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Eng Control System Flashcards

1
Q

NATOPS Chap 2 Engine Control System The Eng control system….

A

“Includes all components necessary for the proper and complete control of the eng to maintain a constant Np/Nr”

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2
Q

NATOPS Chap 2 Engine Control System What are the major components?

A

HMU, EDECU, engine driven Alternator, ODV, and a series of fuel flow control valves

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3
Q

NATOPS Chap 2 Engine Control System What does the Eng control quad consist of?

A

2 PCLs, two fuel slectors, two T handles, and a rotor brake interlock

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4
Q

NATOPS Chap 2 Engine Control System What shuts off fuel with the PCL off?

A

The Power Available Spindle shuts off fuel at the shutoff valve w/i the hmu

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5
Q

NATOPS Chap 2 Engine Control System What do you lose with the PCL in lockout?

A

TGT Limiting, NP governing, and load sharing. You retain Np overspeed protection system

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6
Q

NATOPS Chap 2 Engine Control System With the rotor brake on, can you advance a PCL to fly?

A

No, there is a solenoid on the quadrant that activates a mechanical locking device to prevent the pcl from being advanced to fly. If the Rotor Brake is released, the solenoid energizes and unlocks the PCLs

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7
Q

NATOPS Chap 2 Engine Control System What connects the HMU and collective?

A

The load demand system.

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8
Q

NATOPS Chap 2 Engine Control System What is the Engine driven fuel boost pump designed to do?

A
  1. Provide reliable suction feed from the aircraft fuel tank to the engine, minimizing vulnerability and fire hazard in the event of damaged fuel lines 2. Provide discharge pressure to satisfy min inlet pressure requirement of the HMU or Hi Pressure fuel pump
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9
Q

NATOPS Chap 2 Engine Control System What doesn’t the fuel filter filter?

A

Water

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10
Q

NATOPS Chap 2 Engine Control System What does the HMU contain?

A

Hi-Px fuel pump, Ng governor, metering valve, LVDT, torque motor servo, variable geometry vane servo, vapor vent, and shutoff valve

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11
Q

NATOPS Chap 2 Engine Control System Fuel is tapped off to operate servos in the HMU for? (FSS)

A
  1. Fuel— Positioning a metering valve for proper fuel flow to eng 2. Servo— position a servo piston that actuates var. geometry vane servo and start bleed valve 3. Signals— amplifying signals (T2, P3, Ng) that influence fuel flow and variable geometry servo position
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12
Q

NATOPS Chap 2 Engine Control System Inputs to HMU (mechanical vs. Electronic)

A

2 mechanical: 1. LDS directly coordinates Ng speeds via collective position 2. Position of PCL manipulates the PAS at the HMU setting the desired power 1 Electronic: Signal from DECU actuates the torque motor servo in HMU to trim Ng speed for power turbine control and load sharing

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13
Q

NATOPS Chap 2 Engine Control System The HMU responds to the PCL for: (FSSFD*)

A
  1. Fuel shutoff 2. Setting eng start fuel flow w/ auto accel to ground idle 3. Setting permissable NG up to max 4. Fuel Priming 5. DECU Lockout *The HMU also responds to T2, P3, and Ng. These inputs aid the HMU in controlling variable stator vanes and anti-ice/start bleed valve position during engine start and normal operation, reducing the chance of compressor stall
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14
Q

NATOPS Chap 2 Engine Control System What does the HMU control to reduce the chance of compressor stall?

A

The HMU controls variable stator vanes and anti-ice/start bleed valves during eng start and normal ops.

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15
Q

NATOPS Chap 2 Engine Control System How does fuel flow in HMU

A

The fuel first enters the hi Px pump and is then routed to the metering valve

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16
Q

NATOPS Chap 2 Engine Control System What does the metering valve do?

A

Schedules engine fuel flow commensurate to current power demand and is trimmed to the required level by the torque motor servo via the EDECU

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17
Q

NATOPS Chap 2 Engine Control System How does the HMU respond to the EDECU

A

The HMU uses the LVDT to provide feedback and null the torque motor servo input which stabilizes the metering valve to prevent eng hunting

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18
Q

NATOPS Chap 2 Engine Control System When and how does the Ng overspeed valve trip?

A

If the Ng servo within the Ng governor reaches a position corresponding to an overspeed, a spring-loaded ball valve ports fuel pressure causing the minimum pressure valve to secure flow to the engine. The Ng overspeed valve is set to trip at 110+/- 2% Ng

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19
Q

NATOPS Chap 2 Engine Control System With the PCL in FLY the HMU..

A

Intentionally schedules higher-than-required power level for two reasons: 1. Fail-safe to high power 2. Power avail with OEI

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20
Q

NATOPS Chap 2 Engine Control System Why Fail safe to high power?

A

With a loss of torque motor servo from DECU, the fuel schedule returns to highest power level. This prevents engine damage and engine stall in the event of loss of all electrical power to torque motor

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21
Q

NATOPS Chap 2 Engine Control System OEI?

