To prime or not to prime

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Tim H
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Re: To prime or not to prime

Post by Tim H »

I REALLY struggled starting my DA40 when I first got it. Finally settled on these procedures which work 95% of the time for me:

Cold Start:
WOT
Fuel Pump ON
Mixture Full Rich and back to Full Lean on a count of 5
Throttle - 1/4" open
Engage starter and move slowly move mixture to Full Rich
Fuel Pump OFF
Throttle as req'd and lean for taxi

Warm Start:
Fuel Pump ON
Throttle - 1/4" open
Engage starter and move slowly move mixture to Full Rich
Fuel Pump OFF
Throttle as req'd and lean for taxi

I often wondered if every DA40 starts the same and I'm gathering from these posts that each one is unique.
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Rich
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Re: To prime or not to prime

Post by Rich »

Tim H wrote: Thu Jan 27, 2022 5:58 pm I often wondered if every DA40 starts the same and I'm gathering from these posts that each one is unique.
They're probably more similar than we think. I do generally use the same priming procedure all the time in cold starts, but notice that it takes a bit more cranking in colder weather than not-so-cold. We're talking like one blade vs. 2-3 seconds, so no big deal. I figure vapor pressure is a player here.

The DA40 mechanical fuel injection system, though primitive by modern automotive standards, does have a certain amount of built-in reaction to conditions. It will reduce fuel flow in reaction to increasing altitude and react to throttle position. If the DA40 throttle is pulled back to idle (when priming or otherwise), fuel flow is considerably restricted. This is a factor to consider in priming and is not necessarily a bad thing.
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Diamond_Dan
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Re: To prime or not to prime

Post by Diamond_Dan »

Tim H wrote: Thu Jan 27, 2022 5:58 pm
Cold Start:
WOT
Fuel Pump ON
Mixture Full Rich and back to Full Lean on a count of 5
Throttle - 1/4" open
Engage starter and move slowly move mixture to Full Rich
Fuel Pump OFF
Throttle as req'd and lean for taxi
I used to do something like this but I got a lot of blue juice out the overflow. I backed off and do the following:

Cold Start:
Throttle 1"
Fuel Pump ON
Mixture full rich and back to full lean on a count of 3 (4 in winter)
Fuel Pump OFF, wait a few seconds for the fuel to vaporize
Throttle 1/4" open
Engage starter and move slowly move mixture to Full Rich

Hot Start (within one hour of operation):
Crack the throttle
Engage starter and slowly move mixture to Full Rich (requires a bit of magic hands and voodoo)
At the one hour mark I start with one second of fuel and go up from there depending on season and engine temp.
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dant
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Re: To prime or not to prime

Post by dant »

Various DA40s I've flown have had different manifold pressures at different throttle positions, which would affect where you'd want the throttle to be for starting. That may explain the differences as well.
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Donkadillapig
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Re: To prime or not to prime

Post by Donkadillapig »

I write this not to be snarky at all but to share with you at least a newbie pilot and plane owners logic. With the sincere aim of sharing our different points of views and outlook on aviation;
This is EXACTLY the reason I bought an Austro equipped NG. It didn't really matter to me whether it was a Cessna 172 or a DA40 DiamondStar, as a rookie pilot under training I was simultaneously intimidated, confused and appalled at these kinds of "procedures" (I'd prefer to write shenanigans).
In my fledging pilot brain this kind of stuff belonged in a WW2 fighter pilot movie!

I don't want to have to manage an engine, all power to those that do and love it. What I really wanted was to get from A to B quickly, efficiently and in a certain style. That's the truth of it. In the same vain, I will never fly aerobatics, I'm not that excited about vintage planes, tail draggers, off strip landings etc etc. I just wanted to skip the lines, metaphorically flip the bird to the TSA and be on my way lol

I know companies like Lifestyle make much of their future vision of GA and personal flying. To many it may just sound like marketing slogans and jargon. To me however, it was and still is exactly my goal for flying. I rather suspect I might not be alone, certainly among newbie owners.
All that to say, chapeau to you chaps that keep these engines and airplanes running. But I'm going to flip the master switch, wait a couple of seconds for the glow plugs and turn the key ;)
More to the point perhaps, any plane I own or rent in the future is going to need to do the same.

No snark, just sharing a view, with respect to all.
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Lou
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Re: To prime or not to prime

Post by Lou »

Fair enough, but not for me - engine witchcraft is part of the fun.

When I was a boy car engines flooded all the time in cold weather. There was a certain pride in learning how to deal with it. You removed the air cleaner, and stuck a Bic pen in the carburetor to wedge the choke open. Then you cranked. Sometimes the excess fuel would explode back out of the carb and the pen would be toast.

There is something strangely satisfying about low tech mechanics. The NG is a beautiful machine to be sure, but I worry that at some point tech will suck all the fun out of life. :)
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dant
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Re: To prime or not to prime

Post by dant »

I don't want to have to manage an engine, all power to those that do and love it. What I really wanted was to get from A to B quickly, efficiently and in a certain style. That's the truth of it. In the same vain, I will never fly aerobatics, I'm not that excited about vintage planes, tail draggers, off strip landings etc etc.
^ This is me, except I really enjoy the in-air time in between the points. I do also really enjoy the knowledgecraft around aviation, but there's plenty to go around without it being in the engine.

So far I haven't yet been able to really get my family involved in my flying, but if that happens in the next few years I suspect I'll be in a FADEC engine eventually. In the meantime I can't really rationalize the current premium for an NG.
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Re: To prime or not to prime

Post by CFIDave »

After owning a Lycoming DA40 for 4 years I got really good at hot starts, cold starts, leaning, managing cylinder temps, optimizing RPM for high altitudes, etc. -- I took a certain pride in developing that knowledge. :)

But to this thread's question, when starting a hot (heat-soaked) Lycoming DA40, here's what always worked for me:

1. Prime for only 1 second with fully open throttle and red mixture set to full rich.

2. Then before engine start, set throttle to half-way open, and bring the red mixture back to idle cut-off.

3. Start cranking the engine with "3 hands:"
- one hand to turn the key to start position,
- a 2nd hand to smoothly move the red mixture knob forward from idle cut-off to full rich, and
- a "3rd hand" to quickly move the throttle from 1/2 open back to idle as the engine roared to life.
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smoss
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Re: To prime or not to prime

Post by smoss »

Dave, to clarify, are you smoothly advancing the mixture before it catches, or waiting for it to start to fire, then smoothly advancing? It sounds like you just advance it before it fires, then somewhere in the middle it fires up. What happens when you get to full rich and it hasn't fired?
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Re: To prime or not to prime

Post by CFIDave »

smoss wrote: Sat Jan 29, 2022 3:11 pm Dave, to clarify, are you smoothly advancing the mixture before it catches, or waiting for it to start to fire, then smoothly advancing? It sounds like you just advance it before it fires, then somewhere in the middle it fires up. What happens when you get to full rich and it hasn't fired?
I'm advancing the mixture while cranking, and usually part-way to full rich the engine starts firing. I don't recall it getting to full rich and not firing, but that might have happened occasionally -- in which case I just kept cranking with the starter for another second or two and the engine fired while full rich.
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