Qns for Parameter for B744

[raymtoh]

Hi all,



I would like to ask if anyone of u all know wat are the things/criteria that can control the APU n1 of B744? Pls help mi out. Thank


regards,
raymtoh

[Michael Carter]

Why would you need to adjust N1 of the APU?

APU's are designed to run at a constant speed so the generator will supply the correct frequency and voltage to the aircraft busses.

Unlike engine driven generators that require a constant speed drive unit.

Maybe I am not fully understanding your question.

[michelmvd]

As far I know the APU has a constant speed, so also a constant N1
It is controlled by its own logics.
B. RGds
Michel

[raymtoh]

hi ,
Coz i require that APUN1 should be 95 then the APU AVAIL light will be on but right now my condition is when APUN1 is 87 it will be on. Thank for ur reply

[michelmvd]

Sorry I misunderstood your question I think.

Will I know in the original file the B744 APU values are far to low - also for spool up or downtime.

I changed the entry at which N1 the APU comes available :
"if apun > 87
apustartavail = 1"

but I think 87 was the highest I could have. In fact it should go to 100%. The spool up time was changed to 40 and down to 50.

But how you can change the N1 it self in PMsys , I don't have an idea .
Maybe Thomas can help here ?

B. Rgds
Michel

[Trevor Hale]

Well you could in your logic file set

XXXAPUN1VARIABLEXXX=95

The same as you can set your bleed Air pressure in the logics. However this would change from the value you set if you stopped the APU or started it again.

Trev

[michelmvd]

Aha thanks a lot Trevor Will test that
Maybe you can help me with the following also.

The PSI factor for the bleedair for a B744 is far to low in the present file (20/23)

-With APU on - both bleedair Valves open + 3 packs = value should be 28
-During engines start - or 1 engine running = 22
-All 4 engines running + APU still on = 39
-All 4 engines running - no APU = 34 which remains during flight.

Thanks for suggestions

B. rgds
Michel

[raymtoh]

hi Trevor,

For this XXXAPUN1VARIABLEXXX=95 , What is the offset for this? Wat is the XXX? I cant find this variable in the sysvars.Thank

[raymtoh]

Hi all,



I manage to ctrl APU n1 but the value is wrong. It is using the APUN offset. but for the APUN it is use for APU n2 also. when i put APUN =95 only the APUN2 will rise to 95. then when i put APUN=250 the APUn1 will rise to 250(as shown in the pic given). Did anyone know about this problem and how to solve it? thank

[raymtoh]

Aha thanks a lot Trevor Will test that
Maybe you can help me with the following also.

The PSI factor for the bleedair for a B744 is far to low in the present file (20/23)

-With APU on - both bleedair Valves open + 3 packs = value should be 28
-During engines start - or 1 engine running = 22
-All 4 engines running + APU still on = 39
-All 4 engines running - no APU = 34 which remains during flight.

Thanks for suggestions

B. rgds
Michel

Hi Michel,
I think u can set it through Pmsystem logic.I think the offset Bleedpsi1 or bleed1psi...