Date: 201501
Aircraft: Gulfstream V / G500 / G550
Operator: Fractional
Operating under: Part 91
Flight plan: IFR
Flight phase: Parked
Aircraft component: APU
Component problem: Malfunctioning
Reporter organization: Fractional
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Pre-flight
Result: General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft; Human Factors
Primary problem: Aircraft

Narrative: I arrived at the aircraft to preflight for [standby] duty and found large amounts of oil on the aircraft belly underneath the APU. I took pictures of the mess and emailed them to maintenance. I wrote up the aircraft as directed by maintenance as an AOG [Aircraft on Ground] item with an oil leak.[The next day] I went back out to the aircraft to do a ferry flight then a revenue trip. We noticed that the access door where you control the main cabin outside door switch was open and swinging in the breeze along with no red/blue security sticker on the baggage door. We called security and finally found out that the mechanics that said they could not find an oil leak left the panel open and did not sticker the baggage door. But....the Belly of the aircraft was all cleaned up (no oil leaks) and signed off as no leaks found on the APU. We fired up the APU and proceeded to prepare the aircraft for flight. After about 10 minutes my first officer came up to me after loading crew bags and said there was oil leaking out of panels around the APU. I shut down the APU; took pictures and emailed them to maintenance. At this time the mechanic that inspected the aircraft the day before came out of nowhere up the stairs and asked 'what's the problem' we told him about the oil and went back to show him the new leakage. When we got back to the aft belly area the oil was ALL WIPED UP! He said he had just wiped it up. I told him the aircraft was leaking again and he said it was just residue oil from someone previously filling/spillage the APU with oil. I asked him why this 'residue oil' didn't leak out during last night but started leaking again after we started the APU. He looked at me like I was stupid. I; myself; since 1984 have kept current my Airframe and Powerplant mechanic's license along with my FAA Inspection Authorization and know when an aircraft is leaking! We MEL'd the APU; got a huffer; started the main engines and ferried to [our interim destination]. I followed the maintenance line on this aircraft and sure enough some lines; elbows and hoses were ordered for the APU oil leak repair.The suggestions I have are: #1: Not to let inexperienced mechanics touch a Gulfstream G550 (it impacted an owners trip) #2: Do we or do we not investigate the experience level of these mechanics as to which aircraft they have experience on? #3: Is this so called mechanic a 'jack of all trades' working on all of our aircraft with very little experience on any of them? #4: Was THIS mechanic ever at a Gulfstream factory maintenance initial or recurrent [training session]? I don't think anyone can 'save money' with cheap mechanics; this is proven history in the aviation business. #5 Let us not forget that we can't run these Gulfstream APU's in flight because the sealant around its enclosure isn't fireproof and can you imagine if we get an APU fire going in the aft compartment? #6: My grandfather taught me two things: 1: A lazy man does the most work. 2: If you get too greedy you get caught.




Synopsis: A G500 Captain took exception to the attempt by a Mechanic to insist a twice 'wiped' APU oil leak was merely the result of overfilling. A later inspection of the aircraft records verified there was a significant leak requiring the replacement of fittings and hoses for proper repair. The flight at risk was flown with the APU deferred inoperative utilizing ground power for start and pneumatics.