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turns in an auto. what to expect


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Here is a question for you all. Lets say I am in an autorotation and need to loose some altitude to make my spot. I decide to make some 90 degree turns. How will the helicopter respond in a right and left 90 turn in an auto? When I make one to the right, will the heli want to nose up, so I will have to push forward cyclic and raise collective a touch to keep the nose down and rotor rpm from increasing? Will the opposite be true in a left hand turn? Just wondering if I can get some clarification. Thanks

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Turning right or left won't affect pitching up or down enough to be a consideration. The reason the nose pitches up in a right turn is because most people pull slightly aft on the cyclic with out realizing it. If a person concentrates on not pulling aft when turning, they will be able to hold the nose level throughout the turn.

 

If a turn is made during an auto the rotor rpm tends to increase. To keep the rpm where desired raising the collective would be necessary. This is true no matter which way the helicopter is turning.

 

Another option for losing altitude other that making 90 degree turns would be to slow the airspeed while high then gaining it back before losing too much altitude. This is a good option because it keeps the landing spot in view. This must be done correctly otherwise there may not be sufficient airspeed at the end to perform a proper flair.

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If a turn is made during an auto the rotor rpm tends to increase. To keep the rpm where desired raising the collective would be necessary.

 

And don't forget to mention the obvious (but often missed) consequence of this.

 

When you come out of the turn in that configuration your RPM will droop. You need to lower the collective again.

 

Anytime you feel squashed into your seat, raise the collective. Soon it will become natural.

 

Joker

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Turning right or left won't affect pitching up or down enough to be a consideration. The reason the nose pitches up in a right turn is because most people pull slightly aft on the cyclic with out realizing it. If a person concentrates on not pulling aft when turning, they will be able to hold the nose level throughout the turn.

 

If a turn is made during an auto the rotor rpm tends to increase. To keep the rpm where desired raising the collective would be necessary. This is true no matter which way the helicopter is turning.

 

Another option for losing altitude other that making 90 degree turns would be to slow the airspeed while high then gaining it back before losing too much altitude. This is a good option because it keeps the landing spot in view. This must be done correctly otherwise there may not be sufficient airspeed at the end to perform a proper flair.

 

 

 

 

don't forget if you just have to loose some altitude not alot, Ride the auto with a higher RPM and the decent rate will increase. For small altitude changes this is the best bet because you just have to adjust the collective with a fixed airspeed. if you reduced your airspeed when you don't have to, then you then in turn end up manipulating more then one control which makes the auto complicated. We want to keep them simple.

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You can also kick the aircraft out of trim to help a bit too. I can't remember all the specifics of this though, I haven't had as much time to practice it as I'd like. Maybe someone more experienced could expand on it?

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Kicking out of trim doesn't really help much, and it brings other factors into play - the R22's pitot tube will not be aligned with the airflow, and will under-read. The student sees a drop in apparent airspeed and lowers the nose, which increases airspeed and rate of descent. when he finally balances again, the increased airspeed makes him pull the nose up, RRPM go up, pitch to control revs, and it all turns to worms while getting very close to the ground. Not good news.

 

Another problem with the original idea of turning 90 degrees is that you are now travelling cross-wind (assuming you were previously pointed at the target and into wind), so when you turn back to the target, you need more than 90 degrees to point at it, and are now coming in on an angle to the wind. It all depends on how close you are to begin with. Try it one day with the 1500' markers on the runway as the target. Running straight at it, you have the assurance that a little overshoot or undershoot is not a problem, as there is runway in both directions. Then turn away 90 degrees, hold it for a bit, then turn back. The overshoot and undershoot options are now not so attractive, are they?

 

Careful judgement required.

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Thanks for the info. We've flown out of trim (i mean more than just dumb student mistakes ;) only once, and like you said, the ASI was pretty worthless for obvious reasons. I know that you'll drop like a stone if you're out of trim in a 180, I figured you'd get similar results from a straight in.

 

Need more practice!!! ;)

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This brings a question that I got from the Robinson Safety Course.

