Thoughts on Ice and Aviation…

by

(Ed. note: I was going to tell you some fascinating tales of my adventures in Kenya over the past few weeks, but that will have to wait…)

Airplane crashes are almost always the result of a series of unrelated factors, decisions and failures that conspire to make a tragedy. Remove – or change the order of – any one link in the chain – and the accident doesn’t happen.

Keep this in mind as you watch the often inaccurate, nonsensical, irrelevant coverage of the crash of Continental 3407.

The NTSB “Go Team” that is heading to Buffalo will be comprised of experts in all facets of aviation – and they are hardwired to make sure they do not put blinders on as they sift through this smoldering hole in the ground.

They are seasoned professionals with the collective goal of releasing a thorough and comprehensive report – with the hope that it will make air travel safer in the future. It often takes months or even years for them declare the “probable cause” of an accident.

But of course we all want to know what happened now. And there are some telling clues and facts that you should keep in mind as you follow this investigation:

1)    This happened suddenly. The flight crew did not issue a “May Day” – or report to controllers that they had any sort of problem (ala Sully’s Hudson River splash-landing).
2)    The Bombardier (nee de Havilland Canada) Dash 8 series aircraft have a sterling safety record.  My query to the NTSB database does not return a single accident report. In the fall of 2007, all Dash 8 Q400’s with more than 10,000 landings were grounded for inspection after the landing gear collapsed on two Q400’s in the same week. But that is about it.
3)    The weather conditions were absolutely perfect for the formation and buildup of ice on the surfaces of the aircraft.
4)    It was dark – making it harder to detect ice buildup.
5)    Turboprop airplanes are more vulnerable to the threat of ice.
6)    The accident happened near the “final approach fix” – the place where the flight crew would reduce power, and slow the airplane down for its descent down the “glide slope” to the threshold of the runway.

airmets_icTake a look at this icing conditions warning chart issued by the NOAA Aviation Weather Center that was applicable for the time of the crash (10:10 PM EST). At that time, the forecasters showed the right combination of temperature and precipitation to cause icing existed in Buffalo from the surface through 18,000 feet.

Also take a look at these numbers below:

METAR text: KBUF 130354Z 24011KT 3SM -SN BR SCT011 OVC021 01/M01 A2981 RMK AO2 SLP103 P0002 T00061006

This is the weather report  (or “METAR” in aviation parlance) for BUF at the time of the crash. I have pasted in the actual report for you pilots out there – the basic translation is the wind was blowing from the southwest at 11 knots; visibility was 3 miles with snow and mist. There were scattered clouds at 1100 feet, a solid overcast deck at 2100 feet. The temperature was +01C (about 33 degrees Fahrenheit) – and the dew point was -01C.

Snow, mist and a 2-degree separation between the temperature and the dew point around the freezing mark are sure signs that there is ice in the air, if you will. As you fly higher, the temperature drops. Pilots learn about something called the “adiabatic lapse rate”. While it varies with temperature and pressure, when the air is saturated with moisture, it should get 2.7 °F colder for every thousand feet of altitude gained.

The Instrument Landing System approach to Runway 23 at BUF requires the aircraft to maintain 2300 feet of altitude above sea level (1600 feet above the ground) before beginning the decent down the “glide slope”. ils23-kbuf

Using the lapse rate as a rule of thumb, the temperature at that altitude would be about 4 degrees colder – or 29 degrees Fahrenheit. It is highly likely this airplane was picking up a load of ice

Now icing is a huge problem if you fly a little airplane like mine. Matter of fact, the FAA prohibits my airplane from flying into that blue box – where there are “known icing conditions” because it is not equipped with the necessary de-icing equipment. No sane pilot would thumb his or her nose at this regulation – as ice can bring an airplane down with frightening efficiency: it reduces engine performance, adds weight and changes the shape – reducing the lift – of aerodynamic surfaces.

But this airplane was certified to fly in icing conditions – and had all the necessary equipment. It should not have been a problem. Was the de-icing equipment not working properly? Did the crew use it properly?

The Dash 8 manual says when the plane is operating in icing conditions, engine intake by-pass doors must be open, engine ignition switches must be set at manual, and airframe de-ice must be set to slow or fast. The first two rules are designed to insure the turbine engines maintain required power and the latter is the system that keeps ice from building up on the leading edges of the aerodynamic surfaces.

bootsThey are called “boots” – and they consist of a rubber membrane covering the leading edge of the aero surfaces. When in use, the boots inflate repeatedly with air to break off ice at it forms. There is a myth among many pilots that is it wiser to wait for ice to build-up a bit before activating the boots. The fear is that constant use of the system will create a gap between the ice and the boots – a so called “ice bridge” – rendering the boots impotent. The experts now say boots should be on the minute a pilot sees the slightest bit of ice on the wings. But it was dark and the crew was focused on flying the approach. Did they check for ice?

This accident hearkens back to the crash of flight American Eagle flight 4184 on Halloween night 1994. It was an ATR-72 – also a twin-engine turboprop. The flight was en route from Indianapolis to O’Hare when bad weather forced controllers to put the aircraft into holding pattern at 8,000 feet – where it flew through so called supercooled water droplets – liquid precipitation that is actually colder than the freezing point of water. I am not going to give you the full explanation here (it is a little complex) – check out this wiki link if you are curious.

The key point is this: a supercooled drop of water freezes instantly on contact with surfaces such as electrical power lines, trees, and roads – creating what we call an ice storm. Those same supercooled drops can cover an airplane in ice almost instantly.

As the ice built up on American Eagle 4184, it rolled – and then dove into the ground in Roselawn, Indiana – killing the 64 passengers and 4 crewmembers aboard. The full NTSB report can be found here.

The crew of 4184 did have the boots turned on – but the conditions were “outside the envelope” – meaning the equipment was no match for Mother Nature on that night.

One of the lessons of that crash however is something many pilots like me keep in mind. The crew of 4184 was using the autopilot before they lost control. Since their hands were not on the controls, they could not easily detect that the ice–laden plane was requiring a severe correction in order to maintain altitude. Finally, the control surfaces “ran out of authority” – the autopilot disconnected – and the plane rolled into an uncontrolled fatal dive. It was too late for the crew to right the craft.roselawn

Whenever I see the slightest bit of ice on my wings, I disconnect the autopilot – so I can “feel” what is happening to the airplane  (while asking the controller for a lower altitude immediately).

You have to wonder if Continental 3407 was flying on autopilot – carrying enough ice on its wings that its normal approach speed was simply too slow for it to stay in the air. So when it slowed down, it simply dropped out of the sky. You have to wonder…

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126 Responses to “Thoughts on Ice and Aviation…”

  1. Andres Says:

    Such a great post. I only heard about this news a couple hours ago, didn’t really follow it much more than the headline. Really glad i saw your twitter about this, really helps put a bunch of information together in a linear way.

  2. Nick Ragone Says:

    Amazing, amazing analyis Miles. Great job.

  3. parrotzmom Says:

    Beautiful analysis, and probably correct too!

  4. Matt Sokoloff Says:

    This is very helpful and something every reporter talking about the crash on TV should read.

  5. Mike Hollatz Says:

    Wow! Much more information than I am getting about this anywhere else.

  6. Margaret Anne Says:

    Miles thank you for the information. This is so great everyone else just skims the surface.

  7. Chris Fenger Says:

    A great write-up Miles….and very insightful with such limited official information. As a native of Buffalo, and a pilot I have shot the ILS to runway 23 several times….the area around the FAF (Final Approach Fix) is densely populated. It is amazing there was not more damage or fatalities on the ground.

    Keep up the great work going deeper and more accurately than the general media.

  8. vogel.da Says:

    As always, a concise, factual account, that unfortunately, 99% of the cable/print/broadcast media will miss entirely.

    Thanks for the analysis.

  9. JD Stein Says:

    Thanks for the detailed analysis. I was prompted to search for you online because your on-air explanations of air tragedies have always been complete and delivered with such a high degree of professionalism. So I missed seeing you on TV.

    I suspect you don’t spend a lot of time analyzing CNN’s air tragedy coverage, but I’m pretty sure you never wore white suspenders, a white tie and a black striped shirt to work, unlike the the pilot expert they had on this morning.

  10. Lori Says:

    I have to echo Mr. Stein’s comments. It was this morning’s CNN coverage that caused me to seek out your blog: I figured you had to have landed somewhere. Glad to see there’s intelligent, informed, educated commentary on this sad event somewhere. It’s rather sad, though, that I’ve had to come to a private blog to obtain it. Keep up the great work.

