PropSync Oscillations - Accusim Issue?

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TreeTops
Master Sergeant
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Joined: 07 Apr 2010, 06:13

PropSync Oscillations - Accusim Issue?

Post by TreeTops »

I had better post this before I forget about it. Is it something I failed to do or don't undestand yet?
On my second flight fumbling along below 10,000 ft, I reduced the prop RPM's to about 2200 and then engines 2-4 started hunting for prop sync. This was with FE in control of everything.
I have not experienced this in the few flights since.
The thing that puzzled me was, even after taking control from the FE, and reducing power way back and slowly bring it back up, the issue never went away.
Has anyone else experienced this?
Last edited by TreeTops on 15 Apr 2017, 03:56, edited 2 times in total.
Cheers
Trev

alan CXA651
Senior Master Sergeant
Posts: 2438
Joined: 15 Mar 2016, 08:23

Re: PropSync Ossillations

Post by alan CXA651 »

Hi.
The prop sync gauge if all 4 engines are balanced the 3 rotating needles will be stationary , the engineers job is to play around with the individual engines , whenever they get out of sync , to get them back into sync , the reason these apear to osscelate , is because they are telling the engineer , which engine is slow or fast , so he knows which one to adjust and which way to adjust it , and if you are constantly playing with the throttles , he is always going to be playing catch up .
regards alan. 8)
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TreeTops
Master Sergeant
Posts: 1086
Joined: 07 Apr 2010, 06:13

Re: PropSync Ossillations

Post by TreeTops »

True, except these Ossillations were at about 2 per second and the FE was flicking prop switches trying to sort it out without success. RPM's went between about 2000 and 2400.
Cheers
Trev

Gypsy Baron
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Location: San Francisco

Re: PropSync Ossillations

Post by Gypsy Baron »

TreeTops wrote:True, except these Ossillations were at about 2 per second and the FE was flicking prop switches trying to sort it out without success. RPM's went between about 2000 and 2400.
That sounds to me as though there were problems with the engines. The prop sync switches
on the FE panel change the RPM very slowly. It would take a noticeably longer time to run the
RPM from 2000 to 2400.

And since these props are constant speed, throttle changes at cruise are not going to affect the RPM.

Paul

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CAPFlyer
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Location: Wichita Falls, Texas, USA

Re: PropSync Ossillations

Post by CAPFlyer »

Also, how do you have your props controlled? Do you have just 1 lever or switch for all 4, or individual? Is it assigned through FSUIPC, FSX, or the A2A Input Configurator?

What it sounds to me like is that you were getting interference from somewhere that was trying to force the props to 2400RPM and then the FE was trying to bring them back down only to have them overridden by that external force.
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TreeTops
Master Sergeant
Posts: 1086
Joined: 07 Apr 2010, 06:13

Re: PropSync Ossillations

Post by TreeTops »

Currently I don't have any controls assigned to the props since I'm letting the FE handle everything to start with.
Like I said, the 2 flights I have had since then have been flawless, with adjusting the RPMs master in the VC with the mouse as expected.
Cheers
Trev

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CAPFlyer
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Location: Wichita Falls, Texas, USA

Re: PropSync Ossillations

Post by CAPFlyer »

Hrm, that's strange then and makes it nearly impossible to recreate. That was why I was asking more than anything, to see if I could test it myself and get it to happen, but if you've not got any hardware assigned, then it was probably some software or conditional thing that just happened to crop up that one time.
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TreeTops
Master Sergeant
Posts: 1086
Joined: 07 Apr 2010, 06:13

Re: PropSync Ossillations

Post by TreeTops »

I had this happen to me again. Current engines have about 28 hrs on them.
I was 4 hours into a flight, drift climbing through FL220 in smooth air with FE controlling everything. All had been going well and suddenly props 2-4 start wildly oscillating. It has to be the prop sync unit. There has to be a reason behind this. Some type of failure possible?

There were no comments from the crew. Engine inspection is still excellent. Career comments had nothing to reveal.
Flight load was Max. fuel and 7800lbs payload as I was attempting a maximum range flight per the manual specifications pg74
At time of incident the engine settings were 2160 RPM and 120 BMEP per the manual pg 138 power settings table.

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Trev
Cheers
Trev

TreeTops
Master Sergeant
Posts: 1086
Joined: 07 Apr 2010, 06:13

Re: PropSync Ossillations - Accusim Issue?

Post by TreeTops »

Is there any comment from A2A on this issue? It has killed two flights of mine now with no explaination during or after the flight.
Cheers
Trev

TreeTops
Master Sergeant
Posts: 1086
Joined: 07 Apr 2010, 06:13

Re: PropSync Ossillations - Accusim Issue?

Post by TreeTops »

I have just started another flight 3 hours in, without rebuilding anything and its running sweetly.
This problem of hunting RPMs sure is puzzling. There doesn't seem to be any solution to stabilize it during flight and it sure is frustrating when it happens.
Cheers
Trev

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mallcott
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Location: UK

Re: PropSync Ossillations - Accusim Issue?

Post by mallcott »

Turn off the FE, manage props manually. Does it still do it? Could be icing effect.

TreeTops
Master Sergeant
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Joined: 07 Apr 2010, 06:13

Re: PropSync Ossillations - Accusim Issue?

Post by TreeTops »

Yes ive tried turning off the FE.
If it was icing it would it not affect all props not just 2-4 which hunt to sync with 1?
I didn't try the prop de-icer but I will if it happens again. Even if the props had ice, I would have thought flying over Indonesia they would have come good at lower altitudes in the tropics.
The props were oscillating right down to the runway (37 degrees local temp)
Cheers
Trev

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bobsk8
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Location: Atlanta, Georgia

Re: PropSync Ossillations - Accusim Issue?

Post by bobsk8 »

TreeTops wrote:Yes ive tried turning off the FE.
If it was icing it would it not affect all props not just 2-4 which hunt to sync with 1?
I didn't try the prop de-icer but I will if it happens again. Even if the props had ice, I would have thought flying over Indonesia they would have come good at lower altitudes in the tropics.
The props were oscillating right down to the runway (37 degrees local temp)
Think I found the problem, see this thread. https://a2asimulations.com/forum/viewto ... 89#p482026
MSFS 2020
ATC by PF3

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MatzeH84
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Joined: 29 Mar 2013, 14:26
Location: EDLA, Germany

Re: PropSync Oscillations - Accusim Issue?

Post by MatzeH84 »

True, had the same problem with the DC6 after updating P3D.. Obviously the prop sync assignment sneaked back in somehow. Have me a hard time and some terrible swearwords till I found the cause.

Gesendet von meinem F8331 mit Tapatalk
Kind regards, Matthias

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