Clear up an argument. My mate says a helicopter can "loop the loop" I say this is mechanically impossible

Question

Who is rite and has any idiot ever tried it an lived?
It is physically NOT possible for a helicopter to fly upside down and "loop the loop" - Am i right?

Answer 1

The British Lynx Helicopter can. The rotors are designed to invert as it goes oven 90 degrees in order to allow for air flow to always push towards the ground. This was developed about 7 years ago, I don't know if any more have been designed to do it since mind.

Answer 2

A "loop the loop", even though I have never seen one done by helicopter, could be possible with enough speed and altitude, by one such as an Apache, or similar helicopter. I have seen videos of Apaches and others doing barrel rolls, rolling the aircraft left or right 360 degrees. RC helicopters can hover upside down because the rotor blades pitch both directions. "Real" helicopters can not, their pitch is from flat pitch and up, no down. If they did, the blades would easily cone enough to hit the aircraft. Which some will flex enough during EXTREME conditions to do this from flat pitch. Sustained forward flight is not possible inverted. Aerobatic maneuvers like this, if possible on the type of aircraft, could easily overstress the airframe and overtorque the engines. No helicopters have "boosters" to help do this stuff, and "jet" helicopters as someone called them, are simply ones with a turboshaft engine, which is 90% of all helicopters, the engines dont produce thrust, just horsepower, and lots of it to turn the rotor. All the time I spent in the military, I don't think I ever knew of a pilot that would attempt something like this with passengers on board. They would not be a pilot much longer. Never even heard of a UH-60 mechanic say one could do it, but it may be possible. More or less this stuff is limited to modern military ATTACK helicopters, most civillian and cargo birds either wouldnt have the power or airframe strength to do it. I think you are both right and wrong, just depends on the aircraft. And yes they live through it because the pilots that are allowed to do it are usually factory trained test pilots.

Answer 3

The blades of a helicopter are really rotary wings. Like any other wing, the pitch can be varied from maximum lift to none at all. When an aerobatic airplane is upside down the wings are also trying to push it to the ground but the pilot counter-acts that through the pitch of the wings, same with a helicopter. It is rare but some high performance helicopters can definitely do loops. You need plenty of altitude but it can be done.

Answer 4

I am afraid your mate is quite right helicopters can loop the loop. I have seen it done on several occasions once at an airshow the other at sea when a British navy Lynx looped his helo they sure do like to show off. The rotors of a helo are like the props on a plane the pitch can be changed so that the thrust is reversed same with the rotor change the pitch and instead of thrusting down it's now thrusting up.

Answer 5

It can be done, there have been several demonstrations of this at air shows over the years, the difficult part is getting enough speed up to carry the helicopter through the apex of the loop, so only military copters can do it, and they are only completely upside down for a fraction of a second, so you are partially right helicopters can't fly upside down since the thrust from their blades would drive them towards the ground.

Answer 6

Quite a number of the newer machines can do loops. There is a video somewhere on the internet of a Bell 407 doing an aileron roll, and the Blackhawk will loop, as will a Hughes 500.
The critical factor is a rigid or similar rotor head.

I've heard an Astar will loop, but I've never quite done a true loop in one. Come close though.

Answer 7

There are 3 basic types of Helicopter rotor head.
1/ Semi rigid, used for twin blade helos such as the ubiqutous Bell Jet Ranger.
2/ Fully articulated, used on big helos such as Sea Kings and Coast Guard SAR helos.
3/ Rigid Rotor. This is where the rotor blade roots do not have hinges but rely on the metal of the root to flex and take the strains of powered flight. These ones can loop the loop and include Westland Lynx and Apache Longbow.
Your friend is right, if you have money on this, put your hand in your pocket.

Answer 8

can helicopters fly upside down?

"...this is an experiment that few helicopter pilots ever want to try out....
for most, it is the fastest route to the ground, and not in a good way, although it is possible....

wings are designed so that air passing over the top surface, when the plane is flying normally, pulls them up...
that means they should be sucked down to the ground faster than you can say 'drop like a stone' when they go upside down. ..

what really happens when pilots are doing aerobatics
is that they effectively change the shape of the wings
using the flaps at the back
and angle at which the wings meet the air,
which gives them back some lift....

...helicopter pilots can also change the angle of attack...but, one of the biggest problems for helicopters when it comes to flying upside down is that the rotors have hinges...
this makes them easier to control when they are the right way up...turn them upside down, and the rotors smack into the tail.... which is not good...

...helicopters with rigid blades have been designed, and could fly upside down but have, so far, been too troublesome to make reliable...

...but you will see model helicopters fly upside down as they can now make use of strong carbon-fibre rotors..."
http://www.flipside.org.uk/say/lowdown/


best answer to your question
from other asker...
http://answers.yahoo.com/question/index?qid=20060918035746AAID3HG

Answer 9

Certain helicopters can pull it off. http://www.youtube.com/watch?v=VZlqfYLFR-4
http://www.youtube.com/watch?v=LGSq2OwL4ks
and here is a RC chopper pulling it off
http://www.youtube.com/watch?v=V4eYXYTEG-I
http://www.youtube.com/watch?v=GFOZZLRTaYc&mode=related&search=
So yes it is mechanically possible to fly a helicopter upside down, The RC chopper works exactly the same as the fullsize, But I would imagine a full size helicopter is unable to due to this because of the stresses involved or the pilots dont feel like dying.

If the engine fails on a helicopter, the blades will autorotate, (think of a maple tree seed as it falls to the ground) meaning the air moving up through them will move the blades slowing the aircrafts descent, this would mean that the blades have to be able to have negative pitch.

And its not just new helicopters than can loop, look at the first video, thats way back.

Answer 10

Your mate is right many makes of helicopter can loop the loop