Category: navion, Hartzell, propeller, placard
Applicability: All model B aircraft equipped with Hartzell HC-12 x 20-8C19333C-0 propellers.
Supersedes: n/a
Compliance: Not later than March 15, 1953
Procedure: Vibration tests conducted subsequent to the initial tests of the Hartzell HC-12 x 20-8C19333C-O propeller installed on the Lycoming GO- 435 engine revealed vibration characteristics of a hazardous nature. Therefore, to prevent possible blade cracks and/or failures, the existing r.p.m. restriction placard should be revised as follows:
"Avoid continuous ground operation between 1675 and 2150 engine r.p.m."
Notes: none
AD-53-03-01