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  • Stall

    While this thread might belong to the briefing room, I decided to post it here because it's highly connected to safety (as will be shown) and discussions tend to be much richer here.

    An MD-80 takes off from Detroit. The flpas and slats have been mistakenly left retracted. There is an alarm that should alert the crew of this condition but it failed. The plane crashes shortly after lift-off. Everybody dies, except one child that nobody understands how she managed to survive.

    A second MD-80 taking off from Barajas (Madrid) crashes in almost identical conditions and with the smae result: almost all the passengers and crew die.

    A 737 takes off from Washington in winter. Due to several procedural errors, the engines probes are iced and the related indications are wrong. The applied thrust is not enough to sustain the climb and the plane crashes on a bridge and into a frozen river. Only a handful of persons survive and there are fatalities oin the bridge too.

    A CRJ climbs to 41000ft, has a dual engine failure, hides the situatuin to the ATC, overflies several sutiable airports and crashes, killing both pilots (the only persons in the plane).

    A DC-9 bound for Buenos Aires has frozen pitots but the pilot's don't realize. They believe in the low (and wrong) low airspeed indication and increase power and dive to try to gain airspeed. They do but the indicator still show a too slow airspeed. Fearing a stall, they extend the slats, some of the slats fail and they loose control, falling in an almost vertical dive from cruise to the ground. The airplane almost vaporizes on impact. Of course there are no survivors.

    A 737 is in final approach. The autothrottle is not responding to the selcted speed and has idled the throttle levers. The pilots don't realize of all this. The speed goes way low and they crash short of the runway with a high sink rate. While most people survives, there are fatalities including the three pilots in the cockpit.

    An Airbus (was it an A330?) is in an acceptance flight when the previous user who leased it is returning the plane to its owner. Some of the tests include flying with direct law. They loose control and crash in the sea. The handful of persons on board die.

    A Q-400 crew lets the speed go down on approach and have what should have been a non-event stickshaker activation, at a speed that was way above stall because the stickshaker had margins for icing conditions. The pilot still manages to loose control and crash. No survivors.

    A 737 is in final approach. The autothrottle fails and commands idle. The speed goes way down and the plane is abput to stall the crew commences a go-arround. The stick-shaker activates, but the crew can't keep the plane from pitching up. The plane stalls, falls and gains speed in the fall, what gives the crew enough authority in the elvator to reduce the AoA and recover. They landed uneventfully.

    An MD-10 crew let the speed go down during a high altitude hold. They had a stickshaker activation that lasted one minute until they finally recovered.

    All these TEN accidents and incidents came just out of memory. I didn't do any investigation or search. So I'm sure there must be a lot more.

    These events happened in different airplanes, different airlines, different parts of the world, and different "ages" in the evolution of aviation safety.

    They also are different in themsleves. Different chain of errors or problems in different circumstances and different phases of the flight with different reactions of the flight crew.

    And in all of them there were several opportunities, different in each case, to brake the chain of events and prevent the accident from happening, or to correct the incident in a more timely manner.

    However, they all have two things in common. Besides all the differences:

    1- A stall or aproach to stall, or what the crew considered was a stall or approach to stall, was part of the chain of events in each case.

    2- In each case, a better understanding of the stall and a propper reaction to it WOULD have prevented the accident thus saving all the lifes, or would have cut the incident at the onset and not after a more dangerous or prolonged situation developed.

    AND WE ARE STILL DISCUSSING HOW (if at all) THE ELEVATOR SHOULD BE USED IN A PROCEDURE TO RECOVER FROM A STALL OR APPROACH TO STALL?????

    I am dissapointed. BADLY!

    --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
    --- Defend what you say with arguments, not by imposing your credentials ---

  • #2
    Originally posted by Gabriel View Post
    AND WE ARE STILL DISCUSSING HOW (if at all) THE ELEVATOR SHOULD BE USED IN A PROCEDURE TO RECOVER FROM A STALL OR APPROACH TO STALL?????

    I am dissapointed. BADLY!
    Well - Gabriel - the story of the stall is as old as aviation itself. Plane gets to slow, wings stall, people die. It's as simple as that. Of course everybody tries to avoid stalls, but as long as flight depends on the speed of air over the wing surface they are about to happen now and then.
    I am just not sure what you are trying to tell us with your all-caps question quoted above.

