Airplane Accelerated Stall

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The accelerated stall occurs when the critical angle of attack is exceeded by abrupt control movement, causing the aircraft to stall at a higher-than-normal indicated airspeed. Just because your aircraft has a Vso of 40 doesn’t mean that there is no way it can be stalled at a higher speed. You don’t necessarily have to be nose high to stall it, either. If you exceed the critical angle of attack, you can stall your aircraft going straight up, straight down, or straight and level. Remember, in an accelerated stall, the stall occurs at a higher-than-normal airspeed and usually requires some very rapid control movement to induce the stall. But it will stall.

Everything has its limits and so does your aircraft. What is the highest airspeed at which you can stall your aircraft safely? The answer is the maneuvering speed (Va)—the speed at which you can apply full, abrupt control travel without causing structural damage to your aircraft. Anytime you are at or below maneuvering speed, you can stall your aircraft without worrying about whether you or your wings are going to get to the ground first. It is a built-in safety factor tested by the aircraft manufacturer and certified in your aircraft’s operations limitations.

To practice accelerated stalls, first climb to a minimum stall recovery altitude of 1500 feet above the ground, and then climb another couple of thousand feet for mistakes. Clear the area by doing a 90-degree turn in each direction (or a 180, whichever makes you happy). Look for other aircraft while doing the turns. Too many people go through the motions of clearing turns and use the time to unwrap a piece of gum or adjust the ventilation in the cabin.

The entry speed for the accelerated stall should be no more than 1.25 times the unaccelerated stall speed in a clean configuration: Vsl times 1.25. If your aircraft has a Vsl of 60 knots, this would work out to an entry speed of 75 knots (60 x 1.25 = 75). This rather low speed provides a margin for safety because the load factor at the time of the stall will be lower if it begins at 1.25 Vsl rather than up near maneuvering speed. The stall is less violent and causes less stress on you and your aircraft.

After you arrive at altitude and clear the area, slow your aircraft down to entry speed, and while maintaining constant altitude and a low power setting, roll into a coordinated 45-degree bank. Rapidly increase the pitch as you hold your altitude and the aircraft should stall at a higher-than-normal airspeed. If properly executed, it will stall quickly and break rather sharply. If you turn more than 90 degrees during the execution of the accelerated stall, you aren’t pulling back fast enough on the yoke and probably aren’t getting a true accelerated stall. You don’t have time to eat a hamburger while doing an accelerated stall properly. It happens in a hurry.

Recovery from the accelerated stall is as with all stalls:
• Reduce the pitch to break the stall.
• Add power, if available.
• Level the wings and return to normal flight attitude.

Complete these procedures in that order and quickly. The stall recovery can be initiated at any of the normal recognition cues peculiar to stalls (or impending stalls). These cues are common to all and include the warning horn and/or light, decreasing control effectiveness, buffeting, and finally, the break. The most sinister thing about the accelerated stall is that these cues happen much more rapidly than is the case with most stalls. But if you practice recovery at all the different cues, you will be ready should you ever get into a situation that calls for prompt action.

As far as leveling the wings is concerned, the ailerons will be nearly useless during stalled flight, because smooth airflow over the wings is disrupted. Since the airplane may roll off sharply during the stall break, pilots should counter this rolling tendency, at least initially, with judicial amounts of rudder. The ailerons will become effective again during recovery.

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