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761574B – UTC Aerospace (Hamilton Sundstrand) Integrated Drive Generator (IDG)
Available now on the Airparts.aero Marketplace.
The UTC Aerospace (Hamilton Sundstrand) 761574B is a flight-critical Line Replaceable Unit (LRU) that serves as the primary source of AC electrical power for the Boeing 737 Next Generation (NG) fleet. This sophisticated Integrated Drive Generator (IDG) combines two traditionally separate components—the Constant Speed Drive (CSD) and the AC Generator—into a single, compact, and high-efficiency housing. The 761574B is engineered to take the variable-speed rotational energy from the engine’s accessory gearbox and convert it into a stable, constant-frequency 400 Hz electrical output, which is essential for the operation of sensitive avionics, flight control systems, and environmental control units.
By utilizing a complex hydraulic mechanical differential system, the 761574B maintains a precise output speed of 24,000 RPM, regardless of engine thrust settings or transient power changes during climb, cruise, or descent. This unit is designed for extreme durability and thermal stability, incorporating its own internal oil cooling and filtration system to manage the high heat loads generated during power conversion. The 761574B is a linchpin of aircraft dispatchability; its high MTBF (Mean Time Between Failure) and integrated monitoring features allow for predictive maintenance, ensuring that the Boeing 737NG fleet remains operational and safe.
Key Features
Integrated CSD and Generator: Combines mechanical speed regulation and electrical generation into one unit, reducing total weight and simplifying the engine accessory interface.
Precision Hydraulic Governor: Utilizes a mechanical-hydraulic governing system to ensure frequency stability within the strict ±1% tolerance required for 400 Hz systems.
90 kVA High-Output Capacity: Capable of delivering continuous 115/200V AC 3-phase power to meet the high electrical demands of modern glass-cockpit aircraft.
Advanced Internal Oil Management: Features an integrated charge pump, scavenge pump, and rotating deaerator to ensure consistent lubrication and cooling under high G-loads.
Mechanical Disconnect System: Includes a flight-deck-controllable mechanical disconnect that allows the crew to isolate the IDG from the engine gearbox in the event of a thermal or mechanical anomaly.
Technical Specifications
Part Number: 761574B
Component Type: Integrated Drive Generator (IDG)
OEM Manufacturer: UTC Aerospace Systems (Hamilton Sundstrand / Collins Aerospace)
Output Power: 90 kVA
Output Voltage: 115/200V AC, 3-Phase
Frequency: 400 Hz
Constant Output Speed: 24,000 RPM
ATA Chapter: 24 (Electrical Power)
Material: High-strength Aluminum Alloy housing (A356.0-T6 or similar), AISI 9310 Steel gears
Dimensions: Approximately 18 x 18 x 14 inches
Weight: 116.7 lbs (Approx. 53 kg)
Governing Specifications: MIL-G-21480, RTCA DO-160
Certification: FAA-PMA / Boeing OEM Original Equipment
Aircraft Compatibility
Boeing 737-600
Boeing 737-700 / 737-700C
Boeing 737-800 / 737-800BCF
Boeing 737-900 / 737-900ER
Note: This unit is specific to the CFM56-7B engine accessory gearbox. Always refer to the Boeing 737NG Illustrated Parts Catalog (IPC) to verify the correct dash-number and mod-status for your specific tail number.
Applications
Primary AC Power Generation: Supplies the main AC buses for all onboard aircraft systems.
Avionics & Flight Controls: Provides the stable frequency required for the Flight Management System (FMS) and Digital Autopilot.
Galley & Utility Power: Manages the heavy electrical loads required for cabin lighting and galley equipment.
Why Choose 761574B?
The 761574B is the result of decades of Hamilton Sundstrand expertise in aircraft power systems. Choosing an OEM Integrated Drive Generator is vital for protecting the integrity of the aircraft's electrical grid. Non-certified or improperly overhauled units risk "frequency wander" or mechanical seizure, which can lead to catastrophic damage to the engine accessory gearbox or total loss of a primary electrical channel. By sticking with the UTC Aerospace standard, operators ensure maximum reliability, lower lifecycle costs, and the absolute assurance that their power generation system can handle the rigorous demands of ETOPS operations.
The 761574B functions through a complex Hydro-Mechanical Differential principle. Because jet engine RPM varies significantly between ground idle and takeoff thrust, a direct-drive generator would produce an unusable, fluctuating frequency. To solve this, the IDG utilizes a Variable-Displacement Hydraulic Pump and Motor assembly acting on a Planetary Differential. By varying the displacement of the hydraulic unit, the system either adds or subtracts rotational speed from the engine input to maintain a perfect 24,000 RPM at the generator rotor.
The internal materials are selected for extreme Hysteresis resistance and thermal endurance. Gears are typically manufactured from AISI 9310 vacuum-arc remelted (VAR) steel, which is carburized and precision-ground to withstand the immense torque loads of 90 kVA generation. The housing is cast from precipitation-strengthened aluminum alloys to provide high strength-to-weight ratios and efficient heat dissipation. Furthermore, the generator windings utilize high-purity copper with Polyimide insulation to prevent dielectric breakdown under the high thermal gradients encountered at 41,000 feet.
Note: The 761574B is a flight-critical LRU. Proper oil level and oil clarity are the most important indicators of unit health. Any evidence of metallic "glitter" in the scavenge filter or a magnetic chip detector (MCD) hit requires immediate removal for shop inspection. Installation must be performed by a certified A&P mechanic in accordance with the Boeing 737NG AMM and the UTC/Hamilton Sundstrand CMM 24-11-85. Ensure the input shaft splines are properly lubricated with the specified Aeroshell or Mobil grease during installation.
