AS350 Astar / AS355 Twinstar [Archive Copy]
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Boy this one has become a bit of a contest. The 206 has some things about it that you just need to be aware of, one of the things that has kept me out of trouble, is the slow application of collective, no need to hank pitch, also I have found that just use enough power to do the task you need to do, Ie why pull in 100% when you can do it will 89% for example. A lot of this LTR stuff is to much pitch, to fast, the gov can't keep up, you then get a little rotor droop, and well you get the rotors slowing and you still have all that power pulled in, you get a yaw. Every time I got into one, mostly doing power assurance checks, the yaw would stop as soon as I reduced the power a little. Is the TR on the 206 little on the small side, yep, so you fly knowing that. As for the numbers well yea the 206 is going to be in more accidents and such, because there are a lot of them flying around, Bell sold something like 5000+ of them. All in all the 206 is not a bad helicopter, yes it has some quirks, but all and all if you take good care of it, and fly it well with in the limits rather that at the limit stops, and just don't push it. You could spend the next 20 years flying one and never raise a sweat. It also helps to keep the wind on the nose, but that would be true of any helicopter. Now from what I understand the UH-60 dose loose TR effectiveness ever now and again. Of course you have to have it shot off first.
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BigMike,
I really do not know of any 206III LTE events, perhaps the redesign did help. It could be that it only covered the power/gross weight increases, however.
Please do not misread me on this, I have personally recommended the 206 to at least two folks who became operators, so I have no "agenda" with it. I do believe if you nurse it in the tight spots, it will work. But I am concerned that we decide it represents a good 21st century standard, which is not what I would envision handing to my son.
The situation is so bad that the FAA has approved 412's, 212's and 430's with NO pedal margin, and NO crosswind capability, using a Cat B, 9 passengers or less approval. They undertook this based on the success they had in teaching us to nurse our aircraft, and blame ourselves when our aircraft bit us while in its normal flight envelope. That concept truly concerns me, and is not where we want our industry to go, in the future.
Some lame poster above said I "screached" too much about this, but that is because he hasn't had his helicopter kick his ass, and then have some official with the correct rubber stamp and Advisory Circular tell him it was his fault.
I really do not know of any 206III LTE events, perhaps the redesign did help. It could be that it only covered the power/gross weight increases, however.
Please do not misread me on this, I have personally recommended the 206 to at least two folks who became operators, so I have no "agenda" with it. I do believe if you nurse it in the tight spots, it will work. But I am concerned that we decide it represents a good 21st century standard, which is not what I would envision handing to my son.
The situation is so bad that the FAA has approved 412's, 212's and 430's with NO pedal margin, and NO crosswind capability, using a Cat B, 9 passengers or less approval. They undertook this based on the success they had in teaching us to nurse our aircraft, and blame ourselves when our aircraft bit us while in its normal flight envelope. That concept truly concerns me, and is not where we want our industry to go, in the future.
Some lame poster above said I "screached" too much about this, but that is because he hasn't had his helicopter kick his ass, and then have some official with the correct rubber stamp and Advisory Circular tell him it was his fault.
Join Date: Jul 2002
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To distill:
It's LTE if the helicopter is within its operating envelope, a yaw develops, you run out of pedal and can't stop the yaw.
It's LTA if the helicopter is outside of its operating envelope, a yaw develops, you run out of pedal and can't stop the yaw.
??
Perhaps this is why the FAA has elected to roll it all into the moniker "LTE" - while one is design induced and the other is pilot induced, the results are the same, as is recovery (full pedal, reduce power/torque, get airspeed, fly with the yaw).
It's LTE if the helicopter is within its operating envelope, a yaw develops, you run out of pedal and can't stop the yaw.
It's LTA if the helicopter is outside of its operating envelope, a yaw develops, you run out of pedal and can't stop the yaw.
??
Perhaps this is why the FAA has elected to roll it all into the moniker "LTE" - while one is design induced and the other is pilot induced, the results are the same, as is recovery (full pedal, reduce power/torque, get airspeed, fly with the yaw).
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the difference is very important:
In a helo prone to LTE, the machine screws you
In a machine experiencing LTA, you screw the machine.
Recovery from LTA involves reducing power (torque) down to normal, thus generally reducing from a climb to level, with ground strike as much less probable. Aircraft that experience LTA almost never crash due to it.
