Pilots 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.
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.
Was 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.