Aircraft Alternator
Maintenance Manual
24-30-01
ES1031
Page: 3-8 Rev.
B: 20 Apr. 2022
© 2022 - Hartzell Engine Technologies - All rights reserved
3.3 Alternator Drive Coupling Troubleshooting
A. The alternator drive coupling is provided by the airframe or engine manufacturer and those
manufacturers normally issue instructions regarding maintenance and installation. The alternator drive
coupling is fundamental to the operation of Hartzell Engine Technologies (HET) gear driven alternator.
Observe the following information when installing and using the drive coupling:
B. If an alternator is determined to be at fault, note that the gear coupling is considered a part of the engine
installation and should be removed from the alternator and properly installed on the replacement unit.
(1) Check for any and all service information from the engine, airframe and the drive coupling
manufacturer concerning the installation, inspection, and replacement of the drive coupling.
(2) Check the general condition of the drive coupling (this requires removal of the alternator).
(3) Check the shaft nut and cotter pin for damage. (Damage to these parts will indicate interference with
internal engine parts.) If damaged, determine cause and correct the issue.
(4) Using the manufacturer’s service information, check the condition of the gear teeth and the elastomer
insert. If damaged, replace or overhaul the drive coupling.
(5) Whenever the alternator is overhauled, HET recommends that the drive coupling be replaced. If
the alternator cannot be overhauled or repaired and is being replaced, the coupling should also be
replaced.
(6) To further aid inspection, Continental Motors includes drive coupling service information in the
appropriate engine manuals and also in service bulletins. (Refer to CMI SB11-3 and/or SB95-3B for
drive coupling service information.)
3.4 Alternator Belt Troubleshooting
A.
Although the alternator belt is provided by the airframe or engine manufacturer and those manufacturers
normally issue manuals or instructions regarding their maintenance, the belt is fundamental to the operation
of Hartzell Engine Technologies LLC (HET) alternator. As such, some general troubleshooting regarding
the belt is offered here to prevent mis-diagnosis of what may seem to be an alternator fault.
B. Hartzell Engine Technologies new or overhauled alternators using belt drives are designed for two basic
types of belts via custom pulley installations. The most common type is the single smooth V belt (large
and small width) and the Poly-V belt type which has multi-V groves but is nearly flat. The basic function of
these belts (either type) is to transfer rotational energy produced by the engine to various accessories that
are needed for the aircraft.
C. The belt system or “drive” may be simple, running from the engine drive sheave to an alternator or it might
be complex in not only running the alternator, but including the A/C compressor, hydraulic pump, or idler
pulleys. Belt drives are efficient and safe. However, the more complex, the more difficult it is to align the
“drive”. This troubleshooting will provide insight into both sound and visual inspection practices to identify a
belt condition before moving on to the alternator or other component.
D. If an alternator is determined to be at fault, note that HET sells alternators with or without a pulley due
to the desire of engine and airframe manufacturers to sometimes use their own custom pulley and belt
arrangements. The HET alternator designated ES10024B-1 is delivered without a pulley. Other HET
ES10024B series alternators are delivered with varied size and type pulleys.
