On 22 of January 2002, a Boeing 757-200 operated by Icelandair commenced an unstabilised approach to Oslo Gardermoen airport in instrument meteorological conditions (IMC) and in the presence of a strong tail wind. The result was a near loss of control and low altitude go-around with exceedance of speed limits and g-values exerted on the airframe.
The following is an extract from the official incident Report published by the Accident Investigation Board Norway (AIBN):
“[…] The change of runway, the strong tail wind and the shortened approach path resulted in the aircraft becoming high on the approach profile.
[…]As the Commander doubted that the AP [autopilot] in AUTO mode could capture the GP, he disconnected both AP’s and the Auto Throttle (AT) with the thumb-switches in order to manually capture the GP from above. The aircraft was flown manually the remainder of the approach, and the throttles were also operated manually until TOGA was initiated. Shortly there after, the Commander noticed that raw data information of the ILS on his ADI and HSI were lost. No flag warnings were observed. The Commander reduced the rate of descent because of the uncertainty. The raw data signals on his instrument panel appeared and disappeared again. The First Officer was informed, but on his instruments all indications were normal. The crew did not consider a change of controls at this time.
At an altitude of approx. 580 ft AAL (Flight Data Recorder (FDR) radio altimeter reading) the Commander decided that he discontinued the unstabilized approach and initiated a missed approach. […] He announced his decision to the First Officer and started a “Go-Around” (GA).
The status of the flight was as follows: The aircraft was above the GP, and the SOPs calls for the GA altitude to be set when stabilized on GP, therefore the GA altitude was not set on the MCP. Flaps were not in landing configuration, because landing Check List was not completed. The Commander’s instrument panel indicated intermittent ILS failures of raw data without any flag warnings. The lowest altitude AAL indicated on the FDR was approx 460 ft.
[…] When the go-around manoeuvre was started by the use of the auto go-around system, the speed was 182 kt. Upon initiating the go-around, the A/T automatically engaged and increased the thrust to the EPR (Engine Pressure Ratio) limit. The flight director pitch initially targeted a pitch attitude of 15o. The airspeed reached a maximum of 198 kt before it started to decrease.
Because of the aircrafts proximity to the MCP selected altitude of 2 500 ft when the go-around was started; the AFDS transitioned to Altitude Capture almost immediately after a positive rate of climb was achieved. At time 09:49:19 UTC the aircraft climbed rapidly through the MCP altitude of 2 500 ft, The FD continued to give commands targeting the MCP selected altitude. The A/T changed from go-around mode to targeting the MCP selected speed (150 kt). The maximum aircraft pitch (21 degrees) was reached. The thrust remained near maximum because the Commander held the throttles forward. The speed was decelerating and quickly dropped below MCP speed. The pitch flight director continued to give command to lead the pilot back to the MCP altitude.
[…] the aircraft reached a peak altitude of 2895 ft (FDR QNH corrected altitude) and the speed had decreased to 137 kt. (The reference speed for flaps 20 degrees is 131 kt.) Nose down was applied manually by the control column. The First Officer called for “bug up” (for the flap up manoeuvring speed) to set the airspeed indicator, and the Commander pushed on the Flight Level Change Switch (FLCH) button to break the flight director altitude lock on. The speed selected on MCP was changed from 150 kt to 210 kt. During the next seconds, a full nose down input on the control column was made manually. The aircraft pitched over to an attitude of approx. -30 degrees, and for a period of approx. 5 seconds the FDR indicates negative g-values with a maximum load factor of -0.6 g.
The control column was briefly returned to near neutral, and then another abrupt large nose down column input was made. The aircraft pitched over rapidly with the speed increasing excessively. The FDR data show that the Ground Proximity Warning System (GWPS) aural warning of “Pull up” was activated. The aircraft was now in a steep dive and rapidly descending. During the dive the flight director pitch bar gave pitch up commands relative to the pitch attitude. The A/T reduced the trust from 98% N1 to 45% N1. […] the aircraft pitch attitude had peaked at -49 degrees and was beginning to increase positively.
At this time the First Officer called out “PULL UP!” - “PULL UP!”. The GPWS aural warnings of “TERRAIN” and then “TOO LOW TERRAIN” were activated. Both pilots were active at the control columns and a maximum “up” input was made. A split between left and right elevator was indicated at this time. It appears the split occurred due to both pilots being active at the controls. The pilots did not register the aural warnings. During the dive the airspeed increased to 251 kt and the lowest altitude in the recovery was 321 ft radio altitude with a peaked load factor of +3.59 g’s.
The recovery continued with the aircraft pitch attitude increasing to about 40 degrees, and a positive rate of climb was established.[…]”
The second approach and the subsequent landing were uneventful.
The Report further states:
The importance of crew cooperation is imperative. In this case, AAIB/N is of the opinion there was a complete breakdown of crew management and a lack of interaction at an early stage. When the confusion started, the combination of one pilot manually operating the controls partly in opposition to the automatic throttle movement made this “upset” understandable. This can be referred to as an “automation trap”. When “bug-up” is selected to target speed, this command gets cancelled by selection of “Flight Level Change” or by altitude capture. The speed then becomes “present speed”. This caused the aircraft to act differently than the pilots had anticipated. This resulted in confusion and was probably a factor in causing the incident to occur.
In the opinion of AIBN it is not satisfactory that a seemingly properly trained and qualified airline crew should end up loosing control of a modern airliner and cause an incident like this one.
The AIBN produced the following recommendations based on the incident:
- That the aviation community should review the operational procedure regarding discontinued approaches. The company should also review the flight crew training regarding an unstabilised approach followed by a go-around […].
- That the company should consider its plans for colleague support in relation to accident and incidents. […]
- That the company should consider utilizing the quick access recorders for continuous monitoring of flight operations standards.
- That CAA/N should consider the effect of ATC shortening the approaches in IMC for airline-crew with possible limited experience of the Oslo area, and the effect it has on the crew’s ability to manage the aircraft energy and to stabilize the approach[…].
For further information see the full incident report published by AIBN.