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TheKennady2
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The Future of rear Engine T-Tails

Fri Apr 19, 2019 2:08 pm

With MD-80 fleets dwindling in the West, 717s getting older and CRJs sells drying up, the future of Rear Engine T-Tails outside of Business jets looks bleak. I was wondering, is there any hope there would even be a new Mainline of larger Regional Jet manufactured in the classic T-Tail design? The Comac ARJ already seems dated it wont likely fly outside of Asia, the CRJs are at Trickle and BBD has still not made a final decision on the future of the CRJ line as a re-engined version likely wont be worth the hassle.

Sadly in most Airports i fly into the type of aircraft is mosly predictable if its a Narrow-body, talk about boring seeing 737s and A320s everywhere, if Asia is any example, Aircraft of the Future looks rather non exciting, with more wide-body types than narrowbodies, everything with wing mounted Engines leaves alot more to be desired, at least the US for now has more variety.
 
GalaxyFlyer
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Re: The Future of rear Engine T-Tails

Fri Apr 19, 2019 2:20 pm

Business jets will remain as t-tails, but not much reason for the design as airliners.

GF
 
JayinKitsap
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Re: The Future of rear Engine T-Tails

Fri Apr 19, 2019 2:27 pm

Until unducted fans like the 7J7 return, rear engine T tails probably won't. The newer engines are heavier than before so rear mounting plays havoc with the CG, sliding the wings back on the plane. All these cost efficiency. The 7E7 for a while had a T tail, it went away for conventional to gain efficiency.
 
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PatrickZ80
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Re: The Future of rear Engine T-Tails

Fri Apr 19, 2019 5:04 pm

T-Tails are history, they're not coming back. It's just more economical to build the engines under the wings.

For T-Tails you need to build the rear of the airframe extra strong. It needs to carry the weight of the engines plus the thrust they provide in-flight. This would make the plane heavier. Building the engines under the wings doesn't face those problems.

Business jets still have the engines mounted on the rear of the airframe, but for how long? It's only a matter of time before the first business jet with underwing engines is being built.
 
djvalume
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Re: The Future of rear Engine T-Tails

Fri Apr 19, 2019 5:24 pm

PatrickZ80 wrote:
It's only a matter of time before the first business jet with underwing engines is being built.


While airliner derivatives the BBJ and ACJ are sold as business jets.
 
cschleic
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Re: The Future of rear Engine T-Tails

Fri Apr 19, 2019 6:02 pm

PatrickZ80 wrote:
T-Tails are history, they're not coming back. It's just more economical to build the engines under the wings.

For T-Tails you need to build the rear of the airframe extra strong. It needs to carry the weight of the engines plus the thrust they provide in-flight. This would make the plane heavier. Building the engines under the wings doesn't face those problems.

Business jets still have the engines mounted on the rear of the airframe, but for how long? It's only a matter of time before the first business jet with underwing engines is being built.


Since business jets don't have the same cost constraints, isn't that one factor that will reduce the likelihood of wing mount bizjets? Also, t-tails provide a quieter cabin and the fuselage is lower to the ground. Perhaps the overall smaller size doesn't make as much of a difference in structure and aerodynamics. Seems like the bizjet world would have begun shifting away from t-tails by now if it was going to be a big trend.
 
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lightsaber
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Re: The Future of rear Engine T-Tails

Fri Apr 19, 2019 10:10 pm

PatrickZ80 wrote:
T-Tails are history, they're not coming back. It's just more economical to build the engines under the wings.

For T-Tails you need to build the rear of the airframe extra strong. It needs to carry the weight of the engines plus the thrust they provide in-flight. This would make the plane heavier. Building the engines under the wings doesn't face those problems.

Business jets still have the engines mounted on the rear of the airframe, but for how long? It's only a matter of time before the first business jet with underwing engines is being built.

There is also a cost for taller landing gear and interfering with the wing fuel subsystem. Those aren't so expensive to engineer.

The issue is the huge amount of parts bin engineering that must occur with business jets due to the limited volumes. The Global 7500 must build off prior globals and the CRJ family (building off the c-series is too big of a price jump). There is numerous gear sets available for T-tails in the correct weight range. Heck, keep building in size off Douglas gear, now owned by United technologies. Northrop and Fokker will also bid.

Honeywell has much pricier landing gear, IIRC, they could sell E-Jet gear. The MRJ has pricey gear too. Both of those are expected to sell enough volume to justify the cost. Great business jets sell 250 to 400 units.
Winter is coming.
 
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Veigar
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Re: The Future of rear Engine T-Tails

Fri Apr 19, 2019 10:12 pm

There are still bizjet trijet t-tails in production. Doubt those are going anywhere anytime soon.
 
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lightsaber
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Re: The Future of rear Engine T-Tails

Fri Apr 19, 2019 10:29 pm

cschleic wrote:
PatrickZ80 wrote:
T-Tails are history, they're not coming back. It's just more economical to build the engines under the wings.

For T-Tails you need to build the rear of the airframe extra strong. It needs to carry the weight of the engines plus the thrust they provide in-flight. This would make the plane heavier. Building the engines under the wings doesn't face those problems.

Business jets still have the engines mounted on the rear of the airframe, but for how long? It's only a matter of time before the first business jet with underwing engines is being built.


Since business jets don't have the same cost constraints, isn't that one factor that will reduce the likelihood of wing mount bizjets? Also, t-tails provide a quieter cabin and the fuselage is lower to the ground. Perhaps the overall smaller size doesn't make as much of a difference in structure and aerodynamics. Seems like the bizjet world would have begun shifting away from t-tails by now if it was going to be a big trend.

