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55 votes

Can all helicopters hover, and how long does it take to "stop"?

As noted in another answer, all helicopters can hover, but a so-called "high hover" (out of ground effect or especially at operational altitude) is a more difficult maneuver, requiring more power than ...
Zeiss Ikon's user avatar
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48 votes

What is it exactly about flying a Flyboard across the English channel that made Zapata's thighs burn?

He's using the angle of his legs to control the attitude of the platform (and as a result, the direction he's flying in). So he can't take a relaxed pose, he's standing with his knees slightly bent ...
Hobbes's user avatar
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41 votes
Accepted

What is it exactly about flying a Flyboard across the English channel that made Zapata's thighs burn?

This is what he said after the 1st attempt "When you fly with your body, even your hands affect the direction you want to go in. You feel the turbulence and the air through your fingers," Zapata ...
CrossRoads's user avatar
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32 votes

Can all helicopters hover, and how long does it take to "stop"?

Yes all helicopters can hover, but it requires: More concentration to hover than to fly, because helicopters are unstable in the hover in pitch and roll. Forward airspeed provides stability and ...
Koyovis's user avatar
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24 votes

What is it exactly about flying a Flyboard across the English channel that made Zapata's thighs burn?

There is another bit of information worth mentioning in the CNN link in CrossRoads' answer The flyboard looks like a chunky skateboard and is powered by five small engines. It is fueled by ...
Pavel's user avatar
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16 votes

Why do helicopter performance charts for hover out of ground effect (HOGE) have a "knee"?

The knee is a result of having the engine "flat rated", that is rated to a power limit that is below its potential wide open throttle horsepower at sea level, a very common practice with ...
John K's user avatar
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12 votes

Can all helicopters hover, and how long does it take to "stop"?

When navigating WX in a helicopter, it is often less workload to fly orbits. It gives additional perspective and permits easy lateral movement during the course of the orbit. It also reduces ...
mongo's user avatar
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10 votes
Accepted

Can a F-35 shoot while hovering?

No, it cannot, at least there is no reason for it to do so... A) The stick while in "hover mode" does not control the pitch/roll of the aircraft, but the forward/lateral position of the aircraft. ...
Ron Beyer's user avatar
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10 votes

Why would a helicopter hold a 'nose-up' in hover?

1) The 60 has a natural nose up, left wing down hover attitude. I want to say 3, and 1.5 degrees, but I'm going off memory. Given the angle of the shot, I would venture to say that it's more optical ...
Tom's user avatar
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9 votes

Why is ground effect greater over smooth hard surfaces?

From a conservation of energy perspective, the rotor is transferring energy to the air, which then moves down and is deflected by the ground. A soft or drag-inducing surface will absorb more of that ...
zymhan's user avatar
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8 votes

Can all helicopters hover, and how long does it take to "stop"?

When a helicopter hovers, it's basically is sitting in its own wash. By pushing air down, it creates a low pressure region above itself, and a high pressure area below it. To stay hovering, it has to ...
Acccumulation's user avatar
7 votes
Accepted

Why is tethered hover testing performed on helicopters?

The cable is attached to the helicopter with a tensionometer. This can be used to vary the effective weight of the helicopter by varying the tension applied to the cable. The cable length can also ...
Simon's user avatar
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7 votes

Why does a hovercraft lift blade look one way, but a propeller another?

Because lift propellors need to provide static pressure to inflate the airbag and hover. This means more fan blades to stop backflow. The thrust propellors need to provide force which is a ...
ratchet freak's user avatar
6 votes

Can all helicopters hover, and how long does it take to "stop"?

Question 1: No, an S-76 can hover, but it's more energy intensive than economy cruise. It made more sense to circle and hold in an area as opposed to hovering. In addition, hovering at altitude can be ...
Romeo_4808N's user avatar
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6 votes

Why does the Zapata Flyboard Air UL consume so much more fuel/hr than the Mosquito Air?

It's the difference between jet engines and propellers. It is a lot more efficient to accelerate more air to a low velocity, than it is to accelerate less air to a higher velocity. For fixed wings, ...
Koyovis's user avatar
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6 votes

What size jet engines would it take to make a Cessna 140 hover?

The AV-8B has a maximum thrust of 23,500 lbf for a VTOL MTOW of 20,750 lbs. For a plane the weight of the Cessna 140, which weighs 1450 lbs loaded, you'd need total thrust of about 1640 lbf. So 410 ...
Therac's user avatar
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5 votes

Why does a hovercraft lift blade look one way, but a propeller another?

There are two parts to this: number of blades and squared off tips. 1. Number of blades. A propeller blade is actually just a wing. This is true regardless of weather you are talking about a piston ...
slebetman's user avatar
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4 votes
Accepted

How does the Bell V-280 (a tiltrotor) rotate, bank, and fly sideways?

The yaw would be accomplished by angling one rotor a little forward, and the other a little backwards. The shifting move to the side is accomplished by generating more thrust on one side. Either by ...
Noddle's user avatar
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4 votes

Can all helicopters hover, and how long does it take to "stop"?

Not all can hover indefinitely. A fully loaded Soviet era MI-24 Hind attack helicopter could only hover for 15-20 seconds, before the engines are damaged from the overload. US intelligence agencies ...
tj1000's user avatar
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4 votes

Is there any existing engine which can be converted to turbofan from turboshaft in mid flight?

The closest one is the P&W F-135, used in the F-35B VTOL-capable fighter. However, it switches between turbofan and turbofan+turboshaft modes. The fan's still running, but its flow is redirected ...
Therac's user avatar
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3 votes

Why does the Zapata Flyboard Air UL consume so much more fuel/hr than the Mosquito Air?

First, let's compare apples to apples, and compare the Flyboard to the Mosquito XET, the gas turbine powered version. The Mosquito XET with it's 90hp Solar turboshaft engine consumes around 8.5 gph, ...
tj1000's user avatar
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3 votes

Can all helicopters hover, and how long does it take to "stop"?

As many of the other commenters here mentioned, it is much easier and lower work load for the pilot to fly forward than hover. It also takes more power from the engine to hover than it does to fly ...
Tom K's user avatar
  • 611
2 votes

Would this hovercraft be stable?

Yes - it can work. Colin Furze (UK inventor & TV personality) built an essentially similar device. Skip to about 1:40 to see some of the problems he had.
CatchAsCatchCan's user avatar
2 votes

Why do helicopter performance charts for hover out of ground effect (HOGE) have a "knee"?

There is something in section 7-4 about using the collective above a certain altitude to maintain rpm once the engine is maxed out on power. The steep part of the weight vs maximum hover altitude ...
Robert DiGiovanni's user avatar
2 votes

What size jet engines would it take to make a Cessna 140 hover?

How many engines do you want to use? In each VTOL, weight is key! As each engine you have to lift means, more duplicate weight (housing, fuel systems, starter etc.) it follows that you want as few ...
U_flow's user avatar
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2 votes

What size jet engines would it take to make a Cessna 140 hover?

Making a VTOL Cessna 140 might be possible, but you'd probably end up needing to get a Supplemental Type Certificate if you intend to use the aircraft afterwards. Firstly, the Continental O-190 engine ...
Heat Router's user avatar
1 vote
Accepted

Hover Performance in Helicopter dynamics

You may want to check out the "figure of merit." It's not perfect, but is a useful metric of hover performance. A figure of merit of 0.8 is considered good according to some sources. ...
Mat's user avatar
  • 440

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