The AW 139 main gearbox, or Main Gearbox MGB IGB, forms the core power transmission unit for this medium twin-engine helicopter. Understanding the AW 139 main gearbox components and general information MG IGB helps operators and technicians maintain reliability and safety.
This overview presents key specifications, major assemblies, and operational context for the AW 139 main gearbox and its integral Input Gear Box IGB.
| Item | Specification | Unit | Notes |
|---|---|---|---|
| Model designation | Leonardo Main Gearbox MGB IGB | – | Integrated main and input gear box for AW 139 |
| Typical input speed | 6,000 | rpm | At maximum continuous power setting |
| Primary output speed | 364 | rpm | To main rotor head |
| Oil system | Dry sump with scavenge pump | – | Independent lubrication circuit |
| Mounting configuration | Split housing with spherical bearings | – | Enables thermal expansion compensation |
Main Gearbox Internal Layout and Load Path
The AW 139 main gearbox internal layout arranges gears, bearings, and shafts to manage high torque while minimizing vibration. The power enters through the input shaft, passes through planetary stages, and exits to the main rotor through a carefully balanced set of bevel and helical gears.
This layout ensures efficient torque transmission and allows the Main Gearbox MGB IGB to operate within strict limits even during aggressive maneuvers. Housing design, bolted joints, and internal dampers work together to control noise and fatigue-related stresses.
Input Gear Box IGB Function and Integration
The Input Gear Box IGB integrates directly with the main gearbox to provide a compact, efficient power path. It includes planetary stages that reduce engine speed to an optimal level before torque reaches the main stage gears.
Because the Input Gear Box IGB is part of the single housing, inspections must consider both modules together. Proper lubrication, alignment checks, and timely component replacement help avoid early failures in this critical area.
Major Maintenance Components and Inspection Points
Routine and condition-based maintenance of the AW 139 main gearbox focuses on a small set of high-impact components. Technicians should verify the integrity of these assemblies at every scheduled visit.
- Main and planet gears in the Input Gear Box IGB
- Bearings, including spherical seat interfaces
- Oil pump, filters, and scavenge elements
- Shaft seals and housing gaskets
- Temperature and pressure sensors
Troubleshooting Oil System and Contamination Signs
Oil quality and system performance are decisive for the longevity of the Main Gearbox MGB IGB. Regular sampling, correct viscosity, and filtration prevent scoring, pitting, and premature bearing wear.
Operators should watch for rising temperature trends, unusual noises during power changes, and metal particle readings in oil reports. Early detection allows component replacement before catastrophic failure occurs.
Key Takeaways for Operators and Technicians
- Understand the integrated architecture of the Main Gearbox MGB IGB and Input Gear Box IGB
- Monitor oil particles, temperature trends, and vibration data to catch issues early
- Use correct oil grade, filtration, and housing seals during every maintenance event
- Follow approved inspection intervals and service bulletins from Leonardo
- Train crews on recognizing early signs of gear and bearing distress
FAQ
Reader questions
How often should the main gearbox oil and filters be changed on an AW 139?
Follow the current maintenance program approved by the authority and Leonardo service bulletins, typically combining oil changes with hot-case inspections every 500 to 800 flight hours, depending on operating conditions and contamination trends.
What are the most common failure modes in the Input Gear Box IGB?
Planetary gear wear, bearing spalling, and seal leakage are frequent issues, often revealed by rising oil particle counts, vibration signatures at 1X and 2X rpm, and localized heating during pre-flight checks.
Can contamination in the main gearbox be traced to a specific subsystem on the AW 139?
Yes, contamination patterns can indicate air separator degradation, breather issues, or improper cleaning during overhaul; correlation with oil analysis and component removal helps pinpoint the root cause.
What operational limits should be observed to protect the Main Gearbox MGB IGB during flight?
Avoid prolonged heavy power settings above recommended turbine entry temperatures, respect maximum continuous torque limits, and perform autorotative run-down drills to reduce heat buildup and fatigue in the gearbox components.