H2O Supply / Coombat Thrust / Engine Life

[Hummingbird]

First question first: How long does the water supply last? Anyone know?

 

Been wondering about this since I sometimes activate 'combat thrust' which AFAIK enables the water injection for a period of usable boost. Question is for how long however?

 

Next question: Does anyone know for how long you can have a full hexagon displayed on the HUD before the engine takes damage? Reason for asking is I am VIFF'ing a lot during combat, but I notice the hexagon almost immediately forming as I start VIFF'ing. Maybe I need to have combat thrust enabled before doing any VIFF'ing to ensure proper cooling?

[RuskyV]

Hi Hummingbird,

 

It depends on many factors the main ones being weight, altitude, air temperature. These are key factors in how long you can sustain a hover or how long you can use the combat power switch.

 

The higher the throttle setting used and the higher the angle of the nozzle will determine how much heat is generated and the three main factors mentioned above will have an impact on performance and duration.

 

The below picture is a snippet from the AV8B manual showing duration limits for the engine jet pipe temperature. In this chart focus on the JPT temp and the A B C D E duration limits and cross reference the numbers written in the notes and read the off the corresponding numbers against the text at the bottom of the chart to see what the causes are.

 

You need to monitor the JPT temperature as this will tell you how long you have before you start losing engine performance and ultimately damaging the engine.

 

hope this helps.

Edited December 15, 2017 by (504)Blade

[Hummingbird]

Excellent stuff Blade, many thanks :thumbup:

 

So just to make sure I've understood it right, I mainly need to focus on the Jet Pipe temperature when VIFF'ing, i.e. if the JTC is between 750-765 C then I have at worst 2.5 min before I need to power down for about a 1+ min at 710 C. After that I can start over again by holding to the same limits and not lose engine performance?

Edited December 15, 2017 by Hummingbird
Small typo

[ESAc_matador]

The use of water, although it gives you more RPM, your JPLT is lower... so, do not try to use full rpm without water if possible. If you have the correct weight when landing, you should have enough water.

[RuskyV]

Your welcome, glad i could help.

 

In short Jet pipe temp is the key indicator to how much vectoring you can do, the higher the temperature the less time you have to do it.

 

Have fun mate.

[Nealius]

Is this actually modeled yet? The other day I was on the ramp in a heavy jet and decided to slam throttles forward with 84-degree nozzles, no water. Nozzles glowing, Master Caution, Fire warning, I kept the engines running for a good 3 minutes after that and nothing happened. Engine Life on the ENG display didn't even change.

[Madbrood]

Absolutely. It's possible to Over Temp the engine and then be unable to produce max RPM and thus max thrust.

[Nealius]

Ah, so the damage is more subtle than failure of the engine. Cool.

[NeilWillis]

Is this actually modeled yet? The other day I was on the ramp in a heavy jet and decided to slam throttles forward with 84-degree nozzles, no water. Nozzles glowing, Master Caution, Fire warning, I kept the engines running for a good 3 minutes after that and nothing happened. Engine Life on the ENG display didn't even change.

 

You may have noticed that a lot of systems are still to be modelled, so I dare say this is one of them. We get physical degradation in the way the engine power fades, but I suspect there is far more to come on this subject before the Harrier reaches it's final form.

 

It's just work in progress, so hang in there.

[QuiGon]

Ah, so the damage is more subtle than failure of the engine. Cool.

Yes, it is. On my first flight with the Harrier I was fooling around with VTOLing and probably exceeded the limits quiet a lot, because at one point I wasn't able to produce enough lift to leave the ground anymore. I now know why: The engines were degraded. :music_whistling:

[Hummingbird]

Here's a video that answered my question in regards to water supply duration (5:35 min):

 

kyS1QVjmDWs?t=335

 

In short you've got 1.5 min before water runs out. (The engine limit chart eludes to this as well)

 

Also this means my initial thought that the combat thrust setting involved water injection was wrong, the combat thrust setting apparently just allows for a higher thrust setting, however only for 10 min at a time as the chart provided by blade illustrates.

 

As soon as you turn the nozzles however, like in the case of VIFF'ing, the RPMs increase further regardless of throttle setting (no idea why), and the JPT increases further.

 

Thus if the ingame model follows the chart then if we look at the time limit D you should be able to VIFF for about 2.5 min at 111% thrust & 765 JPT without any engine degradation, but I'm not sure that's doable ingame?

Edited December 15, 2017 by Hummingbird

[Hummingbird]

Next question then becomes: Can you have the 'Combat Thrust' button activated for an entire flight without problem as long as you don't throttle past the engine temp/time limits?

 

i.e. does the CMBT button merely increase the available top end power?