windypops

Can somebody please explain in as simple terms as possible why some aircraft with straight wings have swept tails.

Thanks

Intruder

It looks faster.

rudderrudderrat

If your tail has some taper, and you have a straight trailing edge ( to make the elevator hinge system simple) you will have a "swept" looking leading edge.

Edit
Thanks EEngr. Changed aspect to taper.

windypops

Yes the ones I've seen appear to have straight trailing edges and as you say an "apparent swept leading edge". What is the design reason behind this?

EEngr

I think rudderrudderrat was referring to a tail with a tapered planform. That is; a shorter chord at the tip than at the root. The aerodynamic reasoning for this I'll leave to the experts. But the mechanical linkage simplicity of the straight trailing edge control surfaces is valid.

Tu.114

Here is an example - the Ilyushin 28 bomber.



It has unswept wings with a fairly thick profile, but a slim and noticeably swept empennage (and seems to completely ignore the area rule on top). From my limited understanding of physics, I would have expected this to be the other way round - and would be happy to learn if there are any reasons for this setup beside looks.

Tourist

I was told that it was to do with giving a higher max angle of attack before the stall to ensure tailplane controls always work at angles beyond the wings.

Don't know if it is true, but that is what I was told in response to my answer of "cos it looks nice"

Mechta

Having fully swept tail surfaces as per the Ilyushin 28 also moves the effective centre of the surfaces rearwards without extending the fuselage. With the presumably quite heavy tail gunner's compartment there, extending the whole fuselage back could have caused centre of gravity issues.

As for general aviation aircraft (IAI Westwind, Piper Aerostar), I'll go with the 'looks fast' theory.

Tu.114

Mechta -

that´s plausible indeed; that gunner position must have some weight and one would likely not want too many surfaces behind him to block his field of fire. Thank You for Your explanation.

FlightPathOBN

This configuration would direct the turbulence under the ac outward, away from the bomb bays as well...

whiskey1

Increase Mcrit on the tail surface.
Means that the tail will still be effective although the Main plane may be experiencing Mach effects including Mach tuck. Tail remains effective and allows recovery. But yes does look good too.

Tourist

Mcrit not really a problem on lots of aircraft that exhibit swept tails....

Aircraft SP-KWE (1989 British Aerospace Jetstream 3201 C/N 842) Photo by Thomas Ramgraber-VAP (Photo ID: AC189466)

Google Image Result for http://www.airshows.org.uk/news/raf_kingair_1.jpg

FE Hoppy

Mechta has it.


In the case where the main is straight, sweeping the tail isn't for Mach. It's to move the moment arm back. It must prove lighter than lengthening the fuse or increasing the size of the tail.

mustafagander

The engineer in me has always thought that a swept leading edge tailplane would enable a lighter structure - lower fuselage bending moment - and hence a little lower basic weight of the airframe. There are, as previously noted, advantages in straight hinge lines too.