AAIB Report: Piper PA-28-151 (G-BOTI), Near controlled flight into terrain, 22 October 2022
While on approach into Exeter Airport on 22 October 2022, the pilot of a Piper PA-28-151 (G-BOTI) lost situation awareness and began the final descent early. The aircraft descended to 400 ft from terrain before climbing.
On the final approach to Exeter Airport, the pilot lost situation awareness with respect to his position relative to the runway and ILS (instrument landing system) descent point. The aircraft began its descent early and descended to 400 ft from terrain before ATC instructed the pilot to climb. It is possible there was a malfunction of the glideslope deviation indicator on the course deviation indicator (CDI), but the pilot’s awareness would have been improved by referencing the distance measuring equipment (DME) to confirm his position relative to the descent point.
The approach controller noticed the early descent three minutes after the aircraft departed the cleared level and instructed the pilot to climb. The subsequent approach was flown using the localiser and without vertical guidance to a successful landing. The CDI had been reported as unserviceable prior to scheduled maintenance, which had been completed on the day of the flight, although no fault was found with the glideslope indicator.
The investigation found that the approach controller did not use the correct phraseology – this would have made the approach clearance conditional on the pilot confirming his distance from the runway threshold using DME. The pilot would in any case have improved his situation awareness and probably prevented this serious incident by checking the DME range at the descent point. A DME check is an important part of procedures such as this, because it provides an independent means of confirming that it is safe to descend.