AS350 Astar / AS355 Twinstar [Archive Copy]
"Just a pilot"
Y'all, I've done 30k+ landings in this airframe, in calm to 50 knots, level ground to elevated (all varieties), and my observations-
1) Yes, it ordinarily lands right side skid heels first. If you put that down without translation and not descending too quickly, you won't know when it touches. Translate a little over the ground except forward and all bets are off. If I "feel" for that first touch, I always mess it up. Yes, the control trim positions change suddenly, but nothing unacceptable. If you have a stabilised and slow descent going, it'll be a quick small movement or two and the collective will be on the bottom.
So- eyes out front, hold it in place, and slow uniform descent until the collective stops going down. Just like any helicopter.
2) The aircraft will land fine, as above, unless winds anywhere but on the nose- Then it darts and jumps a bit more, especiialy sporty with 10-15 knots on the right rear quarter! If you're up to form, you can still do the "Technique 1)" but it's not easy. Don't feel for the ground!!!
10-15 knots at the right rear quarter can get real interesting, especially on an elevated pad with turbulence. Those conditions can bounce the automatic leveling device, a/k/a tail skid. It'll pitch up suddenly, commence a descent, and yaw suddenly.
A bunch of wind improves things (and stabilises the airflow, which I think supports my tail rotor wash theory), and it does better in all quads, as long wind steady state. Plenty tail rotor authority and few surprises.
3) If all else fails, a little forward as the right rear skid heel touches. Good when you absolutely gotta plant this pig as it's pointing, and "good basic helo technique" is kicking your keester today.
Whenever I lapse into the slide-it-on routinely, I'm soon back feeling for the ground and jarring teeth. 350's will show you where the pilot is wanting.
This aircraft is "precise" and little change in trim and effect is apparent in the seat of one's pants. More than once I've thought I was definitely down and bottomed the collective only to have it drop the last couple inches. "I" was "down and through flying" but the helo wasn't.
When all else fails- stop overcontrolling, hold it still- and land it like any helo. The slide on is admitting defeat and she knows she whipped you.
1) Yes, it ordinarily lands right side skid heels first. If you put that down without translation and not descending too quickly, you won't know when it touches. Translate a little over the ground except forward and all bets are off. If I "feel" for that first touch, I always mess it up. Yes, the control trim positions change suddenly, but nothing unacceptable. If you have a stabilised and slow descent going, it'll be a quick small movement or two and the collective will be on the bottom.
So- eyes out front, hold it in place, and slow uniform descent until the collective stops going down. Just like any helicopter.
2) The aircraft will land fine, as above, unless winds anywhere but on the nose- Then it darts and jumps a bit more, especiialy sporty with 10-15 knots on the right rear quarter! If you're up to form, you can still do the "Technique 1)" but it's not easy. Don't feel for the ground!!!
10-15 knots at the right rear quarter can get real interesting, especially on an elevated pad with turbulence. Those conditions can bounce the automatic leveling device, a/k/a tail skid. It'll pitch up suddenly, commence a descent, and yaw suddenly.
A bunch of wind improves things (and stabilises the airflow, which I think supports my tail rotor wash theory), and it does better in all quads, as long wind steady state. Plenty tail rotor authority and few surprises.
3) If all else fails, a little forward as the right rear skid heel touches. Good when you absolutely gotta plant this pig as it's pointing, and "good basic helo technique" is kicking your keester today.
Whenever I lapse into the slide-it-on routinely, I'm soon back feeling for the ground and jarring teeth. 350's will show you where the pilot is wanting.
This aircraft is "precise" and little change in trim and effect is apparent in the seat of one's pants. More than once I've thought I was definitely down and bottomed the collective only to have it drop the last couple inches. "I" was "down and through flying" but the helo wasn't.
When all else fails- stop overcontrolling, hold it still- and land it like any helo. The slide on is admitting defeat and she knows she whipped you.
