Several years ago, two active-duty Air Force pilots (one an instructor) rented a Cessna 172 in Del Rio, Texas, so they could take their dates for a flight. The two pilots sat up front with two passengers in the back seat and a heavy load of fuel in the wings. (In case youre thinking ahead, the aircraft was 323 pounds over its maximum allowable gross weight and 3.1 inches beyond its allowable aft C.G. limit.)
They took off and proceeded to perform aerobatic maneuvers at very low altitudes while also buzzing boats on the nearby lake. They performed at least one complete aileron roll, abrupt pull-ups, very abrupt level-offs at low altitude and hammerhead type turns.
The last maneuver was a steep pull-up and climb followed by a hammerhead turn and a delayed pullout at the bottom. The timing of the pull-out was too late and the aircraft violently impacted the terrain. All four occupants were killed.
The tragic event was captured on video by boaters. The commanding general of the Air Forces Air Training Command grounded everyone for a day to watch it. As a lieutenant at the time, I remember my squadron mates sat there in awe watching the video. It made a very lasting impression on some of us. The message was clear – clowning around, especially at low altitudes – can kill.
Rolling Thunder
Though the thought of using a Cessna 172 for aerobatics may leave you wondering, hold on, it gets better – or worse. The chief of the 92nd Bombardment Wings Standardization and Evaluation Section at Fairchild Air Force Base in Spokane, Wash., had more than 5,200 hours of flying time and had flown the B-52 since 1971. He was considered by commanders to be one of Strategic Air Commands best B-52 instructor pilots.
His not-so-secret lifetime goal was to roll a B-52. Between 1991 and 1994, he broke numerous military and civilian aviation regulations regarding low-level maneuvers, yet military commanders did nothing to stop the continuing string of transgressions.
Finally in 1994, while practicing for an upcoming airshow, the pilot grossly exceeded pitch and bank limits in the B-52 while at low altitude, ultimately slamming into the ground and killing all on board.
If trying aerobatics in a Cessna 172 or a B-52 is a bad idea, then trying them at low altitude is even worse. Even when using aircraft that are capable of aerobatics, low altitude aerobatics can be just as deadly.
An OV-10 Bronco aircraft, operated by the Bureau of Land Management as an air attack aircraft used for aerial fire fighting and flown by a former military pilot, departed from Bakersfield, Calif., on a local flight. The pilot proceeded to buzz one of his former fire bases.
Four witnesses from the fire station observed the aircraft fly by at approximately 200 feet agl and initiate a roll to the right. The aircraft continued the roll until it was nearly inverted, then the pilot reversed the roll direction in an attempt to level the wings. The aircraft struck the ground in approximately a 90-degree bank attitude.
Even when the right equipment is used by a pilot qualified to do low-altitude aerobatics, mistakes can still happen.
An experienced airshow pilot was performing aerobatics at an airshow in Salt Lake City in a Pitts S-2B that had been modified with main landing gear added to the top of the wings so the pilot could land upside-down. The pilot reported that the aircrafts engine momentarily lost power during inverted flight at the top of a loop. He attempted to complete the loop but descended in a high speed stall.
The aircraft struck the runway in a level attitude and became airborne again, then impacted on its right wing, cartwheeled and came to rest against the airport perimeter fence. Perhaps surprisingly, the pilot was unhurt.
There are a lot of reasons why low level aerobatics should be performed only by the right person, with the right equipment, in the right environment, using the right procedures and with the right safety margin.
One of the inherent problems with low level aerobatics is that the safety margin is very thin. An engine failure at altitude over the wide wheat fields of Kansas leaves plenty of time to come up with a strategy for a low-risk landing.
At low altitude, there is no such margin. You wont have time to diagnose and solve the problem, and the landing options are narrowed to the ground immediately below you. Chances are you wont have time to set the landing configuration, stabilize the descent or even slow down.
When mechanical malfunctions occur at altitude, a minor deviation in the airspeed, heading or attitude while youre looking for the emergency checklist probably wont kill you. At low altitude, however, there is no such luxury. The small distraction of looking at the oil pressure gauge can cause a moments lapse of monitoring the aircrafts attitude and performance – and at low altitude, that can kill.
The precision of control inputs must be very accurate. For example, as the aircraft rolls past 90 degrees of bank, the lift vector is actually pointed downward. If you didnt put any correction into the controls to correct for this roll, the aircraft would quickly start losing altitude, especially in relatively slow rolling aircraft.
A CFI in a Cessna 152 made a low pass over a runway, telling friends over the unicom frequency to come outside to watch. At the end of the runway, the aircraft pulled up and started a roll. As the aircraft passed through 125 degrees of bank, the aircraft descended and impacted the ground. Both the CFI and the student were killed.
Pressures On
Slight deviations in the pressure youre holding on the stick are probably not even noticeable at altitude, but when youre close to the ground theres precious little time for recognition and recovery.
The pilots perception of time and distance are extremely distorted while flying low. Lines and angles that appear to be straight at altitude suddenly seem curved or crooked. These perceptual distortions may or may not be obvious to the pilot.
At the outer edges of the windshield, the curvature of the windshield can distort lines and angles, creating a visual illusion of the ground, and more importantly, your distance from the ground. The distance traveled from the top of a loop to the ground can be seconds. There is little time for the pilot to react to compensate for error. Even when you do make a control correction, even the most nimble of aircraft wont change its flight path instantly.
The recent Air Force F-16 crash during a low-altitude aerobatic maneuver at an airshow in Kingsville, Texas, and a Marine FA-18 crash at an El Toro airshow in 1986 demonstrate amply that efforts to correct an improper flight path may be fruitless, regardless of the airplane involved.
Hauling back on the stick wont do much good for several reasons. First, you can easily enter a high-speed accelerated stall that will end with contact with the ground. Second, you can easily over-stress the aircraft, which isnt going to help the situation any. Third, the aircraft has a certain degree of momentum to continue along its flight path.
Even if you rapidly pitch the aircraft, it will actually take a few moments for the aircraft to start changing its flight path. During those precious seconds or moments, you are still screaming toward the ground.
There are a host of human factors, both sensory and perceptual, that make pilots prone to mistakes at low altitude. The ultimate lesson, however, is best understood simply by considering one of these airshow mishaps. Certainly the best way to prevent this type of accident is to resist the temptation to show off.
Low altitude aerobatics just arent worth it. There is a proper time, place, environment and aircraft for aerobatics, and for 99.99 percent of pilots, its not looping and rolling at low altitudes.
-by Patrick Veillette
Patrick Veillette admits to having done a lot of dumb things, but low-level aerobatics arent among them.
