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1 The Accident as a Situational Example
The flight departed from an airport where dispatch had released another aircraft to make up for delays that would otherwise have taken your crew beyond the airline’s duty time limitation (14 hours).
You are an above-average junior first officer and have not previously flown with your captain, who is quite senior and a former station chief pilot. While waiting for the aircraft, you received an advisory from the airline and from the national weather service that there is thunderstorm activity all along your route.
In flight, messages from the airline reiterate this weather for the arrival but do not mention delays or diversions. An en route air traffic control (ATC) center broadcasts significant meteorological information (SIGMET) about a line of severe thunderstorms with large hail and strong wind gusts. After transfer to the next ATC center, it appears that the controllers do not have access to real-time weather radar data and that no meteorologists are on duty at the center.
What do you think of the weather situation?
You begin to realize that the flight conditions will be very turbulent with a line of squalls heading for your destination airport. You press ahead and tell the cabin staff to complete passenger duties. You go through the descent and approach checklists, selecting manual brakes rather than autobrakes at the captain’s request.
ATC informs you that a thunderstorm northwest of the airport is closing in. You discuss crosswind limitations for landing. Unaware of the storm’s severity because of technical radar limitations, ATC offers a visual approach to the runway, which you acknowledge inconclusively while waiting for further weather information. A few moments later, ATC informs you that surface winds have shifted and that the airport low-level Low Level wind shear alert system (LLWAS) has generated a wind shear alert.
In light of this wind shear alert, what would your next step be?
Preferring a headwind landing, you inform the controller. He then vectors you for a right turn from your northeasterly heading 4 nm southeast of the airport, the long way around for an Instrument Landing System (ILS) (instrument landing system) approach to another runway.
You conduct an abbreviated briefing for the new runway, including localizer frequency, final approach course, minimum safe altitude and decision altitude, but do not include the missed approach procedure. You see the airport, but the captain, the pilot flying, does not. He requests a first selection of flaps and asks for visual cues that he has difficulty getting and maintaining.
You also lose visual reference. ATC gives an intercept heading for an ILS approach and instructs you to descend. You are very close to the storm. Then you are cleared to continue the right turn to join the localizer close to the outer marker (OM).
ATC clears you for the ILS approach and to turn to a right heading 3 nm (6 km) from the OM. The controller adds that there is heavy rain over the airport, visibility is less than a mile, runway visual range (RVR) is 3,000 ft (1,000 m) and there is a crosswind of 300 degrees at 30 kt gusting to 45 kt. You read back this wind information as 030 degrees gusting to 45 kt, which would give a crosswind component of less than 10 kt. ATC does not correct you.
The airport’s automated surface observing system (ASOS) is not available.
At this stage, the aircraft intercepts the localizer with the captain still undecided as to landing with such an RVR and requesting landing gear and lights. ATC relays another LLWAS alert — wind 350 degrees at 32 kt gusting to 45, and the RVR down to 1,600 ft (500 m). Established on final, the captain asks for 20 kt to be added to the final approach speed of 130 kt.
What do you suggest to the captain?
Passing 1,000 ft, you suggest full flaps while still helping the captain with visual references. The resulting rapid pitch change becomes an extra disturbance in trying to stabilize the aircraft.
The approach is stabilized until the aircraft begins drifting right at about 400 ft above ground level (AGL), one dot to the right of the localizer course. As it nears the decision height (DH) of 460 ft, the glideslope deviation is between one and one and a half dots and increasing. When the aircraft is between 5 ft and 20 ft above DH, the captain acquires visual contact with the runway for the first time. Seconds later, however, the ground-proximity warning system (GPWS) “SINK RATE” warning sounds. You then call out radio altitude in 10-ft increments until touchdown about 2,000 ft from the runway threshold with a right drift angle of 5 degrees at 147 kt and near maximum landing weight.
Since manual brakes rather than autobrakes had been selected at the captain’s request, the autospoiler system is not activated. Therefore, the spoilers do not extend automatically at touchdown. The crew does not react by extending them manually. Consequently, the aircraft is hydroplaning with very little effective braking or steering. The aircraft points left and skids right. Reverse thrust has little effect because rudder effectiveness has decreased.
After departing the end of the runway at 70 kt in a left skid, the aircraft strikes the left edge of the ILS localizer array, passes through a security fence and over a rock embankment to a floodplain below the runway, and collides with the structure supporting another runway‘s lighting system.
2 Data, Discussion and Human Factors
Approach-and-landing accidents account for 55 percent of hull losses and 50 percent of fatalities (Flight Safety Digest, “Killers in Aviation,” 1999). The following points illustrate the human factors elements in this case:
3 Prevention Strategies and Lines of Defense
Whenever there is a change in the assigned runway and insufficient time available to prepare for the approach, a crew must focus more on being prepared for a go-around.
All along, accurate risk assessments and tactical decision making must be performed based on weather and winds, approach type, and risk of specific threats, such as an approach conducted in haste.
Whenever a difficult situation occurs for either crewmember, critical thinking should become part of flight management.
The following warning signs of error chain formation have been identified:
You must recognize and break the error chain before it breaks you.
4 Key Points
The probable causes of this accident were the crew’s failure to discontinue the approach when severe thunderstorms were in the airport area and the failure to ensure that the spoilers had extended after touchdown. The crew could have stopped the aircraft with 700 ft (213 m) of runway remaining had the spoilers been extended, maximum braking used and reverse thrust maintained at the appropriate setting.
Contributing to the accident were the flight crew’s impaired performance resulting from fatigue and the stress associated with the intent to land under the circumstances; continuation of the approach to a landing when the company’s maximum crosswind component was exceeded; and use of excessive reverse thrust adversely disrupting airflow over the rudder, impairing directional control.
This accident was preventable if the pilots had recognized that they were driven by ATC into a high and fast situation that they could and should have refused.
Human factors issues in the unstabilized approach include:
5 Associated OGHFA Material
6 Additional Reading Material
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