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as355f1
It is an old belief that the height of the main rotor vs the height of the tail rotor is a reason for hovering one skid/wheel down, this is really not correct. All the forces developed by the machine are summed at the center of gravity, which is considerably below the main rotor head.
The aerodynamics of the machine make it such that the higher the tail rotor, the LESS it leans in a hover! Helos with the lowest tail rotors have the most lean, believe it or not.
High tail rotors produce a rolling moment that subtracts the left lean (for a US type system). For a given helo, if the tail rotor is centered on the tail cone, the left lean is about 5 to 6 degrees. If that tail rotor is moved up a few feet to the top of the tail, the lean is reduced to 3 degrees or so.
A question for the group:
In what axis does it wiggle - yaw or roll?
How fast are the wiggles _ in wiggles per second?
It is an old belief that the height of the main rotor vs the height of the tail rotor is a reason for hovering one skid/wheel down, this is really not correct. All the forces developed by the machine are summed at the center of gravity, which is considerably below the main rotor head.
The aerodynamics of the machine make it such that the higher the tail rotor, the LESS it leans in a hover! Helos with the lowest tail rotors have the most lean, believe it or not.
High tail rotors produce a rolling moment that subtracts the left lean (for a US type system). For a given helo, if the tail rotor is centered on the tail cone, the left lean is about 5 to 6 degrees. If that tail rotor is moved up a few feet to the top of the tail, the lean is reduced to 3 degrees or so.
A question for the group:
In what axis does it wiggle - yaw or roll?
How fast are the wiggles _ in wiggles per second?
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From my days flying the D model, lo these many years ago, ISTR that the answers are Yes and I can't count that fast. 
I always tried to keep my hands as still as possible and my feet moving as fast as possible - land the thing using the tail rotor instead of the main rotor for precise positioning. But nobody alive can set one down gracefully every time. Most of the time, but not every time; eventually it will embarrass you. I've never flown any flavor of B model, and never one with a high skid gear, so those may be different. If the fuel tanks are baffled now, that's a big improvement, but I only noticed that in cruise, the notorious AStar shuffle. When landing, I was always moving things faster than the fuel could move in the tank, so the inertia never seemed to build up.
I loved the space between the seat and the door. When I moved into the AStar from a 206, all that space was wonderful. I finally had a place to put my bag where the pax couldn't get it and take it downstairs with them. 140 gallons of fuel, speed to get somewhere before burning all of it, a heater, a defroster - hell, I was in paradise. A little twitchiness in landing was only a minor annoyance. The hand grenade LTS101 built by Lycoming was what worried me. Those who still use them say they're much improved now, but the offshore operators abandoned them long ago.
I always tried to keep my hands as still as possible and my feet moving as fast as possible - land the thing using the tail rotor instead of the main rotor for precise positioning. But nobody alive can set one down gracefully every time. Most of the time, but not every time; eventually it will embarrass you. I've never flown any flavor of B model, and never one with a high skid gear, so those may be different. If the fuel tanks are baffled now, that's a big improvement, but I only noticed that in cruise, the notorious AStar shuffle. When landing, I was always moving things faster than the fuel could move in the tank, so the inertia never seemed to build up.
I loved the space between the seat and the door. When I moved into the AStar from a 206, all that space was wonderful. I finally had a place to put my bag where the pax couldn't get it and take it downstairs with them. 140 gallons of fuel, speed to get somewhere before burning all of it, a heater, a defroster - hell, I was in paradise. A little twitchiness in landing was only a minor annoyance. The hand grenade LTS101 built by Lycoming was what worried me. Those who still use them say they're much improved now, but the offshore operators abandoned them long ago.
