ASN Wikibase Occurrence # 192782
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Narrative:The aircraft was operating a commercial air transport flight from Manchester to Inverness. It departed at 1630 hrs, and the initial part of the flight was described by the crew as uneventful.
|Date:||Friday 6 November 2015|
|Fatalities:||Fatalities: 0 / Occupants: 32|
|Aircraft damage:|| None|
|Location:||Manchester Airport (MAN/EGCC) -
|Phase:|| Take off|
|Nature:||Passenger - Scheduled|
|Departure airport:||Manchester Airport (MAN)|
|Destination airport:||Inverness Airport (INV)|
|Investigating agency: ||AAIB|
|Confidence Rating:|| Accident investigation report completed and information captured|
The autopilot was engaged during the climb.
The aircraft levelled at FL090 and accelerated from 180 kt to 240 kt on a radar heading and in VMC. The pilot recalled that shortly afterwards the primary flight display (PFD) indicated that the aircraft had a nose-up attitude of 7° and 10° of roll to the left, an unusual attitude for straight and level flight. He also felt that the aircraft was not in balance. The PF alerted the pilot monitoring (PM) and together they cross-checked their instruments. A yellow ‘r’ mistrim indication then illuminated on the PFD, indicating there were untrimmed forces in the aileron system.
The PF decided to disconnect the autopilot, bracing the controls for the jolt he expected when doing so with an aileron mistrim. The jolt was more pronounced than usual and he had difficulty maintaining straight and level flight, finding that the aileron controls felt "sloppy" and unresponsive. He reduced airspeed to below 200 KIAS, and the PM viewed the Flight Control System (FCS) synoptic page on the Secondary EICAS Display (SED). The pilots recalled that the FCS diagram indicated both of the aircraft’s ailerons were deflected upwards, with the left aileron up 8° and the right aileron up 5°, and that whilst they were looking at the display both aileron depictions briefly deflected upwards to 17°.
The pilots decided that there was a problem with the aircraft’s aileron system, so the PM consulted the malfunction checklist kept in the cockpit. He read through the two aileron malfunction checklists it contained: ‘Aileron system jammed’ and ‘Aileron system open failure’. Neither seemed to fit the symptoms, but the pilots remained under the impression that something was wrong with the ailerons, and as the controls were not jammed they decided to action the ‘Aileron system open failure’ checklist. The pilots did not look outside the window to check the actual position of the ailerons, which can be seen from the cockpit if the ailerons are deflected up, and relied upon the SED synoptic page for indications of their deflection.
After pulling the roll handle (as directed by the checklist, to separate the left and right aileron control systems), both pilots flew the aircraft in turn to establish who had the most control. They determined that the left control wheel was more effective than the right, and so the commander remained as the PF. Initially a PAN call was transmitted to ATC but this was subsequently upgraded to a MAYDAY once it was clear that a landing would have to be made "with compromised flight controls."
The pilots decided to return to Manchester and informed ATC that the aircraft had a reduced turning capability. The cabin crew were briefed and the PM set the navigation system for an ILS approach to runway 23R at Manchester. Passing 4,000 ft, the PF requested the selection of Flap 15 in order to check controllability. When the flaps had extended to 7° the PF observed that the aircraft was more difficult to control, and when extended to 13° he requested they be reselected back up. The pilots then planned for a Flap 0 landing and reset the Vref of 152 kt accordingly. At approximately 200 ft agl on the approach the TAWS ‘too low terrain’ and ‘glideslope’ cautions sounded. The PF could see the runway and the PAPIs clearly, and the aircraft landed safely.
The investigation established that there had been two separate faults on the aircraft: one involved the rudder trim position recorded on the QAR and the second the output from the left aileron position transducer.
The first fault, with the rudder position, involved a restriction which prevented the rudder pedals from moving. The restriction ceased when the pilot disconnected the autopilot and flew the aircraft manually, and the investigation was unable to determine the cause of the restriction.
| || |
|Investigating agency: ||AAIB |
|Report number: ||L-111/15 |
|Status: ||Investigation completed|
|Download report: || Final report|
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