NYC01LA025

The pilot of a Cessna 172 was en route between two airports, on a heading of about 300 degrees, when it crossed the final approach course to another airport, which handled large airplanes. A Boeing 757 was on final approach, on a heading of about 360 degrees to that airport. The pilots of both airplanes were in contact with approach control, and acknowledged visual contact with each other. The pilot of the Cessna also acknowledged a caution for wake turbulence. The Boeing was descending. The Cessna crossed the flight path of the Boeing about 30 seconds after the Boeing passed through, at the same altitude. The pilot of the Cessna reported he was thrown about the cockpit, as the airplane rolled left and then pitched nose down. The pilot of the Cessna recovered to normal flight and landed at his planned destination. Post flight examination of the Cessna revealed wrinkled skin on top of the right wing, and further examination revealed a cracked rear spar underneath. The Aeronautical Information Manual recommended, 'Pilots should fly at or above the preceding aircraft's flight path, altering course as necessary to avoid the area behind and below the generating aircraft.' Surface winds were from 300 degrees at 16 knots with gusts to 24 knots.

On October 19, 2000, at 1438 Eastern Daylight Time, a Cessna 172M, N950ME, was substantially damaged when it encountered wake turbulence from a Boeing 757-200 (C-32A), operated by the US Air Force as Venus 91, about 6 miles south of Andrews Air Force Base (ADW), Camp Springs, Maryland. The certificated private pilot was not injured. Visual meteorological conditions prevailed for the personal flight. No flight plan had been filed for the flight that was conducted under 14 CFR Part 91.

The pilot of the Cessna reported that he had departed Cambridge-Dorchester Airport (CGE), Cambridge, Maryland, and was en route to Potomac Airport (VKX), Friendly, Maryland, on a heading of about 300 degrees. The route of flight of the Cessna took it south of Andrews AFB. The pilot of the Cessna was in radio contact with Andrews Approach Control.

The Boeing was executing the NDB approach to Runway 01L at Andrews AFB, and was on a heading of about 360 degrees. The pilots of the Boeing were in radio contact with Andrews Approach Control.

According to a transcript of the air/ground communications between the pilots of both airplanes, and the arrival controller at Andrews AFB, the pilots of both airplanes had been advised of the presence of each other and reported each other in sight.

At 1437:30, the arrival controller transmitted, "...zero mike echo, just un, verify you have the seven fifty seven in sight and pass behind him." The pilot of the Cessna replied, "We got him, we'll make sure we pass behind." The arrival controller then transmitted, "Okay caution for the wake turbulence", and the pilot of the Cessna replied, "Thank you for that."

The pilot of the Cessna reported that as he neared a point behind the Boeing, he initiated a climb from 1,300 feet to 1,600 feet. As the airplane neared 1,600 feet, it encountered turbulence and rolled to the left. The pilot said he was thrown about the cockpit and when the turbulence ended, the Cessna was descending in a nose low attitude. The pilot regained control of the airplane and landed at Potomac Airport.

Radar data revealed that at the point where the flight paths of the two airplanes crossed, the Boeing was on a descent and its altitude was recorded as 1,500 feet. The Cessna had climbed to 1,600 feet, and then about 10 seconds prior to crossing the flight path of the Boeing, descended to 1,500 feet. After passing the flight path of the Boeing, the Cessna descended to 1,400 feet, and maintained that altitude for the next minute of flight.

After landing, the pilot of the Cessna noticed wrinkles and deformed skin on the top surface of the right wing, and on the left aileron.

An airworthiness inspector from the Federal Aviation Administration (FAA), examined the airplane and reported that the rear spar on the right wing was cracked.

According to the Aeronautical Information Manual (AIM), Section 7, Wake Turbulence, Vortex Behavior;

"...Pilots should fly at or above the preceding aircraft's flight path, altering course as necessary to avoid the area behind and below the generating aircraft...."

Surface winds were from 300 degrees at 16 knots with gusts to 24 knots.