Kirtland AFB, NM
8 Aug 2002
AIRCRAFT ACCIDENT INVESTIGATION
On 8 August 2002 at approximately 1610 (all times are local), the mishap aircraft (MA), a UH-1N, S/N 69-6612, crashed on Pad 8 of the auxiliary field (N34-57.16 W106-33.95), approximately 5 NM south of the Albuquerque International airport. The crew on the MA consisted of five people, the mission instructor pilot (MIP), two mission student pilots (MSP1, MSP2), mission flight engineer (MFE), and a student flight engineer (SFE). The MA was on a scheduled contact check ride on the MSFE, a contact training flight on the MSP2, and an ungraded remedial training flight on the MSP1. All three students were in UH-1N qualification training. The MSP1 had been graded “unsatisfactory” in manual fuel operations on the previous day’s recommendation flight for manual fuel operations due to an over speed on the manually controlled engine. The MA too-off seven minutes early at 1353 on a VFR flight plan to the auxiliary field. Two hours and 17 minutes after departure, the MA crashed on pad 8 of the auxiliary field. The aircraft was technically destroyed, but the crew was not injured. There was no damage to the landing site.
The accident was the result of pilot error brought on by MSP1 applyhing too much throttle to engine number 1, causing its power to exceed that of the automatically controlled #2 engine. This input results in what is called a swap, a condition where the manually controlled engine provides more power than the automatically controlled engine, effectively creating a single engine situation, and loss of power to the rotor system degrading its ability to produce lift thus causing the helicopter to rapidly descend. The MSP1’s improper control of the MA #1 throttle (the manually controlled/ungoverned engine) placed the MA in a condition which resulted in a momentary loss of power to the automatically controlled engine, placing the MA in a single engine condition without the power to maintain either an in or out of ground effect hover, which resulted in the rapid loss of RPM’s to the main rotor system and started an accelerating descent. Clear and convincing evidence indicates that once the MSP1 had made the throttle inputs it was impossible to arrest the decent of the helicopter due to the lack of time available to recover the #2 engine (governed engine) back to full operating power (2-5 seconds required) and the lack of altitude available to recover the rapidly decaying main rotor RPM (within the first second of the #2 engine reducing power, the main rotor had decayed to 92% of less). The aircraft was not recoverable at that point, the only question was at what rate of decent it would impact. The MIP’s inputs in the 2-3 seconds he had to react where focused on leveling the MA and controlling the yaw axis to prevent MA rollover and blade to fuselage contact. These actions ensured that no serious injuries were suffered by the MA crew.