What is the sound I'm hearing?

[kramerdc9]

I was wondering if anybody could help me identify the sound I'm hearing. When I lower my RPM's from 1500 to 1000 or below I hear a clunky noise. Was wondering if it might be a sparkplug, but my plane is in good shape. Can't think of what else it could be and can't get rid of it. I'm hoping it's an easy fix and something I overlooked. If anybody has an idea or knows what this is and what I need to do, I would greatly appreciate your help. Thanks in advance.

[Lewis - A2A]

Hello,

Are you running the latest Accu-sim update?

Is your throttle hitting the stops?

Thanks,
Lewis


Sent from my iPhone using Tapatalk

[TymK]

Wouldn't that be the alternator kicking in/out?

Tym

[AKar]

Wouldn't that be the alternator kicking in/out?

It should always be energized with master and alternator switches on - just the maximum output may lack a bit at very lowest RPMs. I think what Lewis said, the throttle stop. Back when I had more noisier controller, it was rather... well, annoying by clacking it constantly to the stop.

-Esa

[Bruce Hamilton]

Only clunky noise I usually hear is the popping sound of a fouled plug, happens when you run too rich.

[kramerdc9]

Well I think it's fouled spark plugs. I do have the most recent service pack. I have done everything I know of to try to get the plugs unfouled. Changed spark plugs, did complete overhaul, tried 2000rpm for a minute on both magnetos and no sign of fouling. When I go into the hanger it says my plane is in excellent shape. I'm baffled as to what is causing this. Unless it's something else, which I don't think it is since I've heard what the plugs sound like fouled, is this just a sound that is normal when pulling the power down close to 1000rpm's? I try to slowly pull power and not all at once. Does anybody know what this might be and have an idea what I can do to solve it?

Thanks,
Dirk

P.S.
The sound I'm referring to sounds like a knocking sound.

[Oracle427]

With the engine off try moving your throttle all the way forward and back to the stops.

Then try moving your mixture all the way forward and back to the stops.

You should hear a knocking sound when the stops are reached. Is this the sound you are hearing?

[cessnaman]

Is this happening while in the air or on the ground?
Can you post a video or sound bit?
I would think it would be a problem with engine if in the air, but you said the airplane is in excellent shape, so I have no Idea.
Wouldn't sparkplug fouling be more like a popping noise. I did a flight and as I was lifting off the engine was popping, but as I climbed the engine smoothened out so I'm sure it was spark plug fouling.
I didn't do a the before takeoff checklist which is always something I do and I was in a hurry. I'll say this: Always do a the checklists. I could of taken off and had a engine failure.

I really don't think your problem is with fouled plugs.
Is your oil level good? I wonder if something is happening in the engine and it's not noticed in the Maint. yet.

Could it be just a sound issue in your computer? Just a thought.

[kramerdc9]

With the engine off try moving your throttle all the way forward and back to the stops.

Then try moving your mixture all the way forward and back to the stops.

You should hear a knocking sound when the stops are reached. Is this the sound you are hearing?

This could be the noise I hear. I tried what you suggested and did hear the knocking. I've noticed that it only does it sometimes when I lower my rpms from 1500 > 1000 or lower. So the throttle is never pulled out all the way. It just starts popping or knocking when I lower from 1500 > sometimes. Hope this helps.

[Oracle427]

If this is the same sound you are hearing then you probably have a noisy potentiometer in your throttle and/or mixture controls.

I have the Saitek throttle quadrant and the signal is very noisy near the edges of travel. I will hear a rapid knocking whenever I move the levers anywhere near the limits. At I while I just got used to it. I cleaned out the potentiometers once and it stopped, but then it started up again one they got dirty again.

[kramerdc9]

If this is the same sound you are hearing then you probably have a noisy potentiometer in your throttle and/or mixture controls.

I have the Saitek throttle quadrant and the signal is very noisy near the edges of travel. I will hear a rapid knocking whenever I move the levers anywhere near the limits. At I while I just got used to it. I cleaned out the potentiometers once and it stopped, but then it started up again one they got dirty again.

Hey Oracle, was the sound you were referring to the sound of your Saitek controls or the actual aircraft. Because the sound I checked was with the plane off and just increased and decreased the throttle and mixture of the plane in sim. I only have a Saitek X 52. This noise is definitely in the plane itself. Sorry about the confusion.

[TymK]

Hi,

I believe Oracle was referring to electrical noise (dirty potentiometers) in the Saitek throttle quadrant, which then translates into jerky movement of the simulated levers in FSX (possibly hitting the stops and triggering the in-simulator sound effect). I have the same throttle quad and it tends to do that (I've made it a habit to move the levers quickly through the full range of motion several times before flying). I've also noticed the noise you're describing when reducing power. But I've never had any issues with the X52 throttle, it's always been super smooth. Next time I'm flying the 172, I'll keep a close eye on the throttle lever in the virtual cockpit to see how it behaves.

Tym

[Oracle427]

I'm referring to the in game sound effect when the throttle and mixture levers reach their travel limits.

The potentiometers generate a "noisy" signal when they get dirty, but you can't hear that.

Note that on my sim, the virtual levers don't move about erratically most of the time even though the sound of them hitting the stops repeatedly can be heard playing as I move the physical levers near the stops. Sometimes the virtual mixture lever will begin to move erratically forward and back, but if I reposition the physical one on my quadrant just a little that will usually stop the problem.

[kramerdc9]

I'm referring to the in game sound effect when the throttle and mixture levers reach their travel limits.

The potentiometers generate a "noisy" signal when they get dirty, but you can't hear that.

Note that on my sim, the virtual levers don't move about erratically most of the time even though the sound of them hitting the stops repeatedly can be heard playing as I move the physical levers near the stops. Sometimes the virtual mixture lever will begin to move erratically forward and back, but if I reposition the physical one on my quadrant just a little that will usually stop the problem.

Ok, I now understand what your talking about regarding the potentiometers. I too don't have the problem of my virtual levers moving about erratically, although my rpms do bounce a little. I think the problem is that the stop sound is hitting at low rpms and not at idle. This doesn't happen when throttle is pushed all the forward, just when lowering to low rpms. As a test, I disabled my joystick and only used my keyboard. Same thing happened, only more often.

So, to my understanding, this is happening to others and not just me? A2A has done a wonderful job with the aircraft and I enjoy flying it, aside from the noise. My only request would be that maybe Lewis or Scott look into this. My guess would be that their not having the issue, which in that case, I would like to know what the solution might be. Anyway, thanks Oracle427 for your help and insight on the subject. I really couldn't tell what the noise was, but I now know that it's definitely not the spark plugs.

[Oracle427]

To be sure I understand, the sound is confirmed to be the sound of the virtual throttle lever hitting the stop, except that you hear it as you get near to the stop?

I never tried with the keyboard to see what the threshold is for the sound to be triggered. I assumed it was only at 100% or 0%.