Plane & Pilot
Tuesday, July 9, 2013

The Reality Of Deep Stalls


Stalls are simply stalls, except when they’re not


Aviation educators like to hope that all pilots learned everything they'll ever need to know about stalls when they earned their private pilot's license. It's no big secret that pilots who don't aspire to make a living in the sky will probably have performed the last full stall they'll ever fly on their private checkride.

My wife, Peggy, is a perfect example of a conscientious private pilot who'd just as soon never fly another stall—power-on, power-off, accelerated or any other kind—unless she's a few feet above the ground in a landing flare. She's done all the necessary book work, she understands what causes a stall, and she demonstrated the ability to recover successfully to her examiner last November. She hopes that's the last stall she'll ever have to fly.

That's not a surprise, and many pilots share her lack of enthusiasm for stalls. After all, would you be eager to fly your airplane at the absolute bottom of the performance envelope if you didn't have to? Unless you're a bush pilot or an aerobatic enthusiast, the answer is probably no.

There's one more stall that's the very worst kind, and you'd best hope you never encounter it. This is the dreaded Deep Stall, sometimes referred to as a Super Stall.

The good news is many general aviation designs are relatively immune to deep stalls. Deep stalls are most often associated with swept-wing, T-tailed airplanes, typically designs with wings mounted aft on the fuselage. Many airliners and corporate jets use this configuration, but some smaller aircraft also employ a T-tail. If these aircraft are flown into stall conditions at extreme angles of attack, they can enter a stabilized deep stall from which it may be difficult or impossible to recover.

Despite that introduction, there's nothing inherently sinister about T-tailed airplanes. T-tailed designs are no less stable or difficult to fly than airplanes fitted with conventional low tails or cruciform designs.

The normal goal with T-tails is to mount the elevator, whether it's contained in a stabilizer or an all-flying stabilator, up out of the wash from the fuselage and wings. This usually results in smoother, more effective elevator control. (In jets, another benefit of high tailing is expediting installation of engines on the aft fuselage.)



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