Why can't real helicopters sustain inverted flight, like model ones?
Answers:
Cost is the only thing preventing it.
All you have to is design and certify a helicopter with a rigid head and enough negative pitch in the rotor. Then sell enough to recover the development costs.
Rotor airfoils are symetrical so they will produce the same lift upward as downward at similar angles of attack. Since the rotor would cone downwards, the tailboom would have to be clear of it. A rigid head would prevent the fuselage from flopping abound. The tail rotor would need no modification since torque direction is the same. Put in inverted fuel and oil systems and you're all set.
BTW, most helicopters have hinge stops to prevent the rotor from contacting the tail boom, but these aren't designed for flight loads.
And the Jesus nut wouldn't be supporting the weight of the helicopter, the mast would be in compression load. Just like propellers I work on that can go in forward or reverse with 4000SHP on the Hercules.
Ive been in helicopters many times.. over 20.. and im only 14.. ahaa.. im just to tired to read all that sh** you wrote.. ahaa
Well, you answered a few yourself, already. Also, the weight of the helicopter would also kill its lift, let alone, there is no way to reverse the rotor blades to sustain lift inverted. then there is the fuel problem too. No fuel can get to the engine(s). Also it probably require lots of forward momentum to be able to try and do a roll thus losing altitude.
Mass to Weight ratio + Lifting Force is why. Weigh a Model Helicopter, then get the weight of an Apache and do some math. The Model is about 1/2 if not more than actual weight of an Apache. If the Model weighs 5lb with gas, pilot ,toy pilot, but its weight. Then find the weight of an Apache, or a Cobra. We are talking Tons vs lbs here, so is alotta math. If the model is 1/4 scale, fully fueled,with added pilot, see how long it can sustain Inverted flight, then do that math with all those figures.
11,340lbs * 1/4, awe hec, Ill do it,1/4 of 11,340, (empty weight), 11k*25=454.4
Now if the model weighs 454 lbs, that's a big model! But you can see the Prop Area,Torque and Lift that is lost.
Plus the fact that it would take a whole buncha money and a great team of Mechanichs to retrofit the Jesus Nut and Rotor Pitch assemblies so that they could sustain lift while inverted.
Its basically a bad idea, because of the Helicopters natural design it is supposed to and it works in level and pitched attitude flight.
It would be cool at airshows and stuff, but would be a mechanicall nightmare.
Helicopter were never designed to fly upside down, it's that simple.
I was a mechanic on a BO-105 for about 13yrs and I have been inverted in one momentarily. And there's some german pilot that will make you stomach hurt just watching him go inverted
I am a helicopter pilot and have wondered this myself. It amazes me that model helicopters can do it, I couldn't believe it the first time I saw it.. very impressive!
There are a number of mechanical reasons for why production helicopters can't do it: the main rotor blades will not pitch negatively; any oils used in a sump-type system such as engine oil and gearbox oil would run down (up) and no longer lubricate whatever component it is supposed to; the main rotor gearbox is probably not built to hold the helicopter in that manner; and the helicopter body hangs from the main rotor like a pendulum and if you flipped it over the body would just flop to one side and either contact the blades or just turn the helicopter over again. The swashplate (the system that tilts the main rotor disc) would have to be built strong enough to stabilize the helicopter body in place over the main rotor.
Theoritically it might be possible to build a helicopter capable of this, but it might not be possible to make certain components strong enough without exeeding the weight limitations. The problem is that size and weight make a huge difference, a grasshoper can jump many times it's own body length, a human can't because the strength required increases exponentially with weight.
And considering the obstacles they would have to overcome there is no reason for a company to produce a helicopter capable of flying upside down because it serves no practical purpose. Also a pilot would have to try it, and I can tell you that that would be suicide.
There have been Rotorcraft from NASA in the past that CAN sustain inverted flight. Any Semi-Rigid or Rigid rotor system can loop, roll or split-s. As some have already answered the average Helicopter is not made for arobatics and does not have the necessary tools for such manuvers. Under FAA part 91 they don't even have guidlines but go out and loop a 500E and they'll slap you funny.
why do you worry about that sort of thing generally helicopters are for flying up the right way not inverted but if you look at the weight difference between a real one and a model you should be able to figure it out but also if you turn the helicopter upright the blades are designed so that the wind goes under the blades faster than over the blades thus creating lift and if inverted the difference in windspeed is reversed thus allowing the helicopter to cash downwards
The lift are on the blades not the helicopter. If the chopper was rigged for inverted flight (meaning the blades were far enough away to prevent damage, the engine were still able to receive oil correctly and the mast strong enough to stand the pressure) then it would be able to fly inverted but according to math the helicopter like the bumble bee is not supposed to fly any way. So there is no mathmatical answer to the question.
Some very fancy descriptions of why not. But all of them miss the truth.
It's only the noise and vibration that keeps a helicopter in the air!
Turn it upside down and it all goes quiet.
as a helicopter pilot the simple answer is this the enginering on a helicopter ie the stop when the collective is down will not go in to negative blade pitch which would be required to produce lift in inverted flight, to build an aircraft which would do this would be highly dangerous, if the pilot closed the lever on the decent for example and went to far you would un load the disc, and the aircraft would literally fall out of the sky. the only emergency procedure a helicopter has is an autorotaion, which requires the wind to come through the blades to provide lift in the event of an engine failure you only have 2 second to enter this state before your loss of spin in the rotors would become fatal, ie unloading of the disc.
if the collective was configured to function in the manner for it would be dangerous because the only procedure for getting to the ground would be removed.
Helicopters by there very nature are not designed to be acrobatic aircraft they are functional and practical. They are capable so some fantastic flying feats but if you want excitement go see the red arrows.
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