Flight model no longer corresponds to the Pegasus 11-61 power curve

[pappachuck]

The engine should have a maximum dry-thrust of 20,500 lbf at least varies with temperature and altitude. It is not being currently modeled properly. The current power curve is more like a Pegasus 11-51.

PERFORMANCE

• Maximum thrust: 23,800 lbf (106 kN)
• Overall pressure ratio: 16.3:1
• Specific fuel consumption: 0.76 lb/lbf-hr
• Thrust-to-weight ratio: 6:1

• Pegasus: the Heart of the Harrier, Andrew Dow, Pen & Sword, ISBN 978-1-84884-042-3
• Not Much of an Engineer, Sir Stanley Hooker, Airlife Publishing, ISBN 0-906393-35-3
• Powerplant: Water Injection System, Aircraft Engineering and Aerospace Technology, Vol. 42 Iss: 1, pp: 31 - 32. DOI: 10.1108/eb034594 (Permanent URL). Publisher: MCB UP Ltd

Citations

[Wisky]

if you look at the NFM-400 and read the graphs correctly you will realize its actually spot on.

there has been a few threads on this topic, do your homework and use the forum search function.

 

it has been tested a lot by various users and after understanding how to actually read the graphs they all accept that the current engine model is near perfect to the real deal

[pappachuck]

On 7/4/2021 at 6:48 AM, Wisky said:

if you look at the NFM-400 and read the graphs correctly you will realize its actually spot on.

there has been a few threads on this topic, do your homework and use the forum search function.

 

it has been tested a lot by various users and after understanding how to actually read the graphs they all accept that the current engine model is near perfect to the real deal

The NFM-400 states that the Pegasus 11-61 produces 22,200 pounds without water injection. Exactly my point. The engine they modelled it is the Pegasus 11-21. 

I searched a lot as matter of fact.

[Bog9y]

3 hours ago, pappachuck said:

The NFM-400 states that the Pegasus 11-61 produces 22,200 pounds without water injection. Exactly my point. The engine they modelled it is the Pegasus 11-21. 

I searched a lot as matter of fact.

That's interesting. The best way to go about this is raise a formal bug in the bugs section and provide all the test data with the charts you've used to prove that yours is correct and theirs is wrong. 

[Blackeye]

On 7/4/2021 at 9:15 AM, pappachuck said:

The engine should have a maximum dry-thrust of 20,500 lbf at least varies with temperature and altitude. It is not being currently modeled properly. The current power curve is more like a Pegasus 11-51.

 

And what lead you to the conclusion that it is not modeled correctly?

The maximum wet VTO weight is listed as ~20400 for the -408 engine and from what I tested you can takeoff at that weight.

 

Edited July 13, 2021 by Blackeye

[pappachuck]

On 7/13/2021 at 5:05 PM, Blackeye said:

 

And what lead you to the conclusion that it is not modeled correctly?

The maximum wet VTO weight is listed as ~20400 for the -408 engine and from what I tested you can takeoff at that weight.

 

 

Evolving into the topic, the state space model of the flight model does not correspond to the in-game model by a slight deviance that is above 10%.

I need time to build the MATLAB model and put side by side with DCS. RB would help if they let us have their FM for mathematical comparison.

 

NASA did all the testing and they have good resources about this topic.

https://ntrs.nasa.gov/api/citations/19900012460/downloads/19900012460.pdf

[Blackeye]

6 hours ago, pappachuck said:

I need time to build the MATLAB model and put side by side with DCS.

 

So you haven't done any modeling and/or comparison to DCS? I'm genuinely curious what makes you say the model is off then.

 

I mean if you want people to verify your findings and change the model in DCS you'd need to provide more than just "it's off" - a format that is often used is

1) The data you based your conclusions on (beware of the posting rules)

2) How you'd expect the aircraft to behave in DCS based on that data

3) How the aircraft actually behaves in DCS, i.e. what is wrong

4) (Optional) Suggestions why this might be the case or what to change

Edited July 15, 2021 by Blackeye

[pappachuck]

On 7/15/2021 at 12:46 AM, Blackeye said:

 

So you haven't done any modeling and/or comparison to DCS? I'm genuinely curious what makes you say the model is off then.

 

I mean if you want people to verify your findings and change the model in DCS you'd need to provide more than just "it's off" - a format that is often used is

1) The data you based your conclusions on (beware of the posting rules)

2) How you'd expect the aircraft to behave in DCS based on that data

3) How the aircraft actually behaves in DCS, i.e. what is wrong

4) (Optional) Suggestions why this might be the case or what to change

 

Its relatively easy to get the mathematical model of the aircraft, its purely academic research.

What is hard is getting data from the game to build a comparative model. 

 

So far the best I can say is that its off by a little, thus the current Flight model does not represent an accurate version of the real thing. Maybe one day I can extract data from the game and build a comparative model and determine by how much and where.

 

RB have their Flight model and could easily compare to the Data from NASA VSRA program. I would if I had a way to get data out of the game, that would be a good practice for academic purposes.

 

Obs.: Flight model include the flight controls which on the Harrier case are software, response times on reaction control, thrust curve response time, and many other stuff that is not even debated on the manuals given to the military.

[Blackeye]

3 hours ago, pappachuck said:

So far the best I can say is that its off by a little, thus the current Flight model does not represent an accurate version of the real thing.

 

You can say anything you want but I'm afraid most people will want at least some reproducible evidence before considering your statements about FM deficiencies credible or even taking any form of action.

 

[TLTeo]

6 hours ago, pappachuck said:

Its relatively easy to get the mathematical model of the aircraft, its purely academic research.

And that is why coding FMs in DCS is so easy and takes so little effort /s

[pappachuck]

On 7/17/2021 at 5:02 PM, TLTeo said:

And that is why coding FMs in DCS is so easy and takes so little effort /s

Actually the way DCS FM is made is the hard way since it does not use standarized engineering methods and processes.

[G.J.S]

On 7/17/2021 at 4:36 PM, pappachuck said:

Its relatively easy to get the mathematical model of the aircraft, its purely academic research.

What is hard is getting data from the game to build a comparative model. 

 

So far the best I can say is that its off by a little, thus the current Flight model does not represent an accurate version of the real thing. Maybe one day I can extract data from the game and build a comparative model and determine by how much and where.

 

RB have their Flight model and could easily compare to the Data from NASA VSRA program. I would if I had a way to get data out of the game, that would be a good practice for academic purposes.

 

Obs.: Flight model include the flight controls which on the Harrier case are software, response times on reaction control, thrust curve response time, and many other stuff that is not even debated on the manuals given to the military.

Isnt the NASA paper you cite a “human factors integration” paper that relies on hypothetical pilot models using modified simulated versions of the aircraft (AV-8B & UH-60 in this case) to evaluate control laws?