STUCK Collective

[LostHeliBoy]

STUCK COLLECTIVE

• Why is it something that is not covered in a training environment?
   
  
• What have others heard about this possibly career ending phenomon?
   
  
• What solutions or procedures have people done or recommended?
   
  
• Turbine Vs. Piston
   
  
• Power Required & Power Avialable Topics as relates to this..
  

[KMWK]

They covered it during Army flight school back in the day. We were taught to control altitude with power. Shallow approach to a run on landing.

 

[Superman]

I think it was during my commercial training that my instructor looked over at me while in level cruise flight, smiled and said "your collective has just jammed, how ya gonna land this thing?"

 

I'll give ya the rest of the story after I see what some of you have to say about it. If you want to hear it that is.

 

If its not being covered in training now....it should be.

 

Clark

[Pogue]

They covered it during Army flight school back in the day. We were taught to control altitude with power. Shallow approach to a run on landing.

And if you're limited by rotor rpm you can bank it and point the nose enough down to get a circling descent going.

[flyby_heli]

I do to my commercial students what Superman's instructor did to him....you will not believe how many different and often scary suggestions of how to get "safely" on the ground i've heard!

 

Some of them are:

 

"We can just roll of throttle and enter an auto..." ------- "YOU WANNA DO WHAT? what will happen to your RRPM???" -------"Oh, sh**, I didn't think about that"

 

"Nose it over and start descending..." -------- "OK, but how will you slow it down without gaining altitude??" -------- "EEEHHHHH you could fly really low and fast over water and trim it away from you and jump out the side" --------- "Like a high speed, high risk ditching you mean??" -----" Yeah, exactly..." ------ "OK, I'll leave the call to the insurance agent in your hands after that one!!!!"

 

"Nose over for descent and do a really high speed running landing and then roll of throttle" -------- "OK, what's the limitation on the landinggear as far as airspeed goes for running landings?" --------- "EEEHHH, I know i read it somewhere in the POH, but i forgot..." ----- "36 knots" ----- "I guess that will not work either then" ----- " I guess not!!"

 

 

These are some of the replies I've had. I'll share my technique after a bit unless someone else mentions it first.

Edited June 26, 2007 by flyby_heli

[Linc]

If it happens at a normal cruise setting, slow the aircraft. It will climb, until you drop below the minimum airspeed for that power setting (basically, below ETL), then control rate of descent with airspeed to a running landing, rolling the throttle off once the skids are on the ground. If necessary, a landing to a spot can be accomplished, but the landing will be a bit rougher and the timing on the throttle more critical.

 

I have demonstrated this concept a couple times to a few of my copilots without touching down, without manipulating the throttle...I am not an instructor pilot, and it is not an established task, but it can be effectively demonstrated within the normal flight envelope. Once, I demonstrated it to a copilot on a fairly windy day. The appropriate airspeed to generate the descent was actually a ground speed in the opposite direction.

 

I haven't quite figured out how I would do it if the collective was stuck at a HOGE power setting.

Edited June 26, 2007 by Linc

[Goldy]

Personally, I would just slide my fat butt over on top of the collective...it will go down, guaranteed. 245 pounds plus leverage can even overcome the worst of em....

[PhotoFlyer]

If it happens at a normal cruise setting, slow the aircraft. It will climb, until you drop below the minimum airspeed for that power setting (basically, below ETL), then control rate of descent with airspeed to a running landing, rolling the throttle off once the skids are on the ground. If necessary, a landing to a spot can be accomplished, but the landing will be a bit rougher and the timing on the throttle more critical.

 

I have demonstrated this concept a couple times to a few of my copilots without touching down, without manipulating the throttle...I am not an instructor pilot, and it is not an established task, but it can be effectively demonstrated within the normal flight envelope. Once, I demonstrated it to a copilot on a fairly windy day. The appropriate airspeed to generate the descent was actually a ground speed in the opposite direction.

 

I haven't quite figured out how I would do it if the collective was stuck at a HOGE power setting.

 

I teach the same technique. Usually I demonstrate this at the private level, and have my commercial/CFI students perform the landing to a touchdown.

 

HOGE is actually fairly easy, but it takes a long time to get down safely. While in a OGE hover reduce RPM to the minimum flight RPM. Control the descent rate with throttle. Keep it REALLY slow to prevent settling with power, and be prepared to get airspeed at the slightest hint of settling. It will take a REALLY long time to get down, but it works. When you enter ground effect you will have to reduce RPM below the green arc to land.

[jsmith13]

LOL Goldy, you always solve 'em!!

