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JPTL Failure (battle damage)


Opalias

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Does anyone have the casualty procedure for a JPTL failure?

 

 

It seems to be a fairly common failure when damaged, I have been able to get back to the boat a few times with this failure, but have been unable to work out how to get enough engine power to land.

 

 

The JPTL seems to be tied into the water injection system, though even dry I seem to start getting the J polygon at much lower power settings especially as drop airspeed during the approach to the boat.

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I asked this once somewhere. Just turn it off. The switch is between the throttle and nozzle angle control lever. Then your throttle will have direct control of fuel input and can easily over-temp the engine at high throttle settings. You can try turning it off with an healthy engine to experience the effect.

 

Just turning the JPTL off will often not change anything, and a lot of times the engine goes out if the JPTL is damaged, so you might want to practice restarting the engine in mid-flight too :)

When you hit the wrong button on take-off

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EFC Emergency Procedures

 

I asked this once somewhere. Just turn it off. The switch is between the throttle and nozzle angle control lever. Then your throttle will have direct control of fuel input and can easily over-temp the engine at high throttle settings. You can try turning it off with an healthy engine to experience the effect.

 

 

Just turning the JPTL off will often not change anything, and a lot of times the engine goes out if the JPTL is damaged, so you might want to practice restarting the engine in mid-flight too smile.gif

 

That switch is there for the pilot to push through the limiters if they are descending too fast and need max performance to not crash. That switch only turns off the JPT limiters to allow the pilot to get as much performance as possible regardless of over temping the engine. The throttle has a spring stop at the max travel and you can 'push' the throttle farther to trip that switch.

 

If the system has failed it is better to go into Manual Fuel so you can maintain the limits yourself but the max RPM in man fuel is 111%. You cannot air restart the engine in flight as the ignitors are not modeled for that and the boost pumps are not actuated when the air restart switch is pressed. To verify this, check this before you start the engines. Turn on batts, do a lights check, ensure you have both boost pump lights (meaning they are off) and then press the air restart switch. IRL both ignitors can be heard popping and both boost pump lights go out, meaning they are energized by DC power from the battery, which is how the engine gets fuel flow to restart in the air. In manual fuel the ignitors pop continuously, as in they never stop as long as you have it on, which is also not modeled (already reported to DECOY).

 

Does anyone have the casualty procedure for a JPTL failure?

It seems to be a fairly common failure when damaged, I have been able to get back to the boat a few times with this failure, but have been unable to work out how to get enough engine power to land.

 

The JPTL seems to be tied into the water injection system, though even dry I seem to start getting the J polygon at much lower power settings especially as drop airspeed during the approach to the boat.

 

This is an intricate system and you first need to determine which failure has occurred. If you have a Master Caution EFC and JPTL light, first ensure DECS enable switch is ON and switch DECU lanes and see if you get control back (called a single lane failure). Normally the jet does this automatically for a single lane failure, but it is not modeled AFAIK. If you do have a Master Warning EFC light (called a dual lane failure) then you need to select Manual Fuel. The JTPL system is actually controlled by the Electronic Fuel Control (EFC), which is controlled by the two Digital Engine Control Units (DECUs). If your EFC system or the JTPL system is damaged (two in the same) then you are supposed to put the jet into Manual Fuel, which is literally you using the throttle to tell the jet (the Fuel Metering Unit, FMU) how much fuel to put in the engine. It is up to the pilot to maintain all operational limits however, and is very easy to both over temp the engine or over speed the engine. :book:

 

Manual Fuel does not have max limits that are automatically controlled, hence the name of manual fuel. The maximum RPM you can achieve is 111% and you need to keep the temp below 780°C when your nozzles are below 14°, which would put you in Short Lift Dry (normally) or 710° when your nozzles are above 14°, which would put you in Max Thrust (normally) (see chart below for performance limitations). Unless you absolutely have to do a VL, perform a Variable Nozzle Slow Landing (VNSL = RPM 80-95%). Attempt to keep RPM below 100% to max extent possible and if VL is a must (simulated boat ops) reduce weight to minimum practical amount and use smooth throttle deceleration.

 

 

IRL water does actually flow when it is selected while in manual fuel, but I have not tested this out in this module, I might give it a go and report back here after I test it. You will not get the associated rise in RPM IRL, but it does give it to you in the sim, which is incorrect and I reported it to DECOY already.

 

 

kEiAFm0.jpg


Edited by vstolmech513
Bugs reported to -DECOY-
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Ok, so after further testing in Man Fuel, the majority of the system is modeled correctly. If you are in Man Fuel water will flow in T/O around 105% (should be 102.5ish so close enough, but it will flow) and around 765°C in LDG. I had no issues maintaining limitations manually and performing a VL was doable especially if you dump fuel and keep your weight reasonable. Bold face procedures (Emergency Procedures) call for jettisoning all stores if you have to select Man Fuel anyway so keeping the weight down should be easy enough and having water to keep the JPT down helps get you back on ship if you absolutely have to do a VL. The maximum RPM is 111%, which is modeled correctly, so you will more than likely only ever see the R power hex in the HUD especially if you have your H2O in LDG.

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I tried the settings as described above and was still unable to get water to flow. It may have been damaged as well, obviously its hard to know what is damaged, its probably also not a great sign that I get hit enough to retry this frequently. But not matter what settings I had, and even at very low weights, water was static and the J polygon hits very quickly.

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Posting a track would help see what is going on, that way we can take over when it happens to see what we get. Might be a bug with the water system or the EFC system, and also to see what your JPT is when you get the hex. I did not have any damage when I was testing the Man Fuel system but I'll see if I can take some rounds and replicate if I have time.

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