Presented to: By: Date: Federal Aviation Administration Airworthiness and/or Operations Potential for Propeller failure 1

Federal Aviation Administration 2 Description of Airworthiness Concern On June 18, 2012, a Piper PA , had a liberation of about 6” of the tip of one propeller blade. The event occurred at Peoria Airport in Peoria, IL The propeller is a 2-bladed aluminum propeller.

Federal Aviation Administration Event Aircraft Just After Landing 3

Federal Aviation Administration 4 Leading Edge Damage –The propeller leading edge shows a significant amount of dents and scrapes from impact with small rocks (probably flown out of a gravel strip).

Federal Aviation Administration 5 Fatigue of Cracked Propeller Blade There was significant fatigue evident (about 75% of blade showed fatigue damage), and with only a few hundred hours on the propeller, this leads us to believe the propeller was being operated in a resonant mode.

Federal Aviation Administration 6 Fatigue of Cracked Propeller Blade Dark grey is failure in overload Shiny silver is cyclic fatigue Dull grey is crack initiation site

Federal Aviation Administration 7 Cause of Fatigue There is a known resonant mode with this propeller/engine combination that has it’s highest level between 2200 and 2250 RPM. –An AD had been issued, creating an operating restriction range between 2100 and 2350 RPM. –The propeller manufacturer had provided information to operators to avoid operation below 2500 RPM The president of the flying club said their pilots have been told to operate at 2500 RPM. However, it is possible they have been flying at the more traditional 2400 RPM to save fuel.

Federal Aviation Administration 8 Probable Event Scenario When tested after the event, the airplane’s tachometer was reading 80 rpm higher than actual rotational speed of the propeller. –Tachometer error discovered by NTSB. –If the pilot set the RPM to 2400, then he was probably operating in the restricted range below 2350 RPM.

Federal Aviation Administration Resonant Mode Evaluation 9

Federal Aviation Administration Why does this happen? Mechanical tachometers can loose their accuracy over time. Reports of tachometer errors of 50 rpm are common and they have been seen up to 250 rpm. When the tachometer is out of calibration, you can inadvertently operate in a restricted range, subjecting the propeller to vibration that will cause damage. 10

Federal Aviation Administration What can you do? Check with the propeller manufacturer regarding restricted ranges for your propeller/engine combination Verify the proper RPM restrictions are accurately marked Verify the accuracy of the tachometer readings – and repeat at regular intervals Be vigilant in checking the propeller for damage that can initiate a crack 11

Federal Aviation Administration For more information…… FAA Special Airworthiness Information Bulletin NE-08-21, issued May 14, 2008 FAA Advisory Circular 20-37E, Aircraft Propeller Maintenance, dated September 9,

Federal Aviation Administration Taking these actions will help to ensure that this does not happen to you! 13

Federal Aviation Administration Updated FAA Contact Information For General Propeller issues – Jay Turnberg, Propeller Specialist, Engine and Propeller Directorate, For Hamilton Sunstrand – Michael Schwetz, Boston ACO, For Hartzell Propellers – Chris Richards, Chicago ACO, For Sensenich Propellers (wood) – Gary Wechsler, Atlanta ACO, 14

Federal Aviation Administration Updated FAA Contact Information For Sensenich Propellers (metal) – Ron Segall, New York ACO, For McCauley Propellers – Steven Litke, Wichita ACO, For Aeroproducts/Pacific – Margaret Langsted, Seattle ACO, For Tarver – Jonathan Oxman, Los Angeles ACO, 15