Archive for February, 2009

Chasing the Needles…

February 20, 2009

bordinstrument_232x232-rgb_tcm586-46594Pilots learning to fly on instruments are told by their instructors to be careful not to “chase the needles”. It is expression that refers to the gauge that is used to insure an airplane is flying inside an imaginary cone of safety as it descends toward a runway. The pilot’s goal is to keep the cross hairs lined up perfectly (as they are in this image) – meaning the aircraft is centered vertically and horizontally on the path toward a safe landing. Pilots who are new to flying with this gauge as a navigational reference tend to over-correct when the sensitive needles show the plane is in the wrong place. They “chase the needles” – flying S-turns – or porpoising up and down – as they struggle to find the sweet spot in the middle. More often that not, “chasing the needles” leads to a botched/aborted approach.

And so it goes for aviation accident investigations. As you read the daily dispatches about the current state of play in the search for the cause of the crash of Colgan/Continental 3407, I urge you to avoid “chasing the needles”.

Remember, a plane crash is almost always the result of a chain of seemingly unrelated factors.q400_turboprops

So far, it appears investigators have only ruled out one significant thing: the aircraft itself. It seems the Dash-8 Q400 controls, systems and engines were all operating as per design. That leaves the weather, the instrument landing system and the human beings in the cockpit on the list of possible causes or contributors to this crash.

We know the plane had picked up a pretty good coating of ice that night – the crew reported that fact to controllers . Was that, in and of itself, enough to bring the plane down? Highly unlikely. Did it change the way the airplane performed – making it important for the crew to fly a little faster so it would not encounter an aerodynamic stall? Very likely. Would it have been wiser for the crew to disengage the autopilot and fly the airplane “by hand” through the ice – so they could “feel” the effects of the ice? You bet.

ils23-kbufWas the Instrument Landing System for runway 23 operating properly that night? A few weeks before the crash, Southwest Airlines pilots warned of a glitch caused by terrain beneath the approach path to runway 23 that might cause an aircraft on autopilot to suddenly pitch up – chasing the needle – trying to intercept an errant radio beam. The FAA downplays this as a factor – saying the glitch is noted on charts. But I do not see any reference to this on the government issued diagram (“approach plate” in pilot parlance) for the Instrument Landing System approach to runway 23 at BUF. Apparently this would only be a factor for aircraft turning right toward the approach to runway 23 from the north. Colgan/Continental 3407 was turning left from the south. Stay tuned on this one.

Finally, did the crew manage the aircraft properly given the conditions and circumstances that night? Was the ice a distraction that caused them to ignore some basic rules of airmanship (like maintaining a safe speed)? Or was the ice a red herring – that caused them to make matters worse when the plane automatically tried to pitch the nose downward (apparently to prevent an aerodynamic stall)? Did they presume it was a so-called “tailplane stall” – wherein the recovery calls for the pilot to pull the nose up? (see previous post).

Or was it a combination of some or all of these factors? Don’t chase the needles.

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The “Groundhog Day” Accident

February 16, 2009

What made this crash more than tragic was that it was foreseeable and likely preventable if not for the preference of profit over safety in some of the aviation industry and for the lax oversight of the Federal Aviation Administration in its failure to adequately address known safety risks related to icing.

Jim Hall, former chairman of the NTSB, quoted in the Buffalo News.

sld_icing1In aviation, there is an expression that the rules, regulations, designs and procedures are “written in blood” – meaning the tremendous safety that is built into our  air transport system comes at the steepest price of all: human lives. It is is a grim reality, but when people die in airplane crashes, the lessons learned generally do make it less likely history will repeat itself. We are supposed to learn from our mistakes, right?

Except, it seems, when it comes to ice. For as long as pilots have dared to fly their airplanes into the clouds, they have found themselves grappling with this efficient killer – and yet the accidents keep happening again and again – as if we are all living in Bill Murray’s “Groundhog Day” nightmare.

While it is way to early tbufo know what happened with certainty, he crash of Colgan/Continental 3407 in Buffalo appears to be a tragic replay of the the Comair crash in January 1997 outside Detroit, which itself was a repeat of the American Eagle crash in Roselawn, Indiana in 1994 – which had all the elements of the crash of American Airlines Flight 63 in Centerville, TN – in October of 1943!