Recovering from LTE involves reducing the power from normal to descent, thus almost always assuring that you and the ground can become one. Aircraft that experience LTE often crash because of it.
that being said, if you find yourself spinning to the right, put in full left pedal, carefuly reduce torque, and try to accelerate out of the mess you are in, no matter if you call it LTA, LTE, MTA or FTA (SASless, tell them what FTA means!)
One thing I learned from this thread: there are pilots out there who would allow their helo to spin out of control without putting in full opposite pedal. For what reason would one allow loss of control without fighting the situation with all the tools at your disposal?
In a helo prone to LTE, the machine screws you
In a machine experiencing LTA, you screw the machine.
Recovery from LTA involves reducing power (torque) down to normal, thus generally reducing from a climb to level, with ground strike as much less probable. Aircraft that experience LTA almost never crash due to it.
Recovering from LTE involves reducing the power from normal to descent, thus almost always assuring that you and the ground can become one. Aircraft that experience LTE often crash because of it.
that being said, if you find yourself spinning to the right, put in full left pedal, carefuly reduce torque, and try to accelerate out of the mess you are in, no matter if you call it LTA, LTE, MTA or FTA (SASless, tell them what FTA means!)
One thing I learned from this thread: there are pilots out there who would allow their helo to spin out of control without putting in full opposite pedal. For what reason would one allow loss of control without fighting the situation with all the tools at your disposal?
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I like Nicks definition about pilots screwing machines and machines screwing pilots!!
Didn't have the privilege to get my hands on a Blackhawk (or any derivative) yet, but I am still hoping!
When I started to fly the 206 I had about 1400 hrs on the Bell-47 and about 2000 on the R-44.
Generally I am slow to get used to a new machine, but after about 35 hrs I started to explore the limits of the machine ( or rather MY limits in the machine!)
It took me about 500 hrs to get to the edge in the R-44.
It took about 5 hrs to find the limits in the 206. Still I liked to fly it, until part of the compressor let go - down it went, it flew again 2 weeks later, but I prefer the EC120 hands down.
Back on track - LTE:
Nick talks about the upper edge (economically) of good TRs.
Let me give you a sample of the lower edge:
I don't know wether it still gets demonstrated, but at my first Robinson Safety Course the instructor would demonstrate
(albeit light wind, half fuel, 2 persons on board) a 1 foot hover at 75% RRPM!! This was not to show how a R-44 still stays aloft when RRPM is 29% below nominal ( R's fly at 104% RRPM), but to demonstrate the TE (Tailrotor Efficiency). He still could do a complete pedal turn either side!
He never demoed it at 70%, but would confess, that it gets hard to control there and he would run out of pedal at times!
The same demo in a R-22 is done at 80% - well it is a little more sensitive!
Now when I loose a little MRRPM a times when external cargo is heavy and Density Altitude is high - LTE is no concern EVER!!
If you can't afford a Sikorsky, go for the Robinson - LTE is NOT in the Robinson Vocabulary!
3top
Didn't have the privilege to get my hands on a Blackhawk (or any derivative) yet, but I am still hoping!
When I started to fly the 206 I had about 1400 hrs on the Bell-47 and about 2000 on the R-44.
Generally I am slow to get used to a new machine, but after about 35 hrs I started to explore the limits of the machine ( or rather MY limits in the machine!)
It took me about 500 hrs to get to the edge in the R-44.
It took about 5 hrs to find the limits in the 206. Still I liked to fly it, until part of the compressor let go - down it went, it flew again 2 weeks later, but I prefer the EC120 hands down.
Back on track - LTE:
Nick talks about the upper edge (economically) of good TRs.
Let me give you a sample of the lower edge:
I don't know wether it still gets demonstrated, but at my first Robinson Safety Course the instructor would demonstrate
(albeit light wind, half fuel, 2 persons on board) a 1 foot hover at 75% RRPM!! This was not to show how a R-44 still stays aloft when RRPM is 29% below nominal ( R's fly at 104% RRPM), but to demonstrate the TE (Tailrotor Efficiency). He still could do a complete pedal turn either side!
He never demoed it at 70%, but would confess, that it gets hard to control there and he would run out of pedal at times!
The same demo in a R-22 is done at 80% - well it is a little more sensitive!
