WOW. Harrier engine changes: Has our hover ability been nerfed?

[Nemesis44UK]

On 5/15/2021 at 3:17 PM, Aernov said:

Did anyone test how engine damage is modeled in our Harrier? 120% RPM is limited to 15 seconds, how would exceeding this time limit affect engine performance? Will it noticeably degrade if this overtime is like 5 seconds? Also, are there plans to enable engine life count dissipation (as an estimate of engine's probable datum deviation and it's resource/stress tolerance)?

I heard on The Fighter Podcast a Harrier pilot, who said that the 120% RPM is an absolute emergency type situation. They don't train for it and don't use it in day to day flights as it is too taxing on the engine, which is an absolute pig to maintain anyway.

Edited July 5, 2021 by Nemesis44UK

[Holbeach]

 

This shows a full forward nozzle approach, something I hadn't thought of trying.

 

..

[horstweihrauch]

3 hours ago, Holbeach said:

 

This shows a full forward nozzle approach, something I hadn't thought of trying.

 

..

What a damn cool jet the harrier is🤌

[pappachuck]

On 5/10/2021 at 7:20 AM, Vakarian said:

They did fix it. It was ridicuously overpowered before latest update.

 

Look here at the comparison charts to see how badly did Harrier overperform until latest update:

 

 

That is incorrect, now it seems the engine has the thrust curve of the Pegasus 11-21 and no longer the Pegasus 11-61.

[pappachuck]

1 hour ago, Malakhit said:

 

The Pegasus 11-61 is for the AV-8B+. We only have a standard AV-8BNA, so the 11-21 is correct.

Well, that is incorrect.
The AV-8B N/A also fields an updated version of the Rolls-Royce Pegasus 11-61 (F402-RR-408) vectored-thrust turbofan engine.

It is also on the module description: https://www.digitalcombatsimulator.com/en/shop/modules/av8bna/

The AV8B N/A is the version they modelled which is after 2010 and has the Pegasus 11-61. AV-8B N/A + also has the pegasus 11-61 and is basically the same airframe but the nose.

[Vakarian]

12 hours ago, pappachuck said:

 

That is incorrect, now it seems the engine has the thrust curve of the Pegasus 11-21 and no longer the Pegasus 11-61.

Hmm, that's interesting. Could you elaborate what exactly is wrong? I'm genuinely curious as couple of people in the thread I linked did some testing, read the charts and told that it's now supposedly correct.

 

If you can show some evidence what is wrong, maybe we can push it to RB to get it fixed?

[pappachuck]

On 7/6/2021 at 2:03 AM, Vakarian said:

Hmm, that's interesting. Could you elaborate what exactly is wrong? I'm genuinely curious as couple of people in the thread I linked did some testing, read the charts and told that it's now supposedly correct.

 

If you can show some evidence what is wrong, maybe we can push it to RB to get it fixed?

The evidence is on the NFM-000 and NFM-400.

I agree the older Flight Model was too off, however this one is aprox. 15% underpowered.

 

There are other aspects to the graphics that is not listed, they are assuming 95% of the total engine output as safety margin. So even if the currently model was for the engine  F402--RR--408 (Pegasus11-61) it would need to be slightly above of what the manual states to match what the aircraft would output.

 

You can confirm on figures:

Maximum Corrected Hover Capability, Remarks engine: F402--RR--408 on Figure 3-8

Hover Capability Dry, Remarks engine: F402--RR--408 on Figure 3-10

Vertical Takeoff Capability, Remarks engine: F402--RR--408 on Figure 3-12

 

Remember that the engine F402--RR--408 (Pegasus11-61) is capable of aprox. 22,200 lbs of static thrust running dry in optimum ICAO conditions. There are engineering tables which states how much loss of thrust according to the Reaction Control System required flow rates, and varying conditions (temperature, air pressure, ....). From those tables they derive (with a safety margin) what is given to the pilots and what you can see on NFM-000 and NFM-400.

 

My personal opinion is that RB misunderstood the tables and made the engines slightly closer to the F402--RR--406 rather than the F402--RR--408.

