ENGINE CONTROL SYS Flashcards
(34 cards)
ENG CONT SYS
Engine
T700-GE-401C/D front drive turboshaft engine consisting of five sections:
1. Inlet
2. Compressor
3. Combustor
4. Turbine
5. Exhaust
NATOPS 2.1.1
ENG SYS
Inlet Section
Components:
1. Inlet Cowling
2. Swirl Frame- includes waterwash manifold
3. Front Frame
4. Main Frame
5. Accessory Section
6. Scroll Case
Airflow:
Air first passes through the inlet cowling (Heated by inlet anti-ice).
Then air passes through the swirl vanes (hollow for engine anti-icing) and splits:
- Swirled air with particulates (dirty air) is thrown outward to the collection scroll, passes over scroll vanes then dumped overboard by IPS blower
- Swirled air without particulates (clean air) is passed over the deswirl vanes, which removes rotation.
Clean air is then ready for compression
NATOPS 2.1.1.1
ENG CONT SYS
Compressor Section
5-stage axial, single-stage centrifugal rotor/stator assembly
NATOPS 2.1.1.2
ENG SYS
Combustion Section
Flow-through annular combustion chamber with 2 igniters (1 exciter), 12 fuel injectors (fuel from ODV and supplied atomized)
NATOPS 2.1.1.3
ENG SYS
Turbines
Ng:
-Drives the Compressor
- Drives the AGB
Np:
- Extends through the front of the engine (Coaxial inside of Ng)
- Connects to the high speed shaft->input module
TGT sensed between the turbines.
NATOPS 2.1.1.4-2.1.1.5
ENG SYS
Engine airflow
(After the compressor)
30% of the total airflow through the engine is used for combustion
70% is used for:
compressor inlet air temperature (T2)
compressor discharge air pressure (P3)
combustion and turbine cooling
engine oil seal pressurization
NATOPS 2.1.2
ENG SYS
Main Frame and Accessory Section
Main frame contains the oil tank and sight gauge and AGB supports.
AGB mounts to the rear of the main frame above the scroll case.
- AGB is Ng Driven
- Front face driving pads:
- Alternator
- Engine driven fuel pump
- Rear face driving pads: (IHOEs)
- IPS Blower
- HMU
- ODV
- Engine Starter
NATOPS 2.1.2.1
ENG SYS
Engine control system purpose and components
Engine Control System includes all components necessary for the proper and complete control of the engine to maintain 100% Np/Nr
Components:
- HMU
- ODV
- EDECU
- Engine-driven alternator
- Fuel flow control valves
NATOPS 2.1.3
ENG SYS
PCL Positions
OFF- PAS mechanically shuts off fuel at the shutoff valve in the HMU
IDLE- HMU auto controls start sequence fuel flow to self-sustaining combustion.
FLY- Sets maximum level of power suppliable if demanded. HMU responds to collective position via the LDS
LOCKOUT- PCL Manually controls Np/Ng. In lockout you lose: TGT limiting, Np governing, and loadsharing. Np overspeed is retained through the direct link between the EDECU and ODV.
NATOPS 2.1.3.1-2.1.3.2
NATOPS 12.2.5
Indications of failed LDS:
1. Bad Engine Idle Ng 3-4% higher than other
2. Bad Engine indicates higher Q during run-up.
3. Abnormal Q matching on initial collective pull (Q split >5% and doesnt diminish after collective is steady state. Q splits up to 26% if matched within 6 sec of steady state collective is allowed).
4. Bad engine will lag in Q.
5. In an auto, Np follows Nr above 109% or recovery Np peaks exceed 114%. Engine with failed LDS may show Q=12% with collective full down.
ENG SYS
Name the three inputs to the HMU.
- Mechanical (PAS / LDS)
HMU Responds to PAS for:
- Fuel Shutoff (OFF)
- Auto acceleration to ground IDLE (IDLE)
- Setting permissable Ng to maximum (FLY)
- Fuel Priming (LOCKOUT)
- EDECU override capability (LOCKOUT) - Electrical (torque motor servo to trim Ng speed)
- T2, P3, Ng (control variable stator vanes and anti-ice/start bleed valve position during start and normal operations, reducing the chance of compressor stall)
NATOPS 2.1.3.6
ENG SYS
Name the functions of the HMU. (RANFAN)
R - Rapid engine transient response through collective compensation. (LDS)
A - Automatic fuel scheduling for engine start (PAS)
N - Ng overspeed protection (Mechanically limits Ng to 110+/-2% via centrifugal valve)
F - Flameout and compressor stall protection (variable geometry vane and eng anti-ice/start bleed valve)
A - Acceleration limiting. (Ng Governor)
N - Ng governing (T2, P3, Ng to sked fuel flow)
NATOPS 2.1.3.7
What does the variable geometry vane servo do?
