Helicopter Aeros & Display Flying
Why can't a helicopter loop? Certainly it's been done by helicopters with just about every head design extant. Back in the 1970's a chap named Mike Meager was a demo pilot for Enstrom and he used to loop the ship in his displays. (He used to do backwards touchdown autos too, which tells you something about his mental state.)
There are anecdotal stories galore of various military Bell 47's looping - albeit unintentionally. My father went through Navy flight school in the mid-1950's. He tells of looking up one day and seeing one of his squadron HTL's upside down. He thought he was witnessing a fatal crash, but the pilots pulled it out.
A friend of mine who began flying 206's when they first came out admits that he buzzed a friend's house. Being a lot faster than the 47 he had been flying, when he hauled back on the stick the nose went up past vertical. So he says he just kept pulling and it went over into a loop. B*llocks? This old guy was never known to exaggerate and he told the story very matter-of-factly and contritely, not in a bragging way.
Ray Prouty writes about the incredible power that the cyclic has in pitch, and how that power is not dependent on airspeed the way the elevator of a fixed-wing is. The problem of course is "keeping it positive." As long as you maintain a positive-G all through the maneuvre it should work fine. And a properly performed loop should not have any parts where you endure negative-G.
But there are other problems. In a 206, I'd worry about pulling the transmission deck fittings clean out of their mounts. I'd worry about clipping the tailboom upon entry. And of course I'd worry about the engine quitting right at the top of the loop. (Would you lower the collective? Raise it? Would it matter?) But an H-500? Man, I'd loop that baby all day long.
So......can a helicopter do a loop? Sure! Just as a hang-glider *could.* But would you want to? Errr, maybe not. It depends on a LOT of things.
There are anecdotal stories galore of various military Bell 47's looping - albeit unintentionally. My father went through Navy flight school in the mid-1950's. He tells of looking up one day and seeing one of his squadron HTL's upside down. He thought he was witnessing a fatal crash, but the pilots pulled it out.
A friend of mine who began flying 206's when they first came out admits that he buzzed a friend's house. Being a lot faster than the 47 he had been flying, when he hauled back on the stick the nose went up past vertical. So he says he just kept pulling and it went over into a loop. B*llocks? This old guy was never known to exaggerate and he told the story very matter-of-factly and contritely, not in a bragging way.
Ray Prouty writes about the incredible power that the cyclic has in pitch, and how that power is not dependent on airspeed the way the elevator of a fixed-wing is. The problem of course is "keeping it positive." As long as you maintain a positive-G all through the maneuvre it should work fine. And a properly performed loop should not have any parts where you endure negative-G.
But there are other problems. In a 206, I'd worry about pulling the transmission deck fittings clean out of their mounts. I'd worry about clipping the tailboom upon entry. And of course I'd worry about the engine quitting right at the top of the loop. (Would you lower the collective? Raise it? Would it matter?) But an H-500? Man, I'd loop that baby all day long.
So......can a helicopter do a loop? Sure! Just as a hang-glider *could.* But would you want to? Errr, maybe not. It depends on a LOT of things.
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PPRUNE FAN#1
The S76 sim in West Palm Beach is great to play with. Until your half way around the roll. Then the lights all flash and the thing lurges and shakes as the the mild mouthed chap in the back shreeches something about his forced retirement plan , as we all sit there in the dark.
It was fun at the time.......
It was fun at the time.......
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UK Army display team 'The Blue Eagles' have loops as part of the display. Aircraft type is a Lynx.
There are various example pictures on their website. This one is quite nice.
Lynx looping
There is also some video footage here, although the quality is not brilliant. The Lynx does a couple of loops in the sequence. File size is 1.2Megs.
http://www.deltaweb.co.uk/eagles/fil...lsouthend01.rm
Edited as image was too big
There are various example pictures on their website. This one is quite nice.
Lynx looping
There is also some video footage here, although the quality is not brilliant. The Lynx does a couple of loops in the sequence. File size is 1.2Megs.
http://www.deltaweb.co.uk/eagles/fil...lsouthend01.rm
Edited as image was too big
Last edited by PPRuNe Radar; 13th Apr 2003 at 23:08.
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PPRUNE FAN#1
"But an H-500? Man, I'd loop that baby all day long."
The scene: tropical isle, full of well-heeled tourists, spending dotcom dollars on helicopter rides. Mate works for one company, D and E models.
Chief pilot regularly loops (empty) ship, "just to show everyone who's the boss".
Then they have trouble balancing the main rotor, not a simple thing on a D anyway, but now it seems like nothing's working right. Until...
