Questions tagged [helicopter]

A helicopter is a type of rotorcraft in which lift and thrust are supplied by rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward, and laterally. These attributes allow helicopters to be used in congested or isolated areas where fixed-wing aircraft would usually not be able to take off or land.

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1answer
128 views

Do hospitals have radio communications with air ambulances?

Do hospitals have a sort of ATC for incoming medical helicopters? What kind of procedures do helis follow when landing at a hospital to make sure they are cleared to land/takeoff, etc?
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Should the helicopter be washed after any sea mission?

I was seeing this image: The caption of this image says (source): Here a Belgian NH90 NFH returning after a flight over sea. The helicopter is washed by the fire brigade to remove the salt water... ...
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What is this helicopter seen in the Falcon Crest TV series?

My next to last "Falcon Crest" related question for the database I'm programming: Does anyone recognize the make and model of this helicopter from episodes # 160 <7.05> (first screen ...
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1answer
119 views

Is it possible to stall a stationary helicopter through excessive collective input?

I understand that helicopters can suffer from "retreating blade stall" where the retreating side of the rotor has low airspeed and stalls in a typical way that airplane wings stall. This ...
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3answers
211 views

On the Ka-50 coaxial helicopter, why does the bottom rotor flap up on the right side instead of in front during forward flight?

In the game DCS World flying the Ka-50, when flying forward at high speeds, the bottom rotor will flap up on the right side of the helicopter (also note that the top rotor is flapping up on the left, ...
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Is axial dynamics important for the helicopter equations of motion?

While analyzing helicopter performance, why do we always ignore the axial dynamics from the equations of motion?
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Why do new helicopters have rotor blades with swept tip? [duplicate]

Many new helicopers have rotor blades with swept tip. Why? Acoustic? e.g.
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1answer
66 views

How to do blade element momentum theory analysis for different geometries of airfoil, e.g. NACA airfoils?

I want to analyse NACA airfoils using BEMT. I have only yet done it for basic symmetric airfoils. I would like to know what all assumptions remain same in NACA airfoil analysis and to what degree it ...
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2answers
103 views

Can a helicopter be stable without moving the control inputs?

I have only flown helicopters in a flight simulator (X-Plane) and I have found it exceedingly hard to fly in certain regimes (especially hovering and close to hovering) because it seems like there is ...
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193 views

Why do the intake of some helicopters have a bump body?

Not all but the intake of many helicopters have a bump body. Why? e.g.
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1answer
1k views

What is this hole above the intake of engines of Mil helicopters?

Almost all the helicopters designed and manufactured by Mil have a hole above the intake. e.g. What is it for? APU? Other helicopters made by this company:
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1answer
290 views

Why was the Sikorsky Firefly built but never flown?

Sikorsky Firefly is the electric helicopter that has been built but never flown. How do such histories happen? If the design looked so unsafe that there was not enough courage of trying, why this was ...
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Is it possible to build an ultralight helicopter with electric motors as its main engines? [closed]

So I'm trying to make an electric ultralight helicopter, but I'm not sure if it will work. Is it possible to use electric motors to make it fly? If yes, I'm going to need some advice. I'm expecting ...
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Per the AIM, Helicopter pilots may fly non-copter approaches at half the published visibility. Where is that in the FAR?

In AIM 10-1-2 Helicopter Instrument Approaches, paragraph a1 says the visibility reduction rule comes from 14 CFR Section 97.3. From what I can see, that section is just definitions. What is the AIM ...
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3answers
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Normal tendency of helicopter with counter clockwise rotating main rotors (top view) with force trim off and leaving controls?

Is it normal for the helicopter with CCW rotating main rotors to pitch down and roll left in forward flight, when force trim is turned off and hands off the cyclic? Moreover, when we put the ...
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1answer
148 views

What is rotor damping and how does it affect helicopter stability?

