Autorotation: Hitting the spot
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You should also refer to SN36.
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You guys crack me up, pick a field ,Mmmm hows about pick a tree. I just spent the best part of 8hrs today on a longline doing precision stuff with 2000lb loads as I do most days, getting eaten alive by flies, bugs etc, in the Boreal Forest, we dont have the luxury of fields, I wish 
'Newfieboy' In what way was your reply constructive to the guy who started the thread? Or should I have just swung the lantern too based on all my experience in different parts of the world!
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He wanted to know how he can IMPROVE HIS TRAINING.
Exceeding the upper limit can result in a loss of the main rotor-or cause big damages so "hitting the spot" is then the most minor of your problems..
Far more folks have been hurt....and helicopters destroyed by the lack of Main Rotor RPM than too much. If the aircraft is properly rigged there should be danger of causing one self any harm by an overspeed situation.
Again....I put forth my view on this.
Limitations are for Normal Operations!
There is absolutely no reason to worry about damaging an aircraft by overspeeding a rotor when you are about to crash it....the rotors are probably going to be trashed anyway and one might as well use them up saving yer hind end.
Yes.....the phrase "Ass, Tin, Ticket!" applies to this discussion on real life engine out landings.
Rabid has gotten some very good suggestions and the discussion branched out to a discussion on emergency landings....which cannot hurt anyone to read it. As in all things....pick the pretty berries and leave the bad ones.
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We are not talking about DAMAGING a helicopter with too much r-rpm....we are talking about loosing lifes because of too much r-rpm..
EN48-I agree with you in that point...
There is actually no sense in "hitting the stamp" in an auto-that is just a method of training....
In an actual emergency, it is not important to land on the spot-but it is important to fl the helicopter down to the spot you want to....
In an actual emergency, i would like to have the r-rpm at "high green"-but there is no way i am letting it increasing to the high red marking...
I have seen a helicopter which went through the high-r-rpm stage......not a nice wreck at all.....
And :
I do not agree to this "limitations are for normal operations"....
There are also limitations on emergency procedures.....and there are reasons WHY there are limitations on emergency procedures..
We are still talking about a "Beginner".
And to tell a beginner that "limitations are for pussies".....is not a good start...(i am exagerating...)
SASless:
You are right.
After training "student-autos" it is VERY important to know that things will be different when the engine quits in real life.......but there are instructors out there that should tell their students about that....
EN48-I agree with you in that point...
There is actually no sense in "hitting the stamp" in an auto-that is just a method of training....
In an actual emergency, it is not important to land on the spot-but it is important to fl the helicopter down to the spot you want to....
In an actual emergency, i would like to have the r-rpm at "high green"-but there is no way i am letting it increasing to the high red marking...
I have seen a helicopter which went through the high-r-rpm stage......not a nice wreck at all.....
And :
I do not agree to this "limitations are for normal operations"....
There are also limitations on emergency procedures.....and there are reasons WHY there are limitations on emergency procedures..
We are still talking about a "Beginner".
And to tell a beginner that "limitations are for pussies".....is not a good start...(i am exagerating...)
SASless:
You are right.
After training "student-autos" it is VERY important to know that things will be different when the engine quits in real life.......but there are instructors out there that should tell their students about that....
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Well you guys have succeeded in explaining quite a few things. In an emergency 1st and foremost fly the helicopter, RPM's are life, keep it within limits for training at least. All of you guys have given me great input and I am not so daft as to try and do it all at once or inappropriately. I am going to read and re-read all of you guys/girls responses and take the little bits of knowledge that I need, when I need them, until it all comes together. I am not sure my instructor (who is in charge of cleaning the windscreen after each flight) will take kindly to the grease pencil method, but I will definitely suggest it. I have never looked for the area that appears to be stationary, and now I am very curious... One big solution to this problem will come in about 9 days when I am done with private and move back to my original instructor (who is awesome). We are going to revisit the autos.
