Gear Load Factor (Reaction Load) Question

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In summary, the conversation discusses using the equation to determine shock stroke in aircraft landing gear design. The speaker assumes a gear load factor of 5, which is common for Navy fighter aircraft. They want the landing gear to be able to handle a STOL aircraft and function similarly to a carrier landing. The question is why an increase in gear load factor results in a decrease in shock stroke. The other speaker explains that the load on the airframe depends on how fast the vertical velocity is reduced to zero, and that a low load factor requires a longer shock strut compression distance. The speaker thanks them and acknowledges that they had not considered the time necessary to decelerate the vertical component to zero.
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TL;DR Summary
Why does an increase in gear load factor decrease shock stroke?
Using the equation to determine shock stroke I input a gear load factor. For the aircraft landing gear that I am designing, I am assuming a gear load factor of 5 which is what is generally used for Navy fighter aircraft. This is because I am designing landing gear for a STOL aircraft and I want it to be able to drop right onto the landing spot more like a carrier landing. The question I have is why does an increase in gear load factor decrease the shock stroke? Perhaps I don't understand the concept of gear load factor very well, but I would assume that a harder landing would demand a greater shock stroke.
 
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  • #2
Aircraft landing gear design starts with an assumed vertical velocity component. The landing gear absorbs that vertical velocity component by compressing the shock strut. The load on the airframe depends on how fast that vertical velocity is reduced to zero. If the landing gear has long struts with soft springs and low damping, the force is low while the compression distance is long. If the landing gear is rigid, with no compression distance, then the force is very high and things get broken.

Your analysis is turning that around by starting with the allowable load factor, and using that to find the required shock strut compression distance. A low load factor requires a long stroke to gradually decelerate the vertical velocity component. A high load factor stops the vertical component faster, so needs less distance.
 
  • #3
That makes sense and thank you. It looks like taking into consideration the time necessary to decelerate the vertical component to zero is a factor that I was overlooking.
 

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