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Thread: N13HP down?

  1. #31

    Default Re: N13HP down?

    As Dudewanarace stated above, When Oil pressure is lost in the prop (Whether engine supplied (Hamilton Standard) or internal (Aeroproducts)) The blades go to the flattest pitch possible. This overspeeds the engine as the prop is not taking a big enough bite to produce a load, Causes an insane amount of drag and produces minimum thrust. Reducing power does nothing to slow the overspeed. Imagine a windmill in a hurricane. There things that can be done mechanically to the prop which can partially alleviate this however as with everything there are downsides in day to day performance.

    I never saw the event but I heard that when Whittington lost the governer in PM many moons ago it was like throwing an anchor and a drogue shoot out the back. He was lucky enough to fly it to the crash site and walk away. I do know that the current crew in their awesomeness has installed a feather pump.

    In the case of N13HP I believe the pilot was faced with a worst case scenario, he had no power, no altitude, no airspeed. I am sure the instructor did all he could to help.

    I feel for his family and friends.

  2. #32
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    Default Re: N13HP down?

    I would think the pitch limit stops would not allow the prop to go "flatter" than the "max rpm" setting which is usually used at the initial takeoff roll.

    There would be no need to have a setting that is useless......which is why stops exist in the first place.

    I'm wondering if they pulled power to save the engine, found it not enough, added power and the torque rolled the plane over.

  3. #33
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    Default Re: N13HP down?

    Quote Originally Posted by IcePaq View Post
    I would think the pitch limit stops would not allow the prop to go "flatter" than the "max rpm" setting which is usually used at the initial takeoff roll.

    There would be no need to have a setting that is useless......which is why stops exist in the first place.

    I'm wondering if they pulled power to save the engine, found it not enough, added power and the torque rolled the plane over.
    I don't think you understand constant speed props. Read my post again. Maximum rpm is not a specific blade angle. It is a variable based on power output, forward speed, etc, controlled by some sort of governor.

    The blade pitch stop is not useless.

    I think it is very likely he reduced power to save the engine. But, if the prop has run away, when you add a huge amount of power, it isn't going to generate thrust, or in your scenario torque, to roll the plane. The prop is just going to spin up and do very little but over-rev the engine.

    I don't know if your a pilot or not, but you should really fly behind a constant speed if you haven't before. It will change your opinion.

  4. #34

    Default Re: N13HP down?

    Quote Originally Posted by IcePaq View Post
    I would think the pitch limit stops would not allow the prop to go "flatter" than the "max rpm" setting which is usually used at the initial takeoff roll.

    There would be no need to have a setting that is useless......which is why stops exist in the first place.

    I'm wondering if they pulled power to save the engine, found it not enough, added power and the torque rolled the plane over.
    Quote Originally Posted by Juke View Post
    I figure just adding more power would throw the plane inverted..if not experienced ?
    I know its hard to get your brain around what a constant-speed prop does when it "goes flat,"... but what it basically means is that it is no longer POSSIBLE to "add power." You can add RPM until the jugs fly off, but the prop can't "bite" the air and deliver any power, nor can it alleviate the drag.

    You can go looking for an automotive analogy all you want- slipping clutch, broken driveshaft, etc... but there's none that is complete because of the sudden disconnection of the engine from the air COMBINED with the sudden increase in drag of the propellor. A CVT transmission suddenly moving from 1:1 to its maximum numerical ratio while you're cruising on the highway is as close as I can get.


    As for why the stops aren't set with a significant amount of "bite" permanently fixed in: the time when minimum pitch is needed is not really the start of the takoff roll, its during landing- at least for most gasoline-engined constant-speed prop aircraft. There are times when a pilot WANTS to use the prop as a brake- not literally reverse thrust the way modern turboprops can deliver, but maintaining a higher RPM setting and then closing the throttle produces a flatter pitch than would ever be used to accelerate the airplane. The closed throttle causes enough engine braking to keep the flat pitch from overspeeding the engine, and the flat pitch provides a lot of aerodynamic braking during landing. Basically it gives throttle position a lot more authority over the instantaneous acceleration/deceleration of the aircraft than would be available if the pitch travel were limited further from "flat." Its not even something that the pilot has to consciously "do." Just leaving the RPMs high and pulling throttle does it through the magic of the governor. That's one characteristic of diesel powered aircraft that keeps getting written up in articles about them- since a diesel doesn't have as much engine drag as a gas engine (no throttle), flat pitch would greatly overspeed a diesel and generally IS locked out by pitch stops so they lack the aerodynamic braking of their gasoline counterparts.

    Granted- as to whether or not that's an issue with the Sea Fury or not, I may well be talking out of the wrong orifice and the warbird pilots here would have to answer that. But given the size and weight of the machine I would think that it is a factor, and permanently disabling flat pitch would make it more of a handful to land than it already is.

