fixed Consistently wrong engine behavior depending on previous throttle position

[Machalot]

2 hours ago, Maxthrust said:

 

Nozzle operation is quite complex:

 

VARIABLE EXHAUST

1

NOZZLE OPERATION

Variable exhaust nozzle operation is controlled by throttle position and EGT. When the throttle is advanced slowly to MIL, nozzle opening decreases toward 0% until approximately 85% rpm. At this pofnt, the nozzle remains constant at a fixed cruise flat position ( 16% to 22%) until the throttle is advanced to where the nozzle starts to 

close toward 0%. The engine delivers best cruise power performance with minimum fuel consumption when on the cruise flat. When the throttle is advanced beyond the cruise flat toward MIL rpm, the nozzle continues to close until an EGT above 670° ± 5° is momentarily reached. The nozzle then opens via the T5 amplifier control to maintain EGT within limits. This is called Ts modulation. Just prior to T5 modulation, the nozzle is still mechanically controlled by the throttle. A throttle setting just prior to Ts modulation improves fuel consumption rates. When Ts modulation occurs, the nozzle opens slightly. During a rapid throttle burst from IDLE to MIL or MAX, the nozle closes to 43% to 53%, and stays at that opening momentarily. Nozzle hesitation at this point during acceleration minimizes exhaust back pressure to provide rapid acceleration and to preclude compressor stall. The nozzle then closes to 0% to 3% until T5 modulation occurs. At high altitude, low airspeed, when a throttle burst from IDLE or cruise to MIL or MAX is made, the nozzle opens toward the 43% to 53% area, then closes to approximately 7% to 12% to minimize rpm rollback and compressor stall prior to Ts modulation. During a throttle burst to AB range at low altitude, the main afterburner fuel flow is delayed by a sequence valve, momentarily causing the nozzle to pause (approximately 6% to 14% above MIL steady-state nozzle position) to allow afterburner pilot fuel to light off first; permitting a softer afterburner lightoff, 

28% to 38% to maintain safe EGT operation. 

This nozzle position is known as the T5 lockout area. At high altitudes and low airspeeds, MIL nozzle opening may be larger and EGT lower than observed at low altitudes

and high airspeeds. During ground operation at MIL power, nozzle opening should be approximately 0%. As the throttle advances into the AB range, openin~ should approximate 25% to 50% in mmimum afterburner, increasing to approximately 80% at maximum afterburner. Nozzle indication of 75% or hi~her indicates a fullopen nozzle (nozzle-limited) condition. Under this condition, fuel flow to the affected engine is reduced to maintain EGT within limits. If the

Ts amplifier fails during MIL or AB power, retard the throttle to maintain EGT within limits if flight conditions permit.

 

Ts AMPLIFIER SYSTEM

The T5 amplifier system maintains a preset

turbine discharge EGT within allowable limits

during MIL and AB power operation by varying

the exhaust nozzle opening. Operation is

automatic with ac power supplied by the engine

tachometer generator. If EGT is higher

than the reference temperature, the amplifier

causes the nozzle to open; if lower, the nozzle

closes. The system operates primarily in MIL

and AB power ranges.

 

 

Thanks for posting this.  I will read and digest this later, but this supports my earlier post suggesting that nozzle position might also depend on Mach and altitude (affecting EGT).

 

(This is In contrast with my post to which you replied here, which was just a description of the simplified diagram in which RPM and nozzle have a unique function.)

[bkthunder]

13 hours ago, DoorMouse said:

This only effects the thrust as you retreat the throttle? But resets once you hit mil? Or does this also effect your AB thrust capabilities? 

 

It affect thrust as you retreat the throttle, because the nozzle stays closed instead of re-opening. Once you hit IDLE it "resets" and resumes normal scheduling. Once you hit MIL again, the nozzles close up, and stay wrongly closed until you throttle all the way back. 

 

Have a look at the diagram posted before. 

[nessuno0505]

Why this bug is not even acknowledged by ED? What is missing? 

[Svend_Dellepude]

6 hours ago, nessuno0505 said:

Why this bug is not even acknowledged by ED? What is missing? 

 

It has a reported tag...

[nessuno0505]

I can't see it...

[Svend_Dellepude]

[Slice313]

I was going to buy the F-5E today or tomorrow before the sale expires but… with this kind of bugs being ignored…. Not a chance. I guess that checking the forums before a purchase is good practice to avoid frustration. I wish every plane was given the same amount of attention

[Rudel_chw]

7 minutes ago, Slice313 said:

I was going to buy the F-5E today or tomorrow before the sale expires but… with this kind of bugs being ignored…. Not a chance. 

 

I understand that slow bug-fixing is a pain, but this is hardly a game-breaking bug, I flew the F-5E a lot on its day and never even became aware of it.

I did flew on formation with other pilots, but I didn't rely on rpm settings to keep formation, instead relying on spatial cues between the cockpit frame and the other aircrafts.

 

I enjoyed my time with the F-5E a lot, as it is a simple aircraft to learn .. and it was a pleasure to be able to use the Natops manual of the real thing, as most details are pretty well simulated.

[Frederf]

Anyone else have issue of AB not lighting? When I go max idle max I get proper light off but max-mil-max often I don't.

 

It's really annoying to be falling out of the sky wondering where the thrust is when the levers are full forward.

[Machalot]

15 minutes ago, Frederf said:

Anyone else have issue of AB not lighting? When I go max idle max I get proper light off but max-mil-max often I don't.

 

It's really annoying to be falling out of the sky wondering where the thrust is when the levers are full forward.

Yeah, if you have the AB gated and go to MIL, then toggle the gate and push into AB, it will not light.  You have to momentarily back off MIL before pushing into AB.  I assume this is a bug.

