Regulatory Brief - Hartzell Propeller AD

Regulatory Brief

Hartzell Propeller AD

The issue

On September 9, 2005, the FAA issued a final rule airworthiness directive (AD) that requires the inspection of the propeller blades and other critical propeller parts. The AD resulted from two incidents where "Z-shank" blades failed and separated. Teardown inspections detected corrosion in the blade bores. The AD affects some 1,200 airplanes in the U.S. registry that may include the Cessna 172, 175, 190, 195, and 421; the Piper PA-23, PA-24, and PA-25; and several other models from Beechcraft, Aero Commander, Grumman, and Mooney.

The importance to our members

Undetected corrosion and mechanical damage in the propeller assembly could result in propeller blade failure and subsequent loss of aircraft control. To mitigate this possibility, the FAA issued AD 2005-18-12, which requires inspection of the propeller assembly for corrosion and mechanical damage if the propeller assembly has more than 10 years time-since-overhaul (TSO) on the effective date of this AD, or if the TSO is unknown, or if the propeller has not complied with Hartzell Service Bulletin (SB) No. HC-SB-61-136, Revision I, H, or G. The FAA has established a compliance schedule for completing the inspections, ranging from 12 to 36 months.

The AD does not require further action on the aircraft owner if the propeller TSO is 10 years or less on the AD's effective date, or the propeller assembly was inspected in accordance with one of the previously referenced Hartzell SBs.

Compliance times for one-time inspection:

If the TSO of the propeller assembly on the effective date of this AD is more than 25 years or the TSO is not known, then perform the inspection within 12 months after the effective date of this AD.
If the TSO of the propeller assembly on the effective date of this AD is 21 to 25 years, then perform the inspection within 18 months after the effective date of this AD.
If the TSO of the propeller assembly on the effective date of this AD is 16 to 20 years, then perform the inspection within 24 months after the effective date of this AD.
If the TSO of the propeller assembly on the effective date of this AD is 11 to 15 years, then perform the inspection within 36 months after the effective date of this AD.
The one-time inspection consists of the following steps:
1. Disassemble and clean the propeller assembly.
2. Perform visual and nondestructive inspections of propeller components for cracks, corrosion or pits, nicks, scratches, wear, blade minimum dimensions, and damage in the blade balance hole.
3. Inspect and rework the propeller blade bore. Use 3.A. of the Accomplishment instructions of Hartzell SB No. HC-SB-61-136, Revision I, dated April 26, 2003.
4. Repair and replace with serviceable parts, as necessary.
5. Reassemble and test.

Inspection results must be reported within 15 working days to the Manager of the Chicago Aircraft Certification Office, FAA, Small Airplane Directorate, 2300 East Devon Ave, Des Plaines, IL 60018.
The FAA estimates that it will cost about $1,750 per propeller assembly to perform the required AD actions.
The AD goes into effect on October 14, 2005.

AOPA position

AOPA agrees that, in this particular situation, the possibility for blade failure caused by corrosion in the blade bore, and possible subsequent in-flight propeller blade separation, warrants airworthiness action. The AD is reasonable in that it only requires a one-time inspection ranging from 12 to 36 months from the AD's effective date to comply. Affected owners may request an alternate means of compliance from the FAA.

Status

On September 9, 2005, the FAA issued final rule AD 2005-18-12