occasional shuddering of engine(s)

[jibjab3]

For each flight plan I keep notes of Gross weight, rpm, torque, mp vis, kias etc. at 5000 feet altitude increments. I am flying COTS
So sometimes I have this problem and sometimes I don't - under identical aircraft/power configurations.
The engines shudder, not constantly, in a wave, smooth for about 20 seconds, shudder for 5 seconds, smooth for 20 seconds.
It starts in the climb and continues in the cruise.
The shuddering sounds like a propeller is broken or out of balance.
As an example, I leveled off into cruise at FL250 with a 16 kt tailwind. My Gross wt. at takeoff was 117150.
Master Propeller =49%
Throttle = 70%
RPM = 1930
MP = 32.5
Torque = 139
Mixture = Auto Lean
Fuel flow = 781
KIAS = 182
Ground Speed = 273 kt / 314 mph

Flight Engineer has FE STATION, PRESSURIZATION and TURBOS.
Damage if OFF
All engines are healthy

Shuddering continues as described above.
I pause, save flight, load saved flight and shuddering disappears. Happens every time, saving and loading saved flight eliminates the problem

[Lewis - A2A]

Hello,

what are you using for your weather, you could be experiencing some gusting, some settles changes and shuddering as the changes are made etc, it could be any number of things. Can you better describe the shuddering, is it on the gauges, if so which gauges for example?

Also are you all updated having run the latest updater?

thanks,
Lewis

[jibjab3]

Lewis,
I am not using any weather add-on and I'm running FSX.
I had the original Wings of Silver + SP1, the bought the COTS ( download version) about 3 months ago.
The odd thing is that it is not on every flight. The 20 seconds smooth, 5 seconds rough is just a rough description.

I found a B377 video on YouTube and if you listen at 17:56 till about 18:40 and you will hear the same noise I am getting, sounds like one prop it just flopping around
I thought I was not using the optimum RPM/MP/Torque setting and played around with various settings but no luck.
The problem is that it is not repeatable.

[jibjab3]

Also. it is not reflected in any of the gauges.
RPM, Fuel Flow, MP, Torque, Cylinder temps etc. are all "normal" and consistent, and all engines are "healthy"

[jibjab3]

forgot to post the Youtube link - https://www.youtube.com/watch?v=LRtDtMci-kI

[FlameOut]

I'm not a real world pilot.

This sounds like what I call the "Shuddering Effect" that Accusim /C.O.T.S. adds to the B 377. I could be wrong.
In this video, at those time markers, he was in that well debated / discussed "... can't get the B 377 out of reverse thrust scenario..."

I've been there plenty of times myself.

The way I cruise at FL 250, at pretty much the same T.O. weight as you've posted.


1. RPM = 1930
2. MP = 32.5
3. Torque = 139
4. Mixture = Auto Lean


mine
1a. RPM = 2100
2a. MP = 36-38
3a. Torque = about 180-189
4a. Mixture = 0.66 manual lean

.... also, Flight Engineer has FE STATION, PRESSURIZATION and TURBOS.
.... me too ... Damage if OFF

You do post a 16 kt. tailwind, which is a good thing and I do not think that is too excessive to cause C.O.T.S. to introduce/inject the shuddering effect/ sounds.

I don not load or save any "flights" ... always start off with that little Trike flying over Friday Harbor, .. chop the throttle, --->> "Go To Airport ", --->> put the Trike on the ground at parking spot at new airport payware, freeware, default, then load up the Stratocrusier.... and off I go...

I wonder if just reloading the same B 377 in mid flight would fix it?
Of course you'd prolly loose you C.O.T.S. settings, Career Mode, Auto pilot, maybe even your loaded passengers, fuel, supplies, etc;

I'm not saying that you are flying it wrong, maybe it's just that "saved flight" thing that FSX gives us sometimes.

[jibjab3]

Hi Flameout,
Thanks for the reply.
As far as the Saved/Load Save flight I described I was not restarting FSX and loading a saved flight. In Cruise I simply paused, saved, and from the dropdown menu selected FLIGHT/LOAD and loaded the saved flight in mid air. Everything is loaded back except you have to do Shift 3 and re-engage the Live Engineer again, the defroster and the ADF/NAV toggle switches. Shuddering stops.

I did 2.5 hour flight this morning, Heavy payload, 16000 pounds of fuel, FL250 with 1 knot tailwind - no shuddering in climb or cruise

I am now on another flight, Heavy payload, 25000 pounds of fuel, cruising at 28000 - no shuddering in climb or cruise - will be going up to 31,000 in about an hour
Current settings;
Auto Lean
1950 RPM (master prop sync at 50%)
Throttle at 75%
MP = 34
Torque = 142
KIAS = 181
Tail wind of 4 kt
Ground speed 278 kt / 320 mph


I will try your configuration on my next flight

[FlameOut]

Good to hear !

[Lewis - A2A]

keep us informed

thanks,
Lewis

[jibjab3]

Made a few flight - 5 to 8 hours each. No shuddering
Now in climb mode out of VIDP - passing 20.000 feet - Heavy payload and 19,000 LB fuel
engine rpm: 2470
throttle: 90%
mixture: Auto Lean
Master Sync: 90%
MP: 47
Torque: 177
VIS: 500 fpm
KIAS: 163
GND SPEED: 238 kt


Shuddering has been continuous since 3000 feet

Then I tried this:
1. Turned all four PROPELLER SELECTOR CONTROL SWITCHES from AUTO to MANUAL
2. Rapidly moved the MASTER PROPELLER SYNCRONIZER from 90% to 100% then back to 90% ( did not on 100)
3. Turned all four PROPELLER SELECTOR CONTROL SWITCHES from MANUAL to AUTO
4. No other changes

shuddering stopped immediately

I have to think that it is some sequence of events/steps that I am unwitting doing that causes the problem.
I keep a log of all fuel/power/pitch settings and under identical settings I will sometimes have the shuddering - sometimes not
Or my Flight Engineer on the shuddering flights is named Murphy and his Law is to blame

I'm now 30 minutes into cruise atFL290 and no shuddering