R22 Corner
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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)
Last edited by RDRickster; 19th Nov 2003 at 09:16.
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!
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They put it there for a reason, and we are allowed to think for ourself, even though it's not SOP ( Yeah, I know, but hey.......it could save your as* one day !!! ).
Ofcourse any leaning will be performed on the ground ( if I recall correctly, their lawyers don't recommend inflight mixture manipulation ). !!
Ofcourse any leaning will be performed on the ground ( if I recall correctly, their lawyers don't recommend inflight mixture manipulation ). !!
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Dropping a Robinson
Information wanted please. I am trying to to do some evaluation on skid setups, and would be interested on any information from anyone who has had engine failure or other problems which have necessitated dropping a Robinson from eight feet or less, from a hover. I refer to structural damage rather than the cause. Many thanks, Bug.
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I'm assuming that you live somewhere that makes it inconvenient to attend the factory school - a pity, as it's a great school. Anyway, in the school they show you video tapes of their products being dropped (not hover auto - cut-the-string dropped) while they measure the skid distension.
I'd suggest you call RHC and ask to talk to Ken Martin or Pat Cox and see if they can get you some numbers.
I'd suggest you call RHC and ask to talk to Ken Martin or Pat Cox and see if they can get you some numbers.
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As part of the certification testing of the R22, they did some drop tests. RHC have a video which, as has been mentioned, is shown on their course. Its quite impressive to see how much the skids deflect, and then return.
From experience doing instruction, the R22 skids are pretty good at resisting damage from "drops": much more so than many other apparently stronger helicopters. However, helicopters can be dropped in various ways. Sometimes, even when the drop is not large, it can be awkward. If the drop is not just straight down, but has a lateral element, you can get damage. Not necessarily the skids, but damage to the MR gearbox and/or its fairing.
From experience doing instruction, the R22 skids are pretty good at resisting damage from "drops": much more so than many other apparently stronger helicopters. However, helicopters can be dropped in various ways. Sometimes, even when the drop is not large, it can be awkward. If the drop is not just straight down, but has a lateral element, you can get damage. Not necessarily the skids, but damage to the MR gearbox and/or its fairing.
Senis Semper Fidelis
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If a Robbo is dropped or put down hard and nearly level at impact , this can be seen after the event in the cross member at the rear of the cabin will show varying stages of deformity IE it wont be straight the bigger the bend the harder the hit, after that it in the other things like the tail boom drooping and the rotor mast moving(deflecting) so much that it will deform the roof around where it pokes out from the main body!
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Dropping an R22 may increase the bend in the beam that VFR mentions - however it is bent to some extent as it comes out the factory, so don't reject an R22 just because it is bent.
If I remember right, RHC specify a check of the height of the tail stinger above level ground as part of the check after a heavy landing - it will all be in the maintenance manual. Presumably it effectively checks that any deformation of the skids was elastic and that the skids system remains within limits.
I guess what I was trying to say earlier is that, in my experience you are more likely to get damage from drops, in practice, away from the skids.
If I remember right, RHC specify a check of the height of the tail stinger above level ground as part of the check after a heavy landing - it will all be in the maintenance manual. Presumably it effectively checks that any deformation of the skids was elastic and that the skids system remains within limits.
I guess what I was trying to say earlier is that, in my experience you are more likely to get damage from drops, in practice, away from the skids.
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R22 overspeed query
Hi - can anyone tell me why some sort of engine rpm limiter could not be incorporated into the design of an R22/R44?
It seems that a lot of low time pilots waste a fair amount of cash coughing up for accidental engine overspeeds and R22s remain grounded pending inspections when e.g. starting up with the throttle open or raising the collective without the governor on and not reacting quickly enough to reduce rpm.
Thanks
It seems that a lot of low time pilots waste a fair amount of cash coughing up for accidental engine overspeeds and R22s remain grounded pending inspections when e.g. starting up with the throttle open or raising the collective without the governor on and not reacting quickly enough to reduce rpm.
Thanks
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I don't need no stinking limits.
To: rba194
Some automotive engines have over speed limiters, which either cut off the fuel supply or cut the ignition. On an automotive engine when you stop ignition or fuel the rear/front wheels through the transmission are still back driving the engine.
On the Robbie or any other helicopter the internal combustion engine is isolated by the free wheeling unit and when any overspend device were actuated the engine would most likely stop.
To put some type of limiter on an existing engine it would require re certification or that an STC be issued which would require much less paperwork than a full re certification.
Many years ago the US Army took delivery of a brand new H-34. A new pilot was transitioning from H-13s to the H-34. He started the engine while twisting or untwisting the throttle trying to get fuel pumped into the engine. The throttle canceller switch was misrigged and the engine caught with the throttle wide open. The engine went to 2800 RPM and there was so much force in the hydromechanical clutch that it broke and the engine was connected to the driveline. It took only one second under those conditions to make that brand new H-34 a write-off and it was taken to the training school as a training aid.
Some automotive engines have over speed limiters, which either cut off the fuel supply or cut the ignition. On an automotive engine when you stop ignition or fuel the rear/front wheels through the transmission are still back driving the engine.
On the Robbie or any other helicopter the internal combustion engine is isolated by the free wheeling unit and when any overspend device were actuated the engine would most likely stop.
To put some type of limiter on an existing engine it would require re certification or that an STC be issued which would require much less paperwork than a full re certification.
Many years ago the US Army took delivery of a brand new H-34. A new pilot was transitioning from H-13s to the H-34. He started the engine while twisting or untwisting the throttle trying to get fuel pumped into the engine. The throttle canceller switch was misrigged and the engine caught with the throttle wide open. The engine went to 2800 RPM and there was so much force in the hydromechanical clutch that it broke and the engine was connected to the driveline. It took only one second under those conditions to make that brand new H-34 a write-off and it was taken to the training school as a training aid.
rba:
Point taken - I've been there
To my mind, if the pilot follows the checklist, they're safe, and it's incumbent on the school to teach well enough to avoid it - not only in the "this is what you do and don't do" but "this is the time you concentrate on one task" sort of stuff.
Adding technology probably means the aircraft will be grounded with a limiter fault more often anyway.
Point taken - I've been there
To my mind, if the pilot follows the checklist, they're safe, and it's incumbent on the school to teach well enough to avoid it - not only in the "this is what you do and don't do" but "this is the time you concentrate on one task" sort of stuff.
Adding technology probably means the aircraft will be grounded with a limiter fault more often anyway.