Question: Difference between FAR 23.397 and 23.143

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Discussion Overview

The discussion centers on the differences between FAR 23.397 and FAR 23.143, specifically regarding pilot forces and control surface loads in aircraft. Participants explore the implications of these regulations on aircraft design and safety, with a focus on the definitions of maximum and minimum forces.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants explain that FAR 23.143 specifies the maximum permitted pilot forces for safe aircraft control, while FAR 23.397 addresses the maximum loads on flight control surfaces resulting from those pilot forces.
  • Others argue that FAR 23.143 sets a limit on the physical strength required of pilots for normal flight operations, whereas FAR 23.397 ensures that excessive pilot forces do not damage the aircraft's control surfaces.
  • A participant questions the necessity of quoting minimum forces in FAR 23.397, suggesting it may be meaningless.
  • Another participant references Note 2 regarding wind gust loads on control surfaces as a potential justification for the minimum values in FAR 23.397.
  • There is a suggestion that understanding the broader context of regulations from sections 391 to 459 may clarify the individual regulations.

Areas of Agreement / Disagreement

Participants express differing views on the significance of minimum forces in FAR 23.397, indicating that the discussion remains unresolved regarding their necessity and implications.

Contextual Notes

Participants acknowledge the complexity of understanding individual FAR regulations without considering their interconnections, suggesting that further reading may be required to grasp the full context.

jonathanpun
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Hi,
Can anyone here can explain to me the difference between FAR23.397 and 23.143?
What's the maximum and minimum force represents in 23.397?
 
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143 gives the maximum permitted pilot forces to safely control and maneuver the aircraft.
398 says the maximum loads on the flight control surfaces must never exceed what would resullt from the given pilot forces.

In other words, 143 is a limit on the physical strength the pilot needs to have, to fly the plane "normally" in a safe manner. 398 says that if the pilot applies a greater force to the controls (for example in an emergency situation), the control system much stop the pilot from damaging the aircraft by applying excessive force to the control surfaces.
 
Last edited:
AlephZero said:
143 gives the maximum permitted pilot forces to safely control and maneuver the aircraft.
398 says the maximum loads on the flight control surfaces must never exceed what would resullt from the given pilot forces.

In other words, 143 is a limit on the physical strength the pilot needs to have, to fly the plane "normally" in a safe manner. 398 says that if the pilot applies a greater force to the controls (for example in an emergency situation), the control system much stop the pilot from damaging the aircraft by applying excessive force to the control surfaces.

Then I think that FAA will only quote the maximum force in 397. Why they quote the minimum force in 397? It's meaningless?
 
See the cross-reference in Note 2 to wind gust loads on the control surfaces when the aircraft is on the ground (section 415). That gives one use for the "minimum" values in the table in 397.

I'm not a "expert" on this part of FAR, but in general, it's hard to understand individual regulations without getting the big picture of how they fit together. Reading the whole section from 391 to 459 might help.
 

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