  11. Jon Says:

    I have to agree with much of what Miles has written regarding this crash. I would like to add a thought about the Props of this plane.
    The props of this, and all turboprop planes are highly complex mechanisms. The angle at which the blade of the prop hits the air can be
    changed in order to maintain the best efficency for the given flight condition. The prop angle is usually changed in preparation for landing.
    THERE is an ear witness report of an unusual engine sound, described as that of a chain saw. This leads me to think that the prop or props ran away and went to a very high speed and flat pitch. This might, I REPEAT MIGHT, cause certain problems which could cause the plane to lose control. It might lead to an aerodynamic stall. There are other prop malfunctions which could also cause this unusual sound.

    These props are known as constant speed props, with a governor and other mechanisms to prevent a prop runaway, but, this unusual sound reported does make me wonder. AGAIN, we will have to wait for the NTSB to make sure.

    In my long career as a pilot, I have flown both turboprops and jets. Turboprops are more demanding in my mind than jets due to the unique
    demands of the prop.

    As I’ve always told Miles, follow the money.

  12. Sarah W. Says:

    This is a fantastic analysis. Thank you, Miles. I was horrified to hear of this crash especially considering the 1994 crash you mentioned here. I was living in Indiana at the time, and that crash left me with a crippling fear of the turboprop planes that made up the majority of the plans leaving the regional airport.

    One of the things to come of that crash, though, was that it was clear the state was making a concerted effort to minimize turboprop flights — for years and years, the only flights home I had were regional jets. Recently, though, I’ve noticed that there are more and more prop flights. Chicago, Buffalo, my native South Bend — these are all airports very near the Great Lakes, and subject to the various weather peculiarities that come with that. I’ve always thought it was beyond reckless to continue flying these planes to these cities, and now we are presented with more tragic evidence.

  13. Jon Says:

    The captain appears to have been with the airline for about 3 or 4 years…less so for the copilot/first officer.

    Even one year flying in the Northeastern part of the USA would give any pilot great respect for icing problems. FWIW I get the gut feeling that it was a mechanical issue. The plane was running late and I do have to ask about crew fatigue.

    Captain Marvin Renslow joined Colgan on September 9, 2005. Captain Renslow had flown 3,379 hours with Colgan Air.
    First Officer Rebecca Shaw joined Colgan on January 16, 2008. Ms. Shaw had flown 2,244 hours with Colgan Air.
    Flight Attendant Matilda Quintero joined Colgan on May 28, 2008.
    Flight Attendant Donna Prisco joined Colgan on May 28, 2008.
    Captain Joseph Zuffoletto, an off-duty crew member aboard flight 3407, joined Colgan on September 19, 2005.

    I call upon the Obama administration to get a good strong leader for the FAA. The names involved with the suggested new heads of the FAA do not impress me.

    It seems to me that if the flight recorders survived, we should know what happened within 48 hours.

  14. Jon Says:

    many people on tv are pronouncing the manufacterer’s name the way one would pronounce the person who aims the bomb of a military bombing plane.

    to my knoo

  15. Jon Says:

    correction to above…it should be pronounced “bomb’ bah dee a” (long a)

  16. Jon Says:

    IF the autopilot was disconnected, and the pilots were not ready for an odd control force or an out of trim situation that the autopilot had been masking…the loss of control could have been very fast.

  17. Markus Says:

    I agree the news coverage, especially immediately after the story broke, was somewhat horrible. I’ve sadly kinda grown to expect that, since it’s pretty much the usual fare these days, but it’s still bothering me, because I know it doesn’t have to be like that. What’s bugging me even more though is when that local/national news coverage reaches this side of the Atlantic to be used by our news programs here and additionally suffers from bad and clueless translation. (I translate topics like this for a living, so I can tell.) And that happens rather routinely.

  18. Dave Higdon Says:

    As a former daily newspaper reporter with a few aviation accident stories in my clips file, the depth and detail of Miles’ analysis is excellent — not to mention impressively speedy.

    And his logic works fairly well; morning reports cite ATC traffic with other pilots complaining about the icing and in such conditions icing will always be a prime suspect…but…

    We don’t have indications that the Dash 8 spent the kind of inordinate time in icing that afflicted the ATR-72 in the Indiana crash; we have an airplane with an excellent record in handling normal icing — and normal icing is the way the METAR and NOAA info translate to me in my flying experience…

    With so many other potential issues — from the prop governor failure hinted at by another pilot, to the possibility of a flight management system failure or improper programming, to a simple case of the airplane getting below glideslope late in the approach, there’s still tons we don’t know and can’t confirm…and if it was ice, did the ice alter the airfoil shape beyond its ability to perform or did the airfoils still produce lift acceptably but insufficient to offset the weight of any ice accrued; both would increase stall speed, but for very different reasons…

    …which is why this one will take a while to sort out for the NTSB and all the parties to the investigation, those parties being Bombardier, which built the airplane, Pratt & Whitney Canada, which built the engines, the airline, plus reps for the pilot and maintenance organizations at Colgan down at Manassas, Va…

    Still good puzzle work by Miles; but an accident inquiry still a long way from a probable cause.

  19. M. Mikolay Says:

    Fantastic post that includes some great insights as well as explains the subject matter with excellent visuals such as the icing chart and approach plate. I’m sure you’ve already heard snippets of the audio from BUF approach which really add another element of realism to this sad event. I share Jon’s thoughts above that if they had a load of ice and were on autopilot, the simple act of disconnecting as they started marching down the glide slope could have brought on a sudden loose of control.

  20. Adam Attarian Says:

    Thanks for the great analysis and speculation on this crash. It is great to see a level headed approach that is grounded in science and in reason.

    Great blog work.

  21. Tracy Kornfeld Says:

    As always, we all turn to you, Miles, for accurate reporting on anything to do with man made articles that leave the earth for any distance. I’ve been listening to various reports all morning and they are SO off of the mark that it’s sickening

  22. Mark Pooley Says:

    Hi Miles,

    I was a big fan of your work on CNN and in wathcing the video on the CNN site I thought to myself; I want to know what Miles O’Brien has to say about this. A quick search of your name on wikipedia led to me to your blog and of course I got exactly what I wanted, the straight goods in terms I understand, so I just wanted to say thank you.

  23. Stuart MacDonald Says:

    Miles, what a thoughtful and complete post. This incident is truly a tragedy, the Dash 8 / Q400 machine is incredibly reliable and a true workhorse of regional aviation and the conditions do seem right for buildup.

    My thoughts go to the families and friends of all concerned.

    – Stuart

  24. TomF Says:

    Very solid analysis, Miles, and much more informed and coherent than anything I saw on the broadcast media overnight — even from Bob Hager, who still is NBC’s go-to guy for aviation expertise even though he’s officially retired to a remote corner of New England.

    I suppose it is difficult to put analysis across on TV when chaotic and emotional images are propelling the coverage, but that doesn’t really excuse the stream of misinformation, logic leaps and knowledge gaps that invariably come up in broadcast coverage of tragedies like this. Even casual students of airlines and aircraft were undoubtedly stupefied by the errors and bizarre pronouncements from the cablers last night. As was the case with US1549 last month, there was much clearer, more accurate reporting to be found at airline / aviation community sites on the Internet, fed solely by amateurs and enthusiasts. While CNN was expressing skepticism that the ATC tape existed, a bunch of us on Flyertalk.com were already listening to it, and one guy actually made and posted a transcript.

    Perhaps you can comment on this as a TV anchor, but my suspicion is that a lot of TV talent secretly roots to be at the epicenter of breaking-news coverage of a big plane crash, because it’s a perfect storm of TV drama, raw emotion, big audiences, and scriptless adrenalin. The pity is that most obviously don’t study for that day in advance, though, because when they get that moment, their performance is frequently cringeworthy.

  25. Eric Coronado Says:

    Miles, this is probably the best post-accident analysis I’ve read. If I may contribute my own $.02

    1) Airline policy typically requires the airplane to be full configured (gear and flaps down) prior to the final approach fix so that the speed, power, descent rate, and configuration of the aircraft need not change for the last 2-3 minutes of flight. The location of the accident is just short of the FAF, about at the location the crew would have been selecting the final flap position. Fully deployed flaps cause the most critical situation with tailplane icing as they increase the angle of downwash from the wings, which increases the angle of attack of the tailplane, possibly past the critical angle of attack and into a stall.

    2) I think the speculation of whether the pilots were “looking” for ice buildup is probably misleading. Most airlines have a standard policy of turning on anti-icing equipment when in icing conditions or when the ice detector detects ice. Both conditions were certainly met that night. Today’s airplanes handle ice so well that pilots have absolute confidence in them. It is pretty easy to turn the anti-ice system on and then forget it unless you start seeing accumulation on the windshield wipers.