What do we mean by rotor damping (in terms of helicopters)? How is it affected by air density? How does helicopter stability depend on rotor damping?
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Sub-ideal Autorotation in Rotorcraft

I have another AuRo question for you. When a Helicopter autorotates (ideally) it is in the turbulent wake state and there is virtually no flow through the rotor disk (figure of Leishman attached). Now,...
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What is this helicopter type at a U.S. military base?

This helicopter is on a US military base, shown by Google Maps. I don't recognize the glass windows at the front top.
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Isn't it dangerous for a soldier to sit on the outside of a flying helicopter?

AH-64 during an extraction exercise at Camp Bondsteel, Kosovo in 2007 with a soldier on the avionics bay. I lit upon this image on Wikipedia. I see that the soldier is harnessed fastened to the ...
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Why did the pilot in this EC135 crash change the throttle setting after encountering wake turbulence?

I’m confused in this accident why the Eurocopter EC135 pilot decided to manipulate the throttle after encountering wake turbulence - I can’t think of a reason for this. Could someone please explain ...
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163 views

What forward airspeed produces maximum rate-of-climb in helicopters?

Lift in a helicopter increases with airspeed (from zero IAS up to some Vmax). But in contrast to fixed-wing aircraft a helicopter can generate lift at zero airspeed. Is there a formula for the ...
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0answers
56 views

What is the tail rotor rpm for the Sikorsky S58 helicopter?

I need to know the TR rpm for Sikorsky S58. I have tried searching for it and calculating it based on some assumptions I've made. I would like to know the true rpm value and not assume it since this ...
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What is the main and tail rotor speed (RPM) for a Sikorsky S52?

I need the RPMs for the main and tail rotor of a Sikorsky S52 for the research I am doing for my degree. I tried checking flight manuals and other websites, but I don't find concrete numbers, only ...
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Can the lift equation be used for the Ingenuity Mars Helicopter?

I am currently working on a basic simulation of the Mars Helicopter Ingenuity, and I am having trouble interpreting the outputs I am receiving from the lift equation. The equation reads as follows: L =...
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How does an accessory drive hydraulic system power a crop duster pump?

Aerial agricultural spraying uses pumps, which are usually powered electrically from the starter/generator. Now I have read, that these pumps can also be powered by an accessory drive hydraulic system....
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Why do helicopters have windows near the pedals?

What is the purpose of the clear windows in some helicopters in the floor of the nose, right where the pilot's feet and pedals are? For example, here's a Huey with windows clearly visible: Airbus ...
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Autorotation: Positive Pitch during descent phase possible?

I was wondering if a rotorcraft, that descends very slowly compared to its nominal rotor rotation rate (for example an RC Helicopter vertically autorotating with 3m/s descent rate and 2200RPM on the ...
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Did NASA just broke the world record for fastest aircraft by going over 10 times faster than the previous record?

The current world record is held by the Lockheed SR-71 Blackbird. In 1976, this aircraft reached a top speed of 3,529.6 km/h, according to Wikipedia. Fast forward 44 years, and NASA just launched the ...
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345 views

Is there other option than a Chinook to transport 2 cars simultaneously?

If a civilian wants to fly between homes several hundred miles apart AND carry 2 cars with him what are the options other than a chinook?
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Are there any true aerobatic helicopters that aren’t built around the Bo-105?

I know that some aerobatic maneuvers have been performed (legally or otherwise) in many different models of helicopters. However, to my knowledge, I have only heard of Bo-105s being specifically ...
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What are the expected vibration frequencies in a co-axial rotor system with contra-rotating propellers?

I am trying to understand the frequency spectrum of a co-axial rotor system. Form now i have a RC helicopter with two sets of three gear systems arranged in parallel, The number of teeth are 7,23,27) ...
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348 views

Is PVC tubing a good material for helicopter airframes?

Been thinking of getting into the hobby of building ultralight helicopters, and would PVC tubing be a good choice to build the overall airframe?
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CH-37 Mojave Helicopter decibels

What was the decibels level for the Sikorsky CH-37 Mojave Helicopter? 1956 --1959. I need this information for the VA, to process my hearing claim. I was a crew chief in the Army.
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What is the helicopter in the background of this image of the V-22 Osprey?

