Robinson R22 Corner [Archive copy]
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Sir:
With all due respect, two questions:
Do you comprehend the usual response from any helicopter that you have loaded to over 96% of maximum, hovered it at an rather high density altitude, and then practiced *left* pedal turns
How "hard" can any helicopter land *from 12 inches* above the ground with even total power loss. ?
In My Humble Opinion, Instructors often demo hovering autos from that altitude, and even if PIC does nothing (except apply pedal to maintain heading), the helicopter does not land "hard".
With all due respect, two questions:
Do you comprehend the usual response from any helicopter that you have loaded to over 96% of maximum, hovered it at an rather high density altitude, and then practiced *left* pedal turns
How "hard" can any helicopter land *from 12 inches* above the ground with even total power loss. ?
In My Humble Opinion, Instructors often demo hovering autos from that altitude, and even if PIC does nothing (except apply pedal to maintain heading), the helicopter does not land "hard".
Aren't R22 (and R44) engines derated, so even if you were using full power the butterfly valve would not have been fully open, increasing the likelyhood of carb ice?
Russell
1840hrs turbine heli
5 hrs piston heli
so I may be talking out of my ar5e....tell me!
Russell
1840hrs turbine heli
5 hrs piston heli
so I may be talking out of my ar5e....tell me!
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Possible cause of hard landing
Alpinehelicopter,
Perhaps a pertinent question to ask would be; what characterized the terrain over which you were hovering?
If it was long grass or similar, the effects of recirculation could have substantially reduced the ground cushion which resulted in the hard landing you describe.
While by no means the sole cause, it could be a contributing factor.
Kind Regards
Bluegold
Perhaps a pertinent question to ask would be; what characterized the terrain over which you were hovering?
If it was long grass or similar, the effects of recirculation could have substantially reduced the ground cushion which resulted in the hard landing you describe.
While by no means the sole cause, it could be a contributing factor.
Kind Regards
Bluegold
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R22 B2 Power Loss
At that altitude, did you have much carb heat on? Reason i ask is beacuse if you have full carb heat on and give it loads of left pedal, did you sneak by the 25 inches of manifold pressure 
When was the last maintenance done on the aircraft, and like Bluegold said, what sort of terrain were you hovering over? Did you establish what the Dew point was?
Sorry to ask, but it could all be relevent.
MD 900
When was the last maintenance done on the aircraft, and like Bluegold said, what sort of terrain were you hovering over? Did you establish what the Dew point was?
Sorry to ask, but it could all be relevent.
MD 900
Overboosted Mr Selfish??
Don't think so. If this robbie had been boosted it would not have hit the ground hard. The turbo would've pressurised the intake and forced atomised particles of air and fuel into the cylinder mimicing the characteristics of sealevel operation.
Since the R22 is not fitted with a turbo this is very impossible. Like you correctly said: the redline is the "derating". The limit is when the collective and the throttle will travel no further in a positive direction.
If this really did end in a hard destructive landing, then it is a sad example of how many people are being taught bad habits early on by inexperienced instructors. Like TMFlyer says.....12 inches is not a long way off the planet.
Carb icing is insidious. It won't end in a sudden power loss but a gradual degradation. In this case being at full throttle would negate this occuring as it usually occurs around the throttle butterfly during a partial open position. Hense why you apply carb heat prior to decent.
Don't think so. If this robbie had been boosted it would not have hit the ground hard. The turbo would've pressurised the intake and forced atomised particles of air and fuel into the cylinder mimicing the characteristics of sealevel operation.
Since the R22 is not fitted with a turbo this is very impossible. Like you correctly said: the redline is the "derating". The limit is when the collective and the throttle will travel no further in a positive direction.
If this really did end in a hard destructive landing, then it is a sad example of how many people are being taught bad habits early on by inexperienced instructors. Like TMFlyer says.....12 inches is not a long way off the planet.
Carb icing is insidious. It won't end in a sudden power loss but a gradual degradation. In this case being at full throttle would negate this occuring as it usually occurs around the throttle butterfly during a partial open position. Hense why you apply carb heat prior to decent.
Stretching the memory, but with carb icing there is a couple of kinds.
Throttle icing as previously discussed, usually around a partially open throttle as the airflow velocity increases and the pressure drops, cooling the air to freezing.
