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Why you should teach the power-on stall with engine failure

A new stall series

At a safe altitude (we suggest at least 3,000 feet agl), introduce students and pilots to whom you give recurrent training to the following maneuvers. Follow guidelines in your airplane's POH to ensure no limits are exceeded. Also, avoid abrupt power reductions in high-performance aircraft. Keep in mind that when you transition from a climb, you may still be holding in rudder correction to counteract the torque, creating an uncoordinated situation that could lead to an incipient spin if the stall recovery isn't prompt.

  • Power-off stall, clean configuration. This will establish a baseline from which to determine how the pitch attitude, deck angle, timing, and stall profile changes in the next two maneuvers.
  • Climb profile to best-glide attitude. Establish a climb at VX, pull the power, and pitch to recover best glide airspeed promptly. Note your altitude loss--you can work to minimize this while acquiring best glide in a timely fashion.
  • Climb profile to a power-off stall, clean configuration. Start with a climb at VY, then do another one from a climb at VX. Measure the amount of time between the power reduction and the incipient stall. Remember to neutralize the rudder.
  • Climb profile to a power-off stall, takeoff configuration. Use the normal takeoff flap setting, and try one with the gear up and one with the gear down.

--JKB

There's been a terrible accident; we think it was Leo; there were no survivors. The details were sketchy, but it was day VMC at Falcon Field in Atlanta that morning. Calm winds, a long runway--and an engine failure after takeoff. The airplane stalled, lost the hundred feet or so it had gained since liftoff, and became a crumpled pile of parts on the ground.

Leo was not the first pilot to lose his life at that airport to this scenario. So why would a competent, experienced pilot be unable to cope successfully with such an emergency--especially when there were plenty of options for a safe off-airport landing?

The preliminary accident report sounds familiar: After hearing a "change in engine noise," witnesses described the airplane leveling off, beginning a descent, then making a shallow turn, followed by a steep bank, loss of altitude, and "spiral" out of view.

Your classic stall-spin accident, right? The one you inoculate your students against by practicing departure stalls, and admonishing them not to turn back to the runway in this situation but to land straight ahead, right?

Not quite. What if turning back had nothing to do with it? Have you ever asked your students to perform a power-on stall with an engine failure? Have you ever demonstrated how much a pilot has to push first to make that off-airport landing happen safely?

Advisory Circular 61-21A--you know it as the Flight Training Handbook--was superseded in 1999 by the Airplane Flying Handbook (now in a second edition, published in May 2004 as FAA-H-8083-3A). Only in the latest revision is any mention made in the Airplane Flying Handbook of what to do if the engine fails after takeoff. In Chapter 5, "Takeoff and Departure Climbs," there are just two paragraphs on the scenario, with an emphasis on the urgency of the situation.

The FAA adds to its reference library with advisory circulars, and one in particular, AC 61-67, Stall and Spin Awareness Training, should address more fully the "engine failure after takeoff" scenario. And it does--by admonishing pilots not to turn back to the runway. Although this is a problem, it's not the first problem encountered by a pilot when the engine quits after takeoff. The first order of business is maintaining control of the airplane--and capturing best-glide airspeed when you're already climbing out at a comparable speed (and a high deck angle) is very different from capturing it from cruise flight.

The most critical thing is to prevent a stall from occurring on the heels of the engine failure--and to maintain the energy to control your descent and landing flare. Are you teaching your students about this critical area? It's nowhere in any of the practical test standards.

Most power-on stall recovery procedures involve relaxing the back-pressure, which lets the nose come down to about the horizon, to regain airspeed. The pilot's right hand is on the throttle (in most light aircraft) to ensure full power. The goal is to lose as little altitude as possible without inducing a secondary stall.

Setting up for a power-off stall is much the same. To recover, you reduce the angle of attack, bring in full power (and shut off the carb heat if necessary), clean up the airplane, and pitch to the horizon. Again, you're trying to minimize your altitude loss, because the stall itself is the primary problem.

Now consider this: You take off, climbing out at VX to maximize your altitude. At 200 feet agl, you cross the airport boundary fence--and the engine quits.

You have the deck angle of the power-on stall, yet the power's off--and you're not getting it back. You have a healthy amount of rudder pressure in to counteract torque--so you're uncoordinated unless you neutralize the rudder. You will stall if you keep the nose up. If you pitch down to just the horizon, you won't recover all the energy that you lost when the prop stopped moving. And if you continue holding rudder pressure, you may fall off into an incipient spin, even if you keep the airplane's nose pointed straight ahead.

To address this scenario, you need to measure the difference between the time it takes for your training airplane to stall from level cruise flight (slowed to VY) when the power was reduced to idle and the pitch attitude held in place, and the time it takes to stall from a VY climb when the power was reduced to idle and the pitch attitude similarly fixed.

When I tested the maneuver in a Cessna 172S, the time it took to reach imminent stall in the first scenario was 12 seconds. The time it took to stall in the second scenario? Five seconds. It's even less if you're climbing at VX.

VY in most light singles can be pretty close to best-glide airspeed; VX is often several knots below best glide, as it is in the 172S, and only marginally above the corresponding wings-level stall speed. At most, VY is 20 kt more than best glide--it's 14 kt above VY in a Cirrus SR22 as tested at max gross weight--but the moment the engine stops, that airspeed starts going away. With that deck angle (in some high-performance singles you may be pitched up as much as 10 degrees) and the airplane trimmed for the climb, the airspeed ticks away quickly.

You will need to pitch down deeply below the horizon to regain airspeed and arrest the sink rate--up to 10 degrees below the horizon, depending on the airplane, its configuration, the sink rate, and the density altitude. Pitching down this much can require a significant amount of stick or yoke travel--for example, in a tailwheel Cessna 150, it takes about three inches of travel, overcoming aerodynamic and trim forces in the process. It takes a push.

Also note the altitude loss before you recapture best-glide airspeed. I had lost at least 200 feet in the 172S. Getting that energy back so you can flare may be all you have time to do. Keeping the wings level also increases your margin from the stall: The very act of the turn increases the load factor and the stall speed. If you feel heavy in your seat, you're entering dangerous territory. You have to trade back some of the energy by dropping the nose farther, reducing the angle of attack, and getting your margin back.

There's no single category that "engine failure after takeoff" accidents fall into. Instead, they lie buried in at least three separate categories within the general aviation accident data. Because these accidents happen with the takeoff, some are classified as "takeoff" accidents. Because some are the result of mechanical failures, some are classified under this category. Accidents may also go into the "maneuvering flight" bucket--the way the NTSB sees it, once you start to turn, you're maneuvering.

According to a preliminary search of the AOPA Air Safety Foundation's accident database covering the past five years, accidents fitting the profile occurred more than five times a year in airplanes less than 12,500 pounds. At least three accidents occurred involving instructional flights in which the instructor was demonstrating or observing a student managing a power loss after takeoff at low altitude, with an attempted return to the airport. All of these accidents were fatal.

Because the typical accident profile involves a power failure and happens in close proximity to an airport, there is an opportunity for a pilot to successfully manage the power loss and land the airplane without damage. These "success stories" would not necessarily fall within the criteria for reporting as an accident or incident, and thus be off the radar.

But the accidents continue. Since September 2006, another 19 accidents have potentially been attributed to improper response to an engine failure on takeoff--including one involving a student on a solo flight.

Julie K. Boatman is contributing editor of AOPA Flight Training magazine and technical editor of AOPA Pilot magazine. She has been a CFI since 1993.

By Julie K. Boatman

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