T-tails actually have much more cabin noise:
1. Underwing mounted engines have two natural frequency incompatibilities that prevent noise transmission through metal.
2. Engines on the wings also have during cruise the noise move rearward in the airflow so much it misses the cabin.

Search for G500 pilot report. Ugh... Forgetting the site. The GV and G500 have worse resale as the credenza area is too loud for business conversation. The same is true for early Global Express. The G5000 and G6000 solved it by putting double the noise insulation back by the engines. Heck, all BR7xx powered aircraft are notorious for having the click clack noise of engine subsystems penitrates the cabin.

Then again, I'm biased. I designed some replacement subsystems for the Pearl to improve engine efficiency and reduce cabin noise. ;) I'm very happy that engine went into production. I thought my work for RR would never enter service. I also thought it would enter for the BR725 replacement if it did... I'm happy to see my c-series parts on the MRJ too and one purepower subsystem on the whole family. :hyper: But I digress.

If you have ever sat back by the engines of a MD-80, you know too much noise in a T-tail enters the aft cabin.

It is development cost keeping engines on the tail.

Lightsaber
Winter is coming.
 
JohnAudiR18
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Re: The Future of rear Engine T-Tails

Fri Apr 19, 2019 10:52 pm

Embraer E145 Family: Am I joke to you?
 
WayexTDI
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Re: The Future of rear Engine T-Tails

Fri Apr 19, 2019 11:05 pm

Veigar wrote:
There are still bizjet trijet t-tails in production. Doubt those are going anywhere anytime soon.

Which ones?

The only trijet in production are the Dassault 7X/8X & 900; and they are not T-tail per se, the horizontal stabilizer (H-stab) is located about the middle of the vertical stabilizer (V-stab_.
On a true T-tail, the H-stab is located on the top area (very close to the top) of the H-stab.
 
GalaxyFlyer
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Re: The Future of rear Engine T-Tails

Fri Apr 19, 2019 11:11 pm

lightsaber wrote:
cschleic wrote:
PatrickZ80 wrote:
T-Tails are history, they're not coming back. It's just more economical to build the engines under the wings.

For T-Tails you need to build the rear of the airframe extra strong. It needs to carry the weight of the engines plus the thrust they provide in-flight. This would make the plane heavier. Building the engines under the wings doesn't face those problems.

Business jets still have the engines mounted on the rear of the airframe, but for how long? It's only a matter of time before the first business jet with underwing engines is being built.


Since business jets don't have the same cost constraints, isn't that one factor that will reduce the likelihood of wing mount bizjets? Also, t-tails provide a quieter cabin and the fuselage is lower to the ground. Perhaps the overall smaller size doesn't make as much of a difference in structure and aerodynamics. Seems like the bizjet world would have begun shifting away from t-tails by now if it was going to be a big trend.

T-tails actually have much more cabin noise:
1. Underwing mounted engines have two natural frequency incompatibilities that prevent noise transmission through metal.
2. Engines on the wings also have during cruise the noise move rearward in the airflow so much it misses the cabin.

Search for G500 pilot report. Ugh... Forgetting the site. The GV and G500 have worse resale as the credenza area is too loud for business conversation. The same is true for early Global Express. The G5000 and G6000 solved it by putting double the noise insulation back by the engines. Heck, all BR7xx powered aircraft are notorious for having the click clack noise of engine subsystems penitrates the cabin.

Then again, I'm biased. I designed some replacement subsystems for the Pearl to improve engine efficiency and reduce cabin noise. ;) I'm very happy that engine went into production. I thought my work for RR would never enter service. I also thought it would enter for the BR725 replacement if it did... I'm happy to see my c-series parts on the MRJ too and one purepower subsystem on the whole family. :hyper: But I digress.

If you have ever sat back by the engines of a MD-80, you know too much noise in a T-tail enters the aft cabin.

It is development cost keeping engines on the tail.

Lightsaber


The last Global I flew for acceptance had a cabin sound survey down in the low 50s and the quietest part of the cabin is the aft cabin. The design has done wonders for sound levels over the years. Usually, if the forward cabin divider is open, pilots have to be careful with their voices which carry back into the cabin.

Boarding and servicing are reasons fo keep rear engines spas they allow a lower gear height. Loading bags on the G7500 is now as bad as it is on the GV, heights off the ramp about the same.

GF
 
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PatrickZ80
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Re: The Future of rear Engine T-Tails

Sat Apr 20, 2019 8:17 am

JohnAudiR18 wrote:
Embraer E145 Family: Am I joke to you?


True, that's one of the last remaining of a dying species. Once Embraer quits that family, it's done. Their successors, the E170 / E190 families, already have the engines mounted under the wings. So will any future Embraer design.
 
Okie
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Re: The Future of rear Engine T-Tails

Sat Apr 20, 2019 9:23 pm

PatrickZ80 wrote:
True, that's one of the last remaining of a dying species. Once Embraer quits that family, it's done.

EMB still produces the 500 (Phenom 100) and the EMB-505 (Phenom 300) of which has been one of the most popular light jets on the market.
I believe they just cracked 500 examples of the 300.

I am going with GF there won't be a wing mounted VLJ, LJ or Global anytime in the foreseeable future.

About the only adaptation towards wing mounting is the Honda which at this time is considered a VLJ. I am not sure if there is any weight savings by mounting above the wing unless you consider the less weight by not requiring longer landing gear.

Okie
 
Kilopond
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Re: The Future of rear Engine T-Tails

Sat Apr 20, 2019 9:45 pm

The once proposed Rolls-Royce RB3011 is very late as of today. But if it ever materialises, we might see new T-tailed or cross-tailed aeroplanes again. And don`t forget that the CFM companies are working on the same concept.

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