Systems Flashcards
Engine
T700-GE-701D
1760 continuous SHP (0-739C)
1902 intermediate SHP (739-845C)
1994 max SHP
2000 contingency SHP
Engine will spool up to match the other, will not spool down if the other fails
Connected to the powertrain by the free wheeling unit, allows transmission to continue rotating in single engine operation or autorotation
DEC/EDEC- (enhanced) digital electronic control. Sits under the compressor and controls the electrical function of the engine and transmits operational info to the cockpit. EDEC DAS plug must be installed, otherwise the engines will operate with 701C limits.
DAS plug - discrete application allows the engines to operate at their 701D limits (TGT).
**LOCKOUT - locks out the DEC signal to the fuel controller, allows you to manually do so with the power/fuel controller for more power.
Hot start preventer (HSP) - is a function of the DEC and overspeed drain valve, automatically prevents hot start from occurring
**HMU - hydro mechanical unit controls the amount of fuel flowing into the combustion section (controlled b the engine handle and the collective (raising/lowering). Controls both airflow in and fuel mechanically, always putting in a little too much fuel where the DEC comes in and fine tunes the fuel flow. Based on the NP speed (DEC keeps the NP at 100%)
Overspeed drain valve - has a hot start circuit that can close a valve and stop all fuel from reaching the engine
PAS - power available spindle, opens slightly during IDLE position on the power handle so the HMU can control the fuel during start. DEC signal comes in when power handle moved to FLY
Load Demand Spindle - connected to collective, moves a valve to increase/decrease fuel for the load demand by the collective. If failure occurs, the valve sticks open and then the DEC takes over to fine tune it. Allows you to continue using the collective and have more power than needed, not less
Power Takeoff Dive Assembly - run off the compressor, turns all the accessory gearbox gears and components connected to it (fuel pump, oil pump, blower, liquid to liquid cooler, alternator, etc)
Inlet particle separator - swirl vanes throw particles like sand/dust to the outside and pulled up the scroll case to the blower and back out. Protects engine from dirty air, but not ice and not at slow speeds
Line Replaceable Units - LRU’s
6 stages of compressor - 5 axial and 1 centrifugal (7:1 axial compression, heats air to roughly 500*F), (18:1 centrifugal compression after centrifugal stage)
Inlet Guide Vane - IGV are in front of the compressor and between two other compressor portions (3 total) and are adjustable by the HMU; allows more or less air to flow into the engine.
Engine Inlet Temperature (T2**) - liquid chemical inside contracts or expands and moves a lever inside the HMU, which allows the HMU to know what temperature the outside air is. It will restrict flow with the variable guide vanes at lower temps due to more dense air to make sure the inlet air does not reach the speed of sound and cause compressor stall. This is called NG LIMITING
Power Control Levers (PCLs) - inside cockpit; idle, fly, and manual LOCKOUT for manual power control
- Compressor and GG rotor speed is called NG… 75% of power produced is used to drive the compressor
- Power turbine (consists of two power turbine rotors) speed is called NP; a one-way mechanical connection to the rotor system; 25% of combustion power drives the power turbine. WILL NEVER REDUCE THE ROTOR ON ITS OWN
- Engine Torque - Q; measured by the deflection/distance of the teeth of the power turbine shaft when torque applied - magnetic pickup senses it and is our measure of torque Q.
- Main Rotor Speed (NR) - 100% is 258rpm
4 sections (modules) - cold section module[swirl frame, front frame, main frame(oil tank), scroll case, compressor, diffusor], accessory section module, hot section module, power turbine section module
NG limiting by the T2 sensor telling the HMU how cold the inlet air is, and the the HMU moves the 3 Variable Guide Vanes to increase or decrease inlet flow (saves engine from compressor stall and allows engine to run as efficient as possible)
- Green cables carry signals to the cockpit
- Yellow are AC power on the engine (alternator, which also provides NG speed for the engine, and AC power to all essential engine electrical components (generator as a backup))
- Black cables are Ignition exciters (black heat wrap)
- Blue cables are overspeed and hot start prevention
- Red cables are Integrated vehicle health indicator system
- White cables are airframe electrical supply
NG and NP are the two operational sections of the engine
NG Limiting can be deadly, just because you think you have torque for a maneuver, if your NG is topping out, you can droop the rotor quickly
Fuel system components
Engine driven fuel pump Fuel pressure sensor Fuel filter HMU Liquid to liquid cooler Overspeed and Drive Valve (ODV) Main fuel manifold
- Engine driven fuel pumps operate on negative pressure and suck the fuel into the engine… safety feature incase a line breaks (output side is positive pressure)
- Fuel pressure sensor tells cockpit if fuel pressure is at or below 9 PSI… engine will not run much longer on this pressure (engine driven boost pump failure OR break in the line)
- HMU contains a high pressure pump that delivers fuel to the ODV
- Liquid to liquid cooler fuel and oil in separate lines, fuel cools the oil as it goes through
- Overspeed and Drive Valve with pressure, a valve opens and sends the fuel to the 12 injectors. On shutdown, the pressure pushed the leftover fuel back up and out of the helicopter (NP at 120%, overspeed valve shuts engine down… in lockout, i no longer have TGT limiting but I DO have overspeed protection)
- Main fuel manifold located on the diffuser case, supplies fuel to the 12 injectors evenly spaced around the ring combustor (spins the fuel for a better burn)
- NO TGT LIMITING DURING START, LOCKOUT, OR COMPRESSOR STALL.
