What happened
On 10 August 2001, a Europa XS, registration G-IOWE, was conducting a private flight near Wolverhampton. The aircraft was carrying a pilot and a passenger, the latter of whom was an experienced instructor acting as a safety pilot. Following a standard pre-flight sequence and successful engine power checks, the aircraft commenced its takeoff roll.
As the aircraft reached approximately 100 feet above ground level, the engine began to vibrate and surge, experiencing a near-total loss of power. The passenger took control of the aircraft and executed a 40-degree turn to maneuver toward a suitable landing site. The crew performed a forced landing in a short, uphill cornfield. The engine ceased running upon touchdown, but the aircraft sustained no damage and there were no injuries to the occupants.
The investigation
Investigators examined the aircraft's fuel system, including lines, filters, and carburetor float chambers, but found no initial faults. However, a subsequent fuel flow check identified a restriction within the fuel flow transducer, which was positioned between the fuel filter and the carburetors.
Upon laboratory examination of the German-manufactured transducer, the AAIB discovered that the internal flow chamber was significantly restricted. The internal inlet channel, which tapered to a width of just 0.30mm at its outlet, was partially obstructed by unidentified debris. Furthermore, the magnets on the central sensor were heavily coated with ferrous particles. Testing confirmed that the faulty unit allowed only one-third of the fuel flow compared to a new, identical unit. The investigation could not determine how debris, particularly metallic particles, bypassed the fuel filter to enter the sealed transducer unit.
Findings
- The engine power loss was caused by a blockage within the fuel flow transducer.
- The internal geometry of the transducer's flow channel was highly susceptible to restriction by small particles.
- Ferrous debris had accumulated on the internal sensor magnets.
- The transducer design lacked a bypass mechanism to maintain fuel supply in the event of a blockage.
Safety action
Following the incident, the aircraft owner elected to remove the fuel flow meter system from the aircraft. Additionally, the UK supplier of the system began developing a bypass modification for the original design. The AAIB issued Recommendation 2002-38 to the Popular Flying Association, stating that fuel flow transducers on 'Permit to Fly' aircraft should be designed to be resistant to particle blockage or include an automatic bypass mechanism.