Engine RPM mismatch after startup

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Lufthansa 380
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Engine RPM mismatch after startup

Post Lufthansa 380 »

Hey guys, since I wasn't able to figure this out with the manuals and google I thought I just open a topic and get a discussion going, since there are some very knowledgeable members in this forum.

Here's my issue, I wasn't able to solve of figure out on my own: When I start the engines (all procedures as per manual and the sequence usually is 3 - 4 - 2 -1), I sometimes get one or two engines running low on rpm, even when I open the trottle quite a bit, which then again causes the other engines to rev up at around 1500 - 1800 rpm, while the low-running engine stays at around 600-800 RPM. Increasing the prop speed for those individual engines on the FE station doesn't seem to affect them, lowering the rpm for the normal running engines has no effect either. The strange thing is that sometimes I do everything exactly the same and all engines start up just fine, but sometimes 1 or two engines seem to be quite lazy...
I've tried a couple things already, like shutting down the individual engine and restarting it or shutting down all engines, making sure the rpm for all is at max and restarting them again - with no positive result.

Any advice or help is greatly appreciated, since this really is the first sort of problem I've had with A2A aircraft. Anything P-51 or T-6 related was easily resolvable with the manual.

Thanks in advance.

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Levkovvvv
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Re: Engine RPM mismatch after startup

Post Levkovvvv »

Did you try overhauling the engines in the maintenance hangar?
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Lufthansa 380
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Re: Engine RPM mismatch after startup

Post Lufthansa 380 »

Levkovvvv wrote:Did you try overhauling the engines in the maintenance hangar?
No, they are shown in "Excellent" shape with only 2.8 hours on them. Doesn't seem to have anything to do with the state they are in. One flight they start up normally, the other flight some of them just won't start up normally (low rpm).

I might add: I've had an rpm mismatch one time after startup and was perfectly able to fix it with the individual rpm prop switches. The last time, however, I couldn't. If I give the Flight Engineer full control after startup, he simply shuts down the low-running engines after a while. Those electric prop rpm switches are driving me nuts... :lol:

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Levkovvvv
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Re: Engine RPM mismatch after startup

Post Levkovvvv »

Do you have any hardware axis assigned to your rpm lever? I had a problem with rpm control because prop lever was assigned to one of the rotaries on my x-52. As soon as I made a separate profile in fsuipc for connie and unassigned that, everything worked fine.

And once you get used to them, those little switches will be your best friends :D Rpm control is much more accurate.
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Image Владимир Левков / Vladimir Levkov
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Gypsy Baron
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Re: Engine RPM mismatch after startup

Post Gypsy Baron »

I suspect that you need to use the master rpm regulator switch on the pilot/co-pilot pedestal
to run the RPM for all engines to the upper limit stops. It takes a bit of time, depending
upon where they are set when you start. Figure about 100 rpm change for a 2 second interval.

You should run those up until the limit lights come on. Later, in the run-up check you
run them down to the low limit and then back up.

Using the individual switches takes much more time and those should only be used to
synchronize RPM for the engines once started and climbing out.

Paul

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CAPFlyer
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Re: Engine RPM mismatch after startup

Post CAPFlyer »

If you're following normal procedures, you shouldn't have any RPM split when starting as they should have been against the high pitch stop from the end of the last flight (they should have been run to full RPM during final approach or just after landing). If you're throttling up and the engines aren't following, then that says something else is going on. Can you get a screenshot of the FE panel in full when this is happening and post it here? I suspect you've got something weird set and that's what's causing the issue and it's because the engines aren't properly started and not because of the props.
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Lufthansa 380
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Re: Engine RPM mismatch after startup

Post Lufthansa 380 »

I don't use any hardware throttles (or any other external devices) for the RPM controls. I also made sure that the props are at the high pitch stop (all four lights light up, indicating they are all at max rpm), before every startup. I'll do a quick test flight later on and see if I encounter this issue again. Should that be the case then I'll provide screenshots of my setup.

