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PTU logic doesn't work and cross-bleed start impossible.


Skysurfer

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So basically the PTU (bi-di pump) does not work like it should and isn't really bi-directional. It works as intended when yo start/spool the #1 engine first but when you start the #2 engine the opposite side system (COMB HYD) does not pressurize. Same goes for a cross-bleed start, if you spool up the right hand #2 engine, disconnect ground air supply and select the right engine bleed the #1 engine will not spool no matter the RPM you spool the #2 engine up to. As far as I am concerned a cross-bleed engine start is pretty common for F14's especially on the boat.

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Just a question. Are you sure you disconnected external power after starting R engine?

Because that pump is not operating with connected external power.

Might be the issue.

 

Actually, not the electrical external power, just the ground air supply. Why would it affect the bleeds though? I will try once more though with no ext. AC power.

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I just tried this. As with OP, x bleed start of L eng was not possible. Using 80%N2 on R and selecting "Airstart-ON" did allow me to motor L eng. I was not able to disconnect Ground Air supply - as there was no response to my request. (Chief couldn't hear me?)

 

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I was not able to disconnect Ground Air supply - as there was no response to my request. (Chief couldn't hear me?)

After closing canopy, turn ICS to Hot Mic and use ICS PTT button.

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🖥️ Win10 i7-10700KF 32GB RTX3060   🥽 Rift S   🕹️ T16000M HOTAS   ✈️ FC3, F-14A/B, F-15E   ⚙️ CA   🚢 SC   🌐 NTTR, PG, Syria

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Ok I just did some tests and manual-digging regarding my previous issues and it looks like our A/B Tomcat does not include the AFC744 change and is modelled prior to BuNo 158612. In this case the operating engine needs to be spooled up to 87% RPM to achieve the desired bleed system pressure. This is mostly modelled in our DCS Tomcat, by spooling up the oposite engine to about 90% I was able to roughly achieve 10% starting RPM on the #1 engine and successfully start it. However, the required minimum RPM for a start is stated as 18% in the manual, and this can currently not be achieved in our Tomcat. So there is this descrepancy in starting RPM's and bleed supply.

 

Regarding the PTU logic - even with ground power disconnected and the aircraft being self-sustained the right hand engine with its respective FLT HYD system does not power the PTU pump to pressurize the opposite side system. Only once you crank the #1 engine does the system pressurize. Having the proper PTU logic is obviously "nice to have" for immersion but I'd see it as less critical when compared to the cross-bleed stuff. On another note, it would be highly appreciated if the AUX and ACCU Hydraulic system was modelled and the gauge behind the stick went into the green area - even be it via a simple script so it's not stuck in the red zone all the time (see attached image).

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I just tested in the B. Right engine started first, disconnected external el. power and air, the pump successfully powered both hydraulic systems. Also did cross-bleed start for the left engine with quite a bit of throttle. Turned off right engine and turned off transfer pump. Then pump on again after a while and tested hydraulics - both sides fine.

 

btw: what ACCU? There are PARK and AUX gauges.

🖥️ Win10 i7-10700KF 32GB RTX3060   🥽 Rift S   🕹️ T16000M HOTAS   ✈️ FC3, F-14A/B, F-15E   ⚙️ CA   🚢 SC   🌐 NTTR, PG, Syria

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I just tested in the B. Right engine started first, disconnected external el. power and air, the pump successfully powered both hydraulic systems. Also did cross-bleed start for the left engine with quite a bit of throttle. Turned off right engine and turned off transfer pump. Then pump on again after a while and tested hydraulics - both sides fine.

 

btw: what ACCU? There are PARK and AUX gauges.

 

Yeah sorry, PARK and AUX - got ACCU in my head from other planes. I'll go test it in the B I guess.

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