Robinson R22 Corner [Archive copy]
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Blenderpilot,
in defense of all the people doing their initial training in Robinson products: It is not the fault of the R22/R44 AIRCRAFT if the overcontroling issue isn't taken care of. One rather has to blame the instructor for not correcting this.
When I did my first turbine transition (to a TwinStar) we had two guys in the class who had a lot of Robibson time and the Factory instructor kept coming with stupid remarks to the "two Robinson guys". Just as if we didn't know s*** about flying anything. When we all started on the flying part of the course, everybody got the chance to twice sit in the back on somebody elses flight. I couldn't believe my eyes (and ears). They were mostly Bell drivers (JetRanger). They peformed as good asthey could, but you should have heard those high and low RPM horns in their autorotations. Plus they had plenty problem to get used to this new machine. At the last meeting the Instructor had everybody together and said that he had greatly underestimated the Robinson as a trainer, because the "two Robinson guys" really were the ones who caught on best with the new machine. I must give him credit for standing up and say that.
So once again: If somebody has learned how to fly a Robinson WELL - he can learn to fly any other helicopter!! If the R22 wasn't such a good trainer as it is, why would 95% of all civilian training be conduted in it???
sp
in defense of all the people doing their initial training in Robinson products: It is not the fault of the R22/R44 AIRCRAFT if the overcontroling issue isn't taken care of. One rather has to blame the instructor for not correcting this.
When I did my first turbine transition (to a TwinStar) we had two guys in the class who had a lot of Robibson time and the Factory instructor kept coming with stupid remarks to the "two Robinson guys". Just as if we didn't know s*** about flying anything. When we all started on the flying part of the course, everybody got the chance to twice sit in the back on somebody elses flight. I couldn't believe my eyes (and ears). They were mostly Bell drivers (JetRanger). They peformed as good asthey could, but you should have heard those high and low RPM horns in their autorotations. Plus they had plenty problem to get used to this new machine. At the last meeting the Instructor had everybody together and said that he had greatly underestimated the Robinson as a trainer, because the "two Robinson guys" really were the ones who caught on best with the new machine. I must give him credit for standing up and say that.
So once again: If somebody has learned how to fly a Robinson WELL - he can learn to fly any other helicopter!! If the R22 wasn't such a good trainer as it is, why would 95% of all civilian training be conduted in it???
sp
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sierra-papa (" mountain-potato" translated to spanish)
I haven't said that flying R22 for training was a waste of time, I just said the machine has a tendency to develop nasty habits in pilots, (I guess like flying any other helicopter good habits too) If you ask me the reason why soo many people fly the "thing", its because its cheap, and easy to mantain, I think the Hughes is a far better trainer it just hasn't been properly marketed, big schools like HAI are switching and that is no coincidence, I think its because a lot of their students go straight to Pro Pilot Jobs in turbine helicopters and their transition was more difficult coming from the R22.
You say its up to the instructor to correct things like overcontrolling, most R22 instructors have a couple hundred more hours than the student, they think stirring the cyclic is normal!
As for the transition course anecdote, that might have been the case there, but its usually not like that.
Makes me wonder if basic training is the same why doesn't the US Army, (and other armed forces of the world) do their basic training in R22's or similar types? Its just not the same.
You say its up to the instructor to correct things like overcontrolling, most R22 instructors have a couple hundred more hours than the student, they think stirring the cyclic is normal!
As for the transition course anecdote, that might have been the case there, but its usually not like that.
Makes me wonder if basic training is the same why doesn't the US Army, (and other armed forces of the world) do their basic training in R22's or similar types? Its just not the same.
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The Bristow Flying Training School (alas since closed down) used to carry out sponsored CPL(H) training for many of its pilots. It purchased 6 Robinson R22s in December 1987 and they replaced their fleet of Bell 47s in early 1988. There were no Robinsons fitted with governors then and I don't believe there were any instances of rotor overspeeds either. The fact that the Robinson has one of the best throttle correlators of any piston helicopter probably had something to do with it. At the time I think that it was the biggest commercial helicopter training school in Europe and all of the students went straight on to fly either AS332, S76, S61 or Bell 212. I don't recall any of them having any more problems in converting to larger types than those previously trained in Bell 47s, so maybe it has more to do with the quality of the training than the machine in which it was done. All of the Bristow instructors had at least 3000 hours P1 time before instructing on the school.
