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Engine and Engine controls Flashcards

1
Q

What kind of engine do we have

A

T700-GE-401C front drive turboshaft engine

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2
Q

what are the 5 sections of the engine

A

inlet compressor combustor turbine exhaust

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3
Q

air flow through engine

A

through inlet cowling then to swirl vanes inlet particle separator deswirl vanes compressor combustor gas generator turbine power turbine then out

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4
Q

describe the compressor section

A

5 stage axial and single stage centrifugal system

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5
Q

describe the combustion section

A

flow through annular combustion chamber
2 igniters
12 fuel injectors

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6
Q

function of gas generator turbine

A

drives the compressor and AGB

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7
Q

describe the gas generator turbine

A

two stage air cooled high performance axial design

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8
Q

which turbine shaft turns inside the other

A

Np spins inside Ng

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9
Q

what does the Np turbine do

A

drives high speed output shaft

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10
Q

where is TGT sensed

A

between Ng and Np turbines

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11
Q

how much of the total airflow is used for combustion

A

about 30%

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12
Q

what is the airflow not used for combustion used for

A

compressor inlet temp (T2) air
compressor discharge (P3) air
combustor and turbine cooling
engine oil seal pressurization

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13
Q

what does the AGB drive

A

starter, HMU, IPS blower, ODV
alternator, eng driven fuel boost pump

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14
Q

goal of the engine control system

A

proper and complete control of the engine to maintain a constant Np and Nr

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15
Q

major components of engine control system

A

HMU
ODV
EDECU
Alternator
series of fuel flow control valves

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16
Q

general function of HMU

A

provides Ng control

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17
Q

general function of EDECU

A

trims the HMU to meet Np requirements and lessen pilot workload

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18
Q

What does putting the PCL in the off position do

A

PAS mechanically shuts off fuel at the shutoff valve in the HMU

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19
Q

what does putting the PCL in the idle position do

A

Controls HMU to auto control start sequence to get to self sustaining combustion

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20
Q

what does putting the PCL in fly do

A

sets max level of power that could be supplied if demanded

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21
Q

what does putting the PCL in lockout and back do

A

disables TGT limiting, load sharing and Np governing and allows for manual control of Np and Ng

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22
Q

how to get engine back to normal from lockout

A

idle then fly

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23
Q

what does the solenoid on the quadrant do

A

prevents moving engines past idle with rotor brake on unless the override tab is pulled

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24
Q

function of the load demand system

A

routes collective input to control HMU to auto control engine speed and provide required power

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25
Q

function of eng driven fuel boost pump

A

provides reliable suction feed to eng
suction to reduce likelihood of fire hazard

and provides enough pressure to meet requirement of HMU/high px fuel pump

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26
Q

does the engine fuel filter filter water

A

no

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27
Q

how does fuel get to fuel filter and where does it go

A

from eng driven fuel pump to HMU high px fuel pump

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28
Q

can the PDI on the eng fuel filter be reset

A

only by removing the filter element and bowl

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29
Q

what gives us the #1/2 fuel fltr bypass caution

A

electric switch attached to bypass valve

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30
Q

what does HMU stand for

A

hydromechanical unit

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31
Q

what is in the HMU

A

High px fuel pump
Ng governor
metering valve
linear variable displacement transducer
torque motor servo
variable geometry vane servo
vapor vent
shutoff valve

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32
Q

how does fuel go through the HMU

A

enters at high px pump through metering and shutoff valve sent to the oil to fuel heat exchanger while some fuel is used to position metering valve, variable geometry vane servo start valve and amplify T2,P3, Ng signals, then goes to ODV

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33
Q

2 mechanical and one electric link to HMU

A

MECH: LDS (collective) and PCL (PAS)
ELEC: EDECU moves torque motor servo to precisely trim Ng

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34
Q

what does the PCL input to the HMU provide

A

fuel shutoff
start fuel flow with auto acceleration
set permissible Ng to max
fuel priming
EDECU Lockout

