JPT -REG. TEST

Small bug with indication of JPT -REG. TEST procedure.

As of now positioning JPT -REG. TEST switch to position I and II will illuminate JPT 700°C lamp in both C and ZA.

According to the manuals JPT -REG. TEST switch in position II should illuminate JPT 730°C lamp.

*bump* found this thread cause I noticed this too today.

Still an issue in 2.5.4 stable branch, so topic could be moved to bug section.

Been broken for ages, still broken in the latest OB too.

Just tested and this is still an issue

You know, it is probably just a simple copy/paste error they missed when coding. I tried looking, with no luck, but maybe if we submit a proper bug fix request and support it, it can be fixed.

It is a lot of work building those lamps and I would love it if they all worked correctly. :)

Or WTF, maybe this particular batch of machines had the upper annunciator disabled and only used the lower bulb for both. The thing is, you don't know one way or another - well unless you happen to own a RL example and are very well versed with all the RL mods and subtypes and what have you ;)

EDIT: And yet, it most likely is an ED bug that's been there for ages already...

so WTF?

I get it, no more trying to get bugs fixed.

No, of course it should be fixed, was just flapping my lips. IIRC the release version of the module had it right, but the next patch broke it already and it has been broken ever since.

Quite annoying bug actually. Also the switch shall be "spring loaded"

Yeah, still broken the last I checked. Kind of does not increase your confidence in their ever fixing any of these, TBH.

I agree this would be great to have this fixed, also don't know if this is a bug but putting the JPT REG Test on position II after startup stopped the engine for me and my friend. I think I remember I read that it is not recommended to use it after engine start as it interferes with the fuel shutoff valve or something, but why would only the button II stop the engine then and not both?

Again, maybe this is accurate but I was curious about why exactly it behaves that way.

On 4/30/2021 at 6:16 PM, Raphy said:

I agree this would be great to have this fixed, also don't know if this is a bug but putting the JPT REG Test on position II after startup stopped the engine for me and my friend. I think I remember I read that it is not recommended to use it after engine start as it interferes with the fuel shutoff valve or something, but why would only the button II stop the engine then and not both?

Again, maybe this is accurate but I was curious about why exactly it behaves that way.

With the WOW increasing the engine temperature to 700°C (actually 685°C+-15°C) will only cause fuel regulator to limit fuel supply to limit engine over temperature. But if temperature rises to 730°C (actually 715°C+-15°C) with WOW fuel shut off valve will close causing engine to shut down. If in air only warning light will illuminate without engine shut down, that will only happen after landing with WOW automatically.

Now I am not sure if the test switches actually energize whole limiting system or just the C/W lights. If they energize whole system then only test pos. II would close the fuel valve and shut the engine down.

I originally thought that JPT Reg Test II should light up 730°C and the switch does not work correctly. However, lately I was reading operation manual to AI-25TL engine and it indicates some differences depending on the WOW switch. Now I don't claim to understand everything properly, but I'm now prone to believe the implementation in the module is good:

• On the ground, for the position II, the system only lights up 700°C and stops the engine.
• In the air the engine is not stopped, but 730°C warning is lit up - and stays so until fixed by the ground crew.

The sections from the engine manual are (LIMITATION mode is tested by position I, SHUTDOWN mode is position II):

And a bit later:

L-39 module really does NOT shut down the engine in the air, light stays on, I just don't know how that shutdown on the ground works and what exactly is "soon after" regarding "the nose wheel comes in contact with the ground". I landed with the light on (after flipping the switch to II in-flight) and it doesn't want to stop "by electrical means".

Reading the manual p83-84 actually checks with the engine manual, so I'd say the lamps 700/730 work fine, there is an obvious power limitation in flight when the JPT regulator engages (be it for EGT or because of the TEST II position)... the only thing I'm still waiting for is that engine shutdown on the ground.

But I'd argue that the section on manual p85 is not correct (emphasis mine):

Quote

The spring-loaded RT-12 JPT regulator test switch (JPT REG TEST), located on the right panel in the front cockpit, is intended to check system functionality when the engine is not running. It is necessary to press and hold the switch in position I and check if the J.P.T. 700°С warning light is on, indicating normal system operation. Repeat the same for position II – the J.P.T. 730°С indicator will come on. It is not recommended to toggle this switch after engine start, because it enables the fuel limiting valve.

I don't know whether the real switch is or is not spring-loaded, but the switch will not show 730 on-ground. The last sentence could also clearly state that the engine will be shut down on the ground, the fuel limiting valve is relevant for flight.