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Veigar
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Possibility of the 797 having a T-Tail?

Wed Feb 14, 2018 4:28 am

It could be a throwback to the 727 and a good replacement for the 757 since the 727 and 757 are similarly sized, but very old.

In my opinion it'd be quite nice to see another T-Tail Boeing aircraft instead of another cookie cutter type airplane. What do you guys think?

Maybe T-Tails are more inefficient, I actually don't know.
Last edited by atcsundevil on Wed Feb 14, 2018 5:50 am, edited 1 time in total.
Reason: Edited title for clarity
 
jubguy3
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Re: Possibility of the 797 having a T-Tail

Wed Feb 14, 2018 4:29 am

Yes, because Boeing's primary concern is to make a throwback aircraft.
 
SWALUV
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Re: Possibility of the 797 having a T-Tail

Wed Feb 14, 2018 4:31 am

Correct me if I'm wrong, but I believe the main reason T-Tail aircraft aren't designed more often is simply because of the added weight needed for structural purposes.

I would love to see another modern T-Tail though. That'd be gorgeous!
 
phelpsie87
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Re: Possibility of the 797 having a T-Tail

Wed Feb 14, 2018 4:32 am

Similar size? Seriously?
 
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ikolkyo
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Re: Possibility of the 797 having a T-Tail

Wed Feb 14, 2018 4:34 am

No chance.
 
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Veigar
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Re: Possibility of the 797 having a T-Tail

Wed Feb 14, 2018 4:36 am

SWALUV wrote:
Correct me if I'm wrong, but I believe the main reason T-Tail aircraft aren't designed more often is simply because of the added weight needed for structural purposes.

I would love to see another modern T-Tail though. That'd be gorgeous!


Yeah, I had thought this to be the case, but on the flip side, aren't T-Tail airplanes more aerodynamic?
 
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Veigar
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Re: Possibility of the 797 having a T-Tail

Wed Feb 14, 2018 5:05 am

jubguy3 wrote:
Yes, because Boeing's primary concern is to make a throwback aircraft.



Weren't they aiming to do something similar with the 7J7? I believe it looked identical to a 727 minus the s-duct engine and the weird propfans.
 
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TWA772LR
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Re: Possibility of the 797 having a T-Tail

Wed Feb 14, 2018 5:06 am

Veigar wrote:
jubguy3 wrote:
Yes, because Boeing's primary concern is to make a throwback aircraft.



Weren't they aiming to do something similar with the 7J7? I believe it looked identical to a 727 minus the s-duct engine

A 3-engine, UDF, T-tail, MoM plane would be the coolest airliner to grace the skies since Concorde. Would have to have a super tall landing gear so the fans don't hit the runway upon take off, but who cares? That would be one sexy machine! Like the love child of a 727 and Q400!
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caverunner17
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Re: Possibility of the 797 having a T-Tail

Wed Feb 14, 2018 5:08 am

Zero chance. Notice the diameter of today's turbofan engines. I doubt you'd be able to hang a 80" fan off of the tail of an aircraft without serious weight penalty.
 
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Veigar
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Re: Possibility of the 797 having a T-Tail

Wed Feb 14, 2018 5:33 am

TWA772LR wrote:
Veigar wrote:
jubguy3 wrote:
Yes, because Boeing's primary concern is to make a throwback aircraft.



Weren't they aiming to do something similar with the 7J7? I believe it looked identical to a 727 minus the s-duct engine

A 3-engine, UDF, T-tail, MoM plane would be the coolest airliner to grace the skies since Concorde. Would have to have a super tall landing gear so the fans don't hit the runway upon take off, but who cares? That would be one sexy machine! Like the love child of a 727 and Q400!