    And since I just read the initial report... dear God! My sincerest condolences to the instructor who was flying alongside... that has to be absolutely devastating, and of all the people other than the pilot's family, my heart goes out to him most of all. I am so, so, sorry.
    Last edited by 440_Magnum; 03-24-2014 at 02:24 PM.

  5. #35
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    Default Re: N13HP down?

    To the two dudes above.

    I got my A&P and pilots license 31 years ago when we still trained on the engines and engine families and prop families used in the plane being discussed and don't need to do internet research on them because the knowledge was with me before I ever connected to the internet.

    There is no reason to set prop stops outside of "useful pitch".

    Having rebuilt plenty, I think I know how they work.

    I don't think the pilot did, though........and the one event we attended where he was present saw him parking his jet 100 yards from the finish line of a mile race where cars were passing by at 260+mph.

    We parked behind or beside the start line with the rest of the people who understood the physics of cars passing by at 400 feet per second only 100 yards away is a recipe for disaster.

    I wanted to visit his area but self preservation kept me on the "safe end" of the track.

    Draw your own conclusion.
    Last edited by IcePaq; 03-30-2014 at 08:23 AM.

  6. #36
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    Default Re: N13HP down?

    "There is no reason to set prop stops outside of "useful pitch".

    IcePaq I agree, I just don't understand why the low pitch stops would be set so its impossible to fly to a safe landing spot.

    The minimum pitch should be set for a speed above stall at some power setting.

    I'm scared to fly my Cessna 185 now. What if?
    Brad
    Windy Hill GA83

  7. #37

    Default Re: N13HP down?

    Quote Originally Posted by IcePaq View Post
    To the two dudes above.

    I got my A&P and pilots license 31 years ago when we still trained on the engines and engine families and prop families used in the plane being discussed and don't need to do internet research on them because the knowledge was with me before I ever connected to the internet.

    There is no reason to set prop stops outside of "useful pitch".

    Having rebuilt plenty, I think I know how they work.

    I don't think the pilot did, though........and the one event we attended where he was present saw him parking his jet 100 yards from the finish line of a mile race where cars were passing by at 260+mph.

    We parked behind or beside the start line with the rest of the people who understood the physics of cars passing by at 400 feet per second only 100 yards away is a recipe for disaster.

    I wanted to visit his area but self preservation kept me on the "safe end" of the track.

    Draw your own conclusion.

    So I guess what my conclusion from your post is because he parked, what you considered, too close the action at an automobile race he couldn't understand the workings of a constant speed prop and therefore was incompetent to possibly fly a Sea Fury. OK?
    Last edited by wyhdah; 03-30-2014 at 03:37 PM.

  8. #38
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    Default Re: N13HP down?

    [QUOTE=IcePaq;117962]To the two dudes above.

    I got my A&P and pilots license 31 years ago when we still trained on the engines and engine families and prop families used in the plane being discussed and don't need to do internet research on them because the knowledge was with me before I ever connected to the internet.

    There is no reason to set prop stops outside of "useful pitch".

    Having rebuilt plenty, I think I know how they work.

    I agree. I found this in my old power plant study guide circa 1990 " The low pitch stop on a constant-speed propeller is usually set so that the engine will turn at its rated takeoff RPM at sea level when the throttle is opened to allowable takeoff manifold pressure."

  9. #39
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    Default Re: N13HP down?

    Quote Originally Posted by Comanche View Post
    I agree. I found this in my old power plant study guide circa 1990 " The low pitch stop on a constant-speed propeller is usually set so that the engine will turn at its rated takeoff RPM at sea level when the throttle is opened to allowable takeoff manifold pressure."
    I agree, but like I said in one of my original posts, the blade is only on the stop for a very short time. Once you start building forward speed, the rpm will increase because of the reduced blade angle of attack, then the governor will adjust the blade angle of attack to keep constant RPM. So, the blade is off the pitch stop at that point, and for the rest of the flight, probably..

    The more high performance you get, and Experimental you get, the pitch stop tends to mean less and less. If I were to do a full power takeoff, I bet the blade is off the stop by the time I reach 15" manifold pressure, with 15" to go.. So like the first 3 seconds of the takeoff roll..

  10. #40

    Default Re: N13HP down?

    Quote Originally Posted by IcePaq View Post
    I don't think the pilot did, though........and the one event we attended where he was present saw him parking his jet 100 yards from the finish line of a mile race where cars were passing by at 260+mph.

    We parked behind or beside the start line with the rest of the people who understood the physics of cars passing by at 400 feet per second only 100 yards away is a recipe for disaster.

    I wanted to visit his area but self preservation kept me on the "safe end" of the track.

    Draw your own conclusion.
    Hey IcePaq,

    Tell us more about your Sea Fury Expertise.
    "the Pilot" wasn't the pilot of his jet.
    GFY.

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