There is also fuel icing, a cooling effect from the introduction of fuel as it soaks up latent heat energy to vaporise, like when you spill gas on your skin it feels cold. This is downstream of the throttle butterfly and can tip the temperature below freezing.
What I am trying to say is icing can occur in the carby and also downstream in the intake manifold, despite being at full throttle.
Throttle icing as previously discussed, usually around a partially open throttle as the airflow velocity increases and the pressure drops, cooling the air to freezing.
There is also fuel icing, a cooling effect from the introduction of fuel as it soaks up latent heat energy to vaporise, like when you spill gas on your skin it feels cold. This is downstream of the throttle butterfly and can tip the temperature below freezing.
What I am trying to say is icing can occur in the carby and also downstream in the intake manifold, despite being at full throttle.
'alpinehelicopter' is very quiet!
'Floppy', I gotta tell ya. .
As you can see from the graph, in those conditions, full throttle is around 23.5"
I don't know why everyones bangin' on about carb icing!
Verdict: Overpitched
'Floppy', I gotta tell ya. .
As you can see from the graph, in those conditions, full throttle is around 23.5"
I don't know why everyones bangin' on about carb icing!
Verdict: Overpitched
The last time I was at 9000ft in an R22, I confirmed that the throttle and the collective will come to the end of their travel at the same time. It was mostly a coincidence but interesting none the same. Without the fancy smancy lift formula it is apparent that the MR will bleed off.....
Mr Selfish: "Over boosting" is a completely wrong term here for what happens when you exceed the redline on an R22. Unfortunately you are one of the many (engineers I have worked with included) who use this term incorrectly. It is the result of poor theory instruction in Aussie. I have never heard the term used elsewhere.
Overboosting is terminology used for super/turbo charged engines indicating that you are exceeding the allowable positive pressurisation of the cylinders for that power/throttle/engine condition. The result is detonation and wear to the piston and cylinder as it opposes the increasing pressure while the piston rises during the compression stroke.
SO! you cannot "overboost" a non-boosted engine....just impossible.
There is no term for using all the engines power and ignoring a little redline. Musterers have been doing it since last century.
The ramifications are increased wear....(maybe) and decreased component times. Despite the redline I know of very few O-520's that make it to a 2200hr overhaul without having new cylinders and pistons fitted.
I think Lu has a term stashed away somewhere for this ......
Mr Selfish: "Over boosting" is a completely wrong term here for what happens when you exceed the redline on an R22. Unfortunately you are one of the many (engineers I have worked with included) who use this term incorrectly. It is the result of poor theory instruction in Aussie. I have never heard the term used elsewhere.
Overboosting is terminology used for super/turbo charged engines indicating that you are exceeding the allowable positive pressurisation of the cylinders for that power/throttle/engine condition. The result is detonation and wear to the piston and cylinder as it opposes the increasing pressure while the piston rises during the compression stroke.
SO! you cannot "overboost" a non-boosted engine....just impossible.
There is no term for using all the engines power and ignoring a little redline. Musterers have been doing it since last century.
The ramifications are increased wear....(maybe) and decreased component times. Despite the redline I know of very few O-520's that make it to a 2200hr overhaul without having new cylinders and pistons fitted.
I think Lu has a term stashed away somewhere for this ......
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a little more detailed
Thank you all for your anwers!
I have to be more clear about the situation we had:
-carb heat wasn't applied (down)
-it was a cut grass surface
-we had already hovered 2min before we lost rpm
-the power we applied (when rpm dropped): 23 inches Manifold Pressure
-the rpm dropped very abrupt (lower than 97% in less than a 1sec)
-when the rpm dropped we had already stopped the turn
-weight was within limit with the RFM
-RFM says it's possible to hover IGE up to 10000ft (PA) with the weight we had
An other question:
-When full power is used (butterfly at approx. 45° open) what about the possibilty to risk carb icing?
Greetings.
