Calculating Aircraft Lift Capacity: Understanding the Equation

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Discussion Overview

The discussion revolves around the calculation of lift capacity for an aircraft using the lift equation. Participants explore the implications of various parameters such as air pressure, velocity, wing area, and the coefficient of lift, while considering the complexities involved in determining maximum lift capacity.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant presents the lift equation and calculates a lift force of 1170 lbs based on specific conditions, questioning if this represents maximum lift capacity.
  • Another participant clarifies that the calculated lift force does not necessarily indicate the maximum achievable lift, as it varies with angle of attack and altitude.
  • A participant emphasizes the importance of using consistent units, suggesting that velocity should be in feet per second for proper unit cancellation.
  • Another contribution notes that lift can also be generated by the fuselage and tail, indicating that all lifting forces must be considered along with the wing's maximum coefficient of lift.
  • One participant raises points about the dependence of lift on the wing's shape and the angle of attack, questioning which angle should be considered for accurate calculations.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of the calculated lift force, with some emphasizing the need for further experimentation and consideration of additional factors affecting lift. There is no consensus on whether the calculated value represents maximum lift capacity.

Contextual Notes

Limitations include the need for precise definitions of parameters such as angle of attack and the maximum coefficient of lift, as well as the complexities of real-world conditions affecting lift generation.

AaronWeber
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This is a simple question hopefully.

The equation for determining lift produced by an aircraft is the following if I am correct:
L = (1/2) d v2 s CL

If I was designing an aircraft that would maintain flight at standard air pressure at 1000 feet .002308 ISA at 130 MPH with a wing area of 60 Sq Ft. and a Coefficient of lift of 1, then I would plug the numbers in accordingly..
(.5)*(.002308)*(130^2)*(60)*(1) = 1170
Would this mean that the maximum lift capacity for this type of plane be 1170 lbs, or am I way off base here?
 
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What you calculated is the lift force on the wing at those conditions. You don't know that it's the maximum achieveable by the profile of the wing. The lift on the wing will change with angle of attack and altitude, and it isn't neccessarily max at 0 degrees.

The equation relating these is complex, you'd have to do experiments to find out. I've done it using a wind tunnel and CFD simulations.
 
Last edited:
Also your velocity should be in ft/s rather than mph so your units cancel appropriately.
 
yes.. keep the units straight...

the above formula is good for approximations...

but keep in mind.. the fuselage can create lift.. as well as the tail.. (Lift downward actually)...
so the sum of all lifting forces need to be considered...
as well as a particular wings Cl max...
 
Think of:

1. The actual 3D wing will have a CL max, depending of the shape of a 2D section or profile and on the shape tec. of the actual wing.
2. The Lift generated depends on the angle of attack and thus the CL. So what angle of attack do you consider?
3.
 

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