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H2P > DECU / EDECU > Flashcards

DECU / EDECU Flashcards

1
Q

T2

A

Compressor inlet temp

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2
Q

P3

A

Compressor discharge pressure

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3
Q

HMU responds to Collective position through LDS for what

A

Coordinates Ng speeds

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4
Q

HMU responds to PCL through PAS for:

A 
Fuel shutoff
Engine start fuel glow w/ automatic acceleration to ground idle
Setting Ng up to permissible max
Fuel Priming
DECU override (Lockout)
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5
Q

HMU responds to T2, P3, Ng for

A

to control variable stator vanes and anti-ice / start bleed valve position and max/min flow

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6
Q

Feedback signal from HMU to decu

A

through LVDT (Linear variable displacement transducer) to null torque motor servo and stabilize metering valve

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7
Q

Ng overspeed valve trips at ____

A

110 +_2

Spring loaded ball valve ports fuel pressure cuasing the minimum pressure valve to secure flow

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8
Q

PAS sets max available Ng, and gives engine power more than required for 2 reasons

A
  1. Fail safe to high power, torque motor reduces power normally, but if electrical power to torque motor is lost it returns to the highest so you can adjust with the PCLs
  2. Power available with OEI
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9
Q

HMU provides

A

Rapid engine transient response through collective compensation
Acceleration Limiting - Rapid PCL movement won’t damage engines
Ng overspeed protection 110 +_ 2
Ng governing through T2, P3, Ng
Automatic fuel for engine start
Flameout and compressor stall prevention through anti-ice/start bleed valves

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10
Q

What opens the shutoff valve in HMU to ODV

A

PCL moving to IDLE

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11
Q

Four functions of ODV, overspeed drain valve

A

Traps fuel upstream which keeps fuel/oil heat exchanger full so that priming is not necessary
Returns fuel back to HMU if Np overspeed is energized or hot start
Main fuel flow to 12 fuel injectors
Purges main fuel manifold overboard after shutdown to prevent coking

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12
Q

DECU control parameters

A

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

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13
Q

Inputs to DECU from cockpit

A

ENG SPD Trim switch
CONTGCY PWR switch
ENG OVERSPEED TEST A and B

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14
Q

Inputs to DECU from helicopter

A

Torque demand from other DECU
Np demand
400 hz backup power
HMU (LVDT)

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15
Q

Signals from DECU to cockpit

A

Torque
Np
TGT
C power

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16
Q

DECU functions

A 
400 hz
Np overspeed protection
Np governing
Np overspeed test
Ng auto decay relight feature
C-power
Hot start prevention
Engine load sharing
Fault diagnostics
TGT limiting
Auto-ignition
Signals
Transient droop improvement
Eng spd trim
DECU lockout
17
Q

Np governing

A

Actual Np is compared to a reference Np

18
Q

Np Overspeed protection

A

actuated at 120 Np, signal to ODV, diverts fuel to HMU causes engine flameout
W: ENG OVSP circuit breaker shall not be reset in flight, may result in engine failure by inititiating overspeed

19
Q

TGT limiting

A

When TGT reaches 851 IRP or 878 MRP EDECU prevents increase in fuel flow.
839 +_ 10 IRP
866+_10 MRP

20
Q

______ will be sacrificed to protect the engine against overtemperature

A

Np governing

21
Q

Engine load sharing

A

Compares torque signal from other DECU, increases power on lower engine

22
Q

Engine Speed trim

A

INCR / DECR

Controls Np between 96 and 101 percent

23
Q

Contingency power

A

Allows TGT to increase to 903
CRP limiter will prevent further fuel flow at 891+_10

EDECU auto C-power enabled for OEI when one engine is below 50% trq, advisories will no illuminate

24
Q

Np overspeed test

A

Np overspeed limit is re-referenced to 96 percent

25
Q

DECU lockout

A

PCL manually controls Ng and Np
Lose TGT limiting, Np governing, and load sharing
IDLE then fly to regain

26
Q

Hot start prevention

A

When TGT exceeds 900 with Ng below 60 and Np below 50, stops fuel flow by tripping ODV
Fuel flow restored when TGT less than 300 or 25 seconds
Can be disabled by holding OVSP TEST A and B

27
Q

Fault diagnostic system

A

Codes
Can be suppressed and recalled by pressing either OVSPD test
Cleared and verified after engine at FLY

28
Q

400 Hz airframe power

A

Decu powered by either engine alternator or 400 Hz aircraft power via ENG OVSP circuit breaker

29
Q

Transient droop improvement TDI

A

Anticipates signals from TDI Nr sensor on left accessory module and collective position sensor in the mixing unit

30
Q

Auto-ignition

A

Np overspeed, when Np drops below 120 the system closes the overspeed valve and turns on the igniters for 5 seconds
Continues to cycle until Np/Nr is controlled
Yaw kcik may be felt each relight

31
Q

Ng decay relight feature

A

Auto ignition if engine flames out, turns on igniters for 5 seconds
Relight feature disabled below 62% Ng

H2P (22 decks)

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