Tu-154 Anhedral

FLYFRONTIER · 10-23-2002, 02:10 AM

Maybe someone out there knows the thinking behind so much anhedral on the Tu-154. Is it due to the wings being so far swept back that they were trying to get rid of a little lateral stability? I know this is done quite often with high wing swept wing aircraft but when it comes to low wing, I only know of it being done with the Tu-154 and the Falcon series.

Phugoid · 10-25-2002, 03:05 PM

Excessive lateral static stability can result in dynamic instability. During flight test they probably found violent Dutch roll behavior. Dihedral acts similarly to sweep and would aggravate the instability, so they employed some anhedral. In modern aircraft it is preferable to use artificial stability controls rather than aerodynamic ones, this generally saves on fuel efficiency, manufacturing costs, design, and structural costs.

10-25-2002, 04:18 PM

That was some go info.

Sentinel Chicken · 10-26-2002, 01:56 AM

My aerodynamics is shaky, but if I remember right, the F-104 Starfighter had significant anhedral to counter the rolling moment induced by the T-tail. I'm presuming this to be something unique to T-tailed low-wing aircraft? Most aircraft of that type I noticed have little to no dihedral compared to low-wing aircraft with conventional tail surfaces.

FLYFRONTIER · 10-26-2002, 07:53 PM

Quote:

Originally posted by Phugoid
Excessive lateral static stability can result in dynamic instability. During flight test they probably found violent Dutch roll behavior. Dihedral acts similarly to sweep and would aggravate the instability, so they employed some anhedral. In modern aircraft it is preferable to use artificial stability controls rather than aerodynamic ones, this generally saves on fuel efficiency, manufacturing costs, design, and structural costs.

Thanks,

That tended to be my suspision that Dutch Roll was found to be excessive. However I would find it interesting that they would change the design of the aircraft after inital test flights rather than install yaw dampers. Then again, the Russians might have figured that the sweepback would be a problem and designed it with the anhedral from the start.

10-23-2002, 02:10 AM	#1
FLYFRONTIER Freight Puppy Join Date: Apr 2001 Location: City by the Bay Posts: 493	Tu-154 Anhedral Maybe someone out there knows the thinking behind so much anhedral on the Tu-154. Is it due to the wings being so far swept back that they were trying to get rid of a little lateral stability? I know this is done quite often with high wing swept wing aircraft but when it comes to low wing, I only know of it being done with the Tu-154 and the Falcon series. __________________ - Please don't confuse me with that other guy

10-26-2002, 01:56 AM	#4
Sentinel Chicken Go-Getters Go Ozark Join Date: Jan 2001 Location: DFW/THE GREAT STATE OF TEXAS Posts: 4,167	My aerodynamics is shaky, but if I remember right, the F-104 Starfighter had significant anhedral to counter the rolling moment induced by the T-tail. I'm presuming this to be something unique to T-tailed low-wing aircraft? Most aircraft of that type I noticed have little to no dihedral compared to low-wing aircraft with conventional tail surfaces. __________________ *Piss on noise abatement!*

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10-25-2002, 03:05 PM	#2
Phugoid Collector Join Date: Aug 2002 Posts: 90	Excessive lateral static stability can result in dynamic instability. During flight test they probably found violent Dutch roll behavior. Dihedral acts similarly to sweep and would aggravate the instability, so they employed some anhedral. In modern aircraft it is preferable to use artificial stability controls rather than aerodynamic ones, this generally saves on fuel efficiency, manufacturing costs, design, and structural costs.

10-25-2002, 04:18 PM	#3
Romania is #1 Guest Posts: n/a	That was some go info.