Great job and thanks again.to all of you.
Great job and thanks again.to all of you.
keep it within limits for training at least
That is exactly why I have never liked this "You can never have too much RRPM in auto" mantra... "don't think about anything else, just make sure your RRPM is high" etc.
In my opinion it teaches a single focus and a lack of understanding of the whole equation, and poor RRPM management. RRPM management is the key when power is lost. Those limits are there for very good aerodynamic and structural reasons, do not ignore them.
The ultimate rotor overspeed limit is when it fails. SASLess, can you tell me exactly at what point the rotor system will let go in an overspeed, so I know just how much overspeed at the bottom of an auto I can accept and get away with? Do I now have 2 sets of limits to abide by, the published ones, and the emergency "anything goes" ones?
Don't forget that ROD is a consideration in autorotation, it is usually this that kills people when the ground arrives. Having unnecessarily high RRPM also means an unnecessarily high ROD which also must be arrested. More RRPM at the bottom to deal with my higher ROD that I must now lose before touchdown.
I acknowledge that this whole argument is geared around "you are less likely to die with high RRPM than low RRPM" in that poor RRPM management usually leads to it being low and the resulting high ROD from that is not escapable.
But surely training is when we learn how to do it right, so that when the real emergency comes we do it absolutely right, and not a whole new way because all bets are off.
Last edited by the coyote; 27th Jun 2010 at 22:52.
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I was trying to settle the argument for everyone.
Alright Coyote, if/when the engine takes a nap, I'll revert to my awesome training (which will re-commence in 9 days hopefully) and stick to the green, but if I have a bit extra revs I'll pull a bit of collective and avoid the overspeed, but I won't freak that they're a bit high. How's that? Is that the appropriate attitude for the new guy? (serious question, not sarcasm)
I think I get the point... when the engine kicks the bucket, don't overfocus on green RPM's and miss the point of getting on the ground alive, but don't be shooting for an overspeed and make 2 emergencies out of 1.
Alright Coyote, if/when the engine takes a nap, I'll revert to my awesome training (which will re-commence in 9 days hopefully) and stick to the green, but if I have a bit extra revs I'll pull a bit of collective and avoid the overspeed, but I won't freak that they're a bit high. How's that? Is that the appropriate attitude for the new guy? (serious question, not sarcasm)
I think I get the point... when the engine kicks the bucket, don't overfocus on green RPM's and miss the point of getting on the ground alive, but don't be shooting for an overspeed and make 2 emergencies out of 1.
Last edited by rabidcat; 27th Jun 2010 at 23:16.
Alright Coyote, if/when the engine takes a nap, I'll revert to my awesome training (which will re-commence in 9 days hopefully) and stick to the green, but if I have a bit extra revs I'll pull a bit of collective and avoid the overspeed, but I won't freak that they're a bit high. How's that? Is that the appropriate attitude for the new guy? (serious question, not sarcasm)
However, should you have a genuine emergency, and you revert to your training and keep the aircraft within its limits during that time, I would think this is an appropriate course of action to take, and one that is likely to lead to a successful outcome.
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Cool, yea I was not being defensive, just trying to figure out the general consensus on what is acceptable. Appreciate the input from all of you.
So, in plain old American, what does that mean? It is just too british for my dictionary 
Oh to be bimbling round Blighty again with all those options
Coyote,
Have you ever done an airtest to adjust Autorotative RPM on a helicopter? Does your company routinely do such checks? Do you understand how and why those checks are done? Do you accept an aircraft properly rigged cannot achieve rotor shedding RPM in autorotation? Do you adjust your settings for the conditions you actually fly in?
Now assuming one is flying a properly rigged aircraft....one can accept the fact that actual autorotative RPM will vary depending upon various factors such as aircraft weight, airspeed, density altitude for example thus one needs to monitor the Actual Rotor RPM and control it by means of collective (primarily) and airspeed or acceleration or deceleration (loading) but only relatively minor variations should occur. (Remembering the aircraft is properly rigged.....you do fly properly rigged aircraft do you not?) The Rotor RPM might exceed one of the limits but not by much.....nothing a small touch of collective won't cure.