 

In training it is hammered so much to keep the speed at 60 - 70 KIAS and keep the RPM in the green.

 

But in the safety course that is not what was taught. Man, in the course you set the collective in the beginning and you never moved it till your at the end. We slowed the speed waaaayyy down, to maybe 45 KIAS and that RPM would drop down to 85%.

 

So to my question, which is right? I can do the ones taught in training, but the ones from the Safety Course seemed soooo much smoother and allowed for alot of correction to make your landing spot.

 

For the 180's and even 360's it was awesome. You lower the collective, roll off throttle, check the collective , then don't move the collective at all. If you kept the helicopter level throughout the entire turn the rpm's wouldn't change at all and speed was perfect. It was amazing.

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In training it is hammered so much to keep the speed at 60 - 70 KIAS and keep the RPM in the green.

 

But in the safety course that is not what was taught. Man, in the course you set the collective in the beginning and you never moved it till your at the end. We slowed the speed waaaayyy down, to maybe 45 KIAS and that RPM would drop down to 85%.

 

So to my question, which is right? I can do the ones taught in training, but the ones from the Safety Course seemed soooo much smoother and allowed for alot of correction to make your landing spot.

 

I have flown many hours at high altitude and letting your rpm get that low is extremely dangerous the higher you are. I find that playing around with airspeed is a fairly easy and safe way to go. I personally wouldn't want to see my rpm down to 85%. At that point you are only 5% away from a stall at sea level and as you gain altitude that 80% goes up 1% per thousand feet. Also, operating with the rpm less than the red line is illegal, so anything below 90% is definitely questionable. Of course in a real emergency you may deviate from the regulations, but you weren't in a real emergency.

 

For the 180's and even 360's it was awesome. You lower the collective, roll off throttle, check the collective , then don't move the collective at all. If you kept the helicopter level throughout the entire turn the rpm's wouldn't change at all and speed was perfect. It was amazing.

 

I don't know how much time you have, but when I went to the safety course I had low hours and probably missed quite a bit of things while flying. My students sometimes move the collective and don't even know it. I have done maneuvers like approaches and quick stops where the student couldn't tell that I was adjusting the throttle and sometimes they missed what I did with the collective as well. The point is, you cannot simply leave the collective in one spot if you are initiating a turn or rolling out of a turn. If the collective is properly positioned then it does not need to be moved at all if flying straight or if the aircraft is in a constant bank turn. If you did a 180 or 360 auto, there probably was some point where the collective was adjusted, even if it was just a slight adjustment.

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Not to give away any Safety course secrets, but we were doing vertical auto's at zero airspeed..thats one way to keep your landing spot in sight and lose some altitude..of course you need to recover airspeed as you get closer so you have it for the flare...pretty cool stuff that you can do with a 6,000 hour Robbie pilot !

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Is that anything like settling with power? Maybe like falling straight down and then putting the collective down to get out of the vortex ring and then diving out and getting airspeed for the flare?

 

Huh?

 

Later

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Is that anything like settling with power? Maybe like falling straight down and then putting the collective down to get out of the vortex ring and then diving out and getting airspeed for the flare?

 

I beleive the air below your heli, is less disturbed cause of the low engine setting, and the air moves from below to above the rotors, pluse you are falling alot faster than a 3-500 decent with pulling more collective and power. I'm sure these autos are harder than the test pilot makes them seem, and you really have to know how to get yourself out of every situation that may come up with these risky autos... they are so experienced with that specific heli and they can probably scare you pretty good if they wanted too.... I would love the chance to train with one of them for about 50 hours, that experience would be priceless... could you imagine how relaxed they would be with a very low time pilot at the controls. These are the guys that could teach you how to basically fly in one good lesson........ Must be a cool job, wonder if they need a low time reckless pilot to add onto their crew?????

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These auto's are exactly what I am talking about. They are not that difficult, you just have to know to get your airspeed back by about 400 to 300 ft AGL. If you don't then there is not enough airspeed for the flair.