  26. Jon Says:

    in 1995 an atlantic southeast airlines emb 120 had a prop blade come off, causing the engine to change its angle in the mounting causing terrible drag and it brought the plane down. 9 killed.

    losing aprop blad at low altitude may be beyond recovery.

  27. Greg Gurevich Says:

    Great Report!

  28. Bill Says:

    Miles – nice post. Saw this on another site and thought you might be interested – NASA course on icing.

    http://aircrafticing.grc.nasa.gov/courses.html

  29. David Shugarts Says:

    Very insightful, but I can add a few other thoughts that might be germane or even crucial. Years ago we at Aviation Consumer Magazine did articles investigating the Beech line of aircraft and their certification in known icing conditions. I also was the editor for many years of Aviation Safety Magazine and did many stories on icing accidents.

    No aircraft is ice-proof to the extent that it will never fly into conditions beyond the capability of its deicing equipment. In other words, there could come a condition that is too severe for any deicing system. (Hate to say it, but the same is true for turbulence versus structural integrity.)

    While a lot of effort was devoted to wing and prop deice systems, I do not feel enough was devoted to tail deice. This is a bit insidious because, as you say, the autopilot can mask the effects until you either disengage the autopilot or it runs out of flight control authority, abruptly.

    This aircraft was coming right down the final approach course, which I would attribute to the use of the autopilot. It may have departed from controlled flight at just the time the crew disengaged autopilot, reduced power, added flaps, dropped the gear, etc., which would call upon the control surfaces to compensate for a change in pitch factors.

    Your own consultant, John Wiley, also pointed out that recently the FAA changed policy and, instead of traditionally calling for crews to wait for a small amount of ice to accrete before activating the boots, now calls for them to be activated upon entering icing conditions. I wonder if the CVR will reveal a crew discussion about this very subject.

  30. Mike Says:

    With a prop failure the aircraft would still retained glide capabilities. The FO’s last radio transmission was just outside of the FAF and the aircraft crashed just inside of it. I would think a prop failure or overspeed would have gotten them a lot closer to the airport, a flatter descent angle to the ground, and more houses would have been damaged than the one. Some sort of flight control stall seems more conclusive with the information that is available. Just a thought.

  31. Jon Says:

    there is a post on a different forum indicating that this plane was obsserved doing an engine run at newark prior to the flight.

    ONe must ask if the prop governor mechanism was being checked.

  32. Jon Says:

    there is a post on a different forum indicating that this plane was obsserved doing an engine run at newark prior to the flight.

    what was being checked?

  33. Peter Cooper Says:

    The NTSB issued an advisory on the use of the boots on immediate sight of ice very recently: http://www.propilotmag.com/archives/2008/Dec08/A2_Icing_p1.html

  34. Anonymous Says:

    Outstanding post, Miles. Keep up the good work.

  35. Roland S. Martin Says:

    GREAT post, Miles. Hope all is well with you.

    Roland S. Martin
    CNN Analyst

  36. Roger Resnicoff Says:

    Great post…

    Fantastically detailed, but very clear and precise as to the conditions and what they can potentially do to planes.

  37. Geoff Fox Says:

    Just a quick clarification. Most people think of 32f/0c as the ‘freezing point’ of water. It is actually the melting point of ice. The two are quite different.

    Water can remain in a liquid state in much colder conditions when it has no nucleating agent–something to form an ice crystal around such as a speck of dust. When this supercooled water hits the wing’s leading edge the ice forms nearly instantaneously.

    This ice that forms by accretion is called rime ice. It is not the smooth, transparent ice we’re all used to seeing. http://media.airspacemag.com/images/deicing-388-mar04.jpg is a reasonable example. Obviously, it immediately creates turbulence and changes the shape and lift characteristics of a wing.

    I am a meteorologist. Supercooled water and riming were important enough subjects to receive detailed attention in my meteorology classes.

  38. Leugim Says:

    Why has the FAA waited 15 years to issue the new de-icing adisories? Typical government ineptness.

  39. Peter Cooper Says:

    The ice rationale for the crash has been reported: http://news.bbc.co.uk/1/hi/world/americas/7889764.stm

  40. Jon Says:

    I withdraw my theory on prop problems. NOW , after the NTSB briefing, it seems that all hell broke loose when flaps were selected to 15 degrees. THIS may indicated that the tailplane had too much ice on it and was unable to control the pitch change associated with flap extension.

    the tailplane is the small wing at the back of the plane, also called a horizontal stabilizer.

  41. Jon Says:

    NOW , after the NTSB briefing, it seems that all hell broke loose when flaps were selected to 15 degrees. THIS may indicated that the tailplane had too much ice on it and was unable to control the pitch change associated with flap extension.

    the tailplane is the small wing at the back of the plane, also called a horizontal stabilizer.

  42. wbwill Says:

    Great work on a horrible accident, why is it that such a complete and understandable investigation by one person is not mentioned or heard of unless anyone interested digs into this.

    Makes perfect sense and a wonderful job. So regardless of blame, the pilots did or did not see ice, the auto pilot, so on, did they have the weather data ahead of time to know to take the auto pilot off way earlier?

    Another concern I have from being around the upkeep and repair of not only weather balloons but also Nexrad Radar, is that the old weather balloon system was partially replaced but is running in parallel with the new, in some spots, why is a question I have,, is the new system not trusted or functioning? Next is the age of many Nexrad units, they are at the age where the main mechanical components are in need of rebuilding, and is it getting done?

    Is the combination of dual weather balloon systems, using the older system at some sites, to confirm the accuracy of the new system?

    And the age of the Nexrad units, has the age of these units, needing renewal, of concern?

    Or is anyone aware of the current condition of both weather balloon systems and Nexrad Radar known by the Aviation community?

    Being involved with these needed upgrades, and not seeing any come for upgrade, is both an issue with the business I am in, and the whole situation of lack of funds or whatever, is slowing the revamping of the Nexrad system, worth taking any chance on?

    I am more curious as to the information known by the Avaition community known?

    We need this kind of intelligent diagnoisis, be it right or wrong, as the article is well written and understandable by a layman, something we don’t get as citizens of the US.

    Watching the news on this last spending bill confirms the public has no idea what goes on behind the scene.

    We need more information, although a theory, but a very well put together theory and very believable theory, like this one.

    I bring up what I see going on with weather reporting, as small a portion I have knowledge of, for anyone interested to at least take a look into.

    It appears from the charts there was data, but how accurate is the data? Who confirms it?

    If the Avaition community needs more or better or updated information, there could be no higher priority, I did not say the highest, as National Security is one of the highest also, but to keep our Aviation Industry up to date with whatever they need, I see as important as the most urgent National Security issues, and did the new spending bill do anything to improve the safety of air travel?

  43. Tyler Says:

    Miles,

    As coincidence would have it, I have been learning about aerodynamics because I have been writing about the role of aviation in fighting wildland fires. Wanting to hear some intelligent analysis, I looked for you on the internet and found your blog.

    I have been reading about stalls and discussing same with someone who knows. So, I had an uneasy feeling when I first heard about ice.

    Thanks so much for your intelligent commentary. Keep it up. I have bookmarked your blog and will check back later.

  44. rlasater Says:

    Thank you for your excellent analysis. No doubt vastly superior to the “media” version and much appreciated.

  45. Rick Says:

    Great theory Miles…just doesn’t fit with what most witnesses heard immediately prior to the impact explosion: sputtering of the engines, then absolute silence.

  46. Tim Finucane Says:

    Thank’s for this explanation. Very informative for us non-pilots.

  47. eliza Says:

    Great post. I thought about you last night while watching some of that “often inaccurate, nonsensical, irrelevant coverage,” and was hoping you’d give your analysis. I learned more reading this than I did watching two hours of cable news. Thank you.

  48. corrinstrong Says:

    Whether or not a switch off the auto-pilot caused this accident, the fact that it is a known problem without a remedy is troubling. Couldn’t some kind of program be set up to warn pilots that the auto-pilot is over correcting?

    I live in WNY and have flown into Buffalo many times on both jets and props (often in really horrible conditions). I always felt safer in a prop, but not after this!

  49. Bob Merc-The Shift Says:

    Miles,
    This crash really hits home with me…during the summer my wife was on one of these planes twice …to and from AVP to Cleveland and back from Cleveland to AVP…on a trip to Las Vegas. I do not fly anymore since I got out of the Air Force in 1980. I flew in an Ozark Airlines twin-prop (probably long out of service) from Texas to Chicago and the flight was to say the least harrowing…but we made it. Severe turbulence was the problem on that flight. After I finally made it home to Pa. I promised myself I would never die in a plane crash…if it’s good enough for John Madden of NFL fame to live that way it is good enough for me. This definitely sounds like you’ve hit a home-run with the icing theory. I’m sure that aircraft took on an inordinate amount of weight in a very short time frame and when auto was disengaged they immediately lost control of the aircraft…it probably took them by complete surprise…it actually makes me wonder if they had the de-icing equipment on at all. Suberb article and a terrific read!

