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Whats Wrong With T-tails Now A Days?  
User currently offlineAlbird87 From , joined Dec 1969, posts, RR:
Posted (7 years 4 weeks 1 day 17 hours ago) and read 2172 times:

Hey folks.
Been searchin the photos and looking at some old DC-9s and 727s and been thinking that with there is a little gap in passenger capacity in the 90-130 seating capacity and also the drop in the designs of T-tail aircraft (apart from the smaller Embraers and CRJs). Is there a bad design in these type of tails with the engines at the rear for larger aircraft??
Would be great i think to see a new Dc-9 looking aircraft but hey im just a guy living in the past!! I would think that the new embraers and CRJs will replace this gap but would be nice to see a new type of aircraft
Your views please

5 replies: All unread, jump to last
 
User currently offlineJBo From Sweden, joined Jan 2005, 2310 posts, RR: 0
Reply 1, posted (7 years 4 weeks 1 day 17 hours ago) and read 2150 times:

This has been discusssed before, search around in here and in tech/ops and you will find some answers.

I believe one of the issues with a T-tail design is a potential angle of attack issue in which the horizontal stabilizer may find itself in the wake of the wings at certain nose-up attitudes, which could disrupt airflow over the horizontal stab creating a control issue. Don't quote me on that, look it up.

The other issue is structure/weight ... the T-tail design requires a stronger - and thus, heavier - tail and tailcone structure to support the weight of the horizontal stabilizers up high, let alone the added weight of rear-mounted engines.

Perhaps the biggest reason you see rear-engine, t-tail designs on regional jets is because the design allows the aircraft to sit lower to the ground, facilitating use of airstair doors, etc.



I'd take the awe of understanding over the awe of ignorance any day.
User currently offlineOsiris30 From Barbados, joined Sep 2006, 3186 posts, RR: 26
Reply 2, posted (7 years 4 weeks 1 day 17 hours ago) and read 2150 times:

albird87:

There have been a whole bunch of threads covering this, so a search might turn up more indepth information than my reply. The long and short of it is that a T-tail is not the optimal tail configuration if you can avoid it. T-tails are generally reserved for when you MUST get the engine from under the wings such as ground hugger (the crj's for example) or military applications (servicing less than ideal landing strips for example).

The simple reason is that a T-tail is much heavier and much more complicated from a maintenance perspective than a non-t-tail. Think about how much strong the vertical fin has to be to support the weight and forces at the top of the tail in a t-tail config. Think also about the hydraulic lines, electrical, etc. which must run up the spine of the tail.

Additionally tail mounted engines can have some problems in their own right which further make it sub-optimal to stick them there, unless you have a darn good reason.



I don't care what you think of my opinion. It's my opinion, so have a nice day :)
User currently offlineViscount724 From Switzerland, joined Oct 2006, 24643 posts, RR: 22
Reply 3, posted (7 years 4 weeks 1 day 10 hours ago) and read 1822 times:

A T-tail adds a lot of unnecessary structure. For example, the overall length of the 727-100 was 133 ft, 33 ft. longer than the 737-200, but the length of the passenger cabin was about the same. The overall length of the shortest DC-9, the series -10, was actually 4 feet longer than the 737-200 due to the T-tail, but the DC-9-10s passenger cabin was much shorter than the 737-200. The 727-200 was even a few inches longer than the longest 707, the -320.

The horizontal stabilizer on top of the tail also is also more difficult to access during maintenance.


User currently offlineAirframeAS From United States of America, joined Feb 2004, 14150 posts, RR: 24
Reply 4, posted (7 years 4 weeks 1 day 4 hours ago) and read 1595 times:

There is a whole bunch of threads on the issue. It has been beat to death. I remember one thread talking about the T-tail types are not as efficient as the standard tails are. In terms of what, I dont remember, I think it had to do with aerodynamics.

But the CRJ's are doing well though.... Thats a design on its own, I believe.



A Safe Flight Begins With Quality Maintenance On The Ground.
User currently offlineTornado82 From , joined Dec 1969, posts, RR:
Reply 5, posted (7 years 4 weeks 1 day 3 hours ago) and read 1567 times:

Quoting JBo (Reply 1):

Perhaps the biggest reason you see rear-engine, t-tail designs on regional jets is because the design allows the aircraft to sit lower to the ground, facilitating use of airstair doors, etc.

Especially considering the CRJ was originally a biz jet, and biz jets tend to sit as low as possible since they're all boarded via steps, not jet bridges.


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