DC9-30. I need help with engine datas

[mosquito3]

Hallo everyone

This is my first post here. My name is Francesco and i'm from Rome, Italy.

I take the occasion to present my project and to ask how to solve some problem with it. I don't know if this is the right place to ask something like this (i'm sorry if it's not) but i hope there will be someone able to help me.

I've been workin on a DC9 since 2009 but being alone the project advances very slowly.

I have some problem regarding the the engines (JT8D-9) paramenters. I have a table chart reporting a lots of data (EPR, N1, N2, ecc.) at different thrust settings at sea level. The problem is that if i set every data (in plane maker) to be as the chart says at, for exaple, 14500 lbs thrust i will get wrong datas at 9000 lbs of thrust. I believe i reached a good compromise but i can't get the engines working like in real life.

I would like to know if someone has managed to obtain an engine that works in x-plane the same way as it works in real life, with same parameters and thrust at different settings (maybe a plugin?).

I add some screenshots of the DC9 i'm workin on

http://img10.imageshack.us/f/screenshot1sh.png

http://img194.imageshack.us/img194/1803/screenshot2ju.png

http://img153.imageshack.us/f/screenshot3ev.png

http://img163.imageshack.us/f/screenshot4g.png

http://img718.imageshack.us/f/screenshot5qm.png

http://img37.imageshack.us/f/screenshot6ry.png

http://img23.imageshack.us/f/screenshot7tl.png

http://img825.imageshack.us/f/screenshot8j.png

I hope my english has been at least understandable

Thanks in advance

Francesco

[Kesomir]

Looks very nice 

[Tonka]

TurboJet setups and X-Plane do not go well together.

If your thrust shown in the sim is less than you have set in planemaker, you probably have one of the FADEC options checked.

The main problem with turbojets in the sim is the lack of thrust at higher altitudes. The thrust decay as you climb is too excessive.

The only way to get around this is with a plugin, or maybe a Gizmo script.

[namaui]

I remember reading about how vohinx had similar problems with his Lear Jet 23. Most numbers worked, but he was getting an incorrect EGT. I think if you play with the numbers in Plane-Maker enough, you'll get somewhat realistic performance, just not accurate feedback (EPR, EGT, etc).

[mosquito3]

Thanks guys

There is nothing checked in the fadec section of plane maker and i reached a good compromise between thrust, EPR, N1, ecc. But istill have some problems. For example i get 15000 lbs of thrust at 94.4 of N1 as written in the charts i have, but if i set 85.1 i do not get 11400 lbs but something less.

And, as tonka said, i loose a lot of thrust during climb too....that's frustrating.

I believe i should learn how to create a plugin

[Kieran]

Yes plugin is the only way to fix this. (As far as I know) Gizmo looks pretty simple and should do the job, look in the Gizmo section of these forums.

[Morten XPFW]

X-Planes jet engine model will not fit very well on many aircraft.

In general, it gives too little thrust at low N1's.  Also it has some

problems with ram pressure recovery at different altitudes/speeds.

As you appear to have noticed, the thrust you should set in planemaker

is NOT the published thrust you find on the engine.  The published

thrust of an engine is usually gaven as MAX TO THRUST at ISA (sealevel, 15C etc)

So you need to look into you charts and see at what N1 this is at.

The value you enter in XP is at 100 % N1, so it is always higher or lower than published thrust.

As for fixing the low end N1, the simple solution is manipulating the N1 instrument to show

a lower N1 number.  (shifting the thrust/N1 curve) This can be done easy with a generic instrument.

If you want extreme accuracy in the entire flight envelope, you need to code a plugin.

M

[mosquito3]

Thanks for the exhaustive reply Morten

The data written on the chart refer to sea level, IAS condition.  Infact i had to set 17,450 lbs of thrust at 100% N1 to get 14,500 LBS at 94,4% N1 for the Takeoff as reported in the charts.

Manipulating the N1 instruments would be an interesting walkaround but i believe i finally will learn how to code a plugin

Thanks again.

Best regards

[ptru]

Hi Francesco,

if you're interested I could try to make a plugin for you.

Contact me on e-mail.

Regards,

Premek