A109 automatic engine shutdown ?
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A109 automatic engine shutdown ?
Hi
am I understand it right ? the ECU will automatically shutdown engines when TRQ is above 110% ? the other helicopters have similiar/same ?
Regards
am I understand it right ? the ECU will automatically shutdown engines when TRQ is above 110% ? the other helicopters have similiar/same ?
Regards
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so theoretically when you do negative G and simultaneously reduce collective you may have turbine overspeed and that may cause eng. shutdown .
I also heard that during descent is better to avoid TRQ less than 7% that's because FADEC may switch the eng off - I'm not sure this is only when GOV in MAN mode or during normal operations as well
I also heard that during descent is better to avoid TRQ less than 7% that's because FADEC may switch the eng off - I'm not sure this is only when GOV in MAN mode or during normal operations as well
CHR,
At the 110% ME Tq limit the fuel flow will be "restricted" not cut off, it basically causes the TQ to sit at 110% on the affected engines, and prevents any further TQ being delivered, with a resulting RPM Droop.
The Overspeed "Cutoff" is a bit of a blunt instrument, it doesn't stop the engines, it cuts the fuel using a solenoid in the FMM (from memory), that causes the N2 to fall, once it falls below a threshold value it is free to try and Overspeed again, if the load on the engine has not changed.
Never heard of an issue with 7% Tq being mentioned, I can only assume that is someone's rule of thumb to prevent NR overspeed due to keeping N2 and NR "matched" by always having some Torque applied.
It's fairly easy to overspeed (within transient limits) NR on the S and SP, with brusque manoeuvring when you first start to fly them, the Rotor head is more aerodynamic than the E model and it can come as a bit of a surprise, NR goes up quick, but it also comes down fairly quickly, even with my meagre skills.
At the 110% ME Tq limit the fuel flow will be "restricted" not cut off, it basically causes the TQ to sit at 110% on the affected engines, and prevents any further TQ being delivered, with a resulting RPM Droop.
The Overspeed "Cutoff" is a bit of a blunt instrument, it doesn't stop the engines, it cuts the fuel using a solenoid in the FMM (from memory), that causes the N2 to fall, once it falls below a threshold value it is free to try and Overspeed again, if the load on the engine has not changed.
Never heard of an issue with 7% Tq being mentioned, I can only assume that is someone's rule of thumb to prevent NR overspeed due to keeping N2 and NR "matched" by always having some Torque applied.
It's fairly easy to overspeed (within transient limits) NR on the S and SP, with brusque manoeuvring when you first start to fly them, the Rotor head is more aerodynamic than the E model and it can come as a bit of a surprise, NR goes up quick, but it also comes down fairly quickly, even with my meagre skills.
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In certain EECU failure conditions on the AW169 it will automatically bring the engine back to IDLE where it can remain online as a generator, provided the EECU can still control the stepper motor. There is no manual throttle. The only automatically commanded ‘shutdown’ is the hot start protection.
Much prefer the single-channel DECU with a manual reversion to a full FADEC.
On the S92 a FADEC dual channel failure results in the engine shutting down, with no manual reversion/control. (Well, it did unless recent updates have changed that). I was never clear why that decision could not be left to the pilot, because a frozen engine will/should not cause serious problems unless you make a significant change to the 'power demanded/required' vs the 'power available' (or, 'power being provided')
Oh, that comes as a surprise, dual channel failure logic to shut down the engine. In the S76C++ dual channel DECU failure reverts to manual control. Or you can revert to manual control any time you want by flicking a switch. We could even do both engines in manual control in the simulator which was a little bit silly as that was so unlikely to ever happen. But it was a good airmanship exercise for those who could do all the other stuff.
Oh, that comes as a surprise, dual channel failure logic to shut down the engine. In the S76C++ dual channel DECU failure reverts to manual control. Or you can revert to manual control any time you want by flicking a switch. We could even do both engines in manual control in the simulator which was a little bit silly as that was so unlikely to ever happen. But it was a good airmanship exercise for those who could do all the other stuff.
The clue is in the title - FADEC is Full Authority and implies no manual control. A dual channel DECU would be a different beast and could include a manual reversion.
Anyone know of an aircraft with dual channel and manual reversion?
The Wessex fuel computer could freeze leaving you with fixed power whereas the Sea King (same engine and computer) also allowed manual control.
139 has manual reversion as does the AS 365 N3
Anyone know of an aircraft with dual channel and manual reversion?
The Wessex fuel computer could freeze leaving you with fixed power whereas the Sea King (same engine and computer) also allowed manual control.
139 has manual reversion as does the AS 365 N3
