Date: 201207
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: 10
Aircraft: De Havilland Canada Undifferentiated or Other Model
Operator: Personal
Operating under: Part 91
Flight plan: None
Mission: Personal
Flight phase: Climb
Airspace: Class E ZZZ
ATC / advisory: Tower ZZZ
Aircraft component: Powerplant Lubrication System
Component problem: Failed
Reporter organization: Personal
Reporter function: Pilot Flying; Single Pilot
Reporter qualification: Flight Crew Private
Human factors: Situational Awareness; Time Pressure
Anomaly: Aircraft Equipment Problem Critical
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Diverted; Flight Crew Landed in Emergency Condition; Flight Crew Returned To Departure Airport; General Declared Emergency; General Maintenance Action
Contributing factors: Aircraft; Human Factors
Primary problem: Aircraft

Narrative: Aircraft was flown by owner who had checked oil prior to start. I did not think to verify or conduct another key check on that side of the engine - to rotate the pressure filter screen; which I later learned was jammed. En route; oil pressure was 40 PSI/80 degrees F - normal. Time on the ground at en route stop was hurried - attend briefing (also late!); eat; fuel; crank and hold for military launch. Oil press OK; after completing display; departed. En route [I] noticed oil at 30 PSI/80 degrees F; but stable. Landed and re-fueled. Oil pressure OK on start. CTAF blocked by inbound aircraft with stuck mic. After mag check; frequency cleared. Traffic called base-final; so I departed ahead of them (no impediment to their progress). Some fifteen minutes later; approximately 6 miles east and through 5;000 climbing to 5;500 FT; observed oil pressure at 20 PSI and going South at about 10 PSI/minutes temperature still 80 degrees F. With oil pressure passing 15 PSI - 10 PSI; turned back; loaded Tower frequency and declared Mayday. Pressure dropped to zero; I retarded the throttle to full idle and made for the field at 65 KTS. Engine continued to windmill with no perceived irregularity. It became apparent that the headwind (I recall it as 270/10 or 270/12) was not going to allow me to make the field. I had a couple of fields selected; mown and running East-West; when I recalled being told that the engine (a de Havilland Gipsy Major 10) could run on just a quart of oil. I re-applied power to 1800 RPM which allowed me to arrest the descent rate. Oil pressure remained at a solid zero PSI. Once the field was made I cut power and switched-off mags and fuel; and dead-sticked the plane onto runway; just past the numbers; rolling to a stop just short of Taxiway Echo.[People] helped me push the plane across the hold bars and the FBO sent out a truck to tow the plane into the hangar. The prop had continued to turn until the plane had decelerated to about 40 KTS. It could still be easily turned by hand once on the ground. I returned to the aircraft the next day and removed the pressure filter; this being the point at which I discovered it was completely seized (18' of leverage could not turn it). On removal the filter had a significant coating of crud which after being washed-off proved to be ferrous. The filter was cleaned; re-installed and the oil tank topped-up (7 quarts had been thrown out in the 2.7 hours in which the plane had been operated - it has a 12 quart tank). A ground run gave 45 PSI at full static power; 2000 RPM; which reduced to 40 after a few minutes with the temperature approaching 70 degrees F. Consequently it was decided to fly the airplane and bring it up to full operating temperature above the field and; if all was well; to continue to OSH with the SR22 in which I'd arrived as chase plane. After 15 minutes overhead at 5;500 FT oil pressure was 38 PSI/80 degrees F and; joined by the SR22; we headed for OSH; taking careful note of all airfields; public and private. Oil pressure remained constant and arrival at OSH was uneventful.Subsequent discussion with the owner revealed that the plane had flown only 300 hours since overhaul 18 (eighteen) years ago. Prior to a hop from the owner's strip; the aircraft had not been flown since February. Four A&P engineers I consulted afterwards independently questioned the wisdom of making a flight after finding metal in the oil. To my mind; with pressure holding; it was a calculated risk. Return to base had been considered but continuing to OSH was considered favorable because of its shorter duration and the availability of experts on the field who had knowledge of the vintage engine. Following the advice of the A&P's the airplane was left on the field and arrangements are in hand to have the engine removed and the source of the problem investigated. A full overhaul is anticipated. When taking over an airplane; especially one with which one is unfamiliar; perform a thorough pre-flight check yourself and ignore any pressure to get anywhere by a specific time. Trust but verify. If key items such as a screen cleaner on a filter will not move; investigate and solve before flying. If there's metal in the engine; quit flying it! There was no flight plan; no GPS; no flight following was requested but Center was monitored as the flight progressed and a [flight tracker] was active. Pilotage is alive and well.




Synopsis: DHC Chipmunk pilot describes loss of oil pressure on the third leg of a flight to OSH. The engine continues to produce power and the reporter is able to return to the departure airport. It is discovered that the oil filter screen is completely coated with metal particles. The filter is cleaned and reinstalled; the oil topped off; and the engine run up. When all appears satisfactory the reporter takes off and climbs over the field before continuing on to OSH.