DOFF10300E - Hartzell Engine Technologies Alternator 28V/38A

DOFF10300E – Hartzell Engine Tech 28V, 38A Gear-Driven Alternator

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Overview

The DOFF10300E from Hartzell Engine Technologies is a high-quality, FAA-PMA certified, gear-driven alternator designed as a direct replacement for the original equipment Prestolite alternators on a wide range of Lycoming engines. This is a flight-critical component that serves as the primary source of electrical power for an aircraft's 28-volt DC system. With a continuous output rating of 38 amps, it is an ideal solution for light aircraft with basic electrical and avionics needs.

Unlike belt-driven units, the DOFF10300E is a direct-drive alternator that mounts directly to the engine's accessory case and is driven by the internal gear train. This design eliminates the maintenance and failure points associated with drive belts and pulleys. As a new-manufacture unit from a leading OEM of engine components, the Hartzell DOFF10300E offers a significant upgrade in reliability and performance over aging, overhauled legacy alternators.

Key Features

• Genuine Hartzell Engine Technologies Part: Manufactured and tested by a leading OEM of engine accessories, ensuring the highest standards of quality and reliability.

• FAA-PMA Certified: A fully certified, airworthy replacement part, providing a direct-fit, form, and function equivalent for specified original equipment alternators.

• 28-Volt, 38-Amp Continuous Output: Provides ample, stable electrical power for the typical flight and avionics loads of light general aviation aircraft.

• Gear-Driven (Direct-Drive) Design: Mounts directly to the engine accessory pad, eliminating the need for a drive belt and offering a robust, direct mechanical connection.

• Direct Replacement for Prestolite Models: Engineered as a modern, reliable replacement for the original Prestolite alternators installed on many Lycoming O-235 and O-320 engines.

• Lightweight and Compact Design: Offers a powerful output in a compact and lightweight package, minimizing impact on aircraft weight and balance.

Technical Specifications

• Part Number: DOFF10300E

• Component Type: Engine-Driven Alternator

• OEM Manufacturer: Hartzell Engine Technologies

• Voltage Rating: 28 VDC (Nominal)

• Maximum Continuous Amperage: 38 Amps

• Drive Type: Gear-Driven (Direct-Drive), Lycoming-style drive

• Engine Application (Typical): Lycoming O-235 and O-320 series engines.

• Governing Specification: FAA-PMA Documentation; Hartzell Engine Technologies engineering drawings.

Aircraft Compatibility

This alternator is a specified replacement part for a wide range of popular general aviation aircraft powered by compatible Lycoming engines.

• Primary Aircraft Platforms:

  • Cessna 152

  • Cessna 172 (models with O-320)

  • Piper PA-28-140 Cherokee

  • Grumman American AA-1 Trainer/Yankee

  • Grumman American AA-5 Traveler/Cheetah

  • Various experimental aircraft using these engine models.

Note: Verification of applicability is the absolute responsibility of the installer. The Hartzell Engine Technologies application guide and the aircraft's Illustrated Parts Catalog (IPC) are the final authorities for confirming part number eligibility.

Applications

• Sole Application: To serve as the primary source of 28VDC electrical power for the aircraft's avionics, lighting, and other electrical systems, and for charging the aircraft's battery.

Why Choose DOFF10300E?

The aircraft's electrical system is a safety-of-flight system. The DOFF10300E offers the opportunity to replace an aging, potentially unreliable original alternator with a brand-new, factory-tested unit from a trusted OEM. This significantly reduces the risk of an in-flight alternator failure, which would necessitate an immediate reliance on the time-limited battery and could create an emergency situation, especially at night or in IMC. For owners of legacy aircraft, this alternator represents a powerful and cost-effective upgrade to the reliability of a critical system.

The DOFF10300E alternator operates on the principle of electromagnetic induction, utilizing a Lundell or "claw-pole" rotor design for its compact efficiency. A single field coil, energized by a controlled DC current from the external voltage regulator, is housed within the rotor. This coil magnetizes two interlocking soft iron cores, whose "claws" are shaped and interdigitated to present multiple alternating North and South magnetic poles to the stationary stator windings. As the engine's accessory gear train spins this rotor, the rapidly changing magnetic flux that cuts across the three-phase stator windings induces an alternating current (AC) voltage in them, according to Faraday's Law of Induction (Vind​=−NdtdΦB​​). This three-phase AC output is then passed through a solid-state, full-wave rectifier bridge (a set of six diodes) which converts it to the direct current (DC) required by the aircraft's electrical bus.

Note: This is a flight-critical component. Installation must be performed by a certified A&P mechanic in strict accordance with the engine maintenance manual. Correct gear backlash, mounting torque, and electrical connections are critical for safe and reliable operation. This alternator requires a compatible, external voltage regulator (not included) for proper function. After installation, a full electrical system functional check must be performed.

Documentation

Installation and application data are available from Hartzell Engine Technologies. All installation and maintenance procedures must be performed in accordance with the official Lycoming engine overhaul and maintenance manuals.