They pull the rotor head off and find cracks in 5 out of 7 straps in the strap pack. Some all the way through. Big "GULP" from chief pilot.
The chief pilot now uses the sign on his desk to show who's the boss.
"But an H-500? Man, I'd loop that baby all day long."
The scene: tropical isle, full of well-heeled tourists, spending dotcom dollars on helicopter rides. Mate works for one company, D and E models.
Chief pilot regularly loops (empty) ship, "just to show everyone who's the boss".
Then they have trouble balancing the main rotor, not a simple thing on a D anyway, but now it seems like nothing's working right. Until...
They pull the rotor head off and find cracks in 5 out of 7 straps in the strap pack. Some all the way through. Big "GULP" from chief pilot.
The chief pilot now uses the sign on his desk to show who's the boss.
Is the Lynx as unreliable as it is accused? Seems story after story is reported where it is described as being the holder of the worst availibilty rate of any UK military aircraft. Any truth to those accounts? What say ye who are in the know?
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Thank you for some very cool stuff, The video was better quality than I expected. They really do loop those things around. Great pictures I saved the one of the upside down Lynx.
Ya know, now that I think about it, I think your torque wrench has to be a few clicks away from a correct setting to roll a helio. I mean I am amazed that a/c didn't just fall out of the sky.
Ya know, now that I think about it, I think your torque wrench has to be a few clicks away from a correct setting to roll a helio. I mean I am amazed that a/c didn't just fall out of the sky.
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I really don't advise loops on any helicopter. The guys who do them regularly probably have the mechanics take the helicopter apart and inspect everything very carefully after a couple of those.
Buitenzorg
Strap packs on 500's break for many different reasons, also you are allowed to fly with a certain # of straps (can't remember how many) as long as they are not too many on the same side, and you don't need to pull the rotor head to find them you can almost see them from the ground.
I have only seen one helicopter loop and that was the MD900 Explorer, and they looked more like vertical ovals, the demo pilot did several here in the AeroExpo, and I was amazed at how slow he would do the whole thing, maybe started with about 50 kts, and finished the same.
I've seen video of a military S76 do a roll from level flight but the tail went all over the place and it looked sloppy not like airplanes.
Once to avoid a collision with another helicopter I pulled so hard on the cyclic of a 206, the aircraft went a little past vertical and slightly turning to the left fortunately I was going about 100 kts, and when the 206 was past vertical it must still have had about 70 kts. and I just kept back pressure until it first went slightly inverted pointing straight down and back to level waay past VNE, my passenger described the manuver as one of those little ribbons people pin on themselves to show solidarity for something. I had made a very odd 270 degree turn to the right. This happened out of pure stupidity and I wouldn't want it to happen again, I consider myself lucky and reborn after that.
Buitenzorg
Strap packs on 500's break for many different reasons, also you are allowed to fly with a certain # of straps (can't remember how many) as long as they are not too many on the same side, and you don't need to pull the rotor head to find them you can almost see them from the ground.
I have only seen one helicopter loop and that was the MD900 Explorer, and they looked more like vertical ovals, the demo pilot did several here in the AeroExpo, and I was amazed at how slow he would do the whole thing, maybe started with about 50 kts, and finished the same.
I've seen video of a military S76 do a roll from level flight but the tail went all over the place and it looked sloppy not like airplanes.
Once to avoid a collision with another helicopter I pulled so hard on the cyclic of a 206, the aircraft went a little past vertical and slightly turning to the left fortunately I was going about 100 kts, and when the 206 was past vertical it must still have had about 70 kts. and I just kept back pressure until it first went slightly inverted pointing straight down and back to level waay past VNE, my passenger described the manuver as one of those little ribbons people pin on themselves to show solidarity for something. I had made a very odd 270 degree turn to the right. This happened out of pure stupidity and I wouldn't want it to happen again, I consider myself lucky and reborn after that.
Last edited by BlenderPilot; 15th Apr 2003 at 10:50.
Unless they've changed the display routine, the Lynx doesn't loop during the Blue Eagles display. What it does is a backflip. The pilot pulls up into a high hover, then pulls the cyclic smartly to the rear and the aircraft just flips over backwards, possible due to the semi rigid head design. 
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The Lynx currently doesn't feature in the Blue Eagles team due to operational commitments, however, in the last season when it appeared (2001 season) the routine included 2 loops and a backflip.
You can read reports on their official website.
http://www.deltaweb.co.uk/eagles/
You can read reports on their official website.
http://www.deltaweb.co.uk/eagles/
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What MightyGem describes is the principle of the 'Flip' first performed by my friend Graham Waddington when he was the AAC Lynx display pilot.