I don't think it'd be a three engine sadly, maybe the closest thing you can get is a modernized 727 looking air frame with better engines (that aren't too heavy) I'm pretty sure.
'
 
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Re: Possibility of the 797 having a T-Tail

Wed Feb 14, 2018 5:42 am

If NMA as currently imagined sees the light of day, the oval fuselage will be quite striking and prevent any chance of it being "cookie cutter."
 
jubguy3
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Re: Possibility of the 797 having a T-Tail

Wed Feb 14, 2018 5:48 am

seabosdca wrote:
If NMA as currently imagined sees the light of day, the oval fuselage will be quite striking and prevent any chance of it being "cookie cutter."


Everything I've seen seems to indicate that it was going to have a "hamster pouch" fuselage like the 737 engine nacelles
 
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Re: Possibility of the 797 having a T-Tail

Wed Feb 14, 2018 7:29 am

Veigar wrote:
SWALUV wrote:
Correct me if I'm wrong, but I believe the main reason T-Tail aircraft aren't designed more often is simply because of the added weight needed for structural purposes.

I would love to see another modern T-Tail though. That'd be gorgeous!


Yeah, I had thought this to be the case, but on the flip side, aren't T-Tail airplanes more aerodynamic?

What good does that do you though, if you're adding more weight in order to get it?
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Re: Possibility of the 797 having a T-Tail

Wed Feb 14, 2018 8:14 am

Veigar wrote:
jubguy3 wrote:
Yes, because Boeing's primary concern is to make a throwback aircraft.



Weren't they aiming to do something similar with the 7J7? I believe it looked identical to a 727 minus the s-duct engine and the weird propfans.


Yes, over 30 years ago.
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Re: Possibility of the 797 having a T-Tail

Wed Feb 14, 2018 9:03 am

Veigar wrote:
jubguy3 wrote:
Yes, because Boeing's primary concern is to make a throwback aircraft.



Weren't they aiming to do something similar with the 7J7? I believe it looked identical to a 727 minus the s-duct engine and the weird propfans.


Wasn't it supposed to have a t-tail and under wing slung engines ?

http://www.boeingimages.com/archive/Ear ... OIYZR.html
 
kurtverbose
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Re: Possibility of the 797 having a T-Tail?

Wed Feb 14, 2018 9:11 am

...er, isn't deep stall an issue?

Apart from that I think yes, Boeing should focus more on styling and heritage rather than aerodynamics and efficiency. :roll:
 
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Re: Possibility of the 797 having a T-Tail?

Wed Feb 14, 2018 9:23 am

kurtverbose wrote:
...er, isn't deep stall an issue?

Apart from that I think yes, Boeing should focus more on styling and heritage rather than aerodynamics and efficiency. :roll:


If we're talking looks only, then an evolved looking 757 would do me. Something like a 752 could have been had they Max'd it out. ;-)
 
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Veigar
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Re: Possibility of the 797 having a T-Tail

Wed Feb 14, 2018 9:27 am

JannEejit wrote:
Veigar wrote:
jubguy3 wrote:
Yes, because Boeing's primary concern is to make a throwback aircraft.



Weren't they aiming to do something similar with the 7J7? I believe it looked identical to a 727 minus the s-duct engine and the weird propfans.


Wasn't it supposed to have a t-tail and under wing slung engines ?

http://www.boeingimages.com/archive/Ear ... OIYZR.html



That's a good point. To my knowledge, no mass produced aircraft looks like this - correct me if I'm wrong, of course. Wonder why no manufacturer made an airplane like this.
 
bennett123
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Re: Possibility of the 797 having a T-Tail?

Wed Feb 14, 2018 9:42 am

The HS Trident was a T tail.

Got into a stall soon after take off.

The wing masked the tail plane and the result was a flat spin.
 
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VirginFlyer
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Re: Possibility of the 797 having a T-Tail?

Wed Feb 14, 2018 10:11 am

kurtverbose wrote:
...er, isn't deep stall an issue?

bennett123 wrote:
The HS Trident was a T tail.

Got into a stall soon after take off.

The wing masked the tail plane and the result was a flat spin.

