Why can't a helicopter fly at an altitude of say 50,000 feet?

Answer 1

It is all about the airfoil (wing, fixed or rotorary), and the weight it is lifting.
When an airfoil moves through air (gasses) its design changes the pressures of the ambient gasses that surround the surface, lowering the pressure over the top of the the foil and increasing the pressure of the gasses below it (opposite for the horizontal stabalizers on fixed wing aircraft). This is the concept of lift, high pressure seeks lower pressure so atmosphere reaches equalibolium. Higher pressure under the wings or rotors push the machine towards the lower pressure atmosphere.
The greater the surface of the airfoil (and even its thickness as well as its root The problem with rotarary wing aircraft (helicopters) is their airfoils by inherient design are not as beefy (to speak of) as fixed wing and therefor don't produce the amount of lift as the larger airfoils found on fixed wing. Also because they are constantly in motion (resulting in higher airspeeds with the foil through the atmosphere) the airfoil needs to be more aerodynamicaly effecient, this reduces the thickness (top surface to bottom surface) of the foil, reducing total amount of lift it can produce, reducing the amount of payload it can lift and the maximum celling it can fly at. On some rotary aircraft this design flaw is counter by increasing the number of blades on the rotor and the length of the blades roots (leading edge to trailing edge).

Answer 2

There are a couple of good reasons why helicopters have a limited maximum altitude. First as the altitude increases so the air density drops, most gas turbine engines do not perform well at higher altitudes. These is normally not a problem for planes as they travel at higher speeds and there for have a higher inlet velocity than a helicopter engine.
If there was a way to over come this problem you would still have a major issue with the helicopters rotor. Because all of the lift comes from the rotor blades the lower the air density is the lower the level of lift they provide.
Developments were made in the 1970's to use rocket powered helicopters that had the rocket fixed to the end of the rotor blades. This allowed the tip speed to increase to make up for the loss in air density and lift.
However it was found that huge strains were placed on the rotor blades resulting in premature failures.

Answer 3

At 50,000ft the air is too thin for the rotor blades to produce enough lift for a helicopter to maintain flight. Helicopters are not pressurized so in order to fly at 50,000ft a pilot would have to wear a pressurized flight suite along with equipment on board to keep the suite pressurized. The weight of all that equipment would make the helicopter too heavy to fly to higher altitudes

Answer 4

Most of the replies are correct in saying that air density is a factor. however, most of them are comparing airplanes to helicopters and this is like the old cliche' of apples and oranges. A manufacturer could, without problem, design a helicopter to sustain flight at that altitude, but why would they.

The helicopter is doing pretty much what it is designed for, low level and slow flight. Most of the missions are SAR or landing in remote and confined locations. There are probably not many reasons to fly at that altitude.

Answer 5

Helos fly because the rotors act as wings. Notice how much thicker airplane wings are in comparison to helo blades?

The wings are much larger and thus allow planes at higher altitudes than helos

Answer 6

Helicopter rotor blades don't have enough wing area for the thin air at high altitudes.

Answer 7

Rotary wing air craft need air under there rotors to make lift. Besides turbine engine really suffers power loss in thin air. Jet air craft thin air still gets rammed into the engines air take at the speed the plane is traveling.

Answer 8

B/C most helicoters are designed for a maximum altitude of 20,000 feet

Answer 9

Dansity is the main problem.

Answer 10

because there isn't enough air for their propellers