This is how Graham described the manoeuvre to me:
Later in the season Graham practised with the then new Mark 7. With it's enhanced tail rotor authority, he was able to complete a 180 degree turn whilst upside down!
As the Mark 7 was new on the scene and in short supply, he never publicly displayed the 'Waddington Flip with 180 twist'.
The Lynx was able to do a normal loop, but as they only displayed with the Tow missile system fitted which caused a considerable drag, a lot of airspeed was lost during the inverted portion so that the aircraft had a tendency to fall out of the air!
Still recoverable but "not a nice polished performance".
Makes my gentle manoeuvres in the Gazelle seem a little wimpish.
This is how Graham described the manoeuvre to me:
The manoeuvre starts with a vertical climb using the Lynx's speed - care needed not to exceed 'G' limits on initial pull-up. As the airspeed decreases to zero, the aircraft is levelled maintaining high power.
Once stable in level attitude, but with a vertical climb, the pilot smartly pulls back the cyclic to the stop, and lowers the collective lever slightly to contain Nr. The Lynx flips smartly onto its back.
As the nose passes through the vertical, a forward push on the cyclic is required to continue the descent for display purposes.
During the manoeuvre the only time the Lynx gets near to its limits is during the initial pull-up.
The manoeuvre was fist displayed during the 1988 Blue Eagles season using a Lynx AH1. Once stable in level attitude, but with a vertical climb, the pilot smartly pulls back the cyclic to the stop, and lowers the collective lever slightly to contain Nr. The Lynx flips smartly onto its back.
As the nose passes through the vertical, a forward push on the cyclic is required to continue the descent for display purposes.
During the manoeuvre the only time the Lynx gets near to its limits is during the initial pull-up.
Later in the season Graham practised with the then new Mark 7. With it's enhanced tail rotor authority, he was able to complete a 180 degree turn whilst upside down!
As the Mark 7 was new on the scene and in short supply, he never publicly displayed the 'Waddington Flip with 180 twist'.
The Lynx was able to do a normal loop, but as they only displayed with the Tow missile system fitted which caused a considerable drag, a lot of airspeed was lost during the inverted portion so that the aircraft had a tendency to fall out of the air!
Still recoverable but "not a nice polished performance".
Makes my gentle manoeuvres in the Gazelle seem a little wimpish.
Last edited by Flying Lawyer; 15th Apr 2003 at 07:37.
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MightyGen is right the Blue Eagled do not currently loop the Lynx in the display. The backflip he describes is correct and the aircraft only loses about 200 feet. As to looping and requiring extra maintenance its not true (i have both looped and barrel rolled the Lynx). A properly flown loop can be done at 1g and will not stress the aircraft in any way. The head type does not matter too much either..the Gazelle will happily barrel roll and loop (although you have to be careful not to chop the tail with too much rear cyclic). Even a teetering rotor head system will loop as long as positive 'g' is maintained throughout.
lynx-looping
CAC-R
To take you to task-how do you perform a normal loop at 1g?
It is impossible to do even in a fixed-wing a/c with a pwr/wt ratio of >1:1 ,so what is your secret?And ,are you not flying the a/c outside its Release-to- Service Document?Aerobatic manoeuvres not permitted?What are the "g" limits on your Lynx? Do you have an approved accelerometer fitted?
I presume you have seen the "Westlands" publicity film of a Lynx doing carefully monitored rolls and loops,to demonstrate it`s agility, but I doubt it was ever cleared for Service use.Unless you can quote-?
I will agree that the Gazelle is pretty nimble,and as /one of the original project t/p`s for in-Service testing have probably been to more corners of the envelope,all I would say-a la Hill-Street- is-"Let`s be careful out there,boys and girls"!!
Syc../
To take you to task-how do you perform a normal loop at 1g?
It is impossible to do even in a fixed-wing a/c with a pwr/wt ratio of >1:1 ,so what is your secret?And ,are you not flying the a/c outside its Release-to- Service Document?Aerobatic manoeuvres not permitted?What are the "g" limits on your Lynx? Do you have an approved accelerometer fitted?
I presume you have seen the "Westlands" publicity film of a Lynx doing carefully monitored rolls and loops,to demonstrate it`s agility, but I doubt it was ever cleared for Service use.Unless you can quote-?
I will agree that the Gazelle is pretty nimble,and as /one of the original project t/p`s for in-Service testing have probably been to more corners of the envelope,all I would say-a la Hill-Street- is-"Let`s be careful out there,boys and girls"!!