    Comment


    • #3
      Check the FedEx near stall and the Colgan threads and you'll understand.

      By the way, an airplane can be made to stall (or not to stall) at ANY speed, because stall is not a matter of speed. Lack of understanding of this is not a lesser part of the problem.

      Quiz: You are descending through 5000ft AGL. The config is clean. Throttles are idle or almost idle. AP and AT are off. You are flying at 140 kts. Stall speed is 110 kts. Suddenly you are hit by a tailwind gust of 50 kts. You look at your airspeed indicator and your airspeed has decayed to 100 kts (that is, slower than stall speed). The plane:
      a) either is or will be stalled.
      b) very likely will stall unless you add power immediately.
      c) can easily be kept from stalling without touching the thrust levers or the config.
      d) will not stall, or will briefly stall and recover for itself, without moving any control.

      --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
      --- Defend what you say with arguments, not by imposing your credentials ---

      Comment


      • #4
        11th. A Tri Star approaches in stormy weather, is hit by a low altitude windshear, and crashes short of the runway. Only a handful of survivors.

        --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
        --- Defend what you say with arguments, not by imposing your credentials ---

        Comment


        • #5
          Originally posted by Gabriel View Post
          Check the FedEx near stall and the Colgan threads and you'll understand.

          By the way, an airplane can be made to stall (or not to stall) at ANY speed, because stall is not a matter of speed. Lack of understanding of this is not a lesser part of the problem.

          Quiz: You are descending through 5000ft AGL. The config is clean. Throttles are idle or almost idle. AP and AT are off. You are flying at 140 kts. Stall speed is 110 kts. Suddenly you are hit by a tailwind gust of 50 kts. You look at your airspeed indicator and your airspeed has decayed to 100 kts (that is, slower than stall speed). The plane:
          a) either is or will be stalled.
          b) very likely will stall unless you add power immediately.
          c) can easily be kept from stalling without touching the thrust levers or the config.
          d) will not stall, or will briefly stall and recover for itself, without moving any control.
          Hooray captain contradiction.

          Comment


          • #6
            Originally posted by JordanD View Post
            Hooray captain contradiction.
            You're right. Make those "stall speed" a "nominal stall speed", "flight manual stall speed", or "1G stall speed".

            I hate the term "stall speed" unles it's very clear exactly what we are talking about, and then I still hate it. The term "1G stall speed" is much better.

            --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
            --- Defend what you say with arguments, not by imposing your credentials ---

            Comment


            • #7
              12) December 22, 1996, Airborne Express DC-8-63 crash in Narrows, Virginia.
              The aircraft was on a functional evaluation flight following major modifications and a “C” check. The crew was conducting a stall speed test at 13,600 feet when they noted a stall without the stick shaker. The crew only applied power to recover from the stall but maintained aft column. The aircraft did not recover from the stall. It developed a roll oscillation during the stall departure and the control column remained aft for the entire descent and was further aft than at stall entry for most of the period. All six people on board were killed and the aircraft was destroyed on ground impact.

              Comment


              • #8
                Private Pilot perspective:

                Your very first lesson: Here is a stall, these can happen if you go too slow and get the nose too high, or in a few other instances like enhanced G-forces. Stalls have caused a lot of crashes. You recover by lowering the nose and adding power.

                Second flying lesson: See above.
                About 1/3 of all of your flying lessons: See above.
                Private Pilot checkride: See above.
                BFR: See above.
                Unofficial check out to rent a light plane: See above.
                You get a commercial ticket: See above (and do a spin!)
                You take your instructor checkride to teach at the puppy mill: See above.
                You get students at the puppy mill and give them their first lesson: See above.
                1/3 of the lessons you give to the puppy mill applicants: See above.

                Gabriel lists 10 crashes......where somehow, no one can remember one of the most basic aerodynamic, airmanship concepts, which if you have forgotten.....see above.

                The only other thing- is that a whole lot of commercial stall training tells professional pilots "vehemently", not to lower the nose. Still, critical AOA does not seem to be that tough of a concept or something that is prone to be forgotten.
                Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

                Comment


                • #9
                  Which commercial training tells the pilot not to lower the nose? I have never seen a recovery from stall that does not tell you to reduce the angle of attack.

                  The line about "Adjust pitch as required" usually accompanies the APPROACH to stall technique, which is far, far different from a stalled aeroplane.

