EPU running even when switched off prior emergency?
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I tried looking in the manual, couldn’t find the answer. If it is there, please tell me in what section and I’ll buy you a beer for your trouble.
Situation: set up a flight with 1000lbs of fuel. Commit to runway. Set EPU switch to OFF. Take off in full AB. Watch engine flame out. EPU light ON and AIR+HYDRAZINE ON. Is it normal the EPU can fire even when the switch is in the OFF position? -
Logic would say no.
Darwin would say that if the pilot was stupid enough to put it to OFF rather than NORM, he deserved the immediate ejection -
@Red:
Logic would say no.
Darwin would say that if the pilot was stupid enough to put it to OFF rather than NORM, he deserved the immediate ejectionIndeed
I was just running some tests to see what sharedmem flags of power (battery, emergency bus, essential etc) are flagged during flameout and then when EPU fires. And I couldn’t get the jet to drop down to emergency only. Then I looked down and saw the EPU was running even when I deliberately set it OFF before taking off.
So is there a bug in the EPU logic then in BMS? Or am I missing something else? -
Indeed
I was just running some tests to see what sharedmem flags of power (battery, emergency bus, essential etc) are flagged during flameout and then when EPU fires. And I couldn’t get the jet to drop down to emergency only. Then I looked down and saw the EPU was running even when I deliberately set it OFF before taking off.
So is there a bug in the EPU logic then in BMS? Or am I missing something else?IIRC, EPU is armed during the EPU check (by switching it OFF then NORM) … from this point, EPU will run automatically even is in OFF position.
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IIRC, EPU is armed during the EPU check (by switching it OFF then NORM) … from this point, EPU will run automatically even is in OFF position.
Aha, that could indeed be.
Now I’ve tried again and started from a cold jet. Setting EPU off before starting up and then taking off and burn till flame out will indeed not have EPU kicking in when it’s in OFF position. -
A real -1 sheds more light on it
OFF
- Prevents or terminates EPU operation on the ground (WOW).
- Does not prevent or terminate EPU operationin flight for main and standby generator failures if switch was cycled or placed to NORM at anytime since takeoff (since WOW).
- Prevents EPU operation in flight if switch has remained in the OFF position since takeoff (since WOW).
- Terminates EPU operation in flight except during main and standby generator failures.
The last point is indeed what happened in my first attempt in the air. Even when setting off it wouldn’t terminate once it got started.
However, points 2 & 3 say “since takeoff/WOW”. So even when I chose to commit directly to runway, and I have switched it off before taking off, it shouldn’t have fired, no? -
Now I’ve tried again and started from a cold jet.
Normal, you didn’t armed it by re-going to norm position.
If you do not start in Ramp (Taxi/Takeoff init) code assume that “you” have made the EPU test already and hence the EPU is armed.
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Normal, you didn’t armed it by re-going to norm position.
If you do not start in Ramp (Taxi/Takeoff init) code assume that “you” have made the EPU test already and hence the EPU is armed.
True, I understand.
But judging from the -1 explanation on the switch, it shouldn’t matter if I, or AI, have cycled it as long as I had WOW. -
Since WOW
doesn’t it mean:
since the airplane landed and has weight on wheels?Cause it was said as the other way around.
sent from my Xperia Z3 compact via TapaTalk
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Based on the third item for that list it would more be weight off wheels?
In my test starting from ramp it has been in off from setting it so when still cold until airborne and flame out, so shouldnt be fired