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Licuadora piloto, normally I agree with most of your opinions, but not this time. I personally have trained in other helicopters then Robinson, and therefor got a good chance to compare them against other products. I am not a sales agent for Robinson or anything like it. I just hate seeing people who have no or little time in a particular aircraft throwing mud at it, thus creating a sense of insecurity in many students who train in it. To give you credit you have at least flown the R22 (a very early version of it). So you have a certain opinion about it and you tell us. Nothing wrong with that. The guys who make the most (anti) noise about the R22 are the ones who have never flown one.
Now a few points, not so much for Blender but more for newcomers to the helicopter world:
1. Learning in the R22 makes perfect sense because it prepares a student for the R44 - and the R44 has become the stepping stone into the commercial world for non military trainees (there are more R44 sold per year then all other manufactorers combined). That's why most schools switch to the R22 more that any other aircraft.
2. HAI uses the CB 300 because both companies made a deal. Schweizer (the Helicopter division) would probably be gone by now without HAI. And HAI get better prices on buying them then others. By the way HAI also have about 15 R22's. All other bigger schools with predominantly Schweizer aircraft have also Robinsons on the line. There is no way around it.
3. Why has the US army discontinued their use of the H269 (CB 300) if it was such a great trainer?
4. Again, "nasty habits" hae nothing to do with the type aircraft but rather with the human being at the controls. Habits of human beings can be corrected - no problem. Learning to fly the R22 is a little more difficult then other small helos. Once you have achieved a solid skill level in it you can switch with no trouble into any other helicopter.
Greetings from the mountain potato
Now a few points, not so much for Blender but more for newcomers to the helicopter world:
1. Learning in the R22 makes perfect sense because it prepares a student for the R44 - and the R44 has become the stepping stone into the commercial world for non military trainees (there are more R44 sold per year then all other manufactorers combined). That's why most schools switch to the R22 more that any other aircraft.
2. HAI uses the CB 300 because both companies made a deal. Schweizer (the Helicopter division) would probably be gone by now without HAI. And HAI get better prices on buying them then others. By the way HAI also have about 15 R22's. All other bigger schools with predominantly Schweizer aircraft have also Robinsons on the line. There is no way around it.
3. Why has the US army discontinued their use of the H269 (CB 300) if it was such a great trainer?
4. Again, "nasty habits" hae nothing to do with the type aircraft but rather with the human being at the controls. Habits of human beings can be corrected - no problem. Learning to fly the R22 is a little more difficult then other small helos. Once you have achieved a solid skill level in it you can switch with no trouble into any other helicopter.
Greetings from the mountain potato
From the mouth (keyboard, actually) of BlenderPilot:
Hoooo boy. Only "turbine helis" require such cyclic technique? Now there's a misconception for you. No wonder the Robbo gave you such bad habits, old boy. Hate to break this to you, but ALL helicopters need a deft touch on the stick. Yes, even Robbies. Especially Robbies.
You cannot blame the machine. A lot depends on the quality of instruction. But I've seen enough pilots now to make some generalizations. Most R-22 pilots who I've transitioned into bigger equipment do very well. On the other hand, I recently had a high-time fixed-wing pilot come to me fresh from getting his rating in the 300. Whilst hovering, he wagged the 206 cyclic around so horribly that I finally grabbed the stick and "froze" it for him. After showing him that all this wiggle-waggle was unnecessary, he started to calm down. Adding a little cyclic friction helped too, although he was opposed to the idea at first.
This is partially true, I only have 36.5 piston/R22 hours and one of my first flights after the 22, was with a Bell instructor, I remember that one of first things he said to me as I started the 206 and picked it up into a hover was "I can tell you come from an R22 and the first thing we need to do before starting training is get rid of all those nasty R22 habits."
He was mainly talking about overcontrolling, turbine helis should be flown by barely noticable movements of cycilc in precise amounts, giving the exact amount of control pressure to stop any movement, and leaving it in that position until its needed again.
He was mainly talking about overcontrolling, turbine helis should be flown by barely noticable movements of cycilc in precise amounts, giving the exact amount of control pressure to stop any movement, and leaving it in that position until its needed again.
Hoooo boy. Only "turbine helis" require such cyclic technique? Now there's a misconception for you. No wonder the Robbo gave you such bad habits, old boy. Hate to break this to you, but ALL helicopters need a deft touch on the stick. Yes, even Robbies. Especially Robbies.