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Having flown over 3000 hours on AS 350/355 series and landed most any kind of place, I don´t dare to explain WHY is so hard to do a soft/Bell type of landing, mostly on hard surfaces, like concrete or others alike, but my two cents on HOW to deal with it are trown in:
It's a nice trick to land moving a bit forward as it is to put the wheight on the right aft skid and maintain it in that position until the bouncing stops, then really easy on the cyclic, put the rest of the right skid on the ground, maintain again without stirring the pot, and low collective to land the left skid. I find that if you want to land without feeling that frustating sensation of rebounding on the right skid first and then on the left, due to a really stiff landing gear (cross tube), you have to go through three fases:
1.- Right hand aft skid
2.- Right skid
3.- Left skid
If you don´t move the cyclic nothing more than strictly needed, you might get a soft landing out of every 10 tries.
Good luck
P.D. In the other hand there is no better landing gear to do toes or partial landing in stones and other weird places in mountain terrain IMHO.
Buen vuelo
It's a nice trick to land moving a bit forward as it is to put the wheight on the right aft skid and maintain it in that position until the bouncing stops, then really easy on the cyclic, put the rest of the right skid on the ground, maintain again without stirring the pot, and low collective to land the left skid. I find that if you want to land without feeling that frustating sensation of rebounding on the right skid first and then on the left, due to a really stiff landing gear (cross tube), you have to go through three fases:
1.- Right hand aft skid
2.- Right skid
3.- Left skid
If you don´t move the cyclic nothing more than strictly needed, you might get a soft landing out of every 10 tries.
Good luck
P.D. In the other hand there is no better landing gear to do toes or partial landing in stones and other weird places in mountain terrain IMHO.
Buen vuelo
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Agree totally with Devil & Matador...
Re: the ugly wind, yes, right quartering and/or straight up the tail upslope is very tough - mix in some down drafts from high surrounding trees and you have your hands full. The advantage with the Astar is you do have lots of range fore and aft cyclic, vs others where you have to be very careful not to run out of aft cyclic when facing a slope. I have had to hold it in a hover (against my wishes) when a precise landing plus or minus 8-12" fore and aft and left and right is required, until I have that moment of respite from the tailwind, then plant it on the log or log pad .
As far as moving the pedals, everyone has their own technique, but I try to move the pedals as little as possible - the tail rotor is so powerful (which is good), that even small movements of the pedals back and forth exaggerate the wiggle (at least I have found that).
Re: the ugly wind, yes, right quartering and/or straight up the tail upslope is very tough - mix in some down drafts from high surrounding trees and you have your hands full. The advantage with the Astar is you do have lots of range fore and aft cyclic, vs others where you have to be very careful not to run out of aft cyclic when facing a slope. I have had to hold it in a hover (against my wishes) when a precise landing plus or minus 8-12" fore and aft and left and right is required, until I have that moment of respite from the tailwind, then plant it on the log or log pad .
As far as moving the pedals, everyone has their own technique, but I try to move the pedals as little as possible - the tail rotor is so powerful (which is good), that even small movements of the pedals back and forth exaggerate the wiggle (at least I have found that).
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An interesting thread......
As a very! inexperienced pilot who has flown a number of different types I always found the Squirrel to be a fantastic aircraft.
I learnt to fly rotary in it and although it is a bit jumpy in the hover after some practice I never really noticed it.
As for the throttle I know other aircraft where the throttle is poorly placed for single pilot ops......i.e. Gazelle
Ralph
As a very! inexperienced pilot who has flown a number of different types I always found the Squirrel to be a fantastic aircraft.
I learnt to fly rotary in it and although it is a bit jumpy in the hover after some practice I never really noticed it.
As for the throttle I know other aircraft where the throttle is poorly placed for single pilot ops......i.e. Gazelle
Ralph
"Just a pilot"
Mr Lappos, I don't know why the question was framed as a "wiggle." That's a PIO, everytime, in these. 350's hover just fine, but as one descends and the flow changes, it'll pitch, roll and occasionally yaw, small but quick attitude changes, and start translating in response, if correction not expeditious and accurate. Controls are quick (the engineer type was right- "precise"), so small changes in position gotta have really fine control adjustments. That can be a challenge some days when the death-grip cramps are constantly being shaken out...
