What aircraft was involved and where did it happen?

The accident on null involved a aircraft, registration EI-DGT, at IE.

What was the probable cause of the accident?

The nose gear steering tube fractured due to excessive lateral loads caused by a landing in a strong crosswind while using significant rudder input.

Nose gear failure during landing in Co. Longford

A Lambada UFM-11 ultralight aircraft sustained damage to its nose gear and propeller after a heavy landing in a crosswind at Abbeyshrule.

What happened

On 5 March 2005, a Lambada UFM-11 aircraft, registration EI-DGT, was conducting a private flight from Galway Airport to Abbeyshrule, Co. Longford. Upon arrival at approximately 12:30 UTC, the pilot prepared to land on Runway 28. Due to the presence of a significant crosswind, the pilot opted to perform a landing without the use of flaps and utilized substantial rudder input to maintain directional control.

During the landing roll, approximately 140 meters from the runway threshold, the aircraft experienced a slight ballooning effect after the initial touchdown. As the pilot attempted to lower the nose at a slow forward speed, the nose gear assembly failed. The impact caused the nose wheel steering tube to bend, resulting in the nose wheel spat dragging along the runway surface. Additionally, the tips of the wooden propeller were damaged upon contact with the tarmac. There were no injuries to the pilot during the event.

The investigation

Investigators examined the structural integrity of the nose wheel assembly, which utilizes a fork unit similar to a bicycle's design. The steering tube is reinforced with an internal sleeve and a stiffening tube held by adhesive. A metallurgical analysis of the fractured steering tube revealed that the failure was a single-event overload, with no evidence of prior fatigue, corrosion, or pre-existing defects. However, the examination did note a slight lack of weld penetration at the edges of the plug welds.

Further analysis determined that the aircraft's rudder control is linked to the nose wheel steering, which automatically turns the wheel into the wind during touchdown. In this specific instance, the wind conditions—340 degrees at 14 to 20 knots—meant that the rudder input required to counteract the crosswind simultaneously increased the lateral stresses applied to the steering tube.

Findings

The pilot underestimated the impact of the wind gust factor during the landing.
The aircraft touched down in a wing-down condition without flaps, leading to abnormal loads on the nose wheel steering tube.
The structural design of the steering tube, specifically the area where the internal sleeve and stiffening tube meet, acted as a designed weak point to protect the aircraft's composite skin from major damage during an overload.
The landing stresses caused the steering tube to fracture at this specific location.