  50. Jon Says:

    A tailplane stall occurs when the horizontal stabilizer accumulates enough ice to sufficiently interfere with the airfoil’s
    aerodynamic properties to the point that it l exceeds its critical
    angle of attack.

    The tailplane’s lift is directed opposite that of the
    wing… which means that when it stalls, it rises.

    when the tailplane
    rises, the nose drops. Recovering from a tailplane stall involves a technique
    that is exactly opposite what most pilots have learned: pitch up, reduce
    power, and retract the flaps if they’re extended.

  51. realitymyspace Says:

    Great job explaining this, very interesting to read. May all those who died RIP.

  52. sid Says:

    I was appalled at the misnformation on CNN concerning the evaluation of inflight icing conditions this morning. In particular, was the use of vendor enhanced radar imagery which depicts various stages freeing precip and the idea that such tools can be used to infer inflight icing conditions.

    This is a badly misplaced idea that could get somebody kiled.

    First…Such “winter storm” products are enhanced with colors depicting frozen or mixed precip using manual techniques that generally use observed surface conditions.
    No rigorous effort has ever been made to assess the accuracy of these products, and in any case, THEY DO NOT -CANNOT- DEPICT POTENTIAL ICING CONDITIONS ABOVE THE SURFACE!!!!!

    Next is this little known fact… researchers commonly look for the ABSENCE of echo in WSR-88D imagery.

    Essentially the vast preponderance of droplet sizes (better than 95 percent) which produce rime conditions are too small to paint while the radar is in precip mode. Once the droplet size does grow to the point where it paints well, such condtitions may well be beyond the certificated capability of even transport category aircraft.

    I first learned of this during converstations with Ben Bernstein, formerly of NCAR, who helped develop the FAA’s CIP/FIP…It is amazing how few in aviation know this.

    Here is one reference which points to the complexity of detecting inflight icing conditions using the WSR-88D:

    http://ams.confex.com/ams/Annual2006/techprogram/paper_105175.htm

  53. sid Says:

    More information on the experimental precursor to the CIP/FIP and discussion of icing conditions which do not paint on radar:

    http://www.rap.ucar.edu/largedrop/integrated/ver3/concept.txt

    Radar-based icing algorithms use information from the national radar mosaic and model data to identify subfreezing locations in and around radar-indicated precipitation as those which are likely to have icing. While icing often exists in these locations, a great deal of icing occurs in locations hundreds of kilometers from identifiable echo in radar mosaics. This is typically because the drops which cause the icing are too small to be seen by the radar, except at very close ranges. The exception to this is freezing rain, which can be readily seen by radars, even at long ranges.

  54. Thinking Fool Says:

    Miles, all I can say (write) is “WOW!” I’m so glad TVNewser linked to your blog. Your analysis is incredibly interesting, and I’m glad I found your site.

  55. David Shugarts Says:

    Jon, it’s true that the tailplane is often loaded so as to oppose the pitch-down moment of the wing and therefore it’s a down-force, but this is not true 100 percent of the time. Certain conditions of weight and balance and aircraft configuration can bring the tail to a neutral or even tail-lifting loading. It’s a small point but it can be germane when passenger seating, fuel changes during flight, etc., are considered in aircraft with a wide c.g. range.

    But it’s also worth contemplating that the ice accretion which would be most apt to stall the tailplane in its down-loaded direction, is the ice accreting underneath the leading edge.

    Finally, most pilots never see the worst possible icing conditions and so there is a strong belief that ice just coats the leading edge conforming basically to the shape of the D-section. This is certainly bad enough to make you concerned about degrading the wing’s airfoil. But there is a horn-shaped cross-section which forms in maximum icing conditions that will give you a fright if you ever see it. There are photos in some books, but it’s kind of forgotten lore.

    NTSB is now pointing a big red arrow at ice, and saying the loss of control came just after a flap change. They also say the crew raised the gear before impact. The crrew had been discussing ice observed on the wings and windshield. Ice on the tail would not have been visible, of course.

  56. Rasta Says:

    Dude, this is the clearest (and most plausible) explanation I’ve heard of what my have downed this aircraft. It’s very said and quite frightening. I’ve never flown on a turboprop and incidents like this make me even more nervous to do so.

    We need you back on tv, Miles!

  57. Bob Yuna Says:

    Good analysis, Miles. Good to see your thoughts here. You’re missed in the world of news, hopefully for not too long.

    When the dust settles, I’d love to hear about Kenya. I spent several months in Uganda but Kenya has its own adventures.

  58. diN0bot Says:

    is it possible to research ice conditions online to assess flying risk? where does the ARMETs image (first image of the post) come from?

  59. Wayne Says:

    When they put 15 degrees of flaps the aircraft pitched up due to ice build up. I gather they didn’t react in time: lower the nose, add power etc and the aircraft stalled. I suspect this was pilot error due to non recovery from unusual attitude. So sorry they forgot to push the nose down and add power! They were almost there. I’ve flown ice before and you must be diligent.

  60. ¿Qué pasa en el mundo aeronáutico estadounidense? - OdioTrabajar.com Says:

    […] resulta que la pasada madrugada, se produce un nuevo accidente (excelente post con las hipótesis más plausibles, en inglés). En este caso un Dash 8 Q400, o turbohélice similar (*), en Búfalo, que se salda con […]

  61. Jon Says:

    wayne, it may be tailplane stall and you have to pull back to get out of that unique situation…see my earlier post…

    Boots and icing only mix when you are wearing the boots on your feet while doing a walkaround inspection looking for ice.

    IT IS NOW TIME TO GET RID OF BOOTS in all planes or severely limit those types to trace or light icing exposure for less than 2 minutes.

    WHILE Icing can bring down any plane, it seems that heated wings/airfoils are the way to go.

    OR make the airfoil so robust aerodynamically as not to need anti-ice.

    I guess there should be a ice detector on the tailplane!!!!!!

  62. Tom Kassab Says:

    Miles,
    This was very well written and very thorough. I’m impressed with the details you have provided here and acknowledge you for your passion in writing this story. Great job my friend! Tom

  63. sid Says:

    I would highly recommend that the FAA’s requirements for Weather training evolve beyond the 1950’s standard where they are stuck now.

    Its time weather interpretation skills move out of the boring afterthough position where they are currently ensconsed.

    The idea that our tax dollars will produce some great kinds of 21st century “Magic- Bullet” products that can bridge the gap between the current state of the science of 21st century Meteorology, and the woefully inadequate weather knowledge required by aviation users, is wishful thinking.

    Know what an MCS is?

    Is there ANY FORMAL requirement to learn how to interpret land based weather radar or satellite imagery? Nope. Nada. Zip.

    Did you know that you can spot ~85 percent or better of atmospheric turbulence in satellite imagery?

    Ever hear of “mosisture channel darkening”?

    What is the single biggest source of injuries in Part 121 operations?

    Ever hear of “CIT”? Overshooting tops?

    Who writes the TAFs? Is it the FAA, or the NWS? Where are these forecasters? At the AWC? Or the CWSU? BTW, what radius around the center of an airport does a TAF cover?

    Ever hear of an “AFD”?

    You’d be amazed at how many …with many thousands of hours under their belts… have no idea.

  64. Muriithi Says:

    Ed. note: I was going to tell you some fascinating tales of my adventures in Kenya over the past few weeks, but that will have to wait…

    I will pester you till you spill the beans.

  65. Jim Says:

    Miles,

    Used to work in ROC and BUF media — weather — you’re spot on! By the way, BUF NEXRAD was originally planned for the town of Clarence! Residents complained, declaring “radiation” from NEXRAD would ultimately harm or kill them. NWS kept radar, of course, on airport ground. Don’t believe a Clarence NEXRAD site would have aided in detection of specific dbz level precipitation, but it does offer some intrigue to the problem-solving.

  66. Sad in NY State Says:

    Miles O’Brien, I appreciate your discussion very much.

    After losing a friend on 3407 last night, it helps me start to understand factors involved and have hope for safety improvements in the future.

    Some questions, please:

    1. Did facts from data recorder reported in the NTSB news conf Friday 6pm confirm or change what you think happened? (For example, the anti-icing being “on” as reported prior to flight crew discussing ice build up on windshield and wings, and the severe roll and pitch starting when flaps were moved?)