                  One is an out of control (but recoverable) situation. The other is a perfectly controlled, inside the normal flight envelope situation where normal flight techniques need to be used.

                  Comment


                  • #10
                    Wow, as a layman I'm really impressed with how dangerous an airplane is as a way to travel. Which makes it all the more miraculous that so few crash and so few people die. I am guessing it is all thanks to engineering.

                    I've never looked up the definition of "angle of attack", but I've assumed (there's that word!) it has to do with how the wings attack the air. If that's the case, I'm now wondering why the whole PLANE has to change in order to optimize the angle. Has it ever been attempted to adjust the wings only? I'm not any kind of engineer, obviously, so I can anticipate a bunch of engineering challenges that explain why fixed wings are still fixed (I'm of the vague impression that helicopter rotor blades allow adjustment of angle of attack).

                    This thread might be more educational than any other (though I suppose a person could check out a book on aeronautical engineering, instead)

                    Comment


                    • #11
                      Originally posted by MCM View Post
                      Which commercial training tells the pilot not to lower the nose?
                      No disagreement with most of your comments. On another board, Gabriel and I have gotten a little flack from more than one individual over the "lower the nose" comments.

                      We are told that swept wing aircraft develop a high sink rate when AOA is reduced.

                      Further discussion of this becomes difficult: If you are short on altitude and are on the verge of a stall- there is no argument that critical AOA management with an immediate power up is probably called for with "no" reduction in nose-up attitude.

                      If you really and truly stall....no argument with what you say MCM- but I don't know that we have gotten much agreement from some other folks.

                      Still- Gabriel and I get worked up over stuff like Colgan which you could almost call an accelerated stall, Pinnacle where dudes SAT THERE AND WATCHED with a 20-degree ANU, decaying airspeed, stall and a subsequent (and predictable) flame out.

                      I do not neccesarily see eye to eye with Gabriel on the Detroit flapless MD-80- so little time to analyze crazy behavior you've never seen befor and fighting to keep the plane airborne....but I have to wonder about the Madrid flapless MD-80 with it's 15K ft runway.

                      By the way, I think Gabriel alluded to Delta 191 L-1011 windsheer which arguably was pilots who kept the nose too low.
                      Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

                      Comment


                      • #12
                        Originally posted by EconomyClass View Post
                        Wow, as a layman I'm really impressed with how dangerous an airplane is as a way to travel. Which makes it all the more miraculous that so few crash and so few people die. I am guessing it is all thanks to engineering.
                        You don't have a very high opinion of the hundreds of thousands of decent commercial pilots out there do you (we tend to discuss just the tiny percentage who remove or try to remove themselves from gene pool). Or the Air Traffic controllers, or the groundstaff that design, produce, repair and service the aircraft and the list goes on.

                        Comment


                        • #13
                          Originally posted by EconomyClass View Post
                          Wow, as a layman I'm really impressed with how dangerous an airplane is as a way to travel. Which makes it all the more miraculous that so few crash and so few people die. I am guessing it is all thanks to engineering.
                          Originally posted by SYDCBRWOD View Post
                          You don't have a very high opinion of the hundreds of thousands of decent commercial pilots out there do you (we tend to discuss just the tiny percentage who remove or try to remove themselves from gene pool). Or the Air Traffic controllers, or the groundstaff that design, produce, repair and service the aircraft and the list goes on.
                          Well, SYDCBRWOD, EconomyClass doesn't have a very high opinion of anybody... *lol... at least that's the impression one can get when following his posts here...

                          Comment


                          • #14
                            Gabriel - I am still not sure, what you are trying to tell us with a list of various aircraft accidents (not all of them related to the aircraft being stalled) and all these different terms referring to different kinds of stall.
                            I should correct myself - when I said "Plane gets to slow", what I really meant was "Air over plane's wings gets to slow". I guess we all know about stall, all pilots try to avoid them, some get into one for various reasons and not all of them manage to recover. Simply pushing the stick forward doesn't necessarily help if you aree just a few feet off the ground like the guys in Detroit and Madrid.
                            So - where should this thread lead?

                            Comment


                            • #15
                              Originally posted by ATFS_Crash
                              I’m still not sure what your geting at either Gabriel.
                              Thank you, ATFS_Crash... I am glad I am not the only one

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