Now when I loose a little MRRPM a times when external cargo is heavy and Density Altitude is high - LTE is no concern EVER!!
If you can't afford a Sikorsky, go for the Robinson - LTE is NOT in the Robinson Vocabulary!
3top
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good story, 3top!
the maximum rotor thrust drops by the square of the rotor rpm, so that at 70% rotor, the max thrust is about half what it is at 100% (0.70 x0.70 = 0.49).
the maximum rotor thrust drops by the square of the rotor rpm, so that at 70% rotor, the max thrust is about half what it is at 100% (0.70 x0.70 = 0.49).
I like that screwing definition too!!
3top, good demo. We use it often with the UH-1H during stuck left pedal forward situations.
But please note that you are describing LTA, not LTE when you use that demo to illustrate a point.
3top, good demo. We use it often with the UH-1H during stuck left pedal forward situations.
But please note that you are describing LTA, not LTE when you use that demo to illustrate a point.
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In the EC130 and as well in the new production AS350B3's, there is a potentiometer which monitors yaw movements which will increase the RRPM (thru the fadec) when T/R limits are being reached (when the 10% control margin is getting close). It is increased to something like 402 from 394 for the purpose of providing more T/R authority at those critical times, such as lifting heavy loads in the hover at altitude. Density altitude is also factored into the equation.
To me this supports Nick's comments that overpitching at altitude likely could lead to reaching or exceeding the 10% control margin for the 350's and thus insifficient T/R thrust.
To me this supports Nick's comments that overpitching at altitude likely could lead to reaching or exceeding the 10% control margin for the 350's and thus insifficient T/R thrust.
Interesting idea, squirrel. There must have been some decision making required in the design of it, for example, does it still act if an overtorque, say, would be needed to increase the Nr by the required amount?
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Squirrel and Arm,
The use of the governor to help controllability is a great idea, much in keeping with the idea that the total machine should respond to the mission.
I have personally worked three similar ideas into production, and on them, the overtorque issue was built into the logic, so that the uptrim of Nr was slowed down to match the torque limits available. For those who are wondering what we are talking about, the upbeep of Nr causes a torque increase, so that an overtorque is possible if something is not done to prevent it.
The three areas that I worked on were the Comanche load factor enhancement, where the main rotor is sped up if the aircraft is maneuvered so that stall is prevented, and controllability/maneuverability is enhanced. Another is the use of Nr to trim the best range solution, automatically. The third is the "blow away" limiter on the 76C+ and S-92, where the torque limiter is varied as the rpm droops, so that constant power is available, thus preventing the spiral decay that occurs when a dumb constant torque limit is imposed on the aircraft. If the helo has a constant torque limiter, any hover overtorque is liable to result ina ground contact as power is being reduced by the limiter. Because torque times rpm is power, if the torque is limited and rotor rpm decays, the power is being reduced, so the helo starts a descent, making the pilot pull more collective so that the rpm decays further, and so on, until the ground comes up and smites the helo.
I would bet that the EC people worked the overtorque issue into the logic, perhaps with a slow uptrim rate, or even a limiter to prevent overtorque.
The use of the governor to help controllability is a great idea, much in keeping with the idea that the total machine should respond to the mission.
I have personally worked three similar ideas into production, and on them, the overtorque issue was built into the logic, so that the uptrim of Nr was slowed down to match the torque limits available. For those who are wondering what we are talking about, the upbeep of Nr causes a torque increase, so that an overtorque is possible if something is not done to prevent it.
The three areas that I worked on were the Comanche load factor enhancement, where the main rotor is sped up if the aircraft is maneuvered so that stall is prevented, and controllability/maneuverability is enhanced. Another is the use of Nr to trim the best range solution, automatically. The third is the "blow away" limiter on the 76C+ and S-92, where the torque limiter is varied as the rpm droops, so that constant power is available, thus preventing the spiral decay that occurs when a dumb constant torque limit is imposed on the aircraft. If the helo has a constant torque limiter, any hover overtorque is liable to result ina ground contact as power is being reduced by the limiter. Because torque times rpm is power, if the torque is limited and rotor rpm decays, the power is being reduced, so the helo starts a descent, making the pilot pull more collective so that the rpm decays further, and so on, until the ground comes up and smites the helo.