Edited June 27, 2007 by jsmith13

[RotorRunner]

Goldy: I don't want to hijack the thread, but I thought 240 was the seat limit in a R22. D you fly one at 245? If that works, I might have to give one a shot. I always fly a 300c.

Edited June 27, 2007 by RotorRunner

[LostHeliBoy]

If it happens at a normal cruise setting, slow the aircraft. It will climb, until you drop below the minimum airspeed for that power setting (basically, below ETL), then control rate of descent with airspeed to a running landing, rolling the throttle off once the skids are on the ground. If necessary, a landing to a spot can be accomplished, but the landing will be a bit rougher and the timing on the throttle more critical.

• Excellent this is the Power required curve soultion.. more in part two.
   
  
• APPLY CARB HEAT
   
  
• FIRST
  Attempt is to circle to decend which would increase the power required ..
  The increase would be caused by the additional load factor as you Spiralled tighter and tighter. the tighter the turn the more load factor and the more need for power to keep at the same altitude , if no additional collective was used a decent would occur.. then apply the other theory
   
  
• then SECOND;
  Apply the above mentioned theory using aft cyclic to drop on to the back part of the curve and then start thinking about the power changes to get your precious butt on the ground using the throttle
   
  
• the power changes are NOT an easy thing to learn, but, you can mentally practice them while sitting in traffic waiting for the lights. Pretend that if you hold the throttle and point your finger down, the nose of the helicopter will turn in the direction of the pointed finger after you roll on or off the throttle.. .
   
   
  
• If you have questions about the graph below cousult "the Princples of helicopter flight" by W.Wagentdonk...Or your instructor.
  

 

Any thoughts?

 

I liked Goldy's soultion Bad placement if you get caught thought.

Better graph with a better search when I'm not at work..

Edited June 27, 2007 by LostHeliBoy

[Goldy]

Goldy: I don't want to hijack the thread, but I thought 240 was the seat limit in a R22. D you fly one at 245? If that works, I might have to give one a shot. I always fly a 300c.

 

 

240 is the max. I havent flown the 22 in a month or so, been in the 44....which doesnt care up to 300 pounds. I'll take off a few pounds and go up in the 22 again soon, Unless our B47 comes back on line, then screw it...for an extra 40 bucks an hour, I would rather fly the 47 with a lot more safety factor and load capacity.

 

The 22 does fine with 250 plus pound guys. Even the WB can handle some extra pounds, its the seat crash rating that ends at 240, and of course, your insurance in a crash if you exceed it. BTW- I dont endorse anyone exceeding any flight POH limits, especially in a 22, which is why I havnt been flying one lately! ( too many ice creams )

 

Goldy

Edited June 28, 2007 by Goldy

[RotorRunner]

Thanks Goldy.

[Gomer Pylot]

If you want to come down fast, you can try getting into VRS, which will increase the descent rate rather quickly. Probably won't work, though, unless the conditions are just right. That certainly wouldn't be my first, or hundredth, choice. In any case, this malfunction calls for good technique, and fortunately it's rather rare - in 40 years of flying, I've never heard of it actually happening. Everything is possible in a mechanical system, so it's probably worthwhile to occasionally do thought experiments on solutions to various malfunctions.

 

Depending on where the collective is stuck, you may be able to descend by merely increasing airspeed. This would be the first thing I would try, because you need airspeed to continue flying, and to get to a place to make a safe landing, like a long, long runway. If you have to slow to ETL, you may not have enough fuel to reach a safe landing area. I would try increasing airspeed, even to above the redline, and get to an airport at a comfortable altitude. I guarantee you that nothing will break if you are slightly above Vne, because the manufacturer has to guarantee that nothing bad will happen AT Vne, so there is a margin built in. It's not for normal use, but a stuck collective is not normal. Descending is not really the problem, because there are a number of ways to do it. A tight turn will give a good rate of descent, given no change in power. The problem is touching down on the ground without causing major damage to the aircraft and the people inside. Getting everything to come together at the same time requires judgement, skill, and experience. Or else a lot of luck. Luck always helps, but if you had luck, you wouldn't have the problem in the first place, would you?

[FauxZ]

it's rather rare - in 40 years of flying, I've never heard of it actually happening. Everything is possible in a mechanical system, so it's probably worthwhile to occasionally do thought experiments on solutions to various malfunctions.

 

It happened at our school before I started there. Someone had dropped a pen and it fell into the nook under the collective and broke something. Happened in a hover on the taxiway, after an auto I think. Sorry for the sketchy details, but you get the general idea. R22 for those who care.

[Linc]

All my experience and comments are based solely on turbine engines, so keep that in mind.

