Initial Flight
Before departing from Alpine Airport, the pilot had the main and auxiliary fuel tanks filled and conducted an abbreviated preflight inspection. The pilot did not perform an engine run-up prior to takeoff. According to the pilot, while the airplane was climbing through 100 feet above ground level, the left engine began to surge. The pilot reported that he knew the airplane would not be able to climb at field elevation with one engine inoperative.
Engine Issues and Pilot Response
In response to the surging, the pilot switched the left engine's boost pump from low to high. However, the left engine continued to surge as the airplane lost altitude. The pilot then initiated a forced landing with the landing gear and flaps retracted and the left propeller unfeathered.
Forced Landing and Post-Accident Findings
The airplane impacted the ground left wing tip first, and a fire erupted, which damaged the left wing and left side of the fuselage. Examination of the left engine's spark plugs revealed they were covered with thick black soot. The left engine's magnetos were rotated using an electric hand-held drill; the left magneto did not produce any spark, and the right magneto produced a spark in three of its six distributor cap posts. The left magneto's primary winding resistance and capacitor leakage were found to be beyond the manufacturer's specified limits. Internal components of both magnetos were covered in a dark oil and debris.
Weight and Performance
The maximum takeoff weight for the accident airplane was 6,350 pounds; however, the takeoff weight at the time of the accident was calculated to be 6,509 pounds. The aircraft's single engine performance charts indicated that the airplane would obtain a 29 feet per minute climb at maximum gross weight with the inoperative engine feathered.
Pilot Operating Handbook Guidance
The pilot operating handbook's supplement section indicated that the auxiliary fuel pump should only be used when the engine-driven fuel pump failed. A caution statement in bold print read: "If the auxiliary fuel pump switches are placed in the HIGH position with the engine-driven fuel pump(s) operating normally, total loss of engine power may occur."
Probable Cause (Official Findings)
The probable cause was the pilot's improper use of the emergency fuel boost pump, which resulted in excessive fuel flow to the engine and subsequent total loss of left engine power. Factor's were the high density altitude, the pilot exceeding the airplane's weight and balance, the partial loss of left engine power as a result of the faulty magnetos, and the pilot's inadequate preflight inspection by not performing an engine run-up.