Control linkage reversal during maintenance appears likely to have caused last month's crash of the Spectrum Aeronautical Spectrum 33 very light jet (VLJ) prototype, according to US National Transportation Safety Board (NTSB) "preliminary information". The NTSB says: "The aircraft entered a right roll almost immediately after take-off. The roll continued to about 90° when the right wingtip impacted the ground."

Both test pilots were killed in the 25 July crash on take-off from Spanish Fork airfield, Utah.  The NTSB reports that this was the first flight following maintenance that required the disconnection and reassembly of part of the roll-control mechanism, a system of torque tubes, push/pull tubes and a "translation linkage". This linkage involves bell cranks that convert the torque tube rotation to the mechanical push-pull movement that operates the ailerons. Because of the crash damage, says the NTSB, "aileron control continuity could not be established" throughout the system from the pilots' sidesticks to the ailerons. But it says: "Examination of the translation linkage on the aft side of the aft pressure bulkhead revealed that it was connected in a manner that reversed the roll control." A pilot demand for left roll would have resulted in right roll, and vice-versa, the NTSB says.

Source: Flight International