# Question: Helicopter over a scale

• B
• HawkHunt
In summary, the scale would register a force upon departure and this would be dependent on many factors, including the rotational speed of the helicopter and the mass of the air.

#### HawkHunt

Hey all,

This is clearly a very simple question but for some reason my roommate and I just can't agree on this.

The scenario is as follows: There is a helicopter sitting on a scale. The helicopter weighs 700kg and thus has 700*g = 6867 N of force acting on it by gravity. In order to fly the helicopter must overcome its own weight and so it must produce >6867N of lift.

The question is, how much does the scale register on the millisecond the helicopter leaves the scale. My reasoning is that the scale must register 6868N atleast.

It would help if you told us why you think that. I have a theory that might not be correct, but I'd like to hear your thoughts first, so as to not poison the water.

Assuming the scale is fully supporting the downstream or air, it would depend on the vertical force applied to the helicopter during the period leading up to T+0.001 seconds and the time it takes for that force to be transferred through the air.

If the rotor generated 0 lift at T=-0.0001 and 2G's starting at T=0, then the scale would likely register 0 at T=0.001 - because no downdraft would have been generated in time to reach the scale that soon.

HawkHunt said:
The question is, how much does the scale register on the millisecond the helicopter leaves the scale. My reasoning is that the scale must register 6868N atleast.
F=ma.

(with what vertical acceleration does the helo leave the pad?)

DrClaude and CWatters
berkeman said:
F=ma.

(with what vertical acceleration does the helo leave the pad?)
@HawkHunt did not pose this question in the classical way - that is, as a steady state problem. So secondary effects (like the mass of the air and how quickly the rotor has spun up) need to be considered as well.

## 1. What is the purpose of a helicopter hovering over a scale?

A helicopter may hover over a scale to weigh its own weight or the weight of its cargo. It can also be used to assess the weight of objects on the scale or to calibrate the scale.

## 2. How does a helicopter affect the accuracy of the scale?

The presence of a helicopter can affect the accuracy of the scale due to the strong winds it creates. This can cause the scale to fluctuate and give inconsistent readings. It is important to take this into consideration when using a scale near a helicopter.

## 3. What type of scale is typically used for weighing helicopters?

Helicopters are typically weighed using a platform scale or a load cell scale. These types of scales are able to support the weight of the helicopter and provide accurate readings.

## 4. Why is it important to weigh a helicopter?

Weighing a helicopter is important for several reasons. It allows for proper weight distribution, which is crucial for safe flight. It also helps determine the amount of fuel needed for a flight and ensures that the helicopter is not overloaded, which can lead to mechanical issues.

## 5. How is the weight of a helicopter determined?

The weight of a helicopter is determined by adding the weight of the helicopter's components, such as the body, engine, and fuel, as well as the weight of any cargo or passengers on board. This is typically done by using a scale or load cells placed under the helicopter's landing gear.