What happened
On 16 November 2003, a Stampe SV4C, registration G-BHFG, was conducting an introductory flight at Gloucestershire Airfield. The weather was clear with good visibility and a light wind from 310º at 7 to 8 knots. During the pre-takeoff engine checks, the instructor noted a significant 300 RPM drop on the right magneto. In an attempt to clear potential oil fouling, the engine was run at a higher power setting with a leaned mixture, which appeared to resolve the issue as the drop decreased to an acceptable level.
After waiting at the holding point for approximately ten minutes, the aircraft took off from Runway 27. As the aircraft began its required noise abatement turn to the right, climbing through 100 feet, the instructor observed that the engine was failing to reach its expected 2,200 RPM, peaking instead at only 1,900 RPM. The instructor maintained a height of 200 feet and decided to return to the airfield for an immediate landing on Runway 18, the nearest available option, despite facing a tailwind.
While the landing on Runway 18 was initially successful, the engine ceased running as the aircraft rolled along the runway. As the speed dropped below 10 knots, the aircraft entered a left-hand ground loop and tipped forward onto its nose, despite the instructor applying full right rudder.
The investigation
Investigators examined the engine performance and the aircraft's handling characteristics during the deceleration phase. It was noted that the Stampe SV4C features a fully castering tailwheel that is not linked to the rudder. The investigation focused on how the combination of a tailwind and the loss of engine power affected directional control.
Findings
- The engine power loss during the climb was likely due to spark plug fouling following the period of idling at the holding point.
- As the aircraft decelerated to a speed matching the tailwind component, the flight controls lost all effectiveness.
- Without engine power or aerodynamic rudder authority, the aircraft lacked inherent directional stability, allowing the wind to initiate the ground loop.
- While differential braking was available, using it to correct the swing carried the risk of causing a nose-over.
- The incident resulted in damage to the propeller, the underside of the nose cowling, and the lower surface of the right wing, with no injuries to the crew.