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The fuel valve on the Robbie can be turned halfway for reduce fuel flow. It's a ball valve.

 

The thought I had there was that maybe because of reduced fuel, the engine might run rough, with less power.

 

Witch,

 

If you accidentally go too far, stall the engine, then you're dead in less than 5 seconds as your NR drops off the scale.

 

This is too much risk for me. I'd rather explore every other option and try everything until my fuel runs out!

 

Joker

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The fuel valve on the Robbie can be turned halfway for reduce fuel flow. It's a ball valve.

 

The thought I had there was that maybe because of reduced fuel, the engine might run rough, with less power. It might not be the best solution, but I figured it might be worth a try if one were desperate. All in all, it was basically a stupid idea that might just work, kinda like spilling hot coffee on yourself and suing because the coffee was too hot. Didn't some woman get a few million for that?

 

Later

Wouldn't you get the same end result by closing the throttle slightly? On top of that wouldn't the governor (if there is one) open the throttle to keep the rpm up as your closing the fuel valve?

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The fuel valve on the Robbie can be turned halfway for reduce fuel flow. It's a ball valve.

 

The thought I had there was that maybe because of reduced fuel, the engine might run rough, with less power. It might not be the best solution, but I figured it might be worth a try if one were desperate. All in all, it was basically a stupid idea that might just work, kinda like spilling hot coffee on yourself and suing because the coffee was too hot. Didn't some woman get a few million for that?

 

Later

Wouldn't that be the same as leaning the mixture?
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Wouldn't you get the same end result by closing the throttle slightly? On top of that wouldn't the governor (if there is one) open the throttle to keep the rpm up as your closing the fuel valve?

 

Closing the fuel valve is limiting supply to the carb or FI unit. If it doesn't get enough, the engine quits. A fuel valve is not in anyway a tool for controlling fuel flow. It should only be considered an on/off device. Reducing throttle will reduce the amount of properly mixed fuel and air, so it won't run rough, and it won't quit. However, reducing the throttle at high angles of attack will mean you are not likely to ever get that RPM back because you have just reduced to total available power from the engine. You wouldn't want to bank it and cone the blades to get the RPM back either. Hard banking at low rotor RPM puts you much closer to blade stall. Do one, or the other.

 

My preferences if to use forward speed and a hard slip. This will force the rotor disc at an angle and reduce your vertical component of lift. You have to be careful doing this with utility floats as you could cause a mastbump.

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Guys- this is a great thread...thanks go to LostHeliBoy for starting it.

 

I really cant believe some of the solutions presented !! Holy Crap !!

 

The goal is not to see how fast you can crash...you have to maintain full fuel flow, maintain full engine and rotor rpm...thats the whole thinking of the thread..how can you maintain those things AND get the helo on the ground. Increasing airspeed to reduce my altitude, and then slipping it to reduce speed, then a run on landing onto the runway would be my personal choice.

 

For safety let me just re state one more time here.

 

DO NOT KILL THE ENGINE, REDUCE ROTOR OR ENGINE RPM...stop the engine in a 22 without the ability to lower collective would result in an immediate rotor stall, and as stated above...your dead in seconds.

 

WOW, felt I had to get that out !

 

FLY SAFE..Keep your engine and rotor RPM ALL the time !

 

Goldy

Edited by Goldy
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To reiterate what Goldy just put (to really hammer the nail in!):

 

Yep, Goldy is right. I was possibly a little loose with my solutions in Post #21. Was just listing off the top of my head different ways to reduce lift.

 

Adjusting Fuel and RPM below the green arc are not good options in forward flight at altitude. The risk of rotor stall is too great. Follow Goldy's advice below!*

 

FLY SAFE..Keep your engine and rotor RPM ALL the time !*

 

*That being said, as I said in #21, your solution would depend on your situation (mainly the power setting you are stuck above and your current regeime of flight) and the only time I would consider manipulating RPM below the green arc as a solution would be if I had stuck collective in a hover.

 

Thanks Goldy for bringing that back up for clarification.