In fairness, the Trident, along with numerous other T-tailed types such as the 727, C-141, BAC 1-11, DC-9, F28, VC10, Il-62, Tu-134, Tu-154, C-5, MD-80, BAe-146, F100, ATR 42/72, Dash 8, MD-90, C-17, CRJ series, ERJ series, 717-200, and the bulk of business jet types, have operated without frequent deep stall accidents, in spite of a few well-publicised accidents. If the configuration was inherently unsafe, it wouldn't be certifiable.

This is much more the problem with the configuration:
SWALUV wrote:
Correct me if I'm wrong, but I believe the main reason T-Tail aircraft aren't designed more often is simply because of the added weight needed for structural purposes.

I would love to see another modern T-Tail though. That'd be gorgeous!

Indeed, a T-tail empenage generally works out heavier than a conventional configuration. That why you generally only see them used where needed for other reasons, for instance where a type has rear engines or a high mounted wing, necessitating the horizontal stabiliser to be moved away from the fuselage.

It should be noted in mentioning engine location that provided you can fit engines under the wing, this is the mot structurally efficient layout, since it reduces the amount of lift force which has to be transferred through the wing box, as well as providing relief from bendind moment. That's why in general you only see rear-mounted engines on types which sit low to the ground (where the weight and complexity of larger undercarriage would be a worse solution than the weight of the rear-engine T-tail configuration.

Veigar wrote:
JannEejit wrote:
Wasn't it supposed to have a t-tail and under wing slung engines ?

http://www.boeingimages.com/archive/Ear ... OIYZR.html



That's a good point. To my knowledge, no mass produced aircraft looks like this - correct me if I'm wrong, of course. Wonder why no manufacturer made an airplane like this.

There's a reason this configuration has never been used; there's been no advantage using it instead of a more conventional configuration, and indeed disadvantages from a structural perspective.

As much as we may decry the way in which aircraft increasingly resemble one another, they do this for a reason; it's the best configuration, and it is the natural point of convergence for an airliner design.

V/F
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Re: Possibility of the 797 having a T-Tail?

Wed Feb 14, 2018 10:35 am

A T-tail was considered for the 757. Then they came to their senses.

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Veigar
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Re: Possibility of the 797 having a T-Tail?

Wed Feb 14, 2018 10:51 am

Wow, VirginFlyer, that was a very well constructed post that answered practically every question I've had in my mind about aircraft design. Thank you!

I suppose none of that applies to smaller airplanes though, since T-tailed business jets seem to be the most common (At least in LAS, practically every business jet is a T-tail or cruciform tail). Heck, there are business jets that look exactly like the 727 (even with the 3rd s-duct tail engine) that are commonly used today still. Wonder why that is... another notable example I can think of is the C-5 Galaxy, but since it's a cargo plane, I can only guess that it's a T-Tail for the back cargo door to be easier to open.
 
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Re: Possibility of the 797 having a T-Tail?

Wed Feb 14, 2018 11:22 am

Veigar wrote:
Wow, VirginFlyer, that was a very well constructed post that answered practically every question I've had in my mind about aircraft design. Thank you!

I suppose none of that applies to smaller airplanes though, since T-tailed business jets seem to be the most common (At least in LAS, practically every business jet is a T-tail or cruciform tail). Heck, there are business jets that look exactly like the 727 (even with the 3rd s-duct tail engine) that are commonly used today still. Wonder why that is... another notable example I can think of is the C-5 Galaxy, but since it's a cargo plane, I can only guess that it's a T-Tail for the back cargo door to be easier to open.

Business jets are much smaller and therefore lighter than airliners, so the weight penalties are less significant. If they had underwing engines they would need taller and heavier landing gear which would eat into any advantage gained by having a conventional layout. The bigger the aircraft, the bigger the weight penalty for rear engines/T-tails. T-tails were, to some extent, just a fashionable phase. I believe that Boeing's C-5 proposal had a low mounted tailplane.
 
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Re: Possibility of the 797 having a T-Tail?

Wed Feb 14, 2018 11:28 am

As others have indicated, T-tails are definitely out for airliners due to the structural weight penalties...

