Engine Longevity Problem

[WR269]

Maybe wait for Razbam to respond instead? They did have people with access or previous fliers of Harriers so my guess is they modelled what they did for a reason.

 

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[Whuping]

You mentioned the water didn't come on, may i suggest more throttle, the engine only applies water at the higher settings. If it doesn't come on and you have heat, I may suggest the counter intuitive choice of more throttle.

 

I wish I COULD increase my maximum throttle past 100%. If I increase it further I'd fear I'd break my precious throttle.

 

But as far as I have read through all these posts - I have come to a conclusion that the DECU switch is not performing its intended function? Regardless, my second problem still remains that even if the Engine Life is in whatever state, doing a GROUND REPAIR won't fix it to its normal state.

 

I'll perform more extensive tests considering one of the individuals here manage to fly and land more than SIX times. Impressive. That seems like a far fetch goal for me. The highest was Three for me lmfao.

[Whuping]

Swag.

 

I'm actually quite relieved it is User Error. :doh:. I've revised my techniques and have successfully landed and taken off more than twice with little problems. I suspected it was because of the throttle at 100% (A-10C Habit).

 

It's much MUCH better knowing that little information. I suggest a little warning on the pocketbook in big bold red letters:

 

PROLONGED MAX THROTTLE WILL DAMAGE YOUR ENGINE AND YOU WILL DIE. HORRIBLY.

 

lmao

[Scrape]

I see that JPTL throttle override in the manual. Thanks for pointing it out. I don't think that is the problem - it just seems that the power loss is there to "punish" the player (for lack of a better term) for exceeding limits that the DECU should be protecting in the first place. After all - the throttle is only a switch that transmits TLA to the DECU. The DECU controls thrust and maintains the engine within limits - if it is correctly simulated.

 

I understand engine limits very well - and you could exceed the max continuous power time limit. But again that doesn't degrade the power the engine can produce. It just shortens the life of the engine.

 

Somewhere in the Actual manual it even mentions how many minutes less engine life vs JPT.

 

The key point is it is unrealistic for a jet turbine engine to wildly degrade its available thrust in a short time period. Short of taking damage of some sort. The throttle isn't a "destroy engine" switch.

 

Older engines I fly usually just have a higher EGT to produce the same thrust. They don't loose power to the point you cannnot sustain flight. Which has happened to me several times in the curent release of the AV8B.

 

It's not there to prevent any damage all the time not matter what. Any modern jet can be overflown by its pilot. Real flying is about staying within limits, and DCS is growing more detailed in the nuances of flight. Even modern aircraft have limits.

 

It's not right to compare two different engines and EGTs. Other aircraft have different airflow, compressor stages, blade angles, operating design altitudes, not to mention the big difference, metal alloys. If 645 is the continuous operating temp of the Harrier's engine, then it is. There is documentation to back it up. For various reasons and factors this is the case. Engine building is no mean feat, and engines don't melt/fail from over temp, they degrade. That's what we've been given here. Proper engine degradation from heat. This happens not just from blades melting, but there are a lot of other parts to consider when it comes to heat limitations. Another big factor is heat soak from combustion. This is where the internal parts arrive at a temp that is too hot and exceeds the cooling method, so now the combustion phase is negatively affected. Higher combustion temps mean less power overall. The same thing can happen in any motor, even a car engine.

 

The Harrier is modeled well. Mind the EGTs and she will bring you home.

[bart]

Here's my take on it.

 

 

I haven't had any experience working on this version of the Harrier, but I did work on the older versions GR3/FRS1. We did tie down ground runs on them up to full power and as long as you didn't trip the limiter switch it could sit there quite happy at full power almost until the fuel ran out! the limiters stopping it from running too hot or too high rpm.

 

 

The JPT/RPM limiters are there so the pilot doesn't have to worry about his throttle position, engine temps etc. as long as the engine accel was within limits and he had duct pressure he was good to go. On some aircraft they had a placard figure for the engine and on T/O the pilot would run the engine up to full power and check what he was seeing on the gauge to what the placard figure was and he knew if it was within limits he was good to go.

 

 

The limiter switch on the Harrier had tell tale wire on it so if in flight the pilot tripped the limiter switch we could tell on an after flight servicing where it was checked every time. If he had tripped them we would have a laid down procedure we had to follow to health check the engine, boroscope inspection, pull the mag plugs etc. and if all ok reset the switch and note down in the log what had happened.

 

 

Now a gas turbine's thrust drops off as the engine ages, so to maintain the thrust rating the ground crew would do periodic performance runs on it and if necessary dial in more fuel therefore maintaining the thrust rating of the engine. But the side effect of this was the TBT/JPT temps would increase. After several tweaks of the fuel over a few hundred hours of use it would reach the max limit it could run at and we would then change the engine as it was considered life ex.

 

 

Now from here on I'm speculating as I have no first hand knowledge of our DCS Harrier IRL so could be wrong but, should we not be able to fly around at full throttle as long as we don't trip the limiters? I believe these are still WIP so what we are seeing here could be the effect of no limiter control and consequential damage to the engine?

