Why does the plane shake violently ?

BIG, double-deck, four-engine, medium to long range, high altitude, high speed, commercial transport airplane
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JanF
Airman First Class
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Joined: 19 Oct 2018, 14:10

Why does the plane shake violently ?

Post by JanF »

Sometimes when I throttle up the plane starts to shake violently. Once it also happened after takeoff when I switched four switches from take off to cruise/climb which I find strange since I set the switches to what they must be supposed to be.
Another time during take off it started to shake I then returned the throttle to idle and after that powered up again and then I worked. So what can be wrong when the plane starts to shake violently ?

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Jacques
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Joined: 26 Jun 2011, 17:54
Location: West Coast, USA

Re: Why does the plane shake violently ?

Post by Jacques »

Hi Jan,

The Stratocruiser is a fairly complex and detailed simulation of the Boeing Stratocruiser. any time you start to get violent shaking with throttle movement is usually an indication that you are over-stressing the engines. Reducing throttle and/or propeller rpm will bring the aircraft into a “happier” operating area and the shaking should stop.

Another possible cause of shaking is getting close to, or entering an aircraft condition and speed which is close to, or below, the stall speeds for the aircraft in its current configuration.

Its a great aircraft and very fun to fly, but it does have its quirks! You can learn a lot just by reading past posts in this forum and by reading the manual included with the aircraft!

wrkempson
Airman First Class
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Joined: 17 Apr 2012, 17:26

Re: Why does the plane shake violently ?

Post by wrkempson »

I can produce the shaking by setting the propellers too low. While stopped and with the brake set, run up the engines to takeoff settings and then move the prop slider down and up. You will get the shaking. I suspect that either you have the prop setting at less than full, or that the computer thinks you do. (Do not run the engines this way for more than a few seconds, just long enough to do the test.)

I have had this problem myself but never tracked down a possible cause until just now. My first remedy would be to assure the prop setting is correct.

Here is a shot in the dark, if you control the props with an assigned slider there may be a need to re-calibrate it. Recently I had a problem caused by the brakes being applied so slightly that there was no indication on the screen (that red box in the lower left corner). Is it possible the same thing might happen with the props?

And remember that the computer actually has a mind all its own and does not always behave when it is upset.

Wayne

Hog Driver
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Re: Why does the plane shake violently ?

Post by Hog Driver »

Double check your cowl flaps settings as well, I notice that when I power up and start my take off roll everything is fine but once I start to hit that 70-90 knots area (with cowl flaps open 100%) I would start to get some shaking, start closing my cowls down to around 40% and things start to smooth out... just a thought. Side note: this is from what I remember, it's been a while since I've flown it.
Hog Driver

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JanF
Airman First Class
Posts: 83
Joined: 19 Oct 2018, 14:10

Re: Why does the plane shake violently ?

Post by JanF »

Hog Driver wrote: 29 Mar 2019, 15:07 Double check your cowl flaps settings as well, I notice that when I power up and start my take off roll everything is fine but once I start to hit that 70-90 knots area (with cowl flaps open 100%) I would start to get some shaking, start closing my cowls down to around 40% and things start to smooth out... just a thought. Side note: this is from what I remember, it's been a while since I've flown it.
My cowl flaps was set where the green arc ends

JanF
Airman First Class
Posts: 83
Joined: 19 Oct 2018, 14:10

Re: Why does the plane shake violently ?

Post by JanF »

Jacques wrote: 25 Mar 2019, 11:35 Hi Jan,

The Stratocruiser is a fairly complex and detailed simulation of the Boeing Stratocruiser. any time you start to get violent shaking with throttle movement is usually an indication that you are over-stressing the engines. Reducing throttle and/or propeller rpm will bring the aircraft into a “happier” operating area and the shaking should stop.

Another possible cause of shaking is getting close to, or entering an aircraft condition and speed which is close to, or below, the stall speeds for the aircraft in its current configuration.

Its a great aircraft and very fun to fly, but it does have its quirks! You can learn a lot just by reading past posts in this forum and by reading the manual included with the aircraft!
But if I reduce throttle I wont be able to takeoff. At any rate last time this problem didn't show up. Can this occur if I increase throttle to fast ? Also the last two times I flew the B377 FSX SE crashed. Is the B377 hungry for VAS ?

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Jacques
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Joined: 26 Jun 2011, 17:54
Location: West Coast, USA

Re: Why does the plane shake violently ?

Post by Jacques »

Hi Jan, There is a lot of good information about the possible causes of shaking you experience in the posts above. Perhaps you can let everyone know at what manifold pressure and RPM you start to see and feel the shaking. Also what setting you are using for the turbo. As far as throttle movements, a steady, increase always worked for me. Don’t ram the throttles to the stops, but don’t be overly slow with them either.

JanF
Airman First Class
Posts: 83
Joined: 19 Oct 2018, 14:10

Re: Why does the plane shake violently ?

Post by JanF »

Jacques wrote: 30 Mar 2019, 19:56 Hi Jan, There is a lot of good information about the possible causes of shaking you experience in the posts above. Perhaps you can let everyone know at what manifold pressure and RPM you start to see and feel the shaking. Also what setting you are using for the turbo. As far as throttle movements, a steady, increase always worked for me. Don’t ram the throttles to the stops, but don’t be overly slow with them either.
I try to follow the checklist. So around 60 mp and 2700 rpm I think

wrkempson
Airman First Class
Posts: 79
Joined: 17 Apr 2012, 17:26

Re: Why does the plane shake violently ?

Post by wrkempson »

I don't think any of your settings are incorrect. You seem to be a careful pilot.

I can produce your shaking by advancing the throttle too quickly. Try advancing a shade more slowly. To see the problem in the extreme, set the parking brake, prop to full, and advance the throttle to takeoff pressure. Your will encounter the shaking fairly quickly. You can experiment with different speeds for advancing the throttle. Try a sudden thrust, then try the slowest you can tolerate. Somewhere between the two will be the ideal.

Wayne

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