601D Engine Flashcards
DEC/EDECU functions
IN FLT HOTT
Isochronos NP governing.
NP Reference (96-100)
Fault indications (Q indicator and FMS DEC status page)
Load sharing/torque match - increase Q of low side to match Np no more than 3% above reference
Transient droop comp - compensates, uses collective position indicator
History counter - sends signals to history counter
Hot start preventer - tells ODV to shut off @ 900 degrees Ng<60 Np<50
DEC/EDECU maintains constant power turbine speed of
100% (NG)
What does TGT limiting limit at
879 +/- 9 - 10 min limit
903 +/- 10 - 2.5 min limit
Load sharing keeps both engines matched within
5% torque
Overspeed protection kicks at
120% +/- 1% Np
Torque matching
-Increases power on lower Q engine to keep Qs approximatly equal
-System will not allow high engine to reduce power to match
-If engine fails highside, good engine should only attempt to increase Q until NP is 3% above reference
When does TGT limiting not work
Engine start, compressor stall, lockout
Define LOCKOUT
Manual control of engine RPM while bypassing DEC/EDECU TGT limiting
How can you override Hot start prevention for an engine start?
By holding either ENG OVSP TEST A or B buttons with the engine being started during the start sequence
Is overspeed protection disabled in lockout
No
Parameters to bypass 10 minute TGT limit
to go beyond 879 degrees;
DEC - One engine below 50% Q
EDECU -
- Np drops below 96
-Greater than 3% difference between Np and Np reference
-Greater than 5% per second drop to, or below Np reference
What can be seen in AC with both a DEC and an EDECU
Torque splits in a “contingency situation”
Can you push from idle to fly with rotor brake engaged?
No. There is a rotor brake interlock tab that should prevent this
How does the load demand system work
DEC and HMU respond to collective signals
Load sharing keeps engines within
5% torque
What mechanically links the NG and the accessory gear box?
The power take off assembly
What is T2
Inlet air temperature
-used by the HMU to compensate for air temp changes
-Used in NG limiting
How is TGT measured?
7 probes on the thermocouple assembly
Probes measure between NG and NP
(silver pipes wrapped on aft end of engine)
What are the 4 main modules of the engine
Hot
Cold
Power turbine
Accessory
Describe the engine compressor
A 6 stage air pump that continuously pressurizes the combustion chamber, provides bleed air
5 stage axial, 1 stage centrifugal
Describe the order of guide veins and compressor stages in order of flow
Air is drawn in through the variable stage 1&2 veins, through 5 axial fixed compressor stators, then through the centrifugal stage
What changes the angle of variable stage veins
HMU via a crankshaft assembly
When will engine anti-ice activate, even though the switch is off?
88 to 92% NG
When can inlet anti ice not be provided?
Torque settings below 10% Q
Which of our chip detectors have fuzz burn?
Transmission. Engine chip detectors do not (smaller wire)
What are DCUs?
Data concentrator units
-Takes engine, powertrain inputs, and caution/advisory inputs, sends to MFDs
-EICAS compares outputs to generate miscompares
What can happen with a DCU fail?
EICAS loses all its shit and goes full reversionary
CHIP IBIT FAIL caution may appear
What part of the fire detection system is not tested with positions 1 or 2?
The photo cells
(It does check all detectors POS 1 and deck mounted only in POS 2. Lets find the difference between photo cells and detectors)
Failure to see inlet anti ice appear at 4C and below. Can you still fly?
Do not fly in known icing conditions.
Oil impending bypass button. Below what temperature should it not pop at all?
Below 38C. Thermal lockout is supposed to keep the button from popping. We should verify if we see a bypass during a cold runup that button has not popped postflight.
During engine start, when do engine ignitor exciters fire sparks? Why does it matter?
Until starter dropout
OR
Until ignition key is turned to OFF position.
(Ignitors will not fire if starter is motored with key off)
-Shows why we dont turn key on after engaging starter (hot start)
-Shows why we should turn the key off if starter hangs and doesnt want to disengage with PCL pull down
When using an air source other than APU to start an engine, what should you expect?
Expect a hung starter, especially If NG is near low end for cross bleed start (Near 90% NG) or if PSIG for pneumatic start is near low end (40 PSIG)
Near minimum required pressure will be enough to start the engine, but not enough to drive the starter fast enough itself to trigger the starter speed switch, which disengaged the starter.
What is the DECs TGT offset (bias)
Is the bias always present?
-112 degrees
When the DEC is not being powered (AC?) am unbiased TGT indication is displayed.
If you are going to motor an engine without starting it, what should you do?
Make certain the engine ignition key is OFF
(Think engine flush)
To prevent hot start, never turn on key after starter is engaged.
Where does lockout begin? (need to answer still, ask MTP)
Is it a microswitch just past fly?
Half way?
Or do you have to contact the lockout stop?
Which is the only non self sealing fuel line?
The APU fuel line
How do you use/interpret the Fuel indicating system test button?
(Fuel IND TEST on upper console)
When pressed, the system sends a false empty signal to each tank. Each tank SHOULD read as empty when using the test button
If either tank doesnt read empty when pressing the button, there is a problem.
