Question regarding Cessna 172 start up

[737Andi 6]

Hi,

I have a question regarding the A2A Cessna 172 start up procedure.I always fail to start the engine during my first attempt. What am I doing wrong?
I set the fuel tank selector to both. I push the fuel cut off in. Then I set the throttle to 25% in. I push the mixture to 100% in and switch the fuel pump to on. After 4-6 seconds I pull the mixture to 0% and switch the fuel pump off. Then I switch the Magneto to start. The propeller starts to swing but immediately stops.

If I repeat these steps a second time it works?!

Thanks!

Best regards Andreas

[SAS443 1,703]

cold sonditions? Are you using the primer if equipped?
On some PA28  (not a 172 though) I am familiar with you need around 5 pumps of primer for cold engine start.

[Bobsk8 12,489]

No primer in a fuel injected engine. 

[medx421 50]

3 hours ago, 737Andi said:

After 4-6 seconds I pull the mixture to 0% and switch the fuel pump off. Then I switch the Magneto to start. The propeller starts to swing but immediately stops.

Why are you leaning out the mixture? 

1.  Fuel selector "both"/Fuel cutoff in

2.  Mixture full rich

3.  Battery/Alternator on

4.  Fuel pump on for 10-15 seconds, then off

5.  Throttle in 1/4 or 25%

6.  Turn magnetos to start

7.  If needed, give a few pumps of throttle during the crank

If it does not start after 10-15 seconds, shut down magnetos and battery/alternator and wait a few seconds.  Try again.  Cessna's don't always start on the first crank.

8.  After start, throttle up to 1200rpm, lean mixture for the taxi.

[C2615 319]

I always find myself flood the engine with more than 3 sec. prime, Then just go to the flood procedure by throttle all the way up and hold start until it come.

Don't know if it will hunt the engine....

[marc1184 42]

I agree with @medx421. Should have full mixture.

 

[Bobsk8 12,489]

I have this very bizarre habit when I fly an aircraft either in real life or in a sim, of reading the manual. This is what is says for the A2A 172

 

STARTING ENGINE (WITH BATTERY) 1. Throttle — OPEN 1/4 INCH 2. Mixture — IDLE CUTOFF 3. Propeller Area — CLEAR 4. Master Switch — ON 5. Flashing Beacon — ON NOTE: If engine is warm, omit priming procedure of steps 6, 7, and 8 below. 6. Auxiliary Fuel Pump Switch — ON 7. Mixture — SET to FULL RICH (full forward) until stable fuel flow is indicated (usually 3 to 5 seconds), then set to IDLE CUTOFF (full aft) position. 8. Auxiliary Fuel Pump — OFF 9. Ignition Switch — START (release when engine starts) 10. Mixture — ADVANCE smoothly to RICH when engine starts. NOTE: If engine floods (engine has been primed too much), turn off auxiliary fuel pump, set mixture to idle cutoff, open throttle 1/2 to full, and motor (crank) engine. When engine starts, set mixture to full rich and close throttle promptly.

 

[Bobsk8 12,489]

4 minutes ago, marc1184 said:

I agree with @medx421. Should have full mixture.

 

Very good but irrelevant since the A2A 172 has no carburetor. It's fuel injected.  

[medx421 50]

31 minutes ago, Bobsk8 said:

Very good but irrelevant since the A2A 172 has no carburetor. It's fuel injected.  

Mixture control is still pertinent in fuel injection systems.  The mixture is just fed through the metering jet into the servo.  It's agreeably different than carburetor mechanics, but still essential.  A2A doesn't have automatic mixture control (AMC).  Being fuel injected, it won't have a primer.

[Bobsk8 12,489]

9 hours ago, medx421 said:

Mixture control is still pertinent in fuel injection systems.  The mixture is just fed through the metering jet into the servo.  It's agreeably different than carburetor mechanics, but still essential.  A2A doesn't have automatic mixture control (AMC).  Being fuel injected, it won't have a primer.

I was referring to carb heat. Wrong checklist for this aircraft. 

[IanHarrison 521]

11 hours ago, Bobsk8 said:

I have this very bizarre habit when I fly an aircraft either in real life or in a sim, of reading the manual. This is what is says for the A2A 172

 

STARTING ENGINE (WITH BATTERY) 1. Throttle — OPEN 1/4 INCH 2. Mixture — IDLE CUTOFF 3. Propeller Area — CLEAR 4. Master Switch — ON 5. Flashing Beacon — ON NOTE: If engine is warm, omit priming procedure of steps 6, 7, and 8 below. 6. Auxiliary Fuel Pump Switch — ON 7. Mixture — SET to FULL RICH (full forward) until stable fuel flow is indicated (usually 3 to 5 seconds), then set to IDLE CUTOFF (full aft) position. 8. Auxiliary Fuel Pump — OFF 9. Ignition Switch — START (release when engine starts) 10. Mixture — ADVANCE smoothly to RICH when engine starts. NOTE: If engine floods (engine has been primed too much), turn off auxiliary fuel pump, set mixture to idle cutoff, open throttle 1/2 to full, and motor (crank) engine. When engine starts, set mixture to full rich and close throttle promptly.

 

What's wrong with you?........... You actually read manuals?........... I had better quickly go and lie down.😂

[Nick M 106]

Hi Andreas,

It sounds like you're using pretty-much the correct technique for our 172R. It's a fuel injected model, so is started with the mixture lever in the idle/cutoff position to prevent over priming.

In fact, I'd say that over priming is the most common reason why customers sometimes have difficulty starting. Sometimes what is judged to be 3-5 seconds of priming with the fuel pump on and mixture pushed in, turns out to be at least 10 seconds once a video of unsuccessful starting attempts is shown!

However, once the engine starts, you need to push the mixture lever in pretty smartly to prevent the engine from dying. There quite a bit to do in short time, so with mouse controls only, it can be a bit tricky until you become used to it.

It's not just sim pilots who struggle with this though, and Cessna produced this video specifically to help operators of fuel injected 172s and 182s avoid over priming. If you have a watch and then apply the principals shown in the sim, you should be good.

Finally, although we try to keep an eye on forums elsewhere, if you have any questions specific to A2A products, you're welcome to post on our forums too.

Kind regards,
Nick

[medx421 50]

Thanks for chiming in @Nick M .  I've always had success starting it the way I outlined, but acknowledge it's the methodology I use when starting a carbureted model IRL.  Essentially just swapping out the primer for the fuel pump.  I start the 172 and 182 in this fashion with good success.  The one I do struggle with is the V35B.  That thing, I have to flood start from the jump.  It's about the only value the mixture seems to have on the ground with that thing.  I can lean it back all the way on the ground without killing the engine.  Probably should go back and revisit those procedures.