It is no coincidence that Airbus, Boeing, Bombardier, Embraer, the Russians, etc all produce similar low wing-podded twin-engined airliners...everyone has arrived at the same conclusion...this is the most efficient design template possible given the present state of technology...

Ubiquitous, sad and boring bleating of airline industry herds worldwide...but nonetheless very efficient...


Faro
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Re: Possibility of the 797 having a T-Tail?

Wed Feb 14, 2018 11:37 am

Faro wrote:
As others have indicated, T-tails are definitely out for airliners due to the structural weight penalties...

It is no coincidence that Airbus, Boeing, Bombardier, Embraer, the Russians, etc all produce similar low wing-podded twin-engined airliners...everyone has arrived at the same conclusion...this is the most efficient design template possible given the present state of technology...

Ubiquitous, sad and boring bleating of airline industry herds worldwide...but nonetheless very efficient...


Faro

Basically, Boeing got it right in 1954 with the 367-80 and today all airliners are built in it's image, other than number of engines.
 
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Re: Possibility of the 797 having a T-Tail?

Wed Feb 14, 2018 11:47 am

JCTJennings wrote:
Faro wrote:
As others have indicated, T-tails are definitely out for airliners due to the structural weight penalties...

It is no coincidence that Airbus, Boeing, Bombardier, Embraer, the Russians, etc all produce similar low wing-podded twin-engined airliners...everyone has arrived at the same conclusion...this is the most efficient design template possible given the present state of technology...

Ubiquitous, sad and boring bleating of airline industry herds worldwide...but nonetheless very efficient...


Faro

Basically, Boeing got it right in 1954 with the 367-80 and today all airliners are built in it's image, other than number of engines.



:checkmark: :checkmark:

Spot on...one can even make the argument that they had got it right in the mid-1940's already (apart from the high-set wing) while designing the B-47, the 367-80's basic design progenitor...nothing really new since then in terms of efficiency...


Faro
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mats01776
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Re: Possibility of the 797 having a T-Tail?

Wed Feb 14, 2018 2:27 pm

In general terms, it makes sound engineering sense to:
1) Put the heaviest components near the center of gravity for balancing the airframe.
2) Put the heaviest components near the center of lift for structural strengthening perspective.
3) Put the enpenage's control surfaces far away from the center of lift for efficiency.
4) Place the center of gravity and center of lift close.

Since the heaviest components are the engines, the fuel tanks ("as filled weight" is variable, however), and the landing gear,
putting all these things near the wing makes sense.

In the 727 configuration, however, since they placed all the engines in the tail:
5) The T-tail is needed to move horizontal stabilizer from interfering with the engines.
6) The wing was shifted to the rear of fuselage to balance the center of gravity and the center of lift.
7) Since the wing was shifted to the rear of fuselage, the stabilizers and their control surfaces had to be enlarged
to account for the loss of "moment arm" from the center of gravity/lift.
8) Since the landing gear was shifted rearward, the tail-strike risk is less, and the landing gear can be made shorter.

I am not sure the T-tail configuration buys you any engineering advantage unless your engine cannot be slung under the wing.
 
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Re: Possibility of the 797 having a T-Tail?

Wed Feb 14, 2018 4:50 pm

mats01776 wrote:
3) Put the enpenage's control surfaces far away from the center of lift for efficiency.

Actually I believe this is one design consideration where a T-tail can help, with a swept fin allowing the horizontal stabiliser to be placed further aft than the end of the fuselage. I am under the impression this was the rationale behind the configuration of aircraft such as the Beech 76 Duchess and 77 Skipper, and the Piper PA-38 Tomahawk (which had its own structural dramas as a result of the configuration). It may be that when you get down to that size the configuration can be the most optimal, although given there are plenty of designs which don't use a T-tail, I'm guessing it is a fairly marginal thing.

V/F
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Re: Possibility of the 797 having a T-Tail?