I would bet that the EC people worked the overtorque issue into the logic, perhaps with a slow uptrim rate, or even a limiter to prevent overtorque.
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Helmet Fire,
of course you a right!
There is no LTE on a Robinson, well maybe at 60% MRRPM.
At some extreme flying (filming - sideways, etc....) I do run out of pedal, but there is never any loss of TR-power anywhere.
It is fun when one goes sideways (anywhere from 100º to 30º),
once you are all up on power and run out of pedal, you reduce power just a smidgen and the helo has TR again!
I can control the angle at full pedal just by changing the speed a little, playing with the collective just so little...
Okay to the TR-demo, PLEASE don't do this to your students or yourself!! It was a factory designed demo to show the great power of the Robinson TR and I think part of it (as a side benefit) to demo the helo won't come falling as a rock just because the low rpm warning starts to yell....
I use 85% at 1 foot hover, light load, If I have to do recurrency training with oldtimers that HAD to change to the R brand - especially if they come screaming down at 110% - 2000' VS in an auto, because of "fear of death by low RRPM!"
I was in a R-22 when it was shown to me (80%RRPM), and I observed it done at 75% in a R-44.
The blades start to cone at an obscene angle!!
Thanks to the coning hinges the stay pretty much straight though!
3top
of course you a right!
There is no LTE on a Robinson, well maybe at 60% MRRPM.
At some extreme flying (filming - sideways, etc....) I do run out of pedal, but there is never any loss of TR-power anywhere.
It is fun when one goes sideways (anywhere from 100º to 30º),
once you are all up on power and run out of pedal, you reduce power just a smidgen and the helo has TR again!
I can control the angle at full pedal just by changing the speed a little, playing with the collective just so little...
Okay to the TR-demo, PLEASE don't do this to your students or yourself!! It was a factory designed demo to show the great power of the Robinson TR and I think part of it (as a side benefit) to demo the helo won't come falling as a rock just because the low rpm warning starts to yell....
I use 85% at 1 foot hover, light load, If I have to do recurrency training with oldtimers that HAD to change to the R brand - especially if they come screaming down at 110% - 2000' VS in an auto, because of "fear of death by low RRPM!"
I was in a R-22 when it was shown to me (80%RRPM), and I observed it done at 75% in a R-44.
The blades start to cone at an obscene angle!!
Thanks to the coning hinges the stay pretty much straight though!
3top
Thanks, Nick. Sounds like some great ideas for making use of newer technology to take the load off the pilot and make things generally more safe and efficient.
Nick,
pity you didn't work for Bell; they could have used some of that logic themselves (along with the "let's save the MGB rather than the airframe" logic!)
pity you didn't work for Bell; they could have used some of that logic themselves (along with the "let's save the MGB rather than the airframe" logic!)
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212man,
No pity here, Bell uses a different philosophy with everything, consistent with holding down the lower cost end of the market (that is not a slur, someone has to fill that market slice!)
The S-58T had the simple torque limiter, it was once all we had. New integre=ated systems allow us to mix variables from all over the aircraft, making it far easier to tailor the behavior more precisely to the need. Ofter, the trick is to think of what the pilot now does, and do that, automatically.
No pity here, Bell uses a different philosophy with everything, consistent with holding down the lower cost end of the market (that is not a slur, someone has to fill that market slice!)
The S-58T had the simple torque limiter, it was once all we had. New integre=ated systems allow us to mix variables from all over the aircraft, making it far easier to tailor the behavior more precisely to the need. Ofter, the trick is to think of what the pilot now does, and do that, automatically.
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All I know is that in the normal Bell 206 L4, if you are not careful about your weight, and you try to take off into a hover too heavy at a high DA, you will find yourself spinning as soon as the skids leave the ground with the pedal all the way to stop, and with about only 80% power applied (TQ), bringing it down again becomes very tricky, if you try to do anything but roll the throttle off.
There is a beautiful video of this, pilot who is taking off from high mountain, starts spininng a foot off the ground, doesn't have TR authority, but has enough power to climb vertically (while spinning of course) then he dives it, recovers control for an instant at about 50 feet, only to loose it again and crash.
Don't know if you can call that LTE, LTA but whatever it is its a very dangerous if you are not careful.
