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N52202 at Monroe Airport (W16)

This web page is now three sequences, complete with photos: recovery; failed oil pump; disassembly of the airplane for shipment. The aircraft will be repaired by TopGun Aviation, of Stockton, CA, using a new wing being manufactured early this year by the Mooney factory.

The first photo sequence shows how Dave Hilty and his team of two assistants succeeded in pulling the aircraft back onto the runway using heavy supports and 3/4" plywood. They moved the aircraft 5' to 6' at a time backwards through the brush and across a creek, eventually pulling it up over a 4' berm at the end of the runway. Total distance moved: about 100'.

The entire task took about 3 hours 30 minutes. It involved keeping the plane relatively stable as they pulled it up across the berm -- then down on the runway side. It was done without additional scraping or damaging the plane. Early during the recovery process use of a Hughes 500 helicopter had been proposed, but it was believed that the aircraft would be damaged less by this process.

Initial reports: the engine has seized, but not from oil loss. The aircraft has 7 quarts of oil. Hilty's analysis: L wing is a total loss; right wing is questionable. Nose gear damage undetermined.

Click photo for a larger image.

N52202 after the overrun of Monroe RWY25. Picture from Friday, Oct. 6.	8:30 am on recovery day: brush has been cut back. First look at the L wingtip damage caused by impact with a stump.	9 am: The plane's been pulled back 10'.
9:15 am: Airplane's moved another 10' back.	'The Weedwacker' scrawled on the cowl by the recovery team, which saw how much brush the 252 had carried forward during the landing.	10:30 am: About to cross a 3' deep creek.
11 am: Across the creek and ready to climb a 4' berm at the end of the overrun area.	At the berm.	Up at the top -- but now to keep the tail from scraping as N52202 comes down the opposite side.
Marc Gordon gets to remount as pilot to control the brakes as the 252 is pulled backwards.	Looking backwards with the plane back onto the runover area, almost six days after the accident.	Noon: towing the plane back onto the runway. Gear was damaged but all three tires were rolling.
Henry Hochberg (R) and Andy Czernek cleaning mud and brush from the airframe before it gets hangared. R wing already rinsed, but L wing and gears show mud and brush accumulated.	Right wing after cleanup. Object on wing is cleaning rag.	Left wing: damaged severely, including landing gear.

The Teardown

Because of the prop overspeed, it was assumed that oil pressure had been lost. When oil pressure is lost, the prop governor opens fully and the propellor goes to flat pitch. The question was: where to look first for the cause?

The first step was to check the engine for external damage. There was none. The second step was to drain the oil and check the oil filter, looking for metal. There was nothing beyond a flake or two. Third: look at the screen in the galley entering the prop galley. Several people had bet that we'd find it completely clogged with metal from the engine. However, it too was clean. Only 5 months earlier, this plane had an oil scavenge pump (which pulls oil from the turbocharger) fail. The fourth step was to remove the starter-accessory drive to look for damage. The starter was fine, but the engine-driven alternator's shaft was bent markedly. We were getting closer. As it turned out the accessory drive was not the cause, but the victim. It appears now as if the engine-driven oil pump failed. Though it's a part that rarely fails and is often in good condition at overhaul, this one seized. In doing so, it broke its gear shaft and the oil pump gear had started moving around the accessory case, doing substantial damage. Precise cause will be determined by laboratory analysis at NTSB.

Of course the engine is finished: lack of oil pressure meant lack of lubrication and self-destruction over the final 5 minutes of operation.

The cause of the engine failure in N52202 was a component that rarely fails: the engine's oil pump seizing. When it seized, oil pressure disappeared and the gear-driven shaft broke (part is in two pieces at tip of arrow). The gear itself started moving around the bottom of the sump. Cause of the oil pump seizure is still under investigation by the NTSB.

The oil sump case shows scoring at the head of the arrow from broken oil pump drive gear. This gear also moved into the accessory case, bending the robust shaft of the 252's engine-driven alternator. The inset (lower left) shows the chamber for the oil pump's gear drive, with some fresh scoring here too. (Click on photos for larger images.)

The Disassembly

In mid-January it was time to get the work done. Brian Barth and Josh Schoeneman, of Regal Air, spent a day removing the interior and preparing the disconnection of wing from the fuselage. On Monday, they returned and had the assistance of two of the owners.

It took four hours to complete the job and clean up. First the tail was removed. Then the wing was gingerly moved forward and back to get it out from under the fuselage.

Click photo for a larger image.

Brian Barth, service manager for Regal Air, using a punch to knock out a tail bolt.	Marc Gordon with the tail assembly in its shipping jig.	The fuselage and wing are disconnected now. Though the wing is supported by jacks, Andy Czernek (L) is stabilizing it so that it will not rotate.
Marc Gordon (R) and Andy Czernek (L) supporting the wing.	The wing assembly has been moved down, while the fuselage is jacked as high as it will go.	Brian Barth disconnecting the nose gear so that it can be raised and the wing rolled forward, out from under the fuselage.
With the fuselage and wing separated, it's time to place the shipping jig inside the fuselage (where the wing had been).	Body jig in place.	Josh Schoeneman removing strapping after the wing has been placed in the shipping jig, then rotated to stand on the leading edge.
The three pieces of a Mooney assembly: tail (R), fuselage and wing.	Marc Gordon with the fuselage and wing, both in jigs and ready for shipment.
Revision: 10/28/2010         Comments (and suggestions) to aczernek@comcast.net