> Propeller Conversions
Hartzell has been in business since 1917 when it built its first walnut props for the Wright Brothers in nearby Dayton,
Ohio and for Glen Curtiss' brand new Jenny. From that auspicious beginning, Hartzell has set time to altitude records
with the Army Air Force Scouts in the 1920s, barnstormed with the Wacos in the 1930s, developed general aviation's
first cntrollable pitch props for Cessn's 310, as well as the industry's first reversing propeller for Beech's turboprop
Through its Top Prop conversion program, Hartzell is providing a way for the pilots of a large portion of the existing
general aviation fleet to significantly improve the performance of their aircraft. To date, literally thousands of pilots
have converted with Hartzell props …all of which include the ironclad Plus Three warranty. It provides pilots with an
industry leading three years or 1,000 hours of total coverage. Hartzell Top Prop pilots also enjoy the longest TBO
standards in the industry (2,400 hours/6 years). Kits for more than 50 different aircraft makes and models are
currently available with more on the horizon.
MORE BLADES CAN EQUAL MORE PERFORMANCE
Right now pilots like you are discovering that a propeller conversion is one of the most significant improvements that
can be made to their aircraft. Refinement of propeller design directly addresses takeoff distance, climb, noise level,
and vibration. And on certain aircraft a switch to a prop with more blades will even provide greater flexibility in
selecting effective power settings as well as improved drag characteristics that are helpful for fast desents.
Maximizing the efficiency of aircraft with the lower horsepower and higher RPMs of smaller piston engines would
usually call for fewer blades. Unfortunately, two-bladed props have some inherent disadvantages. For starters, they're
louder. Propellers are the source of most of the noise generated by an aircraft. And two-bladers are often larger in
diameter, resulting in nearly supersonic tip speeds…and dramatically increased noise levels. Refinement of propeller
airfoil design can also reduce noise levels to a more comfortable level.
Two-bladers are also more prone to vibration. Two blades create two large pulses of thrust compared to a three-
blader's three smaller, smoother pulses. Two-blades often provide less ground tip clearance which leads to more
nicks and scratches on the blades. And as the size of the engine increases…requiring more blade area to effectively
absorb the increased power…two-bladed props must become unconventionally long and heavy.
THE PROPELLER THAT'S BEST FOR YOUR AIRCRAFT DEPENDS ON THE TYPE OF PERFORMANCE YOU ARE LOOKING FOR
In long-range applications like the nonstop around the world flight of Voyager, noise, vibration, acceleration, climb and
ground tip clearance were not flight priorities. Extreme cruise efficiency with minimal weight were. The result of these
priorities was a two-bladed Hartzell design that helped to maximize endurance. For very high altitude applications like
the world record holding flight of the Boeing Condor, very large but extremely lightweight Hartzell composite three-
bladed props were utilized to generate thrust in the thin air of 66,000 plus feet.
Applications involving most Beechcraft, Cessna, Mooney, Piper and other general aviation aircraft are quite different.
Here performance in every category is desirable and all of these factors must be part of the propeller's design. With
the help of today's powerful computers and the experience of more than 300 proven Hartzell propeller blade designs
(more than any other manufacturer in the world), it is possible to take the inherent advantages of a prop with more
blades…less noise and vibration plus greater acceleration and climb…and often match or improve cruise performance,
which used to be the privileged domain of props with fewer blades.
WHAT'S INCLUDED IN THE HARTZELL PROPELLER CONVERSION KIT?
In addition to the propeller and spinner hardware, the Supplemental Type Certificate (STC) kit contains several
documents with which you should become familiar. These include: the STC document, STC installation instructions,
propeller owner's manual, Airplane Flight Manual Supplement and warranty card. The STC document makes it legal
to install your new propeller on your airplane. The STC document should be kept with the permanent records for the
aircraft. The STC installation instructions provide the information required to install the propeller, including any
required placards or accessory changes. The enclosed propeller owner's manual also provides installation guidance.
Be sure to mail in the revision service card included with the owner's manual so that you will receive manual updates.
The Airplane Flight Manual Supplement (AFMS) must be kept with the Airplane Flight Manual and must be available
to the pilot. The AFMS will list any changes to the Airplane Flight Manual, which are caused by the installation of the
STC. Any item not called out in the AFMS remains as specified in the original flight manual.
The warranty card is also enclosed in the kit. Top Prop conversions are covered by the Plus Three warranty for a total
of three years or 1,000 flight hours. Other warranty details are the same as the standard warranty, which is described
in the warranty card included in the STC kit. The warranty card should be filled out, a copy made for your records,
and the original card sent in to Hartzell. While the prop is warranted against defects in materials and workmanship as
described above, if you are dissatisfied with the operation of the propeller on your airplane for any reason, contact
Hartzell within 90 days or 10 flight hours after installation.
The Top Prop propeller conversions were developed to provide performance enhancements, improved comfort and
appearance, and reduced maintenance for your airplane. If you are not satisfied with your new Top Prop conversion,
let Hartzell know. They want happy customers. Recommended routine propeller maintenance is described in the
owner's manual, which is included with your STC kit. Familiarizing yourself with the information contained in the
manual will maximize the service life and reliability of your new propeller.
TOP PROP COMPATIBILITY WITH OTHER STC'S
Occasionally, Hartzell gets questions reguarding installation of a Top Prop STC in conjunction with another STC.
