Engine RPM issues

[NikolaiVChr]

N2 ignition point should be 20%

https://github.com/JSBSim-Team/jsbsim/issues/233

prevents this from being fixed until next FG release.

[NikolaiVChr]

Changing this issue, to be about RPMs in general

[NikolaiVChr]

From mark on f-16.net on max N2: F-110-GE100 Max RPM 106% F-100-PW220 Max RPM 96 % F-100-PW200 Max RPM 96% F-110-GE129 Max RPM 108% F-100-PW229 Max RPM 97%

and on rpms:

F-110-GE100 100% on the gauge is equiv to 14,460 RPM F-100-PW220 100% on the gauge is equiv to 14,000 RPM

[NikolaiVChr]

for F100-PW-229:

100% N1 is 10,000 and 100% N2 = 14,000 MAXIMUM is 11,000 for N1 and 13,800 for N2.

[NikolaiVChr]

Timi found this doc: https://www.nasa.gov/centers/dryden/pdf/88434main_H-2122.pdf

The paper test the F110-GE-129:

Idle power is at 20° power lever angle (PLA) setting, and intermediate (maximum nonafterburning) power is at 85° PLA. [What is max PLA????]

In that paper the rpm reached: N1 8520 N2 15094 (probably 108% N2)

[NikolaiVChr]

Furthermore the Tachometer is different on GE engines. GE goes to 110%

[NikolaiVChr]

PLA for F100: 0 degrees - cutoff 16 degrees - Idle 86 degrees - Intermediate or Military 91 degrees - Min AB 130 degrees - Max AB

[NikolaiVChr]

the engine schedule is intended for a relatively linear relationship between PLA and thrust at any particular flight condition

Interesting, will have to make that..

[NikolaiVChr]

06760e2d526330d0f2f85b971c8514a3285ec247 fixes linear relationship and indent position for F100 throttle.

[NikolaiVChr]

Timi: According to this article the later blocks can go from idle to afterburner in two seconds: https://www.codeonemagazine.com/article.html?item_id=23

[JMaverick16]

BTW I still think our spooling time from 0 to 25% is slower compared to videos of it. Thoughts?

[NikolaiVChr]

Time to consider fixing this? Users of older FG, will have to use older versions of F-16.

[JMaverick16]

Older FG as in < 2020.2?

[NikolaiVChr]

No, as in less than 2020.1

[JMaverick16]

J Mav approves

[ph-jake]

BTW I still think our spooling time from 0 to 25% is slower compared to videos of it. Thoughts?

Looking at the "F-16 Engine run, Iraq" video, time from Start 2 to JFS Run light is about 8 seconds, then another 20 seconds for the RPMs to rise to 20%. Our simulation takes 30 seconds to JFS run light, and about 10 seconds for RPMs to 20%.

[NikolaiVChr]

Yes, they probably improved the JFS since the one I modeled, I think that was a rather old model. Also I do believe it spools up faster when doing START 2 than START 1, but I seem to remember I could not find info how how much faster.

As for getting to 20% that might vary alot on the engine installed. But we can change that rate, but wont be supported for 2018.3, so I think this should wait till 2020.3 which should be in a couple of days.

[NikolaiVChr]

N1/N2 ignition is now 5.21%/20.0% for 2020.3 Which means ignition is now wrongly 20%/25% for 2019.1

[NikolaiVChr]

In the same video from Iraq (block 30), I measured this: <n2startrate> 1.6 </n2startrate> Thats the spooling speed from 20 to idle. I haven't put in that number though, as it should match JFS and 0 to 20 also. Maybe we should have a JFS spool time for each block.

[JMaverick16]

Wouldn't be a bad idea. I support it

[ph-jake]

In the same video from Iraq (block 30), I measured this: <n2startrate> 1.6 </n2startrate> Thats the spooling speed from 20 to idle. I haven't put in that number though, as it should match JFS and 0 to 20 also.

I don't get it. When the JFS is switched on (START 2 or START 1) the bottle(s) blow and get the JFS up to run speed ASAP. Timing the video shows from switch on to run light < 10 seconds, using START 2 (both bottles). Only then the engine starter is engaged, using the JFS energy to spin the core up to 20% for ignition. What does the n2startrate have to do with the the time the JFS spools up?

[NikolaiVChr]

Nobody said they are related. But this issue is about RPM in general, both JFS and engine. Please reread my post, I make no claim to talk about JFS in regards to that value.

[NikolaiVChr]

..and when I say 'match' I mean not they should be same.

[NikolaiVChr]

Let me detail what I meant by 'match':

If we just fix engine spool-up from 0 to 20 and from 20 to idle, without changing JSF also, starting total is going to take alot longer than now and that it does in real life.

So need more info on different JFS spoolup times than just 8s with START 2 from block 30. ..or we need to guesstimate.

All we know now is one JFS (which blocks?) takes 30s and a block 30 (MLU?) takes 8s.

[NikolaiVChr]

Alright, I changed the JFS, it can now be configured per block.

I put in these numbers:

Total START 2 startup times:  (JFS + to 20 + to idle)
block YF/10/20   : 20+20+25 = 65s
block 30/40/50/60:  8+20+25 = 53s

Total START 1 startup times:
block YF/10/20   : 30+20+25 = 75s
block 30/40/50/60: 12+20+25 = 57s

I had to increase autostart watchdog timers to be sure it could handle block 10 (START 1)

[NikolaiVChr]

Some engines seems to have 65% idle. I am guessing its the GE engines.