LDS inside the HMU closes or opens a fuel valve as the collective is increased o decreased
Oil system
Oil tank Oil and scavenge pump Oil filter A(Engine bearings), B(GG rotors) and C(Power Turbine rotors)sumps Scroll vanes Scavenge screens Liquid to liquid cooler Engine chip detector Emergency oil system designed to give you 1 minute of oil to sump A and B (shut engines down!)
Engine control system
- DEC/EDECU
- Engine control quadrant (ENG POWER CONT levers)
- Load demand systems
- Speed control system
- Hydromechanical unit (HMU)
- Overspeed Drain Valve (ODV)
DEC/DECU receives inputs to control and monitor engine functions, reducing pilot workload; mounted below the compressor casting; powered by the alternator or the airframe power; cooled by airflow through the scroll case; provides NP1, NP2, Q, TGT and engine history counter. Provides a) load-sharing function, b) transient droop response, c) torque system stabilization (torque matching between engines), d) engine speed trim to meet speed reference. Pilot may override DEC with LOCKOUT and manually controlling power. Put back to IDLE, then FLY to put back into DEC control.
Overspeed protection shuts the fuel to the engine off and causes engine flameout at 120+/-1% NP1 or NP2. When NP1 or NP2 is reduced below the limit, fuel flow is returned to the engine and engine ignition comes on for re-light. This cycle will continue until the condition is removed.
If starting by battery power, no TGT protection provided.
HMU has another valve that if the NG goes to 110%, will shut off fuel (will only happen if the T2 sensor/system malfunctions)
One tape and one ball - 10 minute TGT limit
One tape and two balls - 2.5 minute TGT limit
Engine Control Quadrant has
- two PCL’s with
- starter button on each PCL
- PCL can be pulled down to abort start
- each PCL has 4 positions (Off, idle, fly, lockout)
- PCL must be pulled down to move out of the IDLE or FLY detents
- two engine fuel system selector levers (OFF, DIR, XFD)
- two engine emergency off (ENG EMER OFF) T-Handles; pulling aft shuts off fuel system and arms fire extinguisher system
**In engine LOCKOUT, NG and Max Fuel Flow limits still work (functions of the HMU which are mechanical)
Engine start compressor
Start components
- pneumatic motor
- start control valve
- pneumatic ducting
- controls
- external start pneumatic port
Pneumatic driven air turbine starter motor can receive air from 3 sources
- APU
- external air source
- engine cross bleed
Starter can turn the accessory gearbox and NG until speed increases past starter speed (starter can drive engine, engine cannot drive starter through a one-way clutch)
Ignition system
1 engine can start off the battery, #2 engine may be started by Aircraft AC power
Ignition key
Dual ignition exciter
Leads and plugs
Power is applied to the ignition system until the ENGINE IGNITION keylock is moved to the off position, or the starter drops out
- ABORT START*
- criteria
1) No TGT increase within 45 seconds
2) No P (engine oil pressure) within 45 seconds
3) No NP1 or NP2 within 45 seconds (if rotor brake is off)
4) ENG STARTER ON caution disappears before reaching 52% NG
5) TGT reaches 851*C before idle is attained (above 63% NG)
Manually disengage the starter by pulling straight down on the PCL
Engine Anti-Ice
Performed by two systems, and engine inlet anti-icing and an engine anti-ice system, which prevents ice build-up from restricting the air supply to the compressor section. Both of these systems are activated by the ENG ANTI-IC NO.1 and NO.2 switches.
Engine inlet anti-ice
a) available at 4C and below
b) may or may not be available at 4-13C
c) not available above 13C
d) engine inlet advisory lights
1) ENGINE ANTI-ICE ON indicates engine inlet anti-ice/start bleed valve is open
2) ENGINE ANTI-ICE indicates engine inlet anti-icing air temp is >93*C
e) to fly into trace or light icing conditions, must have [engine anti-ice], [engine inlet anti-ice modulating valve insulated], [ambient air sensing tube]
f) engine air inlets are anti-iced by stage 5 bleed-air from the engines supplied by the opening of the AISBV
Other than bleed air, ENGINE OIL THROUGH THE SCROLL VANES provides a passive anti-ice function
Engine inlet anti-ice automagically turns on at <4C, and may or may not turn on between 4-13C.
With engine anti-ice on, engine can lose up to 20% of it’s power capability
Exhaust
Upturned exhaust reduces IR missile lock capability