 

In a zero airspeed auto there are no vortex rings. The whole rotor system has an upward flow of air over it. This is why it is impossible to get the second set of vortex rings that put you into settling with power.

 

I guess I was a fortunate guy when it came to my training. My primary instructor had 1100 hours, at least 2 of my instructors for my commercial had 6,000+ hours, and for my cfi I was flying with another very high time instructor. I was showed many different techniques and it seems that other people aren't getting that same training.

 

In all of my training none of them let the RPM get below 90%. We played with turns, slowing airspeed, and slips but never let the rpm get below the red line.

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The point is, you cannot simply leave the collective in one spot if you are initiating a turn or rolling out of a turn. If the collective is properly positioned then it does not need to be moved at all if flying straight or if the aircraft is in a constant bank turn. If you did a 180 or 360 auto, there probably was some point where the collective was adjusted, even if it was just a slight adjustment.

 

 

Sorry but that's not true. That collective did not move at all after it was checked until we were near the ground in the flare. The first couple ones I did I would move it a bit in the turn just like I was taught to do and he kept telling me to not move it. He was darn near bitching me out for it.

 

And I tell ya, if going below the red line is illegal, then almost everyone of our auto's were illegal. That RPM would drop and I would hear the horn. He would say, "check the RPM's, ok were above 85, were still good." It was a humbling experience flying with those pilots. It's amazing what those guys can do. Now I'm not saying I would go out and practice these auto's without someone like those factory pilots nor would I demonstrate them to any of my students, but's it's great to know what the bird will do in a true emergency situation.

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And I tell ya, if going below the red line is illegal, then almost everyone of our auto's were illegal. That RPM would drop and I would hear the horn.

 

Just because you hear the horn, it doesn't mean that you are below the red-line. Check your books!

 

Vertical Autos - Good technique. I did one in my CPL checkride. The examiner couldn't fault it. However, someone stated the recovery altitude as being 300-400' agl.

 

They are not that difficult, you just have to know to get your airspeed back by about 400 to 300 ft AGL.

 

This is too low for me. The R22 HV curve will show why.*** Remember that the HV curve is based on 0-airspeed at hover. It doesn't account for a 1500 fpm descent rate too! Next, you are not normally at sea-level DA. My rule of thumb therefore is to initiate recovery somewhere between 400-600' agl depending on DA.

 

And there is no VRS involved as you have flat pitch!

 

Turns - As Eric said, turns can become more trouble than they're worth, especially if you were perfectly lined up for your spot on entry. However, I always prefer to be on a base leg than straight-in. If not too much trouble I will maneuver for that.

 

RPM control in turns - I think there was misunderstanding here. If the auto is initiated and the collective pitch set at say, "X" for a straight forward gliding auto, then anytime you return back to that state, the same collective position of "X" will suffice.

 

However, if you set X, then initiate aggressive banking movements, of course, you will need to check collective to control the RPM!

 

So it depends on the aggressiveness of the banking.

 

The first couple ones I did I would move it a bit in the turn just like I was taught to do and he kept telling me to not move it.
FUSE, I suspect he told you that because you were overcontrolling it. A sort of psychological game, maybe?

 

YES, it is possible to do a 180 auto with nice wide turns, where the aggressiveness of the bank is so little that the collective doesn't need to be moved, or where RPM can be controlled with cyclic alone. This is unrealistic though. I tell you...if I am faced with a crappy situation, then I will bank aggressively enough to get to my safe landing spot. If I need to chuck the aircraft into a bank to get back to a spot that is downwind of me, and then chuck it back to turn into wind again, I'll do that.

 

In R22, you WILL need to work the collective. Don't think otherwise. That'll kill you, because you're rotor head will spin off in spectacular fashion.

 

Letting RPM droop below Red - By RFM it is prohibited for 'Normal Operations'. Emergency procedures are not 'normal' and so you can deviate if you need. However, I WOULD NOT! It seems foolish to do this, unless right at the beginning of an aggressive flare into a short landing spot at the end of your auto!

