Accident Cessna 336 N3838U, Sunday 5 August 2001

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Date:	Sunday 5 August 2001
Time:	20:15 LT
Type:	Cessna 336
Owner/operator:	Robert Howard
Registration:	N3838U
MSN:	336-0138
Year of manufacture:	1963
Engine model:	Continental IO-360-A
Fatalities:	Fatalities: 0 / Occupants: 1
Other fatalities:	0
Aircraft damage:	Substantial
Category:	Accident
Location:	Palmdale, CA - United States of America
Phase:	En route
Nature:	Private
Departure airport:	Lancaster-William J Fox Airport, CA (WJF/KWJF)
Destination airport:	El Monte-San Gabriel Valley Airport, CA (EMT/KEMT)
Investigating agency:	NTSB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
The airplane experienced a loss of engine power in the aft engine and collided with a guardrail during an off-airport emergency landing on a highway. The pilot flew the airplane earlier that afternoon with no mechanical discrepancies noted. After takeoff and leveling off at 4,500 feet, the pilot thought he noticed a loss of engine power in both engines because he was unable to maintain altitude. A forced landing was performed on a highway and the airplane went through a guardrail. A post accident examination revealed the primers were left unlocked with the aft engine primer pulled out approximately 1 inch. Black sooty deposits were discovered on the rear engine spark plugs. The primer is as an optional feature to assist in cold weather operations.

Probable Cause: The pilot's inadequate preflight inspection of the primer controls, resulting in excessive fuel flow, spark plug fouling, and loss of engine power in the aft engine.

Accident investigation: