This mishap was caused by a pilot's over-aggressive rotation, the so-called "snatching the controls" problem. I had just checked out that year in this airplane and as soon as I heard Transport Canada's explanation, I knew it was wrong. They blamed fuel migration for a shifting center of gravity. Most CL604 pilots suspected the pilots almost immediately.
Canada stuck to the fuel migration story for almost four years, placing restrictions on the airplane but not really addressing fuel migration. I flew with a Canadair test pilot in 2001 and took the airplane away from him during takeoff rotation. "Take it easy," I told him, "your manual says 3 degree per second, maybe you should try that for a change." He dismissed my warnings as being overly cautious.
Four years after the Air Transport Canada report, the FAA took the unusual step of reexamining the data. They found the pilot had rotated the nose at 9.6° per second, three times the rate specified in the aircraft operating manual. Looking at other Bombardier test pilots it appeared everyone was rotating at least double the prescribed rate. Had the pilot used the correct rate, the aircraft would have flown under perfect control.
So why does an entire cadre of "test pilots" ignore the flight manuals they are responsible for writing? I think it can be blamed almost entirely on complacency. The best paying jobs at this end of corporate aviation tend to be flying for private owners, and to a lesser degree, charter companies. The aircraft manufacturer offers less pay but the psychological benefit of a business card that says "test pilot." Being among a cadre of test pilots with little or no external oversight leads many to start ignoring established procedure. More about this: Complacency.
The official accident report, while citing the rapid rotation, still mentions fuel migration. The telling fact, however, is that nothing has been done to address this supposed problem. That tells me there was no problem with fuel migration. There are two lessons here:
Everything here is from the references shown below, with a few comments in an alternate color.
Figure: Accident aircraft fuel system diagram, from NTSB Aircraft Accident Brief, figure 1.
The pilot was not, by any definition, an experienced jet pilot ready to take on even a routine test flight of this airplane. He was probably a very good pilot placed into a situation he was ill prepared to cope.
The pilot's rotation rate during the accident flight was 9.6° per second, triple the rate required by the airplane flight manual.
[NTSB Aircraft Accident Brief, AAB-04/01] According to the Bombardier Aerospace Challenger 604 Operations Reference Manual, the PF rotates to 14° at 3o per second after the "rotate" call from the PNF. The same rotation rate is used for an abnormal takeoff (engine failure after V1) but with a reduced pitch attitude of 10°. The rotation rate value listed in the Challenger 604 Operations Reference Manual is based on an industry average for transport-category aircraft takeoff profiles.
[Davies, page 183]
Of course this is precisely the point. Even a minor increase in G-loading decreases stall speed enough to cause one wing or the other to drop off.
[NTSB Aircraft Accident Brief, AAB-04/01] The National Transportation Safety Board determines that the probable cause of this accident was the pilot's excessive takeoff rotation, during an aft center of gravity (c.g.) takeoff, a rearward migration of fuel during acceleration and takeoff and consequent shift in the airplane's aft c.g. to aft of the aft c.g. limit, which caused the airplane to stall at an altitude too low for recovery. Contributing to the accident were Bombardier's inadequate flight planning procedures for the Challenger flight test program and the lack of direct, on-site operational oversight by Transport Canada and the Federal Aviation Administration.
Davies, D. P., Handling the Big Jets, Civil Aviation Authority, Kingsway, London, 1985.
NTSB Aircraft Accident Brief, AAB-04/01, Bombardier CL-600-2B16 (CL-604), C-FTBZ, Mid-Continent Airport, Wichita, Kansas, April 14, 2004
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