Yucaipa, CA Private Plane Crash, Aug 1984

HEATED AIR MAY HAVE CAUSED FATAL CRASH.

San Bernardino - The pilot of a small plane that crashed Aug. 27 in Yucaipa, killing four adults and a baby, may have overlooked a law of nature that diminishes aircraft performance on hot days, a Federal Aviation Administration official said.

Because air expands as its temperature rises, warm air has less density than cool air, leaving an airplane with less to "grab onto" as it struggles to become airborne, said Gary Koch FAA Western Region accident prevention coordinator.

The factor, known as "density altitude," also affects an airplane engine's performance, Koch said.

"All indications are he was overloaded with weight plus he was combating the density altitude factors," Koch said. "There, was not enough power for the aircraft to climb."
Temperature has a direct relationship to performance, he said.

"If we overload an airplane (on a hot day) we're only asking for trouble."
Although the plane crashed in the morning, the temperature rose to more than 100 degrees that day.

Killed in the crash were the pilot, SHENG JEN CHENG, 31, and his wife, LI CHIH Li CHENG, 31; his sister, SHU CHUAN CHENG, 29; the pilot's 22-month-old son, SMILEY CHENG; and LO TI CHENG, 30, who was engaged to the pilot's sister. All five shared a Redlands home on West Highland Avenue.

The plane, a single-engine Piper Cherokee 140, was designed to hold four people, officials have said.

All five victims were burned beyond recognition after the plane, which was loaded with fuel for the 200-mile trip to Las Vegas, struck the trailers of a double truck trailer rig in Yucaipa's North Beach area and exploded into flames. It had just taken off from Redlands Municipal Airport.

Koch said the density altitude factor is well known to aviators.

San Bernardino County Sun California 1984-09-23