You cannot blame the machine. A lot depends on the quality of instruction. But I've seen enough pilots now to make some generalizations. Most R-22 pilots who I've transitioned into bigger equipment do very well. On the other hand, I recently had a high-time fixed-wing pilot come to me fresh from getting his rating in the 300. Whilst hovering, he wagged the 206 cyclic around so horribly that I finally grabbed the stick and "froze" it for him. After showing him that all this wiggle-waggle was unnecessary, he started to calm down. Adding a little cyclic friction helped too, although he was opposed to the idea at first.
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I'm only talking from what my economy brain has seen
sierra-papa
"piloto-licuadora" that really made me laugh!
You have some solid points there, I'm sorry I just don't like Robinsons, I don't like pistons, but I'm sure it could be a good trainer. I don't want to discuourage anyone flying the machine.
Maybe my experiences w/the machine haven't been good, but its been 10 years since I've been on one, and there are none around here, (the only way one could fly around here is by droping it from the belly of a C130) so I guess I'm not really qualified to talk about 22's much, I only have 36.5 R22/Piston hrs.
Good luck to all flying R22's out there, have fun. Adios
PF#1
In my personal opinion you don't always seem to have a very clear idea of what you are talking about, but today . . .
You are right, all helicopters should be flown this way, but for some reason I remember 22's not having precise handling qualities, the controls seemed sloppy to me and this led to over controlling, but I guess it was inexperience.
"piloto-licuadora" that really made me laugh!
You have some solid points there, I'm sorry I just don't like Robinsons, I don't like pistons, but I'm sure it could be a good trainer. I don't want to discuourage anyone flying the machine.
Maybe my experiences w/the machine haven't been good, but its been 10 years since I've been on one, and there are none around here, (the only way one could fly around here is by droping it from the belly of a C130) so I guess I'm not really qualified to talk about 22's much, I only have 36.5 R22/Piston hrs.
Good luck to all flying R22's out there, have fun. Adios
PF#1
In my personal opinion you don't always seem to have a very clear idea of what you are talking about, but today . . .
You are right, all helicopters should be flown this way, but for some reason I remember 22's not having precise handling qualities, the controls seemed sloppy to me and this led to over controlling, but I guess it was inexperience.
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Dzeroplus
Method for preventing overspeed with both tachs and governor off, that I was taught anyway, was to very slowly back off the throttle until you get the low RPM horn and light and then just tweek the throttle back open slightly again to stop the warning.
Theory is RPM should be at 98-100%. This needs to be repeated every now and again to retain a reasonable rpm as the correlator can't cope by itself.
This was taught to me by a very experienced R22 instructor, who when I told him that the governor had failed, while I was on a check flight, sadistically said "even better, we can do practise autos with the governor off"...... B%^&$^d
Method for preventing overspeed with both tachs and governor off, that I was taught anyway, was to very slowly back off the throttle until you get the low RPM horn and light and then just tweek the throttle back open slightly again to stop the warning.
Theory is RPM should be at 98-100%. This needs to be repeated every now and again to retain a reasonable rpm as the correlator can't cope by itself.
This was taught to me by a very experienced R22 instructor, who when I told him that the governor had failed, while I was on a check flight, sadistically said "even better, we can do practise autos with the governor off"...... B%^&$^d
Helicopter Pilots Get It Up Quicker
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... I ve always done all my pratice auto with the govenor switched off.
Indeed Section 4.9 and 4.10 of R22 POH states:
PRACTISCE AUTOROTATION - POWER RECOVERY
Switch govenor off and ....
PRACTICE AUTOROTATION - GROUND CONTACT
......perform in same manner as power recovery autorotations....
Or is it another UK specific training method/idea/regulation to leave the govenor switched on?
Indeed Section 4.9 and 4.10 of R22 POH states:
PRACTISCE AUTOROTATION - POWER RECOVERY
Switch govenor off and ....
PRACTICE AUTOROTATION - GROUND CONTACT
......perform in same manner as power recovery autorotations....
Or is it another UK specific training method/idea/regulation to leave the govenor switched on?
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Pilotwolf
Haven't got a clue what the instructor does with the governor switch, just assumed it was slightly harder to recover afterwards with no governor on.