 

Joker

Edited by joker
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RPM has a power-on range. Manipulating it within this range is something I consider perfectly acceptable.

 

 

Rocky- you are absolutely correct. In a lot of ships, like the 300, you have a pretty good range to deal with. Have you ever seen the green arc in a 22? I think its like plus or minus 4 rpm !! ( thats a joke).

The 22 has a really narrow range of proper RPM, drop below that and you are greatly adding stresses to the aircraft. I was speaking specifically of the 22.

 

Also, I like the carb heat idea....hadn't thought of that one and I cant think of a downside..

 

Goldy

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In my Ahnold Schwarzenegger voice "Again I must clarify. It was one of a few stupid ideas and was not meant to be taken seriously. Believe me, I ain't going to be turning the fuel valve half off-carb heat or mag, maybe if I were desperate. The idea was to get the engine to slow down a little. It most likely won't work, but it might. That's all. Quick...Head for the choppa! NO, NO, THE ODHA CHOPPA!!!"

 

Later

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Question. I am not a rated pilot yet, so go easy, lol... I remember reading in the FAA R22 report that the R22 was certified with a 91% minimum MRPM and horn activation was 95%. While the Beta's have a 97% minimum MRPM at horn activation. In a REAL emergency, why couldn't you reduce RRPM to 94% or so on an approach if you didn't have max load or gusty conditions?? With the new stainless style blades it seems to be a real option in this type of emergency. Or am I missing something? Just a thought.

 

FAA R22 Accident Report, Chapter 4, on page 26. You read then decide?

FAA Report

Thanks for the discussion..

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There's an idea.

 

I seem to remember hearing somewhere that you can hover that thing down to 85% or something. Also, I seem to remember the best glide speed is 75kts at 90%. Yup, just looked it up. Anyhow, rolling off the throttle to 90% seems like a good idea, just get back up to 97% below 500'AGL.

 

I like that idea. Better than the fuel valve thingy, or carb heat.

 

Later

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Witch!

 

Ok, will accept your stupid idea as just 'carefree musing aloud', this last time!

 

Do remember though, that when some students read one of your 'carefree muses', it might just stick in their head. For that reason, I and others can't let that sort of post go by without clarification or correction in explicit manner as possible to get that thought out of the head of that student!

 

The joy of typed text, is that you have time to think about what you're saying....or you should have.

 

Nothing wrong with people being wrong or asking stupid questions. That's why we're all here. If you thought 'fuel system manipluation' was a 'stupid idea in the first place, either don't type it or expect to get flamed.

 

As I said, I never can tell when you are serious or not.

 

R22 Stall Speed was 80% +1% per 1000 foot DA

 

Carb Heat - Yes, definitely an option.

 

Joker

Edited by joker
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why is carbheat an option? it doesn't reduce the rpm as long as the governor is on, right? The manifold pressure will go up because the gov will open the throttle to maintain rpm, but what good does that do?

 

And if you are going to turn the governor off, you can just as well reduce the rpm with the throttle grip, no need to use the carb heat for that.

 

If I wanted to reduce rotor RPM because all other methods to lose altitude have failed, i'd just close the throttle slightly with governor ON.

 

 

 

Another thought: If I'm in a situation where my collective doesn't work anymore, and I don't know why, I'd be very careful doing anything with the rpm - after all, there's still the correlator connected to the throttle. If there's something going wrong down there in the collective/correlator linkages, can I be reasonably sure that the (possibly broken) correlator won't mess with the rpm when I turn the gov off?

 

please excuse any stupidity in this post - I'm a newbie (com student) myself

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why is carbheat an option? it doesn't reduce the rpm as long as the governor is on, right?

 

Not all helicopters have a governor.

 

So why not just roll off the throttle to manipulate the RPM? Good question.

 

after all, there's still the correlator connected to the throttle. If there's something going wrong down there in the collective/correlator linkages, can I be reasonably sure that the (possibly broken) correlator won't mess...

 

Like you said, there is possibly some problem with the correllator / collective / throttle linkages.