Syc../
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CAC-R
You talk about making loop as if it were the same as doing a practice auto, something relatively easy,
You stated:
"A properly flown loop can be done at 1g and will not stress the aircraft in any way. The head type does not matter too much either..the Gazelle will happily barrel roll and loop (although you have to be careful not to chop the tail with too much rear cyclic). Even a teetering rotor head system will loop as long as positive 'g' is maintained throughout."
In my very humble opinion the things you state on the above paragraph are misleading and largely incorrect.
Let me say I usually read a lot of things I usually don't agree with and let them go by, BUT in this case I am afraid some new guy or girl will read this and be mislead into thinking "its easy" and maybe go for it, so I feel it necessary to counterbalance your opinion.
So here,
I really doubt your average heli pilot could fly a "properly flown loop at 1 g", there are many reasons for this and I am sure some will be much better than me at explaining why this is very unlikely.
You said "The head type does not matter too much either" My humble opinion is that this is inaccurate, rotorhead type is what matters the most if you are going to attempt this, I am sure most sane pilots in this world wouldn't even consider performing a loop in an articulated or teetering head.
Then you state "even a teetering rotor head system will loop as long as positive 'g' is maintained throughout." do you have any idea how many things could go wrong here? My honest opinion is that if you get thru a loop in a teetering head heli, you got very lucky, and should consider yourself reborn.
I just really want to ask that when someone posts comments such as this, they do it responsibly, taking into account that the posters represent a small percentage of readers, there are a lot of new guys who only read this forum and rely on it for building their "descison making criteria"
Respectfully, BlenderPilot
LU-Z,
What Gunship was referring to in regards to "hydraulics, lead, lag" was probably the hydraulic dampers that control/restrict the lead lag in a lot of helicopters like the Agusta if I remember correctly.
You talk about making loop as if it were the same as doing a practice auto, something relatively easy,
You stated:
"A properly flown loop can be done at 1g and will not stress the aircraft in any way. The head type does not matter too much either..the Gazelle will happily barrel roll and loop (although you have to be careful not to chop the tail with too much rear cyclic). Even a teetering rotor head system will loop as long as positive 'g' is maintained throughout."
In my very humble opinion the things you state on the above paragraph are misleading and largely incorrect.
Let me say I usually read a lot of things I usually don't agree with and let them go by, BUT in this case I am afraid some new guy or girl will read this and be mislead into thinking "its easy" and maybe go for it, so I feel it necessary to counterbalance your opinion.
So here,
I really doubt your average heli pilot could fly a "properly flown loop at 1 g", there are many reasons for this and I am sure some will be much better than me at explaining why this is very unlikely.
You said "The head type does not matter too much either" My humble opinion is that this is inaccurate, rotorhead type is what matters the most if you are going to attempt this, I am sure most sane pilots in this world wouldn't even consider performing a loop in an articulated or teetering head.
Then you state "even a teetering rotor head system will loop as long as positive 'g' is maintained throughout." do you have any idea how many things could go wrong here? My honest opinion is that if you get thru a loop in a teetering head heli, you got very lucky, and should consider yourself reborn.
I just really want to ask that when someone posts comments such as this, they do it responsibly, taking into account that the posters represent a small percentage of readers, there are a lot of new guys who only read this forum and rely on it for building their "descison making criteria"
Respectfully, BlenderPilot
LU-Z,
What Gunship was referring to in regards to "hydraulics, lead, lag" was probably the hydraulic dampers that control/restrict the lead lag in a lot of helicopters like the Agusta if I remember correctly.
Last edited by BlenderPilot; 15th Apr 2003 at 12:31.
Slow roll????
To correct a previous person's post, that CH53 did a BARREL ROLL, with positive g all the way. A slow roll is impossible in a helicopter (models do them OK, though) because you can't get negative pitch in flight.
And I am sure I have read previously that helicopters such as the Bell 206 are certified to +2.7g. This allows you to perform a level steep turn at 60 degrees of bank, where you must pull 2g to hold height, and be able to survive some turbulence while doing the turn, without the Jesus Nut popping off.
If anybody can perform a loop without pulling 3g or more, I would like to see it. Even in a clean jet like a Macchi, with plenty of airspeed, a 3g pullup still resulted in such a speed loss that the loop was more egg-shaped and you could barely hold 1g over the top. Doing a loop in a teetering head is just practising bleeding. I have come very close to inadvertently barrel-rolling a 206, and almost intentionally did it in a BK117, but the pucker valve over-rode my intentions. But the BK's aero demonstration is special.