I have to be more clear about the situation we had:
-carb heat wasn't applied (down)
-it was a cut grass surface
-we had already hovered 2min before we lost rpm
-the power we applied (when rpm dropped): 23 inches Manifold Pressure
-the rpm dropped very abrupt (lower than 97% in less than a 1sec)
-when the rpm dropped we had already stopped the turn
-weight was within limit with the RFM
-RFM says it's possible to hover IGE up to 10000ft (PA) with the weight we had
An other question:
-When full power is used (butterfly at approx. 45° open) what about the possibilty to risk carb icing?
Greetings.
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Food for thought...
You can get carb icing if the degree difference between dew point and OAT is 20F/11C. Since you had a 15F/8C difference, it is likely that you experienced carb icing (it was already pretty cold that day).
As far as engine performance is concerned, the O-360-J2A (Lycoming engine for Beta II) was designed at 180 BHP; however, Lycoming only tested it at 145 BHP because they thinned-out the cylinder heads and used Aluminum pistons to save weight (and they wanted to cover their tail feathers). The engine is fully capable of producing 180 BHP, but the data plate says 145 BHP. So that's what we go by. If you stay within POH limits, you should not exceed 131 BHP. Why did RHC specify 131 BHP in their design?
In piston engines, you loose about 7 horsepower for every thousand feet (roughly). It's the pilot that derates the engine by staying within MP limits, which affects your angle of attack on the blades. There isn't really a mechanical device that "derates" the engine... just the pilot.
Therefore, at 7000' you have every bit of that 131 horsepower available to you...
180 HP
- 7 (thousand) x 7 HP = 49
--------------------------
131 HP
Schweizer's web site claims the 300 has a HIGE of 10,800 feet. This is a sneaky advertisment because this is at a weight of about 1400 pounds... one person and an hour of fuel. At gross weight, the Schweitzer can only handle 5,900 feet.
Piston helicopters that operate at their maximum horsepower at all times are not high altitude performers. Specifically, the performance power available to their engines is extremely limited when compared to the Beta II at the same altitude because you are subtracting from an available horsepower figure that was running at maximum at sea level! In other words, they don't have the same altitude "buffer" that the R22 Beta II does.
The Beta I and Beta II are almost the exact same aircraft. A few minor changes, but the biggest difference is the engine. So if you fly mostly at lower alititudes, you will NOT have ANY performance increase from a Beta II vs. Beta I. If you fly at higher altitudes, you will need the Beta II.
One more thing, most folks don't know how to properly use the chart that Johe02 posted earlier. You are probably already aware of this, so forgive me if I'm speaking in infant terms...
There is a reason why the MAP lines extend past the "full throttle" line. The extension is used to calculate your max continuous power. Example...
Assume 6000 MSL @ 0 C
To calculate your 5-minute MAP rating, you simply follow the chart. Go to 6 line at bottom and follow it up to the 0 C line to find your 5-minute MAP rating. In this case, you run into the "full throttle" line BEFORE reaching the 0 C line. Therefore, your 5-minute MAP rating is about 23.5 inches.
Now, the chart says, "for MCP subtract 1 inch MAP." Without putting much thought into it, that's exactly what most people do... and that's exactly the wrong thing to do. To calcualte your max continuous power rating, you subtract 1 inch MAP from the calculated 5-minute MAP rating!
Now, the reason for the extended MAP lines beyond the full throttle mark becomes clear. The calculated 5-minute MAP rating in this scenario is 24 inches (actual 5-minute MAP rating is 23.5 inches at full throttle). If you subtract 1 inch from the calculated 5-minute MAP rating, your max continuous power rating is 23 inches.
In summary the difference between your actual 5-minute MAP rating and your max continuous power rating is only 0.5 inches in this case (not the full 1 inch). If you use the "full throttle" line instead of the calculated 5-minute MAP rating, you will cheat yourself a little power.
Hope this helps.
(edited for grammar & spelling)
As far as engine performance is concerned, the O-360-J2A (Lycoming engine for Beta II) was designed at 180 BHP; however, Lycoming only tested it at 145 BHP because they thinned-out the cylinder heads and used Aluminum pistons to save weight (and they wanted to cover their tail feathers). The engine is fully capable of producing 180 BHP, but the data plate says 145 BHP. So that's what we go by. If you stay within POH limits, you should not exceed 131 BHP. Why did RHC specify 131 BHP in their design?
