20000318006712A

(-23) Instructor and private pilot onboard decathalon N2520Z were on final approach to van sant airport (9N1) and were overtaken from behind and involved in collision with a pawnee, N7460Z, which was returning from a glider tow. Both a/c were substantially damaged. Both pilots on the decathalon and the pawnee pilot sustained only minor injuries. (.4) the flight instructor and private pilot flew the Bellanca airplane in the traffic pattern for several minutes, and were on the fourth approach to the runway at the time of the accident. The private pilot said they flew a 'squared off traffic pattern' and were approximately 50 feet above ground level (AGL) on final approach when the other airplane's shadow passed over. The pilot of the Piper said he entered the traffic pattern on the downwind leg, but flew a modified base leg to final for noise abatement. Witnesses described the Bellanca above and behind the Piper after both airplanes turned final. They said the Bellanca overtook the Piper as it descended below the Piper in a slip. Three witnesses said the Bellanca slowed, pitched up, and was struck from behind by the Piper. One witness said the Bellanca's app roach was on the runway heading, while the Piper's approach was '...tracking inbound left of the centerline on a slight angle.' The crew turned off the Bellanca's radios after engine start, and the Piper was not equipped with a communication radio. There was no locally published procedure for flight in and around the traffic pattern nor were there any depicted 'no fly' areas for purposes of noise abatement. According to the aeronautical information manual: 'when two or more aircraft are approaching an airport for the purpose of landing, the aircraft at the lower altitude has the right of way, but it shall not take advantage of this rule to cut in front of another which is on final approach to land, or to overtake that aircraft.' Each pilot reported there were no mechanical deficiencies with their respective airplanes.