 

 

The hexagon symbol on the STOL HUD, once its a whole hexagon and got the extended leg, is saying that we have reached the limits of the engine as controlled by the limiters? and were not going to have enough thrust to hover if its not hovering already. Time for an alternative plan and a short landing may be in order!

 

 

Here's a scenario taken from a book I'm reading about the GR7 in Afghanistan. Two Harriers were flying around and they get an emergency call.....troops in contact. So they start heading for the area at full throttle. He (the pilot) doesn't want to be worried about whether his engine is over temping or over revving or what not, he just wants to plant that throttle to the max stop and not worry about it......let the limiters do their job.....he's too busy getting ready for the up and coming confrontation.

 

 

Currently on our Harrier if we did that we would damage the engine. It seems to be more prone on a heavy aircraft too. I was flying it this morning with 2 external tanks on, 6 Mk 82's and a Targeting pod. I used water on T/O then turned it off and was flying around at 400kts, opened the throttle to full and soon was presented with and OT caption and subsequent downgraded engine, the rpm was only going to 94% at full throttle instead of 104% or 106%? cant remember what max is now.

 

 

The jist of this huge post is.....I think our engine seems very prone to damage at the moment, to me anyway, or the Limiters are either bugged or WIP.

 

 

Fantastic module though......just loving it to bits!

Edited December 3, 2017 by bart

[Whuping]

 

I'll leave this here. Taken from the Pocketbook Page 39.

 

EDIT: And if I haven't said my praise to the module - it's dank. Having a blast.

[Sneak69]

 

I'll leave this here. Taken from the Pocketbook Page 39.

 

EDIT: And if I haven't said my praise to the module - it's dank. Having a blast.

So is this for the total flight time, or can you give it a break at lower rpm and then get your full 15 minutes back at max?

 

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[Ramsay]

So is this for the total flight time, or can you give it a break at lower rpm and then get your full 15 minutes back at max?

Not sure, I'd guess the answer is it depends.

 

The engine life of the 408A PPC 192/408B is 1,000 hours/ 50,000 counts

• SLW with JPT 800° is 1,500 counts per minute, so 15 minutes = 22,500 counts = 45% of the total engine life of the most robust engine. However the water supply is limited.
   
  
• SLD with JPT 780° is 600 counts per minute, so 15 minutes = 9000 counts = 18% and in theory you could burn out an engine in 83 minutes. However after 15 seconds there's danger of turbine damage and you need to derate to 3/6 of the Power Margin hexagon (10 minute limit)

I'd say we shouldn't see Harriers falling out of the sky, unless they've been at max (full hexagon) for +30 minutes but it'd be nice to have access to the MPCD engine management page to see how well (or poorly) we've been managing the engine life.

 

Note: Each side of the JPT Power Margin hexagon = 10°C with it's 'tail' equalling the last 5°C

 

Page 415, NATOPS Flight Manual, 15 March 2008, A1-AV8BB-NFM-00

 

Edited December 3, 2017 by Ramsay
Add limits for dry

[Sneak69]

Not sure, I'd guess the answer is it depends.

 

The engine life of the 408A PPC 192/408B is 1,000 hours/ 50,000 counts - SLW with JPT 800° is 1,500 counts per minute, so 15 minutes = 22,500 counts = 45% of the total engine life of the most robust engine.

 

I'd say we shouldn't see Harriers falling out of the sky, unless they've been at max (full hexagon) for +30 minutes but it'd be nice to have access to the MPCD engine management page to see how well (or poorly) we've been manging the engine life.

 

Page 415, NATOPS Flight Manual, 15 March 2008, A1-AV8BB-NFM-00

 

According to that we get 833 minutes at combat thrust. So we shouldn't be getting damage done for flying at full for a play session. The damage must be coming from taking off and landing. Which would make sense on the 2nd or 3rd time rearming depending on how long you were flying for.

 

I wonder if they can make it so a repair will zero out the damage. Although not realistic it sort of sucks from a gameplay/immersion element to get a brand-new bird each time.

 

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[Scrape]

It sucks for immersion that a system is modeled properly? Gameplay is better when an aircraft is modeled not only for its performance, but its limitations.

[Esac_mirmidon]

+1 Scrape

[Sneak69]

It sucks for immersion that a system is modeled properly? Gameplay is better when an aircraft is modeled not only for its performance, but its limitations.

I agree fully, was just thinking about getting out of slot and back in on mp servers. Its not a big deal over all.

 

I didnt say get rid of it (if its realistic), just have the option to repair it out. Like most damage you get while flying in dcs the repair shouldn't fix it (that fast anyway) but it does so you can keep flying.

 

Im actually impressed about complexity of work they did into the flight model.

 

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Edited December 3, 2017 by Sneak69

[Sandman1330]

I think there's still a wildcard here somewhere.

 

I just finished a session where I was able to takeoff vertically without going anywhere near limits, but after a circuit coming back, couldn't hover land without exceeding. ???? I can takeoff straight up, but can't come to a hover to land? The takeoff should require far more power.

 

I can be hovering without seeing the hexagon at all, then all of a sudden, master caution, overtemp. I think there's still something that's inconsistent in the modelling of the limitations...