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Lufthansa 380
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Re: Engine RPM mismatch after startup

Post Lufthansa 380 »

Ok, did a testflight and everything worked as it should. Engine 2 and 3 were slightly low on rpm (around 100-200 max. difference)
Don't really know what I've done differently this time. Maybe this time I really made sure all the props were at max before startup.
Should I encounter any issues with rpm mismatch and rpm's being stuck, I'll just report here.

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mallcott
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Re: Engine RPM mismatch after startup

Post mallcott »

Could simply be plug fouling. It IS modelled.

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Lufthansa 380
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Re: Engine RPM mismatch after startup

Post Lufthansa 380 »

Could be. Guess I'll see how the next couple flights go. The Connie sure is a beast to tame!

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Firecapt32
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Re: Engine RPM mismatch after startup

Post Firecapt32 »

I have this same problem. I used to have two throttle sets with enough axis to have one throttle for each engine. Unfortunately, I had a failure of one of the units and haven't replaced it yet. This forced me to assign 1 throttle for all 4 engines. Engines #1 & #2 run at a faster RPM than engines #3 & #4 right after start up. I cycle the props as shown in the checklist and they are still mismatched. I correct this by using the independent PROP RPM switches on the FE's panel to match all 4 engines. Once I've done that the RPM's stay matched on all 4 engines for the rest of the flight using the "master" RPM switch on the front panel.
Flying the A2A C172, C182, T-6, B-17, P-40, P-51, B377, L049 & V35

LostSoul
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Re: Engine RPM mismatch after startup

Post LostSoul »

Just as a sidenote: the props are of the constant speed type and lowest govenring range is 1200 RPM. Whenever the RPM are lower than that and oil pressure has built up the props are in fine pitch. So as long as you are starting up the engines the position of the governor is actually irrelevant (unless you try to start them in feathered position - that would make things a bit different). Nevertheless it is a good idea to have it set to max. RPM as required by the checklist. To avoid plug fouling it might also be a good idea to set 1000 RPM immediately after start-up. Leaving the engines idling definitely leads very quickly to plug fouling and it might require quite some time at higher power to clean them.

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Scott - A2A
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Re: Engine RPM mismatch after startup

Post Scott - A2A »

Keep in mind there is both gauge and prop governor differences. These will change when that particular engine is overhauled and these changes stick, and this will just be the way the airplane is. Also, fouled plugs can remain fouled for quite a long time.

Scott.
A2A Simulations Inc.

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Lufthansa 380
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Re: Engine RPM mismatch after startup

Post Lufthansa 380 »

Scott - A2A wrote:Keep in mind there is both gauge and prop governor differences. These will change when that particular engine is overhauled and these changes stick, and this will just be the way the airplane is. Also, fouled plugs can remain fouled for quite a long time.

Scott.
This is cool! I expect nothing less from A2A. Regarding overhauling and plug fouling - over the years flying A2A pistons I learned how to operate these types of engines and never really had an issue with plug fouling (not that I've noticed, at least). After a couple more flights with the Connie, reading and flying it by the book, I really start to get the hang of it - it really is quite simple to fly (as long as the FE manages the engines and pressurization that is). Speaking of the RPM again - haven't had any issues since, they seem all to work nicely, start up just fine below zero 0°C and purr along in the cruise. Oh and did I mention the sound? It's simply something else with in-ear bass-rich headphones on!

trisho0
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Re: Engine RPM mismatch after startup

Post trisho0 »

Today, I had RPM differences right after I applied Throttle to takeoff and had to stop Connie and brakes On. I went to FE panel and I didn't see how to adjust RPM. I wouldn't mind to do full maintenance but I will loose my flight hours. In hangar, Connie is in excellent status and nothing to repair. So, before proceeding to do Connie repairs I want know why RPM mismatched and if it can be done something.

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