T Tails

[Jeffry Fontaine]

Hi Darren,

Not sure if anyone mentioned this to you earlier or not but Barry Snell (John Howling Mouse) built a T-Tail WHIF a few years ago that was based on the P-51 Mustang which was converted to tricycle landing gear and turbine power plant.  For images and description of his project go to this link: T-51D "Sentinel" Trainer

[Weaver]

One claimed advantage of T-tails was that they wouldn't enter ground effect when landing, thus avoiding a sudden pitching motion just as the aircraft approached the ground. This came to a head with the English Electric P.1, EE insisting that a low tail was better and Boscombe Down insisting on a high one. Eventually the Short SB.5 research aircraft was built with the ability to fit the tail in either position for comparison purposes.  EE were proved right......

[kitnut617]

Originally the P1 was envisioned like this, photo courtesy Phil Butler:

[nev]

The VC-10 is popular will receivers as a tanker because of the lack of turbulence off the tail.  US Navy pilots in Asscrackistan like to specifically request VC-10s to refuel from

[elmayerle]

Well, a T-tail does give the horizontal surface a bit more moment arm so that you can make it a bit smaller and does keep the horizontal surface out of the prop wash.  The T-tail, though, has its own problems with blanking from flow off the wings et al.  I seem to recall that NASA's general aviation testing showed that a cruciform tail was actually a better choice in that it resulted in better recovery from certain extreme conditions and didn't impose as much load on the vertical tail.  If you're wanting to move the horizontal tail for a COIN Mustang derivative (say, a turboprop-powered blend of Mustang and T-28) for a distinctive look, I'd suggest going only part-way up the vertical and using a good fillet around where the two surfaces meet (the Hunter is an excellent example of this).

[The Rat]

Baz would simply say that it looks COOL! Where is he by the way? 

[Hman]

Thanks everyone - it is amazing how one 'dumb' question can really start the ideas flowing. 


Well after all the chat - I had better start the build, even if the COIN Groupbuild hasn't started yet. 

[PR19_Kit]

If I remember correctly (after 45 years or so.....) having the tailplane on top of the fin not only makes the tail more effcient because it's in clear air flow, but also makes the fin more efficent because of the tailplane's end-plate effect. Thus both surfaces can be smaller than otherwise, but of course the fin then needs to be built stronger to take the extra flight loads.

The problem of the T tail being blanketed by the wing at high angles of attack came to the fore when the prototype BAC 1-11 G-ASHG got into a 'deep stall' in October '63 and crashed south of Warminster, killing the entire test crew including Mike Lithgow, one time holder of the World Air Speed Record in a Swift. They were doing stall speed tests and the tail dropped so low that no amount of forward elevator or trim would bring the aircraft out, and it hit the ground going almost vertically downward but in a fairly flat attitude. This one accident resulted in the almost universal adoption of the 'stick shaker' in commercial aircraft to let the crew know when they were approaching a stall etc.

[John Howling Mouse]

Well the obvious answer is that  it makes the plane 1000% cooler

DING! DING! DING!  We have a winner!

[elmayerle]

Talking about Deep stall, that's one reason Learjet eventually went to the delta fins under the aft fuselage that force the tail up before it can get into that condition.  Prior to that a stick-shaker was mandatory on every one.

[PR19_Kit]

You learn something new every day.........

I always wondered what those socking great ventrals were for, when the previous models of almost the same shape managed without them. Presumably as the nose rises the ventrals are then below the wing wake and return some control? Do they have moveable surfaces on them?

[kitnut617]

The problem of the T tail being blanketed by the wing at high angles of attack came to the fore when the prototype BAC 1-11 G-ASHG got into a 'deep stall' in October '63 and crashed south of Warminster, killing the entire test crew including Mike Lithgow, one time holder of the World Air Speed Record in a Swift. They were doing stall speed tests and the tail dropped so low that no amount of forward elevator or trim would bring the aircraft out, and it hit the ground going almost vertically downward but in a fairly flat attitude. This one accident resulted in the almost universal adoption of the 'stick shaker' in commercial aircraft to let the crew know when they were approaching a stall etc.

Just been reading a double volume about the Victors, apparently this also happened to one of the test aircraft before the 1-11 event, and a lot of work was done investigating what had happened.

[elmayerle]

You learn something new every day.........

I always wondered what those socking great ventrals were for, when the previous models of almost the same shape managed without them. Presumably as the nose rises the ventrals are then below the wing wake and return some control? Do they have moveable surfaces on them?

Actually, those delta fins are basically to shove the nose down before it gets too high.  There are no moveable surfaces on them, just two fins set to shove the nose down and prevent a deep stall.  They were doing tunnel testing on them when I was there in the early eighties.