static loads--wheels

Richard

Richard

Final Approach
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Ack...city life
How would I determine what percentage of basic MT wt is carried by each wheel? Specifically, is there a formula or means other than weighing the a/c which would tell me the load on the tailwheel?

I'm asking because an A&P thought the Scott 3200 is undersized for the Stinson. Avox Systems (formerly Scott wheel) said there wheels were built primarily for Piper or Cessna and all the load data was carried out by them for their particular aircraft.

(The Scott is not original to this a/c and there is not a Form 337 since the alteration was completed in Canada. There may be an STC floating around somewhere. However, the FAA stamped their seal of approval when the a/c was recertified when it came back into the US registry.)


I feel I should be sending this straight to Tom but anyone with an opinion can and should chime in.
 
If you know the arm location of each wheel, and the empty cg and weight of the aircraft, it's a fairly simple algebra problem in balancing moments. First, as a basic matter of moments:

Wtot x ARMcg = (Wnw x ARMnw) + 2(Wmw x ARMmw)

Note that the "2" is because you have two mains each supporting half the load at that point. Second, the total weight of the plane is supported by the three wheels, or:

Wtot = Wnw + (2 x Wmw)

...so:

Wnw = Wtot - (2 x Wmw)

You can substitute that into the first equation, yielding:

Wtot x ARMcg = ((Wtot - 2 x Wmw) x ARMnw) + 2(Wmw x ARMmw)

... and solve for Wmw, and then solve for Wnw using Wnw = Wtot - 2 x Wmw.
 
Steve said:
I think Ron meant Wtw instead of Wnw for a tailwheel aircraft...
Click to expand...
DOH! Right you are, Steve -- I missed that even though it said "Stinson" and "tailwheel."

...the math works out the same since the CG is between the mains and either the nose or the tail depending on configuration.
Click to expand...
Right again.
 
Just like figuring out beam loads :)
 
Personally I'd skip the math and simply slide a bathroom scale under the tailwheel. Close enough for government work.
 
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