Can Helicopters fly inverted? (Merged threads)
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The issue is not the attitude of the aircraft, but rather its full maneuver state. You picture it upside down, and the rotors now having to lift upside down, but that is not what happens, in most cases.
In the loops and split S maneuvers we do, the aircraft is continuously developing some positive load factor with the rotor pulling it toward the earth, so that the pilot feels normal in his seat, and a glass of water on the dash would not spill. They can be done in most helos, but with tiny margins for error in many.
Two exceptions are the BO-105 and Comanche., Both have very controllable rotors, and can develop significant negative lift. In films, I have seen the BO pushed over to 135 degrees nose down and then just pulled back up to level. This surely created lots of negative G. These two helos come closest to your concept of true, trimmed upside down flight.
Of course, control is only part of the issue. Without inverted fuel and hydraulic systems, these helos would get very quiet after a few seconds upside down!
In the loops and split S maneuvers we do, the aircraft is continuously developing some positive load factor with the rotor pulling it toward the earth, so that the pilot feels normal in his seat, and a glass of water on the dash would not spill. They can be done in most helos, but with tiny margins for error in many.
Two exceptions are the BO-105 and Comanche., Both have very controllable rotors, and can develop significant negative lift. In films, I have seen the BO pushed over to 135 degrees nose down and then just pulled back up to level. This surely created lots of negative G. These two helos come closest to your concept of true, trimmed upside down flight.
Of course, control is only part of the issue. Without inverted fuel and hydraulic systems, these helos would get very quiet after a few seconds upside down!
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Seem to remember a few years back seeing a video clip of good ol' Charlie Zimmerman holding an inverted hover in a BO 105 for at least 7 or 8 seconds which would indicate a certain degree of control in my book. That said.....what he couldn't do with that aircraft probably wasn't worth talking about.
Gather he was stopped from displaying !!!!! Bloody good pilot but must've been as mad as a fish to pull off some of those manoeuvres.
P.S. As an ex display pilot I have looped a helicopter ( properly )several times. ( Not a 105 ) and would tend to agree with Slartibardfast that once you've plucked up the b***s, commited yourself and adopted the necessary attitude the aircraft will invariably fly itself around.
Seem to remember a few years back seeing a video clip of good ol' Charlie Zimmerman holding an inverted hover in a BO 105 for at least 7 or 8 seconds which would indicate a certain degree of control in my book. That said.....what he couldn't do with that aircraft probably wasn't worth talking about.
Gather he was stopped from displaying !!!!! Bloody good pilot but must've been as mad as a fish to pull off some of those manoeuvres.
P.S. As an ex display pilot I have looped a helicopter ( properly )several times. ( Not a 105 ) and would tend to agree with Slartibardfast that once you've plucked up the b***s, commited yourself and adopted the necessary attitude the aircraft will invariably fly itself around.
One of the first things i could see from the pilot seat in a BO-105 was a 110 degrees dive to demonstrate the possibilities of my favourite ship up to date. I will never forget the first look at the Attitude indicator going into the deep, deep, deep brown... " (really i looked at the instrument, why i couldn't believe the incredible dive angle) The instructor came calm with the words "... look to the mast bending moment, allways stay in the green.... " 
I will admit now, i was shocked!!! I had flown up to this point some really different types of helicopters but it wasn't to imagine what the small beast could do! Ok, some 100 hp and a little bit more cabin room needs the "pilotship", but thats impossible due to some constructional and CG problems.
The hydraulics and the fuel system are able to work proper on negative Gs. They are full pressurized and closed.
Aerobatics are prohibited due to some simple reasons.
1. Most pilots are not aerobatic experienced. That could easy kill you! The green area is small on some situations. In the described dive you have only round about 6-8 sec from a IAS 0kt to bring the ship back to level or you will exceed the VNE with all the problems in aerodynamic and solidity.
2. The a/c will be overstressed, especially with the rigid rotor. Such a rotor brings the stress and vibrations direct to the fuselage with a lot of cracks as the result .
3. You lost all your insurance and may be your job.
4. The a/c is not certified for such "flights".
Thats the reason why EC pilots will today never show (such) aerobatics on official dates. The German Army shows sometimes such procedures, but only very limited to special trained pilots and they have problems with the cracks and other damages. No civil operator will pay such bills.
I will admit now, i was shocked!!! I had flown up to this point some really different types of helicopters but it wasn't to imagine what the small beast could do! Ok, some 100 hp and a little bit more cabin room needs the "pilotship", but thats impossible due to some constructional and CG problems.
