Aircraft landing impact & tires forces analysis

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Discussion Overview

The discussion revolves around the analysis of forces acting on aircraft tires during landing, specifically focusing on friction torque, skidding, and slip ratio. Participants explore the dynamics of tire behavior upon touchdown and the complexities involved in such analyses.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant questions how to analyze the forces involved when an airplane touches down, particularly regarding friction torque and skidding.
  • Another participant suggests that the vertical sink rate must be considered, indicating that it complicates the analysis of friction issues.
  • There is mention of past experiments that attempted to measure the benefits of spinning up the wheels before touchdown, but these were abandoned due to a lack of observed benefits.
  • A participant proposes estimating the G loading on the landing gear for different landing weights, although they express skepticism about the value of such estimates.
  • Concerns are raised about the practical issue of trainee pilots accidentally landing with the wheel brakes engaged, which may be a more pressing question than the theoretical analysis of forces.
  • Another participant acknowledges the need for torque calculations specific to heavy airplanes but notes the complexity of the analysis involved.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility and value of analyzing the forces during landing, with some emphasizing the complexity and others suggesting practical considerations. No consensus is reached on the effectiveness of prior experiments or the best approach to the analysis.

Contextual Notes

Participants highlight the complexity of the analysis, including the need for specific data and the challenges posed by varying landing conditions. There are unresolved questions regarding the assumptions made in estimating forces and the relevance of past experiments.

aar2014
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how is the smartest, can do the analysis?
Ok
when the Airplane touch the runway. the rear wheels touch first, in part of second, the rear tires skidding and then start to spin up. I need to analysis the forces to find:
friction torque, skidding, slip ratio,...
you can use any data or just find the correct formula... thanks for all
 
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Surely the heart of the problem is that there is a vertical sink rate that the tires and hydraulics must absorb before any friction issues become amenable to analysis.
If memory serves, there have been experiments to measure the benefit from spinning up the wheels before touchdown. As no benefits were found, the effort was abandoned.
Consequently I doubt analysis of the forces has been achieved.
 
etudiant said:
If memory serves, there have been experiments to measure the benefit from spinning up the wheels before touchdown. As no benefits were found, the effort was abandoned.
You could make an estimate based on the G loading on the landing gear for "normal" and "heavy" landings. Whether the estimate would be worth much is another question.

How to stop trainee pilots landing light aircraft with the wheel brakes on (easily done by accident, if the brakes are close to the rudder bar) is probably a more important questiion!
 
yes, we need the torque to know how much torque required to spin the wheels. however, it is for heavy airplane. but the analysis is very complicated
 

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