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BreninTW
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Benefits Of The T-tail

Fri Feb 22, 2008 1:02 am

I was wondering about this last night. What are the benefits of a T-tail, especially with wing-mounted engines. The only two more-or-less equivalent aircraft I can think of would be the AN-124 and IL-76. They have a similar design, although they do have different roles to play.

Anyway, they both have high-mounted wings with wing-mounted engines. The AN-124 has a standard +-tail, the IL-76 has a T-tail.

From what I understand, the cons of the T-tail are:

Prone to deep stalling
More complex to manufacture and maintain
Empanage may require additional strengthening

Given the cons I've listed above, what are the pros that (in the case of the IL-76) make a T-tail preferable to the +-tail?
 
KELPkid
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RE: Benefits Of The T-tail

Fri Feb 22, 2008 1:36 am

One of the biggest advantage of T-tails, from an airline's perspective, is that the tail plane is now up and out of harm's way (well, mostly, anways-I'm sure someone has figured out how to damage a horizontal stab or elevator on a T-tail in a ramp rash incident  Wink ) and not interfering with the movement of equipment on the ramp.

Another disadvantage: the flight crew cannot do any pre-flight checks involving the elevator or horizontal stabilizer on a T-tailed bird...including snow and ice accumulation.
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bond007
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RE: Benefits Of The T-tail

Fri Feb 22, 2008 2:06 am

Also, of course there is a reason why most high-wing aircraft have a T-tail, right?

AFAIK it's so that the tail and wings are not at the same level, therefore the wing doesn't 'mask' the airflow to the tail.


Jimbo
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tf39
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RE: Benefits Of The T-tail

Fri Feb 22, 2008 2:10 am

Also a nice place to have lunch  Wink

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Quoting KELPkid (Reply 1):
I'm sure someone has figured out how to damage a horizontal stab or elevator on a T-tail

Once in while you'd see damage where someone with jittery fingers slammed a cherry picker bucket into it. Usually pretty minor though. Nice thing about a C-5 is you could climb up the ladder inside the tail and open the hatch to do an inspection on top.
 
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BreninTW
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RE: Benefits Of The T-tail

Fri Feb 22, 2008 2:16 am



Quoting Bond007 (Reply 2):
Also, of course there is a reason why most high-wing aircraft have a T-tail, right?

Well, the two examples I chose both have high wings ... is the AN-124 prone to deep stalling because the wings distort the airflow over the horizontal stabs?

The Fokker-50 has the +-tail and high wings as well, but the Dash-8 has a T-tail, so it seems to me that it's likely to be fairly evenly split.

(I'm not disagreeing with you ... just asking.)

Are there any commercial (jet) aircraft that have wing-mounted engines and T-tails? Most of the jet examples I've found have been military or had military roots.
 
bond007
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RE: Benefits Of The T-tail

Fri Feb 22, 2008 2:25 am

This thread may be of interest:
Will We Ever See Winglets On The Stabiliser (by NEMA Feb 10 2008 in Tech Ops)

Jimbo
I'd rather be on the ground wishing I was in the air, than in the air wishing I was on the ground!
 
N353SK
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RE: Benefits Of The T-tail

Fri Feb 22, 2008 2:58 am



Quoting Brenintw (Reply 4):
Are there any commercial (jet) aircraft that have wing-mounted engines and T-tails? Most of the jet examples I've found have been military or had military roots.

The 328JET has a T tail.
 
T prop
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RE: Benefits Of The T-tail

Fri Feb 22, 2008 4:13 am



Quoting Brenintw (Reply 4):
Are there any commercial (jet) aircraft that have wing-mounted engines and T-tails? Most of the jet examples I've found have been military or had military roots.


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cptspeaking
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RE: Benefits Of The T-tail

Fri Feb 22, 2008 5:02 am

Not a jet (well...technically it is, but you know what I mean...), however having flown the type, I had to stick it in  Smile


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My experience with t-tails is that especially in props, they are great for airplanes used for cross-country flights, but horrible when doing maneuvers. With the tail up and out of the propwash, the elevator axis is always very stable and easily trimmed, but when you get to slower speeds, the response is decreased drastically with the loss of airflow. With a straight tail, you still have the accelerated slipstream going over the tail at lower airspeeds, so you still have plenty of elevator authority.

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KELPkid
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RE: Benefits Of The T-tail

Fri Feb 22, 2008 6:17 am



Quoting Bond007 (Reply 2):
Also, of course there is a reason why most high-wing aircraft have a T-tail, right?

AFAIK it's so that the tail and wings are not at the same level, therefore the wing doesn't 'mask' the airflow to the tail.


Jimbo

Keeping the horizontal stab/elevator out of the stream of the jet engine exhaust is a good idea for more than one reason...
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SEPilot
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RE: Benefits Of The T-tail

Fri Feb 22, 2008 11:30 am

Piper fell in love with T-tails in the 70's, but quickly fell out of love with them. T-tailed Pipers command lower prices in the used market than the equivalent conventional tailed planes; I have only flown one (a Tomahawk) and didn't fly it enough or do enough maneuvers to really see any difference. But I have yet to meet a pilot who prefers them. Mechanics certainly don't; they are more complex and harder to work on.
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Venus6971
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RE: Benefits Of The T-tail

Fri Feb 22, 2008 3:48 pm



Quoting TF39 (Reply 3):
Once in while you'd see damage where someone with jittery fingers slammed a cherry picker bucket into it. Usually pretty minor though. Nice thing about a C-5 is you could climb up the ladder inside the tail and open the hatch to do an inspection on top.

Disadvantage of a C-5 T-tail is that at non C-5 bases it is almost impossible to properly deice since most deicing trucks basket will not go high enough to shoot down on it and keep fluid from running into drybays
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CanadianNorth
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RE: Benefits Of The T-tail

Fri Feb 22, 2008 6:36 pm

From what we just learned in aircrat mechanics school:

T-tail advantages: Horizonal stabilizer and elevators are harder to hit with stuff and generally operate in smoother air
T-tail disadvantages: Can get stuck in a stall, require stronger (thus heavier) vertical stabilizers, and mechanics don't like them


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KELPkid
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RE: Benefits Of The T-tail

Fri Feb 22, 2008 10:11 pm



Quoting SEPilot (Reply 10):
Piper fell in love with T-tails in the 70's, but quickly fell out of love with them. T-tailed Pipers command lower prices in the used market than the equivalent conventional tailed planes; I have only flown one (a Tomahawk) and didn't fly it enough or do enough maneuvers to really see any difference. But I have yet to meet a pilot who prefers them. Mechanics certainly don't; they are more complex and harder to work on.

In a GA plane (twin or single), the biggest difference you're likely to notice between a T-Tail and a conventional tail is the (lack of) induced lift on the horizontal stablilizer/elevator due to prop wash. Adding power at lower airspeeds also increases induced lift from the tail (amost instantaneously), making the nose want to pitch a little higher. I've experienced this in the T-tailed Piper Lancer (from the right seat). Power settings have very little influence over pitch in t-tailed props, since the horizontal portion of the tail is now effectively out of the prop's slipstream...

IIRC, this is one of the (myriad of) look and feel issues that bedeviled early prop pilots making the jump to jets, the fact that in jets the horizontal tail was intentionally placed where the engine outflow would have no effect on the tail, whereas most prop planes placed the horizontal surfaces of the tail right in the propwash.
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FredT
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RE: Benefits Of The T-tail

Sun Feb 24, 2008 8:29 am

Check this thread out:

T-Tail Pros And Cons

No shame in not finding it. The search function does not make it all that easy.

Cheers,
/Fred
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