    2. If tailplane had too much ice as Jon’s comment says possible, would that be consistent with what data recorder said happened with roll and pitch?

    3. Was there any capability of the plane that the flight crew could have used to reduce ice on the tailplane (similar to what boots do for wings)?

    4. If there’s nothing they could have done to prevent tailplane ice, would a safe landing with tailplane ice depend on the pilot executing perfect or heroic correction actions to sufficiently mitigate harmful effects of tail ice? Was that possibly what didn’t happen? Or just not enough speed?

    5. Considering ice build up noted by flight crew, should the auto pilot have been shut off at some high altitude? If the crew didn’t think to do that, should air traffic controllers have suggested turning off auto pilot? (NTSB didn’t mention auto pilot either way Friday.) Are air traffic controllers allowed to give safety reminders to pilots for things like turing off auto pilot in icy conditions?

    6. Once the flight crew realized ice build up on wings and windshield well before starting landing approach, should they or air traffic controllers have canceled the landing in Buffalo? Fly to some airport away from ice zones on that map you posted? There was still a lot of fuel reportedly. Would it have made sense to fly someplace a few degrees warmer (Cincinnati?) if crew had enough concern about ice build up to have discussed it earlier with air traffic controllers?

    Sorry for so many questions. I’m just trying to understand why this happened to my friend and the others. Thank you for your insights.

  67. driverjowitt Says:

    A fatal accident involved a de Havilland Canada DHC-8-102 ZK-NEY Ansett New Zealand 09-JUN-1995

  68. Rachel in Australia Says:

    I am intrigued by the ATC instruction for 3407 to decrease speed and then later on I heard him give vectors to 330, 310 and then what I heard as 360 (instead of 260 … I have noted 260? in some ATC transcripts that have been posted on the web) as the aircraft was being guided in its turn towards the localiser at 233 inbound to RWY 23. I have read a report from a ground witness saying that the aircraft was flying in a northerly direction during it final dive. I checked Google Earth and dicovered that the FAF is at 4.4 nm from the airport and the crash scene is about 5.2 nm from the airport in almost a direct line to RWY 23. Maybe some pilots can tell me if the 233 direction is locked in about a mile from the FAF or does this mean that the plane was indeed heading north and not in an arc towards the FAF. Does anyone has information on the wind directions and speeds up to say 6000′ in the vicinity of the airport? I am wondering if there was vertical wind shear in addition to the gusts at ground level.

    It is just shocking to hear that young female FO’s final response to ATC. What an awful day for all Americans and especially for the family and friends of those who lost their lives.

  69. John Sampson Says:

    Asymmetric Icing – the Cause and the History
    Quite obviously (IMHO) due to the asymmetric build-up of icing caused by both engine’s props rotating in the same direction (think it through). I’d be amazed if it was due to engine failure.

    They now need to put a scale model in an ice-distributor wind tunnel with the engines being electrically driven i.e. electric motors to drive the props at proportionate (to model-size) speeds) – and see just what the asymmetric ice loading effect becomes over time (in terms of aerodynamic drag differential (L to R), asymmetric lift and weight). By having the flight control loads monitored, they’d be able to determine what the increased stall speeds become and thus the much higher speed at which control is lost (i.e. the inevitable spinning auto-rotation onset speeds-whether on autopilot or not).

    All of this was apparent after Roselawn Indiana and the ensuing icing crashes – but no-one bothered to look into asymmetric wing, tail and fuselage ice-loads induced spanwise by “same direction” prop rotation. Maybe now they will….. but wouldn’t be surprised if they didn’t.

    Like wiring-initiated fires, all icing crashes lose their critical evidence post-crash. The problem with rain-ice or freezing rain (or SLD as it’s called less alarmingly by the fAA/NTSB) is that it “hits and sticks”. It hits (and sticks) more on one side than the other due to prop slipstreaming. That asymmetry is insidious. It’s particularly lethal if the autopilot is left to quietly “soak up” that asymmetric ice-loading. Ultimately the autopilot will run out of compensatory trim-loading and be itself over-powered. That can happen quite quickly even in cruise – as the stall speed rises very rapidly in the latter stages of ice build-up. But the REAL problem is that the stall speed difference between the LH wing and the RH wing can be as much as 25 knots – all due to the spanwise distribution of the ice (both its mass centroid and its aerodynamic drag increment on each wing) being so different, left to right. Once that RH wing stalls, the aircraft will roll rapidly and the instinctive pilot input of opposite aileron (to counter the roll) will only embed the aircraft in the then inescapable condition of autorotation (i.e. spinning).

    You have to wonder how many turbo-props approach that terminal condition each day, across the globe. The few that reach it and fail to recover just become another non-specific “control loss” statistic. It’s less about the Dash-8 and more about the vulnerability of any turbo-prop type that is licenced to operate in icing conditions.

  70. y3 Says:

    so Many questions. thanks

  71. Herb Says:

    You can take the man out of the news network, but you can’t take the expertise out of the man. Keep up the good work, bud.

  72. mikelambert Says:

    CFIT is actually a common cause of plane crashes, as is running out of fuel, not checking for yourself which runway to take off/land on. Not putting landing gear down, flying in conditions for which you are not rated, not having enough hours in IFR conditions. Landing long, not using auto brakes.
    Checking the weather.

  73. Phil Says:

    Outstanding work here Miles- The one item I would ad to this as a high time ATP pilot is that the news last night stated that they had the cockpit voice recorder and that the FO had just selected flaps 15 when the bottom dropped out.
    This change in configuration would change the angle of attack and COULD have made the wing unflyable.
    I have many times landed with no FLAPS TO AVOID THIS POSSIBILITY.
    The aircraft was flying, they changed the flap setting, and then it was not flying.
    I have personal knowledge where this has happened to 3 pilots who have lived to tell the story first hand.
    A point to consider with this new information received after Miles completed his outstanding and well articulated analysis.

  74. noman242 Says:

    great, useful information shows your expertise

  75. mikelambert Says:

    I just read the bad news. Both pilots had little experience. I am sorry but just being confident in your abilities does not trump hours.

  76. Kate Dougherty Says:

    Miles,

    Well done. Thank you for the thought-filled reporting.

    Kate Dougherty

    PS Welcome home!

  77. Pati Mc Says:

    Finally a sensible and learned explanation. Thank you Miles! So glad that your voice is still being heard.

  78. David Shugarts Says:

    I think it’s time we donned parachutes, since we’ve all begun jumping to conclusions.

  79. rbpasker Says:

    observed airframe icing always means a NO FLAP LANDING and a HIGHER AIRSPEED.

  80. Mitch Semel Says:

    As usual, a detailed and thorough explanation for pilots and non-pilots of relevant issues in this terrible accident.

    Hope all is well with you.

  81. brian Says:

    this makes you wonder how cnn and msnbc garner an audience. in my perfect world you would write every associated press article. this is fabulous, great work. thanks.

  82. jobconger Says:

    Super post and excellent reactions in the main. You could be the new Richard Collins or Len Morgan. I have bookmarked your blog and look forward to reading (and learning) here often.

  83. Mike Burris Says:

    @ rbpasker:
    In a Part 121 operation you are never, by choice, going to land a revenue flight with zero flaps or even reduced flaps. If the Wx is that bad you divert.

  84. jurasee Says:

    Great post, fascinating diagrams, maps!

  85. Gerardine Baugh Says:

    With icing conditions in the forecast, does the FAA issue a warning to all planes in the air, and ones taking off?
    Possibly- warning them not to go to turn on auto pilot during unsafe conditions?
    Just wondering..

  86. dcclarkjr Says:

    Interesting that NTSB now says plane landed flat not nose-down. Wouldn’t a flat spin, if that’s what happened, be very tough to recover from?

  87. questions Says:

    Is what rbpasker wrote at 11:45 the conventional wisdom for this aircraft type and the conditions? Why wouldn’t ATC and the procedure manual have instructed the pilot to not put down the flaps? The violent pitch and roll did start a few seconds after the flaps were moved.

    rbpasker: “observed airframe icing always means a NO FLAP LANDING and a HIGHER AIRSPEED.”

  88. questions Says:

    Miles or anyone, what do you think of this point made on the airliners.net forum about the Buffalo crash? How would the pilot know which type of stall? And is it true that a tail stall recovery requires slowing down airspeed?

    “Growly150 From United States, joined Sep 1999, 139 posts, …Reply 37, posted Fri Feb 13 2009 18:37:34
    “Quoting PITrules (Reply 34): ULMFlyer:
    “The problem is that wing and tailplane stalls have opposite recovering procedures. Recovering from a tailplane stalls entails full aft yoke, raising flaps and decreasing airspeed. Tough situation to find yourself in.”

