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PostPosted: Sun Oct 01, 2017 1:44 am 
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Airman

Joined: Fri Sep 29, 2017 5:16 am
Posts: 13
Maybe I can call on them for help!!

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John Earl


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PostPosted: Sun Oct 01, 2017 4:47 am 
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A2A Mechanic
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Joined: Sun May 26, 2013 5:03 am
Posts: 4023
Great you've got this sorted out! Indeed, it often is worthwhile to double check what one's doing, and to look behind the lists to understand what is actually going on. To further explain the meaning of each step, assuming that we begin from a ready to start state (tanks on both, fuel cutoff open and all checks done etc):

    • Ensure that the mixture is at cutoff. This is to make sure that no fuel is introduced into the engine before we are ready do so. This is important.

    • Fuel pump on, let it run for a few seconds, or longer if the engine has been sitting for some time while still hot (I don't think it matters in the simulator). This makes sure that the fuel is pushed through the lines and pressurized up to the fuel injector unit.

    • Fully open the mixture. This allows for the fuel to flow further through the injector lines and into the intake ports. Watch out for the fuel flow needle movement: effectively this is a pressure indicator measuring the flow resistance caused by the injectors which should be fairly well calibrated. Therefore a rise in fuel flow indicates that the fuel is reaching the engine. It should only take a few seconds.

    Immediately after a steady flow is indicated (it is often easier to just count a few seconds - if it is cold, you might want to prime for a few more seconds), pull the mixture out to cutoff. This stops the fuel flow into the engine.

    • Then turn off the fuel pump, it is not necessary anymore, and should be left off to prevent unwanted enriching of the mixture.

    • Make sure the throttle is cracked. This is to allow good amount of air to flow through the induction system, mixing with the fuel you just introduced to the intake port areas.

    • Engage the starter, and keep the engine turning for several seconds. It should catch up within few seconds as the air flow sucks in some fuel with it. If it doesn't, and you suspect the engine was flooded, open the throttle some more while you keep on cranking. This allows more air into the engine, leaning the "mixture".

    Immediately when the engine catches, smoothly push the mixture in and adjust the throttle to keep the idle RPM.

    • Eventually, if the engine doesn't catch, the prime fuel is depleted, and you need to start over. Often a good mixture is reached at some point during cranking, at least in one cylinder, leading into the engine that attempts to start.

This same method applies to just about all fuel-injected Lycomings, but not to Continentals nor to the carbureted engines.

-Esa


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PostPosted: Sun Oct 01, 2017 5:13 am 
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Airman

Joined: Fri Sep 29, 2017 5:16 am
Posts: 13
Thank you. Very comprehensive.

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John Earl


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PostPosted: Sun Oct 01, 2017 1:26 pm 
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A2A Mechanic
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Joined: Sun May 26, 2013 5:03 am
Posts: 4023
If you run into these IO-things in real life, you surely want to pay attention to the fuel flow gauge when priming. In some engines, it may twitch around some before giving a steady indication; the steady indication essentially telling you to cut off - now!.

The twitches occur mainly with a hot engine, having stood for a little while, as the bubbles of fuel vapor dancing in the lines get into individual injector lines. Often running the pump with mixture at cut-off before actually priming helps with these.

These later Cessnas do have a transducer in between, folks say that the effect is harder to tell.

Oh, btw: if the fuel-injected engine you run into happens to be a one manufactured by Continental, then it works entirely the different. :)

-Esa


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PostPosted: Tue Jan 15, 2019 5:07 pm 
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Airman Basic

Joined: Tue Jan 15, 2019 4:58 pm
Posts: 1
I would assume you guys have flown actual Cessna 172 aircraft before, but my question would be... What level of airworthiness were these planes to warrant a simulation that is so difficult to start. I am a pilot and have flown 4 different C172 planes so far. The aircraft almost starts itself. The notion that it is so finicky regarding mixture, throttle, fuel priming, et cetera, is kind of not true at all. You don't have to use the pump, you don't have to prime, you certainly don't drain an entire battery in a 15 second crank. When I start a C172, I pump the throttle once, go full mix, crack throttle one RCH, and then crank for 2 seconds, and it starts at an RPM of 1000. I back it off to about 800/900 for idle. The longest I've ever cranked was 5-6 seconds, cold. I'm just saying, I'd get a better A/P if you think a C172 is this difficult to start. Otherwise, I think the aircraft you're selling is a work of art, and my compliments to the chef. It got me my license much faster due to the fact that I was running VR practice between IRL flight lessons.


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PostPosted: Wed Jan 16, 2019 8:24 pm 
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Chief Master Sergeant
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Joined: Mon Sep 02, 2013 7:30 pm
Posts: 3533
Location: Typically hanging around N07, 12N, KLDJ, KCDW
I find that the A2A 172 is quite faithful to the real machine. The real machine is sensitive to prime, temperature of the engine and atmosphere.

If you do it correctly, the engine will fire right up north in the sim and IRL. Mess things up and you may find yourself cranking away with poor results. It is interesting to watch the local flight school students crank away struggling to stay their aircraft, while the next guy gets am immediate start within a couple of blades.

I wouldn't change a thing about the simulation as it would be less realistic.

I would ask what conditions you fly in? Are your local temps around -3C as they are now for me? How about in the summer where our temps sometimes rise to 37C? Try a hot start in that climate!

A few Bonanza owner strongly prefers to keep his engine running when dropping off a passenger because it is extremely difficult to hot start even in cool climate!

_________________
Flight Simmer since 1983. Private Pilot
Paramus Flying Club http://www.flyingclub.org


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PostPosted: Thu Jan 17, 2019 9:22 am 
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Staff Sergeant

Joined: Mon Dec 31, 2012 1:38 am
Posts: 476
Location: Bonham, Texas
I never had any problems starting the Cessna once I figured out I was over-priming it. Now it starts easily every time unless I under-prime too much and it has always started on the second try after a bit more priming.

I don't get concerned if a particular aircraft doesn't act exactly the way I expect. All aircraft have a slightly different personality and I just consider it part of that aircraft's personality.

At least with A2A planes. They do things right. Other developers' aircraft, I get my hands dirty in the code until I'm happy with it.

Hook


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