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Foldable/No Vertical Tail On Airliners?  
User currently offlinecobra27 From Slovenia, joined May 2001, 1012 posts, RR: 0
Posted (1 year 4 months 1 week 5 days 20 hours ago) and read 4535 times:

Idea is to reduce drag (double digit percent improvement). Vertical tail is almost the size of wing on some airliners.

I am more in favour of foldable tail (like F-14 Tomcat wing), which would be used in TO/LDG. In cruise it would partially or completely fold into the fuselage.

The tailless airplane like B-2 bomber seem to work.

Also the horizontal tail could be tweaked, but with less drag reduction

What do you think, could it work? Would there be stability issues?

57 replies: All unread, showing first 25:
 
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17039 posts, RR: 66
Reply 1, posted (1 year 4 months 1 week 5 days 20 hours ago) and read 4523 times:



Quoting cobra27 (Thread starter):
Idea is to reduce drag (double digit percent improvement).

If there was a double digit percentage point reduction to be had without an equivalent rise in some other negative factor, I guarantee we would be flying tail-less airliners today. There are always trade-offs and compromises, and this case is no different.

Quoting cobra27 (Thread starter):
Vertical tail is almost the size of wing on some airliners.

Name one...

Quoting cobra27 (Thread starter):
I am more in favour of foldable tail (like F-14 Tomcat wing), which would be used in TO/LDG. In cruise it would partially or completely fold into the fuselage.

Too much weight added with current materials.

Quoting cobra27 (Thread starter):
The tailless airplane like B-2 bomber seem to work.

It does work. It also requires a lot of fancy software in the flight control systems. The pilots have ejection seats. Nowhere near safe enough for commercial use.

Quoting cobra27 (Thread starter):
What do you think, could it work? Would there be stability issues?

Yes, very much so.

[Edited 2013-05-07 03:00:03]


"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinecobra27 From Slovenia, joined May 2001, 1012 posts, RR: 0
Reply 2, posted (1 year 4 months 1 week 5 days 19 hours ago) and read 4510 times:

Quoting Starlionblue (Reply 1):
Name one...

737
OK, maybe not the size of full wing but close (surely more than half)

Quoting Starlionblue (Reply 1):
Tmuch weight added with current materials.

Current materials are no problem, especially carbon fibres. Weight is a penalty but drag reduction offsets it


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17039 posts, RR: 66
Reply 3, posted (1 year 4 months 1 week 5 days 19 hours ago) and read 4497 times:

Quoting cobra27 (Reply 2):
Quoting Starlionblue (Reply 1):
Name one...

737
OK, maybe not the size of full wing but close (surely more than half)

Not even close. 737NG figures:
- Wing area 124.58 square meters
- Fin area 26.44 meters
- Wing span 34.32 meters
- Fin height 7.16 meters

Again, name one.

Quoting cobra27 (Reply 2):
Quoting Starlionblue (Reply 1):
Tmuch weight added with current materials.

Current materials are no problem, especially carbon fibres. Weight is a penalty but drag reduction offsets it

Carbon fiber is not the issue. The weight and complexity of the folding mechanism is, regardless what material it is made of.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinecobra27 From Slovenia, joined May 2001, 1012 posts, RR: 0
Reply 4, posted (1 year 4 months 1 week 5 days 17 hours ago) and read 4451 times:

Quoting Starlionblue (Reply 3):
Carbon fiber is not the issue. The weight and complexity of the folding mechanism is, regardless what material it is made of.

F-111, F-14, SU-24 all have working folding wings, I think that folding tail should be easier, since it doesn't carry so much load as wing. Dependns how you design it. Also tilting mechanism could be used, which wuld tilt the tail backwards and reduce cross section.
In my opinion there is bigger problem in stability in turbulence for example.


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17039 posts, RR: 66
Reply 5, posted (1 year 4 months 1 week 5 days 17 hours ago) and read 4447 times:

Quoting cobra27 (Reply 4):
F-111, F-14, SU-24 all have working folding wings, I think that folding tail should be easier, since it doesn't carry so much load as wing.

Those are all military design, and thus accept a much higher cost of operation and construction than airliners. I'll also add that they are all old designs. Variable geometry is no longer the go-to solution even among fighter planes.

