The private pilot, who was the owner and builder of the experimental amateur-built Harmon Rocket, and a commercial pilot departed on a local flight and performed three touch-and-go practice takeoffs and landings.
During the fourth takeoff, after reaching about 300′ above the ground, the engine experienced a total loss of power. The airplane made a right turn and crashed about 1,650′ from the end of the runway at Corona, California, resulting in one fatality and one serious injury.
The single-engine airplane was built about seven years before the accident, at which time the private pilot installed a newly-overhauled engine. The airplane had accrued about 100 total hours of time in service.
During post-accident examination, the engine would not start, but was found to operate normally when a different fuel servo was installed.
The Bendix fuel servo, manufactured in 1977, was designed to meter fuel in relation to the volume of air being consumed by the engine. The metering is accomplished by air and fuel diaphragms inside the unit that are connected by a valve stem that has a regulator ball affixed at its end. A pressure differential across the air diaphragm results in the regulator ball unseating and providing the engine with more fuel.
Complete disassembly of the fuel servo revealed that the regulator stem was separated from the regulator ball, which would prevent the ball from being able to unseat and would subsequently block fuel from entering the engine, resulting in fuel starvation.
The servo manufacturer stated that the servo’s internal components appeared to be original, although those components were required to be replaced every 12 years.
There were no maintenance records pertaining to the servo, but its appearance indicated it was likely never overhauled. The maintenance entry for the engine overhaul noted that the airplane was equipped with a “serviceable fuel servo,” which, according to a representative from the maintenance facility that performed the overhaul, was likely determined by an engine test run.
Because the airframe and engine were classified as amateur-built experimental, the overhaul criteria are not required for airworthiness, however, it is likely that the failure of the regulator valve stem and ball would not have occurred if the servo components had been replaced in accordance with manufacturer specifications.
Probable cause: A total loss of engine power during takeoff due to fuel starvation as a result of a failure of internal components of the fuel servo.
NTSB Identification: WPR17LA054
This January 2017 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
Mark Maurer says
JimH – Thanks for the more informative link, it was an interesting read. Maybe future articles can include an NTSB link to expand accident info and offer a “lesson learned” to those pilots still among us.
JimH in CA says
You can copy the NTSB ID and paste it into the docket search,
Then click on the ‘find’ button on the top-right of the form.
There is usually a number of lines items. I just copied the photo file link.
In most cases there is a lot of good info that pilots can apply.
I fly a 1961 Cessna, so I’m very interested in reports on old parts failing.
JimH in CA says
This is another case where old parts, 1977, failed and cause the engine to stop.
The folks who overhauled this engine failed to observe the fuel servo manufacturer’s overhaul specifications, or even inspect the part.
But, since this was an experimental engine, all the TBOs are not required to be followed.
The NTSB docket is interesting to read along with the photos.