Far too busy kicking rudder pedal, flaring, looking for field with no cows, checking wind direction and undies for skiddies, to worry what the instructor was doing with a poxy little toggler.
Autos.....bloody hate em!!!!
Haven't got a clue what the instructor does with the governor switch, just assumed it was slightly harder to recover afterwards with no governor on.
Far too busy kicking rudder pedal, flaring, looking for field with no cows, checking wind direction and undies for skiddies, to worry what the instructor was doing with a poxy little toggler.
Autos.....bloody hate em!!!!
PPRuNe Enigma
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? Practise autos with the governor off
Not such a big deal surely - once the needles are split the gov. is out of the loop anyway. RPM control whilst in auto is done with a little touch of collective to prevent overspeeds and developing a feel for disk loading.
If you're going all the way to the ground then you'll have the throttle rolled off into the detent anyway - for a power recovery I always preferred the "governor off" approach that we used to do - that way YOU are in control of rematching the needles, rather than have the governor kick in with a surge just when you want to be in control of it.
Not such a big deal surely - once the needles are split the gov. is out of the loop anyway. RPM control whilst in auto is done with a little touch of collective to prevent overspeeds and developing a feel for disk loading.
If you're going all the way to the ground then you'll have the throttle rolled off into the detent anyway - for a power recovery I always preferred the "governor off" approach that we used to do - that way YOU are in control of rematching the needles, rather than have the governor kick in with a surge just when you want to be in control of it.
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Governor on or off for autos? Just a matter of choice I think. I've done both with instructors; each instructor seems to have a preference. If I'm practising them alone with a power recovery, I prefer to have the governor on; it's one less thing to think about. YOU have to join the needles anyway; but then the governor takes over - no big deal.
NigD2,
I hated autos for ages. But after practising them to the ground for what seemed like hours and hours during my CPL course, I suddenly realised they could be fun, and told my instructor that. He reminded me of this during my recent LPC, when I got nervous at the idea of doing autos to the ground, since I'm a bit rusty again. Do enough of 'em, and you might come to love 'em!
NigD2,
I hated autos for ages. But after practising them to the ground for what seemed like hours and hours during my CPL course, I suddenly realised they could be fun, and told my instructor that. He reminded me of this during my recent LPC, when I got nervous at the idea of doing autos to the ground, since I'm a bit rusty again. Do enough of 'em, and you might come to love 'em!
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"regular governor-off refresher training sounds like a very good idea, and perhaps should be part of the annual LPC"
It is where I fly. We also do a new thing on R22 and R44 - the testers pull the tacho cb as a surprise. This is related to a recent incident where a 44 was flying along happily and the tacho dropped to zero. So, the pilot decided to immediately auto. He landed hard and chopped the tail off.
Turned out there was nothing wrong with the engine. The tacho needle/spindle had failed...........
So - might be a good idea to check all pilots for hearing........generally speaking, if the cylinders sound intact, the rotor rpm OK. the airspeed is OK and the VSI isn't diving - you'd think anyone with even half a brai...........sorry. I'll stop. Don't want to get banned.
It is where I fly. We also do a new thing on R22 and R44 - the testers pull the tacho cb as a surprise. This is related to a recent incident where a 44 was flying along happily and the tacho dropped to zero. So, the pilot decided to immediately auto. He landed hard and chopped the tail off.
Turned out there was nothing wrong with the engine. The tacho needle/spindle had failed...........
So - might be a good idea to check all pilots for hearing........generally speaking, if the cylinders sound intact, the rotor rpm OK. the airspeed is OK and the VSI isn't diving - you'd think anyone with even half a brai...........sorry. I'll stop. Don't want to get banned.
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headsethair,
Yes, from the comfort of a desk, or probably even flying with a helluva lot of rotary hours behind you, you would think that anyone with half a.... But up there when you haven't had that much experience and something goes wrong, and you know you have to do something but you're scared and your brain's slowed down as a result...it's all too easy to make the wrong decision. I know; I've been there.
Yes, from the comfort of a desk, or probably even flying with a helluva lot of rotary hours behind you, you would think that anyone with half a.... But up there when you haven't had that much experience and something goes wrong, and you know you have to do something but you're scared and your brain's slowed down as a result...it's all too easy to make the wrong decision. I know; I've been there.
