Aircraft Systems Flashcards
What are the 4 sections of the engine?
Cold Section
Hot Section
Power Turbine Section
Accessory (Gearbox) Section
What are the functions of the HMU?
PM CAN VDTO
Pumps fuel at a high pressure (400-832 psi, 300 psi idle) for better atomization.
Meters fuel via the LDS, PAS, and DEC (Torque Motor) inputs.
Collective pitch compensation through the LDS. When collective is moved, NG is reset for immediate NP response.
Accel/decel fuel flow limiting to prevent compressor stalls, engine damage, and flameout.
NG limiting (will occur before TGT limiting in extreme cold weather) and NG shutdown (at 110% NG).
Variable Geometry Positioning of the inlet guide vanes for optimum performance.
DEC Lockout via the PAS to bypass torque motor inputs from the DEC.
Torque Motor input to trim NG output.
Opens the vapor vent for fuel priming.
What are the functions of the ODV?
HOPS
Hot start prevention (shuts off fuel when activated by hot start preventer).
Overspeed Protection (limits fuel flow when signal is sent from DEC).
Purges main fuel manifold and nozzles at shutdown to prevent coking.
Sequencing of main fuel for engine starting and operation.
What are the 3 windings in the alternator?
NIP
NG signal to the cockpit (green)
Ignition power to the exciters during start (black)
Power for DEC (yellow)
What happens during a complete alternator failure?
Loss of NG cockpit indication with corresponding ENG OUT warnings and audio (NG < 55%). NOTE: There will be no loss of NP1 and NP2, or Q, and Overspeed Protection is still available due to DEC being backed up by airframe power.
What are the functions of the DEC?
FT (TINT) HHOT
Fault Indication through the TQ indicator.
Trims HMU output through the torque motor based on:
- TGT limiting at 897+/-9 Dual Engine or 903+/-10 when other engine is below 50% Q (DEC, sooner with EDECU).
- Isochronous NP Governing to maintain NP at the reference set by the pilot.
- NP reference from the cockpit via the Eng Speed Trim Switch (INCR/DECR) from 96-100%
- Torque matching/Load sharing increases power on the low engine up to 3% above the reference.
Hot Start Preventer tells ODV to shutoff fuel when TGT 900 degrees Celsius, NG<60%, NP<50%.
History Counter Signal.
Overspeed Protection at 120%+/-1%.
Transient Droop Compensation. 4-1 improvement to reduce transient droop.
When does the EDECU switch from the 10-minute TGT limiting value to the higher 2.5-minute TGT limiting value?
When any of the following occur:
1) NP drops below 96%
2) Greater than 3% droop between reference NP and actual NP
3) Greater than 5% per second NP droop rate exists and NP less than or equal to NP reference.
What functions are locked out when going to (DEC) lockout?
1) TGT limiting
2) Isochronous NP Governing
3) NP reference from the cockpit
4) Torque Matching/Load Sharing
If an engine fails to the highside (DEC failure) will the other engine RPM rise with it? For how long?
Yes, but only until NP is 3% above the reference NP.
In what 3 (emergency) situations will TGT limiting not work?
Engine starts, compressor stall, lockout
Is the TGT temp displayed in the aircraft the actual temperature of the engine? Why?
No, it has a -112 degree C bias (the engine is running hotter than the indication).
What parameters will activate HSP? Can it be overridden?
TGT>900 C, NG<60%, and NP<50%
It can be disabled for emergency starts by pressing and holding the overspeed test button (TEST A/B) for the engine being started during the start sequence.
What is the main function of the MMU?
Minimize inherent control coupling. (Basically, decreased pilot workload).
What are the 4 types of mixing the MMU provides, what do they compensate for, and what input does it provide?
- Collective to Pitch: Compensates for the rotor downwash on the stabilator. Provides forward input to the rotor as collective is increased and aft as it is decreased.
- Collective to Roll: Compensates for translating tendency. Provides left input to rotor as collective is increased, right as it is decreased.
- Collective to Yaw: Compensates for torque effect. Increases TR pitch as collective is increased, and decreases TR pitch as collective is decreased.
- Yaw to Pitch: Compensates for the vertical thrust component of the canted TR. Provides aft input rotor as TR pitch is increased, and forward as TR pitch is decreased.
What is electronic coupling? What does it compensate for?
Collective/Airspeed to Yaw - helps compensate for the torque effect. Decreases TR pitch as airspeed increases and TR and cambered fin become more efficient. Maximum mixing occurs from 0-40 knots, then decreases to 100 knots, after which no mixing occurs.
What controls electronic coupling (what is it a function of?)
2 FCC
What are the speeds associated with electronic coupling?
- 0-40 knots: Maximum mixing
- 40-100 knots - Mixing decreases
>100 knots: No mixing
What are the 5 subsystems of AFCS?
1) SAS
2) Trim
3) FPS
4) Coupled Flight Director
5) Stabilator
What is the central component to the AFCS system (where the AFCS systems gain their information/signals to operate)?
1 and #2 Flight Control Computers (FCC)
Which FCC is the only FCC that sends signals to the trim actuators?
The #2 FCC
How does each FCC know the status of the other?
The Cross Channel Data Link (CCDL)
Airspeed, Barometric Altitude, and Barometric Rate are provided to the FCCs through which system?
Air Data Computers
The primary function of the _____ is to compute attitude, heading, present position, and turn rate.
EGI
What are the inner loop and outer loop systems in the FCCs?
Inner loop - SAS
Outer loop - Trim