Flybe DH8D at Manchester on Nov 16th 2011, descended on glideslope without being established on localizer

Last Update: April 12, 2012 / 15:23:26 GMT/Zulu time

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Incident Facts

Date of incident
Nov 16, 2011

Airline
Flybe

Flight number
BE-664

Aircraft Registration
G-ECOK

ICAO Type Designator
DH8D

A Flybe de Havilland Dash 8-400, registration G-ECOK performing flight BE-664 from Knock (Ireland) to Manchester,EN (UK) with 46 passengers and 4 crew, was on approach to Manchester's runway 23R cleared for the ILS approach. Without establishing on the localizer (extended runway center line) and flying more than 2 dots course deflection indication to the right of the centerline the aircraft commenced its descent on the glideslope indication until air traffic control instructed the aircraft to go around when it descended through about 800 feet above the aerodrome level of 250 feet MSL. The aircraft subsequently positioned for another approach and landed safely. The British Air Accident Investigation Branch (AAIB) released their bulletin reporting that the crew consisted of a captain (46, ATPL, 7,000 hours total, 1,600 hours on type) and an acting first officer, who actually was a training captain, occupying the right hand seat. The acting first officer was pilot flying, he had briefed for the ILS/DME approach stating that he wanted to fly the approach manually with the flight director for practise. The weather at Manchester was reported at 3900 meters visibility in haze, light and variable wind and scattered cloud at 800 feet above aerodrome level. The aircraft was vectored for an ILS approach to runway 23R (heading 234 degrees) and had descended to 2500 feet. The flight guidance approach mode had been armed. When the course deflection indicator began to move from full scale, both localizer and glideslope capture modes engaged automatically, the acting first officer followed the fly right indications of his flight director and commenced the descent according to the flight director indications. The course deflection indicator however commanded a fly left with the flight director continuing to command a turn right. The crew became aware of being substantially right of the extended runway center line and suspected they had captured a false localizer. The acting first officer therefore selected heading and vertical speed modes steering the aircraft left while continuing the descent, and armed the approach mode again. He then thought seeing conflicting indications with the captain's side indicating fly left and his side indicating fly right. A cross check with the multi function display confirmed they were still right of the extended runway centerline and right of the localizer. The first officer indicated he would initiate a go-around at 1000 feet above aerodrome level if they had not established on the localizer by then. When the aircraft descended through 1300 feet MSL air traffic control asked whether they were visual with the runway. Although the crew had ground reference and were able to recognize significant features in the area they were not visual with the runway or its approach lights, ATC therefore instructed the crew to go around. While the aircraft was re-positioning for another approach the crew noticed that the inbound courses selected on the flight guidance control panel differed from each other, the right hand side had been correctly selected to 234 degrees, the left hand side however had been incorrectly set to 265 degrees. The left hand inbound course was selected to 234 degrees and a second approach was completed with a safe landing. The operator commenced their own investigation into the occurrence stating: the two pilots worked together effectively to resolve the problem they were faced with, although there existed a relatively unusual situation whereby the acting First Officer was senior to the aircraft Commander by virtue of his Training Captain status. The crew retained sufficient situational awareness to determine that the aircraft was not on the correct track, although this would probably not have been aided by the miss-set course on the CommanderÂ’s side. It was also noted that the crewÂ’s capacity to deal with the problem may have been enhanced if the autopilot had been engaged. Although the crew maintained an overall awareness of their situation and were endeavouring to correct it, it was established that they had begun to deviate from standard operating procedures in allowing the aircraft to continue to descend without it being correctly established on the localiser. Data of the quick access recorder showed the aircraft was heading at 200 degrees and descending when both localizer capture and glideslope capture modes activated, at that point the aircraft was about 2.5 degrees off the localizer. As the aircraft was already descending the descent continued uninterrupted, the heading bug was changed to 234 degrees in accordance with the runway heading, the aircraft however continued to turn right beyond 234 degrees until about 255 degrees. The fly left indication reduced from full scale to about one dot before increasing again to full scale as the aircraft turned away from the localizer center line. The aircraft subsequently slowly turned left until about 210 degrees. The fly left indication began to reduce again, at 1700 feet MSL the localizer and glideslope capture modes armed again followed by another right turn beyond the inbound course of 234 degrees. When the aircraft descended through 1050 feet MSL the course deflection indicator was again full scale left, the crew initiated a go-around upon ATC instruction at that point. The quick access recorder showed left and right ILS course deflection indicators were in agreement through all time, comparism of radar data with the indicated deflections showed good correlation. The AAIB analysed: It is reasonable to assume that the handling pilot followed the flight guidance on each occasion (as he reported) in which case the flight guidance system responded in a very similar manner on each occasion too. With both ILS receivers showing consistently accurate deviation and the position and altitude of each intercept being different, it is most likely that the guidance issue arose as a result of the discrepancy between the left and right inbound courses selected on the flight guidance control panel.
Incident Facts

Date of incident
Nov 16, 2011

Airline
Flybe

Flight number
BE-664

Aircraft Registration
G-ECOK

ICAO Type Designator
DH8D

This article is published under license from Avherald.com. © of text by Avherald.com.
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