A

With the loss of one engine, the other Ng can increase power sufficiently up to its limit (contingency power) to carry the load at the LDS setting.

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22
Q

NATOPS Chap 2 Engine Control System HMU provides: (RANNAF)

A
  1. Rapid engine transient response thru collective compensation 2. Automatic fuel scheduling for engine start 3. Ng Overspeed Protection- if Ng reaches an ovrspeed condition, a centrifugal valve secures fuel flow to engine. 4. Ng governing- HMU receives inputs to schedule fuel for min flow, max flow, and variable geometry vane control 5. Acceleration Limiting- The Ng governor ensures any PCL motion will result in safe engine operation and not cause engine damage. An inadvertant shutdown will not occur during PCL motion 6. Flameout and Compressor stall protection- HMU does this via variable geometry vane position and opens anti-ice/start bleed valve to prevent compressor instability
23
Q

NATOPS Chap 2 Engine Control System ODV functions (PPRT)

A
  1. Provides fuel flow to 12 fuel injectors during engine start and operation
  2. Purges main fuel mainfold overboard, after engine shutdown to prevent coking of fuel injectors.
  3. Returns fuel back to HMU if Np overspeed is energized or if the DECU hot start preventer is activated
  4. Traps fuel upstream so priming is not rq’d prior to next start
24
Q

NATOPS Chap 2 Engine Control System What are the two types of limiting?

A
  1. Engine Limiting (TGT or HMU-fuel flow limiting, etc)
  2. Parameter Limiting (as governed by Chap 4 ex: Ng limited, Torque Limited, etc)
25
Q

NATOPS Chap 2 Engine Control System TGT vs. Fuel Limiting

A

TGT limiting= reaching either IRP or CRP function within the EDECU Fuel Limiting-HMU limits fuel, and the Ng value will be below the Chap 4 limits.

26
Q

NATOPS Chap 2 Engine Control System Types of Fuel Flow limiting (2)

A
  1. Depending on Temp and Pressure altitude, the amount of fuel flow provided is limited by the size of the fuel lines w/i HMU and ODV. This condition can occur at high power settings with C Power selected. 2. EPR (Eng Pressure ratio). The HMU is designed to protect the compresser section by limiting the fuel flow as a funciton of Ng and Ambient temperature. This can occur during cold ambient temps at any pressure altitude
27
Q

NATOPS Chap 2 Engine Control System How is the EDECU cooled?

A

Via Scavenge airflow

28
Q

NATOPs Chap 2 Engine Control System Summary How does the system functionally split between the HMU and EDECU?

A

The HMU provides functions essential to safe engine operations, while the EDECU performs a fine trim to reduce pilot workload

29
Q

NATOPS Chap 2 Engine Control System Np overspeed test

A

Activated by OVSPD A and B buttons. When both are pressed, the Overspeed limit is re-referenced to 96% Np

30
Q

NATOPS Chap 2 Engine Control System Ng decay relight feature

A

If an eng flames out for any reason and exceeds a specified Ng decel rate, the auto ignition system will engage for 5 sec in attempt to relight the eng. This is disabled below 62% Ng

31
Q

NATOPS Chap 2 Engine Control System Np Governing

A

Sensor provides Np speed to Decu. Actual Np is compared to a refernce Np to compute speed error input signal

32
Q

NATOPS Chap 2 Engine Control System Np Overspeed Protection

A

Overspeed system is comprised of redundant circuits which rely on a signal from Np overspeed and torque sensor. Overspeed system is actuated at 120% Np. When Np exceeds 120% a signal is sent from the EDECU to the ODV, diverting fuel to the inlet of the HMU, causing engine flameout.

33
Q

NATOPS Chap 2 Engine Control System Manual Contingency Power

A

TGT limit can be increased to 903. The CRP will limit TGT to 891+- 10. By turning the switch on, a signal is sent to the EDEU to allow TGT to increase to 903, however, max crp limiter will prevent further increase in fuel flow to the engine at 891 +- 10

34
Q

NATOPS Chap 2 Engine Control System Hot Start Prevention

A

Detects a hot start when TGT exceeds 900 with Ng below 60, and Np below 50 and automatically stops fuel flow by tripping the ODV. Fuel flow is restored when TGT <300 or after 25 seconds (whichever is first). This can be disabled by pressing and holding the ENG OVSP test A or B for the duration of the start sequence

35
Q

NATOPS Chap 2 Engine Control System Eng Load Sharing

A

Torque signals are compared between the engine via the respective DECUs. A torque error signal is generated if one engine torque is less than the other. The torque matching system will increase the power on the lower engine while not directly affecting the higher torque engine

36
Q

NATOPS Chap 2 Engine Control System Fault Diagnostics

A

If a failure occured while the engine was operating, the failed component will be identified via a preset code. Once both engines are shutdown, the codes will flash 4 sec on 2 sec off in priority of lowest to highest. They can be surpressed by pressing either one of the ENG OVSPD buttons.