 

When I flew the "R-model" OH-58D, we learned how to do FADEC manual throttle operation. The best technique I learned for landing during manual throttle from any instructor during that period was to use airspeed to control the descent. Into the wind, with 10% less than hover power, the aircraft still can't make up its mind if it wants to come down, so you play with the airspeed. If you want to descend, slow down, if you want to stop descending, speed up. Of course, in the manual throttle, you're trying to get to hover power and you can play with the collective to help control the rotor while manipulating the jet engine's throttle; it's very touchy.

 

In a 60 degree bank turn, it takes 100% of the cruise power applied, or 2G load factor to maintain a level altitude (not attitude). So, I'm not sure that an increase in load factor is going to do anything to help anyone get down in this case. I've tried the circling down method without any results that make me think that that is the way I want to try to get down. I mentioned it once as a possibility when a copilot asked me if there was "any other way" and then we tried it starting at 500 feet. We didn't get much lower, in fact, I remember that we ended up higher. For it to work, you pretty much would have to get aerobatic with the helicopter, IMO. In the turn, the nose wants to tuck which accelerates the aircraft and widens the turn radius, and as you pull aft cyclic to "decel" and tighten the turn radius, the aircraft climbs again, the added kinetic energy in speed traded back for the potential energy of altitude. Of course, you could purposely tuck the nose, which will accelerate the descent, but accelerating towards the ground from a cruise speed is not my choice of a good idea unless I'm doing diving fire, and even then, recovery has to be planned out. Whipping the aircraft around in a tizzy trying to induce a descending (basically sliding downward) turn to lose altitude no longer appeals to me as an option with a major control malfunction. I'd rather maintain good controlled flight for as long as possible.

 

I won't mess with the throttle on a turbine engine unless I absolutely have to (if the engine is running fine, let it), so for me, it is get below the minimum speed for the power applied when I'm at my intended landing area, manage the descent with airspeed and grease it on to a runway or accelerate a little bit towards the bottom for some sort of a decel before touchdown if I have to plant it for a spot landing. In both instances, rolling the throttle off the second the skids make solid contact. Only if I am at a HOGE power application with the collective will I ever consider messing with the throttle (using the technique Photoflyer mentioned, modified for the turbine aircraft I fly), and even then, someone will probably be paying for a helicopter. I just hope it's not me and that my technique is good enough that day so that everyone can walk away.

 

I'm not the authority, these are just my thoughts and my experience that may have some correlation to them. I'm just thankful that my luck is still holding.

Edited June 29, 2007 by Linc

[Gomer Pylot]

Given constant power, entering a turn with constant airspeed will result in some rate of descent. If you start a turn and don't change the collective, you will descend unless you slow down. The climb you describe is the result of slowing down, so you have to keep the nose down and the speed up to descend, and it's a rather subtle effect. It's more obvious if you do it in IMC or under the hood, trying to maintain altitude. The rate of turn doesn't have to be that great - a standard rate turn will give you a descent if you keep the speed up. It's not dramatic, but it's there. Again, this wouldn't be my first choice in most cases, but if you're over or very near the place you want to land, it might be an option. You're obviously going to have to evaluate the conditions you find if it happens, and make a choice based on those conditions. It's not possible to say what the right course of action would be from your armchair. There are several options, and it's up to the PIC to make a choice based on what he sees at the time.

[Witch]

I have a couple of stupid thoughts on how to get down. The first stupid idea was to-now give this some thought-turn the fuel valve half-off. This would reduce the amount of fuel and therefor, engine power.

 

But then that gave me another stupid idea, apply full carb heat. This would also reduce engine power.

 

Stupid idea number three is to-and this is really stupid-turn off one of the mags. Again, it'll reduce engine power.

 

All-in-all, these are desperate measures, but then so is a stuck collective.

 

 

Then I wonder...what about a stuck cyclic?

 

Later

[Linc]

Gomer,

 

At 15 degrees angle of bank, 1.05G or 3.6% more power will keep the aircraft at the same altitude.

At 30 degrees angle of bank, 1.2G or 15% more power will keep the aircraft at the same altitude.

At 45 degrees angle of bank, 1.4G or 41% more power will keep the aircraft at the same altitude.

 

In order to circle down, the pilot would have to allow the aircraft to accelerate and resist trying to maintain an airspeed in the turn. As the aircraft accelerates, the turn radius will widen, so the pilot will have to resist trying to maintain a circle over a point. Anything the pilot does that exceeds these load factors at the respective angle of bank, will lift the nose of the aircraft and it will quickly change from descending to climbing.