Quoting cobra27 (Reply 4):
In my opinion there is bigger problem in stability in turbulence for example.

?

[Edited 2013-05-07 05:15:34]


"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineDavid L From United Kingdom, joined May 1999, 9524 posts, RR: 41
Reply 6, posted (1 year 4 months 1 week 5 days 17 hours ago) and read 4443 times:

Quoting cobra27 (Reply 4):
F-111, F-14, SU-24 all have working folding wings

As Starlionblue says, those are not exactly economically efficient examples. And how many of their replacements have variable sweep wings?


User currently offlineptrjong From Netherlands, joined Mar 2005, 3944 posts, RR: 18
Reply 7, posted (1 year 4 months 1 week 5 days 17 hours ago) and read 4441 times:

The B-2 only works because it has little side area.


The only difference between me and a madman is that I am not mad (Salvador Dali)
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17039 posts, RR: 66
Reply 8, posted (1 year 4 months 1 week 5 days 17 hours ago) and read 4426 times:

I just want to make it clear that I am not negative to your ideas because I am conservative in my thinking, cobra27. In fact forward, creative thinking is just what any industry needs. However airplane designers are quite clever and have thought these things out. If there was a double digit efficiency gain to be had, there would be blood in the water. Heck, a 2% total fuel burn improvement is cause for massive investments.

Variable geometry is an elegant solution on paper, and leads to quite big efficiency gains in one area. Unfortunately weight, maintenance and reliability are gigantic issues that negate the efficiency gains. With some sort of "smart" pliable material that could change shape reliably without actuators and massive hydraulics, it would be another story, but with current technology variable geometry is limited to things like flaps.

Quoting ptrjong (Reply 7):
The B-2 only works because it has little side area.

And because it costs a trillion dollars per plane. 

[Edited 2013-05-07 06:18:22]


"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinecobra27 From Slovenia, joined May 2001, 1012 posts, RR: 0
Reply 9, posted (1 year 4 months 1 week 5 days 16 hours ago) and read 4393 times:

Am sure it is more than 9% improvement. Blended wing is a more aerodynamic wing, it also gets less drag since it has no vertical tail and no separate elevator is. You probabaly know that separate elevator makes negative lift for stability

Quoting Starlionblue (Reply 5):
Those are all military design, and thus accept a much higher cost of operation and construction than airliners. I'll also add that they are all old designs. Variable geometry is no longer the go-to solution even among fighter planes.

I don't think they are old designs. I think that commercial airliners pick from military airplanes but at least a decade later.
And I don't think it is so expensive


User currently onlinehorstroad From Germany, joined Apr 2010, 268 posts, RR: 0
Reply 10, posted (1 year 4 months 1 week 5 days 13 hours ago) and read 4339 times:

I don't think that reliability or maintenance costs are an issue.
look at the horizontal stab trim. take the hinge and the big screw and let it work horizontally... not much different...

Quoting Starlionblue (Reply 3):
- Wing span 34.32 meters

the span of the A380 horizontal stabilizer is 30.37m... I think you can call it a wing


User currently offlinerfields5421 From United States of America, joined Jul 2007, 7607 posts, RR: 31
Reply 11, posted (1 year 4 months 1 week 5 days 12 hours ago) and read 4323 times:

We had folding vertical stabilizers on the A-3 Skywarrior in my first USN squadron back 40+ years ago. The wing tips also folded so that the aircraft was about 25% less wide. The folded tail and wings made it possible to fit the plane into a carrier hanger deck, but no one wanted to do so if possible to avoid.

Of course the folding tail wasn't meant to be used in flight.

There was at least one aircraft loss, along with the crew, during the USN usage of the aircraft due to the locking mechanism on the vertical fin failing (no ejection seats).

It was a major maintenance factor. If there was any indication of a leak - the plane was grounded. It added weight and complexity to the aircraft.

Quoting cobra27 (Thread starter):
In cruise it would partially or completely fold into the fuselage.

What direction are you going to fold the vertical stabilizer? There isn't enough fuselage to just fold it down with one fold point.

