bedtime reading ...

.1.1 Departure and transit The crew took-off from their home base at Zaragoza in north-east Spain at approximately 0420 hrs on the morning of the accident but, due to a fault in the directional gyro (DG) system and the possible requirement to fly a Precision Approach Radar approach (PAR) on arrival at RAF Northolt, the crew decided to return to Zaragoza and change aircraft. Learjet 25, EC-CKR, finally departed Zaragoza at 0525 hrs and flew to Palma de Mallorca Airport on the island of Mallorca in the Balearic Islands. At Palma de Mallorca the crew refuelled the aircraft and, after their sole passenger had boarded, they departed at approximately 0645 hrs on an Instrument Flight Rules (IFR) flight plan for their destination airfield, RAF Northolt. The flight to the UK was flown at FL 390 and was uneventful. The aircraft RT callsign for the flight was MIKE ALFA QUEBEC ONE TWO THREE (MAQ 123). Approaching the UK Flight Information Region (FIR) boundary, the crew contacted the London Area and Terminal Control Centre (LATCC) at 0825 hrs and were given routine clearances to position the aircraft for its approach to Northolt. The aircraft's descent continued normally and control was passed to the Biggin sector of LATCC and then via Heathrow Director South and Heathrow Director North to the RAF Northolt Director. Northolt Director positioned the aircraft on a right-hand downwind leg at 3,000 feet for Runway 25 and passed the latest weather report. MAQ123 then confirmed that they wished to carry out a QNH based PAR and were advised that the decision altitude was 330 feet, the field elevation was 124 feet and the procedure involved a mandatory 31/2