Wed Feb 14, 2018 5:33 pm

Hm. All of the points posed here bring up the question as to why Boeing even did the design they did when developing the 727. If anything, the rear end of the 727's area (everything where the tail is) would be even HEAVIER with the middle engine that has the S-duct inlet. Also, do low bypass engines only work on this type of aircraft? (If it's as big as the 727 or 757 obviously) I know for a fact no manufacturer will make a plane nowadays with low bypass engines, so it'd make sense as to why it could've worked back then and not now.
 
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Re: Possibility of the 797 having a T-Tail?

Wed Feb 14, 2018 6:05 pm

Veigar wrote:
Hm. All of the points posed here bring up the question as to why Boeing even did the design they did when developing the 727. If anything, the rear end of the 727's area (everything where the tail is) would be even HEAVIER with the middle engine that has the S-duct inlet. Also, do low bypass engines only work on this type of aircraft? (If it's as big as the 727 or 757 obviously) I know for a fact no manufacturer will make a plane nowadays with low bypass engines, so it'd make sense as to why it could've worked back then and not now.

When the 727 was designed, there weren't high bypass turbofans; the JT8D was basically it. They needed three engines for performance. I am under the impression podded engines under the wing were discounted in favour of getting a cleaner wing to enable better field performance. The rest of the design would have flowed on from that.

V/F
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Re: Possibility of the 797 having a T-Tail

Wed Feb 14, 2018 6:10 pm

phelpsie87 wrote:
Similar size? Seriously?


The 727 is less than 2 feet shorter than the 757.
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estorilm
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Re: Possibility of the 797 having a T-Tail?

Wed Feb 14, 2018 8:32 pm

JCTJennings wrote:
Faro wrote:
As others have indicated, T-tails are definitely out for airliners due to the structural weight penalties...

It is no coincidence that Airbus, Boeing, Bombardier, Embraer, the Russians, etc all produce similar low wing-podded twin-engined airliners...everyone has arrived at the same conclusion...this is the most efficient design template possible given the present state of technology...

Ubiquitous, sad and boring bleating of airline industry herds worldwide...but nonetheless very efficient...


Faro

Basically, Boeing got it right in 1954 with the 367-80 and today all airliners are built in it's image, other than number of engines.

I mean, basic aerodynamics and physics dictate most of what you see in designs. Boeing used it a lot - but the ME-262 was essentially a low-wing twin engine plane without a t-tail as well, in 1940. It doesn't really matter if it's carrying passengers or bombs, most aircraft use the same low-wing low-tail design.

As Faro said, everyone just continues to arrive at the same conclusion. Boeing's had great success with it, for sure - but I don't know if I'd imply that everyone else is just following in their footsteps.
 
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Re: Possibility of the 797 having a T-Tail?

Thu Feb 15, 2018 12:07 am

VirginFlyer wrote:
Veigar wrote:
Hm. All of the points posed here bring up the question as to why Boeing even did the design they did when developing the 727. If anything, the rear end of the 727's area (everything where the tail is) would be even HEAVIER with the middle engine that has the S-duct inlet. Also, do low bypass engines only work on this type of aircraft? (If it's as big as the 727 or 757 obviously) I know for a fact no manufacturer will make a plane nowadays with low bypass engines, so it'd make sense as to why it could've worked back then and not now.

When the 727 was designed, there weren't high bypass turbofans; the JT8D was basically it. They needed three engines for performance. I am under the impression podded engines under the wing were discounted in favour of getting a cleaner wing to enable better field performance. The rest of the design would have flowed on from that.

V/F


Another point is that airstairs, including integrated ones, were the norm at the time, so a design with the doors further from the ground had disadvantages.

I fondly remember disembarking from the rear airstairs on the 727. Like emerging from the bowels of a mechanical beast. :)

To VirginFlyer's point, look at how tiny those engines seem compared to today's designs.
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Re: Possibility of the 797 having a T-Tail?

Thu Feb 15, 2018 2:47 am

Help me understand this, please.

