Airworthiness Directive · Amendment 39-11592 · Hoffmann Propeller Co. HO27( ) and HO4/27 Series Propellers
Hoffmann Propeller Co. HO27( ) and HO4/27 Series Propellers
Hoffmann Propeller Co. HO27() and HO4/27 series propellers, with propeller mounting bolts, part number (P/N) FP20-147 () () (), installed. These propellers are installed on but not limited to Textron Lycoming O-360 series and O-540 series, and Teledyne Continental Motors O-470 series reciprocating engine powered airplanes manufactured by Aeronca, Bellanca, Cessna, DeHavilland, Piper, Socata, Rallye, Stinson, and Varga.
Note 1: The parentheses that appear in the propeller models indicate the presence or absence of additional letter(s) which vary the basic propeller hub model designation. This airworthiness directive (AD) is applicable regardless of whether these letters are present or absent on the propeller hub model designation.
Note 2: This AD applies to each propeller identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For propellers that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (b) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.
This amendment adopts a new airworthiness directive (AD) that is applicable to Hoffmann Propeller Co. HO27( ) and HO4/27 series propellers. This action requires installing improved propeller mounting bolts to a higher torque value, operating the airplane for one flight, checking the torque, and retorquing, as required, to the correct torque value. This amendment is prompted by reports of insufficient torque of propeller mounting bolts due to operating conditions, loads, and environmental conditions such as humidity and temperature. The actions specified in this AD are intended to prevent propeller mounting bolt failure, which could result in propeller separation and loss of control of the airplane.
To prevent propeller mounting bolt failure, which could result in propeller separation and loss of control of the airplane, accomplish the following:
(a) Within 10 hours time-in-service (TIS), or 7 days after the effective date of this AD, whichever occurs first, remove from service propeller mounting bolts, P/N FP20-147
()()(), and install improved propeller mounting bolts, P/N FP20-147 ()()()V. Make sure the new bolts have the “V” marking at the end of the P/N.
(b) Torque all six propeller mounting bolts to 24.3 to 25.8 foot-pounds or 33 to 35 Newton-meters.
Note 3: Further information on propeller mounting bolt installation and torquing procedures can be found in Hoffmann Propeller Company Owner Manuals E0110.74 or 0207.71, and on the sticker on the propeller.
(c) After installation of new mounting bolts, operate the airplane for no more than 2 hours TIS, check torque and retorque, as required, to 24.3 to 25.8 foot-pounds or 33 to 35 Newton-meters.
The aircraft, engines and makers this AD names, by the model designations in its text. A model listed here may still be outside the AD's serial ranges.
Propellers