Every fold point is going to increase the weight of the vertical stabilizer probably 100%. If you fold it four times - that's a 400% increase in weight - right on the very back of the aircraft. COG has to be redesigned.

Quoting cobra27 (Thread starter):
What do you think, could it work?

I think the added weight and the added maintenance and construction complexity would offset any fuel savings quickly. I think it would increase the cost of acquisition and the cost of operation much more than any fuel savings could ever hope to pay back.


User currently offlinecobra27 From Slovenia, joined May 2001, 1012 posts, RR: 0
Reply 12, posted (1 year 4 months 1 week 5 days 12 hours ago) and read 4317 times:

W

Quoting rfields5421 (Reply 11):

What direction are you going to fold the vertical stabilizer? There isn't enough fuselage to just fold it down with one fold point.

I should say hinge or something. You didn't get my point. The crossarea should be reduced so there is not so much drag


User currently offlinemandala499 From Indonesia, joined Aug 2001, 6858 posts, RR: 75
Reply 13, posted (1 year 4 months 1 week 5 days 12 hours ago) and read 4310 times:

Quoting cobra27 (Reply 9):
And I don't think it is so expensive

If military combat aircraft are bound by the same constraints as airliner operating economics, military aviation would be extremely boring.
Those military planes are smaller and lighter yet costs the same if not more to operate and maintain per hour than your average narrowbody airliner... at least in terms of per ton gross weight if not also in absolute terms...

Quoting cobra27 (Reply 9):
Am sure it is more than 9% improvement. Blended wing is a more aerodynamic wing, it also gets less drag since it has no vertical tail and no separate elevator is. You probabaly know that separate elevator makes negative lift for stability

And blended wing body airliners have not been put into production due to...well, not aerodynamical and construction issues, but infrastructure issues, imagine the modifications to put into airports around the world...yikes.



When losing situational awareness, pray Cumulus Granitus isn't nearby !
User currently offlineRoseflyer From United States of America, joined Feb 2004, 9635 posts, RR: 52
Reply 14, posted (1 year 4 months 1 week 5 days 12 hours ago) and read 4307 times:

The failure modes of a hinged rudder & vertical fin are not very appealing. I have no doubt it could be made to work, but the redundancy required and complexity of moving actuators & hydraulic plumbing just to save drag would way far too much to ever make it worthwhile. Folding a wingtip with no control surfaces on the ground to fit into smaller gates on the 777 is enough of a challenge. Folding the entire fin in flight sounds extremely challenging.

If they really want to reduce vertical fin size, they can increase rudder authority with a dual hinge rudder tab. The A320 & 737NG probably could get away with a vertical fin shrink by eliminating the smallest 737-600 & A318 body lengths which decrease the amount of rudder authority needed.

I can think of much better ways to spend tens of millions of development dollars than to hinge the vertical fin to save on drag.

[Edited 2013-05-07 10:49:43]


If you have never designed an airplane part before, let the real designers do the work!
User currently offlinecobra27 From Slovenia, joined May 2001, 1012 posts, RR: 0
Reply 15, posted (1 year 4 months 1 week 5 days 10 hours ago) and read 4225 times:

OK, If I remember correctly, the vertical fin on Cessna 152 has around 3% better range than swept back tail. This is quite a lot for only small angle of sweep
Mooneys have also non swept fins to increase speed.


User currently offlineStitch From United States of America, joined Jul 2005, 30977 posts, RR: 86
Reply 16, posted (1 year 4 months 1 week 5 days 6 hours ago) and read 4159 times:
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The Boeing 377 Stratocruiser had a foldable vertical stabilizer, but that was just so it could fit in short hangars.

User currently offlineStarlionblue From Greenland, joined Feb 2004, 17039 posts, RR: 66
Reply 17, posted (1 year 4 months 1 week 5 days 6 hours ago) and read 4151 times:

Quoting horstroad (Reply 10):
Quoting Starlionblue (Reply 3):
- Wing span 34.32 meters

the span of the A380 horizontal stabilizer is 30.37m... I think you can call it a wing

Heh. Well sure but I was using 737NG numbers. The wingspan of an A380 is almost 80 meters, and the wing area is multiple times the tail area. In other words same story there. Fins are not "half the wing".