 

There is the old Huey trick from Vietnam to put the helicopter out of trim and cross control it into a sideslip and it will maintain its airspeed while descending without requiring collective movement. I've done that before with good effect and it is less like falling than diving out of the sky.

[coanda]

There is the old Huey trick from Vietnam to put the helicopter out of trim and cross control it into a sideslip and it will maintain its airspeed while descending without requiring collective movement. I've done that before with good effect and it is less like falling than diving out of the sky.

 

I've used this in an auto to hit a spot I was over shooting. It worked really well if you don't mind the wind in your face.

[joker]

This is a pretty rare thing to happen...so I guess that's why it doesn't get covered as an emergency maneouver. That being said, a better knowledge aerodynamics and the helicopter will enhance your chance of a safe recovery.

 

Not quite what we are talking about, but here's a story.

 

I was with a new commercial student doing 180 autos in a Schweizer.

 

"3,2.1, - Practice autorotation!"

 

Student rolls off the throttle, and a split second later, I see the RPM drop like a stone.

 

I instinctively go for the collective, but it won't budge. &*%^)(*) I thought. This is the worst time to have a stuck collective. Well, of course it didn't take me long to abandon the autorotation and focus on working out what I was going to do about this drooping RPM and collective that wouldn't go down. Roll on throttle, massive flare and tight turn and regained it.

 

Whole thing must have lasted about 2 seconds, but I can remember my thought process in detail.

 

Once recovered, I discoverd the battery box of the student's DC headset had got wedged under the collective.

 

 

 

Well that was a lesson learnt, and so I share with all.

 

As for a 'stuck collective' in the traditional sense of the term, then knowing ways to get to the back side of the power curve. You need to waste energy or convert the energy from lift into some other form.

 

Some techniques are only transient conversions of energy, others are more permanent. Depending on your position and situation, one or the other or a combination of more than one technique may be best.

 

Left pedal, fly out of trim, reduce RPM (carefull), tight turns (left), over torquing, adjust speed etc..etc.. All these have been said above though.

 

Joker

 

P.S. Don't know if he was serious (never can tell), but Witch's idea of messing with fuel line is a no no to me.

Edited July 1, 2007 by joker

[Gomer Pylot]

Yeah, I've slipped a UH1 lots of times. Sometimes in a tight formation it's necessary to stay in position on an approach. But I think you're missing the point of your formulas. They also say that entering a turn, and maintaining altitude, requires that much more power. Any bank angle will require more power than straight and level, given all else equal.

 

I don't say that's the best course of action, and I would only use it under a very few circumstances, but I still say that if you turn without changing anything else, you will descend. I've seen it happen thousands of times over the past 40 years, and it will happen again tomorrow.

 

I don't know about a Robbie, but I don't know of any other model in which you can turn the fuel valve halfway off. It's binary, either on or off. And turning it half off wouldn't necessarily reduce the fuel flow by half, or by any at all, anyway. And if it did, your Nr would drop, and then you would drop.

Edited July 1, 2007 by Gomer Pylot

[Superman]

I think that the real value to the stuck collective scenario is seeing what the thought process will be. As Flyby Heli pointed out, it can be interesting. I don’t know that there is a right way to do it, its just one of those things that has to be dealt with on the fly so to speak. In my situation, I looked for the obvious, friction on, something stuck under the collective, seatbelt etc. Nothing there, everything still working, continue to the airport (old fixed wing instructor said that if you think your gonna crash, may as well do it at the airport) anyway, My instructor just sat there, didn't say a word until I figured it out, and I'll admit that it took me a while to figure it out. I used a combination of the circling, airspeed and RPM control to get down, then set up for the runway, used airspeed, out of trim (slip) to make the approach and throttle at the end, didn’t take it to the ground, but I think it would have been survivable. I think I’ll go and try it this week, something I haven’t done for a while.

 

 

 

Fly Safe

Clark

[Witch]

I don't know about a Robbie, but I don't know of any other model in which you can turn the fuel valve halfway off. It's binary, either on or off. And turning it half off wouldn't necessarily reduce the fuel flow by half, or by any at all, anyway. And if it did, your Nr would drop, and then you would drop.

 

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

[Linc]

But I think you're missing the point of your formulas. They also say that entering a turn, and maintaining altitude, requires that much more power.

Gomer,

 

I just want to point out that they are either/or equations, either the load factor must be present or that percentage of power must be added in order to remain at the same altitude.

At 15 degrees angle of bank, 1.05G or 3.6% more power will keep the aircraft at the same altitude.

At 30 degrees angle of bank, 1.2G or 15% more power will keep the aircraft at the same altitude.

At 45 degrees angle of bank, 1.4G or 41% more power will keep the aircraft at the same altitude.