B777-200 lateral oscillation in turbulence
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Stilton,
That is an interesting observation. Here is a quick overlay of the tails from the respective manufacturers CAD drawings.
Was surprised to see almost identical tails from 788 and 767-4. There was no difference in -ER variants from the non -ER...A350 and A333 were identical.
That is an interesting observation. Here is a quick overlay of the tails from the respective manufacturers CAD drawings.
Was surprised to see almost identical tails from 788 and 767-4. There was no difference in -ER variants from the non -ER...A350 and A333 were identical.
Interesting graphic, I think it does illustrate my point, the vertical fin
on the triple 7 is quite small for the size of the aircraft for minimal drag
i'm sure.
But it doesn't provide much area and I believe this is a large part of it's 'tail
wagging' tendencies.
on the triple 7 is quite small for the size of the aircraft for minimal drag
i'm sure.
But it doesn't provide much area and I believe this is a large part of it's 'tail
wagging' tendencies.
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This was an interesting little experiement to look at. I did note that all of the Boeing aircraft have the same angle on the back of the their tails, and the Airbus have the same angle on theirs, albeit different between the manufacturers...
The angle on the front of the tails is the same for both manufacturers, with the exception of the 748, which is odd to all (but same beginning point as the A388...)
Perhaps I will try the same with the wings!
The angle on the front of the tails is the same for both manufacturers, with the exception of the 748, which is odd to all (but same beginning point as the A388...)
Perhaps I will try the same with the wings!
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I don't know if anyone has had the pleasure of the back row of a Q400 Dash-8, but they suffer this problem quite a bit during turbulence.
Felt like oversteer in a rear wheel drive car.
Felt like oversteer in a rear wheel drive car.
It’s annoying at the front end too. The oscillation in turbulence is just the right frequency to be resonant with the fluid in our chinaware. Many a time I’ve flown through very light ripples, nowhere near enough to put the seatbelt on, then experienced my tea making a bid for freedom.
First thing I do on getting to the FD (FCC in EASA-land) is stuff the cupholders with towels to soak up the inevitable spillages.
First thing I do on getting to the FD (FCC in EASA-land) is stuff the cupholders with towels to soak up the inevitable spillages.
Stilton, quads will always have a bigger vertical tail than twins. It's that outboard engine effect.
At least on the Boeing side, the aircraft with the minimalistic vertical tail is the 787, not the 777.
At least on the Boeing side, the aircraft with the minimalistic vertical tail is the 787, not the 777.
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727 has massive inertia in empenage
The mass of all three engines goes a long way to reduce the turbulence response of the aft end of the 727.
As for vertical fin leading edge angle, I believe that this is similar to wing sweep angle with respect to the aerodynamics of flight a Mach numbers closer to 1. The 747 has a higher cruise Mach number than most in part enabled by the greater tail sweep angle.
As for vertical fin leading edge angle, I believe that this is similar to wing sweep angle with respect to the aerodynamics of flight a Mach numbers closer to 1. The 747 has a higher cruise Mach number than most in part enabled by the greater tail sweep angle.
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Oscillation Freqency?
I am very curious as to the frequency of the lateral oscillation that is felt in the aft end of the 777. If the frequency is 1 Hz or less the associated mode probably does not involve flexing of structure. If it is 2 Hz or higher it very likely does involve structural flexing.
The 777 control laws involve functions designed to damp out oscillations at various frequencies, both lower frequency "rigid body" motions and higher frequency "structural mode" motions.
The 777 control laws involve functions designed to damp out oscillations at various frequencies, both lower frequency "rigid body" motions and higher frequency "structural mode" motions.
Yes the 787 vertical tail looks small but not out of proportion like the 777 whose fin really looks 'chopped off'
Wonder what its like in the back of a 787 in turbulence ?
Wonder what its like in the back of a 787 in turbulence ?
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Flew the 788 from MEL to AKL...its rattles and creaks quite a bit in the back, well, through the whole ac in turbulence. The center overhead compartment is attached in the center, and was wagging like a yodelers uvula in turbulence.
What is really disturbing was on rotation, the wings really flex up and down until enough speed has settled them down, like an albatros taking off....there was a very apparent up/down motion in the rear of the ac....
the dragon painted down the side seemed very appropriate....
What is really disturbing was on rotation, the wings really flex up and down until enough speed has settled them down, like an albatros taking off....there was a very apparent up/down motion in the rear of the ac....
the dragon painted down the side seemed very appropriate....
