Guest

T-Tail Vs. Conventional Tail

Sun Sep 30, 2001 12:01 am

I have noticed that most of the east-european designed airliners have T-Tail while T-Tail is very rare on western airliners (actually, used on 727, DC-9 and its derivatives only). Anybody knows what is the reason for this "rule" ? And, in general, what are the main design considerations when choosing between T-Tail and conventional tail when designing a new airplane ?
 
Contact_tower
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RE: T-Tail Vs. Conventional Tail

Sun Sep 30, 2001 3:24 am

Other western airliners with T-tail:

-BAC One Eleven
-Fokker 28/70/100

(And the Aerospatiale Caravel, allmost anyway Big grin)
 
Guest

RE: T-Tail Vs. Conventional Tail

Sun Sep 30, 2001 5:20 am

T-tails are supposedly susceptible to deep stalls, and maintenance is tougher too.
 
IHadAPheo
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RE: T-Tail Vs. Conventional Tail

Sun Sep 30, 2001 12:47 pm

Yippe, I love this stuff keep em coming replies that is
Pray hard but pray with care For the tears that you are crying now Are just your answered prayers
 
FBU 4EVER!
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RE: T-Tail Vs. Conventional Tail

Sun Sep 30, 2001 7:17 pm

And note:all planes mentioned have rear-mounted engines,a conventional tail would not be possible.
Cabin noise considerations were in the forefront when these early jetliners were designed in the late -50's and early -60's,that's why!
"Luck and superstition wins all the time"!
 
Gregg
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RE: T-Tail Vs. Conventional Tail

Sun Sep 30, 2001 8:03 pm

Also the rear wing has to be out of the air flow that goes over the front wing. On smaller a/c it is more important to put the rear wing higher.
 
R4D-5
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RE: T-Tail Vs. Conventional Tail

Mon Oct 01, 2001 2:26 am

... but Caravelle has a cruciform one. Also the Hawker Siddeley (later BAe) HS.125, now developed into Raytheon Hawker 800 and 1000 (Tailplane sits high on the fin, but it is no real T-tail).
 
paulc
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RE: T-Tail Vs. Conventional Tail

Mon Oct 01, 2001 7:50 pm

the tu154/ tu134 / il62 (HS121 Trident also) are all rear engined aircraft so there is the need to keep the tail away from the engines.

IL76 / C5 / C141 /C17 are also T tail but as they are high wing with engines mounted on wing the tail needs to be kept in 'undisturbed air and non exhaust air'

Turbo props like DHC7 / DHC8 follow a similar pattern - even the DHC6 although not a full T tail still has the elevators above the line of the wing to avoid the turbulent air coming from the wing/engines.

The deep stall that rear engined/T tail aircraft are prone to is a result of this - the wing stalls because the angle of attack is too high (or speed too low) and the airflow 'breaks away' from the wing. This disturbed air goes over the T tail and will cause the tail to 'stall' as well. This results in a reduction or total loss of control effectiveness and can place the aircraft in a dangerous situation. The prototype BAC111 was lost as a result of this (then unknown characteristic) and consequently the 'Stick shaker/pusher' was developed to warn the crew if a deep stall situation was close.


English First, British Second, european Never!
 
speedbird002
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RE: T-Tail Vs. Conventional Tail

Mon Oct 01, 2001 7:51 pm

The determining factor as to wheter an aircraft has a 'conventional' tail or 'T' tail is how 'clean' the airflow over the horizontal stabilizer is. Conventional airliners with wings mounted to the bottom of the fuselage and engines in pods under the wing (B737, A320, etc.) have relatively clean airflow at the tail, so they have a 'convetional tail.'

Aircraft with tail-mounted engines (B717,B727, etc.) have engines where the horizontal stabilizers would normally be placed, so they are placed at the top of the fin.

Aircraft with wings mounted to the top of the fuselage and engines mounted in pods under them (BAe 146), don't have 'clean' airflow at the tail because of the wings, so the horizontal stabilizer is placed at the top of the fin.

 
R4D-5
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RE: T-Tail Vs. Conventional Tail

Mon Oct 01, 2001 10:18 pm

Deep stall, also called "super stall" at the time, was already experienced in June 1953 when a Gloster Javelin T-tailed delta fighter prototype was lost and the pilot killed. An aural stall warning device was developed.
 
redngold
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RE: T-Tail Vs. Conventional Tail

Mon Oct 08, 2001 11:49 am

Given the answers relating to deep stall and the high wing, what makes the Shorts 330 different? It has a high wing with wingmounted props, yet has a pretty conventional tail...Comments?

redngold

PS different aside from the fact that it is UGLY.  Smile
Up, up and away!
 
FBU 4EVER!
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RE: T-Tail Vs. Conventional Tail

Mon Oct 08, 2001 6:19 pm

This plane defies all known aerodynamic principles!  Laugh out loud
"Luck and superstition wins all the time"!
 
POSITIVE RATE
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RE: T-Tail Vs. Conventional Tail

Mon Oct 08, 2001 6:32 pm

T-tails were placed on the jets designed with STOL mainly- dunno how it helps exactly. 727/BA146/F28/BAC111/trident/Dash 8/ATR 72/Citation/Learjet/Gulfstream all have t-tails and all of these a/c were designed to operate out of relatively short strips. Anyone know why t-tails affect takeoff/landing distance???(they look pretty cool though)
 
Guest

RE: T-Tail Vs. Conventional Tail

Thu Oct 11, 2001 12:55 am

I think that it has something with the fact that the airplane can accelerate faster with rear-mounted engines.
 
Guest

RE: T-Tail Vs. Conventional Tail

Thu Oct 11, 2001 3:44 am

As Redngold menitoned there are always exceptions to rules like the Shorts 330/360.
More exceptions like these are the Antonov types AN-124/225 AN-12/22 ,Lockheed C-130 ,Fokker F27/50,now how do these designs deal with problems due to the disturbed airflow since they all have high-mounted wings but a 'conventional' tail ?
 
avionic
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RE: T-Tail Vs. Conventional Tail

Fri Oct 12, 2001 12:52 am

I haven´t read the other posts, so i don´t know if i am repeating them, but here are some considerations when you use a T-tail. First of all, the vortex on the top of the fuselage disturb the elevator function of a T-tail. This has been helped by f. ex. on the MD80/90, strakes. The other fact to take into account with a T-tail, is that at high pitch, the elevator tabs will have problems. This means stall problems, and problems getting out of stalls. That´s why some T-tail plane have extensive stall avoidment systems.....

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