Chapter 11. Powertrain.

Question 1

What constitutes the Powertrain?

Answer 1

The powertrain is composed of the following
components 
• Main gearbox (MGB)
• Intermediate gearbox
• Tail rotor gearbox
• Rotor brake assembly
• Shafting, couplings, and hangers

Question 2

What are the functions of the intermediate gear box?

Answer 2

The intermediate gear box 
transmits torque,
changes the drive angle of the tail drive shaft
about 57°, and 
reduces rpm to the tail rotor

Question 3

What is the RPM of the main gear box at 107%Nr?

Answer 3

314 RPM

Question 4

What is the RPM of the engine output drive shaft at 107%Nr?

Answer 4

6409 RPM

Question 5

What is the RPM of the tail drive shaft at 107%Nr?

Answer 5

3491 RPM

Question 6

What is the RPM of the intermediate gear box at 107%Nr?

Answer 6

3370 RPM

Question 7

What is the RPM of the tail rotor gear box at 107%Nr?

Answer 7

1600 RPM

Question 8

What accessories are driven by the main gear box?

Answer 8

The main gearbox drives the following accessories
• Main gearbox oil cooler blower
• Two hydraulic pumps
• AC electrical generator
• Two gearbox lubrication pumps
Additional accessories mounted on the MGB
include a rotor brake and an accumulator/reservoir

Question 9

What causes the main gear box oil to bypass the oil cooler and go directly to the gearbox?

Answer 9

Oil is pumped from the sump of the gearbox
through the oil filter to the oil cooler.

The oil is directed through the cooler core or bypassed
directly to the gearbox by the thermostatic bypass valve at the top of the cooler.

The oil is bypassed if the oil temperature is below 68 to 74°C or if the core differential pressure is greater than 40 psid.

Oil flow is 15.8 gpm. Oil pressure at the manifoid is 80 ±5 psi with both pumps operating and 11.6 grpm at 40–45 psi with one pump operating.

Question 10

where is the oil filter mounted?

Answer 10

The oil filler is just above the oil sight glass window.

Question 11

Under normal operating conditions, at what pressure is the oil from the gear box pumped to the filter?

Answer 11

Oil from the gearbox sump is pumped to the

filter at 80 psi under normal operating conditions.

Question 12

When does the filter bypass indicator button extend?

Answer 12

When a pressure drop of 12 psid occurs because of clogging of the filter, the filter bypass indicator button extends to indicate an impending bypass condition.

A thermal lockout feature prevents the bypass
indicator button from extending until the oil
being filtered reaches 154° to 165°F (68° to
74°C).

Once extended, the filter bypass indicator button can be reset only by removing the filter housing from the gearbox and replacingthe clogged element

Question 13

When does the main gear box oil filter bypass occur?

Answer 13

Actual bypassing does not occur until clogging

produces a pressure drop of 20 psid.

Question 14

What is the function of the thermostatically controlled bypass valve in the MGB oil cooler?

Answer 14

The system includes a thermostat/bypass valve.

If oil temperature is <154° to 165°F (68° to 74°C) or if differential pressure is >40 psi, oil is bypassed to the return line by the thermostatically controlled bypass valve.

Question 15

How many chip detectors are installed on the main gear box?

Answer 15

Two chip detectors/oil strainers are installed on the main gearbox at the oil pump inlets in the bottom of the transmission sump

Question 16

Above what engine oil temperature will the chip detectors be inhibited?

Answer 16

The detectors also contain a temperature switch that inhibits the fuzz from zapping when oil temp exceeds 284°F (140°C).

This prevents the detector from arcing when the oil is in a vaporous state.

Question 17

What does a CHIP SYS FAULT caution indicate?

Answer 17

A CHIP SYS FAULT caution indicates that the chip detector system is not able to detect metal particles in the gear boxes being monitored.

Question 18

Where is the MGB temperature sensor located?

Answer 18

The oil temperature sensor (transmitter) is between the two chip detectors in the lower front portion of the main gearbox.

This location is the hottest main gearbox oil in the system.

Question 19

Above what temperature will the MGB OIL HOT caution illuminate?

