Procedure to starup engine at high altitude airport?

[Japo32]

Hello,

I am doing my world tour with the P51 in P3dv3.2 and today the starting point is sucre SLSU which is at 9500feet high. The problem is I am trying to start the engine and it starts but stays in a situation with black smoke and stutters. I cannot control the fuel mixture.. and the plane don't have any engine issues as I see in the hangar.
Do you know any method to start the engine normally and not in the shift+3 autostart?

Thanks!

[LZ-WIL]

Hi,

Have you tried to increase the rpm as soon as the oil pressure allows it, and check if the black smoke dissipates?
One more thing, check if the engine has the same problems at sea level.

Cheerz,
Will

[Japo32]

No, the plane at sea level is perfect starting up.
I tried the increase of rpm when oil pressure is comming and nothing. Even auto-starting is veeeeeery dificult to startup. Maybe this plane is not prepared for such high altitudes to start engine......

[LZ-WIL]

It may sound silly, but try low and high setting on the supercharger to see, if it would make any difference. After all it was put there to help the engine with air intake.

Cheerz,
Will

[wrkempson]

I went to the airport and have started the engine several times with a minimum of fuss.

First I tried a normal start procedure and had the same problem you describe.

I set the throttle at 75% open since thin air seems to be the culprit. I then primed for an extra couple of seconds. Next I engaged the starter and after the six blades kicked in the magnetos. As the engine began to cough I put the mixture control into run and immediately went back to the primer switch and held it in the up position. The engine continued to sputter for a few seconds and then came to life. The throttle was brought back before rpm's could exceed safe limits and then was set to maintain a good idle. The starter switch was turned off and I was in a normal warm-up posture.

I think the key is to open the throttle almost to max and keep fuel priming into the engine. I tried starting without the extra priming but this resulted in an eventual need for the starter to kick back in. So, for me extra throttle and continuous priming did the trick.

Don't forget your oxygen mask.

Wayne

PS I started out with engaging the turbo, but that did not seem to make a difference.

[robert41]

I have had similar results at high altitude start ups. Need a lot of throttle and the right prime. Usually quite a bit of prime. If it starts to sputter and smoke, this is the plugs fouling. If the plugs do not clear, not much can be done at that point, then it is back to the hangar.

[Tomas Linnet]

maybe it's overprimed?? I'm at Le Alto at 13300ft(ish) with my P-51D Civ. Very sluggish on the throttle during taxi. after shutdown the manifold pressure was only 22", so it must be easy to flood the engine as the air is thin.

[wrkempson]

I just took off from El Alto, Bolivia. I had to prime for 70 seconds, throttle at 90%, mixture on run. Then the starter was engaged after which I had to throttle back quickly when the engine caught. During the first part of warm up the oil pressure was quite high.

Taxi was sluggish due, I suppose, to the thin air. Take off took forever.

Nonetheless, overpriming was not the problem. Even 60 seconds of priming was inadequate.

Hope you find this of interest.

Wayne

[stephan.cote.1]

Not overprimed? With 60 secs??? something is not right here then...
I know stoichiometry is part art, part science but my understanding is that at high altitude (low air density) we should require the same, or less priming then sea level. The idea is that you have less air, so you should require the same primed fuel before flooding in term of quantity of liquid fuel in the chamber, but less in term of Air/fuel ratio. One point of view matters for literally dripping gas on the ground and dipping the plugs, while the other matters for how prone your mixture is to explode when compressed and sparked...

Opening the throttle a bit more, making sure you start with the ram air open should do the trick.. Key here would also be to make sure you are cranking with the mixture cut off (I always do but can't remember if its per POH or not...) and wait for the engine to start dying after it catched before you move the mixture to auto. This way, if you overprimed, you should get back to an explosive mixture in the combustion chambers as each stroke will exhaust a bit of gas and induce a bit more air.

I had to prime for 70 seconds

Was your fuel boost pump on? I'm gessing it could make priming less efficient?

Please correct me if my logic is wrong...
Stephan

[wrkempson]

Stephan, everything you say makes sense to me. I don't fly in the real world, so your point of view is better than mine. All I can say is that this is what happened. And it did not make sense to me either. I would have thought the engine would have been awash in fuel without enough air to burn it. But, it worked. I have no explanation for it.

Try setting up the aircraft at El Alto and give it a go for starting. How should it be done?

Thanks for the insight. Again, you make perfect sense to me.

Wayne

Oh, the fuel pump was on.

[stephan.cote.1]

Stephan, everything you say makes sense to me. I don't fly in the real world, so your point of view is better than mine. All I can say is that this is what happened. And it did not make sense to me either. I would have thought the engine would have been awash in fuel without enough air to burn it. But, it worked. I have no explanation for it.

Try setting up the aircraft at El Alto and give it a go for starting. How should it be done?

Thanks for the insight. Again, you make perfect sense to me.

Wayne

Oh, the fuel pump was on.

Sorry if how I sounded like I was pointing finger at you Wayne... just to clarify, when I said something is not right.... I did not mean you were not right, just so we're clear, I meant more, oh, something is not working as it should....

I'll give it a shot tonight, as I'm at work right now... (psss, don't mention it.. )

Quick question, Did you try this after or prior to this week update? I know A2A worked really hard on the core and supercharger behaviour of the 51 in it...

Stephan

[wrkempson]

Stephan, it was before the update.

I have updated the files and now things work according to your description. The engine (I presume) floods with too much priming in that there was not the slightest hint of catching. I returned to the normal startup procedure (as you described) and with a little coaxing the engine caught.

Thank you for commenting. At no time did I think you were referring to anything other than the situation.

Wayne

[Jacques]

My experience this morning was quite good with the 3-27-2016 update applied. The location was Leadville, Co Lake County Airport which sits at an elevation 9933' and was experiencing a temperature of -12C. I had winter weight oil already on board.

I selected Cold and Dark to make sure the engine was cold-soaked (it was already, but just to be sure). Throttle cracked normally, propeller full increase, mixture idle cut-off, fuel on, pump on and turned the prop six blades. Then primed for seven seconds, mags to both and lifted the starter again. She wasn't going to start, so I began intermittent prime and after about seven seconds the engine caught, mixture to run, rpm set at 900 (until oil temp rose to 10C) then warm up as usual.

The new update fine tuned fuel delivery, among other things. So that might be a source of difficulty if you haven't applied the latest update.

--edit-- Seems you got it sorted! There are a lot of good things with that update!

[EnDSchultz]

Just as a side note that may or may not be related, remember that the Mustang's mixture control has three settings: Cutoff, Run, and Emergency Rich. Make sure when starting you only advance the mixture one notch to the Run setting. While I'm not knowledgeable enough in the Mustang to say for sure, I can certainly imagine that pushing it forward to Emergency Rich during startup at higher elevations might cause the engine some grief.

[Dominique]

the plane don't have any engine issues as I see in the hangar.

Thanks!

Did you do the compression test too ?

I started up the 51 at La Paz without much problem, just adding a couple of shots after the ignition.