N34KP new weight and balance

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Richard Roller
Posts: 78
Joined: Mon May 22, 2017 11:14 am
Location: Olathe, Ks.

N34KP new weight and balance

Post by Richard Roller »

Hey everyone.
N34KP had a new weight and balance ran on it today.
Some background. N34KP was built by Ken Perkins from Olathe Ks. The aircraft was finished in 1999, but suffered from an aft C.G. problem. When weighed with Ken in the pilot seat and full fuel, the aircraft was 3.37” aft of the recommended aft C.G. We moved the engine 7” forward to correct the C.G. Three years later Ken decided he wanted to put a gleaner/combine block on the Model A. The block is heavier and stronger in the bearing webs. When I asked Ken what the weight difference was, he said, “about 7 pounds”. So I refigured the weight and balance based on that figure. It moved the C.G. forward .38”.
Now for the real world. All aircraft gain weight over their lifetimes. But something this small, with no major mods or additions to the airframe, doesn’t normally gain 20 pounds! So it would seem that Ken’s estimate of the block weight was incorrect. N34KP definitely does not have an aft C.G. problem.

N34KP was weighed with full water and oil and with the fuel drained down to residual in the flight attitude. The datum is the forward face of the lower firewall.
Item number of weight c.g. moments
Left main 1 351.1 16.75 5,880.93
Right main 1 345.0 16.75 5,778.75
Tail wheel 1 -1.2 158.5 -190.20 (yes, negative 1.2 lbs.)
Totals 694.90 16.51 11,469.48
9.01 aft of leading edge

Up 20.9 pounds over the 2001 figures, using the same scales.

Aft C.G. check:
Item number of weight c.g. moments
694.90 16.51 11,469.48
Pilot 1 230.00 60.32 13873.60
Co-pilot 1 150.00 23.0 3450.00
Fuel 12.5 75.00 29.98 2248.50
Totals 1149.9 27.00 31041.58
19.5 aft of leading edge

Forward C.G. check:
Item number of weight c.g. moments
694.90 16.51 11,469.48
Pilot 1 105.00 60.32 6333.60
Fuel 5.00 30.00 29.98 899.40
Totals 829.90 22.54 18702.48
15.04 aft of leading edge

Doesn’t hurt to check, does it? I'd like to thank my lovely wife, Lisa, for her help with the weight and balance.
Last edited by Richard Roller on Tue Jun 23, 2020 6:33 pm, edited 1 time in total.

User avatar
Richard Roller
Posts: 78
Joined: Mon May 22, 2017 11:14 am
Location: Olathe, Ks.

Re: N34KP new weight and balance

Post by Richard Roller »

It has occurred to me that people might want to know about the negative 1.2 lb. figure in the base wt.&bal. With the fuel tank empty and in the flight posistion the a/c is nose heavy and wanted to fall onto the prop. So a bag of tools was placed on the horizontal tail directly above the tail wheel. After weighing the a/c and noting the tail weight, the bag of tools was weighed separately and the difference noted as the negative 1.2 lbs.

User avatar
Richard Roller
Posts: 78
Joined: Mon May 22, 2017 11:14 am
Location: Olathe, Ks.

Re: N34KP new weight and balance

Post by Richard Roller »

One more thought. After thinking about it I'm sure that a large part of that 20 lb weight increase is from the the counter-weighted crank that was installed after the first one broke. I'd forgotten about that and I know the weight and balance wasn't redone at that time. I don't know how much more the second crank weighs, but it does have some hefty chunks of metal added to it.

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