What happened
On 26 September 2009, a Piper PA-28-140 Cherokee, registration G-BRWO, was performing a private flight approach to Runway 26 at Humbers and Airport. Shortly after the aircraft crossed the runway threshold, the pilot attempted to flare for landing. During this maneuver, the aircraft experienced an uncontrollable roll to the right, causing the right wing to strike the runway surface. The impact caused the wing structure to fail and the aircraft to come to rest inverted near the fire training facility.
The pilot, who sustained one serious injury, managed to force open the jammed cockpit door and escape the wreckage before emergency services arrived. There was no fire at the scene.
The investigation
Investigators examined air traffic control transcripts and reports from the airport operator and emergency services. The investigation revealed that a Sikorsky S76 helicopter had landed on the runway just prior to the arrival of G-BRWO. Due to the positioning of the airport's fire training facility, the air traffic controller was unable to directly observe the accident site from the tower, which delayed the confirmation of the incident by approximately three minutes.
During the initial response, the airfield's fire category remained at Category 6 and was not downgraded despite the deployment of the Airport Fire and Rescue Service (AFRS). Furthermore, aircraft movements continued at the airport while the emergency services were attending to the crash site.
Findings
- The uncontrolled right roll was likely caused by the Piper PA-28-140 Cherokee flying through the wake turbulence generated by the preceding Sikorsky S76.
- Although both aircraft were categorized as 'Light' under existing separation standards, the intense vortex system produced by a helicopter during its transition to a hover can be more powerful than those from fixed-wing aircraft of similar weight.
- Wind conditions at the time were unlikely to have allowed the wake vortices to dissipate before the arrival of the Cherokee.
Safety action
Following the accident, the airport operator reviewed its response procedures and installed a CCTV camera to allow controllers to monitor the runway threshold. The Aerodrome Manual was also amended to ensure that aircraft movements are suspended and the fire category is reduced to zero immediately upon the deployment of the AFRS.