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35
Q

what other signals then the main 3 does the HMU respond to

A

T2,P3, Ng which help control variable stator vanes and anti ice/start bleed valve to reduce likelihood of compressor stall

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36
Q

how does the HMU act when there is no EDECU input

A

like a conventional gas generator

37
Q

what does the HMU provide

A

fuel scheduling for min/max fuel flow and variable stator vane control

38
Q

how does the HMU respond to the torque motor servo input from the EDECU

A

LVDT passes feedback signal to prevent hunting

39
Q

what happens to excess fuel from HMU

A

rerouted to pump inlet

40
Q

Ng overspeed valve trip point

A

110 +/- 2%

41
Q

what 2 reasons does the PAS set power available above what is required

A

fail safe to high power in the event of an electrical failure to the torque motor the system resets to max power
OEI conditions

42
Q

What does the HMU provide

A

Rapid engine transient response through collective compensation
Auto fuel scheduling for eng start
Ng overspeed protection
Ng governing
Acceleration limiting
Flameout and compressor stall protection

43
Q

describe the Ng overspeed protection provided by HMU

A

if Ng reaches the 110 +/-2% a valve secures fuel flow to the engine until the overspeed condition is gone

44
Q

describe the Ng governing provided by the HMU

A

uses T2, P3, Ng to schedule fuel flow

45
Q

describe the Acceleration limiting provided by HMU

A

ensures PCL motion will not damage the engine or cause inadvertent shut down

46
Q

describe the flameout/compressor stall protection afforded by the HMU

A

moves variable geometry vane and anti-ice/start bleed valve to prevent compressor stall instability

47
Q

what is the ODV

A

overspeed and drain valve

48
Q

4 functions of the ODV

A

provides fuel flow to the 12 fuel injectors
purges main fuel manifold overboard post shutdown to prevent coking
traps fuel upstream in fuel/oil heat exchanger so we don’t have to keep priming
returns fuel to HMU in Np overspeed energized or EDECU hot start preventer activated

49
Q

what 2 conditions will the HMU limit fuel flow separate from other limits

A

combos of T and press alt with a high power required setting where the fuel lines are simply not big enough to provide the required fuel
Ng/T combo that protects the compressor section - usually cold temps

50
Q

what does the alternator power

A

ignitor assembly
EDECU
Ng signal to the vertical instruments

51
Q

what does EDECU stand for

A

enhanced digital electronic control unit

52
Q

what are the control parameters of the EDECU

A

Np sensing (governing)
Np overspeed and Q sensing
TGT monitoring

53
Q

cockpit signals to EDECU

A

ENG spd trim switch
Cpow switch
ENG ovspd test A and B

54
Q

helicopter signals to edecu

A

torque from other EDECU
Np demand
400 Hz backup power
HMU (LVDT)

55
Q

Signals from EDECU to cockpit

A

Torque
Np
TGT
Cpow

56
Q

how many EDECU functions are there

A

16

57
Q

What are the EDECU functions

A

Np governing
Np overspeed protection
Np overspeed test
Ng decay relight
Cpow manual
Cpow auto
Cpow dual auto
hot start prevention
eng load sharing
fault diagnostic system
transient droop improvement
auto ignition system
signals cockpit
TGT limiting
eng speed trim
DECU lockout

58
Q

describe EDECU Np governing

A

Np sensor on the left of Np section sends an Np signal to the EDECU that is comparted to a reference Np

59
Q

describe EDECU Np overspeed protection

A

Uses signal from Np overspeed and Torque sensor on right side of Np section. when Np>120 sends a signal to ODV to divert fuel to HMU causing a flameout

60
Q

can we reset popped eng ovspd CB in flight

A

shall not

61
Q

describe EDECU TGT limiting

A

measured is compared to a reference TGT, if above it signals to reduce fuel flow. when TGT gets to 878, it prevents any further increase in fuel flow
has a max rated power limiter that will stop TGT at 866 +/- 10