The 407 TR, well that is a completely different story, it will get you out of most trouble, but it will also reach it's limits at altitude if you are not careful.
There is a beautiful video of this, pilot who is taking off from high mountain, starts spininng a foot off the ground, doesn't have TR authority, but has enough power to climb vertically (while spinning of course) then he dives it, recovers control for an instant at about 50 feet, only to loose it again and crash.
Don't know if you can call that LTE, LTA but whatever it is its a very dangerous if you are not careful.
The 407 TR, well that is a completely different story, it will get you out of most trouble, but it will also reach it's limits at altitude if you are not careful.
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Hi all,
Nick said:"No pity here, Bell uses a different philosophy with everything, consistent with holding down the lower cost end of the market (that is not a slur, someone has to fill that market slice!)"
Well Bell is not THAT cheap anymore either:
Someone local just bought a 206BIII with some minimum equipment for US$1.2 M, delivered in 2008!!
You get THREE R-44-II models for that and fly 9pax to more altitude than the good old 206, NEVER worry about the TR, now you even can get a A/C, delivery in 4-5 month....
And no I am NOT a Robinson Dealer or get any credits from Frank!
I love EC though!
3top
Nick said:"No pity here, Bell uses a different philosophy with everything, consistent with holding down the lower cost end of the market (that is not a slur, someone has to fill that market slice!)"
Well Bell is not THAT cheap anymore either:
Someone local just bought a 206BIII with some minimum equipment for US$1.2 M, delivered in 2008!!
You get THREE R-44-II models for that and fly 9pax to more altitude than the good old 206, NEVER worry about the TR, now you even can get a A/C, delivery in 4-5 month....
And no I am NOT a Robinson Dealer or get any credits from Frank!
I love EC though!
3top
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BlenderPilot,
That is surely LTE, but one has to be mighty careful, because those Bell manuals have sneaky limits in them. Many models have a WAT curve for hover IGE and OGE that is considerably lighter than actual hover capability within engine limits.
In other words, the main rotor and engine can drive the small tail rotor out of poop, and the hover charts are not actually limited by lift, they are limited by tail rotor authority!
I call this sneaky because we are usually taught to believe that the engine and rotor set our hover limits. I have a full set of 212, 412 and 430 charts that show the hover capability as limited by tail rotor and not power/rotor!
It would be nice if you checked the hover condition you experienced (weight, alt and temp) against the performance charts to see if you were above the chart, yet within engine limits. This would tell us that the chart is a back door way to make it LTA (your fault) rather than LTE (aircraft's fault). Can you check?
That is surely LTE, but one has to be mighty careful, because those Bell manuals have sneaky limits in them. Many models have a WAT curve for hover IGE and OGE that is considerably lighter than actual hover capability within engine limits.
In other words, the main rotor and engine can drive the small tail rotor out of poop, and the hover charts are not actually limited by lift, they are limited by tail rotor authority!
I call this sneaky because we are usually taught to believe that the engine and rotor set our hover limits. I have a full set of 212, 412 and 430 charts that show the hover capability as limited by tail rotor and not power/rotor!
It would be nice if you checked the hover condition you experienced (weight, alt and temp) against the performance charts to see if you were above the chart, yet within engine limits. This would tell us that the chart is a back door way to make it LTA (your fault) rather than LTE (aircraft's fault). Can you check?
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In Bell's defence (or is it defense???) - the Bell 430 had suffienct tail rotor authority at the worst condition of wind at maximum weight at 7,000' Density altitude. (I did some flight testing with them when I was at Transport Canada).
And there is limit to what you can do with the tail rotor - put in such a big tail rotor that it really eats into payload.
There is, for example, no requirement in the regulations to be able to maintain heading while climbing vertically at maximum torque - should this be a requirement? Or should it be to maintain heading with winds up to 30 knots? or 20 mph as it currently is?
and Nick - I think you'd be surprised how many helicopter pilots never look at performance charts!
And there is limit to what you can do with the tail rotor - put in such a big tail rotor that it really eats into payload.
There is, for example, no requirement in the regulations to be able to maintain heading while climbing vertically at maximum torque - should this be a requirement? Or should it be to maintain heading with winds up to 30 knots? or 20 mph as it currently is?
and Nick - I think you'd be surprised how many helicopter pilots never look at performance charts!