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System failures like tachos are not peculiar to R22s of course. In fact, the inbuilt engineering redundancy in R22 RRPM control aids is very high so you will be unlucky not to get some help in RRPM control - (there are 5 separate aircraft systems).
When I did the Bell 206 factory course (which is unbeatable if you fly their aircraft) they made mention of a number of "engine failures" where a perfectly serviceable helicoper was flown into the ground because of a tacho generator failure giving a spurious indication. One of my colleagues had a torque indication failure with other failure indications in an AS355N just a couple of days ago. It all ended uneventfully, fortunately.
Experience can certainly help in these cases, but experience is expensive and difficult to obtain. However, a small part of all that time we spend on the ground waiting to go flying can be usefully spent with the AFM and technical manuals getting to understand how these things work. When something does fail you are in much better shape to intelligently assess the problem. And best of all, you can gain such knowledge at NO COST!
When I did the Bell 206 factory course (which is unbeatable if you fly their aircraft) they made mention of a number of "engine failures" where a perfectly serviceable helicoper was flown into the ground because of a tacho generator failure giving a spurious indication. One of my colleagues had a torque indication failure with other failure indications in an AS355N just a couple of days ago. It all ended uneventfully, fortunately.
Experience can certainly help in these cases, but experience is expensive and difficult to obtain. However, a small part of all that time we spend on the ground waiting to go flying can be usefully spent with the AFM and technical manuals getting to understand how these things work. When something does fail you are in much better shape to intelligently assess the problem. And best of all, you can gain such knowledge at NO COST!
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R22 Performance Chart Interpretation
OK, this one's a little complicated to explain so please bear with me. Any text book I've ever read has said that every degree of temperature deviation off a standard ISA day (15C at sealevel, temperature lapse rate 1.98C for every 1000ft) is equivalent to 120 feet. So on an ISA +10 day (ignoring humidity) a pressure altitude of 0ft should equate to 1200ft of DA. This is easily confirmed by checking a PA/DA conversion chart such as this one from the R22 manual. Pretty standard stuff and up to here no problem (I hope! ) .
Now, if you want to calculate the IGE ceiling for an R22 Beta (at say 1300lbs for the sake of argument) using this IGE Ceiling chart (from the same manual) you will see that your ceiling is 8,500ft of density altitude (point of intersection of ISA line 'Standard Day' with vertical to 1300 lbs). Now at this stage we could stop using the graph and work out the rest in our heads: DA = 8,500ft, ISA +10 day, PA=(8,500-(10x120))=7,300ft also confirmed by aforementioned PA/DA conversion chart.
If however you decide to use the IGE Ceiling chart to calculate your PA, it will give you an answer of 8,000ft PA (intersection of interpolated ISA +10 line (not OAT +10 line!!) with vertical to 1300lbs). So for our 10 degrees of deviation from ISA we have paid a price of only 500ft which equates to 50ft for every degree and not 120ft.
Can anyone explain this discrepancy??? Or have I lost the plot and am incapable of reading a perfomance chart?
If at this stage you are totally lost and wish to brush up on DA and PA calculations, I recommend going to my previous post 'Want something to read?' If you are not totally lost, please enlighten me! Now, where did I leave those Tylenol??
Thanks!
Irlandés
) .Now, if you want to calculate the IGE ceiling for an R22 Beta (at say 1300lbs for the sake of argument) using this IGE Ceiling chart (from the same manual) you will see that your ceiling is 8,500ft of density altitude (point of intersection of ISA line 'Standard Day' with vertical to 1300 lbs). Now at this stage we could stop using the graph and work out the rest in our heads: DA = 8,500ft, ISA +10 day, PA=(8,500-(10x120))=7,300ft also confirmed by aforementioned PA/DA conversion chart.
If however you decide to use the IGE Ceiling chart to calculate your PA, it will give you an answer of 8,000ft PA (intersection of interpolated ISA +10 line (not OAT +10 line!!) with vertical to 1300lbs). So for our 10 degrees of deviation from ISA we have paid a price of only 500ft which equates to 50ft for every degree and not 120ft.
Can anyone explain this discrepancy??? Or have I lost the plot and am incapable of reading a perfomance chart?
If at this stage you are totally lost and wish to brush up on DA and PA calculations, I recommend going to my previous post 'Want something to read?' If you are not totally lost, please enlighten me! Now, where did I leave those Tylenol??
