# Need to find L/D ratio for F117

• Engineering
• vchi
In summary, an L/D ratio published everywhere on the web is not available for our project, but an online calculator can be used to estimate average lift.
vchi
Homework Statement
I was trying to look for an L/D ratio published on the web for the F-117 Nighthawk, and I can't seem to find it; need it for a class project. Since I couldn't find it, I wanted to try calculating myself, but still can't seem to find $$C_l$$ or $$C_d$$ without some sort of paywall on research papers, which I'm not even sure has them in it.
Relevant Equations
$$L = \frac{1}{2} C_{l} \cdot \rho v^2 A$$ ........................ lift equation

$$D = \frac{1}{2} C_{d} \cdot \rho v^2 A$$ ...................... drag equation
I was trying to look for an L/D ratio published everywhere on the web and I can't seem to find it for our project. Since I couldn't find it, I wanted to try calculating myself. Can't seem to find $$C_l$$ or $$C_d$$ though without some sort of paywall on research papers.

So L/D would just be:

$$\frac{L}{D} = \frac{C_l}{C_d}$$

or would the effective area be different for L and D, where L is the area of the top/bottom view of the plane, and D is the area of the front/back view? If this were the case then L and D would have to be determined separately.

The problem is that I'm still missing the C_l and C_d, for the F117, to complete this calculation. Does anyone happen to have access to this? Or is it top secret or something? Been scouring the internet for a couple hours now trying to look for it.

Here are the public specs. While officially inactive, F-117A flight data may not be available. For extra credit you can show the Nighthawk is a bomber, not a fighter.

Given the area measurements and flight regime you can estimate average lift. Keep in mind the F-117A was designed for stealth -- reduced radar cross section -- not elegant flight or speed. It is unstable in pitch, roll, and yaw; particularly at low speeds, controlled by on-board computers (fly-by-wire). While calculating lift, remember Lockheed designed the Nighthawk as a 'lifting body' with the fuselage contributing as well as the wings.

vchi

## What is L/D ratio?

The L/D ratio, also known as the lift-to-drag ratio, is a measure of the efficiency of an aircraft's wings. It is calculated by dividing the lift force by the drag force. A higher L/D ratio indicates a more aerodynamically efficient aircraft.

## Why is L/D ratio important for the F117?

The F117 is a stealth fighter aircraft designed for low observability. A high L/D ratio is important for this type of aircraft because it allows for longer flight times and greater range, which is necessary for stealth operations.

## How is the L/D ratio calculated for the F117?

The L/D ratio for the F117 is calculated using data from wind tunnel tests and computer simulations. Factors such as wing shape, airfoil design, and weight distribution are taken into account to determine the most efficient L/D ratio for the aircraft.

## What is the L/D ratio of the F117?

The L/D ratio of the F117 varies depending on the specific flight conditions and mission requirements. However, it is estimated to be around 4.5 at subsonic speeds and 6.5 at supersonic speeds.

## How does the L/D ratio affect the performance of the F117?

The L/D ratio plays a crucial role in the performance of the F117. A higher L/D ratio allows the aircraft to fly longer distances, maintain altitude, and maneuver more efficiently. It also contributes to the aircraft's low radar signature, making it more difficult to detect by enemy radar systems.

• Aerospace Engineering
Replies
2
Views
1K
• Aerospace Engineering
Replies
7
Views
997
Replies
1
Views
2K
• Engineering and Comp Sci Homework Help
Replies
7
Views
9K
• Engineering and Comp Sci Homework Help
Replies
4
Views
5K
• Engineering and Comp Sci Homework Help
Replies
3
Views
1K
• Mechanical Engineering
Replies
1
Views
1K
• General Engineering
Replies
13
Views
4K
• Mechanics
Replies
4
Views
425
• Introductory Physics Homework Help
Replies
19
Views
1K