Gulfstream G200 (IAI 1126 Galaxy)
Flight Crew Air Transport Pilot (ATP)
Workload; Distraction; Troubleshooting
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Procedure; Aircraft
During preflight of aircraft that was coming out of a dual engine change it was noticed that APU access door was partially closed/locked. This is perhaps a similar event that occurred on another aircraft during preflight on similar event.  On this date and upon closer inspection of APU access door it was noted that the door was indeed locked; but it seemed not correct. Upon use of ladder and closer inspection is determined that outer door latches were place in locked position BEFORE door was closed.  The separate key lock for the door was in proper position and lower push button type locks were in down/locked position. Those were correct; but the push buttons on the 9 o'clock and 3 o'clock were already in down position when door was opened. Door was then properly secured and flight was normal and uneventful. This may or may not have been a similar situation that occurred on subsequent event on the other aircraft when APU access door opened in flight that required FAA/NTSB investigation. Photos of the door were forwarded to the Company during preflight and was asked to file a report.Particular attention should be taken during preflight inspection and determine that the APU access door is indeed secured properly. It may require opening the door and determine that all latches are properly positioned and in proper location.
A G-200 APU Access Door was closed and locked by key before the outer door latches were closed which could allow the door to open in flight.