Incident Overview
On 16 April 2023 at 1245 UTC, a Piper PA-28-161 (registration G-RAAM) was on a training flight conducting an approach to Runway 25 at Blackbushe Airport, Hampshire. The pilot, a 71-year-old qualified flying instructor with 6,500 total hours (5,000 on type), was on final approach when he suspected the aircraft had struck an obstacle. He initiated a go-around, which was followed by a successful landing. After landing, a twig was found attached to the left landing gear wheel.
Weather and Flight Conditions
The weather at the time of the incident was clear with good visibility. The wind was from 290° at 7 knots and described by the pilot as “gusty.”
Obstacle Limitation Surface (OLS) Information
Runway 25 at Blackbushe is a non-instrument approach runway, less than 1,200 m long and 46 m wide. Civil Aviation Publication (CAP) 168 defines an obstacle limitation surface (OLS) to keep the flight path clear of fixed obstacles. The typical light aircraft approach path to Runway 25 is approximately 150 m (500 ft) above ground level and 2,000 m from the threshold, which is about 70 m (230 ft) above the OLS.
The approach path overflies Yateley Common, described as an extensive heathland with areas of open heather, gorse, birch, and oak woodland.
Tree Survey Findings
Blackbushe Airport conducted tree surveys every two to three years. The 2021 survey identified many trees penetrating the Runway 25 approach OLS. Following a 2017 survey, discussions between the airport and Hampshire County Council (HCC) identified these trees as a hazard and planned removal. HCC carried out extensive works in winter 2017-2018, but the airport did not verify removal or formally re-engage with HCC until after the 2021 survey via incidental conversations.
A further survey in March 2023 revealed 19 trees penetrating the Runway 25 approach OLS. Three trees exceeded the OLS by more than 2 m, two by more than 3 m, and the tallest was 3.74 m above the OLS, located 200 m from the runway threshold. For a light aircraft touching down at the threshold on a typical glide slope, the vertical clearance between the top of that tree and the aircraft would be approximately 1 m. The survey also identified trees penetrating the Runway 07 approach and takeoff OLS, and Runway 25 takeoff OLS. Because the survey used optical instruments from the runway thresholds, some OLS penetrations may have been hidden behind taller trees.
Mitigation and Response
Following the incident, the airport planned to survey the identified trees and begin removal works in autumn 2023, after the ground bird nesting season. In the interim, Blackbushe Airport Safety Action Group published safety information advising pilots to exercise caution on approach to Runway 25.
Hampshire County Council will start the planned removal works in autumn 2023.