A Deep Dive into How Aircraft Starter Generators Work

Many modern aircraft rely on an array of complex electrical systems to support functions ranging from basic cabin lighting to the operation of critical avionics. While many of these systems are electronically controlled, electromechanical devices like aircraft starter generators remain essential for enabling core mechanical operations. This blog will examine the inner workings of aircraft starter generators, outlining their dual-purpose functionality, their role within integrated power systems, and key troubleshooting considerations.

What Is a Starter Generator?

A starter generator is an electromechanical device designed to tackle two functions: initiating engine rotation during startup and producing electrical power once the engine reaches self-sustaining operation. These units are typically mounted on the engine’s accessory gearbox and are directly driven by the powerplant. Their design also often prioritizes compact integration, which can be advantageous for integration into various high-performance aircraft platforms.

How the Starting Mode of Generators Works

During engine start-up, a starter generator operates in motor mode, where it draws electrical energy from an aircraft’s onboard battery or an external ground power unit to produce mechanical rotation. This rotation enables an engine to reach the threshold speed required for sustained combustion. Once the engine attains a specified RPM, the system automatically disengages motor functionality, preparing to switch to power generation.

How the Power Generating Mode of Generators Works

After startup, the same unit transitions to power generation mode, harnessing mechanical energy from the running engine to produce electrical output. This electrical power is then used to operate essential aircraft systems, such as avionics, cockpit displays, lighting, and communication equipment.

What Are Common Types and Configurations of Starter Generators?

Generally speaking, one will want to use different starter generators based on the aircraft class, onboard power demands, and operational performance criteria in question. Typical variants include:

• Brush-Type Starter Generators: These units employ carbon brushes to ensure continuous electrical contact, and they typically demand more frequent servicing as the brushes gradually degrade with use.
• Brushless Starter Generators: These systems use solid-state electronic components in place of carbon brushes to regulate excitation and maintain a set electrical output.
• AC Starter Generators: Typically used in modern aircraft, alternating current (AC) starter generators may be integrated with transformer rectifier units for DC applications.
• DC Starter Generators: Predominantly used in older or lighter aircraft, direct current (DC) starter generators can deliver direct current power without the need for external conversion hardware.

What Are Common Issues Faced by Starter Generators?

Despite their reputation for reliability, starter generators can undergo gradual performance decline or develop faults over time as a result of varying issues. Early detection of such issues is essential to prevent system-wide electrical malfunctions and potential operational disruptions, so be sure to review the following symptoms that should be looked out for:

• Voltage Irregularities: Fluctuating or insufficient voltage output may indicate brush wear, internal winding damage, or regulator faults.
• Excessive Heat: Overheating during operation can be a sign of blocked airflow, bearing degradation, or electrical overload.
• Unusual Noise or Vibration: Grinding noises, whining, or abnormal vibration can indicate issues stemming from mechanical wear, such as bearing failure or rotor misalignment.
• Startup Delays: Extended startup durations or difficulty initiating engine rotation may be due to deteriorated electrical contacts or compromised motor windings.
• Frequent System Resets: Inconsistent power delivery or frequent system resets may stem from intermittent faults or compromised electrical connections.

What Are Routine Maintenance Practices for Starter Generators?

The proactive maintenance of starter generators is essential for ensuring continued operational safety and reliability throughout flight operations. Maintenance schedules typically include the following practices:

• Brush Inspection and Replacement: Brushes in contact-based systems should be periodically examined for wear and replaced before they surpass their expected service life.
• Bearing Lubrication: Bearings should be cleaned and lubricated at manufacturer-recommended intervals to reduce the risk of overheating and mechanical failure.
• Electrical Testing: Performing resistance and insulation tests helps confirm winding health and allows for the detection of any signs of developing internal faults.

Obtain Affordable Purchasing Solutions on Aircraft Starter Generators

At ASAP Aerospace, a platform owned and operated by ASAP Semiconductor, we offer customers access to an extensive inventory of high-quality starter generator parts that are sourced from our network of reputable companies. We leverage our purchasing power and industry expertise to bring competitive prices to the table, as well as work with customers to narrow down optimal options based on budget. If you have any particular questions concerning our offerings or procurement process, you may always give us a call or email, as we would be more than happy to assist you however we can!