On 21 January 2010, a Mystere Falcon 50 being operated by TAG Aviation on a positioning flight from Biggin Hill to London City in day Visual Meteorological Conditions (VMC) began a descent at a high rate below its cleared altitude of 2000 ft amsl because the aircraft commander believed, on the basis of external visual cues, that the aircraft was on a final approach track for Runway 27 at destination when in fact it was downwind for Runway 09. After an alert from ATC as the aircraft passed 900 ft agl at a rate of descent of approximately 2200 fpm, recovery to a normal landing on Runway 09 was achieved.
An investigation was carried out by the UK AAIB. It was found that the flight crew was two type-qualified instructor Captains of whom only one had been to London City previously. It was decided that he would be aircraft commander but that the other pilot would act as PF and occupy the left hand seat so as to become familiar with the necessary steep approach procedure at London City.
The event was described as follows:
“The commander was visual with the ground and could see two bright lights ahead, which he believed were the touchdown zone lights for Runway 27 at LCY. The DME indicated that the aircraft was about 4 nm from the airport. At about this time another aircraft on the frequency was instructed to adjust its heading slightly to establish on the localizer and subsequently to descend with the glideslope. Shortly afterwards (the incident aircraft) was given a further slight heading change.
The commander mistakenly believed that the aircraft was landing on Runway 27 and that it was nearing the final approach point, although he couldn’t discern the runway itself. He was concerned that it was becoming too high to conduct an approach and therefore instructed the co-pilot to commence a descent.
The spoilers and full flap were both deployed. A steady descent rate of approximately 2,200 ft/min was established until, on passing 1,100 ft amsl (approximately 900 ft agl), ATC instructed the aircraft to climb. The descent rate was reduced quickly, the aircraft descending approximately 250 ft before achieving a climb. The aircraft was now approximately 4 nm south west of the runway on a downwind leg.”
The aircraft was fitted with an Terrain Avoidance and Warning System (TAWS) and this was removed, downloaded and tested and found to have been fully operational during the event. No crew warnings were generated during the incident but testing and analysis has shown that this was in accordance with its design given that the nearest the aircraft actually got to terrain after ATC alerted the crew to their position was approximately 650 ft agl. Manufacturer simulations showed that, had the aircraft carried on descending at 2,200 fpm, “Sink Rate” followed by “Pull Up” aural warnings would have been activated on passing through a radio height of 422 ft. It was calculated that assuming a similar recovery profile to that flown, the crew would have had just 3.4 seconds after hearing the “PULL UP” to successfully initiate the recovery.
The Investigation noted that even when ATC instructed a climb back to 2200ft, both flight crew had entirely lost positional awareness and remained initially confused:
“When ATC instructed the aircraft to climb back to its cleared altitude, the spoilers and landing gear (remained) deployed as the crew queried the instruction and sought confirmation that a go-around should be initiated”.
The Investigation noted that the operator had since made changes to the minimum requirements for crews operating into London City and had also changed related training procedures and published information to crews highlighting the incident and the lessons learned.
No Safety Recommendations were sustained by the findings of the Investigation.
The Final Report was issued on 9 September 2010 and may be seen in full at SKYbrary bookshelf: AAIB Bulletin: 9/2010 EW/C2010/01/06