Using fuel tapped from the HMU, the servo adjust the variable inlet guide vanes and opens the anti-ice / start bleed valve preventing compressor instability. The valve opens as a function of OAT and Ng at the maximum range it will be opened when Ng is between 80.5% and 96.5%
2.1.3.5 & 2.1.10.1
ENG SYS
HMU Basic Operation
The HMU operates as a conventional gas-generator power conrol and is trimmed by the EDECU.
- Fuel enters through engine driven boost pump.
- Some fuel is tapped to:
- Actuate the metering servo
- Actuate the variable geometry vane servo (VGS) and start/bleed valve
- Amplify signals that influence fuel fow and VGS position
- The metering valve schedules engine fuel flow commensurate to the current power demand.
- The metering valve is trimmed by the torque motor servo in response to the EDECU.
- LVDT provides a feedback signal to null the TMS input. This stabilized the metering valve and prevents engine oscillation/hunting.
2.1.3.7
ENG SYS
Actual level of engine power
The actual level of engine power in FLY is normally more than required by the helicopter. This is because:
1. Fail-safe to high power- TMS trims power down so if the engine electrical system/TMS fails there is no damage or stall.
2. Power available with OEI- If one engine fails, the other can increase power to carry the load at the given LDS setting.
2.1.3.7
Name the four main functions of the ODV.
“Provides, Prevents, Purges, Primes”
- Provides main fuel flow to the 12 fuel injectors during engine start and operation.
- Returns fuel back to the HMU if the Np overspeed is energized or if the EDECU hot start preventer is activated.
- Purges the main fuel manifold overboard, after engine shutdown, to prevent coking of the fuel injectors.
- Traps fuel upstream, which keeps the fuel/oil heat exchanger full, so that system priming is not required prior to the next start.
2.1.3.8
ENG SYS
Engine Limiting
Engine Limiting- reaching a governing condition as a part of the engine design.
- TGT Limiting- EDECU stops fuel flow to engine to protect from overtemp.
- HMU Fuel Flow limiting- Either a restriction due to the physical size of the fuel lines or Engine Pressure Ratio limiting- fuel flow is limited as a function of Ng and OAT to prevent compressor damage.
- In any case increasing collective will cause a droop in Nr prior to reaching a ch 4 limit.
Parameter Limiting- Reaching a NATOPs (Ch. 4) limit.
- Torque limited, TGT limited, Ng Limited
- Increasing Collective/ Power will cause limit exceedence, Nr will remain at 100%.
Restricted Engine Fuel Flow (REFF) is when clogged fuel lines limit the engine before a limited or design limiting. This is a degraded state and is discovered in FCF procedures.
2.1.3.9
ENG SYS
EDECU
Enhanced Digital Electronic Control Unit- Trims the HMU to maintain Np governing while TGT limiting.
2.1.4.2
What inputs does the EDECU take from the cockpit?
- Engine speed trim switch
- Contingency power switch
- Engine overspeed test A/B
2.1.4.2
What inputs does the EDECU take from the helo?
- Torque from the other EDECU
- Np demand
- 400-Hz backup power
- HMU (via LVDT)
2.1.4.2
Name the functions of the EDECU.
(4N CHEF TASTED)
N - Np governing
N - Np overspeed protection
N - Np overspeed test
N - Ng decay relight feature
C - Contingency power
H - Hot start prevention
E - Engine load sharing
F - Fault diagnostic system
T - TGT limiting
A - Auto-ignition system
S - Cockpit Signals
T - Transient droop improvement
E - Engine speed trim
D - EDECU lockout
2.1.4.3
Np governing
Np sensor located on left side of the power turbine sends signal to EDECU
actual vs. a reference Np is compared to compute a speed error
Np overspeed protection
when Np > 120%, a signal is sent from EDECU to ODV, diverting fuel to the inlet of the HMU therefore causing a flameout
Np overspeed test
activated via A/B, pressed together Np overspeed limit is re-referenced to 96%
Ng decay relight feature
if the engine flames out and exceeds Ng deceleration rate, the auto-ignition system will turn on igniters for 5 seconds in an attempt to relight the engine
this feature is disabled below 62% Ng
