Aircraft
Certification Service Washington, DC U.S. Department of Transportation Federal Aviation Administration
NE-08-19
May 14, 2008
This is information only. Recommendations
aren’t mandatory.
Introduction
This Special Airworthiness Information Bulletin (SAIB) alerts you,
owners, operators, pilots, mechanics, and certificated repair stations
of concerns for potential propeller failures, aircraft
damage, and potential loss of aircraft control for certain untested propellers installed on experimental aircraft.
The FAA is concerned that builders of experimental aircraft and
experimental propeller installations do not always consider the
consequences of using an untested/ uncertificated propeller and engine
combination. One example of an inappropriate propeller installation
application is the use of Hartzell ( )8468( )* series blades installed
on Lycoming ( )( )-360 series engines. There may be other inappropriate
propeller installations. Consult the appropriate propeller manufacturer
for installation data to help ensure continued airworthiness.
The FAA acknowledges that the aircraft builder has the ultimate
responsibility for the parts/components used on their experimental
aircraft. The builder of the propeller assembly is often a propeller
repair station who might be unaware of the consequences of using
untested/ uncertified propeller assemblies on a specific engine. To the
extent that the propeller shop may be knowledgeable of such matters,
they also share some responsibility in notifying the experimental
aircraft builder of the potential consequences of using untested/
uncertified propeller installations.
Background
There were two accidents resulting from propeller blade failures on
experimental aircraft using Hartzell ( )8468( )* series blades
installed on Lycoming ( )( )-360 series engines. This blade design uses
a thinner airfoil than that used on other Lycoming 360 applications.
Also, the accident-related blades incorporated a modification that
reduced the blade diameter to less than other approved designs. These
differences result in exposure to high vibratory stress loadings that
exceed the structural levels allowed for safe operation. In both
accidents, the high propeller blade vibratory stress loading is
considered a contributing factor in the failures. These accidents show
that specific engine and propeller combinations are an important design
consideration that requires careful research regardless of the
propeller manufacturer.
Builders of experimental aircraft are permitted to use experimental
propellers. However, certain propellers, even those with type
certificates, might not be suitable for use on certain engines. If
combined, there is the potential for an unsafe condition to exist.
Propeller Repair Stations have, on occasion, been reported to assemble
an experimental propeller using propeller blades retired from use on
certificated aircraft for being undersize in width, thickness, or
diameter. Such a propeller enables the builder of an experimental
aircraft to reduce costs, but could result in an unsafe application
that does not meet any approved or tested engine and propeller
combination.
* There are numerous variations in Hartzell ( )8468( ) series propeller blades such as: F8468A-6R, F8468-2, FC8468-6R, etc.
Recommendations
Propeller Repair Stations –
If asked to build an
experimental propeller, confirm the specific engine model being used
and only select a propeller that is known to be
vibrationally/structurally compatible with that engine. As necessary,
contact the appropriate propeller manufacturer for assistance in making
this selection.
Advise the customer of the
experimental, untested nature of the propeller installation and its
potential airworthiness consequences.
Do not install Hartzell 8468 series blades on a propeller for use on a Lycoming 360 series engine.
Experimental Aircraft Builders –
Wherever possible, always use an FAA-approved or propeller manufacturer-recommended engine and propeller combination.
If either an engine or
propeller does not meet FAA type design, seek a recommendation from the
kit provider (if applicable), the propeller manufacturer, or the engine
manufacturer, to obtain the most suitable application possible to avoid
an unsafe condition. Builders should make informed decisions concerning
their engine and propeller installation combinations.
Do not use a Hartzell 8468 series blade on a propeller for use on a Lycoming 360 series engine.
There may be other engine
and propeller combinations that result in unsafe installations. Contact
the appropriate propeller manufacturer for additional guidance.
Experimental Aircraft Owners –
If you are unfamiliar with
the propeller on your aircraft, perform the research necessary to
ensure the propeller/engine combination meets an approved design. If
you do not do the research, consider changing the propeller, or at
least become aware of the increased risk and the consequences of a
propeller failure.
If you have an aircraft with
a Lycoming 360 series engine, check the propeller to determine if
Hartzell 8468 series blades are installed. If they are installed,
replace them before further flight.
For Further Information Contact
Jay Turnberg, Propeller Specialist, Standards Staff, FAA, Engine
and Propeller Directorate; 12 New England Executive Park, Burlington,
MA 01803; e-mail: jay.turnberg@faa.gov; phone: (781) 238-7116; fax:
(781) 238-7199.
For Hamilton Sundstrand, Avia, Dowty, Hoffmann, or MT Propellers:
Terry Fahr, Aerospace Engineer, Boston Aircraft Certification Office,
FAA, 12 New England Executive Park, Burlington, MA 01803; e-mail:
terry.fahr@faa.gov; phone: (781) 238-7158; fax:
(781) 238-7170.
For Hartzell Propellers:
Tim Smyth, Aerospace Engineer, Chicago Aircraft Certification Office,
FAA, Propulsion Branch, 2300 East Devon Avenue, Des Plaines, IL 60018;
e-mail: timothy.smyth@faa.gov; phone: (847) 294-7132, fax: (847)
294-7834.
For Sensenich Propellers:
James Delisio, Aerospace Engineer, New York Aircraft Certification
Office, FAA, Propulsion Branch, 1600 Stewart Avenue, Suite 410,
Westbury, NY 11590; e-mail: james.delisio@faa.gov;
phone: (516) 228-7321; fax: (516) 794-5531.