37
Q

NATOPS Chap 2 Engine Control System TGT Limiting

A

The EDECU incorporates a max rated power (MRP), the TGT is limited to 866+-10. If power demand is increased further, Np/Nr will droop below 100%; Np governing will be sacrificed to protect the engine against overtemperature

38
Q

NATOPS Chap 2 Engine Control System Auto Ignition System

A

When an overspeed condition is reached and during the overspeed test, the overspeed valve located in the ODV is opened to reroute fuel flow to the HMU inlet. The system will continue to cycle until Np/Nr is controlled

39
Q

NATOPS Chap 2 Engine Control System Cockpit Signals

A

Provides Np, TGT, and torque signals to the DTC (Data Concentrator) for the cockpit display

40
Q

NATOPS Chap 2 Engine Control System Transient Droop Improvement

A

This system is designed to initiate Np acceleration early by using anticipator signals from the Nr sensor. Circuits in DECU increase fuel flow to engine via HMU torque motor servo at low torque settings, when collective demand is increased rapidly or in the event of rapid Nr decay.

41
Q

NATOPS Chap 2 Engine Control System Engine speed Trim

A

Supplies a reference electrical signal to the DECUs for controlling Np between 96-101%

42
Q

NATOPS Chap 2 Engine Control System Dual-engine Auto-contingency power

A

Dual Engine auto-contingency power allows the EDECU to bypass the 10-min TGT limit of 866+- 10, and limit the aircraft at the c-power TGT limit of 891 +- 10. For this feature to activate, one or more of the following conditions must exist: 1. Np drops below 96% 2. Greater than 3% droop between reference power turbine speed (Np and actual Np reference set point 3. Greater than 5% per second Np droop rate exists with Np less than or equal to Np reference set point.

43
Q

NATOPS Chap 2 Engine Control System Auto-contingency power

A

The EDECU provides auto c-power, enabled in OEI Conditions. When the Torque from one engine is below 50%, the opposite engine EDECU will automatically reset the TGT limiter from 866 +-10 to a max limit of 891 +- 10. The #1/2 ENG CON advisories will not illuminate to indicate that c-power has been activated

44
Q

NATOPS Chap 2 Engine Control System EDECU Lockout

A

PCL is used to manually control Ng and Np. This deactivates TGT Limiting, but the Np overspeed protection is retained.

45
Q

NATOPS Chap 2 Engine Control System CEDECU (Identification)

A

Blackhawk codes= 15+- 2.9% Romeo= 35 +- 2.9%

46
Q

NATOPS Chap 2 Engine Control System How do retain the Np overspeed protection system when the PCL is in lockout?

A

Np overspeed protection is retained via a direct link between the EDECU and ODV.

47
Q

NATOPS Chap 2 Engine Electrical System What components are provided ac power via the alternator?

A

Ignitor assembly, EDECU, and Ng signal to the vertical instruments?

48
Q

NATOPS Chap 2 Engine Control System What happens when the PCL is moved to the IDLE position?

A

The HMU automatically controls start sequence fuel flow allowing the engine to achieve self-sustaining combustion.

49
Q

NATOPS Chap 2 Engine Control System With the PCL in FLY, how does the HMU respond to the collective?

A

The HMU responds to the collective position via the LDS, to automatically control engine speed and provide required power. When the PCL is moved to LOCKOUT and then to some intermediate position, the engine will still vary power in response to collective position.

50
Q

NATOPS Chap 2 Engine Control System What is a limit condition defined as?

A

A limit condition may be defined by reaching a governing condition as part of the T700 design. This type of limit condition is referred to as engine limiting because the engine control system is preventing further increases in power output. A limit condition may also be defined by reaching a maximum value prescribed in Chapter 4. This is called parameter limiting.

51
Q

NATOPS Chap 2 Engine Control System What does Torque limited mean?

A

Torque limited is a transmission limit defined by reaching a NATOPS Chapter 4 torque limit. the pilot is responsible for maintaining torque within Chapter 4 limits under all conditions

52
Q

NATOPS Chap 2 Engine Control System What does TGT-Limited mean?

A

It is defined by reaching a NATOPS Chapter 4 TGT Limit prior to reaching EDECU IRP, MRP, or CRP functions or in the event of a malfunction EDECU (when there is no TGT-limiting)

53
Q

NATOPS Chap 2 Engine Control System What does Ng limited mean?

A

An engine limit defined by reaching a NATOPS Chapter 4 Ng limit. the pilot is responsible for maintaining Ng within Chapter 4 limits under all conditions. If an engine is Ng limited and the collective is increased further, Nr will remain at 100% and Ng will increase (along with TGT and torque). Unlike conditions of fuel-flow limit, increasing collective while Ng limited may result in exceeding either transient or max Ng and/or torque limits.

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