In favor of the T-Tail and fuselage-mounted engines, we have:
- Smaller, lighter landing gear.
- Smaller horizontal stab (longer arm)
- Smaller vertical stab and rudder (less asymmetric thrust)
- Smaller wing for the same performance (no engines messing up your aero)

And all of that is more than offset, at least on large transport aircraft, by
- wing bending relief
- vertical stab structural weight
 
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Re: Possibility of the 797 having a T-Tail

Thu Feb 15, 2018 3:07 am

SWALUV wrote:
Correct me if I'm wrong, but I believe the main reason T-Tail aircraft aren't designed more often is simply because of the added weight needed for structural purposes.

I would love to see another modern T-Tail though. That'd be gorgeous!


Hello: You are correct in both the spirit and the letter.

Planes with T-tail have reinforced Structure on a Vertical Stabilizer to Hold Horizontal Stabilizer weight/ lift and it's Moments.
At the same time, should engines are placed on the tail, wing is heavier, cause engines mounted in the wing, "discharge' it from main force component/ moment: :Lift
And Last, ... Fuel System should be more complicate and heavier, cause engines been placed higher will complicate a no electrical power feeding.,

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Re: Possibility of the 797 having a T-Tail?

Thu Feb 15, 2018 3:36 am

Hello: T-Tail a/c were not made first by Boeing. First commercial a/c with engines on Tail and T-tail was Caravelle. And they applied for a patent, so, anyone who followed them, fisrt had to pay the french..
Rgds
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Re: Possibility of the 797 having a T-Tail?

Thu Feb 15, 2018 3:56 am

Apprentice wrote:
Hello: T-Tail a/c were not made first by Boeing. First commercial a/c with engines on Tail and T-tail was Caravelle. And they applied for a patent, so, anyone who followed them, fisrt had to pay the french..
Rgds


Caravelle didn't have a T-tail. It had a cruciform tail. The stab was about half way up the fin.

Image

Florianopolis wrote:
Help me understand this, please.

In favor of the T-Tail and fuselage-mounted engines, we have:
- Smaller, lighter landing gear.
- Smaller horizontal stab (longer arm)
- Smaller vertical stab and rudder (less asymmetric thrust)
- Smaller wing for the same performance (no engines messing up your aero)

And all of that is more than offset, at least on large transport aircraft, by
- wing bending relief
- vertical stab structural weight


There's more. For T-tail aircraft with rear mounted engines.
- More complex fuel system including long fuel lines.
- Not only don't you get wing bending relief. You also don't get wing twisting relief. Engines hung out the front of the wing prevent the leading edge from twisting up.
- Airflow to fuselage mounted engines is less "clean" than in front of the wing.
- Heavier structure because you have to carry more load through the fuselage. With underslung engines, the engines and landing gear are close to the wing box and spars, which are the strongest structures in the aircraft anyway. If you put the engines way back there, you have to support not only the empennage but the engines, with their thrust loads, all the way through the fuselage to the wing box. The "banjo" and tail engine pylon on the DC-10 were massive piece of kit. Just look at all this big structural stuff.

Image
Last edited by Starlionblue on Thu Feb 15, 2018 4:11 am, edited 1 time in total.
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Veigar
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Re: Possibility of the 797 having a T-Tail

Thu Feb 15, 2018 4:12 am

phelpsie87 wrote:
Similar size? Seriously?


Go compare it for yourself - the 727-200 and 757-200 are almost the same length. There's a reason the 757 was a 727 replacement after all!
 
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Re: Possibility of the 797 having a T-Tail?

Thu Feb 15, 2018 5:32 am

Stationblue, hello:
"Caravelle didn't have a T-tail. It had a cruciform tail. The stab was about half way up the fin"
Yes, they preferred to multiply Forces and momentum by L/2 instead of L.

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Re: Possibility of the 797 having a T-Tail?

Thu Feb 15, 2018 5:46 am

Florianapolis, hello: "- Smaller wing for the same performance (no engines messing up your aero)" when engines are hanging from the wing, structure is much lighter

rgds/
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Faro
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Re: Possibility of the 797 having a T-Tail?

