C-5 Crash At Dover AFB in April Blamed On Crew Error
World News & Analysis
C-5 Crash At Dover AFB in April Blamed On Crew Error
Aviation Week & Space Technology
06/19/2006, page 28
David Hughes
Washington
An experienced crew gets complacent returning to home base on a clear day
Printed headline: C-5 Crew Error Crash
A U.S. Air Force accident investigation board has concluded that the cause of a C-5B crash near Dover AFB, Del., on Apr. 3 was a series of primarily pilot errors that resulted in the aircraft stalling into the ground.
All 14 crewmembers from the USAF Reserve's 512th Military Airlift Wing and three passengers survived. Some were seriously injured. The aircraft crashed and broke into two large pieces about 2,000 ft. short of the runway during an emergency return to Dover.
The aircraft weighed 742,000 lb. and was bound for Ramstein Air Base, Germany, with 105,000 lb. of cargo when the crew decided to shut down the No. 2 engine after a "thrust reverser not locked" light illuminated. If a thrust reverser deploys in flight with the engine running, it would be a serious hazard.
The pilots then canceled the instrument flight rules clearance, for reasons not in the report, and requested a visual approach to Dover's runway 32--3,300 ft. longer than the instrument landing system-equipped runway 19.
The pilot was in the right seat and was certified as a C-5 flight instructor. He was chosen by the pilots to fly the emergency return so he could log the sortie. During the descent, he pulled throttles for the remaining operating engines 1, 3 and 4 to idle. When later advancing the throttles, he mistakenly advanced throttle 1, 2 and 4, leaving No. 3 at idle (29% fan speed) for the duration of the flight. In effect, the pilot used above-idle thrust on just two of the three functioning engines until ground impact. This error and corresponding engine-instrument indications were missed by the pilot in the left seat (a C-5 flight examiner), the pilot in the jump seat and the flight engineers who monitor engine performance.
The accident board found the cause of the mishap was the pilots' and flight engineers' failure to use the fully operational No. 3 engine, the instructor and primary flight engineer's failure to brief the approach and the pilot's failure to use 62.5% or 40% flaps for the approach. Col. Raymond Torres, president of the accident investigation board, says the Air Force directs pilots of heavy-weight aircraft (above 632,000 lb.) to use 40% flaps on an engine-out approach--not 100% flaps.
While flying with the landing gear extended at 500 ft. above ground about 4 mi. from the runway, the pilots selected 100% flaps--an action not normally taken on a three-engine approach until landing is assured. Normal glidepath at this point should have put the aircraft at about 1,200 ft. The investigation board said the 100% flap selection was premature, based on the heavy weight, speed, altitude and position of the aircraft relative to the runway. The crew's call for a visual approach and descent below the normal glidepath was another cause of the accident, the board says.
After selection of 100% flaps, the aircraft continued to descend. The target approach speed for 100% flaps was 146 kt., with minimum control airspeed at 133 kt. But the pilot was unable to maintain the target airspeed, and the aircraft slowed to 127 kt. Descending through 150 ft., the crew selected 40% flaps (apparently to reduce drag), causing an immediate stall due to loss of lift. The 127-kt. speed was 40 kt. below the target speed for 40% flaps. The accident board noted that even without this change in flap setting, the plane would have stalled and crashed short of the runway.
The aircraft impacted the ground in a "very nose-high attitude" of 18-21-deg. angle of attack. The tail struck the ground first, even before the main landing gear, with a 10g force as the empennage broke off. Then, the nose slammed down with 30g of force, breaking the fuselage into two major sections.
There was no post-crash fire or explosion, despite the aircraft carrying 250,000 lb. of jet fuel. The C-5 had nitrogen in the airspace above the JP8 fuel in the tanks. The main and auxiliary tanks ultimately ruptured, and more than 1,000 gallons of fuel spilled on the ground. There was no spark to set it on fire.
The board says the crew was complacent and failed to realize the potential risk of a heavy-weight, full-flap approach and landing. Torres says simulator sessions showed if any of three errors (flying below the normal glidepath, using less than the available thrust on the three running engines or selecting the 100% flap setting) had been corrected, the aircraft could have landed safely.
For example, simulator sessions showed that using the No. 3 engine as late as 300 ft. above the ground resulted in a safe landing. The accident aircraft stalled at 150 ft. Another scenario showed that using a 62.5% or 40% flap setting and the related approach speed without using the No. 3 engine above idle led to a safe landing. And a third scenario showed that flying an ILS or tactical air navigation approach to the runways at the base at the right altitudes would have worked even without the No. 3 engine above idle and flaps at 100%.
Torres says that crew performance in this accident did not meet the Air Force's professional standards, but he does not know if any disciplinary action will be taken against crewmembers.
The C-5 in the accident was recently fitted with the avionics modernization program system, which worked properly during the flight.
Wally Magathan, a former C-5 aircraft commander and flight instructor, contributed to this article.
Besides, what else am I supposed to do on a layover in Mumbai?
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