Anybody who has seen the NH90 demo will certainly be awed- most spectacular thing I have ever seen by a chopper.
And I am sure I have read previously that helicopters such as the Bell 206 are certified to +2.7g. This allows you to perform a level steep turn at 60 degrees of bank, where you must pull 2g to hold height, and be able to survive some turbulence while doing the turn, without the Jesus Nut popping off.
If anybody can perform a loop without pulling 3g or more, I would like to see it. Even in a clean jet like a Macchi, with plenty of airspeed, a 3g pullup still resulted in such a speed loss that the loop was more egg-shaped and you could barely hold 1g over the top. Doing a loop in a teetering head is just practising bleeding. I have come very close to inadvertently barrel-rolling a 206, and almost intentionally did it in a BK117, but the pucker valve over-rode my intentions. But the BK's aero demonstration is special.
Anybody who has seen the NH90 demo will certainly be awed- most spectacular thing I have ever seen by a chopper.
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I was fortunate enough to be in The Blue Eagles for a few years and have displayed the Lynx AH7 many times. Just for the record all of the manoeuvres flown were approved by the manufacturer and the MOD.
The last time I personally displayed it the more extreme parts were a loop which was entered at 120kts 600ft agl and completed purely in the pitch plane with no roll at all at the top of the loop. (That was Plan A anyway).
The backflip was flown from 600ft agl and was recoverable by 300ft agl quite easily.
The Eagle Roll was entered at 600ft 120kts and consisted of rolling the aircraft inverted and simultaneously turning through 270deg to the right.
The rearwards transition was flow at 60kts ending in a 90deg nose down attitude to fly away.
Other parts of the display include pedal turns which are broadly similar to a fixed wing hammerhead stall turn and wingovers which are almost identical to fixed wing wingovers.
By far the most difficult thing to do however was stopping the rotor blades at the same time as the Gazelles during the post display shutdown!
The short answer to your question is yes it can and has been done, the aircraft is not falling out of the loop, you are still definitely flying it. Incidentally the display aircraft were fitted with a G meter and all of the display was flown within the normal aircraft limitations. Flying this machine in the displays we did was without doubt tiring and demanding on the concentration front but also unquestionably the highlight of my flying career to date.
Hope this is of use to you. Feel free to e mail me if you would like further.
Thanks for your post and offer of further info.
Can I suggest questions/answers here on the forum instead of email so that we can all read and discuss.
Heliport
The last time I personally displayed it the more extreme parts were a loop which was entered at 120kts 600ft agl and completed purely in the pitch plane with no roll at all at the top of the loop. (That was Plan A anyway).
The backflip was flown from 600ft agl and was recoverable by 300ft agl quite easily.
The Eagle Roll was entered at 600ft 120kts and consisted of rolling the aircraft inverted and simultaneously turning through 270deg to the right.
The rearwards transition was flow at 60kts ending in a 90deg nose down attitude to fly away.
Other parts of the display include pedal turns which are broadly similar to a fixed wing hammerhead stall turn and wingovers which are almost identical to fixed wing wingovers.
By far the most difficult thing to do however was stopping the rotor blades at the same time as the Gazelles during the post display shutdown!
The short answer to your question is yes it can and has been done, the aircraft is not falling out of the loop, you are still definitely flying it. Incidentally the display aircraft were fitted with a G meter and all of the display was flown within the normal aircraft limitations. Flying this machine in the displays we did was without doubt tiring and demanding on the concentration front but also unquestionably the highlight of my flying career to date.
Hope this is of use to you. Feel free to e mail me if you would like further.
Thanks for your post and offer of further info.
Can I suggest questions/answers here on the forum instead of email so that we can all read and discuss.
Heliport
Last edited by Heliport; 15th Apr 2003 at 20:21.
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Helicopters that I know of that have done aerobatics include the Apache, the UH-60 (one famous shot of Nick upside down in a Turkish model shortly after the US Army declared the Blackhawk was not cleared for anything more than 60 degrees of bank), the Rooivalk, Bo-105, CH-53, S-67 (old Sikorsky prototype that unfortunately crashed at Farnborough), Gazelle, Lynx.
At the speeds most helicopters are capable of, aerobatic maneuvers will resemble those of Cessna 152 Aerobat or other underpowered light airplanes (i.e. not like a Pitts Special)
At the speeds most helicopters are capable of, aerobatic maneuvers will resemble those of Cessna 152 Aerobat or other underpowered light airplanes (i.e. not like a Pitts Special)