 

I guess the moral is that there are so many factors that come to play when faced with a real engine failure, that no single technique is can be cited. Everyone has mentioned good ideas, but others might fit better in a bad situation. There are 'checkride' performance manevuer autos, and there are 'Oh, sh1t, we just lost the donk', real world ones. Here's something to keep in your head when faced with the latter:

 

Do what you need to do to make that spot!

 

During your initial training, you fly your autos by rules. 1-2-3 - AUTO - lower collective - wait - check collective - turn - check attitude - look at spot - look at rpm - look at airspeed - etc..etc..

 

As we know, the engine doesn't quit according to rules though. Whith proper training, RPM control will become a reflex. Only then will you be truely prepared for engine failure at altitude.

 

OK, some of this is repeating what good advice has already been posted here. I just wanted put all my observation down in a single post.

 

Joker

 

*** Just a further note on the HV curve.

 

When discussing the HV curve, I used to ask in stage checks this"

 

"What altitude today can we expect not to be able to complete a successfull auto from 0 airspeed."

 

The answer would invariably come back at the intersection of the curve and the axis on the diagram. Problem was, that rarely we were at standard day conditions.

 

The point is, the HV curve is predicated on DA. All it needs is a few degrees extra and the curve looks significantly different.

 

This was often missed / unappreciated or misunderstood (especially by Schwiezer students) by students and instructors alike.

 

(Same issue for Schweizer - No autos above 3570 DA rule (or whatever it was).

Edited by joker
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Joker, thank you for your post. This is basically what I was trying to say. I think it is good for us to try to help answer questions as it really makes us think and try to explain in helpful ways. I know I am always learning and willing to admit when I am wrong.

 

Also, when I stated the 400 - 300 ft for recovering airspeed I was going from experience and I know that if you wait longer than that you will not have enough altitude to recover adequate airspeed. If you have enough room to recover airspeed higher than this then that is great! Play around with it and see just how much altitude it takes to recover the airspeed. Remember, the HV curve is built with the "average pilot" in mind when they would not be expecting anything to happen. If you have initiated a zero airspeed auto, you know what is happening. If you start to nose it over as you pass below 400ft then you have enough time.

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Yes Joker- great reply-

 

but

 

I have to add that the HV curve is based on the time "entering" an auto...whereas when doing a vertical auto...I am already in the auto and there is no time delay dropping collective...you just nose it over and gain speed....so yes, I wouldnt do it as a matter of practice, but you can recover in less altitude than the HV curve if you are already in the auto...and of course assuming a low DA.

 

Remember they test these ships, and create the HV curve just off the ocean in So Cal...so pretty low altitudes there !! The high speed low altitude test ( I think it was 80 knots and 20 feet agl..) was also at 20 MSL in the channel next to the Queen Mary-

 

Dont try this at home.

 

Goldy

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Goldy / southernweyr,

 

Yep, you both make very true points. Regarding the HV curve I didn't tell the whole truth, did I?

 

During a vertical auto:

 

Working for you is that you are already in the auto, so no time delay in establishing autorotational flow or gaining speed.

 

Working against you is an established 1500 fpm descent rate.(25 fps) Maybe this is negligable in an R22...I don't know. I am certain with a heavier ship, this is problematic. (F=Ma) I tried one in S76 a month ago during a check, but I didn't get the speed all the way back (min. 45kts), and was VERY conservative about when I started regaining speed (which did seem to take ages to come back), so no useful data there...sorry!

 

Maybe for everyone's peice of mind, someone can go out and test how long it takes to recover 80kts from a vertical auto, in terms of time and altititude. Then go out and do one from a hover. (Can be safely done at 1000' AGL). Then post the results here. I think I did it once a long time ago. We found (just as Goldy and Southernweyr state) that actually you are able to recover within the HV curve.

 

Over the months I guess I now simply err on the side of caution when performing, teaching and explaining this maneuver, by filtering out of mind, those factors which are working in one's favour, in order to leave me with worst case to work with.

 

As we all agree though, the earlier you can start to recover speed back, it better. Don't leave it too late, if you don't have to!