Thu Feb 15, 2018 9:38 am

Starlionblue wrote:
VirginFlyer wrote:
Veigar wrote:
Hm. All of the points posed here bring up the question as to why Boeing even did the design they did when developing the 727. If anything, the rear end of the 727's area (everything where the tail is) would be even HEAVIER with the middle engine that has the S-duct inlet. Also, do low bypass engines only work on this type of aircraft? (If it's as big as the 727 or 757 obviously) I know for a fact no manufacturer will make a plane nowadays with low bypass engines, so it'd make sense as to why it could've worked back then and not now.

When the 727 was designed, there weren't high bypass turbofans; the JT8D was basically it. They needed three engines for performance. I am under the impression podded engines under the wing were discounted in favour of getting a cleaner wing to enable better field performance. The rest of the design would have flowed on from that.

V/F


Another point is that airstairs, including integrated ones, were the norm at the time, so a design with the doors further from the ground had disadvantages.

I fondly remember disembarking from the rear airstairs on the 727. Like emerging from the bowels of a mechanical beast. :)

To VirginFlyer's point, look at how tiny those engines seem compared to today's designs.
Image




On a side-note...I continue to be amazed by the magnificently sleek and elegant lines of the 727-200...nothing comes close to it in beauty and elegance...that swept-back, streamlined empannage is pure design magic...


Faro
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Starlionblue
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Re: Possibility of the 797 having a T-Tail?

Thu Feb 15, 2018 9:40 am

Faro wrote:
Starlionblue wrote:
VirginFlyer wrote:
When the 727 was designed, there weren't high bypass turbofans; the JT8D was basically it. They needed three engines for performance. I am under the impression podded engines under the wing were discounted in favour of getting a cleaner wing to enable better field performance. The rest of the design would have flowed on from that.

V/F


Another point is that airstairs, including integrated ones, were the norm at the time, so a design with the doors further from the ground had disadvantages.

I fondly remember disembarking from the rear airstairs on the 727. Like emerging from the bowels of a mechanical beast. :)

To VirginFlyer's point, look at how tiny those engines seem compared to today's designs.
Image




On a side-note...I continue to be amazed by the magnificently sleek and elegant lines of the 727-200...nothing comes close to it in beauty and elegance...that swept-back, streamlined empannage is pure design magic...


Faro


Quite right. I'd say the VC-10 is up there as well, for the same reasons.

Image
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VirginFlyer
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Re: Possibility of the 797 having a T-Tail?

Thu Feb 15, 2018 10:15 am

Starlionblue wrote:
Faro wrote:
Starlionblue wrote:

Another point is that airstairs, including integrated ones, were the norm at the time, so a design with the doors further from the ground had disadvantages.

I fondly remember disembarking from the rear airstairs on the 727. Like emerging from the bowels of a mechanical beast. :)

To VirginFlyer's point, look at how tiny those engines seem compared to today's designs.
Image




On a side-note...I continue to be amazed by the magnificently sleek and elegant lines of the 727-200...nothing comes close to it in beauty and elegance...that swept-back, streamlined empannage is pure design magic...


Faro


Quite right. I'd say the VC-10 is up there as well, for the same reasons.

Image

Yes, aesthetically the rear-engine layout tends to lend itself to beauty.

V/F
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kurtverbose
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Re: Possibility of the 797 having a T-Tail?

Thu Feb 15, 2018 11:00 am

D.B. Cooper killed off the rear air stairs. Just too tempting for passengers to try a parachute jump from.
 
JCTJennings
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Re: Possibility of the 797 having a T-Tail

Thu Feb 15, 2018 11:02 am

Veigar wrote:
phelpsie87 wrote:
Similar size? Seriously?


Go compare it for yourself - the 727-200 and 757-200 are almost the same length. There's a reason the 757 was a 727 replacement after all!