In an actual emergency, I suggest priority goes to aircraft control, hitting the desired safe landing area, and worrying about exceedances becomes secondary. There are buffers built into every limitation. Rotors do not automatically and instantly shed themselves if you exceed the normal limitations limit.
As having insufficient Rotor RPM is a sure killer......proven over and over again through the ages of helicopter flying....we should ensure we get to the bottom with as much RPM as we can muster. That can be done by a simple maneuver called "flaring" done at the very bottom. That connotes flying the machine in such a manner as to have airspeed and collective position to trade for increased Rotor RPM. Again, any exceedance is going to transient as landing shall require the raising of the collective to slow the ROD and ground speed.
As to Rate of Descent (ROD) you worry about.....sheer collective position alone will not produce a ROD that is problemattical....only when you include certain airspeeds, turns, pitching movements, might that happen. You remember the Blue line on the Bell 206 series for example?
Somewhere in this discussion I failed to mention the Golden Rule of Helicopter Flying...."THINK!". I see your expressed worries as falling short on that. You suppose we advocates of having lots of Rotor RPM as ignoring a long list of factors and experience when we express our views.
When things happen fast as they can in helicopter flying...."Thinking" sometimes becomes more reacting than reasoning....and if one is predisposed to remembering to have lots of Rotor RPM rather than worrying about whether it is at a certain RPM...odds are....you will be able to lean on a Bar somewhere and regale your compadres with a harrowing account starting off with "There I was with nothing on the clock but the makers name....and the Donk died.....".
You are quite right when you pose a concern about exceeding published Limitations willy nilly....but let's add in all the factors that preclude your imagined imitation of a failed collection of Boomerangs caused by an grossly overspeeding Rotor system.
Have you ever done an airtest to adjust Autorotative RPM on a helicopter? Does your company routinely do such checks? Do you understand how and why those checks are done? Do you accept an aircraft properly rigged cannot achieve rotor shedding RPM in autorotation? Do you adjust your settings for the conditions you actually fly in?
Now assuming one is flying a properly rigged aircraft....one can accept the fact that actual autorotative RPM will vary depending upon various factors such as aircraft weight, airspeed, density altitude for example thus one needs to monitor the Actual Rotor RPM and control it by means of collective (primarily) and airspeed or acceleration or deceleration (loading) but only relatively minor variations should occur. (Remembering the aircraft is properly rigged.....you do fly properly rigged aircraft do you not?) The Rotor RPM might exceed one of the limits but not by much.....nothing a small touch of collective won't cure.
In an actual emergency, I suggest priority goes to aircraft control, hitting the desired safe landing area, and worrying about exceedances becomes secondary. There are buffers built into every limitation. Rotors do not automatically and instantly shed themselves if you exceed the normal limitations limit.
As having insufficient Rotor RPM is a sure killer......proven over and over again through the ages of helicopter flying....we should ensure we get to the bottom with as much RPM as we can muster. That can be done by a simple maneuver called "flaring" done at the very bottom. That connotes flying the machine in such a manner as to have airspeed and collective position to trade for increased Rotor RPM. Again, any exceedance is going to transient as landing shall require the raising of the collective to slow the ROD and ground speed.
As to Rate of Descent (ROD) you worry about.....sheer collective position alone will not produce a ROD that is problemattical....only when you include certain airspeeds, turns, pitching movements, might that happen. You remember the Blue line on the Bell 206 series for example?
Somewhere in this discussion I failed to mention the Golden Rule of Helicopter Flying...."THINK!". I see your expressed worries as falling short on that. You suppose we advocates of having lots of Rotor RPM as ignoring a long list of factors and experience when we express our views.
