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Archived Military Aviation > Powertrain > Flashcards

Powertrain Flashcards

1
Q

(COL) What is a planetary gear train?

A

Consists of a central gear (sun gear), intermediate pinons (planetary gears), and a coaxial ring gear. The pinon gears rotate about the sun gear.

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2
Q

(COL) Why is efficiency in gear trains important?

A

More power is transferred to components
Energy requirements are less
Friction, heat, and wear are reduced

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3
Q

(COL) What is different about the teeth on a spiral bevel gear?

A

The teeth are curved.

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4
Q

What is backlash?

A

The amount by which tooth space exceeds the thickness of and engaging tooth.

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5
Q

NGB rpm reduction?

A

21,162 to 9939 rpm

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6
Q

NGB backlash?

A

Twice the normal is provided to accommodate high thermos expansion during emergency operations.

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7
Q

What is unique about NGB bearings?

A

Bearings use silver-plated M50 steel races to provide initial lubrication during starts and assist in emergency operations.

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8
Q

NGB major components?

A 
Housing assemblies
Quill shafts
Input bevel gear assemblies
Output shaft/spiral bevel gear assemblies
Triplex bearings
Duplex bearings
Roller bearings
Fan mounting adapters
Oil pump housing
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9
Q

NGB Housing components/description?

A

Magnesium alloy / finned for cooling
Input/output retainers for Input/output seals
Bearing support covers for output shaft (for oil pump and roller bearings)

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10
Q

NGB input bevel gear assemblies description?

A

Splined to quill shaft / steel
30 felt disks for oil wicking
dam installed to hold felt disks

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11
Q

NGB output shaft/spiral bevel gear assembly description?

A

32 felt disks for oil wicking (w/ dam)
Dam drilled for lubing duplex bearings
Splined end to drive oil pumps
Output shaft’s spiral bevel gear has spirolox ring for dampening harmonic freqs - allows for smaller gearbox

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12
Q

NGB duplex and triplex bearing locations?

A

Duplex output shaft / triplex input shaft

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13
Q

NGB roller bearing assemblies?

A

Support bevel gear ends of the input and output shafts

Transmit radial loads to housing

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14
Q

NGB oil sump capacity?

A

5 pints

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15
Q

NGB oil type?

A

MIL-L-23699 (OAT -32 C and above)

MIL-L-7808 (OAT -32 C and below)

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16
Q

NGB Lubrication system components?

A 
Sump assembly
Pressure transducer
Pressure switch
Chip detector/Temperature switch
Temperature transducer
Sight level plug
Breather vent
Filter w/ bypass indicator
Filler plug
Oil jets
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17
Q

NGB oil pump description?

A

Rated for 2.3 gpm and 50 psi (at 9939 or 101%)
Relief values crack at 68+/-4 psi fully open at 90 psi
Oil is returned to sump

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18
Q

NGB oil pressure switch parameters?

A

Removes signal to SP at 45+/-2 psi increasing

and 28+/-2 psi decreasing

19
Q

NGB chip detector/temp sensor description?

A

Houses a capacitor that discharges to burn “fuzz” without activating caution.
Temperature sensor is discrete signal to SP
134 - 146 C increasing or 129 - 118 C decreasing

20
Q

NGB oil pump type?

A

Georotor type

21
Q

NGB oil filter parameters?

A

12 micron
Impending bypass button pops at 23+/-2 psid
Thermal lockout below 29.5 C (oil temp) deactivated 46-67 C
Bypass valve opens at 38+/-2 psid

22
Q

NGB oil jets description?

A

Internal filters
LEFT NGB
Top fwd lubes input roller bearings and input felt disks
Top aft lubes inboard gear mesh
Outboard lubes triplex bearing
RIGHT NGB
Top aft replaced by plug - jet moved to inboard side by output shaft

23
Q

NGB fan considerations?

A

Fan impeller and diffuser are serialized matched components.

24
Q

XMSN gear reduction?

A

Three stage
292 rpm main rotor (701C)
4863 rpm tail rotor

25
Q

XMSN emergency features?

A

Silver plated steel bearing racers
Felt wicking disks in drive shafts
Twice the normal backlash
Can operate with one of two oil systems inop (check valves and float diverter)

26
Q

XMSN major components?

A

Housing
2 input clutch assemblies
Primary gear train
Secondary gear train

27
Q

XSM housing description?

A

lightweight magnesium alloy
Four piece assembly
Cover (curvic coupling - torsional loads)
Intermediate gear support housing (oil galleries)
Lower housing assembly ( oil sumps, galleries, support of input clutch assemblies, and accessory mounting)
Accessory cover (internal oil jets)

28
Q

Input clutch assembly description?

A 
Contains overrunning (Sprag) clutches
2 hours permissible with no impairment
Does not affect 30 min emergency window
29
Q

Describe the 3 stages XMSN gear reduction

A

Input pinion gear to cluster gear 9939 to 4546
Cluster gear to intermediate helical gear 4546 to 1160
Intermediate helical gear to planetary gear 1160 to 292

Cluster gear to tail rotor drive gear 4863 (LH cluster)

30
Q

What gear drives the XMSN oil pumps?

A

Lower splined portion of cluster gears

31
Q

What type of damper rings are installed on the XMSN and where are they located?

A

Spirolox damper rings are installed on the cluster gears and intermediate helical gear.

32
Q

Which intermediate cluster gear is primary? How many teeth?

A

No. 2 is primary with 85 teeth (84 on No.1)

33
Q

How is the APU able to run accessory components without driving the rotor?

A

Overrunning clutches are installed on each intermediate cluster gear ( and tail rotor drive gear?)

34
Q

What are the two types of rotor brake assemblies? Are they interchangeable?

A

Parker Hanifin and Goodyear. No

35
Q

Magnetic pickup caution?

A

Do not rotate pickup during removal or installation, doing so damages the alignment pin and mag pickup.

36
Q

Describe magnetic pickup

A

Provides RPM signal to ENG page and MSPU. MSPU monitoring mode is group 1 components only, triggered at 90% RPM, sensed by MSPU through TACH 3.
Housed on same axis as secondary clutch - allows no Nr reading on APU.

37
Q

What prevents collateral damage in the event of a generator seizure?

A

Nylon spline adapters

38
Q

How are generators sealed?

A

Plain encased seal in housing and cork stopper in driveshaft.

39
Q

How many oil jets does the XMSN have?

A

10

40
Q

XMSN oil pump ratings?

A

6.5 gpm +/-0.25 gpm at 75 psi at 101%

scavenge element 2 gpm 50 psig at 101%

41
Q

XMSN oil filter parameters?

A

12 micron
Bypass indication at 23+/-2 psid (thermo lockout below 29.5 C oil temp) deactivated 46-67 C
Bypass value opens 38+-4 psid

42
Q

XMSN pressure switch parameters?

A

Signal SP at 28+/-2 psi decreasing, removed at 45+/-2 psi increasing.

43
Q

XMSN temperature switch parameters?

A

Provide signal to SP when reaches 140+/-12 C removed when drops to 123+/-12 C

44
Q

XMSN normal operating pressure?

A

60-85 psi

Archived Military Aviation (26 decks)

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