A-12/M-21 Cygnus V1.11 Fuel Gauge and CG Procedure Questions/Problems

[lmeirose]

Hello David and Glowingheat Aircraft Development Team,

Once again, thank you for a wonderful job on your SR-71, A-12, and B-58, and for your timely help with every technical question I have had in the past. Thank you!!

I have some additional questions regarding fuel and CG management in the A-12/M-21 Cygnus for FSX. I have read both the Glowingheat and original CIA flight manual (David - thank you for providing that, by the way! ) and understand 25% MAC is appropriate for takeoff, about 28% MAC is the limit for Mach 3.2 at altitude and approximately 19% MAC is the optimum CG for landing. My questions/issues are the following:

What is the accepted procedure for manual fuel tank sequence selection for the Cygnus during flight? In comparison, the Glowingheat SR-71, the manual suggests selecting the forward tank pair (tanks 2 and 3 on the gauge) first. Once the forward tank pair is empty, then the CG can be adjusted by alternating between the nose and tail balance tanks (tanks 1 and 6 on the gauge). Is this procedure also the same for the Cygnus? What sequence or procedure (MANUAL or AUTO) do you personally use (as the fuel gauge in V1.11 only allows for tanks to be selected individually and not in pairs)?

In the SR-71 manual, during descent/preparation for the landing, the "FWD" switch is used to transfer the remaining fuel from the aft tank pair (tanks 4 and 5) into the forward pair (tanks 2 and 3) to as close to the following configuration as possible:

CG: 20.6%
Nose tank: EMPTY
FWD fuselage tank pair: ~20%
AFT fuselage tank pair: EMPTY
Tail tank: ~20%

Excluding the CG reading, is this the optimum landing configuration for the Cygnus? How do you personally manage the fuel balance?

I have been having some problems with A-12/M-21 V1.11 fuel gauge:
When I manually attempt to transfer fuel from the aft tank pair (tanks 4 and 5) to the forward in preparation for landing, both aft tanks 4 and 5 drain, but only tank 2 of the forward pair fills up; tank 3 does not. As a result, I always have to manually dump the fuel from tank 5 to achieve the recommended 19% MAC before landing. Is this the correct approach? If not, Is there anything I can do on my end to fix the gauge?

I would greatly appreciate any suggestions and/or help you might have. If you need me to provide additional screenshots, please let me know.

Thanks very much for your time and help. I look forward to hearing from you.


Best,

-Leo

[DBushell]

Hi Leo,

The real life A-12 didn't have a CoG gauge to cross check against, but the tanks should drain in order giving reasonably correct CoG for all flight aspects. I may or may not have nailed this, I admit fuel tank sequencing is not my strong suit. Personally though, I take-off and fly without adjusting the fuel, until it comes time to land where I will dump to get down below 20% remaining, and I forward transfer the remainder. That way when it comes time to land the aircraft should be relatively balanced.

I'd need more time to investigate this one.

David.

[lmeirose]

Hi David,

Thanks very much for your response! No worries. Thank you for taking the time to investigate this. I was just curious as to the operations and if anything needs to be done for the fuel/CG gauge. If necessary, take all of the time you need. If nothing can be done, it’s absolutely fine. You and your team have done a fantastic job! As always, thanks again for all of your help!


Best,

-Leo