AERO - Tail Strikes: Prevention

Boeing also works to reduce tail strikes through exhaustive takeoff testing, which is a part of certification for any new airplane program. During flight testing, takeoff test conditions are specifically designed to investigate the impact of early rotation, rapid rotation, no flare during landing, and long flare. During this testing, an acceptable margin per certification criteria is established for the design operational use of the airplane. In all cases, Boeing commercial airplanes meet or exceed the design certification criteria for takeoffs and landings, as well as for crosswind takeoffs and landings (see fig. 1). Criteria for engine-out takeoffs and landings are also evaluated (see fig. 2).

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TYPICAL TAIL CLEARANCE FOR TAKEOFF

Figure 1

Model	Flap	Liftoff Attitude (deg)	Minimum Tail Clearance [inches (cm)]	Tail Strike Pitch Attitude (deg)

747-400	10	10.1	39 (99)	12.5
747-400	20	10.0	40 (102)	12.5

This diagram indicates the effect of flap position on liftoff pitch attitude as well as minimum tail clearance during takeoff. The minimum tail clearance depicted is predicated on a no-wind, no-crosswind control, and constant rate of 2 to 3 degrees per second rate of rotation.

TYPICAL TAIL CLEARANCE FOR ENGINES-OUT TAKEOFF

Figure 2

Model	Flap	Liftoff Attitude (deg)	Minimum Tail Clearance [inches (cm)]	Tail Strike Pitch Attitude (deg)

747-400	10, 20	10.6	34 (86)	12.5

When operating with an engine failed at V₁ with only 75 percent of thrust available for a four-engine airplane or 50 percent of thrust available for a two-engine airplane, minimum tail clearance is reduced. If there is a crosswind, the aileron/spoiler displacement will further reduce minimum tail clearance. In all cases, whether operating in one-engine or two-engine configuration during the rotation, a high average rate of rotation above what is recommended will further reduce minimum tail clearance.

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