Quoting cobra27 (Reply 15):

OK, If I remember correctly, the vertical fin on Cessna 152 has around 3% better range than swept back tail. This is quite a lot for only small angle of sweep

Could you clarify this? I don't quite understand what you mean. AFAIK all 152s have swept tails.

Quoting cobra27 (Reply 15):
Mooneys have also non swept fins to increase speed.

I get the impression that Mooneys have that particular tail shape because it is distinctive.   Jokes aside, you're talking a plane that does under 200 knots. The aerodynamics change considerably one you start on the transonic speed range.

Quoting mandala499 (Reply 13):
If military combat aircraft are bound by the same constraints as airliner operating economics, military aviation would be extremely boring.

              



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinethegeek From Australia, joined Nov 2007, 2638 posts, RR: 0
Reply 18, posted (1 year 4 months 1 week 5 days 5 hours ago) and read 4119 times:

I don't understand the drag reduction claimed.

User currently offlinerfields5421 From United States of America, joined Jul 2007, 7607 posts, RR: 31
Reply 19, posted (1 year 4 months 1 week 5 days 4 hours ago) and read 4091 times:

Quoting cobra27 (Reply 12):
You didn't get my point. The crossarea should be reduced so there is not so much drag

I understand your idea, but you also need to consider the adverse factors.

Where are you going to put the folded segment to minimize frontal cross area?

The fuselage isn't tall enough in the empennage area to hold a 1/2 fold or even 1/6 fold vertical stabilizer.

Only a unit which telescoped into itself would hold the areas you wanted to get out of the air flow, however, you have to increase the cross section by a factor of at least two to create a telescoping mechanism and have it strong enough to withstand the unidirectional air flow and rudder movements. The end result will be MORE drag and more weight.

Any way you do folds, you are going to greatly increase the weight hanging on the very back of the plane. The fold mechanism and extra strengthening needed to support the weight at an unusual angle is a significant weight penalty in carrier aircraft.

Anything which folded the fin to a side by side configuration would increase the drag even with the same frontal surface area because of turbulent airflow between the side by side sections.

You are saying you want to reduce the frontal drag area of the vertical stabilizer and possibly horizontal stabilizer.

Fine.

But where do you propose to put the frontal area you take out of the wind?

The idea was interesting, but I can't get past the physics and the engineering requirements.


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17039 posts, RR: 66
Reply 20, posted (1 year 4 months 1 week 5 days 3 hours ago) and read 4078 times:

Quoting thegeek (Reply 18):
I don't understand the drag reduction claimed.

The full size of the fin and rudder are only needed at low speed with an engine out. At cruise speed the fin and rudder can be much smaller. A variable geometry fin which shrinks at high speed would reduce drag.

Quoting rfields5421 (Reply 19):
But where do you propose to put the frontal area you take out of the wind?

The idea was interesting, but I can't get past the physics and the engineering requirements.

The only way I think this is feasible is with some sort of pliable material that does not need actuators and hydraulics. A bit like an inflatable structure.

[Edited 2013-05-07 19:28:10]


"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinethegeek From Australia, joined Nov 2007, 2638 posts, RR: 0
Reply 21, posted (1 year 4 months 1 week 5 days 2 hours ago) and read 4050 times:

Quoting Starlionblue (Reply 20):
The full size of the fin and rudder are only needed at low speed with an engine out. At cruise speed the fin and rudder can be much smaller. A variable geometry fin which shrinks at high speed would reduce drag.

Hmm, I think I get it now.

Why not just have a rudder with a longer chord and not quite as high? The savings involved in this idea seem pretty minimal and I'm not at all sure where the OP got their double digit savings idea from.

Or an all moving vertical tail, similar to all moving stabilisers on supersonic planes? I'm guessing that it's too heavy and doesn't save enough drag to bother.


User currently offlinerfields5421 From United States of America, joined Jul 2007, 7607 posts, RR: 31
Reply 22, posted (1 year 4 months 1 week 5 days 2 hours ago) and read 4049 times:

Quoting Starlionblue (Reply 20):
The only way I think this is feasible is with some sort of pliable material that does not need actuators and hydraulics.

That was my thought also, but I dismissed it because I can't thing of a current material which would sustain the loads.