Thanks!
Irlandés
Irlandes, I think it is because you have tried to interpolate from the standard day line - I understand why but since there is only one ISA line on the graph you are only guessing as to where the ISA +10 line would be.
The gradient would be parallel to the standard day line but you can only best guess the spacing using the spacing on the OAT lines.
This may or may not be reasonable but I suspect that Robinson would argue that they did not include such a line on the graph, therefore you shouldn't make one up. If there had been a series of ISA+temp lines then you could actually 'interpolate'.
To be honest the lapse rate is likely to change so much in the real world that assuming it is ISA+10 at altitude just because it is ISA+10 at sea level is asking for trouble. You are better off getting an accurate OAT from either Met reports (balloon ascents) or from the OAT gauge when you get up there.
The NZ handbook on performance is a very good guide and every operator should be made to read it. As a Mil pilot I would have to have a very good reason to operate without OGE performance plus a 5% Thrust margin. I know the light single operators will tell me they could never get the job done if they had to have this much spare performance but the accident statistics speak for themselves.
Planning to land in the mountains with only IGE hover capability is like russian roulette - you only have to get it wrong once!
The gradient would be parallel to the standard day line but you can only best guess the spacing using the spacing on the OAT lines.
This may or may not be reasonable but I suspect that Robinson would argue that they did not include such a line on the graph, therefore you shouldn't make one up. If there had been a series of ISA+temp lines then you could actually 'interpolate'.
To be honest the lapse rate is likely to change so much in the real world that assuming it is ISA+10 at altitude just because it is ISA+10 at sea level is asking for trouble. You are better off getting an accurate OAT from either Met reports (balloon ascents) or from the OAT gauge when you get up there.
The NZ handbook on performance is a very good guide and every operator should be made to read it. As a Mil pilot I would have to have a very good reason to operate without OGE performance plus a 5% Thrust margin. I know the light single operators will tell me they could never get the job done if they had to have this much spare performance but the accident statistics speak for themselves.
Planning to land in the mountains with only IGE hover capability is like russian roulette - you only have to get it wrong once!
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Hey Crab,
thanks for your reply and for taking the time to wade through my post. On a practical level (the one that really counts!) you are of course totally right and I couldn't agree more.
On a purely theoretical level however (please indulge me here), I would suggest that I'm not really guessing where the ISA +10 line is. If you consider that the ISA line intersects the 1300 lb vertical at approx -2 degrees OAT (pretty clear on the graph) which exactly corresponds to the ISA temp at 8,500ft (15-(8.5x2)=-2) then it seems logical that the ISA +10 line must intersect the same 1300 lb vertical at + 8 degrees OAT (-2+10=+8) which on this graph corresponds to 8000 ft PA and not the 7,300 ft I believe it should be. Do you see what I mean? My worry is that the graph tells you that your ceiling is higher than it actually is for ISA + values, i.e. if there is an error, then it's not erring on the side of safety. Obviously the reverse holds true for a 'minus' ISA day where performance improves. Also the same holds true for the R22's OGE graphs. The way I see it, on a 'hot and heavy' day, the graphs are not penalising you as much as they should for non-standard temperatures. Maybe I need glasses...
Ah well, back to the real world...
Irlandés
thanks for your reply and for taking the time to wade through my post. On a practical level (the one that really counts!) you are of course totally right and I couldn't agree more.
On a purely theoretical level however (please indulge me here), I would suggest that I'm not really guessing where the ISA +10 line is. If you consider that the ISA line intersects the 1300 lb vertical at approx -2 degrees OAT (pretty clear on the graph) which exactly corresponds to the ISA temp at 8,500ft (15-(8.5x2)=-2) then it seems logical that the ISA +10 line must intersect the same 1300 lb vertical at + 8 degrees OAT (-2+10=+8) which on this graph corresponds to 8000 ft PA and not the 7,300 ft I believe it should be. Do you see what I mean? My worry is that the graph tells you that your ceiling is higher than it actually is for ISA + values, i.e. if there is an error, then it's not erring on the side of safety. Obviously the reverse holds true for a 'minus' ISA day where performance improves. Also the same holds true for the R22's OGE graphs. The way I see it, on a 'hot and heavy' day, the graphs are not penalising you as much as they should for non-standard temperatures. Maybe I need glasses...
