by Tony Fernando
Minnesota DOT Office of Aeronautics
Published in Midwest Flyer – August/September 2020 issue
At 10:45 am on April 13, 2018, a U.S. Air Force F-22 Raptor started its takeoff roll at NAS Fallon in Nevada. NAS Fallon is the home of the famed TOPGUN fighter pilot training course, and the Air Force fighter was scheduled to fly in a one-on-one graduation exercise against a TOPGUN student who would be flying an F/A-18. The F-22 accelerated to 120 knots and the pilot rotated. At 135 knots, recognizing visual cues that the fighter was airborne, he retracted the landing gear.
Unfortunately, the fighter was not airborne, although enough weight had been taken by the wings for the weight-on-wheels switch to allow the gear to retract. When the landing gear retracted, the fighter settled back onto the runway, sliding 6,514 feet before stopping. Fortunately, there was no fire and the pilot was not injured. The accident report does not state how much damage was done to the $150 million fighter jet.
Using the prevailing conditions at NAS Fallon that morning, accident investigators determined that the correct rotation speed should have been 143 knots, and the fighter would have been airborne at 164 knots. Rotating early increases induced drag during a critical phase of flight.
In one sense, this is clearly a pilot error accident. A correct procedure existed and the pilot didn’t follow it. However, USAF fighter pilots are amongst the most highly trained pilots in the world. The pilot was highly qualified, and nothing in his training or service record suggested he was struggling with the demands of being a fighter pilot assigned to an elite squadron. Fatigue was not an issue; he was only three hours into his flight duty day and had ample rest over the preceding several days. There was no indication of drugs, alcohol or other substances playing a role. Why would such a pilot make such an elementary mistake?
All of the F-22 bases except for Nellis AFB are located at or near sea level, while NAS Fallon has a field elevation of 3,934 feet. Aircraft engines, jet or piston, provide less power at higher elevations. After the accident, the investigators analyzed the flight data recorders from 73 previous sorties by F-22 pilots. The investigators found that 52% of F-22 pilots rotate at 120±5 knots regardless of the calculated rotation speed, and 80% of F-22 pilots were becoming airborne five knots or more before the calculated takeoff speed. When looking at F-22 takeoffs from high elevation airports (e.g. Colorado Springs), 91% became airborne 5 knots or more before the calculated takeoff speed; 54% were airborne 20 knots or more before the correct calculated speed. At those high elevation fields, 81% of F-22 pilots had retracted the landing gear before takeoff speed.
Given these statistics, the accident described here was inevitable. The F-22 pilot community had internalized a procedure of rotating early, thus becoming airborne early. This practice worked fine at the sea level airports from which the F-22 is normally flown, but greatly increased risk at high elevation airports. The accident board was not able to determine where the early rotation practice originated or how it spread through the pilot community, but by the time of the accident, it clearly had been culturally accepted.
Culture develops in any group of pilots. General aviation is no exception. Pilots who routinely operate out of grass strips, or fly a specific type of airplane, develop habits that are passed from one pilot to another. Culture is not inherently a bad thing. Aircraft manufacturers can hardly anticipate every scenario their aircraft might be placed in. The hazard is when we allow culture to override established procedures. We might takeoff over gross because we “know” the aircraft can handle it, or because we don’t feel the need to get the actual weight of our passengers. We might forgo doing a takeoff distance calculation because we’ve internalized that the airplane has enough performance to meet the demands we ask of it. We can get away with these practices until the conditions are outside what we’ve experienced (e.g. high elevations, hot days, strong crosswinds, poor braking action, etc.). A raft of accidents suggest that pilots are not great at identifying when not to apply procedures developed through hangar flying.
Can an accident involving a very high-performance military fighter jet be relevant to general aviation? As pilots we learn a lot from hangar talk and tribal knowledge. But as pilots, we have also been trained and tested on proper procedures. This summer, as we fly to new and unfamiliar airports, pay attention to how you calculate your takeoff performance numbers, especially at high elevation fields out west. Follow the procedures in your aircraft’s manual. There’s no reason for you to be the pilot who has an accident from using an informal, culturally-developed procedure under the wrong conditions.
All speeds reported as knots calibrated airspeed (KCAS).
Reference: Trigler, J. 2018. F-22A Mishap, Naval Air Station Fallon, NV. United States Air Force Accident Investigation Board Report. 29 pages.