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Engine Separation After Takeoff (OGHFA SE)
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Revision as of 12:16, 25 October 2012 by Timo.Kouwenhoven
|Content source:||Flight Safety Foundation|
|Human Factors Aspects||Unexpected Events, Airmanship, Crew Coordination, Decision Making|
|Flight Phase||Climb, Descent|
|Operator's Guide to Human Factors in Aviation|
|Engine Separation After Takeoff|
The Incident as a Situational Example
Your four-engine airplane is scheduled for a midday departure for a long-haul flight from a major airport. Your crew receives a forecast of severe turbulence during climb-out as well as a notice that severe turbulence has been reported by the crews of other large airplanes. You brief your crew on the possible turbulence and tell them to be prepared for a rough ride.
After takeoff, at about 2,000 ft, the airplane experiences an uncommanded left roll of approximately 50 degrees. While the target airspeed is 183 kt, the airspeed fluctuates by about 75 kt, from a high of 245 kt to a low of 170 kt. Just after that, you experience significant yaw, the no. 2 throttle lever slams to its aft stop, the no. 2 reverser indication shows thrust reverser deployment, and the no. 2 engine electrical bus fails.
What is your diagnosis of the situation?
In fact, unknown to you, the no. 2 engine has actually separated from the airplane. Witnesses on the ground report later that the airplane experienced several severe pitch and roll oscillations before the engine separated. Detailed investigation after the event indicates that there is no reason for you to have suspected that the airplane would be damaged during climb-out as the level of turbulence encountered is within the design limits of the airplane, and previous departures encountered the same conditions without any problems.
Shortly after the engine separates from the airplane, your crew carries out the emergency checklist memory items for an engine failure.
What is your next move?
You decide to make an in-flight turn-back (IFTB) and instruct the first officer (FO) to declare an emergency. Air traffic control (ATC) accepts the emergency and offers any of the airport’s runways for the return. You instruct the flight engineer (FE) to lock down the leading edge devices using the manual extension method and to begin dumping fuel.
How would you organize your crew?
Immediately after deciding to declare an emergency and executing an IFTB, you begin delegating important duties. You choose to concentrate entirely on flight path control and to delegate communications to the FO. The FE is assigned systems management, including the engine shutdown procedure, fuel dumping and handling the subsequent failures of a generator and hydraulic system. The FE is later assisted by two positioning FEs aboard as passengers in making calculations on the fuel dumping procedure and landing weights.
You are initially unable to maintain altitude.
What is your next move?
You use emergency/maximum power on the no. 1 engine, full rudder authority and almost full right aileron to maintain control. The stick shaker and bank angle warnings activate intermittently throughout the remainder of the flight. Once you re-establish a reasonable degree of control, you initiate a wide-radius turn to the left to return and land on the departure runway. While on the downwind portion of the landing pattern, bank angles alternate between wings level and momentary excursions that exceed 40 degrees.
The FO maintains ATC communications while surrounded by high background noise from multiple alarms and alerts. Poor sound quality on the intercom also limits the potential use of ground resources such as the airline’s technical department. Even though two fighter airplanes rendezvous with your airplane to assess the extent of the damage, any possible assistance is thwarted by poor communications. You are not able to confirm the nature and extent of the damage the aircraft has sustained until after you land.
Which option do you choose?
- Continue dumping fuel
- Make an overweight landing
Because of the handling and communications difficulties, you decide to make an overweight landing instead of continuing to dump fuel. You instruct the FE to stop dumping fuel as the airplane turns onto final approach. The extension of the landing gear is delayed until the airplane is on short final. The airplane intercepts the glideslope between 500 and 600 ft. At 300 ft, you call for flaps 25. The aircraft lands and taxies safely to the gate even though the landing weight is 17 percent higher than the maximum certified value.
After landing, you note that the brakes on the left side are very hot. You inform ground personnel to take precautions to protect themselves from the potential danger of an explosion of the wheels and brakes due to the overheating. The damage to the airplane is substantial — likely beyond what would be economically viable to repair. Nevertheless, the event results in no loss of life or injury.
Data, Discussion and Human Factors
From the review of this accident, it is clear that the crew:
- Faced significant stress and time pressure.
- Did not have perfect situational awareness because noise and the inability to see the no. 2 engine prevented them from confirming any details of what had happened.
- Followed the “operations golden rules” and concentrated on the tasks of aviate, navigate, communicate, manage without giving in to distraction.
- Was disciplined throughout the event and practiced good airmanship.
- Applied crew resource management (CRM) skills to achieve effective leadership and support, making use of all available resources.
- Used excellent judgment and demonstrated effective decision making in accordance with known operational facts.
The crew was cool, calm and collected in its response to stress and time pressures despite the many physical and emotional stress factors that could have affected performance, including:
- Severe turbulence.
- Marginal control of the aircraft that might have caused anxiety. The crew responded by focusing primarily on maintaining control of the aircraft despite almost losing control twice.
- Uncertainty concerning what actually had happened and therefore how extreme the situation actually was.
- Existence of multiple failures that greatly increased workload.
- The short time frame within which the events occurred and the intensity of the activity required to return safely.
- Persistent noise from alarms and warnings.
Despite these stress factors and pressures, the captain was able to maintain control of his emotions and transfer his positive attitude and confidence to the other crewmembers. The negative effects of the acute stress only appeared after landing, when the captain suffered a severe stomach ache for several hours.
