AERONCA Memo M-28

June - 1938                                                          M-28


                 MEMORANDUM TO OWNERS OF AERONCA AIRPLANES
            POWERED WITH ALL E-113-E-113-A-B-C-CB-CD-CDB ENGINES

SUBJECT:    Inspection of Propeller end of Crankshaft

     It has been brought to our attention that cracks have occurred in the
crankshaft at the propeller end.  These cracks originated at the rear end
of the keyway.  In an effort to avoid a complete failure of the propeller
shaft, should a crack exist, it is recommended that the propeller shaft
be inspected so that any apparent cracks may be discovered.

     This inspection should consist of removing the propeller and hub from
the crankshaft ever 100 hours.  After cleaning off the dirt and oil from the
tapered section of the crankshaft, apply a weak solution of nitric acid
(one part nitric acid to ten parts of water).  If there is a small crack,
which is not visible to the naked eye, the nitric acid solution should
remove the dirt in the crack and make it visible.  Particular attention 
should be paid to the section at the rear of the keyway.

     Before reinstalling the propeller, the nitric acid solution should be
removed from the crankshaft with water and then dried thoroughly.

     If the crankshaft show any signs of being galled from the propeller hub
it should be relapped, using a slight amount of fine grinding and lapping
compound such as No. 2A Clover Brand or equivalent.  Lap the surfaces 
together by periodically oscillating the propeller and relieving the load
to obtain a good fit.  After lapping, check the fit by using pencil lines
axially along the tapered end of the shaft.  Remount the propeller, 
oscillating it several times and remove to check fit.  When both bearing
surfaces show a good fit, apply a very small amount of lapping compound
to the small front bearing surface on the taper shank "lap" a slight
amount more, using only oil on the larger rear bearing surface.  Clean
both surfaces thoroughly before reinstalling the propeller.

     It is important that the results of each 100 hour inspection of the
crankshaft be noted in the engine log book for future reference of the
Bureau of Air Commerce Inspectors.


                                     AERONAUTICAL CORPORATION OF AMERICA
                                     LUNKEN AIRPORT --- CINCINNATI, OHIO