Mechanical failure causes sudden roll during training flight at Cambridge

Casualties unknown • Cambridge Airport, GB

A Dyn Aero MCR-01 Banbi experienced a sharp right-hand roll during a training flight at Cambridge Airport due to a stripped flap mechanism.

What happened

On 10 October 2001, a Dyn Aero MCR-01 Banbi, registration G-PGAC, was conducting a short training flight at Cambridge Airport. During the approach, the pilot had established a normal overhead join at 2,000 feet and selected 10 degrees of flap. As the aircraft descended to approximately 450 feet, the pilot selected additional flap, at which point the aircraft experienced a sudden jolt and rolled sharply to the right.

Despite applying full left stick, the pilot could not arrest the bank, which reached approximately 65 degrees. Attempts to use increased power to climb away only worsened the bank angle, forcing the pilot to reduce power and stabilize the roll at roughly 75 degrees. Fearing a stall or spin, the pilot maintained an airspeed of at least 80 knots while managing a descent that dropped to 100 feet above ground level. After performing a 180-degree turn, the pilot found that reducing speed to 75 knots helped reduce the bank angle. The aircraft eventually cleared a hedge and a low cable before landing smoothly on the grass beside the runway. There were no injuries and no damage to the aircraft.

The investigation

An inspection of the aircraft by a Popular Flying Association (PFA) inspector revealed that the flapperons were operated by an electrically driven mechanism using steel screw jacks. These jacks traveled within aluminium 'chariots' along guide tubes, with the threads of the steel jacks running directly against the aluminium without any bushing.

Upon examination, it was discovered that the aluminium threads within the right-hand chariot had stripped. This mechanical failure allowed the flap to retract under aerodynamic loads, creating an asymmetric configuration that induced the intense right-hand roll.

Findings

  • The sudden roll was caused by the stripping of aluminium threads in the right-hand flap mechanism chariot.
  • This failure allowed the right flapperon to retract under air loads while the left remained extended.
  • The pilot's decision to reduce speed helped stabilize the aircraft's flight path during the emergency landing.

Probable cause

The primary cause of the incident was the mechanical failure of the right-hand flapperon mechanism, specifically the stripping of the aluminium threads in the chariot, which caused an asymmetric flap configuration under aerodynamic loads.

Frequently asked questions

What happened in the 2001-10-10 MCR-01 accident near Cambridge Airport, GB?

A Dyn Aero MCR-01 Banbi experienced a sharp right-hand roll during a training flight at Cambridge Airport due to a stripped flap mechanism.

What aircraft was involved and where did it happen?

The accident on 2001-10-10 involved a MCR-01, registration G-PGAC, at Cambridge Airport, GB.

What was the probable cause of the accident?

The primary cause of the incident was the mechanical failure of the right-hand flapperon mechanism, specifically the stripping of the aluminium threads in the chariot, which caused an asymmetric flap configuration under aerodynamic loads.

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