Loss of elevator control leads to inverted crash of Pitts S-1C

Casualties unknown • Popham Airfield, GB

A test flight following an extensive rebuild ended in a heavy landing and inversion at Popham Airfield after a control linkage disconnected.

What happened

On 27 March 2022, a Pitts S-1C (registration G-BTOO) was conducting a test flight at Popham Airfield to verify its airworthiness following a major rebuild and modification. The flight was intended to confirm the aircraft's handling characteristics after the installation of new wings and structural changes.

While cruising at 2,500 feet, the pilot noticed unusual play in the control column's pitch axis. Upon investigation, the pilot discovered that the elevator was no longer responding to the control column. Although the pilot could still use the trim and engine power to influence the aircraft's pitch, the loss of direct elevator authority created a high-stress situation. The pilot declared a MAYDAY and attempted to return to the airfield using unbalanced turns to manage the descent.

During the final stages of the approach to Runway 03, the aircraft encountered turbulence, causing a sudden nose-down attitude. The pilot reduced throttle in response, but the aircraft struck the ground heavily on the forward fuselage and came to rest inverted. The pilot sustained one serious injury involving a severe head laceration.

The investigation

Investigators examined the elevator control system and discovered that a pushrod had disconnected from a bellcrank. The bolt used to secure the joint was present, but the required split pin and castellated nut were missing. It is believed the nut loosened and detached because the split pin was not installed.

Further examination of the cockpit revealed that the instrument panel coaming lacked the required padding. This unprotected sharp edge caused the pilot's head injury when they were thrown forward during the impact. The investigation also reviewed the aircraft's rebuild documentation, noting that while the work was comprehensive, the records lacked the specific detail and photographic evidence recommended by the Light Aircraft Association (LAA).

Findings

  • The loss of elevator control was caused by a disconnected pivot joint in the control linkage, likely due to the absence of a split pin to secure the bolt.
  • The pilot's head injury was exacerbated by the lack of padding on a sharp edge of the cockpit coaming.
  • There were inconsistencies in the LAA technical leaflets regarding the authorization of duplicate inspections.
  • The rebuild documentation did not fully adhere to the level of detail suggested in LAA guidance.

Probable cause

The primary cause of the accident was the disconnection of the elevator pushrod from the bellcrank due to a missing split pin, which resulted in the loss of pitch control authority. This was compounded by the pilot's inability to counter a sudden nose-down attitude during the final approach.

Frequently asked questions

What happened in the 2022-03-27 Pitts S-1C (Modified) accident near Popham Airfield, GB?

A test flight following an extensive rebuild ended in a heavy landing and inversion at Popham Airfield after a control linkage disconnected.

What aircraft was involved and where did it happen?

The accident on 2022-03-27 involved a Pitts S-1C (Modified), registration G-BTOO , at Popham Airfield, GB.

What was the probable cause of the accident?

The primary cause of the accident was the disconnection of the elevator pushrod from the bellcrank due to a missing split pin, which resulted in the loss of pitch control authority. This was compounded by the pilot's inability to counter a sudden nose-down attitude during the final approach.

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