 

The only way to tell for sure is if someone help me extract their code and run on MATLAB.

[Bog9y]

20 hours ago, pappachuck said:

The evidence is on the NFM-000 and NFM-400.

I agree the older Flight Model was too off, however this one is aprox. 15% underpowered.

 

There are other aspects to the graphics that is not listed, they are assuming 95% of the total engine output as safety margin. So even if the currently model was for the engine  F402--RR--408 (Pegasus11-61) it would need to be slightly above of what the manual states to match what the aircraft would output.

 

You can confirm on figures:

Maximum Corrected Hover Capability, Remarks engine: F402--RR--408 on Figure 3-8

Hover Capability Dry, Remarks engine: F402--RR--408 on Figure 3-10

Vertical Takeoff Capability, Remarks engine: F402--RR--408 on Figure 3-12

 

Remember that the engine F402--RR--408 (Pegasus11-61) is capable of aprox. 22,200 lbs of static thrust running dry in optimum ICAO conditions. There are engineering tables which states how much loss of thrust according to the Reaction Control System required flow rates, and varying conditions (temperature, air pressure, ....). From those tables they derive (with a safety margin) what is given to the pilots and what you can see on NFM-000 and NFM-400.

 

My personal opinion is that RB misunderstood the tables and made the engines slightly closer to the F402--RR--406 rather than the F402--RR--408.

 

The only way to tell for sure is if someone help me extract their code and run on MATLAB.

I'm really curious to see exactly how the current engine model is 15% underpowered.  Can you please provide a clear graph or picture or some kind of proof of this?

With regards to the safety margin you mention, are you saying there is an additional 5% margin on top of the 3% margin already implemented for the VTO graph? 

For the VL graph there is a 5% margin implemented, are you not confusing the 95% margin with that?  

If I remember correctly the DCS performance conforms to what the VTO & Hover graphs are depicting, with a small margin but it would be good if you did some tests to show that it is incorrect and provide the proof.   

 

When it comes to climb performance the RB flight & engine performance model reflects the figures depicted in the TIME TO CLIMB/DISTANCE TO CLIMB/FUEL TO CLIMB graphs really closely. Upping the engine performance would probably lead to the climb performance being wrong again. Unless they modify the drag and weight too.  

 

Extracting the code? I doubt that will happen but worth asking RB. Message Helljumper with that request, he may be able to help. 

 

You may be absolutely right with all this, it's just that the model closely resembles what graphs that are available to the public depict. So please don't take offence to me questioning what is correct.  Unless we are reading these graphs wrong like you said and you can point us in the right direction where exactly we are going wrong?  It sounds like you have knowledge of the Pegasus engine, are you an engines mech/engineer? 

 

 

[pappachuck]

On 7/8/2021 at 4:24 AM, Bog9y said:

I'm really curious to see exactly how the current engine model is 15% underpowered.  Can you please provide a clear graph or picture or some kind of proof of this?

With regards to the safety margin you mention, are you saying there is an additional 5% margin on top of the 3% margin already implemented for the VTO graph? 

For the VL graph there is a 5% margin implemented, are you not confusing the 95% margin with that?  

If I remember correctly the DCS performance conforms to what the VTO & Hover graphs are depicting, with a small margin but it would be good if you did some tests to show that it is incorrect and provide the proof.   

 

When it comes to climb performance the RB flight & engine performance model reflects the figures depicted in the TIME TO CLIMB/DISTANCE TO CLIMB/FUEL TO CLIMB graphs really closely. Upping the engine performance would probably lead to the climb performance being wrong again. Unless they modify the drag and weight too.  

 

Extracting the code? I doubt that will happen but worth asking RB. Message Helljumper with that request, he may be able to help. 

 

You may be absolutely right with all this, it's just that the model closely resembles what graphs that are available to the public depict. So please don't take offence to me questioning what is correct.  Unless we are reading these graphs wrong like you said and you can point us in the right direction where exactly we are going wrong?  It sounds like you have knowledge of the Pegasus engine, are you an engines mech/engineer? 