 

Cheers,

 

Joker

Edited by joker
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Goldy / southernweyr,

 

Yep, you both make very true points. Regarding the HV curve I didn't tell the whole truth, did I?

 

During a vertical auto:

 

Working for you is that you are already in the auto, so no time delay in establishing autorotational flow or gaining speed.

 

Working against you is an established 1500 fpm descent rate.(25 fps) Maybe this is negligable in an R22...I don't know.

Joker

 

Joker- you are correct. The 1500fpm descent rate is established and a huge negative. The thing about the light rotor system of the R22 is it can be easily recovered and easily lost. I hate even talking about no airspeed in an auto, due to the students reading this....speed is the one thing that will keep you alive...even more than altitude, so don't give it up needlessly !! These manuevers are nice to know, but really one in a hundred in a real auto...Enough said...don't try these !!!!

 

and I'm really jealous of you in a 76..

 

Goldy

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The point is, the HV curve is predicated on DA. All it needs is a few degrees extra and the curve looks significantly different.

 

This was often missed / unappreciated or misunderstood (especially by Schwiezer students) by students and instructors alike.

 

(Same issue for Schweizer - No autos above 3570 DA rule (or whatever it was).

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I'm not too sure what you're talking about here concerning no autos above 3570 (3750 is a more common number for schwiezers). I've never seen or heard this and have done plenty of autos above 3570 DA, and the guys at High Desert in utah wouldnt be getting much emergency procedures training done for 3/4 of the year if it was so. Also if it were true, i doubt the FAA would certify it to fly above that altitude.

The HV curve certainly is predicated on DA, among other things such as skill landing surface and alignment of the stars, and any CFI that fails to point that out is doing a huge and dangerous disservice to their student. Also not sure why you're picking on schwiezers here. u arent a Frank in sheeps clothing, are you?! ;)

 

Whatever type of helicopter I'm in I usually add a very healthy margin to the h/v, I even have a puffed up one I use to brief photographers so they dont get any silly ideas. Helicopters are versatile and alot of the value of that versatility comes from operating in the H/V curve. Assesing that value and minimizing the risks associated with it is what being a helicopter pilot is.

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I'm not too sure what you're talking about here concerning no autos above 3570 (3750 is a more common number for schwiezers).

 

I had tried to be clear that this was a Schweizer issue (not an R22 issue) in my last post.

 

In my old knackered Schweizer 300CB RFM, it says this in bold letters in the emergency section:

 

WARNING

 

AVOID THROTTLE CHOPSS TO FULL IDLE ABOVE 3750 DENSITY ALTITUDE TO AVOID POSSIBILITY OF ENGINE STOPPAGE.

 

Well, my bad, as it is more about 'throttle chops' rather than 'autos. Anyway, I don't think this distiction was realised the majority.

 

So, like I was saying, I'd hear repeated stories of people going out in the middle of a Florida summer (31 degrees), climbing to say 2000' and doing their throttle chop training there. Tsk, tsk I would say to them.

 

Well, you know how I love questions, so I put this pretty easy one out all. Why this limitation? Why not the same in the R22?

 

I would be interested to know if this is the same case in the CBi RFM. I see no reason why not.

 

So, I'll leave a little time for folks to chew on this.

 

Joker

Edited by joker
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Well, you know how I love questions, so I put this pretty easy one out all. Why this limitation? Why not the same in the R22?

Joker

See Robinson Safety Notice SN-27 (attached) about throttle chops. I think the comparable R22 limitation you're looking for is using full carb heat whenever you go below 18" MAP.

rchsn27.pdf

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Pogue,

 

Thanks for that...

 

It wasn't really what I was thinking. You don't explain the 'altitude' issue, and why that is only in the Schweizer RFM.

 

Also, the Carb Heat requirements are pretty similar in both aircraft, and are mentioned elsewhere in the 300CB RFM.

 

The last two lines of the SN-27 are the closest to what I'm talking about (in a roundabout way).

 

Joker

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