In piston engines, you loose about 7 horsepower for every thousand feet (roughly). It's the pilot that derates the engine by staying within MP limits, which affects your angle of attack on the blades. There isn't really a mechanical device that "derates" the engine... just the pilot.
Therefore, at 7000' you have every bit of that 131 horsepower available to you...
180 HP
- 7 (thousand) x 7 HP = 49
--------------------------
131 HP
Schweizer's web site claims the 300 has a HIGE of 10,800 feet. This is a sneaky advertisment because this is at a weight of about 1400 pounds... one person and an hour of fuel. At gross weight, the Schweitzer can only handle 5,900 feet.
Piston helicopters that operate at their maximum horsepower at all times are not high altitude performers. Specifically, the performance power available to their engines is extremely limited when compared to the Beta II at the same altitude because you are subtracting from an available horsepower figure that was running at maximum at sea level! In other words, they don't have the same altitude "buffer" that the R22 Beta II does.
The Beta I and Beta II are almost the exact same aircraft. A few minor changes, but the biggest difference is the engine. So if you fly mostly at lower alititudes, you will NOT have ANY performance increase from a Beta II vs. Beta I. If you fly at higher altitudes, you will need the Beta II.
One more thing, most folks don't know how to properly use the chart that Johe02 posted earlier. You are probably already aware of this, so forgive me if I'm speaking in infant terms...
There is a reason why the MAP lines extend past the "full throttle" line. The extension is used to calculate your max continuous power. Example...
Assume 6000 MSL @ 0 C
To calculate your 5-minute MAP rating, you simply follow the chart. Go to 6 line at bottom and follow it up to the 0 C line to find your 5-minute MAP rating. In this case, you run into the "full throttle" line BEFORE reaching the 0 C line. Therefore, your 5-minute MAP rating is about 23.5 inches.
Now, the chart says, "for MCP subtract 1 inch MAP." Without putting much thought into it, that's exactly what most people do... and that's exactly the wrong thing to do. To calcualte your max continuous power rating, you subtract 1 inch MAP from the calculated 5-minute MAP rating!
Now, the reason for the extended MAP lines beyond the full throttle mark becomes clear. The calculated 5-minute MAP rating in this scenario is 24 inches (actual 5-minute MAP rating is 23.5 inches at full throttle). If you subtract 1 inch from the calculated 5-minute MAP rating, your max continuous power rating is 23 inches.
In summary the difference between your actual 5-minute MAP rating and your max continuous power rating is only 0.5 inches in this case (not the full 1 inch). If you use the "full throttle" line instead of the calculated 5-minute MAP rating, you will cheat yourself a little power.
Hope this helps.
(edited for grammar & spelling)
Mr Selfish,
I didn't have a Beta II chart handy. Just wanted to show that alpinehelicopter was hovering at or close to full throttle.
All those graphs and figures assume a perfect engine, (and correct weights!?). It only needs the timing or valve adjustment to be slightly out (even old oil) and you've got less power than expected.
Maybe the engine was hot from being over worked at that PA?
I still think he overpitched. Carb icing is for small throttle openings, where the pressure difference across the butterfly is great.
Either way I don't think he's gonna strip the engine. . .
I didn't have a Beta II chart handy. Just wanted to show that alpinehelicopter was hovering at or close to full throttle.
All those graphs and figures assume a perfect engine, (and correct weights!?). It only needs the timing or valve adjustment to be slightly out (even old oil) and you've got less power than expected.
Maybe the engine was hot from being over worked at that PA?
I still think he overpitched. Carb icing is for small throttle openings, where the pressure difference across the butterfly is great.
Either way I don't think he's gonna strip the engine. . .
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Alpinehelicopter
To answer your throttle question, yes, carb-ice is very possible at, or close to, full throttle in an R22. The reason, as you state and as others have pointed out above, is that the engine is derated and the butterfly is not wide open.
The information you add in your second post reinforces the likelihood of carb-ice. Hovering over grass can recirculate the moisture necessary to produce the ice. You state you had nil wind conditions. This just helps the recirculation process. And you'd been there for two minutes already. Perfect for ice!
I'd still get the machine checked over for all other possibles. Your 'hard' landing should be checked too if you suspect damage may have been done.
