Primary finding
Probable cause
uncommanded operation of the parking brake, due to a missing tension spring, which resulted in locked brakes and subsequent nose over of the airplane during landing.
Investigator assessment
Analysis narrative
The pilot made an approach to the airport with a passenger aboard. The wind was calm, and the pilot proceeded with a standard traffic pattern. When the airplane touched down, main tire(s) locked, and the airplane nosed over. The pilot stated that he was in a perfect configuration for a three point landing, and there was no warning or indication of a problem until the accident occurred. Examination of the airplane revealed that the left master cylinder tension spring, which was designed to prevent the parking brake lock from engaging, was missing.
Source record
Factual narrative
On October 26, 1996, about 1600 eastern daylight time, a Cessna 140, N83N, sustained substantial damage when it nosed over during landing at the Wakefield Municipal Airport (AKQ), Wakefield, Virginia. The certificated private pilot and passenger were not injured. Visual meteorological conditions prevailed for the flight, and no flight plan had been filed for the personal flight conducted under 14 CFR Part 91. In a written statement, the pilot said he was on approach to runway 2 at AKQ. He further stated: "...The winds were basically calm, as could be observed from the flags next to the airport office. I then proceeded with a standard traffic pattern...I was in a perfect configuration for a 3 point landing, but as I touched down, the airplane front tires violently and abruptly locked up. There was no warning or indication of a problem, but the airplane within seconds flipped forward on its back." The airplane was examined by a Federal Aviation Administration Inspector. The examination revealed that left master cylinder tension spring which is designed to prevent the parking brake lock from engaging, was missing. The Cessna 140 Airplane Operations Manuel stated: "The parking brake control is operated in conjunction with the toe brake...In setting the parking brake, first press the toe brake to the desired brake pressure then pull the control out to engage the locking lever and release the toe brake pressure...." The pilot did recall depressing the toe brakes during the cross country flight to AKQ. -