What happened
On 22 July 1998, a Piper PA-46, registration N92562, was conducting a private VFR flight from Huddersfield to the Isle of Man. While being vectored by Approach control for a VOR/DME approach to Runway 08, the aircraft was cleared to descend to 1,900 feet. The pilot utilized the autopilot in Vertical Speed mode, intending to maintain a descent rate of 300 feet per minute.
During the descent, the pilot was instructed multiple times to switch radio frequencies to Ronaldsway Tower. While attempting to establish contact with the tower, the aircraft struck rising ground near the Isle of and Man VOR/DME transmitter station at Spanish Head. The impact caused the landing gear to collapse, and the aircraft slid approximately 150 metres across rough terrain. Despite the extensive damage to the airframe, the pilot, a passenger, and a dog escaped without none injuries.
The investigation
Investigators examined the aircraft's avionics and flight instruments following the accident. Testing by the manufacturer confirmed that the avionics equipment was functioning correctly, and the altimeter had been set accurately to the QFE of 1004 mb. However, an interrogation of the Altitude Pre-Select controller's non-volatile memory revealed that the last pre-selected altitude was actually 400 feet, rather than the intended 1,400 feet.
Further analysis of the flight path suggested that the aircraft's descent rate averaged approximately 500 feet per minute over a three-minute period following its descent from 1,900 feet. The pilot also noted that the physical location of the Altitude Pre-Select controller at the bottom of the avionics stack made it difficult to read clearly.
Findings
- The primary cause of the accident was the incorrect altitude pre-selection of 400 feet instead of the required 1,400 feet.
- The pilot's attention was diverted by multiple requests to change radio frequencies during the descent.
- The positioning of the Altitude Pre-Select controller made it difficult for the pilot to monitor the setting.
- The existing VOR/DME approach procedure was found to be susceptible to error.
Safety action
Following the investigation and the review of two similar incidents from earlier that year, the CAA implemented a revised descent procedure in September 1998. The new procedure specified a continuous 3° angle of descent to reduce the potential for misinterpretation or error.