 

 

 

I am a mechanical engineer and just like to spend my free time messing with simulations. To summarize: a flight model for VSTOL aircraft is a extremely complex topic and reverse engineer the aircraft from performance charts given to pilots is not ideal.

 

This is a brief book on the Aerodynamics of VSTOL aircrafts from the time the Harrier was developed, it gives a glimpse about the topic.

https://apps.dtic.mil/sti/pdfs/AD0688921.pdf

 

There are lots of Books and publications specially on AIAAA and recently formed a VTOL journal.

It is a complex topic and It is not that RB or the people is reading the graphics wrong, you are not exposed to the complete picture. It is necessary to dig some performance engine tests and apply that to the right Flight Model equations in order to derive a precise model of the Harrier. Currently RB team did the best they could with the USMC manual which is pretty good for a videogame but it is not quite yet good model for a simulation.

 

The best way is to find Academic information.

[TLTeo]

On 7/7/2021 at 8:09 AM, pappachuck said:

The only way to tell for sure is if someone help me extract their code and run on MATLAB.

I don't think that's possible given that DCS EFMs are written in C++ and encrypted.

 

Just an idea - could it be that both thrust and drag are too small, so that when flying at high speeds the errors on both kinda balance each other out and the aircraft matches the performance charts, but during VTOL you notice the lack of thrust but not the lack of drag?

[Fri13]

1 hour ago, TLTeo said:

Just an idea - could it be that both thrust and drag are too small, so that when flying at high speeds the errors on both kinda balance each other out and the aircraft matches the performance charts, but during VTOL you notice the lack of thrust but not the lack of drag?

 

I think you are on something. As it feels that Harrier accelerate too quickly. Regardless it having a climb to altitude record faster than even F-15C to 9000 ft and then Eagle goes pass. The Harrier doesn't seem to have a drag at slow speeds in hover and such. 

 

Talking about full 92° forward thrust and full flaps and landing gear and the plane does not seem to stop so fast from 100 knots as it does accelerate from 0 knots. 

 

I have the strange feeling that Harrier wants to go faster. It is a lot smaller compared before thrust fix, but still drag feels too small. Like you can't perform the "nose down bow" hover like in videos as Harrier starts acceleration forward and dives.

 

 

 

[pappachuck]

1 hour ago, TLTeo said:

I don't think that's possible given that DCS EFMs are written in C++ and encrypted.

 

Just an idea - could it be that both thrust and drag are too small, so that when flying at high speeds the errors on both kinda balance each other out and the aircraft matches the performance charts, but during VTOL you notice the lack of thrust but not the lack of drag?

It is possible, and we wont know unless we can see their Flight model.

VSTOL is extremely complex to model and I think RB missed lots of aspects by just using the USMC manuals. One of these probably is the engine power and Cd.

[lukeXIII]

On 7/6/2021 at 6:07 AM, pappachuck said:

That is incorrect, now it seems the engine has the thrust curve of the Pegasus 11-21 and no longer the Pegasus 11-61.

 

Using the NFM-400 charts; the 406 has a maximum corrected hover weight of around 19,500 lbs, compared to the 408 that has a maximum corrected hover weight of around 21,000 lbs. In game the thrust matches closely to that of the 408 curve (except for certain wet conditions).

 

In regards to the maximum thrust being incorrect, the full quote for this value is: 

 

"The F402--RR--408 series engine, with water injection, develops a nominal (static test bed) thrust of 23,400 pounds in optimum ICAO conditions or 22,200 pounds without water injection."

 

It's likely this value was the best possible thrust obtained using a perfect engine and in perfect laboratory conditions. As the charts in the NFM-400 were obtained from data directly from flight tests these are much more indicative of the actual thrust that can be produced in normal operations. Perhaps an argument could be made for simulating a non-zero datum engine compared to the current zero datum engine.

 

On 7/8/2021 at 12:09 AM, pappachuck said:

There are other aspects to the graphics that is not listed, they are assuming 95% of the total engine output as safety margin. So even if the currently model was for the engine  F402--RR--408 (Pegasus11-61) it would need to be slightly above of what the manual states to match what the aircraft would output.

