Powerplant Flashcards
What engines and how much thrust?
Honeywell TFE731-20
Each produces 3500lbs thrust static at SLP, and 3650lbs using APR
N1 Fan Gearbox output to input ratio
0.556
Fan spins at 0.556 of what the LP shaft spins at
Name the seven sections of the engine
Air Inlet Fan Compressor Combustor Turbine Exhaust Accessory
Describe N1
Fan speed or low pressure rotor rpm.
Consists of the Fan, 4 stage LP compressor and 3 stage LP turbine.
Describe N2
Turbine speed or HP rotating group/spool.
Consists of single stage HP compressor and HP turbine.
How is ITT measured?
By 10 thermocouples located in between the HP and LP turbines.
What is the engine bypass ratio?
3.1 to 1
How many fuel nozzles per engine?
12 duples fuel atomizers & 2 ignitor plugs.
What drives the Accessory Gearbox?
The HP centrifugal compressor drives the tower shaft, which drives the transfer gearbox, which drives the accessory gearbox.
What is driven by the Accessory Gearbox?
(rear)
Oil pump
Engine driven Fuel pump
FCU
(front) DC Starter/Gen AC Alternator Hyd pump Motive flow fuel pump
What percentage is IDLE
Flight idle is 65%N2 and increases w altitude.
Ground idle is 52%N2.
It will be commanded 20secs after touchdown unless higher thrust is set.
What does DEEC provide?
Thrust management Rating display/N1 Bug Overspeed protection Automatic start sequence Spool speed and temp limiting Surge-free accel and dece Engine synchronization APR
FCU flyweight governer overspeed protection
Operates the fuel metering valve to restrict fuel flow to prevent the engine from exceeding 105%N2
DEEC overspeed protection
Closes overspeed solenoid valve at 107%N1 or 109%N2.
Describe the flow of fuel from wing to engine.
From wing to 2 stage LP and HP engine driven FP.
LP centrifugal FP to heater/cooler and filter and back thru the HP gear fuel pump.
From pump to FCU
FCU to fuel flow sensor
Sensor to flow divider
Divider to manifolds and nozzles.
Target N1 Bug settings should be within…
1% between both engines
N1 Bug readouts
Ground/Flight w flaps or gear down: T/O power
Flight w gear/flaps up: detent power (APR,TO,MCT,MCR)
Below MCR the bug is removed.
N2 range
0-115%
> 100% display is amber(101.1% for APR)
> 102.5% display is red
Oil pressure range
65-80psig (white)
Oil temp range
30-127°C
What 3 scenarios does DEEC auto activate ignition?
- Normal engine start
- Uncommanded engine decel
(N1 is set and N2 not accelerating) - Excessive engine decel
(to prevent flameout; actual decel is greater than decel commanded thru thrust levers)
Describe DEEC normal ignition
- Thrust lever moved to IDLE
- START switch depressed
Ignition activated at 6.8%N2 and off at 45%N2
Describe the colors of IGN
- Green: both ignitors on
- White: one not firing
- Amber: both not firing
Describe the starting process
P. 7-26
Starter drives tower shaft which drives N2
DEEC commands ignition at 6.8%N2
Fuel introduced at positive N1 (~11-12%N2)
Ignition/Starter cutoff at 45%N2
DEEC brings generator online at 49.4%N2
(95% of ground idle/52%N2 is 49.4%)
Secondary signal for starter cutout at 50%N2
Parameters of starting an engine
ITT indication within 10secs of initiation
Oil pressure within 10secs of lightoff
START turns amber if energized above 51%N2
Both spools should increase smoothly and rapidly after lightoff
60secs from start to idle N1
Authority limits for SYNC
+/-5%N1 during midrange operation
0% at takeoff PLA
-2% to +5%N1 at flight idle
When must SYNC be off?
Takeoff, landing, and single engine operations
Sync will not function during APR
When will SYNC not be green?
Sync will be amber while the gear is not locked up. A chime will indicate an amber sync.
What is APR?
APR provides automatic increase in thrust on the operative engine in the event of a power loss on the other during takeoff and missed approach.
The DEEC senses a > or =15% mismatch in N2 in auto mode. It can also be activated manually.
APR provides an extra 150lbs of thrust by increasing ITT limits by 22°C to allow a 2% increase in N2.
How do you reset APR?
In auto, the APR ARM switch must be cycled off.
If accidentally activated on the ground by differential thrust, cycling the APR switch off and back to ARM with thrust N2 within 15% will reset the system.
Engine oil capacity
8.6 quarts per engine
Engine oil burn
1 quart per 25hrs
When should oil levels be checked?
Within 1 hour after shutdown
Oil pressure limits
50-100psi (up to 125psi for start)
Reversers should be stowed at
40kias
