119
EDIT
Huge apologies to one and all, in my first version of this answer I mistyped 184 as 84, and then proceeded to do all my calculations based on that. This is the corrected version.
Also, huge thanks for all the up-votes and comments. I'm so glad it's not just me that is enjoying this question immensely.
The radius of the ball in the image is 21 pixels....
100
Wouldn't they be more stable and easier to control than helicopters?
No, they would not.
Quadcopters don't have any special inherent stability. When you increase power of one of the rotors to pitch, the increasing pitch will not do anything to the power difference and therefore the pitching moment.
The advantage of quadcopters is that the rotors can be ...
72
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. Gordon Leishman, Principles Of Helicopter Aerodynamics:
The line for total power goes down between 0 - 70 kts with increasing airspeed, this is caused by the line ...
71
Police helicopters don't always fly in circles. I've often seen my local police helicopter hovering. There are a few reasons you might have seen police helicopters flying in circles:-
Not all types of helicopter can hover out of ground effect. It might be that the police helicopters in your area can't hover at the heights they work at, with the weight of ...
60
Special mention for Raúl Pateras Pescara de Castelluccio (good article) who was fond of lots and lots of rotor blades, settling on sixteen for most of his designs, although his Model 3 had twenty.
Pescara's helicopters may look a little comical (and dangerous!) but they are an important part of early helicopter evolution, pioneers in the first fully ...
58
Looks like a Mil Mi-6 with the rotor removed (like the adjacent two to the right). Here is the 3-view drawing overlaid:
(Google Earth @ 55°40'04.61" N 37°56'07.62" E)
The tail boom appears to be thicker than it is due to the angle, it'll make sense by taking the satellite's perspective. Note the fatter bottom:
Google Maps measurement; actual aircraft ...
56
First, they have been used, like in case of the Federation tower fire in Moscow on 2012. The image below shows a Kamov Ka-32A11BC being used to fight fire in that case.
Helicopter fighting Federation Tower fire in Moscow; image from dailymail.co.uk
According to a news article
The Ka-32A11BC proved its fire-fighting credentials in April 2012, when a ...
56
A few notes of update.
Evidence from other operators that there is no hard age limit
There is no upper or lower age limit for pleasure flight however we recommend that children under 12 are accompanied by an adult.
Central Helicopters T&C
Generally anyone can be a passenger on a pleasure flight. Young children should be accompanied by an adult....
55
The torque in a helicopter is generated by the engine driving the main rotor in one direction, which causes the fuselage to spin in the other direction. The tail rotor shaft is horizontally mounted and hence creates it own 'lift' to provide anti-torque. The pitch of the tail rotor gives directional control.
Common ways to design a helicopter without a tail ...
54
A helicopter will achieve its best climb rate at a moderate forward speed. Climbing in a spiral helps to have forward speed in what is essentially a vertical climb.
In a hover all the airflow which is available for lift creation must be generated by the rotation of the main rotor. This means that a small amount of air must be accelerated by a lot. If the ...
51
The helicopter would be a UH60 Blackhawk. Max payload on a hook is 9000lb. At your mild steel density this is half a cubic meter, so the picture as you describe is impossible.
50
Ex-Royal Air Force helicopter force here, spent a lot of time around Chinooks.
I think the main answer is "because I can", but I can think of a legitimate combat use.
You are heavy, and forced to land downwind into a narrow strip because there is a hazard on the upwind side of the landing zone. There is not enough room to turn around. You could hover ...
50
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 are the empennage and the outer wings missing, but also the engines, which helps to reduce the load considerably.
Mil-26 lifting a Tu-134 carcass, seen from ...
49
Helicopters are very inefficient in forward flight, for several reasons.
Consider Glauert's high speed assumption, i.e. the helicopter can be represented as an aircraft with a circular wing during high speed flight. Now, if you know anything about basic fixed-wing performance, you'll realize immediately that this implies an aspect ratio just over 1, ...
48
Of course the photo is absolutely real. I know a guy who knows a guy who says he met the guy in front!
3) Assume the wrecking ball is solid mild steel with a density of 7.85 g/cm3.