I found a photo of a V-22 Osprey alongside an unknown helicopter on the left corner:
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1answer
156 views

How does a bearingless rotor work on a helicopter?

I have read about some helicopters now using a mechanism referred to as a "bearingless rotor". From what I've seen online, the system involves a flapping hinge. What I struggle to get my ...
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What were those two military helicopters that I recorded?

I have recently recorded two military helicopters. Here is a screenshot of it:
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Helicopter retreating blade stall: Increasing the fwd speed decreases the tip speed on retreating side and angle of attack. So why limit on V_n.e?

On Retreating side: Speed of wind over blade tip = blade rotation speed - forward speed. So, with an increase in forward speed, the speed of the wind over tip is getting reduced. In airflow diagram, ...
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Why do helicopter operations avoid IFR?

In almost any airplane commercial operation, unless you’re doing something very short haul daytime ops, an Instrument Rating is all but required with airplanes(it’s even in the FARs). Generally the ...
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1answer
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How to say the name of this approach clearance: COPTER RNAV (GPS) 027°

JFK has this approach: https://aeronav.faa.gov/d-tpp/2006/00610COPTERR027.PDF How is this approach said on frequency? Is it the "copter RNAV zero two seven approach" or the "copter RNAV zero two ...
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What was this helicopter photographed on a Chinese aircraft carrier?

I've read this twit Chinese carrier got photographed by a satellite. On the nose you can find a helicopter and several people around it. What helicopter is that?
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Was flying a helicopter below building height against FAA regulations? [duplicate]

I'm referring to this incident: https://twitter.com/Dacheslow/status/1267638389421072384 Some people were saying it was illegal under FAA rules to fly that low and close to a crowd, and also to use a ...
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What are the applications, advantages and limitations of Gyrodyne rotorcraft?

Gyrodyne is a VTOL rotorcraft. It has ability to power both rotors and propellers for generating lift and thrust. What makes it of lesser popularity than helicopters. Are there any applications of ...
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1answer
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Helicopter Basics: How does lead-lag of blades actually help in compensating for increase/decrease in speed due to flapping?

I understand the following - Due to dissymmetry of lift, flapping up and down occurs. Since angular momentum has to be conserved, the speed of blade increases/decreases during flapping up/down ...
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1answer
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What does induced flow exactly means on helicopters flight? How is it different from downward deflection of air?

I believe all airfoils deflect air downwards at an angle at a velocity V. What is the difference between the downward-vertical component of the deflected wind and the induced velocity in Helicopter ...
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Helicopter flight: Does the rotor disc plane and hub plane rotate along axis perpendicular to rotational axis?

In many pieces of literature, diagrams as below are shown to explain the directional flight of Helicopter. I have the understanding that the cyclic input will only change the pitch angle of the blades ...
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1answer
164 views

What is this long Bar/Rod on the Boeing MH-47G? [duplicate]

This MH-47G has a thick, long rod at the bottom left front. What's the purpose of this thing?
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What is the purpose of a freewheeling unit in an helicopter, if a centrifugal clutch is already present?

Some helicopters such as the Bell 47 are fitted with a centrifugal clutch. Centrifugal clutch will engage only at certain engine RPM. If the engine fails, the engine RPM will reduce and the ...
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Helicopter Flight: What is the reason for decrease in Induced drag with increase in speed?

As per the figure the induced drag will decrease only if the AoA of the blade is decreased — But in the forward flight, cyclic input increases and decreases the AoA throughout the blade rotation cycle....
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1answer
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Is it possible to start another engine of Mil Mi 8 with one engine started and APU off?

In the 737NG, it is possible to start the other engine without APU if one engine is already started, by routing air from the started engine to the other one. Is this possible in the Mil Mi 8 ...
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1answer
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How are pitching and rolling moments transferred from rotor to the body?

When a rotorcraft pilot moves pushes on the cyclic control stick, the swashplate tilts so that angle of attack of the retreating blades increase and of the advancing blades decrease, which creates ...

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