[Texac]

Or you are simply doing something wrong you have to get used to it. It works fine for me.

 

Taking off with 21000 lbs, cruising around without exceeding engine limitations for to long, head back to base with a bit of fuel left and VL without any problems. The engine still runs as it did on take off and even after a third, fourth, fifth landing it still reaches to 113% RPM while the acceleration times are all identical.

 

And make sure that your start up procedure is correct.

Edited December 3, 2017 by Texac

[Sandman1330]

Or you are simply doing something wrong you have to get used to it. It works fine for me.

 

Taking off with 21000 lbs, cruising around without exceeding engine limitations for to long, head back to base with a bit of fuel left and VL without any problems. The engine still runs as it did on take off and even after a third, fourth, fifth landing it still reaches to 113% RPM while the acceleration times are all identical.

 

And make sure that your start up procedure is correct.

 

I’m doing a runway (we’ll ship lol) start, so aircraft already running.

 

The majority of the time it’s good, but just once in a while, the bottom seems to fall out, even when I’ve exceeded no limits that I can tell. I’ll keep practicing but it definitely still feels inconsistent...

[3mta3]

I hope the developer will reconsider the unrealistic loss of thrust following a max continuous power time limit exceedance.

 

First of all the DECU is designed to protect the engine from damage - over speeds and temps that actually could damage the engine.

 

The other time limits are designed to extend the life of the engine. You can exceed max continuous thrust all day and not damage a engine - but mx is going to be unhappy as they are going to need to perform inspections and the remaining time until overhaul will be reduced.

 

This is a combat aircraft designed to be flown with minimal attention to engine limits by the pilot - because that's what the DECU's job is - protect the engine.

 

Check every TO procedure in the manual - it says "Throttle - Full". Why? The DECU. It is managing the engine power.

 

I love this jet, but real jets don't suddenly lose thrust like this - short of a bird strike or other damage. Thanks again for a fun little jet.

[comie1]

Again.. you guys sure it's not user error cause I ain't having this problem

[Texac]

If you take a look at CptSmiley's post at hoggit you'll get a better understanding of the engine limits and how to deal with them in DCS.

 

- There are a things are not modeled fully...DECU being off, MFS logic, JPT limiter switch off, Logic to disable JPT limiter when throttle pushed, and P3/Fuel Flow limiting behavior.

 

- The longer you stay in the limit the more "damage" you are causing.

 

- limit must be maintained by pilot and are not automatically limited by the DECU.

 

- If you do cause enough damage you do eventually get to where values are "out of tolerance" and you do get warnings but you can mildly damage the engine in such a way that it doesn't trigger faults.

 

The best way to avoid any loss of power or damage to the engine is to stay under any of the limits at any time so flying with less than 102% RPM and 645° JPT should keep the engine from any perfomance hit.

 

If I'm understanding that correct. And remember the aircraft has been released a few days ago into Early Access state.

Edited December 3, 2017 by Texac

[Sneak69]

So the things to protect arent fully in yet. Makes sense.

 

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[bart]

If you take a look at CptSmiley's post at hoggit you'll get a better understanding of the engine limits and how to deal with them in DCS.

 

 

 

The best way to avoid any loss of power or damage to the engine is to stay under any of the limits at any time so flying with less than 102% RPM and 645° JPT should keep the engine from any perfomance hit.

 

If I'm understanding that correct. And remember the aircraft has been released a few days ago into Early Access state.

 

 

 

Yeah, now this makes much more sense to me after reading the Dev's comments in your post. Those systems not being modelled would explain a lot.

 

 

Now I know the limits, and why they exist, i.e.- certain stuff can't be fully modelled by DCS, I know what I'm looking for and why in regards to the engine management.

 

 

Good post Texac.

[ESAc_matador]

I would like to see, one day.... that DCS can keep record of the aircraft state. Batts, engine, etc. You can always reset, but for campaigns would be awesome.

[Delareon]

I tried to kill the Engine yesterday.

From my experiments it seems like the DECT is Buggy, which causes some Problems.

 

Following Experiments:

Vertical Take Off,

Gaining Speed and back to a Vertical Landing.

Then doing this all over again until the Engine dies and you cant take off or crash while trying to hover.

 

With DECT on i can barely do 2 starts and the second landing doesnt work out well.

 

With DECT off i can do it 6-7 times before the Engine dies.

 

Well even if i did something different between the flights with and without DECS, there wasnt that much difference to cut the Engine Lifecycle in half.

[jejsus]

I've had power loos due to OT, but since then I keep my eyes on % and EHT. I never had power loss after paying attention to the limits. Full throttle only for the roll, as soon as airborn not above 102%. I land every time with a gentle transition into vertical landing.

[Texac]

Thanks for the info CptSmiley!

 

I for myself really like to have another factor that requires attention and additional workload to maintain the engine at life.

[Raven (Elysian Angel)]

Indeed very useful information, thanks!

Personally, I stopped having engine thrust issues on 2nd/3rd take-off within the same mission, once I started paying close attention to the R/J limits :)