The overall length of the 727 was extended by the rear mounted engines and the swept back fin, you need to compare internal cabin length.
 
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Re: Possibility of the 797 having a T-Tail?

Thu Feb 15, 2018 4:29 pm

kurtverbose wrote:
D.B. Cooper killed off the rear air stairs. Just too tempting for passengers to try a parachute jump from.



I honestly doubt this was the reason. That incident occurred in 1971, and 727s have been used throughout the years even to this day. If he was the reason the rear stairs were canned, then you'd likely have seen major design modifications from 727s back when their production was still going.
 
GalaxyFlyer
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Re: Possibility of the 797 having a T-Tail?

Thu Feb 15, 2018 10:16 pm

On a -200, the aft stairs acted as a “tail pole” in case the aft baggage was loaded first.

Wing mounted engines also allow for fitting engines of different weights from different engine manufacturers because the heavy component is near the CofG.

GF
 
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BaconButty
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Re: Possibility of the 797 having a T-Tail?

Fri Feb 16, 2018 1:56 am

Playing devils advocate, but I think we might see a T-Tail, or at least an unconventional empennage arrangement, on the Narrowbody replacements. I get that with rear mounted engines you have to transmit the loads from the engines to the center of lift, resulting in an overbuilt rear fuselage. But the trade-offs might not be the same next time round. Ultra high bypass engines - or even open rotor - will require far greater ground clearance, and almost every concept you see featuring them has them mounted at the rear. Remember Boeing's Fozzie and Beaker et al? Sure, you might be able to put longer gear on, but what about when you need more clearance for future variants? It's already a constraint on the 737. Also, significant research seems to be going into laminar flow wings (e.g. the A340 BLADE demonstrator) which I assume would benefit from rear mounted engines.

I know as part of Clean Skies they're having a technology demonstrator of innovative empennage designs - U-Tail and V-Tail. I read somewhere they were going to modify a Falcon as a demonstrator, but I can't find a link now. The key driver seems to be noise - in a U-Tail the engines are shrouded, something you can't get with underwing engines. Reducing noise is going to be massive over the course of these new aircrafts lifespans, given the growth we expect to see. In the current generation improvements have come from quieter engine, but surely we're going to hit diminishing returns on that front?

So three big things that could drive a switch to rear mounted engines (if not T-Tail)
* Ever increasing engine diameter
* Clean, (more) Laminar Flow wings
* Noise shielding

My bet (not that I'll remember in 2030) is that the aircraft will look like Boeings beaker (folding wintips and all) but with a U-Tail:
Image
Image
Down with that sort of thing!
 
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Moose135
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Re: Possibility of the 797 having a T-Tail?

Fri Feb 16, 2018 3:18 am

Veigar wrote:
I honestly doubt this was the reason. That incident occurred in 1971, and 727s have been used throughout the years even to this day. If he was the reason the rear stairs were canned, then you'd likely have seen major design modifications from 727s back when their production was still going.

727s in the United States were modified following the Cooper hijacking. The FAA ordered the installation of a device usually referred to as a Cooper Vane. This was a spring-loaded vane, moved by airflow once airborne, that prevented the rear air stair door from opening in flight. Once back on the ground, the spring would move the vane away from the door, allowing it to be opened after landing.
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Veigar
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Re: Possibility of the 797 having a T-Tail?

Fri Feb 16, 2018 4:57 am

Moose135 wrote:
Veigar wrote:
I honestly doubt this was the reason. That incident occurred in 1971, and 727s have been used throughout the years even to this day. If he was the reason the rear stairs were canned, then you'd likely have seen major design modifications from 727s back when their production was still going.

727s in the United States were modified following the Cooper hijacking. The FAA ordered the installation of a device usually referred to as a Cooper Vane. This was a spring-loaded vane, moved by airflow once airborne, that prevented the rear air stair door from opening in flight. Once back on the ground, the spring would move the vane away from the door, allowing it to be opened after landing.


Ah, I see! Thank you for the correction, that's a nice new thing I've learned.

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