JFS - START 1 & START 2 not correct

[Dača]

Hello, dear ED team.

I wanted to point out small but annoying irregularity considering JFS startup. In real life, JFS starter turbine is cranking using 2 compressed gas reservoirs. As you know, start 1 for one "bottle" and start 2 for both at the same time. Problem is that in real life JFS reservoirs are exhausted a bit less than 2 minutes (can't remember where I've seen this info on their duration) after START switch is set to 2 (or 1), while in DCS they are infinite and will never exhaust.

With this, timing is crucial when bringing engine to life. Right after SEC light dissapears and RPM hits ~20%, handle is immediately placed to idle position in order to finish engine start up before reservoirs (or one reservoir) are depleted. Refilling those reservoirs is not an easy task !

Right now we don't have to pay attention to this and can idle engine whenever we like, which is wrong.

Can this be simulated in the future ? Where:

1.) JFS is actually timed about 2 minutes and if throttle is not placed in idle position in this time frame (too late), JFS stops, JFS indication light goes out, engine cannot be started and we need to request ground crew option to repair aircraft or add additional Ground crew menu option for "JFS reservoirs refill".

2.) If we attempt to set throttle to idle too early, before SEC light is off and RPM is less then ~20%, it should be simulated as hot start - there’s not enough airflow to keep the engine cool. FTIT should indicate hot start where engine start up should be aborted to prevent possible damage (maybe this is already simulated, I forgot to test it).

https://theaviationgeekclub.com/starting-the-engine-on-an-f-16-viper-is-different-from-most-other-jet-aircraft-heres-why/amp/

 

Thank you for your time.

 

 

Best regards.

 

Edited 13 hours ago by Dača

[NineLine]

Thanks for the report, this is the response from the team I received.

The hydraulic/brake accumulators are indeed used to start the Jet Fuel Starter, but once the JFS is operational and it spools the engine past 12% RPM, the accumulators begin to recharge, even if the engine throttle itself is never moved to idle. If the user starts the JFS but manually shuts it down before the engine spools past 12%, it is possible to deplete the accumulators, although I am not sure why one would want to.

If you feel this is still wrong, I would be happy to take a look at any references you might have on this.

Thanks!

[Dača]

9 hours ago, NineLine said:

Thanks for the report, this is the response from the team I received.

The hydraulic/brake accumulators are indeed used to start the Jet Fuel Starter, but once the JFS is operational and it spools the engine past 12% RPM, the accumulators begin to recharge, even if the engine throttle itself is never moved to idle. If the user starts the JFS but manually shuts it down before the engine spools past 12%, it is possible to deplete the accumulators, although I am not sure why one would want to.

If you feel this is still wrong, I would be happy to take a look at any references you might have on this.

Thanks!

Nope, I was wrong to trust sites over manuals. Sorry.

It is how you said. Only thing not mentioned is not just pilot manually returnig jfs start switch to off will stop jfs and deplete reservoirs. Misfire probability is still a thing which ground crew needs to be prepared for.

Now only things that remains not simulated fully is START 1.

START 1 could be simulated in a way to have probability to "misfire" which also results in one depleted bottle. Second start 1 attempt with last remaining bottle and if fails again, you're done. Ground crew JFS refill is needed then. Misfire usually has higher probability in hot temperature, higher MSL altitudes, JFS bottles condition (pressure).

START 2 already has high start probability in RL and should remain as is.

 

Thank you.

 

 

Best regards.

Edited 2 hours ago by Dača