The crew’s situational awareness was incomplete as a consequence of limited information availability. They therefore focused on producing an accurate response to their situation rather than becoming fixated with determining the causes of their predicament. It is ironic that the crew’s lack of complete situational awareness of the seriousness of the aircraft failure may actually have protected them from developing excessive anxiety.
The captain quickly realized that the aircraft was in significant danger and devoted his efforts to re-establishing and maintaining aircraft control. He delegated additional critical tasks clearly to the other crewmembers so that everyone had a full understanding of the duties they were to perform. Likewise, the FO focused on helping the captain by handling communications and assisting in the engine failure procedure rather than overanalyzing the causes of the situation.
The crew never lost sight of the operations golden rules. In spite of many competing needs, they never permitted distraction to compromise the primary functions of aviate-navigate-communicate-manage that are fundamental to safe flight.
The crew remained disciplined throughout the event. They remained calm, followed standard operating procedures (SOPs), did not cut corners and showed appropriate concern for others by warning ground personnel of the excessive brake and wheel temperatures.
Good CRM was applied throughout, including:
- Ensuring that all appropriate resources, including the FEs traveling as passengers, were used.
- Making sure that vital communications were not disrupted.
- Delegation of tasks by the captain while coaching the entire crew and maintaining flight path control all the way to touchdown.
- Excellent teamwork among crewmembers with each focusing on his own area of concern while supporting others both verbally and technically without criticism.
- A firm resolve to bring the flight to a successful conclusion. Nobody gave up or gave in to negative thoughts.
- The firm yet charismatic behavior of the captain, which ensured effective support.
Good judgment and decision making were exhibited throughout the flight, along with proper and timely setting of priorities. Examples of good judgment and decisions included:
- The immediate decision of the captain to establish priorities and delegate tasks to his crew based on the assumption of a simple engine failure even though the exact nature of the problem was unknown. This focused them on a manageable set of tasks and avoided fixation on problem-solving, which might have compromised the effective application of the operations golden rules.
- A decision by the crew to refrain from pulling the aural warning circuit breaker to silence the multiple alerts and alarms they were receiving. Even though the alerts hindered the clarity of communication with ATC, they preserved awareness of existing failures and any possible additional failures. The crew considered the benefits from the alerts to be sufficiently important to tolerate the intrusive noise.
- The decision by the captain to use the resources of the two positioning FEs to assist in making calculations on the fuel dumping procedure and landing weights. This distributed the high workload across five crewmembers rather than three.
- The decision by the captain to delay the fuel dumping procedure for a few minutes while overflying inhabited areas at low altitude. This preserved safety on the ground and created additional time for planning.
- The captain’s decision to make an overweight landing rather than to risk additional flight time in a crippled aircraft.
- The captain’s decision to delay gear extension until 300 ft above ground level to benefit from the attenuated roll and pitch movements produced by ground effect.
- The decision to notify ground personnel of the high wheel temperatures to protect them from harm.
Prevention Strategies and Lines of Defense
This event is an excellent example of how the application of various human factors techniques can combine with technical knowledge and good flying skills to produce effective airmanship and successful problem resolution.
The main lessons that can be derived from this event include:
- Follow SOPs, set clear task priorities and maintain discipline.
- Do not abandon good airmanship no matter how desperate the situation appears.
- Follow the operations golden rules by considering trajectory control (aviate and navigate) as first priorities, followed by communication and system management.
- Be alert for additional unexpected events which often arise under abnormal and emergency conditions.
- Practice effective CRM by:
- Clearly defining objectives (e.g., when the captain decided on an IFTB and an overweight landing).
- Providing mutual backup and support to other crewmembers whenever possible, even if a full cross-check is not feasible.
- Communicating all intentions and actions so that the entire crew is fully aware of what is going on.
- Giving encouragement and constructive advice to fellow crewmembers.
- Using all available resources.
- Keep decision making flexible by:
- Avoiding the temptation of trying to bring a bad situation to an end quickly.
- Keeping your options open even after initial decisions have been made.
- Discussing perceptions and impressions with other crewmembers to refresh situational awareness.
- Staying ahead of the aircraft at all times.
- Sharing tasks whenever possible to reserve capacity for additional decision making.
- Keeping it safe and simple by not engaging in unnecessary analysis while an event is unfolding. There will be abundant time to evaluate what happened after you are safely on the ground.
The successful resolution of an in-flight problem such as an engine separation is dependent on the application of good human factors principles. Airmanship, discipline, communication, CRM (teamwork, leadership), judgment, effective decision making and adherence to the operations golden rules (aviate, navigate, communicate, manage) are vitally important when dealing with unexpected events.
Associated OGHFA Material
The following briefing notes provide expanded information on key human factors principles:
Additional Reading Material
- Foushee, H. Clayton; Helmreich, Robert L. “Group Interaction and Flight Crew Performance.” In Human Factors in Aviation, edited by Earl L. Wiener and David C. Nagel. San Diego, California, U.S.; Academic Press, 1988, ISBN: 0-12-750030-8.
- Orlady, Harry W.; Orlady, Linda M. Human Factors in Multi-Crew Flight Operations. Hants, England; Ashgate Publishing, 1999, ISBN: 0-291-39838-3 (hardcopy) or 0-291-39839-1 (paperback).
- Smith, Kevin M.; Lofaro, Ronald J. In Proceedings of the Tenth International Symposium on Aviation Psychology, Ohio State University, May 3-6, 1999.