[Svend_Dellepude]

14 minutes ago, Frederf said:

Anyone else have issue of AB not lighting? When I go max idle max I get proper light off but max-mil-max often I don't.

 

It's really annoying to be falling out of the sky wondering where the thrust is when the levers are full forward.

 

I experience the same if I do not pull throttles back far enough after using afterburner before entering afterburner again.

[Rudel_chw]

1 hour ago, Frederf said:

Anyone else have issue of AB not lighting? When I go max idle max I get proper light off but max-mil-max often I don't.

 

Just tried it, and it works for me .. of course the AB takes a few seconds to light, but that is true to the real aircraft, that could take up to 5 seconds to light its AB.

 

 

I use a Thrustmaster Cougar as throttle, no special gates, just proper calibration.

[Slice313]

10 hours ago, Rudel_chw said:

 

I understand that slow bug-fixing is a pain, but this is hardly a game-breaking bug, I flew the F-5E a lot on its day and never even became aware of it.

I did flew on formation with other pilots, but I didn't rely on rpm settings to keep formation, instead relying on spatial cues between the cockpit frame and the other aircrafts.

 

I enjoyed my time with the F-5E a lot, as it is a simple aircraft to learn .. and it was a pleasure to be able to use the Natops manual of the real thing, as most details are pretty well simulated.

Are there any other problems? I heard the FM model have big problems too, but I would like insight from experienced owners. 
 

Thank you

 

[Rudel_chw]

50 minutes ago, Slice313 said:

Are there any other problems? I heard the FM model have big problems too, but I would like insight from experienced owners. 
 

Thank you

 

currently it is possible to test fly a Module for up to 14 days, you could thus fly it and see for yourself 

[Slice313]

20 minutes ago, Rudel_chw said:

currently it is possible to test fly a Module for up to 14 days, you could thus fly it and see for yourself 

I know, but only people who have been flying it for a while can give back accurate info. I already know I would like flying it, I’m just concerned about possible long crippling bugs. Ty for your help

[Svend_Dellepude]

2 hours ago, Slice313 said:

Are there any other problems? I heard the FM model have big problems too, but I would like insight from experienced owners. 
 

Thank you

 

 

The FM has a good feel and it feels very much like a racecar. Just don't expect to take out F-15's or the like. The nozzle schedule is mostly something you notice when landing.

[Frederf]

14 hours ago, Rudel_chw said:

 

Just tried it, and it works for me .. of course the AB takes a few seconds to light, but that is true to the real aircraft, that could take up to 5 seconds to light its AB.

I use a Thrustmaster Cougar as throttle, no special gates, just proper calibration.

Cool for you. Here's a track which shows with just a few attempts giving the condition of both handles full forward indefinitely and no AB.

F5 AB fail.trk

[Rudel_chw]

42 minutes ago, Frederf said:

Cool for you. Here's a track which shows with just a few attempts giving the condition of both handles full forward indefinitely and no AB.

 

Could it be a HOTAS issue? ... why it would work for one people and not for others?

[Northstar98]

7 hours ago, Slice313 said:

Are there any other problems? I heard the FM model have big problems too, but I would like insight from experienced owners. 
 

Thank you

 

I can't say much for the FDM, but the RADAR has a very simplistic representation of clutter (and is simplistic in general), though this is maybe more minor.

 

The other big thing for me is that the SEARCH mode for the RWR still doesn't work properly, and hasn't for years (just over 4 years so far).

 

What's supposed to happen is that the SEARCH mode is supposed to filter out RADARs that show up an 'S', i.e EWR/GCI RADARs, which aren't (at least directly) threat emitters (such as acquisition/search RADARs directly associated with SAM systems, like the P-19). When SEARCH mode is enabled, these RADARs should be displayed, and when disabled they should be filtered out from the display (and I'm pretty sure the 'S' on the SEARCH mode button is supposed to blink in such a case - indicating that an 'S' type RADAR has been detected but is not being displayed).

 

What happens in DCS however, is that the SEARCH mode toggles between RADARs in a search/acquisition mode and a track/fire-control mode, necessitating that you press the button over and over again, whenever the emitter you're interested in changes mode.

 

The RWR itself also has a tonne of missing functionality, many of which also apply to the F-16CM.

 

I would definitely still recommend the F-5E, but these 3 things in particular are pretty problematic IMO, with barely any word from ED.

Edited July 10, 2021 by Northstar98

[Frederf]

Possibly because my throttle is producing an exact value output of 80% for an extended range (65-75% input).  It's not a precise thing a human is normally able to do. Actually I just changed my script profile to not have this flat spot (just simple 0-100 in = 0-100 out) and I can still reproduce the result. Slowly and gently put throttle from AB range until AB just barely goes out then move lever forward again.

F5 AB fail2.trk

[Machalot]

1 hour ago, Frederf said:

Possibly because my throttle is producing an exact value output of 80% for an extended range (65-75% input).  It's not a precise thing a human is normally able to do. Actually I just changed my script profile to not have this flat spot (just simple 0-100 in = 0-100 out) and I can still reproduce the result. Slowly and gently put throttle from AB range until AB just barely goes out then move lever forward again.

F5 AB fail2.trk 101.31 kB · 1 download

It seems like the AB ignite is triggered at a throttle position somewhere below MIL.  Have you tested how far you need to back off before pushing forward again to get a good light?  I have done it by feel, but you seem to have a more precise level of insight with your throttle axis. 

Edited July 10, 2021 by Machalot

[NineLine]

Dear all I have just tested and set to merge a fix for this issue. I hope to see it in an upcoming update. Thanks for your extreme patience on this, and sorry for the time it has taken to get corrected.