Whats the purpose of the transmission system?
It takes the combined power from the two engines, reduces the RPM, and transfer it to the Main and Tail Rotors.
It's secondary function is to provide drive for the hydraulic pumps and electrical generators.
What does the tail rotor drive shaft consist of?
The drive shaft consists of six sections with a disconnect coupling at the fold hinge
The shafts are ballistically tolerant and suspended at four points by viscous-damped bearings
The sections are connected by Thomas-couplings in order to allow temporary misalignment while spinning
What does the transmission consist of?
How much is it tilted?
A modular design with a 3° forward tilt, it consists of 2 accessory modules, 2 input modules, and a main module.
You also have a utility hydraulic system, an oil sump, an oil filter, and temp/pressure/chip sensors
What does the input module do?
What about it is important for Autos?
Provides the front support for the engines and provides the first gear reduction.
A freewheeling unit allows the engine to decouple from the transmission when Nr exceeds Np
What does the Diaphragm coupling do?
Transfers drive from the engine to the input module, it also allows for slight angular or axial misalignment of the engine output shaft
What does the Accesory module do?
Which sensor is on which Module?
The accesory module is mounted on the forward part of each module and provides a mounting drive for an electrical generator and hydraulic pump module
The Nr sensor for the vertical instruments is mounted on the right module (Think NR, on the Right), and the one for the TDI on the left module
What kind of lubrication do the IGB and TGB have?
What do the gearboxes do?
They are both splash lubricated
The IGB reduces shaft speed and changes the angle of the drive
The TGB changes the angle of drive and provides gear reduction, it has a 20° left tilt
What kind of lubrication system does the transmission have?
How many pumps does it have?
It has a wet sump lubrication system, providing filtered and cooled oil to all main transmission bearings
With two pumps, the transmission has a redundant system in the even one fails
Describe the path that transmission oil travels
Oil is pumped through a transmission filter from the sump (the filter may be bypassed in the event of a clog)
It then passes through an air oil cooler over a pressure and temperature sensor, then to the various modules and the generator bearings
It returns to the main sump after passing over accessory and input chip detectors where it will settle on the main transmission chip detector / temperature sensor
Describe the Transmission oil pressure low sensors
The sensor immediately after oil cooler will measure oil pressure and display the indications in the cockpit, if it senses oil pressure is less than 30psi and Nr is greater than 25%, it will activate the white oil pressure low advisory.
The left accessory module has another oil pressure sensor which will activate the oil pressure low caution when it senses oil pressure to be below 14psi
Describe the transmission oil temperature sensors
The main transmission chip detector located at the bottom of the sump doubles as the temperature sensor displaying oi temp in the cockpit. It will also illuminate the oil hot advisory when temperatures reach 105°C
The temperature sensor located immediately after the air/oil cooler will illuminate the oil hot caution when it senses oil temperature exceeding 117°C
How many chip detectors does the system have?
Where are they located?
The main transmission system has 5 chip detectors, each with a corresponding caution.
The accessory chip detectors are located in the return lines of the accessory modules
The input chip, and main module chip detectors are located in the main transmission module
Describe the Chip detectors and the fuzz burn off feature.
The chip detectors us magnetic plugs to attract ferrous metal chips, then the circuit is complete the appropriate caution will appear.
The fuzz burn off feature will attempt to reduce false cautions by heating up to burn off any minute particles. This feature is disabled when oil temperatures exceed 140°C
How is the main chip dectector different from the others?
The main chip detector rests at the bottom of the sump and has an additional 30 sec time delay to further eliminate any false warnings. It also has a temperature sensor which drives the display in the cockpit
What happens when you run the Chip IBIT?
The system will test the circuitry and individual chip detectors for faults
It takes approximately 2min to run and for the first 40sec, power is interrupted to the WCA and Master Caution