The hydraulics and the fuel system are able to work proper on negative Gs. They are full pressurized and closed.
Aerobatics are prohibited due to some simple reasons.
1. Most pilots are not aerobatic experienced. That could easy kill you! The green area is small on some situations. In the described dive you have only round about 6-8 sec from a IAS 0kt to bring the ship back to level or you will exceed the VNE with all the problems in aerodynamic and solidity.
2. The a/c will be overstressed, especially with the rigid rotor. Such a rotor brings the stress and vibrations direct to the fuselage with a lot of cracks as the result .
3. You lost all your insurance and may be your job.
4. The a/c is not certified for such "flights".
Thats the reason why EC pilots will today never show (such) aerobatics on official dates. The German Army shows sometimes such procedures, but only very limited to special trained pilots and they have problems with the cracks and other damages. No civil operator will pay such bills.
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Inverted flight
Can anyone tell me why some helicopters are capable of inverted flight (apache, lynx, bk117?) and others are not. My guess is a teetering head would be susceptible to mast bumping (lowG) but, apart from acrobatics prohibited and carburetor problems is there more involved? And can it be sustained or is it short lived.
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The concept of hinge offset is worth exploring for the real answer here. If the rotor has the ability to develop control at zero g, it has high hinge offset, and can be maneuvered more. Teetering rotors are the worst kind for maneuvering, for that reason, as they have zero hinge offset.
See this discussion, with a good illustration half way down:
http://www.w3mh.co.uk/articles/html/csm9-11.htm
See this discussion, with a good illustration half way down:
http://www.w3mh.co.uk/articles/html/csm9-11.htm
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Avoid imitations
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There is a site showing a model heli landing on the ceiling amongst other amazing stunt flying. Look on Google for "rc helicopter videos" and take a look at the Helihobby.com site.
Last edited by ShyTorque; 2nd Jun 2005 at 17:23.
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Thanx for your replys guys, liked the vid glyn thrash & yes like that!
If teetering rotors are the worst for manouvering then is a rigid system the best?What about fully articulated systems.
None of my texts cover this subject.Does anyone know of texts that cover inverted flight in choppers?
If teetering rotors are the worst for manouvering then is a rigid system the best?What about fully articulated systems.
None of my texts cover this subject.Does anyone know of texts that cover inverted flight in choppers?
why some helicopters are capable of inverted flight
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The thread I made a while ago had some great upside down replies and Silsoe Sid abusing public property !! ( lol )
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TFS
CLICK HERE
TFS
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here is link to accident report guy went inverted in 222 and lived to tell the tale
http://www.ntsb.gov/ntsb/brief.asp?e...12X20769&key=1
THere should also be a factual report but my pdf reader is acting up. excerpt from factual report
"... severe nose high climb attitude. The cyclic stick harded over to the full aft position. I
was unable to move any of the flight controls except the pedals. The aircraft continued over, now
upside down and diving towards the ground, still at cruise power. Unable to move the cyclic, the
aircraft continued this inside loop type of attitude and started up again. Until this point I
believe I was trying to manipulate the flight controls normally with one hand on the collective,
and my right on the cyclic. I was not strong enough so I tried moving the cyclic with both hands.
As about this the cyclic started moving on it's own, and the fight now was trying to keep the
controls centered. The aircraft was completely out of control with me having minimal impact on
adjusting the flight controls."
"I either told the paramedic or he on his own initiative lowered the collective using both hands.
The aircraft then was diving at the ground and it seemed like I was more able to keep it somewhat
in a level attitude. I flared with cyclic to arrest the rate of decent and then we ballooned up in
pitch. I was trying to place the aircraft in a parking lot when we did this pitch-up. As we
climbed up again I saw power lines to my front with a road beyond that had enough room to set the
aircraft down. As I tried to raise the collective to go over these wires, the rotor bled off with
the low rotor audio and lights. I realized the aircraft was not going to clear the wires, so I
jammed full left pedal and placed the helicopter on the roof of a two-story building immediately to
my left."
http://www.ntsb.gov/ntsb/brief.asp?e...12X20769&key=1
THere should also be a factual report but my pdf reader is acting up. excerpt from factual report
"... severe nose high climb attitude. The cyclic stick harded over to the full aft position. I
was unable to move any of the flight controls except the pedals. The aircraft continued over, now
upside down and diving towards the ground, still at cruise power. Unable to move the cyclic, the
aircraft continued this inside loop type of attitude and started up again. Until this point I
believe I was trying to manipulate the flight controls normally with one hand on the collective,
and my right on the cyclic. I was not strong enough so I tried moving the cyclic with both hands.