Answer 19

If the oil temperature is greater than 221°F (120°C), the
MGB OIL HOT caution message illuminates.

Main gearboxes operating from 248° to 275°F
(120° to 135°C) for other than a short transient
period requires an inspection of the main gearbox
systems.

Main gearboxes operating from 275° to 284°F
(135° to 140°C) for a period of more than 30
minutes require inspection of oil filter and chip
detector/strainers for contamination. other than
a short transient period requires an inspection
of the main gearbox systems,

Main gearboxes operating above 284°F (140°C)
for any length of time must be replaced.

Question 20

Above what temperature will the MGB OIL HOT warning illuminate?

Answer 20

If the MGB oil temperature sensor exceeds
275°F (135°C), theVMM illuminates the MGB
OIL HOT warning message and a “MAIN
GEAR BOX OIL HOT” aural message is heard
in the headset.

The MGB OIL HOT caution
will extinguish when the warning illuminates.

Main gearboxes operating from 248° to 275°F
(120° to 135°C) for other than a short transient
period requires an inspection of the main gearbox
systems.

Main gearboxes operating from 275° to 284°F
(135° to 140°C) for a period of more than 30
minutes require inspection of oil filter and chip
detector/strainers for contamination. other than
a short transient period requires an inspection
of the main gearbox systems,

Main gearboxes operating above 284°F (140°C)
for any length of time must be replaced.

Question 21

Where is the MGB low oil pressure warning switch located?

Answer 21

The low oil pressure warning switch is between
the hydraulic pumps on the lower front side of
the main gearbox

This location is the lowest oil pressure in the system.
the switch provides a warning on the WCA
whenever the MGB oil pressure drops <14 psi.

Question 22

What powers the MGB low oil pressure warning switch?

Answer 22

The No. 1 DC ESS bus powers the switch.

Question 23

At what pressure will the MGB oil pressure switch close?

Answer 23

The MGB oil pressure warning switch closes

at 14 psi.

Question 24

The tail drive shaft consists of how many sections?

Answer 24

The shaft consists of five sections and extends
from the tail rotor takeoff flange of the main
gearbox to the input side of the intermediate
gearbox, and from the output side of the intermediate
gearbox to the input of the tail gearbox

Question 25

How is the intermediate gear box lubricated?

Answer 25

The intermediate gearbox is splash-lubricated and

air-cooled.

Question 26

What causes the IGB CHIP/HOT caution to illuminate?

Answer 26

If chips are detected in the oil sump of the intermediate gearbox or if oil temperature >284°F (140°C), a signal is supplied to the VMM to illuminate the IGB CHIP/HOT caution message

Question 27

How is the chip detector processor (CDP) unit powered?

Answer 27

Electrical power for the Chip Detector Processor unit (CDP) for the 6 detectors is through a 5 amp CHIP DET circuit breaker on the No. 1 DC ESS bus

Question 28

What makes up the rotor brake system?

Answer 28

The manual rotor brake system consists of the
following:
• Accumulator/reservoir and relief valve
• Master cylinder/handle
• Rotor brake assembly
• Pressure switch
• WCA caution message

Question 29

At what pressure will the rotor brake over pressure relief valve actuate?

Answer 29

The relief valve actuates at 435 psi ±30 psi.

Question 30

What causes the rotor brake caution light to illuminate and when does it extinguish?

Answer 30

Pressure greater than 10 psi on the pressure
switch completes an electrical circuit to illuminate
the ROTOR BRAKE ON caution message
on the WCA.

When system pressure goes below approximately 7 psi,
the ROTOR BRAKE ON caution message extinguishes.

Question 31

What is considered normal rotor brake pressure?

Answer 31

Normal brake pressure to stop the

rotors is approximately 300-350 psi.

Question 32

What is the normal Nr for rotor brake application?

Answer 32

Normal NR for rotor brake application ?? 40 to 60%.
Maximum NR is 65% for normal rotor brake
application.

Brake application begun at less than 30% NR
should be light enough to produce a smooth,
gentle stop.

Rotor shutdown with the rotor brake shall not be performed more than one time in any 10 minute period

Minimum time to stop the rotor from
45% NR or greater with the rotor brake
is 8 seconds