Escape Maneuvers

Escape Maneuvers

DOI: 10.4018/978-1-4666-8673-1.ch009
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Important escape maneuvers are covered here. From a mission success standpoint, the information presented is arguably the most important. The terrain escape maneuver, wind shear escape maneuver, engine failure during second segment climb, upset recovery maneuver, and stall warning and recovery during takeoff operations are discussed in detail. Terrain escape maneuvers include operations from terrain critical airports when the engine fails. This information is useful to not only system designers but training designers as well. We also introduce the dynamic “rudder bar.” The rudder bar improves maneuver precision but reduces workload. We contend that the escape maneuver package presented here become part of the crew station for all future aircraft and retrofitted to all aircraft currently operating that possess data bus technologies.
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Escape Maneuvers: Wind Shear

Encountering a wind shear event is a serious challenge for all flight crews. During this type of event, atmospheric disturbances will impact the dynamics of the aircraft by reducing energy or causing inadvertent rolling or pitching moments. Energy change can be either minor or dramatic. Airspeed may fluctuate and flight trajectories may be significantly altered. Each fluctuation of airspeed may signify a complete cycle of the disturbance. These repetitive short-term encounters can be caused by atmospheric eddies, in turn caused by convective or frontal weather conditions. In some dramatic encounters the aircraft can experience large, rapid changes in airspeed and G-force levels.

An example of a minor encounter may be the crossing of a cold front where the aircraft may experience an increase or decrease in indicated airspeed. This often is because of wind directional shift. Usually the aircraft will return to its original condition after a short time.

More dramatic conditions, known as microburst events, are of the greatest concern. These events are extremely dangerous because they may represent conditions in which the aircraft does not have enough energy for recovery. Consequently, avoidance is of primary concern. The escape maneuver should be used as a last resort in these instances.

Energy Management

Maximizing the energy state of the aircraft in any escape maneuver is essential. This is optimized by selecting maximum thrust for these maneuvers. For all escape maneuvers, selecting maximum thrust is almost always required. Establishing the optimum climb angle is the next objective. Such an angle will clear all threatening terrain in the projected flight path. This should be done without significantly reducing the airplane’s kinetic energy. An initial pitch of 20 degrees nose up has been determined to be the target pitch attitude for all transport aircraft for the purposes of executing a terrain escape maneuver. Twenty degrees nose up is the industry standard. If the terrain continues to rise ahead of the aircraft, the climb angle is further increased to avoid this deteriorating situation. In extreme cases, the pitch can be increased to the stall warning limit, but this attitude can only be used for a short duration.

From an energy standpoint, the last ditch effort is a tradeoff. While it may provide some increase in flight path angle to clear the immediate terrain, the subsequent flight path may degrade in terms of a climbing trajectory. This is why the pitch attitude target is set where additional energy reserves are available.

Figure 1.

GPWS escape maneuver


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