That's where you went wrong. The angle of the line and the drag equation allow us to determine the ball's mass, given a known velocity. The ball presents a frontal area of 11....
45
The reason for the failure is important actually. If all the electrical systems on an EC135 helicopter fail in your classic EMP scenario then the helicopter has to make an emergency landing as the jet engine is run by a computer system which requires electricity. A power failure of that system would most likely cause the engine to revert to manual backup, ...
44
Aircraft, fixed-wing or rotorcraft, have limited capability to produce a sideways force, so they simply can't throw you out.
It is a matter of physics. Inertial forces (gravity and centrifugal force) act on you and the aircraft the same, so they won't make you move relative to the aircraft. The only force between you and the seat is caused by the ...
43
The sound you're hearing is the APU (Auxiliary Power Unit) running.
Turbine (jet) engines turn at a much higher RPM than reciprocating engines. This means that an electric starter motor would have to be bigger and heavier in order to produce enough torque to get the engine moving fast enough. The bigger the engine, the bigger the starter (and the batteries ...
42
John K and Koyovis's answers are both correct. However, as a former pilot of the UH-60 and a mechanical engineer here is a simpler version.
A helicopter must be balanced. If the front is much heavier than the tail, then it can't fly safely as the nose is too low. If the tail it too heavy, then the same. The point of balance is called the center of gravity. ...
41
They do in fact exist, though they often use smaller helicopters. A Google search on the term "heli taxi" yields thousands of results, and while a lot are probably irrelevant, the first few pages give hundreds of operators around the world, ranging from companies ferrying passengers between airports and major cities to companies servicing oil platforms at ...
41
The most blades I've seen are 8 on the Mi-26.
Source
But the highest theoretical lifting efficiency is achieved with the fewest blades and experiments have been done with single blade rotors (with a counterweight - there were vibration problems that couldn't be resolved).
So in practical terms, the most lift for the least power is achieved with a 2 blade ...
41
You won't see it done in the fixed wing world unless the aircraft is tied down or otherwise securely restrained (like when you tie off the tail to something when hand starting your no-starter taildragger; some pilots just use chocks or parking brakes to hand bomb their airplane, but it's a terrible idea).
However, it's common in the helicopter world ...
40
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 for lift creation must be generated by the rotation of the main rotor. This means that a small amount of air must be accelerated by a lot. If the helicopter adds ...
38
Airplanes are much more efficient, much faster and scale better.
Helicopters are limited to around 150 knots because when flying forward the tip of the advancing blade must not exceed the speed of sound while the retreating blade must still move aft fast enough to produce lift.
Helicopters are also difficult to make large, because for efficiency the rotor ...
38
Forward flight is much more efficient than hovering. As airspeed builds, lift increases from "translational" lift as the air moves more horizontally over the disc. Since the relative airflow is more horizontal, the angle of attack for a given pitch angle is increased.
The vortices and turbulence move behind and down from the helicopter so undisturbed air ...
38
It's a stabilator used on the Blackhawk to reduce attitude changes with airspeed and to offset pitch effects from the tail rotor. It's part of the automatic flight control system.
All "traditional" design helicopters have horizontal stabilisers to push the tail down to reduce the nose down pitch in forward flight. Fixed ones are normally trimmed to ...
38
Yes, there has:
In the Iran-Iraq War, Wikipedia:
The war also saw the only confirmed air-to-air helicopter battles in the history of warfare, with Iraqi Mi-25s flying against Iranian AH-1J SeaCobras on numerous occasions. The first instance of these helicopter "dogfights" occurred on the first day of the war (22 September 1980): two Iranian SeaCobras ...
37
Helicopters are able to do something called autorotation if all thrust is lost.
In a helicopter, an autorotative descent is a power-off maneuver in
which the engine is disengaged from the main rotor system and the
rotor blades are driven solely by the upward flow of air through the
rotor. In other words, the engine is no longer
supplying ...
37
Juan de la Cierva's first autogiro did roll over, twice, and he then applied the principle of blade flapping, a stroke of genius. Flapping is created by allowing the blade to move up and down. Depending on rotor head design this is done in different ways:
By a flapping hinge at the hub, allowing vertical rotation.
By a teetering hinge on two-blade designs, ...
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