AAIB Bulletin: 6/2006 I-BIKE EW/C2005/06/03 INCIDENT Aircraft Type and Registration: Airbus A320-200, I-BIKE No & Type of Engines: 2 CFM-56 turbofan engines Year of Manufacture: 1999 Date & Time (UTC): 25 June 2005 at 0740 hrs Location: On approach to Runway 09L at London Heathrow Airport Type of Flight: Public Transport (Passenger) Persons on Board: Crew - 6 Passengers - 98 Injuries: Crew - None Passengers - None Nature of Damage: Failure of No 1 and 3 ADIRUs Commander’s Licence: Airline Transport Pilot’s Licence Commander’s Age: 41 years Commander’s Flying Experience: 8,300 hours (of which 1,300 were on type) Last 90 days - 130 hours Last 28 days - 50 hours Information Source: AAIB Field Investigation Synopsis The aircraft had departed on a scheduled passenger whilst attempting to diagnose the problem, contrary flight from Milan to London Heathrow Airport, with to prescribed procedures. As a result, additional data an unserviceable No 3 Air Data Inertial Reference Unit was lost from the commander’s electronic instrument (ADIRU). On final approach to Runway 09L at London displays, the nosewheel steering became inoperative and Heathrow, in Instrument Meteorological Conditions it became necessary to lower the landing gear by gravity (IMC), the Inertial Reference (IR) part of the No 1 extension. The aircraft landed safely. ADIRU failed, depriving the commander (the pilot History of the flight flying) of much of the information on his Primary Flight and Navigation Displays. ATC required the aircraft to The history of the flight is derived from multiple sources, go-around from a height of 200 ft on short final approach including data from both the Flight Data Recorder due to another aircraft still occupying the runway. The (FDR) and Cockpit Voice Data Recorder (CVR). co-pilot, who had been handed control, performed the go‑around and the aircraft was radar vectored for a second The flight departed from Milan Airport at 0547 hrs on a approach. The crew then turned off the No 1 ADIRU scheduled flight to London Heathrow Airport (LHR) with © Crown copyright 2006 AAIB Bulletin: 6/2006 I-BIKE EW/C2005/06/03 the commander as the Pilot Flying (PF). The previous co‑pilot, whose PFD and ND were functioning normally, day, the No 3 ADIRU was found to be unserviceable and the ILS approach was continued. and had been turned off; the Minimum Equipment List (MEL) allowed the aircraft to depart in this condition, as At about 0724 hrs, the flap lever was set to position both the Nos 1 and 2 ADIRUs were serviceable. During three. Shortly after this time the aircraft started to the flight, as a precautionary measure, the commander deviate from the glideslope and localiser. The aircraft and co-pilot reviewed the Flight Manual Abnormal altitude continued decreasing and, by about 300 ft radio Procedures for the actions to be taken in the event of a altitude and when at an airspeed of 130 kt, the aircraft second ADIRU becoming unserviceable. had deviated some 1.3 ‘dots’ below the glideslope. Almost coincident with this, the CVR recorded an Following an uneventful transit, the aircraft was given EGPWS “glideslope” warning (see Figure 1 Point B). radar vectors and became fully established on the ILS The deviation below the glideslope continued to approach to Runway 09L at LHR. Two stages of flap increase and a second EGPWS “glideslope” warning were selected and, at 1,820 ft (QNH), the landing gear was recorded by the time the aircraft was at some was lowered. Some 16 seconds later, just as the landing 1.84 ‘dots’ below the glideslope. gear locked down, the Inertial Reference (IR) part of the No 1 ADIRU failed and a ‘NAV IR 1 FAULT’ message As the crew continued their approach, ATC advised that appeared on the aircraft’s Electronic Centralised Aircraft they would receive a late clearance to land. When the Monitor (ECAM). The autopilot and
