Amateur-built VANS RV 9A N699RV accident near Newark, Illinois

Probable cause

The pilot's failure to properly assemble the fuel pump, which resulted in the loss of fuel pressure and the subsequent partial loss of engine power.

NTSB analysis

The pilot was conducting a cross-country flight in an experimental airplane when he observed the fuel pressure fluctuating, and the engine began to surge. The pilot turned on the backup fuel pump but the engine continued to surge, so he diverted to a nearby airport. The pilot stated that he had difficulty visually acquiring the airport and was losing altitude while circling over the airport. He performed an "S" turn but was still too high. He was running out of runway below him, so he performed a "hard slip" to lose altitude. The airplane stalled 10-15 ft above the runway, hit the ground, and slid about 30 ft before stopping.

The primary fuel pump had failed 4 days before the accident. The pilot replaced the fuel pump with a new unit that required partial assembly. He noted during assembly that there was not an O-ring where the lower fitting attached but that the mating surfaces were different between the two pumps and he had believed one was not required. The instructions with the new pump did not address the installation of an O-ring at the fitting.

After the accident, the pilot reexamined the box the new fuel pump came in and found an O-ring for the lower fitting. Without the O-ring installed, the fuel system was not able to maintain the fuel pressure necessary to ensure smooth engine operation and resulted in the partial loss of engine power. The pilot stated the accident resulted from this maintenance issue.

Text from the NTSB. Open the NTSB docket for CEN16LA387 for the full record.