N7094T accident

NTSB ERA21LA075 · 2020-12-11 · Durham, NC · near 8NC8

Docket — crew, injuries and powerplant

Summary

The pilot reported that about 20 minutes into the flight, at an altitude about 500 ft above ground level, the engine started losing power. The pilot noted no anomalies on the engine monitoring system, but his attempts to increase engine power were unsuccessful, and he chose to conduct a forced landing in a lake. During the landing flare, the wheels contacted the water surface and the airplane nosed over and came to rest inverted and submerged. Examination of the airplane following recovery from the lake revealed that the fuel primer bulb was missing a spring on the fuel inlet check valve, which prevented the check ball from seating properly. This likely blocked the incoming fuel and thereby resulted in fuel starvation and the total loss of engine power.

Full narrative

On December 11, 2020, about 1300 eastern daylight time, a Kolb Firestar II, N7094T, was substantially damaged when it was involved in an accident near Durham, North Carolina. The pilot sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

The pilot reported that, about 20 minutes into the flight, the engine started losing power. The airplane was about 500 ft above ground level; the engine monitoring system did not indicate an engine problem. The pilot’s attempts to increase engine power were unsuccessful, and the airplane continued to lose altitude.

The pilot decided to conduct a forced landing on a lake. During the landing flare, the wheels contacted the water surface and the airplane immediately flipped forward and came to rest upside down and partially submerged. The pilot egressed and swam to the surface, where he was rescued by an individual on a personal watercraft.

The airplane sustained substantial damage to the wings and fuselage. The tail separated about 2 ft aft of the fuel tank and the leading outboard edges of the wings were crushed and torn open. The airplane remained submerged until the following day, when it was recovered and transported to the owner’s hangar for further examination. The owner performed the examination and discovered that the fuel primer bulb was missing the fuel input primer spring. (see figure 1.)

Figure 1 - Primer bulb illustration.   The owner’s observation of the check “ball” valve and lack of spring tension kept the ball from seating properly during normal operations. The owner reported that the system should ideally be installed in a vertical position, but on the accident airplane, it was installed horizontally (see figure 2). Without the spring, gravity would not be adequate to keep the check ball from migrating inside the primer inlet fuel line.

Probable cause

A total loss of engine power due to fuel starvation as the result of a degraded fuel primer check valve. The National Transportation Safety Board determined the probable cause of this accident.

Circumstances

Event type
Accident
Highest injury
None
Weather conditions
Visual Meteorological Cond
Light condition
Day
Ceiling (ft)
0
Visibility (sm)
10
Wind direction
0
Wind speed (kt)
3
Temperature (F)
64
Nearest airport
Lake Ridge Aero Park Airport
Distance from field
3.0
Airport elevation
309

Aircraft

RegistrationMakeModelDamageFAR part
N7094T — — SUBS 091

Sequence of events

#OccurrencePhase
3 Enroute Fuel starvation defining Climb
4 Enroute Off-field or emergency landing Climb

Findings

Finding
Aircraft-Aircraft systems-Fuel system-Fuel transfer valve-Damaged/degraded cause
Aircraft-Aircraft systems-Fuel system-Fuel transfer valve-Malfunction cause