Interesting 717 stall video

Discussion in 'The Powder Keg' started by TXplt, Oct 1, 2020.

  1. TXplt

    TXplt Gun Toting Boeing Driver Forum Contributor

    A stall is where the wing loses lift due to a high angle of attack (usually because you're too slow for the wing to fly at the G loading you're asking it to maintain); if aggravated the airplane can roll (largely due to asymmetric lift, yawing moments, and loss of control effectiveness. An airplane usually loses control effectiveness in the order of ailerons, elevator, and rudder and they come back in reverse order. Also, one side of the wing might reach a stall AOA before the other adding a rolling moment).

    Pilots train to stall characteristics and recovery on lighter aircraft and it's a basic skill of handling. Larger airplanes aren't typically stalled (due to undesirable characteristics around the stall). But understanding stall recovery and high AOA maneuvering is a very basic part of becoming and being a pilot. It becomes especially important in fighters because maneuvering here max performs the airplane and can be the difference between winning and losing a close in fight.

    Several commercial aircraft (and many lighter ones) have been lost due to improper action during the stall (you need to unload--push or relax pressure forward to unload the wing and get it flying again while adding thrust). If you pull back instead the airplane can go into some pretty impressive post-stall gyrations.

    I stumbled across this on the internet and found it fascinating (it appears to be a flight test of the 717--a small-ish to medium size airliner about the same size as the older DC-9s). What struck me is the rate at which the airplane rolled (this is an airliner rolling over--rather quickly--while test pilots were trying to address some potential dodgy stall characteristics). The nose pitches down alot more than I'd personally want (once the wing gets flying it's better to roll to the nearest horizon--even if you're inverted--rather than let the nose get buried too far--but you ALSO have to make sure the wing's flying and your control inputs won't further aggravate the stall) -- but they're the ones who would have known the flight characteristics and airplane much better than I. And were actually there.

    A bunch of warning horns are going off; they're at medium altitude so you can ignore the 'Altitude' one. But the clacker and apparent 'overspeed' one would get my attention in that you have to be very careful when pulling that you don't break the jet.



    Interesting ride. If the sim is to be believed, the 777 has excellent and relatively straightforward stall characteristics and I've never seen it do anything like this. Then again, I'm not sure how accurately the computer tapes replicate what the airplane actually would do at high AOA.

    (the lever on the left side of the throttles the left seat pilot pulls and the right seat pilot re-stows after the event are the speed brakes which were used to apparently mitigate the overspeed event that happened as the nose pitched downward quite a bit after the roll).
     
    Last edited: Oct 1, 2020
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  2. ChaZam

    ChaZam G&G Evangelist Forum Contributor

    That would make me need fresh underwear probably...
     

  3. Ten Man

    Ten Man G&G Evangelist

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    With the amount of time it takes to recover, it's very easy to see WHY that would be FATAL at the altitudes it is most likely to happen.
     
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  4. rando

    rando G&G Evangelist Forum Contributor

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    I cant imagine keeping your composure and staying calm while all of that is going on. Seems like so many things you have to do in a certain order and time demanding. Then get it all done before plane crashes, rolls or spirals while bells and alarms have your heart pounding. Those pilots were awesome. Thanks for the video and description J.J. Even though I didnt understand half the terminology you spoke LOL.
     
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  5. Ten Man

    Ten Man G&G Evangelist

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    Not ALL pilots are that composed when it happens. A high nose entry stall is commonly performed as the entry for a spin.

    This video was made of the jet pulling the nose high, as in a climbout from a runway takeoff. The nose was too high for the airspeed, so the wings lost lift, and the nose pitched down as the aircraft quickly rolled inverted.

    USAF Pilot Training used to be the number one "Spin Training" program around, when T-37s were the trainer jet. It was designed for spin training. Of course, it was practiced at altitudes above 20,000 feet, and the small trainer jet was much more maneuverable than an airliner.

    I have seen some pilots get VERY agitated by spins, both military AND civilian. It can be unnerving for some folks. LOL!!

    T-37
    T-37 in Flight.jpg
     
    Last edited: Oct 1, 2020
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  6. TXplt

    TXplt Gun Toting Boeing Driver Forum Contributor

    We did this alot in the military and do some of it in the civil airline world (at least in the sim) but what kinda caught me off guard in the video is how quickly the larger airplane rolled over. The 777 characteristics (at least as replicated in the sim) as opposed to the 717 in the video are fairly benign with alot of buffet and the airplane fully controllable in and out of the stall (with little tendency to roll and the rolling being easily controllable so long as the controls aren't mishandled).

    We would teach (at least in smaller airplanes) as the nose went below the horizon (and you got flying speed back) to roll from inverted to the nearest horizon (where you might have to push forward slightly if you're still upside down) to preclude the nose from pitching down quite that much losing altitude and having speed come up -- but for a larger airplane this sure happened quick and it looked like one helluva ride -- they sure did well under the circumstances and it was fascinating to watch. The shaking during the recovery might have been due to the overspeed and/or buffeting from loading up the wing during the recovery (airflow detaches from the wing and the wake smacks the tail). The kinda tricky part in the larger airplanes is having enough pull in the recovery (when you're upright) to minimize altitude loss while still keeping the wing flying (the wing will stall at a higher speed when you load it up to more than 1 G so finding that 'tickle' point right before it stalls again is a training and feel kinda thing; one in which the newer generations of fledging pilots don't get alot of in the larger airplanes). Or if you do wind up going inverted/excessively nose down (with high speed and plenty of flying speed for the wing--which might happen in something like a thunderstorm upset) not pulling so hard (while you're headed down towards the ground) that you break the airplane apart.
     
  7. animalspooker

    animalspooker G&G Evangelist

    My father was in a plane that seated around 10 one time and it stalled unexpectedly. Story is they fell ~5000' before regaining control. I can not imagine how that must've felt. I'm with ChaZ on the 'underwear' comment!
     
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