US Air Force,
LANGLEY AIR FORCE BASE: An improper stabilizer trim setting caused the July 21 crash of a B-52 Stratofortress aircraft northwest of Guam, according to an Air Combat Command accident investigation board report released Feb. 13.
Analysis of aircraft parts found during salvage operations revealed the aircraft's stabilizer trim was set between approximately 4.5 and 5.0 degrees nose-down at impact. According to the investigation board, this indicates an improper stab trim setting of an aircraft in a nose low descent at low altitude.
The stabilizer trim is a control function used in conjunction with the aircraft's elevator to control the pitch of the aircraft. Pilots will first push or pull on the aircraft yoke to use the elevator to change pitch. They will then use stabilizer trim to ease handling of the aircraft. The stabilizer trim moves the stabilizer so that the desired pitch is held with the elevator in a neutral position.
Through extensive interviews, and using radar data with simulator and computer modeling, the accident board was able to simulate the turn, descent and aircraft crash. With this modeling, they were able to rule out multiple other causes and scenarios due to lack of supporting evidence.
Based on the generated profile and recovered aircraft parts, the board focused on possible problems with the stabilizer trim function. With no surviving aircrew members, no emergency radio calls and with minimal recovered aircraft control systems or instruments, the specific reason the stabilizer trim was mis-positioned could not be determined by the AIB.
The AIB president also found that the combination of low altitude with a descending left turn of the mishap aircraft and late recognition of the serious nature of the situation by the aircrew contributed to the mishap. The board noted that any experienced aircrew could have found it difficult to recognize, assess and recover from the rapidly developing situation involving the stabilizer trim setting.
Six Airmen perished in this accident: Maj. Christopher Cooper, aircraft commander; Capt. Michael Dodson, copilot; Maj. Brent Williams, radar navigator; 1st Lt. Joshua Shepherd, navigator; 1st Lt. Robert Gerren, electronic warfare officer; and Col. George Martin, flight surgeon. Their remains were laid to rest in a ceremony Nov. 14 at Arlington National Cemetery.
The B-52 aircrew was flying a training mission that included a flyby in support of the Guam Liberation Day celebration. The B-52 was assigned to the 20th Bomb Squadron, Barksdale Air Force Base, La., and temporarily assigned to the 20th Expeditionary Bomb Squadron, Andersen AFB, Guam. The aircraft was deployed to Guam as part of the Department of Defense's continuous bomber presence mission in the Pacific.
All the crewmembers were assigned to Barksdale AFB, except Colonel Martin, who was assigned to the 36th Medical Group, Andersen Air Force Base, Guam, at the time of the accident.
For the AIB report, click here.
