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Setteling w/ Power

Discussion in 'The Okie Corral' started by Wulfenite, Jul 14, 2004.

  1. Wulfenite

    Wulfenite The King

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    I was reading an old Flying the other day, specifically their "What I learned about flying from that....."

    The article was written by an Army Helo pilot who was demonstrating a setteling w/ power manuver. The article suggested that the lesson of the manuver was that you shouldent decend vertically more than a couple feet cause you can get trapped in a bubble of air thats decending an loose your lift.

    Then today I was watching Jurasiac Park, scene where everyones flying out to the island in the Augusta. The manuver into a steep sided box canyon and decend vertically several hundred feet to a pad.

    Got me wondering if this was movie magic or if there's a way to do that safely, or is it a special circimstance when you're boxed in or what?
     
  2. M2 Carbine

    M2 Carbine

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    Hi Wulf, it's me again with another long winded explanation, but I'll tell a couple stories to make up for it.;f

    We demonstrated SP to the students in flight school.
    I've been in it bad two times that I can recall that took me to the ground.

    When hovering a few feet off the ground the air that the main rotor is "blowing" downward, of course is blocked by the ground and must exit out to the sides. This gives you a "ground effect", high pressure area, bubble of air, whatever you want to call it, between the rotor blades and the ground.
    That's one reason learning to hover, to "balance" on this ball of air is one of the hardest things to master when learning to fly a chopper.

    When hovering "out of ground effect" there is nothing to stop this downward moving column of air (for all practical purposes).

    So at a stationary hover in the air mass (no or little air speed) Your main rotor blades are creating a downward moving vertical column of air below you and drawing air in from above.

    Of course there's much more to the air movement, rotor blade action but basically if you think of the rotor blades "blowing" the air downward as they "pull" in the air from above you can see you are hovering or climbing vertically in a descending column of air and you know what this is doing to your lift.

    Within the power/pitch limits of your helicopter you can hover or climb vertically.

    BUT if, for several reasons, the helicopter drops into the descending column of air below you, you can instantly go into settling with power. (falling vertically)
    The normal reaction is to increase pitch/power if you have any left.
    This only makes you fall faster because you are just continuing the downward flow of air that you are falling in.

    To get out of SWP it takes altitude or a lot of luck if you are low.
    What you do is keep the RPM up and lower the pitch and nose of the helicopter to try and fly out of the descending air. The cyclic control is mushy because of what the main rotor is flying in.
    Also kicking the tail rotor pedal will help "skid" out of the descending air.
    You can imagine this takes altitude to recover.
    I would demonstrate it at about 3,000 feet.


    The first time I got in SWP was solo in flight school in the Sikorsky H19.
    I was about 75 foot high on final, almost no air speed, light variable wind.
    I think I got a little gust of tail wind.
    The H19 dropped into it's own downwash and SWP.
    I lowered the pitch as much as I could and rolled on throttle and thought about all that AV gas under my ***.
    Just before I hit I pulled all the pitch I could and the big bird stopped just before the wheels hit the ground.
    I couldn't believe it.
    The tower called me and asked what the hell I was doing.
    I just said, Got into settling with power.
    They said, Oh, OK.:)



    The second time I was counting Elk in Colorado and another Bell G3B1 was chasing me around making a movie for the state.
    About 6,000 feet ground elevation.

    I was about 60-70 foot high, going slow and the little Elk herd did a 180 and ran by me before the Game and Fish man got the count.

    I thought I'd show off for the camera. I pulled the nose up and did a 180 degree pedal turn.
    Immediately dropped into settling with power.
    Same thing, lowered pitch and wound up the RPM.
    I thought, well the state is going to get a crash in their movie.
    I pulled pitch a few feet above the snow but still sank in up to the bottom of the chopper. Didn't hurt anything except my pride.

    I never did see the movie.;f



    One more.