    Unfortunately, these recovery procedures are generally not part of airline training.”

    That seems unforgivable.”

    http://www.airliners.net/aviation-forums/general_aviation/read.main/4316683/

  89. Mike Burris Says:

    @ Questions:
    For your first question about rbpasker’s suggestion and the conventional wisdom of flap usage in icing conditions– standard operating procedure would be to not put them down until absolutely necessary during the approach. However, landing with them up would not have been an option. Rbpasker’s suggestion is what they teach general aviation pilots and does not apply to Colgan’s equipment or operation.
    As for your second question, about tailplane stall recovery procedures and why they are not taught, I don’t really have a good answer for you. My only thought is that a tailplane stall is an exceeingly rare occurance. I’ve never had one happen to me, nor have I heard of it happening to anyone I fly with.

  90. David Shugarts Says:

    I have covered thousands of aircraft accidents and the tail stall belongs to a class of events that you cannot expect to train for with any success because it goes counter to the normal and correct use of controls, and is so rare.

    To take a different situation that is almost totally forgotten these days, thankfully: Once there was a possibility that ailerons could be rigged backwards during certain maintenance and repair procedures (later, careful aircraft designers made it impossible to reverse the cables). If the pilot failed to make the routine (and boring) check that is theoretically made with full pilot attention (hah!) before every takeoff, he or she might leave the ground and discover that a right roll command gets you left roll, and vice versa.

    Unfortunately, many pilots died before understanding the situation. A few superheros survived and made it seem like the rest of us were defective somehow. The first kind showed up as fatal accidents, the second were cited in Service Difficulty Reports.

    Getting back to the tail stall: The conditions where you would encounter it are so rare and so unexpected that it would be extremely unproductive to try to train for it.

    Worse still, this situation when it involves ice usually occurs at a relatively low altitude upon some change such as a power reduction, flap change, etc. that comes on final approach. The aircraft may be fully stalled, rolling over and diving, or spinning, with controls that do not respond conventionally, with seconds before ground impact. It is superhuman to expect the crew to figure all this out in time.

  91. questions Says:

    Mike B. and Dave S., Thank you for those explanations.

    To follow up Dave’s last paragraph, what does anyone thing about the following?

    Might a better strategy be to require some icing detection device on the tailplane (horizontal stabilizer) to enable pilots to know if and when significant icing happens back there?

    Unlike for wings, visual inspection isn’t possible for the tail. Even for wings, maybe some automated detection would be a good improvement especially for flights after dark.

    Does anyone know, do any turboprop planes have that kind of thing on the wings and or tailplane to detect ice and inform the pilot?

    In general, if a pilot knew before being too close to the ground that there was dangerous ice on the tailplane (or on the wings) then the safe thing to do would be to not land until enough de-icing from the boots happened – correct? Or to fly somewhere else? Wouldn’t there have to be some better alternative than to go ahead and try landing – if they knew?

  92. Thomas Richard Says:

    Early CNN coverage had a reporter pressing witnesses to say if the plane sounded like ‘those World War 2 planes’ when diving. Virtually all WW2 film was shot without sound which was added later, often very creatively. And, of course, they were hunky prop planes, not turbo props. Oh my.

  93. Jon Says:

    As more information comes out, the plane may have had a conventional aerodynamic stall and not a tailplane stall. As we hear more and more
    the plane came in flat to the ground and not nose down as previously reported. Could errors in airspeed indication have fooled the pilots
    into getting too slow? Did they advance the throttles to compensate for the drag of lowering flaps and landing gear? Was the autothrottle system
    installed and working to maintain speed? Did the deice boots fail to keep up with the ice? Are we becoming too dependent upon autopilots and other automatic systems to fly planes? I hate autopilots and always flew my jets from takeoff to cruise levels by hand. So too in the descent.

    Are modern airline pilots just interested observers to automation?

    jon

  94. Jon Says:

    Miles knows my pet peeve of autopilots and automation over use in today’s aviation world. Imagine your life of never climbing stairs
    never walking, never thinking for yourself…and suddenly you have to run from an escaped tiger? Imagine the modern pilot who is instructed by his airline to use the autopilot all the time and suddenly facing an aerodynamic nightmare?

    How did we get here? Back in the golden age of flying, the cockpit of a transatlantic airliner was a crowded place. Captain, Copilot, Relief Pilot
    (for the other pilots to take a nap)a radio operator (sometimes even using a telegraph key) and a navigator using a sextent…later Loran or other difficult to operate primitive navigation systems. And not to forget the flight engineer who monitored the engines and other systems that made things work

    Sure there was an autopilot. Those have been around since Sperry and Jimmy Doolittle became friends in the 1920’s.
    But those old autopilots could hold altitude and heading and were not really used for landing.

    But all those guys in the cockpit COST MONEY! They were worth every penny, but why not get rid of them with machines?. Management, always thinking of money!

    So, radios got better and the guy with the telegraph key was gone. Then the navigator was replaced by more modern
    methods of navigation. The flight engineer was replaced by automatic throttle systems and now the PILOT and COPILOT were doing everything. The relief pilot was gone sometimes as the new jets could make it across the atlantic to some destinations in shorter time and the two pilots had to stay awake the whole way across.

    The newer autotpilots could handle things from about 100 feet after takeoff all the way to touchdown and roll out on the runway. The skilled pilot was NOW DISCOURAGED from keeping his hand flying skills up to muster. AUTOPILOTS are more fuel efficient…they do a better job than you do was the mantra of the corporate executives whose bottom line was the bottom line.

    In 1992 I spoke to the aeronautic professor at MIT occupyping the Boeing Chair there. He said that pilots with 250 hours could easily command the new generations of automate planes. I argued with him…WHAT HAPPENS WHEN THE GADGET DOESN’T WORK? WHAT HAPPENS WHEN the GADGETS are faced with something that they are not programmed for? Nothing can go wrong, go wrong, go wrong…SHADES OF THE HAL 9000.

    So, we have a new generation of pilots. Masters of the magic, but having lost the capability of keeping it all together in their head, and losing that sense of the seat of the pants.

    I still don’t know what went wrong near Buffalo. But I know that IF I RAN THINGS, the autopilot would be used less and less and the mind and hands of the pilot would be used more and more.

  95. David Shugarts Says:

    If we think historically, too, it was flights like Albany and Buffalo that made the stuff of legends, as per “Fate is the Hunter,” by Ernest K. Gann (also “The High and the Mighty”). I would have to re-read Gann, but I remember that he certainly considered the thunderstorms of upstate New York to be legendary, and maybe the ice.

    BTW, those who brought up prop downwash, should remember this was a T-tail aircraft, so the tailplane is flying in free air. On the other thought, asymmetrical wing icing due to lack of counter-rotating props, it’s intriguing and I am not ready to dispute the theory, but has anyone ever see it happen in the real world?

  96. Icing expert and CFI Says:

    Miles – better than most reports, but you say, “Keep this in mind as you watch the often inaccurate, nonsensical, irrelevant coverage of the crash of Continental 3407.”

    You have some technical errors in your discussion that I’d like to correct.

    “Take a look at this icing conditions warning chart issued by the NOAA Aviation Weather Center that was applicable for the time of the crash (10:10 PM EST). At that time, the forecasters showed the right combination of temperature and precipitation to cause icing existed in Buffalo from the surface through 18,000 feet.”

    Well, it is true that there were advisories for moderate icing along the route of flight. This wasn’t an advisory for severe icing. Moderate icing is very common for air crews to like this to fly in. Next, it doesn’t show the “right combination of temperature and precipitation” since icing doesn’t have to involve precipitation – just supercooled liquid water. The aircraft’s route took them right on the edge of two AIRMETs with the southwesterly AIRMET being 3,000 to 8,000 feet.

    “Snow, mist and a 2-degree separation between the temperature and the dew point around the freezing mark are sure signs that there is ice in the air, if you will. As you fly higher, the temperature drops. Pilots learn about something called the “adiabatic lapse rate”. While it varies with temperature and pressure, when the air is saturated with moisture, it should get 2.7 °F colder for every thousand feet of altitude gained.”

    Given a temperature of 1°C at the surface, it doesn’t mean that there’s icing in the air. I’ve departed dozens of times into the clouds in this situation only to find that the temperature at 8,000 feet is +12°C or warmer. That’s called a temperature inversion. Happens quite frequently.

