Cool777 From , joined Dec 1969, posts, RR: Posted (13 years 8 months 4 days 4 hours ago) and read 4604 times:
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 ?
FBU 4EVER! From Norway, joined Jan 2001, 998 posts, RR: 7
Reply 4, posted (13 years 8 months 3 days 9 hours ago) and read 4421 times:
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!
Paulc From United Kingdom, joined Mar 2001, 1490 posts, RR: 0
Reply 7, posted (13 years 8 months 2 days 8 hours ago) and read 4371 times:
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.
Speedbird002 From Canada, joined May 2006, 0 posts, RR: 0
Reply 8, posted (13 years 8 months 2 days 8 hours ago) and read 4362 times:
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 From Belgium, joined Sep 2001, 13 posts, RR: 0
Reply 9, posted (13 years 8 months 2 days 6 hours ago) and read 4358 times:
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.
POSITIVE RATE From Australia, joined Sep 2001, 2143 posts, RR: 1
Reply 12, posted (13 years 7 months 3 weeks 4 days 9 hours ago) and read 4293 times:
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)
Ganymed From , joined Dec 1969, posts, RR:
Reply 14, posted (13 years 7 months 3 weeks 2 days ago) and read 4238 times:
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 From Denmark, joined Nov 1999, 111 posts, RR: 1
Reply 15, posted (13 years 7 months 3 weeks 1 day 3 hours ago) and read 4210 times:
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.....