Ah well, back to the real world...
Irlandés
Irlandes, I fully understand your concern and think it is worth highlighting this anomaly on the graph. I would be very interested to see what experienced R22 operators have to say. You could always email it to Frank Robinson and ask, just don't copy it to Lu Z or there will be another conspiracy born!
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Irlandes,
I think the problem is that you are expecting the hover performance of the aircraft to be driven only by the density altitude. For any helicopter, the hover performance is based upon the altitude, temperature and engine power available, as well as the ancilliary limits, such as tail rotor effectiveness.
The gain in hover IGE weight with reduction in altitude is a product of the both rotor efficiency, (which is almost entirely driven by density altitude), and the engine power available, which gains power as altitude is reduced, and also as temperature is reduced.
I believe the hover performance is more strongly influenced by engine power than by rotor efficiency, and you have deduced that from the charts.
As an experiment, look at several constant density altitude conditions, where the temperature is increased considerably, and see if the weight to hover is a constant. I believe the lower temperature conditions should have higher HIGE performance.
I think the problem is that you are expecting the hover performance of the aircraft to be driven only by the density altitude. For any helicopter, the hover performance is based upon the altitude, temperature and engine power available, as well as the ancilliary limits, such as tail rotor effectiveness.
The gain in hover IGE weight with reduction in altitude is a product of the both rotor efficiency, (which is almost entirely driven by density altitude), and the engine power available, which gains power as altitude is reduced, and also as temperature is reduced.
I believe the hover performance is more strongly influenced by engine power than by rotor efficiency, and you have deduced that from the charts.
As an experiment, look at several constant density altitude conditions, where the temperature is increased considerably, and see if the weight to hover is a constant. I believe the lower temperature conditions should have higher HIGE performance.
Join Date: Jun 2002
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Well Nick I've had to rethink my original reply to your post and subsequently deleted it (I was in a dazed and confused state! 
). I did what you suggested using the line of constant 12,600 ft DA on the graph and here are the results...
12,000ft PA, OAT -4 degrees = DA 12,600ft, MAUW = 1100 lbs
10,000ft PA, OAT +17 degrees = DA 12,600ft, MAUW = 1150 lbs
8,000ft Pa, OAT +40 Degrees = DA 12,600ft, MAUW = 1200 lbs
You said that you believed the lower temperature conditions should have higher HIGE performance. But it seems judging by these figures, that DA being equal, performance is increased at the lower altitudes/higher temperatures. This is reflected by the increase in maximum allowed all-up weight. Does that make sense?? Is the piston engine performance therefore more adversely affected by higher altitudes than by higher temperatures for a constant DA? That's the only way it seems to make sense to me. Am I still in a dazed and confused state?
That apart, thanks for throwing light on the error of my assumptions. As usual, it all seems so obvious in hindsight. I always took for granted that an aircraft would perform identically irrespective of the pressure altitude/temperature combination as long as the density altitude didn't change. If only life were so simple! I guess this assumption is only correct for non-powered flight, gliders etc. This for me is a real eye opener and something I thought I understood well needs a bit of reevaluation.
Thanks!
Irlandés
). I did what you suggested using the line of constant 12,600 ft DA on the graph and here are the results...12,000ft PA, OAT -4 degrees = DA 12,600ft, MAUW = 1100 lbs
10,000ft PA, OAT +17 degrees = DA 12,600ft, MAUW = 1150 lbs
8,000ft Pa, OAT +40 Degrees = DA 12,600ft, MAUW = 1200 lbs
You said that you believed the lower temperature conditions should have higher HIGE performance. But it seems judging by these figures, that DA being equal, performance is increased at the lower altitudes/higher temperatures. This is reflected by the increase in maximum allowed all-up weight. Does that make sense?? Is the piston engine performance therefore more adversely affected by higher altitudes than by higher temperatures for a constant DA? That's the only way it seems to make sense to me. Am I still in a dazed and confused state?
That apart, thanks for throwing light on the error of my assumptions. As usual, it all seems so obvious in hindsight. I always took for granted that an aircraft would perform identically irrespective of the pressure altitude/temperature combination as long as the density altitude didn't change. If only life were so simple! I guess this assumption is only correct for non-powered flight, gliders etc. This for me is a real eye opener and something I thought I understood well needs a bit of reevaluation.
Thanks!
Irlandés