Why Stop Conformal Tank Transfer

[Avio]

During engines startup, why the need to first switch to stop conformal tank from transferring?  Something to do with CG balancing, but why? And it is only for that brief moment only right? Does that make much difference?

 

[Rudel_chw]

Yes, its to prevent CG changes before the take-off. In flight, all external tanks are pressurized and can transfer fuel. On the ground, since external wing and centerline tanks are depressurized, no fuel will transfer from those tanks. However, the CFTs can transfer fuel on the ground since the CFT electric transfer pumps operate continuously. 
 

Fuel transfer sequence within the CFT is designed so the CG moves forward as the CFT transfers fuel, so it is best to prevent fuel transfer from the CFT until you are ready for take-off.

[Rainmaker]

Okay, so the clear stiff up as its already going in the weeds unnecessarily. The stop trans is to check internal feeding to make sure the feeds and both wings xfer properly. Also, wear and tear on the CFT xfer pumps.  That’s it in a nutshell. In the DCS world, all of that will always work and nothing goes bad. Choose to do it or not based on your needs to imitate real life. 

[Avio]

Thanks a lot, folks. Very illuminating, love learning from this forum, priceless !

 

[draconus]

5 hours ago, Avio said:

Very illuminating, love learning from this forum, priceless !

Yeah, just wait till you're asked "How do you know all this?!"

[Nealius]

Is this CG change modeled in the sim? I admit I didn't know this was even part of the startup procedure but haven't seen any ill effects from skipping it. But I also don't spend more than 10~15 minutes on the ground with the engines running, so perhaps I'm just not burning enough gas for it to matter.

[Rudel_chw]

2 hours ago, Nealius said:

Is this CG change modeled in the sim?

I really don’t know, just like to follow the real procedures as much as possible  … I even edited my own cold start mission, as the built-in one didn’t include all details:

 

 

Edited September 7, 2023 by Rudel_chw

[Ala12Rv-Tundra]

39 minutes ago, Rudel_chw said:

I really don’t know, just like to follow the real procedures as much as possible  … I even edited my own cold start mission, as the built-in one didn’t include all details:

 

 

 

what checklist do you follow?

[Rudel_chw]

5 minutes ago, Ala12Rv-Tundra said:

what checklist do you follow?

the one described on page 2-7 of the TO 1F-15E-1CL-1  manual, I summarized it like this, as some items cant be done on dcs

https://1drv.ms/b/s!Ai6cuX3YQI26iopz6QRNMFpHZ4vS5w

 

Edited September 7, 2023 by Rudel_chw

[Ala12Rv-Tundra]

6 hours ago, Rudel_chw said:

the one described on page 2-7 of the TO 1F-15E-1CL-1  manual, I summarized it like this, as some items cant be done on dcs

https://1drv.ms/b/s!Ai6cuX3YQI26iopz6QRNMFpHZ4vS5w

 

 

Thanks, last Saturday we took a lesson on F-15E startup and patterns, and there was no quorum regarding what checklist to follow. We ended up following the official Manual.