When things happen fast as they can in helicopter flying...."Thinking" sometimes becomes more reacting than reasoning....and if one is predisposed to remembering to have lots of Rotor RPM rather than worrying about whether it is at a certain RPM...odds are....you will be able to lean on a Bar somewhere and regale your compadres with a harrowing account starting off with "There I was with nothing on the clock but the makers name....and the Donk died.....".
You are quite right when you pose a concern about exceeding published Limitations willy nilly....but let's add in all the factors that preclude your imagined imitation of a failed collection of Boomerangs caused by an grossly overspeeding Rotor system.
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* Got to make up for being less erudite where I can
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I'm a bit of a dab hand at practicing auto rotations. I prefer to approach the flare at min RRPM (thus also min ROD) and prevent it from raising more than just a touch by raising the lever. I think if you have your rpm on the high side then your ROD is too fast.
Last edited by chopjock; 28th Jun 2010 at 14:42.
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Being a maintenance test pilot, let me explain to you that one cannot adjust autorotative R-RPM.
You can only adjust the warning light/audio step.....or je-adjust the reading instrument..
The r-rpm is not adjustable...
Think that you meant that-but it is misunderstandable...
If r-rpm is high green (or over) BEFORE the flare, there will be a massive exceeding of the main rotor-rpm limitation when doing the flare..
But finally i think we are talking about the same things....
You can only adjust the warning light/audio step.....or je-adjust the reading instrument..
The r-rpm is not adjustable...
Think that you meant that-but it is misunderstandable...
If r-rpm is high green (or over) BEFORE the flare, there will be a massive exceeding of the main rotor-rpm limitation when doing the flare..
But finally i think we are talking about the same things....
hueyracer
What! I have just retired from being the MTP on AStars and 412. Both had an auto check post servieing and, sometimes, it was out of limits for the weight/temp/altitude on the day. When that happened, the RRPM were adjusted mechanically to bring them into limits ( -0 to +10 RRPM of datum for the 350 and +/- 3% for the 412).
Onto you're next point, if the Nr is high during the flare, why not use collective to contain it? Basics!
Onto you're next point, if the Nr is high during the flare, why not use collective to contain it? Basics!
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You can balance the main rotor blades to bring them into trim (or use the trim tabs -depending on your type of helicopter) -but how on earth are you going to adjust autorotative r-rpm?
We are NOT talking about adjusting the normal r-rpm during flight...just about the free-wheeling r-rpm....
Why should one go into the "high-risk-area" of massive overspeeding, when he needs to pitch the r-rpm down afterwards?
I agree if you say-keep the r-rpm in the high green limit.....so you have more power to cushion the landing..
But i disagree (in my own personal opinion and experience) if one is continueing telling to keep the r-rpm highly over the limit...
We are NOT talking about adjusting the normal r-rpm during flight...just about the free-wheeling r-rpm....
Why should one go into the "high-risk-area" of massive overspeeding, when he needs to pitch the r-rpm down afterwards?
I agree if you say-keep the r-rpm in the high green limit.....so you have more power to cushion the landing..
But i disagree (in my own personal opinion and experience) if one is continueing telling to keep the r-rpm highly over the limit...
Being a maintenance test pilot, let me explain to you that one cannot adjust autorotative R-RPM.
How about explaining why one cannot do so please?
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adjusting auto rrpms
Thread drift, but yes, you can adjust your autorotation rrpms.
I'm sure all of us pilots have heard the term "flats" from the engineer when doing track and balance flights.
in track and balance you can adjust blade weight, trim tabs and angle of attack.
you set autorotation rrpm by adjusting "flat pitch" angle of attack by means of push rod length, acheived by turning all push rods a set amount of nut "flats" to correct for over/under rrpm on an autorotation. (for Bell anyways, not sure on others)
This autorotation rrpm check should be done after the completion of every track and balance.