62
Q

describe EDECU eng load sharing

A

both EDECUs share their torque level and the system will try to raise the torque of the lower eng to the higher

63
Q

describe EDECU eng speed trim

A

speed trim witch can manipulate EDECU reference between 96 and 101%

64
Q

describe EDECU manual cpow

A

uses the switch to change the TGT limit from 878 to 903 but like normal it will prevent further fuel flow at 891 +/-10
also deactivates ECS
only cpow that gives us a signal it is on

65
Q

describe EDECU auto cpow

A

happens in OEI conditions when Q of one engines falls below 50%, the 866+/-10 is changed to 891 +/-10

66
Q

describe EDECU dual cpow

A

makes the switch from the 866 +-10 to 891+-10 if one or more of the following conditions exist
Np<96
greater than 3% droop from ref Np and actual Np
greather than 5%/sec droop in Np if Np less than or equal to reference point

67
Q

describe EDECU overspeed test

A

only when Np>96%
artificially lowers the Np overspeed limit from 120 to 96 causing flameout

68
Q

describe EDECU lockout

A

disable torque motor servo and thus deactivates TGT limiting, Np governing, and load sharing
retains Np overspeed protection

69
Q

Describe EDECU cockpit signals

A

provides Np, TGT, and torque signals to to DTC for cockpit display

70
Q

Describe EDECU hot start prevention

A

if TGT exceeds 900 with Ng <60 and Np<50 auto stops fuel flow
restores when TGT gets down to 300 c or after 25 seconds whichever is first
can be disabled by holding one of the overspeed buttons for the whole start
auto tests in Np overspeed test

71
Q

describe EDECU transient droop improvement

A

using signals from TDI Nr sensor on left accessory module and a collective position sensor in the mixing unit, will increase fuel flow early at low torque settings when collective demand increases rapidly or rapid Nr decay

72
Q

describe EDECU auto ignition system

A

turns the ignition system on for 5 seconds when Np overspeed sys activates

73
Q

describe EDECU Ng decay relight feature

A

if an engine flames out and exceeds normal Ng decay rate, the system will turn on an ignition sequence for 5 seconds
disable below 62% Ng

74
Q

describe EDECU fault diagnostic system

A

assesses signals and tells us after shutdown if something is wrong

75
Q

what is considered clearing an EDECU fault code

A

stabilize above 425 deg in fly or idle then do a normal shutdown

76
Q

EDECU fault code 15

A

may result in EDECU driven eng control failure and may damage engine

77
Q

EDECU fault codes and AFCS

A

presence of unsuppressed codes will prevent AFCS ground checks and auto blade fold because it is sending a torque code

78
Q

what makes up the ignition system

A

ignition exciter unit
2 ignition plugs

79
Q

component of the start system

A

engine starter, start valve, check valves, controls, ducting

80
Q

when does starter dropout normally occur

A

52-65%Ng

81
Q

how can we disengage the starter

A

pull down PCL
pull its CB
remove the air source

82
Q

how can you override a malfunctioning starter

A

hold it in until normal starter drop out speed

83
Q

if the apu is running can we do a crossbleed start

A

no

84
Q

what is the minimum Ng of the receiving enging for a crossbleed start prior to idle

A

24%

85
Q

What is the generally required range of Ng on the donor engine for crossbleed

A

90-94%

86
Q

where is Np sensed

A

two sensors at the top of the exhaust frame that receive electrical pulses from “teeth” brushing against

87
Q

left vs right Np sensor

A

left sends Np signal to EDECU and vertical instruments
Right is used to compute torque and is used in the Np overspeed system (still fed through EDECU)

88
Q

where does the Ng signal in the cockpit come from

A

alternator

89
Q

how many thermocouples are there

A

7

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