So helicopters have relatively low maximum altitudes due to limitations in low air density. Is this because the rotors are less efficient or the engines get starved of air?
If you had two theoretical helicopters, both with identical rotors, aerodynamics, weights, etc. one with a combustion engine and one with an electric engine, could the electric helicopter fly to a higher maximum altitude because it doesn’t lose power with altitude? Or will it still have limitations due to rotor efficiency or something else not related to the engine.
Theoretically we are assuming the flight time isn’t relevant and any cooling issues with the batteries and electric motors at high altitudes have been solved without changing any aerodynamics between the two helicopters.
In: Engineering
Issue is a loss of air density. Helicopters essentially work by throwing their weight’s worth of air below them. As you go higher and higher, the air gets thinner to the point that the helicopter is unable to generate enough thrust.
yes, gas engine helicopters have trouble with the thinner air. in general helicopters can only fly around 25k feet and hover around 10k feet. at higher altitudes, gas engine helicopters can use turbo chargers to compensate for the thinner air.
Helicopters are limited in altitude by two things: the lift produced by the rotor and the power produced by the engine. Both of those things decrease with altitude, so both of those things limit the altitude the helicopter can reach. It stands to reason that if you remove the engine power limitation by fitting an electric motor that doesn’t lose power as you climb, being left with your maximum altitude limited only by how much lift your rotor can produce, you’ll be able to go higher.
Reducing air density at high altitude and the ability of the rotor blades to create lift are a bigger issue than issues with turbine engines losing power vs electric motors.
In theory, you can just use a bigger turbine engine to offset the loss in power output.
Source : a wild guess.
The lift provided by the rotors depends on the air they can push down. Starving the engines of air doesn’t become a problem until after the rotors have an issue with the amount of air for them to push off of.
Batteries are heavy, so an electric helicopter would struggle to fly as fast or as far as an ordinary one, but it wouldn’t gain much in terms of height.
If airnfor the fuel was the issue, more air intakes or an onbaord oxidizer would push you much further, but it’s not the issue.
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Theoretical, of course, but don’t forget that batteries are insanely heavy, you’re theoretical helicopter might be able to go higher, but for probably a total of a total of a minute before it comes crashing down due to zero charge Left
It’s the air density mostly, air is too thin for the blades to get a good lift on the air
It’s like the difference between swimming in water and swimming in air, it’s easier to swim and float in water since it’s more dense but you’ll have a hard time swimming in air
Ummmm, does anyone here understand that helicopters don’t use gasoline? We use JP8 or JP4 or 100LL which means our burn rate isn’t the same as a car or airplane.
Air density applies to lift and thrust, not climb rate nor effective rate of climb by itself. Humans have this strange need for oxygen so high altitude air things need supplemental oxygen.
Yes, the helicopter controls (depending on make and model) may feel like spaghetti, but you reach a “service ceiling ” or operational attitude. At that point, you have several choices that involve gravity.
You either lose weight by burning fuel (crazy idea), slow down to increase rate of effective climb (without hovering, roughly 24-40 knots), wait for outside temperature to change (2 degrees per 1,000 feet in altitude, yup, gets cold up there), or catch an updraft like they do in the movies (unless you are performing mountain operations which means updrafts will become downdraft the moment you least expecte it, HATS).
But there is the more obvious answer here: why would you use a helicopter to conduct upper atmosphere work when there are aircraft designed for such work. That tiny tail rotor will hinder non tandem systems. Tail rotors can only spin so fast. Tandem rotor systems were the only helicopters allowed to conduct high attitude recovery operations in really, really high places (25-32K).
I’m not sure about other helicopter pilots but I don’t like hypoxia, hypothermia, nor high attitude work without proper training, proper equipment, and one hell of a good crew. I read that in a book somewhere.
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