Bell 412

[IAHM-COL]

that sounds real revolutionary. It'd be great if you share some details on that java-nasal parser!

[valery]

I'm really sorry, you're going to be disapointed: I do the translation nasal<=>Java by myself, with my brain CPU ! Be sure it's really simple and do not require a lot of skills, like I said it's all about class and members, not difficulty at all.

[IAHM-COL]

ok.
Not disappointment.
On the contrary -- truly impressed.

[valery]

do you know somebody there who could help me on a twin turbine engine behaviour ? Some data I got here and around are sometimes very weird and difficult to understand. You have 2 engine shafts, each of them producing some power. But one engine alone could sometimes produce more power than it theorically can with its twin part. The two shafts are connected to one gearbox running at a lower speed, then this gearbox is connected to a transmission box that run at the rotor rpm speed (more lower). When one engine is inoperative, the other produce more power. But the difference btw the 2 power values is very weird ...

[IAHM-COL]

sounds like a challenge for Simon "bomber" Marley (?)

[SHM]

Definitely a task for bomber.

[valery]

https://sourceforge.net/p/bell-412/code/HEAD/tree/Docs/412EPI_ProductSpec201302-Web.pdf
https://sourceforge.net/p/bell-412/code/HEAD/tree/Docs/Engine_PT6T-EASA_TCDS_IM.E.059_20153010_1.0.pdf

The engine is the PT6T-3D
The design is:
(Engine0(39300rpm, 597kW] + Engine1[39300rpm, 597kW]) ==> GearBox[6600rpm, 1194kW] => XMSN[324rpm] => Rotor

In OEI mode (one eng. inop.), the Gearbox can produce 764kW, I don't know how, because the max continuous power for one engine alone is 597kW. So, there are some data I don't read correctly.

[EDIT]: yes, some data are coming from the Bell412-EPI (it use a different PT6T), but it will be ok for my needs. The pb. is still the same I think.

[valery]

I think this https://www.nashvillecfi.com/multi/performance.html shed a small light on the trouble I encounter. But I have still some questions about this.
Meanwhile, the v0.2 of the PT6T processing sketch is almost done. ITT (interturbine temperature) has to have a thermodynamic (or some latency) behaviour that it's not the case. The OEI mode is functionnal but not Ok. I'm starting to translate to nasal now, and will try it with the Yasim rotorgear engine. Still funny !
CU..
https://www.youtube.com/watch?v=D0A0XUR1W1I&t=50s



[EDIT]
Processing-1.5 sketch (I'm not sure that the ControlP5 library is Ok with other Processing version, it's better to use the sketch with the v1.5):
https://sourceforge.net/p/bell-412/code/HEAD/tree/Tools/

[bomber]

My initial thoughts on this were limitations on transmission of power through the gearbox or rotor shaft torque... but having done some reading it's very simple...

You're simply flogging the bollocks off the engine to keep the crew and passengers alive..... until you can find a place to land. Be it 30secs, 2mins, 2.5mins or 30mins or any other time that the engine manufacture is prepared to rate the engine at.

One Engine Inoperable comes at a cost of forced inspection and maintenance.

There's many military examples of where the engine is sacrificed to save the crew.... and infact the Merlin Vulture engine got a bad reputation on the Avro Manchester during WWII simply because pilots would say screw the engines, let's thrash the bollocks off em and get home rather than stay and dance with a couple of 109's. WEP or War Engine Power for it's full title wasn't used in British planes at the beginning of the war simply because of this tendency, later on with air superiority it reappeared, with say a 5 minute rating to be used when needed to get out of Dodge in a hurry.... Some terms you'll hear for its use is to push the throttle through the gate, which is stop point but doesn't prevent you from pushing the throttle further if needed... I expect that this is the case.

Remember every engine is capable of producing far more power than it's rated at, even your car engine, the 6000rpm is a manufacturers stop, but could probably do 170000RPM.... or wreck itself getting there.

Simon

[valery]

All right, very clear, I keep in mind if someone want to flog my bollocks off, even less than 30secs, it could be better to go away (with my bollocks too) ! o0o ....

Thanks Bomber,

Val.