    My neighbor in Mineral Wells was a military instructor in the Hughes TH 55.
    He told me he was telling his flight commander, a Major, "The damned Hughes almost killed me today.
    I was demonstrating settling with power and the thing wouldn't recover. It went into a "falling leaf" and dropped about 1,500 feet before I could get it flying.
    The Major said that's BS there's no way it was that bad.
    Just then another instructor came in saying, Holly sh** you should have seen what I saw. A Hughes was falling like hell doing like a falling leaf."


    ;f Funny;f


    but about 50 instructors and students were killed in the Hughes.
     

  3. Wulfenite

    Wulfenite The King

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    So if you want to decend vertically, like they did in the movie, how do you do it safely?
     
  4. M2 Carbine

    M2 Carbine

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    The safest way is with airspeed from a headwind.
    If there's a wind, of course you can have some airspeed and still be operating vertically.

    But descending vertically with power can be done because you aren't using as much power/pitch in the decent as it takes to hover or climb so you aren't building that bad a column of air below you.
    Even though you are decending the decending air is still below you.

    But you could induce SWP by quickly lowering pitch and pulling it back in as you drop into the descending column of air.
    (that's one way we got into the SWP demo in flight school)

    Mostly it just comes down to having plenty of power to climb and descend vertically and keeping you out of your "downwash".

    With plenty of power a nice smooth vertical climb or decent will work.

    Like, a light loaded Sikorsky S76 would have no problem.
    A medium loaded Huey probably couldn't do it.

    BUT you have a bigger problem operating vertically than SWP.
    You will be in the "dead man's curve".

    There is a height/velocity curve in order to make a safe autorotation.

    For instance if you are hovering at 100 feet (no air speed) and the enging quits you will at least get back injuries from the vertical fall.
    It happened at work. The heliports were about 100 ft high.

    But you could be at 50 foot with 60 knots airspeed and a safe autorotation will be no problem.
     
  5. Tennessee Slim

    Tennessee Slim Señor Member CLM

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    Uncle M2, now will you teach us about retreating blade stall? ;)
     
  6. M2 Carbine

    M2 Carbine

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    No, No, No.

    I used to get paid a lot of money to teach that.



    Truth is I got paid very little money;f

    But the flying was fun.:cool:


    Wulf, This is the dead man's curve for the Bell 407.
    [​IMG]
     
  7. Wulfenite

    Wulfenite The King

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    So if I read that right anytime you're higher than ground effect and lower than a couple hundred feet you need to be doing 60 or 70 knots to autorotate. In fixed wing we call that a buzz job. Seems like doing a 70 knots at a 100 feet you're as likely to get into trouble with obstructions as you are an engine out.

    Seems like it would be pretty common for police choppers to operate inside that curve.
     
  8. M2 Carbine

    M2 Carbine

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    Ya, because of the low level requirement of many helicopter operations, a lot have hit wires, towers, etc.
    I've been lucky enough to miss wires about a dozen times.
    No probably more than that.
    They can get very sneaky where they hide wires.


    Ya, when operating in the shaded area a successful autorotation isn't impossible but very unlikely.

    Hospital, police, oil field, news helicopters are all hanging their *** out on take off and approach to a raised heliport.

    The approach isn't as bad as the TO because you can maintain as much airspeed as you can for as long as you can.

    You can see from the curve as you leave a 10 story roof top heliport with almost zero airspeed an engine failure is going to be a bugger.
     
  9. TimC

    TimC Uhavthecontrols

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    Hmmmm...^8
     
  10. Wulfenite

    Wulfenite The King

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    Good stuff Buck, thanks. I think I'm going to log an hour of ground towards my helo rating. ;)
     
  11. Texas T

    Texas T TX expatriate CLM

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    But I want to know what the F&G guy was saying/doing during this episode! ;P ;f
     
  12. M2 Carbine

    M2 Carbine

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    T,
    That guy was pretty cool.

