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View Full Version : Who knows about: turbo prop engine start procedures



bstikkel
10-29-2010, 11:46 AM
Hello fellow builders,
I try to create a semi realistic engine start procedure in my home-cockpit.
This cockpit reflects a bushplane in general.

FSX Tutorials tell a enough abou starting a piston engine, but actually nothing about how to start a turbine prop engine.

Can somebody provide me some clear info about this?

Thanks.

ANDYSMITH
10-29-2010, 12:44 PM
Hello!

1. set a button to (starter1_set)in FSUIPC
2. set a control to (mixture1) this is the same as the "condition" or "fuel" lever in the turbine. you can also use two buttons if you wish, set one to (mixture lean) and the other to (mixture rich)

To start
1. mixture or condition lever in the lean position, full aft.
2. throttle or power lever to idle, full aft.
3. engage starter and watch the RPM until it reaches 10 or 15%
4. mixture or condition lever to RICH or RUN , full forward if using a lever.
Engine should come to life and then you can turn off the starter

To shutdown just pull the condition lever to the aft or" fuel off"position and that is it.

bstikkel
10-29-2010, 05:49 PM
Hi Andy,

Thanks for your explanation.

I heard a real turbo prop start last year and later talked about it with the pilot.
He first starts the turbine and later connects the propellor so it starts rotating.
Do you know if these two things can be handled separately in FSX ?

I actually do not know whether the 'connecting' prop phase is started manually or whether it follows automatically after the turbine has started up properly.

Do you - or anybody else - happen to know something about this?

Greetings,
Bram

Ronson2k9
10-29-2010, 06:29 PM
There is no disconnect between prop and aircraft in FSX. There is only feathering and that's only on aircraft that have that as a feature (built into the model via the builder). I would add prop to neutral if feathering is possible during startup. That would reduce the thrust (work load) during startup on the engine. Turbines are different from normally aspirated as they work best when hot. So they need to warm up before load is applied.

There is the 'simulated' connect during startup as often the prop won't begin rotating till RPM reaches a certain level. This is built into the model though and not controllable any more then RPM is controllable during startup.

So in many ways the startup of the Turbine is based on the model of the aircraft. By that I mean what the model maker included in his/her model. You could do a few things though if the startup procedure is something you want to go by the book.. One is to get the book. The POH of the aircraft or FCOM (Flight Crew Operations Manual) will describe 'your aircrafts' startup procedure. The next is contact the builder of the FSX aircraft and or check for a checklist in the builders aircraft. Some builders go to great pains to simulate every aspect of the operation and often that is quite important.

Hope that helps.
Ron

bstikkel
10-29-2010, 07:02 PM
Hello Ron,
Thank you for your clear explaination.
Great, the way various people point at various aspects of one question.
The advantage of a forum, I suppose.
Thanks again, both replyers !

I must be able to come where I want to with all your info info.

Greetings,
Bram 8)

davek
10-29-2010, 07:44 PM
The prop seems to be delayed in turning due to the ratio of the gear box. In the 412 I fly in, the turbine spins at 20,000 rpm but the rotor spins at 400rpm. Therefore the turbine can spool up to about 10% before the rotor starts to turn.
So the rotor/prop is contected to the turbine by a gearbox with a huge reduction so that the prop/rotor is spinning at the operational rpm
There are several references out there in cyber land that state you can hold onto to a prop while the turbine is spooling up, not the sort of thing that I would do.

Good reference reading > http://en.wikipedia.org/wiki/Turboprop

Another easy to read page > http://www.helicopterpage.com/html/jet.html

wledzian
10-29-2010, 08:46 PM
It's not the gear ratio.

On many turboshaft engines, the output shaft has its own turbine, which is not connected to the compressor shaft and primary turbine. During startup, the primary turbine absorbs most of the power to spool up the main shaft, not leaving much left over for the output shaft.

Once the engine spools up to a point where there is enough leftover energy at the output turbine, the output shaft may begin to turn. At this point, though, the turbine blades may be stalled. In this condition, they don't efficiently extract energy from the exhaust gas, and produce little torque. For these engines, you can hold the prop while the engine is starting. (if you plan to try, please let the guys at Darwin Awards know beforehand)

Once the prop starts spinning and the turbine becomes unstalled, power extraction becomes much more efficient, torque rises rapidly, and output RPM increases accordingly.

Ronson2k9
10-29-2010, 08:48 PM
Hold on to the prop??? WOW.. Can we say amputee.. There are about a thousand things that could happen if something that is supposed to happen doesn't go as planned. All of them bad.. Nope I'm not holding onto anything on the outside attached to anything on the inside that is moving.

ANDYSMITH
10-29-2010, 10:50 PM
Hold on to the prop??? WOW.. Can we say amputee.. There are about a thousand things that could happen if something that is supposed to happen doesn't go as planned. All of them bad.. Nope I'm not holding onto anything on the outside attached to anything on the inside that is moving.

I understand that you really don't even need to hold on very tight, but DO NOT LET GO!!!

Andy

bstikkel
10-30-2010, 06:39 AM
Dave, thanks for these indeed very informative pages. :cool:
Greetings,
Bram