What happened
On 22 January 1999, a BAe 125-800A, registration N453TM, was conducting a private flight from Blackpool to Farnborough. The flight, which included two crew members and three passengers, encountered heavy fog upon arrival at Farnborough Airport. At the time of the incident, the Runway Visual Range (RVR) was recorded at only 200 metres, significantly lower than the 650-metre minimum required for the Precision Approach Radar (PAR) procedure being used.
During the descent, the commander expressed uncertainty regarding UK approach regulations to the air traffic controller. Despite this, the aircraft was cleared to land. As the aircraft descended through the decision altitude, the co-pilot reported seeing lights, prompting the commander to continue the approach. However, the aircraft drifted left of the centreline. The aircraft subsequently touched down on the intersection of taxiways M and N rather than the runway surface. The main wheels then transitioned onto the grass, causing the aircraft to come to a stop. While there were no fatalities or injuries, the aircraft sustained damage to the right trailing edge flap, and both engines required inspection due to mud ingestion.
The investigation
The AAIB investigation focused on the legality of the approach under UK law and the communication between the flight crew and air traffic control. The investigators examined the 'Approach Ban' legislation, which prohibits aircraft from descending below 1,000 feet at a notified instrument approach if the RVR is below the specified minimum. The investigation also reviewed the radio communications between the commander and the London Area and Terminal Control Centre (LATCC) and Farnborough Radar controllers.
Findings
- The commander was aware of the low visibility but was uncertain of the specific UK 'Approach Ban' regulations, having been trained under US Federal Aviation Regulations.
- The air traffic controller did not interpret the pilot's non-standard phraseology regarding regulatory uncertainty as a request for legal guidance.
- The aircraft descended below 1,000 feet in visibility that was below the legal minimum for the approach.
- The controller confirmed the approach was acceptable based on the operator's minima, rather than the UK's regulatory requirements.
- At the moment of decision altitude, the co-pilot experienced a momentary lapse in monitoring the approach lights, leading to a delay in communicating the aircraft's position.