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HeliTorque :: View topic - Priming engine on R44 raven II
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Priming engine on R44 raven II
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Rotorman
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PostPosted: Tue Mar 10, 2009 12:09 pm    Post subject: Priming engine on R44 raven II Reply with quote

Hi
When priming an R44 I am following the advise in POH. Nothing mentioned about throttle closed or open. My instructor told me, I wasn't enough with 3-5 seconds go for 7-8 seconds. Then an mecanical told me, there wouldn't be any flow, if throttle was closed. Do any body know what is right ?
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JeffHall
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PostPosted: Tue Mar 10, 2009 12:38 pm    Post subject: R44 Raven II Priming Reply with quote

I've been taught to prime with the following:
Mixture Full Rich,
Throttle Closed
Prime for 3-5 seconds AFTER the Warning Light goes out
Pull Mixture to Lean

Press Starter + Move Mixture to Rich as Engine Fires...

I have to say 3-5 secs isn't always enough, sometimes it takes a 2nd prime before it'll run.
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PostPosted: Tue Mar 10, 2009 2:08 pm    Post subject: Reply with quote

It's a bit of an art, this I think! I've been told several different things by different instructors over the years, at the same place! (I tend to follow the advice of the owner though - his business, after all!)

I don't think "throttle open" features though - that sounds like a potential "gotcha" - forget to shut it, start engine with throttle open! No thanks. Wink Particularly if it's not on the checklist...!

Once started, when we consider the throttle to be shut, the engine is still running - therefore, has to be some fuel getting in!

How much to prime, I find, depends on how recently the heli has flown/how hot the engine is. If it's just been shut down, then no prime seems to be the thing. If it's cold, then a good 5 seconds is about right.

"Move Mixture to rich as engine fires"... well, that's more or less how I was taught, but on the last LPC, the technique was refined slightly, to move mixture to rich after engine fires.
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JeffHall
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PostPosted: Tue Mar 10, 2009 7:21 pm    Post subject: Reply with quote

Quote:

"Move Mixture to rich as engine fires"... well, that's more or less how I was taught, but on the last LPC, the technique was refined slightly, to move mixture to rich after engine fires.


Thinking about it, after is probably more true than my as, at first I tended to push the mixture in before the engine had actually fired and it wouldn't run - last weekend I was back in a Raven II after about 8-10months of flying a Raven I... It fired on the 2nd prime using the after it fires approach.

The Raven I on the other hand is a piece of cake - virtually every start is a winner! I don't know why the fuel injected Lycoming is such a pain.
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PostPosted: Tue Mar 10, 2009 9:09 pm    Post subject: Reply with quote

You would think EFI would be much better at starting than Carbd. In any other vehicle fuel injected engines start far far better than a carbd engine.
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PostPosted: Tue Mar 10, 2009 9:16 pm    Post subject: Reply with quote

WindSwept wrote:
You would think EFI would be much better at starting than Carbd. In any other vehicle fuel injected engines start far far better than a carbd engine.


We were having a similar (albeit very brief) discussion about fuel gauges at the weekend and if you look at a modern car and its engine systems you realise that light aircraft engines are still pretty much in the dark ages.

W.
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Rotorman
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PostPosted: Wed Mar 11, 2009 9:05 am    Post subject: Reply with quote

When looking at some of the reply, I see you have same problem as I hat.
Flowing the POH but with open throttle under priming, it is my expirence will improve start up.
Ofcource you have to close throttle before starting.
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PostPosted: Wed Mar 11, 2009 3:26 pm    Post subject: Reply with quote

PilotWolf wrote:
WindSwept wrote:
You would think EFI would be much better at starting than Carbd. In any other vehicle fuel injected engines start far far better than a carbd engine.


We were having a similar (albeit very brief) discussion about fuel gauges at the weekend and if you look at a modern car and its engine systems you realise that light aircraft engines are still pretty much in the dark ages.

W.


Unfortunatly it does seem this way.

The only thing i can think of is cost. Its probably cheaper to adapt old engines then to fit new ones and go through the whole testing process' all over again.
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PostPosted: Wed Sep 30, 2009 5:51 pm    Post subject: Reply with quote

Just my tuppence worth....

A gotcha on the Raven II is for people to release the starter button before the engine catches, realise it's not caught and then press the starter button again straight away.

This dis-engages the starter motor and then re-engages the motor into the main ring gear whilst it is still turning. A great way to rip teeth off the ring gear and wear down the starter motor at the same time. Very labour expensive to repair.
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PostPosted: Wed Sep 30, 2009 11:57 pm    Post subject: Reply with quote

WindSwept wrote:
You would think EFI would be much better at starting than Carbd. In any other vehicle fuel injected engines start far far better than a carbd engine.


Autos, and most other surface vehicles don't have mixture controls. For fuel injected aircraft engines, the start sequence is based on the assumption of an over-rich prime which will lean out as the starter turns the engine until a combustible air/fuel mix is obtained. Thus, most fuel injected aircraft engines specify a start with a closed throttle.

This is common design practice except for hot starts, which are a whole different story. Heat aids fuel vapourizaton, and so less prime, and sometimes a little additional air, is necessary.
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PostPosted: Thu Oct 01, 2009 8:26 am    Post subject: Reply with quote

PilotWolf wrote:
WindSwept wrote:
You would think EFI would be much better at starting than Carbd. In any other vehicle fuel injected engines start far far better than a carbd engine.


We were having a similar (albeit very brief) discussion about fuel gauges at the weekend and if you look at a modern car and its engine systems you realise that light aircraft engines are still pretty much in the dark ages.

W.


I have to say that engine wise I would rather be in the dark ages rather than having some very falable engine management system shutting down for some non critical issue such as a sensor not having a good day. I am happy to stick with the warning light and a pilot making the time to land quickly desicion. The more complex you make it the more there is to go wrong. What was the line in Armagedon " Russian made, American made all componants same , made in Taiwan " or something like that.
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