 

I suppose the carb heat is a way of reducing RPM (as a last ditch effort) without the need to manipulate correllator / collective / throttle linkages.

 

But as stressed before, messing with RPM (beyond limits of green arc) and throttle can lead to death. About the only time I'd use this option was in a hover.

 

I guess we have shown that there are so many different scenarios, and right ways of solving a problem. Even a wrong way could be a right way in another circumstance.

 

A good thread, but I guess I'm about done with it now! Next topic?

Joker

Edited by joker
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R22 Stall Speed was 80% +1% per 1000 foot DA

 

So, are you saying the blades can't stall at 100% RPM? Are you saying that during a full touchdown auto when you pull pitch, you only have 20% of useful RPM? I think Robinson put this out to scare pilots into keeping rotor RPM. But I think it is very misleading and I'd rather a pilot know more about how an airfoil actually stalls. An airfoil can stall at any speed. I can take you up in an airplane with a listed stall speed of 60 knots and stall it at 90, or fly it down to 0 without stalling it. Airfoils stall at a specific AOA, not a speed.

 

You bank a helicopter too much and pull too many g's, and the blades can stall at full RPM. This is why I stated not to make aggressive turns with low rotor RPM. It is one or the other.

 

When you do a touch down auto, glance at the RPM just as you are settling to the ground. The RPM will probably be down around 50 or 60%, but the blades have not stalled. This is because you have not encountered a strong vertical component of the relative wind from the descending helicopter. In fact, the blades never stall on a properly performed touchdown auto. Even with full up collective, you never exceed the critical AOA. You still need the upflow of air for the blades to stall.

 

The power-on range for some R22's is 97%-104%. It wasn't until the Beta did they move it up to 101%-104%

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ANOTHER STUPID THOUGHT !!!

 

I'm wondering how slow one might get the rotor and still be able to hold a hover of two feet?

 

Later

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Great thread.

 

I used to teach this when I was doing primary instruction. I always favoured the get behind the power curve method. it's not actually as complicated as it sounds. Reduce speed and you climb, but eventually you will start to descend. Be aware of the airspace above you!! As with the majority of helo problems take your time and think about what you are doing. (except if the engine has quit or you have a catastrophic failure!)

 

As far as manipulating the rotor rpm with throttle I always viewed that as not being a problem, just remember again take your time. Most helicopters will continue to fly way below the green arc.

 

As for Witch's question I hovered a 407 the other day at about 67% before it gave up and we touched down.

 

As for an R22 or 300 I couldn't tell you.

 

Do not go out and try this if you're not 100% certain of what you're doing!

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ANOTHER STUPID THOUGHT !!!

 

I'm wondering how slow one might get the rotor and still be able to hold a hover of two feet?

 

Later

 

You will start to run out of power on most helicopters before the blades stall. The lower your RPM, the lower you total available power is.

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ANOTHER STUPID THOUGHT !!!

 

I'm wondering how slow one might get the rotor and still be able to hold a hover of two feet?

 

Later

S300C with 2 people and 25 gal of fuel will hover no problem at 2500 RPM, normal operating range below 500 feet is 3000-3200. Feels funny though to sit with the collective up under your arm, and the left foot mashed all the way forward as the slow RPM takes away a lot of tail rotor authority.

 

If my memory serves me right, I think we hovered an R22 at about 80% before it descended to a touchdown....it's been a while though so i might be off on that one.

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AWESOME replies

  • I am NOT the definitive master of this subject but I have enjoyed the various replies
  • and there are some good ideas out there..
  • BUT
    NEVER close the fuel valve ..
  • Never
    purposely LOOSE RPM Rotor or other wise..
  • carb heat is a good start in a piston heli.. it increses the MAP by as much as 1 1/2 inches in a R22
  • more stories and info needed.
     

    You Guys/Gals Rock!!



