Aeronautical engineering and spin proofing

This is a fascinating discussion of plane wing design and avoiding the stall/spin problem.

Many doctors were killed in the v tail doctor killer–the Beachcraft, but that was a different problem apparently, it was such a slick plane that it would exceed airfram tolerances and come apart if the pilot let the nose down.

The stall spin is related to the other major problem–pilots not paying attention to altimeter and flying into a slippy slidey spin to the ground.

Tests on pilots not using instruments showed that the natural tendency of flying by feel is to go into a sliding spin created by dipping one wing or the other.

I don’t fly, but I stayed at Holiday Inn Express sometime in the past.


8 responses to “Aeronautical engineering and spin proofing

  1. From an Aircraft Owner’s and Pilot’s Association report (1994): “The V-tail Bonanza came under close scrutiny in the mid-1980s following a series of in-flight breakups. Several airworthiness directives were issued and a special study was done by the FAA and the Department of Transportation, which resulted in a stabilizer reinforcement kit at the root of the V-tail. After the installation of the kit, the in-flight breakups decreased dramatically.”
    Beyond that, the AOPA found pilot error was the main factor in most of the 523 accidents (for both V-tail and straight tail versions) investigated. “The V-tail pilots were responsible for about 73 percent (248 accidents) of accidents, and the straight-tail pilots weighed in at a whopping 83 percent (154 accidents). “

  2. thanks Tadchem, good info. As I understand it, the Bonanza could go faster than its air frame could stand if it was going down hill. pilot error was the reason it went to fast, and exceeded air frame tolerances. Bonanza was a slick little and owned by a lot of docs–some died finding out about watching the altimeter.

  3. Geologist Down The Pub Sez

    All aircraft can exceed the Never-Exceed Speed if you stick the nose down long enough. The Bonanza just gets to that speed quicker than most. As we used to say in General Aviation, if it weren’t for Bonanza’s we would be up to our ass in lawyers and doctors.

    And spins come from crossing the controls, not from ignoring the altimeter. One of the big problems here is that many years ago they quit teaching spin recovery as part of the Private Pilot curriculum. We learned it later on our own.

  4. Geo–give me a break

    crossing the controls?? what is that ??

    • Pushing bottom rudder instead of banking. Wasn’t that the reason for rudderless planes?

    • To amplify a bit: When making a left banking turn, you normally push left rudder a bit to enter the turn at the time you’re banking the wings into it. The aircraft steers smoothly around the turn with minimum wind friction.

      But if, as Gene said, you push the right rudder pedal instead, the aircraft is banking left but trying to push sort of sideways into the wind. This sets up forces that could cause the plane to fall off into a spin.

      More frequently, the aircraft’s speed drops below what’s need to keep its wings flying, and it “stalls” or suddenly drops as the air breaks away from the wing surface. If this drop is straight ahead and smooth, it’s usually no big deal. But sometimes it drops off to one side, and the aircraft can wind up pushing sort of sideways through the air (as with the crossed controls), spinning slowly and never able to get enough airspeed to fly out of the spin. Most modern general aviation aircraft are designed not to do this or not easily, but “stall-spin” crashes used to be all too common.

      “Stall” in an aircraft refers to the wing quitting, not the engine. The engine can be roaring full-tilt, but if in a spin the pilot is hauling back on the controls, the airplane is struggling to go “uphill” and can never get moving enough to grab the air and get out of the spin. The air over the control surfaces is too slow to create the steering force required. The solution is simple: Nose down, get a bit of speed, and the problem solves itself. You’re flying again.

      But many pilots have gone to their graves, all too literally, not realizing this.

      ===|==============/ Keith DeHavelle

  5. Hank de Carbonel

    Off subject some. After the Air France Airbus loss in the So Atlantic, Rio, to Paris there was talk of pitot problems.I never read what was the difference between Airbus and Boeing pitots and how could it be after decades of pitots, which seem very low tech.

  6. Hank, have no knowledge of the Boeing v Airbus pilots.

    Keith, I was stunned to find out that if you put the hood on a pilot they will, by the seat of their pants, get into a spin attitude within a very short time, less than 5 minutes.

    That’s a scary thing and recommends not flying by your pants, maybe look at the altimeter and avoid the yaw to spin problem.

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