Chapter 11. Powertrain. Flashcards
Learn about the powertrain installed on the S76D
What constitutes the Powertrain?
The powertrain is composed of the following components • Main gearbox (MGB) • Intermediate gearbox • Tail rotor gearbox • Rotor brake assembly • Shafting, couplings, and hangers
What are the functions of the intermediate gear box?
The intermediate gear box transmits torque, changes the drive angle of the tail drive shaft about 57°, and reduces rpm to the tail rotor
What is the RPM of the main gear box at 107%Nr?
314 RPM
What is the RPM of the engine output drive shaft at 107%Nr?
6409 RPM
What is the RPM of the tail drive shaft at 107%Nr?
3491 RPM
What is the RPM of the intermediate gear box at 107%Nr?
3370 RPM
What is the RPM of the tail rotor gear box at 107%Nr?
1600 RPM
What accessories are driven by the main gear box?
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
What causes the main gear box oil to bypass the oil cooler and go directly to the gearbox?
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.
where is the oil filter mounted?
The oil filler is just above the oil sight glass window.
Under normal operating conditions, at what pressure is the oil from the gear box pumped to the filter?
Oil from the gearbox sump is pumped to the
filter at 80 psi under normal operating conditions.
When does the filter bypass indicator button extend?
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
When does the main gear box oil filter bypass occur?
Actual bypassing does not occur until clogging
produces a pressure drop of 20 psid.
What is the function of the thermostatically controlled bypass valve in the MGB oil cooler?
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.
How many chip detectors are installed on the main gear box?
Two chip detectors/oil strainers are installed on the main gearbox at the oil pump inlets in the bottom of the transmission sump
Above what engine oil temperature will the chip detectors be inhibited?
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.
What does a CHIP SYS FAULT caution indicate?
A CHIP SYS FAULT caution indicates that the chip detector system is not able to detect metal particles in the gear boxes being monitored.
Where is the MGB temperature sensor located?
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.
Above what temperature will the MGB OIL HOT caution illuminate?
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.
Above what temperature will the MGB OIL HOT warning illuminate?
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.
Where is the MGB low oil pressure warning switch located?
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.
What powers the MGB low oil pressure warning switch?
The No. 1 DC ESS bus powers the switch.
At what pressure will the MGB oil pressure switch close?
The MGB oil pressure warning switch closes
at 14 psi.
The tail drive shaft consists of how many sections?
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
How is the intermediate gear box lubricated?
The intermediate gearbox is splash-lubricated and
air-cooled.
What causes the IGB CHIP/HOT caution to illuminate?
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
How is the chip detector processor (CDP) unit powered?
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
What makes up the rotor brake system?
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
At what pressure will the rotor brake over pressure relief valve actuate?
The relief valve actuates at 435 psi ±30 psi.
What causes the rotor brake caution light to illuminate and when does it extinguish?
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.
What is considered normal rotor brake pressure?
Normal brake pressure to stop the
rotors is approximately 300-350 psi.
What is the normal Nr for rotor brake application?
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