As about this the cyclic started moving on it's own, and the fight now was trying to keep the
controls centered. The aircraft was completely out of control with me having minimal impact on
adjusting the flight controls."
"I either told the paramedic or he on his own initiative lowered the collective using both hands.
The aircraft then was diving at the ground and it seemed like I was more able to keep it somewhat
in a level attitude. I flared with cyclic to arrest the rate of decent and then we ballooned up in
pitch. I was trying to place the aircraft in a parking lot when we did this pitch-up. As we
climbed up again I saw power lines to my front with a road beyond that had enough room to set the
aircraft down. As I tried to raise the collective to go over these wires, the rotor bled off with
the low rotor audio and lights. I realized the aircraft was not going to clear the wires, so I
jammed full left pedal and placed the helicopter on the roof of a two-story building immediately to
my left."
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inverted flight
RC models have no teetering hinge normally, so the head is rigid (hingeless) except for the blade attach bolt that also serves as a lead lag hinge. The collective pitch is set for several degrees of negative pitch in aerobatic models, this allows sustained inverted flight.
For a full size helo the collective lower stop is set near 0 degrees for autorotation. The 5 degrees or so of negative pitch required for sustained inverted flight would be a problem for the pilot in an autorotation emergency. Just one of the many problems to consider.
For a full size helo the collective lower stop is set near 0 degrees for autorotation. The 5 degrees or so of negative pitch required for sustained inverted flight would be a problem for the pilot in an autorotation emergency. Just one of the many problems to consider.
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Thats answered some of my questions, I didn't realise that thread was there TFS, thanks.
Great pics of gazelle & aussie squirrell
A must see is Discovery Channel Extreme Choppers on DVD,with umpteen barrel rolls in a lynx.
Great pics of gazelle & aussie squirrell
A must see is Discovery Channel Extreme Choppers on DVD,with umpteen barrel rolls in a lynx.
Avoid imitations
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The Navy Lynx is capable of some negative pitch, I believe.
The Navy Lynx is capable of some negative pitch, I believe
Combine Operations
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Widgeon - that's the stuff of nightmares.
We used to operate BO105's, and I seem to remember we had one which had two degrees of negative pitch. It's a long time ago, and I've a memory like a whatsit, but there were certainly no special procedures for applying negative pitch.
My own experience of negative g, again in a BO105, was while enjoying a flight over the Western Isles. I flew into a terrific downdraught, and became aware of a sudden vast increase in pressure on the shoulder harness, my feet flying off the pedals, clouds of dust rising from the floor, oil pressure warning lights coming on, with the pressures indicating zero, and all the while the passenger pushing up on the cockpit roof as hard as he could, barely managing to suppress a scream.
It probably didn't last more than a second or so, but I'm sure it shortened my life by a few years. My thought at the time was, "Of all the helicopter types in the world, thank God I'm in a Boelkow."
We used to operate BO105's, and I seem to remember we had one which had two degrees of negative pitch. It's a long time ago, and I've a memory like a whatsit, but there were certainly no special procedures for applying negative pitch.
My own experience of negative g, again in a BO105, was while enjoying a flight over the Western Isles. I flew into a terrific downdraught, and became aware of a sudden vast increase in pressure on the shoulder harness, my feet flying off the pedals, clouds of dust rising from the floor, oil pressure warning lights coming on, with the pressures indicating zero, and all the while the passenger pushing up on the cockpit roof as hard as he could, barely managing to suppress a scream.
It probably didn't last more than a second or so, but I'm sure it shortened my life by a few years. My thought at the time was, "Of all the helicopter types in the world, thank God I'm in a Boelkow."
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"Boelkow Uber Alles!" .... even the birds are jealous!
gotta luv that "slippery lil sucker" ...
Ahhh "The earth above and the sky below" what! ......?????
gotta luv that "slippery lil sucker" ...
Ahhh "The earth above and the sky below" what! ......?????
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To those who fly in UK, we fly inverted all the time compared to those in Australia - and visa versa.
The question is worthy of technical debate but as often stressed - why would anyone wish to build a helicopter (mega, mega bucks) with an ability that would not be rational.
It's almost similar to asking why can't all boats be fitted with wheels so that they could operate on land. Or why can't all airplanes land on water and submerge.
The question is worthy of technical debate but as often stressed - why would anyone wish to build a helicopter (mega, mega bucks) with an ability that would not be rational.
It's almost similar to asking why can't all boats be fitted with wheels so that they could operate on land. Or why can't all airplanes land on water and submerge.