    Also pilots know nothing about the adiabatic lapse rate unless they’ve done training with me. There is a “dry” adibatic lapse rate and a “moist” adibatic lapse rate. Which one are you talking about? The dry adibatic lapse rate is about 3°C (not F) for every 1,000 feet. That’s for unsaturated air that is lifted and has nothing to do with the environmental temperature. It doesn’t vary with temperature – the rate is constant.

    The moist adibatic lapse rate isn’t a constant, but varies with temperature. Once again, this is only the situation where rising saturated air is cooling, not the environment. I have no idea the value of comparing the actual temperatures to these rates unless you are lifting a parcel of air.

    “This accident hearkens back to the crash of flight American Eagle flight 4184 on Halloween night 1994. It was an ATR-72 – also a twin-engine turboprop. The flight was en route from Indianapolis to O’Hare when bad weather forced controllers to put the aircraft into holding pattern at 8,000 feet – where it flew through so called supercooled water droplets – liquid precipitation that is actually colder than the freezing point of water. ”

    Well, the initial altitude of the hold was 10,000 feet, not 8,000 feet. The pilot was cleared down to 8,000 feet, but suffered an uncommanded roll at about 9,100 feet as the pilot retracted flaps. This was basically due to freezing drizzle aloft.

    “Using the lapse rate as a rule of thumb, the temperature at that altitude would be about 4 degrees colder – or 29 degrees Fahrenheit. It is highly likely this airplane was picking up a load of ice.”

    I wouldn’t recommend using any lapse rate as a rule of thumb. In this case, the environment just happened to be close to the numbers you are suggesting (actually 28 degrees F).

    With a ceiling of 2,100 feet above ground level, that would have put the aircraft at about 2,200 MSL which is just in the bases of the clouds based on the 0254 METAR. I doubt they were picking up a load of ice here. Their problem potentially started as the aircraft descended through 11,000 feet into the supercooled liquid water and then leveling off at 2,300 feet. Most icing accidents happen on the approach to land with slower airspeed and higher angles of attack. Add ice to the airfoil where it is not supposed to be and weird things can happen when you change configuration (add flaps, for example).

    “You have to wonder if Continental 3407 was flying on autopilot – carrying enough ice on its wings that its normal approach speed was simply too slow for it to stay in the air. So when it slowed down, it simply dropped out of the sky. ”

    I don’t agree with you here. Likely had an ice ridge building behind the protected surfaces and causing an uncommanded roll when the configuration was changed while the aircraft was on autopilot (yes they were executing an instrument approach). When you are only 2,000 feet or so above the ground, it is hard to recover. This same issue occured in the 1994 Roselawn, IN accident.

  97. Justin Says:

    wow I wish I could write like you….i’ll definately keep coming back to your blog if its all as good as this! great job!

  98. Jim Ogle Says:

    This is why I have SOOOOO much respect for your work. This is one of the best explanations I’ve seen this week! Thank you!

  99. y3 Says:

    ok . I could write like you :D

  100. Ellen OBrien Says:

    Miles…great job, as usual. Wish you were reporting regularly…CnNNs BIG loss…maybe TPTB will wake up and get you back

  101. John Sampson Says:

    Some Prior Research into Asymmetric Icing due to Same Direction Prop Rotation

    Considering prop rotational directions and the resulting asymmetry of lift and drag due to icing buildup under helical prop slipstream influence (an Academic Study with DHC8-400 graphics)

    LINK:

    http://www.iasa-intl.com/folders/belfast/Continental_Flt3407.htm

    …(to an explanation for asymmetric icing and the possibility of asymmetry-generated autorotation)

  102. Bob Yuna Says:

    Well folks, here is a likely answer.

    http://www.msnbc.msn.com/id/29194109/

  103. Jon Says:

    AUTOPILOT was ON …new report saying the autopilot was engaged as the plane stopped flying.

    I hate autopilots…this is sounding more and more like a stall/spin accident with ice as the kicker

  104. Marty Says:

    Miles,
    Do you know the different types of Deice vs Anti Ice systems on this type of Aircraft and which surfaces are “protected”, both airframe and engine/prop? I believe there is some confusion regarding the difference in these systems and their use along with where icing could occur.

  105. Jon Says:

    This is a nutty crash. How could two pilots let the plane get so slow…UNLESS their flight instruments were not registering the correct air speed. Or if the pilots were hypoxic. lack of oxygen that is. or very fatigued.

  106. Bob Yuna Says:

    Interesting piece in today’s “Buffalo News” about two carriers who’ve stopped using turbo prop aircraft in cold weather climates:

    http://www.buffalonews.com/home/story/579988.html

  107. Jon Says:

    what if the pilot was so primed to be ready for a tailplane/ice/stall that he used that recovery when it was only a conventional stall?

    I recall when I flew DC9’s on this route…it is only economic choice to use a lesser plane like a turboprop.

  108. Fran Hammond Says:

    Isn’t this incident similar to one several years ago when an ATR-72 corkscrewed into a cornfield in Indiana near West Lafayette/Purdue U?

    I seem to recall that the icing was so severe that the boots couldn’t handle it. And that the ATR’s operated by American Airlines were relocated to Dallas and southern routes during seasons of extreme icing.

    It appears that the Dash-8 and ATR-72 are very similar designs.

  109. Mike Burris Says:

    Jon, interesting point about the flat impact angle. You’re right, with a tailplane stall you’d expected to see her go down nose first.

  110. Bob Jacobson Says:

    T-tailed aircraft (horizontal stabilizer mounted at the top of the tail) are subject to a phenomenon called pitch-up. This occurs when the wingtip vortex moves inboard from the wing-tips during a high-speed stall. The vortex presses down on the horizontal stabilizer and forces the nose up rapidly. Recovery is difficult, and roll or yaw inputs may result in the aircraft going into a flat spin. Stick shakers are used to warn of incipient stall, and pushers are an automatic way of rapidly reducing the angle of attack, which is the recommended recovery input in a pitch-up onset situation.

    Pitch-up is a bigger problem in swept wing aircraft than straight wing aircraft like the Dash-8, as swept wings tend to stall first at the wing tips, and straight wings tend to stall first at the wing root. It may be that the icing conditions caused the wings to stall faster outboard than inboard, causing the vortex to move inward and cause the pitch-up.

    The systems designed to warn of and prevent stall depend on sensors that measure airspeed and altitude, angle of attack, and g-loading. These systems are designed for the aircraft’s performance envelope. It may be that the ice loading on the wings and stabilizers changed the performance envelope of the aircraft enough that the safety systems did not kick in soon enough.

    If the plane had been piloted manually at the time, there is no assurance that the pilots would have noticed significant changes in the handling of the aircraft. The stick shaker and pusher systems were developed because the onset of pitch-up can be so rapid that the pilot may not have time to react to feedback from the controls.

    Speculating on pilot error at this point needlessly besmirches the names of the crew, and cause additional pain on their families.

  111. Jon Says:

    I don’t think anyone is speculating on pilot error, but people are wondering why the FAA and the NTSB differ on autopilot useage?

  112. JOEDUPONT Says:

    tHE BEST THEORY IS THAT THERE WAS ICE ON THE HORIZONTAL STABILIZER. WHEN THE FLAPS WERE EXTENDED IT CAUSE TURBULANCE OVER TH E ENTIRE NEGATIVE LIFTING SURFACE AND SHE DOVE INTO THE GROUND.
    THE faa HAD WARNINGS ABOUT AUTO PILOT WHICH MASKED THE SYMPTOMS UNTIL IT WAS TOO LATE.

  113. Dave Price Says:

    Miles: As a pilot, and a colleague who was dispatched to Buffalo to cover 3407 – I appreciate your insight. I can’t agree more about the irresponsibility of rushing to put a final cause on an accident just hours after it’s taken place or repeating annecdotal info as fact, when we can’t confirm it (“the plane nose-dived into the house”). Miss your presence on CNN….but glad to see you have a flourishing presence on the web. I’ve always looked to you for solid aviation reporting, and this week was no exception. Thanks.

  114. Don Ennis Says:

    Miles,
    I’m a former CNN’er, too, who covered Discovery with John Holliman after Challenger. All I can say is your insight is sorely missed. Glad to have found you here thanks to tvnewser.com, great stuff, thank you.

  115. jmanpa Says:

    Miles,

    Excellent and informative post and equally infomative follow ups by others. It makes me appreciate even more the herculean task of those at the NTSB who must write a final report on what happened. To me, those investigators and all of those who repsonded this horrfic event are unsung heroes. Let’s hope that in the end their work results in knowledge that will prevent this kind of tragedy in the future.

    By the way, you are sorely missed on TV. I have always admired your work and found your reporting fair and intelligent. I wish you continuing success.