 

As there are already separate "safety margins" for VL and VTO based on the calculated hover weight (95% and 97% respectively) I highly doubt that there is another safety margin factored into the charts. Do you have a source for charts being 95% of the actual thrust?

 

[pappachuck]

2 hours ago, lukeXIII said:

 

Using the NFM-400 charts; the 406 has a maximum corrected hover weight of around 19,500 lbs, compared to the 408 that has a maximum corrected hover weight of around 21,000 lbs. In game the thrust matches closely to that of the 408 curve (except for certain wet conditions).

 

In regards to the maximum thrust being incorrect, the full quote for this value is: 

 

"The F402--RR--408 series engine, with water injection, develops a nominal (static test bed) thrust of 23,400 pounds in optimum ICAO conditions or 22,200 pounds without water injection."

 

It's likely this value was the best possible thrust obtained using a perfect engine and in perfect laboratory conditions. As the charts in the NFM-400 were obtained from data directly from flight tests these are much more indicative of the actual thrust that can be produced in normal operations. Perhaps an argument could be made for simulating a non-zero datum engine compared to the current zero datum engine.

 

 

As there are already separate "safety margins" for VL and VTO based on the calculated hover weight (95% and 97% respectively) I highly doubt that there is another safety margin factored into the charts. Do you have a source for charts being 95% of the actual thrust?

 

That is the challenge, getting the Langley test results or any flight model created afterwards. I only found academic reference on those.

The FM is slightly off, its just incredibly hard to find academic information in something so old.

 

How I know it is off. Well, RCS bleed flow curves are not factored among lots of other things, I would guess they dont have a fancy model and scripted most behaviors.  

 

Below I present a series of examples of modelling aircraft, very useful for very complicated models such the harrier and vectored thrust and high maneuverable aircrafts.

 

For example:

 

 

 

[JIMJAM]

I haven't flown the Harrier in months but today pancaked a attempted hover with no ordinance and 2400 on the fuel. All I did before that was pattern work so the engine wasn't smoked. I came here just to see if it was me and here ya go.

[Ramstein]

I am not a pilot, but serviced plenty of British Harriers inthe USAF around 1980... they never took on water, and had plenty of power for landing taking off and hovering...

of course this was a long time ago, plus they were the Brit version. I cannot sya for sure but I believe they were practicing for the Falklands. My point is, I can go on and on about aircraft I both flew in and serviced and have spoken in length to pilots about capabilities and there is alot of evidence that some of the modelling in some of the aircraft is not the same as in real life. Not much one can do ecpent either buy it or don't I know/knew real pilots, combat pilots who flew aircraft from Korea on, I ppkoke topolits who wer eitneh real Flying Tigers too.. and often thes epiltos would tell about what theyse aircraft flew like, and some of the pilots would try to chat with modelers about the aircraft and features and the modelers were often open to information but still would disgregard the information and features that chose to not fix. Back in the circle of don't like don't buy it. I get po'd and annnoyed when things are wrong too, but at the end of the day we get what we get. I have asmall list of things I consider to be not correct but just don't list the stuff.. as I am just oo worn out and cannot handle along drawn out battle over things needed changed of fixed. I wil never ever be able to learn how to fly al that i have, at least be very good at each aircraft, and am stil having agood time. I don't code, Ileanred the hardware in engineering a long time ago with computers, but didn't learn to write the software. So I cannot dictate to the software writers. So, thank you for those that make all of this possible.

[Ramsay]

3 hours ago, JIMJAM said:

All I did before that was pattern work so the engine wasn't smoked. I came here just to see if it was me and here ya go.

... with no mention of airfield altitude or air temperature - how are we supposed to help you or check what the "charts" say for your weight ?

[Longiron]

Altimeter 29.78 temp 19c

Got it on deck with 900lb fuel and 200lb water.

Didn't get a hover until I was 1400lb fuel and 500 water.

Caveat here, this was all with the boat steaming 20kn.

I had 2 SA full gpod and tpod.

[Brainfreeze]

Definitely struggling with more than 40% fuel on the LHA.  Forget about having ordinance. Water goes in less than a minute if u need it.