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AWESOME replies

  • I am NOT the definitive master of this subject but I have enjoyed the various replies
  • and there are some good ideas out there..
  • BUT
    NEVER close the fuel valve ..
  • Never
    purposely LOOSE RPM Rotor or other wise..
  • carb heat is a good start in a piston heli.. it increses the MAP by as much as 1 1/2 inches in a R22
  • more stories and info needed.
     

    You Guys/Gals Rock!!



 

Loose RPM is a bad thing. I like mine nice and tight. LOL

 

The only way carb heat increases manifold pressure is if you have ice formed. The manifold increases when carb heat is applied because the throttle opens more to maintain RPM. Carb heat will reduce RPM if the governor is not on which will cause MAP to rise slightly, but not 1.5 inches.

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AWESOME replies

  • I am NOT the definitive master of this subject but I have enjoyed the various replies
  • and there are some good ideas out there..
  • BUT
    NEVER close the fuel valve ..
  • Never
    purposely LOOSE RPM Rotor or other wise..
  • carb heat is a good start in a piston heli.. it increses the MAP by as much as 1 1/2 inches in a R22
  • more stories and info needed.
     

    You Guys/Gals Rock!!



 

 

The R22 POH states that you abide by the limits on the Instrument (tach) installed per Regulations.

Beta models had 97-104% power on MRPM safe range and Beta II's have 101-104% power on MRPM safe range.

Both have the same Blades, -4 type or newer.

 

AIM 6-1-1 and 91.3 says you can deviate from part 91 normal rules in an emergency.

 

So, if in my Beta II, if my collective is stuck and the gov is working normally, I will over ride the gov or turn it off if need be, to fly manual throttle, if I can't get it to descend using shallow banking turns to get to a area where I can get it slowed down enough to do a hover taxi type auto or run on landing, depending on the amount of room I have to work with and conditions. I have flown complete patterns with the gov off, no big deal. I think you would still use the carb heat, if needed, to keep the gauge out of the yellow. If you just use carb heat you will lose power and torque, right? So, the end result is less ERPM and RRPM, no? When I fly with a CFI thats around 200 and I am at about 200 we turn off carb heat under 100 agl on HOT days, so we have enough power to arrest the descent and a little extra power going into a hover after the approach. The biggest factor in this supposed stuck collective, is how much pitch are we pulling when the thing sticks? Are we in normal climb, approach, or cruise flight..

 

I wonder why the R22 does not have a Stuck Collective procedure in Section 3? All I can find in Sections 2,3, and 4 is keep rpm at min of 97% under 500 feet. I think this is a very good thread, because the fact there is no procedure in the R22 POH. It gets everyones views and get you to thinking about ALL possible combinations of techn's to get it down safe as possible.

 

Thanks a bunch to all that responded.

Mechanic

 

P.S. RockyMountainPilot, thanks for the spell cheker...lol

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ANOTHER STUPID THOUGHT !!!

 

I'm wondering how slow one might get the rotor and still be able to hold a hover of two feet?

 

Later

 

I used to demonstrate that to students back when I was a CFI. They would always freak when they got the low rotor RPM, wrap the throttle around, and usually overspeed. So I we would hold a two foot hover and do some SLOW taxing at 90%, then 80%, then drain it down from there. The R22 will still hold its hover at ~70%, but will sink the second you move the cylic in any direction. MP is just below ambient the whole time.

 

In retrospect, I probably shouldn't have been doing that. When I started flying turbines, I heard fair warnings about people who forgot to open the throttle all the way, and tried to lift to a hover a flight idle. Massive overtorques, especially if they tried to roll the throttle open after they learned of their mistake. Entire rotor system and engine gets replaced, ouch!! So if MP is truely an "indicator" of the respective torque, then I shouldn't have been doing what I was doing. But that's what my instructor taught me, so I never really thought anything was wrong with it.

 

A few other notes.......RHC claims that they got the RRPM down to 74% at VNE and Max gross Weight during testing without stalling.

 

Also, one trick I was taught in stuck pedal ops, stir the cyclic at a hover to destroy the lift if you can't lower the collective/reduce throttle. That might be applicable in the stuck collective discussion somewhere.

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