C170A/B aileron mass balance weights

[cgoaw]

It appears that both models(A and B) were delivered with 2.94 aileron mass balance weights. But some A models were delivered with 1.75 lb mass balance weights. Can the lower weight ones be used on the B model? And also, does the C172 have the same weights that can be used on the 170?

Thanks.

[n2582d]

Yes, it is surprising to me that the ailerons could be balanced with as much as 1.2 lbs. difference in weight. My guess is they used different criteria for their balance limits prior to 1952. Koop says he used over 3.25 lbs. to get his ailerons balanced. The aileron part numbers for the C-170A and C-170B are identical. The aileron balance weight for the 170A, p/n 0523815, has been superseded to p/n 0724115-2. The 170B originally had an aileron balance weight p/n of 0721109 which has also been superseded to the same p/n as on the 170A -- p/n 0724115-2. This same p/n is used at least through the 1986 C-172's. After your ailerons are primed and painted add or subtract weight in accordance with SNL 86-44. Have your engineer install the weights with soft rivets in accordance with Service Letter SE 71-27.