It's one of the few helos I've flown that seems as quick in the hover as in cruise. Real joy, harmonious and stable without being ponderous. If only the hydraulics were as nice...
It's one of the few helos I've flown that seems as quick in the hover as in cruise. Real joy, harmonious and stable without being ponderous. If only the hydraulics were as nice...
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Devil49,
Thanks for that info, it does seem to me the comments center around a yaw control that is both powerful and sensitive, and that we are talking about a bit of Pilot Induced Oscillation - PIO. Not much, I'll bet, and easily compensated for.
The reason why it gets worse as the aircraft descends is probably little to do with flow and such, and lots to do with the pilot getting tighter on the controls as the ground nears.
The reason why I asked about the frequency of the wiggle is that the airflow around the machine cannot generate a 2 or 3 Hz problem, because the aerodynamics are slower than that, but the pedals surely can. NOTARs are a bit slow on the yaw response, for example, and they captiolize on that aerodynamic force.
Generally the PIO can be fixed with a bit of damping on the pedals - like a door closer, a small hydraulic cylinder is imposed that makes the pedals hard to move too fast, but easy to move slowly.
Even a Huey is sensitive in the pedals, and likely to get a tad squirley when a pilot dances a bit too much on the pedals.
JNo,
Yes, I agree the right drift is exactly why the skid is low. The tail rotor is producing a force, (all US convention hereon) that pushes the helo to the right, a factor called "translating tendency". When the pilot corrects the right drift, he automatically rolls the aircraft a it to the left. When everything is settled, the roll attitude is about 2 to 3 degrees to the left, so the main rotor thrust is tilted a bit to the left to counter the tail rotor thrust to the right. 3 degrees tilt equals 5% of the main rotor thrust.
There is a hard to kill belief that the height of the tail rotor makes this worse, as if the comparison between the tail rotor hub and the main rotor hub height is somehow a part of the aerodynamics. Sadly, this one will not quite go away! Actually, the higher the tail rotor, the LESS the hover bank angle is!
Those who fly S-76 note about 2 to 3 degrees, those who fly a center line tail rotor (A-109 and any fenestron bird, for example) can you tell us what you see on the roll gyro when in a steady hover, no wind? I predict about 5 degrees or so. Comanche leaned at 5 degrees with its centerline fantail.
Thanks for that info, it does seem to me the comments center around a yaw control that is both powerful and sensitive, and that we are talking about a bit of Pilot Induced Oscillation - PIO. Not much, I'll bet, and easily compensated for.
The reason why it gets worse as the aircraft descends is probably little to do with flow and such, and lots to do with the pilot getting tighter on the controls as the ground nears.
The reason why I asked about the frequency of the wiggle is that the airflow around the machine cannot generate a 2 or 3 Hz problem, because the aerodynamics are slower than that, but the pedals surely can. NOTARs are a bit slow on the yaw response, for example, and they captiolize on that aerodynamic force.
Generally the PIO can be fixed with a bit of damping on the pedals - like a door closer, a small hydraulic cylinder is imposed that makes the pedals hard to move too fast, but easy to move slowly.
Even a Huey is sensitive in the pedals, and likely to get a tad squirley when a pilot dances a bit too much on the pedals.
JNo,
Yes, I agree the right drift is exactly why the skid is low. The tail rotor is producing a force, (all US convention hereon) that pushes the helo to the right, a factor called "translating tendency". When the pilot corrects the right drift, he automatically rolls the aircraft a it to the left. When everything is settled, the roll attitude is about 2 to 3 degrees to the left, so the main rotor thrust is tilted a bit to the left to counter the tail rotor thrust to the right. 3 degrees tilt equals 5% of the main rotor thrust.
There is a hard to kill belief that the height of the tail rotor makes this worse, as if the comparison between the tail rotor hub and the main rotor hub height is somehow a part of the aerodynamics. Sadly, this one will not quite go away! Actually, the higher the tail rotor, the LESS the hover bank angle is!
