TEB crash prompts NTSB safety recommendation

 - July 30, 2008, 6:16 AM

The NTSB issued safety recommendations A-08-48 and -49 on July 17 warning that pilots may decide to abort takeoffs in Bombardier Challengers if the pilots mistakenly set the pitch trim too far forward, even though the aircraft will lift off at a speed above V2 in that configuration.

When it investigated the Feb. 2, 2005, Challenger 600 aborted takeoff accident at Teterboro (N.J.) Airport, the Safety Board found that “in the mistrim scenario, with the [center of gravity] at the most forward limit and with the horizontal stabilizer at the nose-down limit of the takeoff green band, the airplane did not rotate, even with full nose-up elevator control, until it was significantly above the nominal rotation speed (V2).”

The NTSB found the cause of the accident to be the fact that the Challenger “had a center of gravity that was significantly forward of the airplane’s forward limit, which severely degraded the airplane’s ability to rotate” and that “neither pilot used the available weight and balance information appropriately.”

The NTSB said that pilots in this type of mistrim scenario may elect to abort the takeoff at a high speed because they believe the airplane won’t fly. “A delay of this length in the most adverse trim condition is an excessive delay that constitutes an ‘unsafe flight characteristic,’” the NTSB claimed, although certification regulations do not “state explicitly that an excessive delay in rotation during the mistrim is an ‘unsafe flight characteristic’ to be evaluated during certification testing.”

The Safety Board recommends that the FAA revise certification advisory material to address mistrim-takeoff rotation delays and that Challenger operators “provide training to their pilots that emphasizes the importance of the proper takeoff stabilizer trim setting.”

The NTSB recommended that Transport Canada encourage Bombardier to revise its Challenger quick reference handbook (QRH) to include details on setting stabilizer trim, which are not currently in the handbook. However, FlightSafety International publishes the QRH.

The NTSB did not say whether it has simulator tested forward cg/full forward trim configurations in any other jet types.