    He had been in a Bell 47 G3B1 that had a transmission mast bearing fail.
    10,000 feet, 250 feet above the ground.
    The mast didn't completely come out of the transmission but the pilot didn't have a lot of control.
    They hit nose high, flopped down flat spreading the skids and rocked forward busting the bubble.
    The pilot and Claude the F&G man, didn't get a scratch.;P

    When He told me the details I said, You know, no one usually lives through a mast bearing failure.

    He said, I know, I've also had several other close calls and that's why I told your company I wanted you to be my pilot or I would pull the contract.

    That was the first I heard of that and I had never met Claude before.
    I found out Claude had been talking to the mechanic that was with me in Montana and Idaho.
    So a couple things that had happened days before began to make sense.

    The first day in Colorado that I was to fly Claude, we were delayed taking off.
    We were going to count Elk.

    Claude asked me how much game counting I had done.
    I told him, "The company owner wants me to BS you but the only game counting I've done is one day of looking for mountain goats East of Salt Lake City. We never found any. I know nothing about game counting. If you want to get another pilot, no hard feelings."

    To my surprise He said, "No problem. I'll teach you everything you need to know."

    We got alone great and had some interesting , fun flying.

    When I screwed up and got in SWP I was too busy to remember if He said anything, but He just took it as another day at the office.;f
     
  13. FlyNavy

    FlyNavy

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    Yep, "vortex ring state" as the Navy/Marines teach is bad news. The gouge number for the danger zone is any indicated airspeed below 40 with a descent rate over 800fpm. I think you'll usually be far exceeding these parameters to actually start falling into your own bubble. The only way out of fully developed VRS is to auto. Better hope you're high enough! A straight down elevator ride in a helo can be done, just keep your descent rate slow and smooth. We usually avoid it because it puts you in the ugly portion of the H/V diagram. Sometimes in a tight CAL zone with high trees, you do what you gotta do and roll the dice that its not your day for an engine failure. A little wind is nice, but you're gonna lose that under the tree line anyway-be ready.
     
  14. BillCola

    BillCola Supreme Cmdr ®

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    Wow. This one might get my "most learned in one thread" award of all time!
     
  15. Tennessee Slim

    Tennessee Slim Señor Member CLM

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    Oh, bruddah! We're just warming up. We haven't touched ground resonance, translating tendency, the Jeezis nut, dynamic rollover, mast bumping, yadda, yadda, yadda, .... ;Q
     
  16. BillCola

    BillCola Supreme Cmdr ®

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    I was wondering why my logbook wasn't endorsed "OK for rotorcraft" after a whole hour of dual! It's much clearer now... ;f
     
  17. Tennessee Slim

    Tennessee Slim Señor Member CLM

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    Why Helicopter Pilots are Different!
    Harry Reasoner, February 16, 1971

    "The thing is, helicopters are different from planes. An airplane by it's nature wants to fly, and if not interfered with too strongly by unusual events or by a deliberately incompetent pilot, it will fly. A helicopter does not want to fly. It is maintained in the air by a variety of forces and controls working in opposition to each other, and if there is any disturbance in this delicate balance the helicopter stops flying; immediately and disastrously. There is no such thing as a gliding helicopter.

    This is why being a helicopter pilot is so different from being an airplane pilot, and why in generality, airplane pilots are open, clear-eyed, buoyant extroverts and helicopter pilots are brooding introspective anticipators of trouble. They know if something bad has not happened it is about to."
     
  18. M2 Carbine

    M2 Carbine

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    Ya Slim,
    it doesn't help when a new aircraft checkout (Bell 407) is four days spent learning how to handle all the additional failures that can happen to this, "Aw it's just a big 206".;f
     
  19. Tennessee Slim

    Tennessee Slim Señor Member CLM

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    Allah be praised, Bell finally has discovered that 'copters with more than 2 blades can fly after all!

    I have a buddy who was a crew chief all the way back to Korea & Inchon, and he's very fond of saying, "When better helicopters are built, Sikorsky will build them."
     
  20. flyandscuba

    flyandscuba

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    The Bell 412 has four blades -- and it's been around for a looong time... Here's the one I put in service in Chattanooga.

    [​IMG]