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
What are some of the characteristics of the inner loop of the FCCs?
Fast in response, limited in authority, does not move the flight controls.
How much control authority does the outer loop of the FCCs have and at what rate?
100% at a rate of 10% per second.
What are static and dynamic stability?
Static stability is long term and is the tendency to return to the pilot’s desired heading, attitude, or airspeed.
Dynamic Stability is short term and is the tendency to resist movement.
What does SAS provide? in what axes? What type of stability does it provide (dynamic/static)?
SAS enhances dynamic stability by providing short term rate dampening in the pitch, roll, and yaw axis.
What are the brains of SAS1? SAS2?
SAS 1 - #1 FCC
SAS 2 - #2 FCC
What is the muscle for SAS?
Pitch, Roll, and Yaw SAS Actuators
How much control authority does SAS have? What if one SAS fails?
5% each for a total of 10%. If one SAS fails, the other will double its gain, but only to its max of 5% control authority.
When will the SAS OFF caution appear?
Loss of actuator pressure, or if both SAS1 and SAS2 are turned off.
How is a SAS malfunction identified?
Erratic motion in the helicopter.
What axes (motions) does Trim work in?
Pitch, Roll, Yaw, Collective
What is the muscle for Trim?
3 Trim Actuators (Roll, Yaw, Collective), and 1 Trim Servo (pitch).
What system monitors Trim?
2 FCC
What must be on for Trim to be fully operational (because of yaw trim)?
SAS/BOOST
What are the 3 functions of Trim?
Force Gradient, Muscle for FPS, and Electronic Coupling
If a Trim actuator becomes jammed, what allows the controls to still be moved? What force is required?
Slip clutches allow the flight controls to be moved if an actuator becomes jammed. It requires 80 lbs maximum in Yaw, 13 lbs maximum in Roll, and 22 lbs maximum in collective.
What type of actuators are used for pitch, roll, yaw, and collective trim?
Pitch - Electrohydromechanical actuator.
Roll, Yaw, Collective - Electromechanical actuators.
What does FPS provide? In what axes? What type of stability does it provide (dynamic/static)?
It provides a basic autopilot function in the Pitch, Roll, and Yaw axis. Provides long term static stability.
When coupled with trim, how much control authority does FPS have?
100%
What systems must be on for FPS to work?
SAS/BOOST, Trim, SAS 1 and/or SAS2. Stabilator is not required, performance will increase when operated in the auto mode.
What basic autopilot functions does FPS provide below 50 kts? Above 50 kts?
Below 50 kts:
Pitch: Attitude Hold
Roll: Attitude Hold
Yaw: Heading Hold
Above 50 kts:
Pitch: Airspeed/Attitude Hold
Roll: Attitude Hold
Yaw: Heading Hold or Turn Coordination
What are the brains for FPS? Muscle?
Brains - FCCs
Muscle - Trim Actuators
When/How is turn coordination activated?
When roll attitude is greater than 1 degree for any of the following:
1) Lateral cyclic greater than 1/3 inch stick displacement from trim.
2) Cyclic TRIM REL is pressed.
3) Roll attitude is beeped beyond 2.5 degrees bank angle.
What is the purpose of the stabilator?
Enhance the handling qualities of the helicopter and improves static and dynamic stability about the pitch axis.
What are the 5 functions of the Stabilator?
SCALP
Streamlines w/rotor downwash at low airspeeds (below 30 knots) to minimize nose up attitude.
Collective Coupling to minimize pitch attitude excursions due to collective inputs.
Angle of Incidence decreases above 30 knots to improve static stability.
Lateral Sideslip to Pitch coupling to reduce susceptibility to gusts. Stabilator goes up for nose right, and down for nose left.
Pitch Rate Feedback to improve dynamic stability. Dampens pitch excursions due to turbulence or “G” forces.
What are the brains for the Stabilator? Muscle?
Brains - 2 FCCs.
Muscle - 2 Stabilator Actuators.
On the MFD, What does it mean when the stabilator indicator is white, yellow, and red?
White: AUTO MODE
Yellow: MANUAL MODE
Red: When stabilator fail flag is displayed
What is the purposed of the Flight Director?
Provide autopilot functions
The steering commands derived from the navigation and flight instruments allow FPS to perform what tasks with a coupled Flight Director?
MMMAAA
Maintain a desired heading
Maintain fixed altitude and/or airspeed
Make a programmed accel/decel and climb/descent to a predetermined airspeed or altitude
Acquire a selected course
Acquire and track localizer and glide slope for ILS approach
Acquire and track an MFS route
What are the FD/DCP engagement parameters for the IAS (airspeed hold) mode?
50-150 KIAS
What are the FD/DCP engagement parameters for the HDG (heading hold) mode?
Above 50 KIAS
What are the FD/DCP engagement parameters for the ALT (barometric altitude hold) mode?
Above 50 KIAS
What are the FD/DCP engagement parameters for the RALT (radar altitude hold) mode?
0-1500 ft AGL
What are the FD/DCP engagement parameters for the VS (vertical speed hold) mode?
0-2000 fpm AND above 50 KIAS
What are the FD/DCP engagement parameters for the GA (go around) mode, and what will it provide?
Any airspeed or hover
Gives: 70 KIAS, 750 FPM climb.
What are the FD/DCP engagement parameters for the ALTP (altitude pre-select) mode?
Can be armed in flight or on the ground (will capture within 300’)
What are the FD/DCP engagement parameters for the FMS Navigation mode, and what will it provide?
Above 50 KIAS:
Provides roll command to follow the FMS flight plan.
What are the FD/DCP engagement parameters for the VOR, LOC, and GS Navigation modes, and what will it provide?
Above 50 KIAS:
VOR and LOC modes provide roll commands for the desired course, and GS mode provides collective commands to follow the glide slope.
What does the DECL (ILS Deceleration) mode provide when activated?
Pitch command to slow the helicopter to 70 KIAS by 200’ AGL using the DECL mode (0.5 kts per second deceleration).