  116. Wes Oleszewski Says:

    Miles- from someone who has spent a lot of time flying around the Great Lakes area in Part 121 turboprop ops. and seen lots and lots of in-flight ice, I have to say that your piece on inflight icing was the best I’ve ever read! Especially when you busted the long-standing “Ice Bridging” myth.

  117. Greg Says:

    Pretty much everything I have heard about this crash has been echoed by yourself..Its nice to hear it from a pilot though…I also need to add that I was at the Buffalo airport when this crash occured as I was waiting for my son’s flight to arrive which landed only about 15 minutes after the crash happened…I feel terrible for the people that were waiting there for friends and loved ones, and the hardest is knowing I was waiting amongst these people and had no idea that the crash occured until later.

  118. Bob Yuna Says:

    Damn.

    http://online.wsj.com/article/SB123492905826906821.html?mod=djemalertNEWS

  119. David Shugarts Says:

    This triggers old hunches. When something doesn’t make sense, it is usually because there is more information we have not heard or discovered.

    Also, I am completely at attention when I hear something like this:

    “A Bombardier spokesman said Tuesday that the company is ‘not aware of any serious icing incident on this aircraft’ since it was introduced into service in February 2000.”

    The operative phrases are “not aware of” and “serious icing incident.”

  120. John Mooney Says:

    Miles, thanks for a great piece, which shows why you are sorely missed on CNN. That said, it’s interesting that the comments also provide a good deal of food for thought, something that wouldn’t have been available on the tube.

    Happy to have found the site – I’ll be a regular, I’m sure.

  121. John Sampson Says:

    Autopilot level off from a descent in an aircraft without autothrottles is a bit of a trap. Although I don’t know of any similar accidents, there’s beginning to emerge a story of a catalogue of similar frightening incidents on the Q400 where pilots have become preoccupied with resetting (or setting up ) the FMS and not noticing, whilst heads down, the body angle changing rapidly to nose-up (once below about 180kts the Q400 reputedly does this slowdown rather fast, iced up or not). The normal speeds for intermediate level-offs are 200 to 210 knots. It’s believed that Colgan 3407 slowed to as little as 134kts. Some of the anecdotes have both pilots head down trying to resolve an FMS button-punching glitch and/or looking back at the special “wing inspection” lights illuminating the Q400 wingtips – to see if the ice is actually being dislodged.

    Does the Q400 simply level off and start bleeding airspeed without any indications at all? Is setting this trap something that should be happening during high pilot workload on approach?

    Should the autopilot instead be set to a descent rate and the altitude alerter set to clue the flight crew to do the level off manually – instead of the autopilot just capturing the altitude and slowing whilst awaiting the pilots setting of an appropriate thrust? At least then there would be an expected alerting chime or suchlike.

    So did the low time on type Colgan Flt 3407 pilot respond to a sudden stick-shaker [and rapidly following stick-pusher] by raising the nose, cleaning up the gear and flap and attempting a go-round from a dangerously low speed (instead of taking the correct stall recovery action of adding power and lowering the nose?). That possibility exists. Surprise can be quite a mind-numbing wake-up call. It’s called Instant Overload. It results from fatigue or loss of Situational Awareness (SA)

    But why and how would he achieve 31 degrees nose up before the aircraft stalled and started spinning? Did he mean to? The logical answer is “no, of course he didn’t”.

    The simple answer is that that extreme nose-up pitch-up tendency would be the autopilot’s legacy to him after it kicked itself out due to reaching full nose-up auto-trim in pitch (in its attempt to maintain the set capture altitude against the added drag of ice, gear and flap – likely with something near idle power inadvertently LEFT set).

    Once the autopilot kicked out and the panicky pilot added max power, the full noseup trim would be conducive to the aircraft looping the loop of its own accord. The pilot would be flummoxed by this setup and, after a confused pause, fighting hard against powerful nose-up trim forces to lower the nose. Adding max power at low IAS itself produces a powerful nose-up trim change. Add that to the already full nose-up trim state and they didn’t have a chance…… of avoiding a deadly stall/spin outcome.

    I couldn’t imagine a nastier surprise. Fancy building in such a death-trap as an autopilot without autothrottle and an FMS that needs lots of head-down two-pilot trouble-shooting and reprogramming? His available solutions were:

    a. Not to add full power, but just enough to keep it flying and, as per my technique (see below)

    b. Roll sufficiently (about 50 degrees bank) so that the fully back-trimmed airplane only pitched mostly into the turn – giving him a chance to wind the trim nose forward whilst minimizing the speed loss..

    I had a similar situation (but not unexpected) tonight after a night take-off. The EFATO drill for a practice (or real) engine failure after take-off is for the front-seat student to raise the nose, simulate putting the throttle to “stop”, call Mayday on intercom and then he releases the stick after having run the pitch trim to full nose up (for his optimal survival seat-vector), places both hands on his left knee and calls “abandoning now” (simulating an ejection). The rear-seat instructor then takes over, banks into the circuit direction (turns “crosswind” essentially), to help the nose drop from around 25 to 30 degrees nose-up – all whilst running the elevator trim nose-down towards neutral and adding near to max power. It’s a silly drill (it’s like practising dying) but meant to be very realistic for the trainee – and it’s a requirement for him to do it prior to his NF3 night solo sortie. You wouldn’t want it to happen suddenly without warning however. It’d be a quite difficult recovery (particularly at night or in IMC).

    Prima facie, and in light of all the similar anecdotes now emerging about turboprops with this cheap option (i.e.no autothrottles and a heads down FMS keypad), this would have been the scenario surrounding Flt 3407’s fate. For that Colgan pilot it would have all happened very fast. It’s a nasty setup just begging for a tech remedy.

    Automation can be a half-baked bitch. The FAA is still trying to nut out the cause of the A330 pitch incidents (AD 2009-04-07) – which is just as concerning. They don’t understand why it happened on that Airbus – but they’ve come up with an interim fix to deactivate the “faulting ADIRU and stop it happening. Hardly good enough, this long after the incident.

  122. keith wilson Says:

    Thank you to all who commented. As a novice to all the technical stuff, could I ask the question “If the deicing system on the plane was turned on shortly after takeoff, why was there significant ice buildup thereafter?”

  123. d shatin Says:

    http://www.wthr.com/Global/story.asp?S=9879126&nav=menu188_11_10_4

    “Jim Hall, an attorney with Nolan Law Group and former Chairman of the U.S. National Transportation Safety Board added, “The FAA cannot demonstrate the Dash 8-Q400 can be safely operated by Colgan Air within the airplane’s certification requirements. For the safety of the flying public, the Q400 turboprops operated by Colgan Air should be barred from operating in icing conditions. Declaring an operation to be safe, in the absence of conclusive proof, is not sufficient.”

    Noone is looking for a ‘conspiracy’ for goodness sakes, however, there are questions which must be raised and answered, including whether the pilots at Colgan Air were sufficiently trained on the Dash 8-Q400 and whether the pilots were sufficiently trained for its employment in the weather conditions in Buffalo NY that night given this was the first winter Colgan Air had employed this aircraft. More facts to come.

  124. d shatin Says:

    http://www.forbes.com/feeds/afx/2007/10/29/afx4271244.html

    from Forbes: October 29, 2007

    “SAS Permanently removes Bombardier Dash 8 Q400 planes from fleet”

    Excerpt:
    On Saturday, Danish civil aviation grounded all Dash 8 Q400 planes in the SAS fleet after one made an emergency landing at Copenhagen airport. None of the 44 passengers and crew on board were injured.
    According to Danish police cited by Ritzau news agency, the landing gear in the plane’s right wing failed to deploy. It was the latest in a string of incidents involving the aircraft which carries around 70 passengers and is manufactured by Bombardier of Canada.
    On Sept 12, SAS grounded its entire fleet of 8 Q400s after two planes’ landing gears failed in separate incidents.

    Inspections later found that the insides of the landing gear bolts on the entire Dash fleet of SAS were corroded. After that ban was lifted another 8 Q400 had problems with its landing gear whilst in mid-air on October 10 and was forced to return to Copenhagen airport.

    ‘Confidence in the Q400 has diminished considerably and our customers are becoming increasingly doubtful about flying in this type of aircraft,’ SAS chief Mats Jansson said in the statement. SAS had operated 27 of the 8 Q400s, using them on many Nordic regional routes and for connections to close destinations such as Britain, Germany, Luxembourg and Poland.

    tf.TFN-Europe_newsdesk@thomson.com

  125. David Shugarts Says:

    I have looked closely at the Nolan press release and I don’t find anything I can identify as new facts to support their scary statements and rhetorical questions. Could it be that this law firm wants to get noticed so that it can attract clients?

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