What happened
On December 12, 1982, an aircraft departed Savoonga for Nome, Alaska. Shortly after takeoff, the pilot detected an issue with the left engine and decided to divert to Gambell, Alaska. During the flight to Gambell, oil pressure gradually decreased. Upon landing at Gambell, the pilot discovered that the oil filler cap was missing and confirmed there was no oil on the dipstick.
A mechanic added seven quarts of oil to the system. To secure the filler neck, a cap from another vehicle was placed over the opening and fastened with duct tape and safety wire. The engine was operationally checked afterward, and no discrepancies were reported at that time. The pilot then attempted to file an Instrument Flight Rules (IFR) flight plan but encountered freezing rain conditions. Deciding against continuing, the pilot turned back toward Gambell.
During the return flight, oil pressure in the left engine dropped again. The pilot shut down the left engine, after which ice began accumulating on the windshield and right windows. The aircraft touched down 25 degrees left of the runway heading and struck a gravel and snow berm beside the runway.
The investigation
Post-acc examination of the left engine revealed that cylinder number one had no compression. A hole was found in the piston, indicating severe mechanical failure likely caused by oil starvation due to the missing cap.
Findings
The primary contributing factor was the loss of the oil filler cap, which led to oil exhaustion and subsequent engine failure. The makeshift repair using a non-standard cap and duct tape failed to maintain proper sealing under flight conditions. Additionally, icing conditions impaired visibility and control during the emergency return.