DOFF10300ER - Hartzell Alternator 28 Volt 38 Amp

DOFF10300ER – Hartzell Engine Technologies 28 Volt 38 Amp Alternator

Available now on the Airparts.aero Marketplace.

Overview

The Hartzell Engine Technologies DOFF10300ER is a modern, lightweight, gear-driven alternator designed as a direct replacement for the heavy, legacy DC generators on a range of Continental IO-520 and IO-550 series engines. This is a flight-critical component that serves as the primary source of electrical power for the entire aircraft, responsible for running all avionics and lighting systems while simultaneously charging the battery. As an FAA-PMA certified component from a leading OEM, this alternator represents a significant upgrade in reliability, efficiency, and performance over the older generator technology.

Unlike a DC generator that is inefficient at low engine speeds, this alternator is engineered to produce significant charging output even at idle and taxi RPMs, reducing battery discharge during ground operations. It utilizes a robust, solid-state internal rectifier to convert AC power to DC, eliminating the heavy, maintenance-intensive commutators found in generators. Housed in a lightweight, blast-cooled aluminum case, the DOFF10300ER provides a powerful 38 amps of continuous output in a compact, reliable package, making it the premier choice for upgrading or replacing the electrical generating system on compatible aircraft.

Key Features

• Genuine Hartzell / FAA-PMA Certified: A fully certified, airworthy component from a world leader in engine accessories, ensuring the highest standards of quality and reliability.

• Modern Alternator Technology: Vastly superior to the legacy DC generators it replaces, offering higher efficiency, lower weight, and dramatically improved performance at low engine RPM.

• Lightweight Design: Offers a significant weight savings over older generator models, contributing to an increase in the aircraft's useful load.

• High Efficiency at Low RPM: Begins producing significant electrical power at engine idle, reducing battery drain during taxi and ground operations.

• Solid-State Rectification: Utilizes a highly reliable, integrated six-diode solid-state rectifier bridge to convert AC to DC power, eliminating the high-wear brushes and commutators of a generator.

• Blast-Cooled for Durability: Features a purpose-built housing with an integrated fan and ports for blast tube cooling, ensuring proper operating temperatures and a long service life.

Technical Specifications

• Part Number: DOFF10300ER

• Component Type: Engine-Driven Alternator

• OEM Manufacturer: Hartzell Engine Technologies

• Voltage Rating: 28 VDC

• Maximum Continuous Output: 38 Amps

• Drive Type: Gear Driven (Continental Accessory Pad)

• Cooling: Forced Air (Blast Tube) Cooling

• Rectification: Internal, Solid-State, 6-Diode Bridge

Aircraft Compatibility

This alternator is designed as a direct replacement for the original generator or alternator on numerous aircraft powered by large-displacement Continental engines, including:

• Engine Models: Continental IO-520, IO-550, TSIO-520 series and others.

• Common Aircraft Applications: Beechcraft Bonanza, Beechcraft Baron, and some Cessna models using these engines.

Note: This is a flight-critical electrical system component. The specific aircraft and engine Illustrated Parts Catalog (IPC) and STC data are the final and absolute authorities for determining part applicability.

Applications

• Primary Electrical Power Generation: Supplies all the electrical power required to operate the aircraft's systems in flight, including avionics, lighting, flight instruments, and autopilot.

• Battery Charging: Provides the necessary current to maintain the aircraft's battery at a full state of charge.

• Generator-to-Alternator Upgrade: The premier choice for STC'd upgrades from older, less reliable DC generator systems.

Why Choose DOFF10300ER?

The aircraft's electrical generating system is a no-fail system. The Hartzell DOFF10300ER offers a massive leap forward in reliability and performance compared to the generators it replaces. A generator's inability to produce power at low RPM leads to chronic battery issues and the risk of a dead battery for an engine restart. The heavy-wear commutator and brushes of a generator are a constant source of maintenance and potential failure. This modern, lightweight alternator from Hartzell is a "fit-and-forget" solution, providing ample, stable power from engine start to shutdown. For a safe and reliable electrical system, there is no better choice than this OEM-quality, certified alternator.

The core engineering principle that allows the DOFF10300ER alternator to be so effective is its closed-loop feedback control system, executed in partnership with an external voltage regulator. The alternator generates three-phase AC power via electromagnetic induction, where the output voltage is directly proportional to the rotor's speed and the strength of its magnetic field. The voltage regulator continuously senses the DC bus voltage. If the voltage drops due to increased electrical load or decreased engine RPM, the regulator instantly increases the low-amperage "field current" sent to the alternator's rotating electromagnet via a set of low-wear brushes and slip rings. This strengthened magnetic field causes the alternator to produce a higher AC voltage, which is then rectified to bring the DC bus voltage back to its target (e.g., 28.0V). This solid-state, closed-loop system reacts instantaneously to maintain a rock-solid bus voltage, protecting sensitive avionics and ensuring reliable power under all flight conditions.

Note: The DOFF10300ER is a flight-critical component. Installation must be performed by a certified A&P/IA mechanic. It must be paired with a compatible, certified voltage regulator for proper operation. All electrical connections, especially the high-current "B-lead" output, must be clean and torqued to the specified values. The installation of the cooling air duct (blast tube) is mandatory and must be correctly positioned to prevent overheating and premature failure.

Documentation

• Hartzell Engine Technologies Website: Full application charts, cross-reference guides, and technical documents for Hartzell alternators are publicly available for download from the official HET website.

 
Part number:   DOFF10300ER
Alternate PN:   ES4004, 633962
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