80
votes
Accepted
Do helicopters use more fuel when hovering?
Yes it is correct that helicopters use more fuel when hovering: the engine needs to apply more power to overcome drag. Here is a graph of the engine power required for different airspeeds, from J. ...
- 62.9k
50
votes
Can a helicopter carry a large airplane?
If you look more closely, this "airplane" is only the husk of a Tupolev Tu-134, a rather small airliner, and the helicopter is a Mil-26, the heaviest helicopter ever to go into production. Not only ...
- 237k
42
votes
Do helicopters use more fuel when hovering?
Yes, it is correct, if the helicopter doesn’t fly too fast. A helicopter will produce the necessary lift most efficiently at a moderate forward speed.
In a hover all the airflow which is available ...
- 237k
39
votes
Would a helicopter with the blades on the bottom fly the same, if at all?
Yes that is possible, like the Hiller flying platform demonstrated. It had two counter-rotating propellers inside a shroud and the pilot controlled his craft by shifting his body weight, like on a ...
- 62.9k
30
votes
Do helicopters use more fuel when hovering?
Yeah, I'm not a physics student, but I work on Black Hawks. If you conceptualise a helicopter as just a main rotor disc producing lift, then Peter Kampf's answer about mass-flow through the rotor disc ...
- 301
26
votes
Why does a turbine helicopter need to spin a tail rotor?
Well, that’s complex. Where should I begin?
The main job of the tail rotor is to use its long lever arm and directed force/thrust (horizontal lift) to counteract the torque of the spinning main rotor....
- 16.6k
26
votes
Why does it take so long to stop the rotor of a helicopter after landing?
A minute isn't that long a time. Arranging the medevac flight plus the flight itself will typically take about 1 hour in one of the best healthcare systems. Urban medevac cycle times can be shorter, ...
- 30.1k
25
votes
Would a helicopter with the blades on the bottom fly the same, if at all?
We spend all our weekends mowing lawn with these guys.
Courtesy: Helifreak.com
You can find thousands of Youtube videos showing how comfortably they can do that
- 6,021
20
votes
Do you know the exact model and use of this rotorcraft?
It's a Bell TH-57, most likely a TH-57C, which is the Navy's variant of the Bell 206 JetRanger. It's used for VFR and IFR helicopter primary flight training for the Navy and Marine Corps. Most ...
- 75k
20
votes
Do helicopters use more fuel when hovering?
The concept is known as "translational lift". When moving in forward flight, a helicopter's rotor disc acts a lot like an airplane's wing - it has a significant lift-to-drag ratio. The required ...
- 4,640
17
votes
Can a tiltrotor fly safely with one engine?
Short Answer: yes. If they could not, they'd likely not get certified
One engine can drive both prop rotors.
After digging into an old version of the V-22 flight manual, I find a whole pile of tables ...
- 4,211
16
votes
Accepted
How do the Kaman K-225 rotor "planes" work?
These are a form of servo flap, commonly found on Kaman designs, but also on at least one early helicopter (namely, a coaxial rotor aircraft built by d'Ascanio (shown below):
As opposed to ...
- 3,776
14
votes
Would a helicopter with the blades on the bottom fly the same, if at all?
One of the first helicopters that really flew (c. 1918) was the 'Petróczy-Kármán-Žurovec', intended to be used by the Austro-Hungarian Army as a tethered observation platform. The observer stood above ...
- 11.2k
14
votes
Why do helicopters typically have blades at the top?
Yes the answer is that simple, that mincer needs to be out of the way so it doesn't chop peoples' head or feet off, or slashes into a bit of concrete and shatters into 100 pieces scattered around like ...
- 62.9k
14
votes
Accepted
Can a tiltrotor fly safely with one engine?
This concern was one of the major design challenges in the development of tilt-rotor VTOL craft. In every flying example I'm aware of, it was solved one of two ways: either the engines were embedded ...
- 17.3k
13
votes
Accepted
What is the reasoning behind Kamov twin-rudder design?
It's kind of a hard one. It looks like in this helicopter directional stability is a challenge because:
the tail arm is quite short;
there is no tail rotor, which provides directional stability just ...
- 62.9k
13
votes
Accepted
Why do helicopter rotors have constant section and angle of attack?
Helicopter blades do have twist. The relative air speed increases from blade root to blade tip, and therefore on an untwisted blade lift would increase quadratically from root to tip. Or going the ...
- 62.9k
12
votes
Is it more efficient to have many or a few rotors?
The problem with many propellers is that more of the propeller slipstream will flow around wings and tail. The higher local flow speed might be beneficial if you want blown flaps, but for regular ...
- 237k
12
votes
Is it more efficient to have many or a few rotors?
Rotors need something to power them and the current generation of aircraft (once you get bigger than model size) burn hydrocarbons to get that power. If you want twelve rotors, then you either need ...
- 12k
12
votes
What is the airspeed record for a helicopter flying backwards?
Inspired by Jpe61's answer I checked the flight manual of the Chinook, and it mentions
"Maximum airspeed in rearward flight is 45 knots" (23.15 m/s)
This value is rather close to the upper ...
- 8,272
10
votes
Would it take 7 to 10 times more energy to lift a turbofan-helicopter?
Helicopter rotors are very large precisely for that reason. Lift from a rotor (or thrust from a propeller or fan) is obtained by accelerating a given mass of air m to a velocity v. The thrust obtained ...
- 11.2k
10
votes
Do helicopters use more fuel when hovering?
When in a hover, the air has more time to setup into an induced wash from further upwards that translates into higher down flow speed by the time the induced wash reaches the plane of the rotor. When ...
- 534
10
votes
What is the airspeed record for a helicopter flying backwards?
This video:
Chinook CH-47 Roll and flying backwards amazing to see at RIAT 2017 shows a Chinook taxiing backwards and the proceeding to take off at the same backwards speed. I estimated it travelled ...
- 30.5k
8
votes
Why are RC rotor blades different from helicopter blades?
If the rotor was mechanically strong enough to lift the desired weight
It wouldn't be. Because of the square-cube law, lift and mechanical strength grow with second power of linear size, but weight ...
- 56.5k
8
votes
Why does a turbine helicopter need to spin a tail rotor?
The turbine output is very hot and therefore needs to be shielded in some way if it is to be routed through any part of the helicopter. This shielding adds cost and weight, so it's generally avoided. ...
- 81
8
votes
Why does it take so long to stop the rotor of a helicopter after landing?
If you were building a helicopter specifically for medivac and price was no object, there's nothing stopping you from doing it, but, the price will be a lot of weight, both for a brake large enough to ...
- 136k
8
votes
Why does it take so long to stop the rotor of a helicopter after landing?
Your question makes a lot of sense from a theoretical perspective and I have no good answers for the technical questions like whether a supplemental brake is possible because that's not the sort of ...
- 321
7
votes
How does a helicopter hover?
A helicopter can hover without the CoG being directly underneath the rotor hub, because the rotor hub can apply hinge moments:
Fully articulated hubs with a hinge offset and fixed hubs apply direct ...
- 62.9k
7
votes
Accepted
Helicopter mast bumping in low g condition
The answer is yes it could be used in that flight profile as the pilot of that AS300 was never in a low G condition with the rotor unloaded during those maneuvers. Once he dropped the concrete, ...
- 75k
Only top scored, non community-wiki answers of a minimum length are eligible