I am not a little disconcerted to read amongst the above that some of us here cannot see the likelihood of carb-ice in this case. Having done a lot of work on this subject I can assure you carb-ice in Robinsons is very possible under a surprisingly wide variety of conditions. Given that pulling out the carb-heat control costs nothing (well, almost nothing) to keep that temp needle out of the yellow arc, the rule here just has to be:::
"If in doubt, pull it out"
The information you add in your second post reinforces the likelihood of carb-ice. Hovering over grass can recirculate the moisture necessary to produce the ice. You state you had nil wind conditions. This just helps the recirculation process. And you'd been there for two minutes already. Perfect for ice!
I'd still get the machine checked over for all other possibles. Your 'hard' landing should be checked too if you suspect damage may have been done.
I am not a little disconcerted to read amongst the above that some of us here cannot see the likelihood of carb-ice in this case. Having done a lot of work on this subject I can assure you carb-ice in Robinsons is very possible under a surprisingly wide variety of conditions. Given that pulling out the carb-heat control costs nothing (well, almost nothing) to keep that temp needle out of the yellow arc, the rule here just has to be:::
"If in doubt, pull it out"
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For RDRickster:
Just a question on your detailed response- didn't you mean the maximum MAP you could get is 22.5" - that's where the full throttle line crosses at 6,000'?
How can you get more MAP than full throttle?
Otherwise, an excellent post.
Just a question on your detailed response- didn't you mean the maximum MAP you could get is 22.5" - that's where the full throttle line crosses at 6,000'?
How can you get more MAP than full throttle?
Otherwise, an excellent post.
Dantruck,
Full throttle is full throttle my friend, butterfly as open as it can be. Perhaps you mean at or close to max POWER that you can use according to the limit chart, that the butterfly is not wide open?
It is by adhering to the limit chart that the pilot "derates" the engine at lower altitudes, but as you climb you will eventually be running at full throttle and quite within the stated limits.
I still think carby icing is also possible at full throttle due to fuel and/or impact icing and not throttle icing. Can any of you icing guru's prove me right or wrong?
Alpinehelicopter,
There is also the possibility you had a stuck valve momentarily, although the engine will run very noticeably rough as it drops a cylinder. It may have only done it for a couple of strokes though. How "sudden" was your power loss?
Full throttle is full throttle my friend, butterfly as open as it can be. Perhaps you mean at or close to max POWER that you can use according to the limit chart, that the butterfly is not wide open?
It is by adhering to the limit chart that the pilot "derates" the engine at lower altitudes, but as you climb you will eventually be running at full throttle and quite within the stated limits.
I still think carby icing is also possible at full throttle due to fuel and/or impact icing and not throttle icing. Can any of you icing guru's prove me right or wrong?
Alpinehelicopter,
There is also the possibility you had a stuck valve momentarily, although the engine will run very noticeably rough as it drops a cylinder. It may have only done it for a couple of strokes though. How "sudden" was your power loss?
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With carb heat, always, always keep the inlet temperature out of the yellow. I always fly with +10.
And be aware that the "temperature assist" doesn't always do you favours. As you transition and reduce power, the carb heat knob actually drops. If you are doing training across the airfield, you'll more than likely be constantly starting and stopping exercises frequently. Make sure the knob is always up at least an inch.
I'm not a great fan of the temp assist mechanism - it never seems to assist when you need it and its reactions in no way reflect the actual inlet temperature.
And be aware that the "temperature assist" doesn't always do you favours. As you transition and reduce power, the carb heat knob actually drops. If you are doing training across the airfield, you'll more than likely be constantly starting and stopping exercises frequently. Make sure the knob is always up at least an inch.
I'm not a great fan of the temp assist mechanism - it never seems to assist when you need it and its reactions in no way reflect the actual inlet temperature.
rotordk:
There's nothing in the POH which recommends leaning the mixture in an R22, it's not taught (to my knowledge) and as far as I remember I've never done it nor spoken with anyone who has.
In my defence, if I'm wrong, I can't get to my copy of the POH cos it's packed away cos we're moving house next week!
There's nothing in the POH which recommends leaning the mixture in an R22, it's not taught (to my knowledge) and as far as I remember I've never done it nor spoken with anyone who has.
In my defence, if I'm wrong, I can't get to my copy of the POH cos it's packed away cos we're moving house next week!