There are many STCs available today for a wide variety of aircraft equipment. The responsibility for determining that
the STC is compatible with previously installed modifications on a particular airplane rests with the installer (the
mechanic with Inspection Authorization who completes the installation). An FAA statement to this effect is usually
given in the STC document under the Limitations and Conditions section.
Generally speaking, the installation of STC'd interior equipment is considered to be compatible with the installation
of a Top Prop conversion kit. Examples of such equipment include: electronic navigation equipment, engine
analyzers and fuel totalizers. Airframe modifications are also generally compatible with the installation of a Top Prop
conversion kit. Examples of such equipment include: control surface gap seal kits, vortex generator kits, wing tip
A previously installed STC which approves engine modifications that change the power or vibrational characteristics of
the engine is generally not compatible with a Top Prop propeller conversion. Examples of engine modifications not
compatible with a Top Prop conversion include: installation of a turbocharger, higher compression pistons, engine
substitutions. Modifiers who offer engine conversions or modifications sometimes work with Hartzell to have a Top
Prop propeller approved with their engine modification STC. Contact the holder of the powerplant STC to see if a
particular Top Prop propeller model is listed on the engine modification STC. If there is any question whether an
STC is compatible with your modified airplane, consult your local FAA Flight Standards Office. They are
the final authority.
People often ask about the performance improvements, which they will receive from their new propeller. Aircraft in the
general aviation fleet today vary widely in condition, making it difficult to make blanket statements about performance
improvements. Variables include: engine wear, rigging differences, minor airframe damage, previous modifications
and poorly fitting components such as cowlings, doors, etc. STC performance testing is generally done using
unmodified aircraft, which are in very "clean" condition. Test results must be at least as good as the original
propeller to obtain the STC from the FAA. Many STCs are obtained on an "as good or better" performance basis.
This means that while the performance benefits are often gained, many times credit is not taken for the improvement
to avoid having to prepare a complete set of new performance data for the airplane. In these cases, the AFMS will
often state "No Change" under the performance section.
From time to time, owners wish to performance test their airplanes with the new Top Prop installed. While this can
be an enjoyable and educational activity, several factors should be considered. To obain accurate data, consistent
power settings, RPM, weight and C.G. values must be used for all tests. Proper data corrections must also be
applied to correct for temperature, weight and other variations, which occur during the test program. If the data are to
be compared to the original handbook figures, all of the instruments used in the test must also be calibrated. In short,
without proper test techniques, calibations and data corrections applied, informal performance tests can lead to
Hartzell sometimes gets questions regarding cabin vibration, which is thought to be caused by the propeller. Before
flying a new propeller installation, the following items should be checked: (1) Verify propeller tracking and proper
mating of the propeller/engine flange; (2) Verify that items such as control surfaces, cowl flaps, exhaust system and
landing gear doors are free of excess play; and (3) Check for poor isolation of engine controls and lines. Sometimes
these items are disturbed when the propeller is installed in conjunction with other maintenance.
If vibration is experienced during initial flights with a newly installed propeller, the following items should be
accomplished: (1) Perform propeller dynamic balancing (strongly recommended for all propeller installations); (2)
Change propeller indexing (for propellers having more than one mounting position); (3) Check engine shock mounts
for deterioration; and (4) If vibration persists, stop troubleshooting and contact the Hartzell Top Prop office. It is
recommended that the original propeller be installed (and flown) after an engine overhaul to determine that the engine
vibration levels in the cabin are acceptable before installing a new propeller. If the engine and propeller are changed
at the same time, it will be difficult to determine the source of any changes in vibration levels.
All Top Prop STCs purchased after January 1, 1997 have the STC document copied on watermark paper with a raised
Hartzell stamp. These features denote an authentic STC document and are intended to prevent unauthorized
reproduction. The STC document is truly "worth more than the paper it is printed on." Obtaining an STC to install
a new propeller can cost anywhere from ten thousand to a quarter-million dollars depending on the complexity of the
aircraft and installation. The STC paperwork is an important legal document, which should be treated with the same
care as an aircraft or engine logbook. Verification of all aircraft documents, including STCs, should be a part of every
aircraft pre-purchase inspection.
In the case of lost documents, replacement copies are available (for a fee) for aircraft which originally had a Top Prop
kit installed. Before calling, locate your copy of the warranty card or be prepared to supply the aircraft serial number,
propeller serial number, and aircraft N-number in order for Hartzell to issue new copies of the documents. The STC
documentation packages are not for sale separate from the propeller hardware. The Top Prop program is intended to
provide owners with new propellers. Use of the Top Prop STC documents with used propellers is not authorized.
Each Top Prop STC kit is licensed for a particular aircraft (registration number and serial number). The STC
documentation must remain with the aircraft for which it was originally purchased.
Obtaining approval to install a Top Prop STC outside of the U.S. is considered to be the responsibility of the installer
(owner, mechanic, or inspector). However, Hartzell has a list available for their foreign customers, which lists all of
the countries in which the STC has been previously approved or sold. Non-U.S. customers might also check with
their national aviation authorities to see if a list of approved modifications is available for their country. If a Top Prop
STC is not currently approved in a particular country, application for approval usually must be made. Many countries
accept the FAA STC outright, while others require some level of validation. The validation process often takes several
months and should be initiated before purchase and installation of the propeller conversion. Contact the Hartzell Top
Prop office as soon as possible if approval in a non-U.S. country is required.