Gear Box (MGB and TGB) Flashcards
the MGB is a —- stage system
three stage reduction gear box system
How much does the MGB reduction system reduce engine RPM? Think… red gear box produces 6,000 rpm
NR spins @ 355RPM
TR spins @ 4000RPM
reduces engine input RPM by a ratio of 17 to 1 to drive the main rotor, and 1.5 to 1 to drive the tail rotor.
6000/355=17
6000/1.5=4000
What does the MGB consist of?
- left and right engine input housings and accessory gearboxes(primary[right] & secondary[left])
- shafts for driving the NR tachometer generator and MGB oil system pump
- and an accessory drive for the oil cooler and rotor brake.
How many lubricating systems does the MGB have?
The main gearbox has two lubricating systems consisting of a two stage oil pump with main
and auxiliary pumping elements connected by a shear shaft.
What does the main lubricating system lube?
The main system provides oil flow through external lines and the oil cooler
What does the MGB aux oil system lubricate?
the auxiliary system provides internal oil flow only.
Describe MGB lubricating system, normal operation.
During normal operation, the main pump circulates oil through the oil cooler, filter, and to the MGB jets. During normal operation, the auxiliary pump operates, but its output is blocked by a shuttle valve which is held closed by higher pressure from the primary system, causing auxiliary system oil flow to return to the MGB sump via the auxiliary relief valve.
If the MGB main pump fails or shaft shear, how does the auxiliary pump take over? Think… shuttle valve.
In the event of main pump failure or shaft shearing, the auxiliary pump will continue to operate. The shuttle valve opens and oil is pumped from the MGB sump directly through the filter to the jets at a lower pressure and without the benefit of cooling.
What should be noted if the auxiliary pump is providing oil? Think… higher psi from the main pump keeps the shuttle valve secure
An increase in oil temperature and a lower oil pressure will occur when the auxiliary pump is providing MGB lubrication
What is significant for cooling purposes of being at or above 120KIAS?
Ram air is sufficient for MGB oil cooling, no longer needing the fan to be on
How many pressure switches measure the MGB oil pressure?
MGB oil pressure is measured by three pressure switches. One switch is located in the oil filter outlet line, a second in the main oil system, and a third in the auxiliary system.
What does the MGB indication system monitor?
The MGB indicating system monitors oil temperature, oil pressure, and metal chip detection.
Results if minimum PSI, 9(+/-1), at the filter outlet is sensed
MGB PRESS warning light to illuminate and
the two master WARNING lights located on the instrument panel to flash. If the minimum pressure is sensed at the pump output of the main or auxiliary system, either the MGB PMP MAIN caution light or MGB PMP AUX caution light will also illuminate.
Results of Oil Temp reaching max allowable temperature of 120 degrees Celsius?
The master WARNING lights and the OIL TEMP warning light will illuminate
How is MGB oil psi measured and where is it displayed?
MGB oil pressure is measured by a pressure transmitter mounted on the oil filter outlet line, and is displayed on the XSMN OIL P scale on the VEMD.
