Background
On the day of the accident, six Learjet flight crews from the same operator planned near-simultaneous departures from Hohn Military Airport for separate missions. The accident aircraft was the third to take off. It was a Learjet 35A with two pilots: the Pilot Flying (PF) in the left seat and the Pilot Monitoring (PM) in the right seat. The flight was scheduled to proceed to Wunstorf Military Airport for several instrument approaches to train local air traffic controllers, while also serving as a proficiency check for the left-seat pilot's type and instrument rating.
Flight and Sequence of Events
Before engine start, the pilots completed the Before Starting Engine checklist, which included a Yaw Damper check and a Full Travel check of the flight controls. The right engine was started at 1224 hrs and the left at 1226 hrs. At 1237 hrs, while on taxiway C3, the crew performed the takeoff emergency briefing. At 1238 hrs, another Learjet received takeoff clearance with a simulated engine failure and departed. The accident aircraft then taxied to Ramp 1, turned, and waited for clearance to line up on runway 26. At 1244 hrs, the crew was instructed to roll onto runway 26 and hold. They completed the Line-up check and Before Takeoff check, planning a takeoff with flaps set to 8° and engine full thrust targeting N1 of 96.6%.
Takeoff clearance was received at approximately 1247 hrs, and the airplane lifted off at 1247:34 hrs near taxiway C3. According to the Cockpit Voice Recorder (CVR), after takeoff the PF directed the PM to retract the landing gear and engage the Yaw Damper. At 1247:39 hrs, the PM announced, "in advance, you will lose the right engine," and the PF acknowledged. The right engine thrust then reduced while the left engine maintained takeoff thrust. The Flight Data Recorder (FDR) indicated an airspeed of about 160 kt at that time. At 1247:44 hrs, the PF called "Damper on," and the PM responded. Moments later, the PF exclaimed quietly "Oh shit" followed by louder expletives. The last recorded sounds were a landing gear warning "Too low" at 1247:55 hrs.
During this period, Hohn Tower transmitted traffic information about two Tornado aircraft nearby and instructed a frequency change to Hohn Radar. Witnesses observed the airplane perform a snap roll and then impact the ground at the end of the runway. An explosive fireball occurred on impact. Both pilots suffered fatal injuries and the aircraft was destroyed.
Probable Cause
The official investigation determined that the accident resulted from loss of control due to an untimely or significantly too low rudder deflection to correct the asymmetric thrust after the simulated engine failure. The large yaw angle caused a stall of the vertical tail and subsequently the wing, leading to an uncontrolled roll. The exact reason for the insufficient rudder deflection could not be determined with certainty.