# Single main rotor helicopter

• Marco9518
In summary: I have tried to reproduce it as accurately as possible.Is that the equation that is highlighted in the picture?It seems to be the lift contribuited by the fuselage while the helicopter is vertically descending for landing, which should equal its drag.
Marco9518
Hello everyone!
I am currently developing a thesi to become an aeronautical engineer.
I am trying to reproduce the NASA report "a mathematical model of a single main rotor helicopter for piloted simulation".
I already built a simulink model but i am having a bit of trouble looking at the equations.
I uploaded a picture of the equation's set. I can't explain the L equation highlighted.
How can the lift be 0 when the angle of attack is 90 or -90 deg? cos(90) is zero, but at that alpha the lift should be maximum.

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Lift is always defined perpendicular to the inflow. So if at cos(90), then I guess the blades are not rotating and your chopper is falling straight down. But the lift is now defined perpendicular to the inflow, which is directed in the horizontal plane, so you will not ever get any lift from this 'lift'... :) Only some from the drag component, which is directed vertical in this case.

Marco9518 and Lnewqban
What angle does alpha represent in that equation?

Marco9518
Marco9518 said:
I am trying to reproduce the NASA report "a mathematical model of a single main rotor helicopter for piloted simulation".
Here is a link to that report for background info for everybody:

https://ntrs.nasa.gov/citations/19830001781

Marco9518
Marco9518 said:
How can the lift be 0 when the angle of attack is 90 or -90 deg? cos(90) is zero, but at that alpha the lift should be maximum.
Why do you say this? At that angle of attack, there will only be drag. That would be the air hitting the blade broadside. (Is this angle of attack with respect to the blade motion or to the vehicle motion?)

Last edited:
Marco9518
Arjan82 said:
Lift is always defined perpendicular to the inflow. So if at cos(90), then I guess the blades are not rotating and your chopper is falling straight down. But the lift is now defined perpendicular to the inflow, which is directed in the horizontal plane, so you will not ever get any lift from this 'lift'... :) Only some from the drag component, which is directed vertical in this case.
Thank you a lot for your answer. So at the moment i am modelling the fuselage alone and i am not taking into account any other component. As soon as i figure this out i will add the rotor inflow. For what i understand it is than possible for the lift to be zero at that angle of attack.

FactChecker said:
Why do you say this? At that angle of attack, there will only be drag. That would be the air hitting the blade broadside. (Is this angle of attack with respect to the blade motion or to the vehicle motion?)
Thank you a lot for your answer. So at the moment i am modelling the fuselage alone and i am not taking into account any other component. Talking about the angle of attack, they did not make very clear the reference axis. I supposed it to be with respect to the fuselage motion.

Lnewqban said:
What angle does alpha represent in that equation?
The way i formulated it, it represents the angle between the direction of the flow and an ipotetical "chord" that goes from the nose to the tail of the fuselage.

Marco9518 said:
The way i formulated it, it represents the angle between the direction of the flow and an ipotetical "chord" that goes from the nose to the tail of the fuselage.
It seems to be the lift contribuited by the fuselage while the helicopter is vertically descending for landing, which should equal its drag.
In that case, I can’t understand that equation; sorry.

## 1. What is a single main rotor helicopter?

A single main rotor helicopter is a type of aircraft that uses a single large rotor mounted on top of the aircraft to provide lift and control. It is the most common type of helicopter and is used for a variety of purposes such as transportation, rescue operations, and military missions.

## 2. How does a single main rotor helicopter stay balanced?

A single main rotor helicopter stays balanced through the use of a tail rotor, which counteracts the torque produced by the main rotor. This allows the helicopter to hover and move in different directions while maintaining stability.

## 3. What are the advantages of a single main rotor helicopter?

Single main rotor helicopters have several advantages, including their ability to hover and take off and land vertically, making them suitable for use in small or confined spaces. They also have a higher lifting capacity compared to other types of helicopters and can fly at higher altitudes.

## 4. What are the disadvantages of a single main rotor helicopter?

One of the main disadvantages of a single main rotor helicopter is its complex control system, which requires skilled pilots to operate. They also tend to be more expensive to maintain and operate compared to other types of aircraft.

## 5. How does a single main rotor helicopter differ from a dual main rotor helicopter?

A single main rotor helicopter differs from a dual main rotor helicopter in that it only has one main rotor, while a dual main rotor helicopter has two. This affects their flight characteristics, with single main rotor helicopters being more maneuverable and dual main rotor helicopters having a higher lifting capacity.

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