Powerplant and Related Systems

Question 1

Airflow

Answer 1

Inlet Cowling
Swirl Vanes
Inlet Partical Separator (IPS)
Deswirl Vanes
5 Stage Axial and Single-Stage Centrifugal Compressor
Combustion Section (Annular)
Ng 2-stage turbine
TGT Harness
Np 2-stage turbine

30% of air is used for combustion
70% is used for the following:
1. Combustion and Turbine Cooling
2. T2
3. P3
4. Engine Oil Seal Pressurization

Question 2

Turbine Interaction

Answer 2

Coaxial: Np in the Ng shaft

Question 3

How is power transmitted from engine to transmission?

Answer 3

Ng and Np are pneumatically connected from exhaust from the combustion section.

Np rotates coaxially within Ng.

Np connects to the high speed shaft (Diagram mentions something about a “power output drive shaft”)

“Power output drive shaft” connects to diaphragm coupling.

Diaphragm coupling to input module.

Question 4

Accessory Section

Answer 4

Driven by a rotor via a radial drive from the Ng drive shaft.

Rear face:

1. Starter
2. HMU
3. IPS Blower
4. ODV

Front face:

1. Alternator
2. Engine Driven Fuel Boost Pump
3. Fuel/Oil HXC
4. Fuel filter
5. Oil filter

Question 5

Interaction of HMU and DECU

Answer 5

HMU provides for convention mechanical gas generator control while the DECU fine tunes engine operation reducing pilot workload and satisfies the requirements of the power turbine load.

Question 6

Engine Control Quadrant

Answer 6

PCLs (OFF, IDLE, FLY, LOCKOUT), Fuel Selectors, Fire T-Handles, Rotor Brake Interlock Override

Question 7

Inputs to the HMU

Answer 7

PAS, LDS, TMS (responds with LVDT to precent engine oscillation and hunting), T2, P3, and Ng

Technically fuel is also an input.

Question 8

HMU response from PCL

Answer 8

Go through PCL positions:

OFF: fuel cutoff
IDLE: automatic fuel scheduling for engine start
FLY: maximum permissible Ng
LOCKOUT: Fuel priming
LOCKOUT: DECU LOCKOUT (loss of TGT limiting, Np governing, and load sharing; Np overspeed is retained via direct link between DECU and ODV)

Question 9

Engine Limiting

Answer 9

Occurs to protect engine components and/or by reaching a maximum possible output based on ambient conditions.

Question 10

Parameter Limited

Answer 10

A limit condition defined by reaching a maximum value prescribed by Chapter 4.

Question 11

Engine Driven Fuel Boost Pump

Answer 11

Provides reliable suction feed and provides discharge pressure to satisfy inlet pressure requirement of the HMU.

Question 12

HMU Provides:

Answer 12

1. Rapid engine transient response through collective compensation.
2. Automatic fuel scheduling for engine start.
3. Ng overspeed protection: mechanically limits Ng to 110 +/- 2% via a centrifugal valve.
4. Ng governing: HMU receives T2, P3, and Ng inputs from their respective sensors which are used to schedule fuel for min flow, max flow, and VG vane control.
5. Acceleration limiting: Ng governor ensures that any PCL motion will result in safe engine operation and will not cause damage. Except for intentional shutoff of the PCL, an inadvertent shutdown will not occur during PCL motion.
6. Flameout and compressor stall protection: HMU adjust VG vane position and opens the anti-ice start bleed valve to prevent compressor instability.

Question 13

ODV

Answer 13

1. Provides main fuel flow to the 12 fuel injectors
2. Purges the main fuel manifold overboard, after shutdown shutdown, to prevent coking.
3. Traps fuel upstream so that priming is not required.
4. Returns fuel back to the HMU if the Np overspeed is energized or if the DECU hot start preventer is activated.

Question 14

DECU (4N CHEF TASTED) and (TAD)

Answer 14

• 400 Hz: either airframe power or alternator
• Np governing: Np sensor on left side of engine is compared to a reference Np
• Np overspeed: Np overspeed and torque sensor on right side activates at 120%; fuel is diverted from ODV to HMU
• Np overspeed test: Np overspeed value is changed to 96%
• Ng decay relight: if engine flames out and exceeds a decay rate, the auto-ignition system fires the igniters for 5 seconds; disabled below 62% Ng
• C-pwr: TGT limit increased to 903; however, CRP limiter is 891 +/- 10
• Hot start prevention: detects hot start when TGT exceeds 900 with Ng below 60 and Np below 50; fuel flow is restored when TGT goes below 300 or after 25 seconds; disabled by pressing and holding either overspeed test button during start
• Engine Load Sharing: torque matching system increases power on the lower torque engine
• Fault diagnostic: DECU error codes; can be suppressed and recalled from overspeed test buttons
• TGT limiting: TGT approaching 851 (839 +/-10) prevents fuel flow causing Np/Nr droop; Np governing sacrificed to prevent overtemp
• Auto-ignition: after overspeed, when Np drops below 120%, auto-ignition system will fire igniters for 5 seconds
• Cockpit signals: provides Np, TGT, and torque signals to DTC
• TDI: uses TDI sensor and collective position to initiate power turbine response early
• Engine Trim: INCR/DECR between 96 and 101 Np
• DECU LOCKOUT: loss of TGT limiting, Np governing, and load sharing; Np overspeed protection is retained by DECU interaction with ODV
• TGT limiting: increased to 878 (866 +/- 10) for MRP
• Auto-C-power: when torque of one engine drops below 50% or 180 ft-lbs sets opposite DECU from 866 to 891.
• Dual auto c-power: newer versions of CEDECU active c-power when excessive Nr droop is sensed