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On an airplane with tricycle gears, the main gear supports most of the weight and is therefore the strongest. The nose gear prevents the nose tipping down, since the center of gravity is forward of the main gear.

What is the typical ratio of weight distribution between the nose gear and all main gears?

For the purpose of the question, I'm mostly interested in airliners, although an answer comparing that with GA would be useful as well. I understand that the weight distribution varies with loading, so perhaps a range would do (e.g. on most airliners the max nose gear loading cannot exceed X:Y).

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    $\begingroup$ Related: Page 235 of this A350-900 Airport planning document, or this screenshot. Logically this ratio is the half the ratio of gear distances to the CG, and in the case of the A350-900 about 5.5 (depending on the balance). I believe the largest force on the main gear is during the touchdown. $\endgroup$
    – mins
    Aug 19, 2016 at 14:20
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    $\begingroup$ @mins Yes, while some very light 'greaser' landings might be exceptions, a normal landing is definitely the largest force on the main gear, as the force has to accelerate the entire mass of the airplane upwards with a magnitude equal to its prior downward motion over a rather short distance (the compression of the tires and gear struts.) The main gear has to be designed to deal with forces much larger than what it encounters while just sitting around on the ramp. $\endgroup$
    – reirab
    Aug 20, 2016 at 4:37
  • $\begingroup$ kevin, could you perhaps specify roughly what type of plane you're wondering about (e.g. large transport category, light GA, etc.?) I'd guess this varies quite a bit between different classes of airplanes. $\endgroup$
    – reirab
    Aug 20, 2016 at 4:39
  • $\begingroup$ Also, this will depend on how you've loaded the aircraft. If you load it with the CG far enough aft, the nose gear supports no weight at all. However, this is usually a bad idea. $\endgroup$
    – reirab
    Aug 20, 2016 at 4:47
  • $\begingroup$ Related: aviation.stackexchange.com/questions/16447/… $\endgroup$
    – Peter Kämpf
    Aug 20, 2016 at 14:42

2 Answers 2

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Look at the sketch of the recommended gear placement relative to the center of gravity (cg) from this answer:

side view of tricycle gear layout

We can calculate the load distribution for both extremes. For simplification we use the same angle of 60° for the nose wheel in both cases:

  1. Main landing gear 6° aft of cg: $\frac{\tan 6°}{\tan 60°}$ = 6%
  2. Main landing gear 20° aft of cg: $\frac{\tan 20°}{\tan 60°}$ = 21%

Add some dynamic loading from the application of wheel brakes. In this answer it is shown that the horizontal braking force is less than 30% of the maximum static weight of the aircraft, and applying this knowledge to the nose gear at 60° from the cg adds 0.3$\cdot\cos 60°$ = 15% of the maximum static load of a fully loaded aircraft to the nose gear load.

In extreme cases the nose gear would carry almost half of the aircraft mass, but then rotation would be impossible. In case of the Go-229 it was 45%.

Semi-finished Go-229 V3

Semi-finished Go-229 V3 (picture source)

On the other extreme you find nose gears with zero static load which were only intended for taking the braking forces.

Zeppelin Staaken R VI

Zeppelin Staaken R VI (picture source)

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Jenkinson recomends at least a static load of 8% W on the nose-wheel to give reasonable steering forces. Also not more than 15% W static load on the nose-wheel, as more than this will make it difficult to rotate the aircraf. Furthermore it is importent to provide an adequate reverse stabilising moment for backward towing and general stability.

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