I'm sure all of us pilots have heard the term "flats" from the engineer when doing track and balance flights.
in track and balance you can adjust blade weight, trim tabs and angle of attack.
you set autorotation rrpm by adjusting "flat pitch" angle of attack by means of push rod length, acheived by turning all push rods a set amount of nut "flats" to correct for over/under rrpm on an autorotation. (for Bell anyways, not sure on others)
This autorotation rrpm check should be done after the completion of every track and balance.
Comment on both teaching and learning autorotations:
It has been some years, but I used to teach a special circular autorotation scan (Seahawk) that accounted for line up/spot (target) position in windscreen, airspeed & NR (really needed to be scanned together), altitude/radalt (depends on phase of auto ...) and ball, then back out. It was my teaching approach that the key to a good auto is a good entry (down right idle turn was the Jet Ranger mantra, but "control Nr and Airspeed is generic as a truth) followed by a fast and sustained scan, with corrections to match.
We fixed quite a few problems among novices with teaching them the scan, and what corrections / counter corrections (every correction has a counter correction, doesn't it?) got you the performance you were looking for.
I see some advanced skills being discussed here. Is it fair to say autos to a spot are an advanced skill? (Is that the consensus in the civil world? I am a few years out of date here).
I tip my cap (seriously!) to those who know their aircraft well enough to control airspeed through visual reference to horizon, outside reference, and Nr by audio cues.
If you practice enough, and have a decent outside ref, you can estimate flare height. Without a radalt, that's a required visual skill to learn early in life, but if I recall, flare height is somewhat model dependent.
For our OP: has your instructor taught you a specific autorotation scan?
A tailored scan for a task seems a good way to stay ahead of the aircraft.
for hueyracer: we adjusted auto rpm after every maintenance check flight, usually adjusted for season and weight. (The procedure was in the maintenance manuals). The idea was that you'd have a ballpark "good" NR if you lost engines, or had to auto for other reasons, seasonally adjusted.
Now that I think of it, the charts had OAT as a variable. Grrrr. Been too long.
It has been some years, but I used to teach a special circular autorotation scan (Seahawk) that accounted for line up/spot (target) position in windscreen, airspeed & NR (really needed to be scanned together), altitude/radalt (depends on phase of auto ...) and ball, then back out. It was my teaching approach that the key to a good auto is a good entry (down right idle turn was the Jet Ranger mantra, but "control Nr and Airspeed is generic as a truth) followed by a fast and sustained scan, with corrections to match.
We fixed quite a few problems among novices with teaching them the scan, and what corrections / counter corrections (every correction has a counter correction, doesn't it?) got you the performance you were looking for.
I see some advanced skills being discussed here. Is it fair to say autos to a spot are an advanced skill? (Is that the consensus in the civil world? I am a few years out of date here).
I tip my cap (seriously!) to those who know their aircraft well enough to control airspeed through visual reference to horizon, outside reference, and Nr by audio cues.
If you practice enough, and have a decent outside ref, you can estimate flare height. Without a radalt, that's a required visual skill to learn early in life, but if I recall, flare height is somewhat model dependent.
For our OP: has your instructor taught you a specific autorotation scan?
A tailored scan for a task seems a good way to stay ahead of the aircraft.
for hueyracer: we adjusted auto rpm after every maintenance check flight, usually adjusted for season and weight. (The procedure was in the maintenance manuals). The idea was that you'd have a ballpark "good" NR if you lost engines, or had to auto for other reasons, seasonally adjusted.
Now that I think of it, the charts had OAT as a variable. Grrrr. Been too long.
Before we give hueyracer a hard time is he having a problem with his English ?
If not then blimey, all helicopters that I know of have to have their autorevs adjusted, otherwise you can end up having all sorts of fun in autos !! So who passes German air test pilots then ?
If not then blimey, all helicopters that I know of have to have their autorevs adjusted, otherwise you can end up having all sorts of fun in autos !! So who passes German air test pilots then ?