Those who fly S-76 note about 2 to 3 degrees, those who fly a center line tail rotor (A-109 and any fenestron bird, for example) can you tell us what you see on the roll gyro when in a steady hover, no wind? I predict about 5 degrees or so. Comanche leaned at 5 degrees with its centerline fantail.
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My thoughts are that all of you that experience this wiggle are ex Bell pilots.
I have never had the problem, nor have my students.
Around all helicopters close to the ground there will be patterns of air flow that are random due to a multiplicity of reasons. These air flow patterns will effect the tail and main rotors and as pilots you are trained and practiced in hovering. May I suggest more hovering practice with a relaxed and alert brain!
Coanda effects and the like are possible reasons. Some tail booms have strakes, some have had strakes and have had them removed, some do not have strakes. I think strakes were/are fitted for other reasons.
I have never had the problem, nor have my students.
Around all helicopters close to the ground there will be patterns of air flow that are random due to a multiplicity of reasons. These air flow patterns will effect the tail and main rotors and as pilots you are trained and practiced in hovering. May I suggest more hovering practice with a relaxed and alert brain!
Coanda effects and the like are possible reasons. Some tail booms have strakes, some have had strakes and have had them removed, some do not have strakes. I think strakes were/are fitted for other reasons.
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Head Turner:
There are lots of those who experience this who are not ex-Bell pilots.
Seems to be unique to the AS-350 series, although I have seen something similar, with less intensity in the Bell 407.
There are lots of those who experience this who are not ex-Bell pilots.
Seems to be unique to the AS-350 series, although I have seen something similar, with less intensity in the Bell 407.
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My company's looking at buying a Squirrel that comes with both high and low skids.
Planning to fly it in both configs and see but apart from the obvious change of ground clearance and dynamic rollover potential, what else is different when flying the low skid version ? Less 'wiggle' ?
Planning to fly it in both configs and see but apart from the obvious change of ground clearance and dynamic rollover potential, what else is different when flying the low skid version ? Less 'wiggle' ?
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All my time is in low skid models, and IME the low skid makes it harder to set one down gracefully. Also, the tail skid is below knee level when on the ground, and it is entirely possible to strike the ground with it when hovering with an aft CG and/or a tailwind. Avoid low skid gear at all costs.
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Is it nothing to do with the front and rear legs being a different length, and the bushy tail moving from side to side as they run???
Is there a difference between grey and red versions as well??
Is there a difference between grey and red versions as well??
Gentleman Aviator
Are there any helicopters where the main rotor head is at the same level as the tail rotor?
Certainly Brit military Principles of Flight teaching is thus: put simply, tail rotor roll (ie hovering left or right skid/wheel low, depending on main rotor direction of rotation) IS a consequence of the different height of main and tail rotors and is designed in to avoid being left (or right) side low in the cruise. As the fuselage pitches further down with increasing speed, at normal cruise, you have a (laterally) level floor. Much more comfortable, and less disorientating in IMC. However, inevitable design compromise means that laterally level fuselage in cruise (tail rotor and main rotor level) inevitably means in the hover when more nose up (tail rotor and main rotor NOT level), there is a lean to one side (towards the advancing main rotor blade).
Check out side on pictures of most conventional helos in the cruise to see that tail rotor is usually level with (or closer to) the main.
And I did say "put simply"!! With due consideration for Danny's bandwidth.
Steve,
Looked at many single-rotor Russian helicopters lately?
Maybe anti-clockwise is just the Americans being American...
Looked at many single-rotor Russian helicopters lately?
Maybe anti-clockwise is just the Americans being American...
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Jonathon Swift wrote a whole book about the ability to argue about arbitrary things!
As lately seen, Americans go Right when more power is added, the French and Russians have always gone Left!
As lately seen, Americans go Right when more power is added, the French and Russians have always gone Left!