There are plenty of other deadly crashes in between – way too numerous to mention (the grim list is here) – but some of them may be lodged in your memory: the Air Florida crash into the Potomac in Washington DC in 1982 – the DC-8 carrying US troops home for the holidays that went down in Gander, Newfoundland in 1985 – the USAir crash on takeoff at LaGuardia in March 1992 – or the chartered jet carrying TV executive Dick Ebersol and his family that crashed in Colorado in November 2004.

We are now in our seventh decade of watching ice laden planes fall out of the sky and you have to wonder why. The National Transportation Safety Board is also wondering. The Board made some recommendations to the FAA aimed at reducing the risks – and put them on top of its so-called “Most Wanted” list.

The NTSB is asking the FAA to:

  • change the way manufacturers evaluate new airplanes for performance in icing conditions.
  • require manufacturers to demonstrate their aircraft can operate for extended periods in Supercooled Large Drop icing conditions (cause of the Roselawn crash) or provide pilots a warning that these conditions exist so they take evasive action.
  • create more specific procedures for operation of ice protection systems and when to fly out of icing conditions.
  • require additional testing – with revised criteria – of turboprop airplanes currently in service to insure no unsafe conditions exist.
  • require flight crews to activate pneumatic boot systems to knock off ice the moment they encounter icing conditions.

In 2007, the FAA  put  these ideas into the rule-making pipeline – but only the rule that changes the way new airplane designs are tested for ice resilience has been made the the law of the land. It’s now been 15 years since the Roselawn crash – which crystallized (if you will) the impetus for change – and the rule-making process appears frozen in time.

“The pace of the FAA’s activities in response to all of these recommendations remains unacceptably slow, despite some encouraging action during 2007,” says the NTSB.roselawn

For its part, the FAA says it “has taken short-and long-term safety actions over the past 15 years to improve safety of aircraft that encounter icing conditions on the ground and in flight.” And it released a fact-sheet with a tally of actions taken since Roselawn. It boasts of “100 airworthiness directives to address icing safety issues on more than 50 specific aircraft types.”

But the rules that would change either require installation of ice detection equipment or changes in the way ice protection systems are operated – and the rule that affects supercooled large drop icing remains in limbo pending an “economic analysis.”

Whatever the bottom line may be when the bean counters are done, it is axiomatic that safety costs money – and the converse holds as well. The fact is, the airlines are not doing well (they were a leading edge indicator for the rest of us, I suppose) and the FAA has to walk the line between mandating safety improvements – and placing financially unbearable regulations on an ailing industry. It is probably no coincidence that the only rule that has been codified affects aircraft designs in development – and thus will not incur any direct costs to the airlines.

To borrow a phrase, if you want to know why ice is still killing people in airliners – you must follow the money. Blood money.

Tailplane Icing Tested, Explained – by NASA

February 14, 2009

Check out this tape from NASA’s Glenn Research Center in Cleveland. It is 23 minutes long, but it is worth your time if you want to fully understand what might have happened to Colgan/Continental 3407. It explains the phenomenon of Tailplane icing in stark, frightening detail.  The key points: the horizontal stabilizer collects ice faster (and holds more of it) than the wing. It is impossible for a flight crew to see this. NASA says if the crew sees any ice at all on wings, they should assume there is more ice on horizontal stabilizer. The problem is often discovered on approach – when the flaps are extended. If the tail stalls at that point recovery is very difficult – if not impossible. Flying on autopilot you would never feel the symptoms of TP icing – which include difficulty trimming the airplane – or oscillations.  In severe cases of TP icing, the yoke goes all the way forward to the stops – and it requires 170 pound of pressure to pull the back on the wheel. Full deployment of flaps is not advised when there is ice on the stabilizer. Film shows dramatic testing of this kind of icing – and its impact on a de Havilland DH6 (the Otter) – cousin to the Dash 8 that crashed on approach to BUF.  Chilling point to remember: Lowering flaps is the trigger. When you lower the flaps, the yoke shakes, and it seems just like a typical wing stall. But if you try a standard wing stall recovery, “you and your passengers could become history,” says NASA. Tip of the hat to Jon Regas for finding this. Link to video here.

Thoughts on Ice and Aviation…

February 13, 2009

(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…