Having spent a lot of time around Naval Aviation - the only reason that foldable wings/ tails are used is to make the aircraft fit into smaller deck space or the hanger height requirements.

They are a mechanical liability and weight liability. If the US Navy could avoid them, they would.

Quoting cobra27 (Thread starter):
I am more in favour of foldable tail

Looking back over this - are you talking about a variable geometry tail, not a foldable tail?

One which would pivot back to take much of the frontal area out of the forward wind resistance, and put it in the trailing wind turbulence?

There have been several aircraft with variable geometry wings. The F-111, the F-14, the B-1, the Panavia Tornado, the MiG-23, the MiG-27, the Su-17, the Su-24, the Tu-22M and the Tu-160.

The one thing all have in common is a need to have a steeply swept wing for supersonic flight, and used a forward wing position for landing, slow speed flight.

There was also one aircraft which folded the outer sections of the wing down for an increase in lift during supersonic flight - the XB-70. The purpose was to increase 'compression lift' during supersonic flight. http://upload.wikimedia.org/wikipedi...ican_XB-70_in_Flight_EC68-2131.jpg

The variable geometry wing itself is very complex with the sweep mechanism. Again - a large weight penalty, and reduced ability to use movable conrol surfaces on the swept portion of the wing. The cross section would also likely have to be more than current vertical stabilizer designs.

Such a tail device has probably been studied by NASA and others - but I can't find any reference to any studies.


User currently offlinemandala499 From Indonesia, joined Aug 2001, 6858 posts, RR: 75
Reply 23, posted (1 year 4 months 1 week 5 days ago) and read 4022 times:

Quoting rfields5421 (Reply 22):
If the US Navy could avoid them, they would.

Just to prove your point... The US Navy did avoid it for the A-4 Skyhawk as it specified simplicity and lightweight as a major requirement... folding wings don't go well with those two factors as we know.

Quoting rfields5421 (Reply 22):
The one thing all have in common is a need to have a steeply swept wing for supersonic flight, and used a forward wing position for landing, slow speed flight.

And high subsonic / transonic low level flight.



When losing situational awareness, pray Cumulus Granitus isn't nearby !
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17039 posts, RR: 66
Reply 24, posted (1 year 4 months 1 week 5 days ago) and read 4016 times:

Quoting thegeek (Reply 21):
Why not just have a rudder with a longer chord and not quite as high? The savings involved in this idea seem pretty minimal and I'm not at all sure where the OP got their double digit savings idea from.

I think that gives you more drag in total for the same amount of authority.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinecobra27 From Slovenia, joined May 2001, 1012 posts, RR: 0
Reply 25, posted (1 year 4 months 1 week 4 days 19 hours ago) and read 4068 times:

Quoting thegeek (Reply 21):
Or an all moving vertical tail, similar to all moving stabilisers on supersonic planes? I'm guessing that it's too heavy and doesn't save enough drag to bother.

Yes, that was thought also, increase the rudder and reduce the tail. All movable is the best idea. And it is easier to fold or change geometry.

Quoting rfields5421 (Reply 22):
Looking back over this - are you talking about a variable geometry tail, not a foldable tail?

Basically I am looking to reduce drag no matter which solution.

Conventional tail (both vertical and horizontal surfaces) are good for controlability but less good aerodynamically

I got a feeling if Boeing made a working example other would follow


User currently offlineoly720man From United Kingdom, joined May 2004, 6725 posts, RR: 11
Reply 26, posted (1 year 4 months 1 week 4 days 18 hours ago) and read 4027 times:

Quoting Starlionblue (Reply 24):

Quoting thegeek (Reply 21):
Why not just have a rudder with a longer chord and not quite as high? The savings involved in this idea seem pretty minimal and I'm not at all sure where the OP got their double digit savings idea from.

I think that gives you more drag in total for the same amount of authority.

I'd have thought you'd need the height of the fin so that some effectiveness was maintained at the higher incidences/pitch angles. A smaller fin may be wholly in any separated flow around the fuselage. Also, if the fin was longer the centre of lift would move forwards unless the fuselage was made longer. And a longer fin would need to be thicker to maintain any thickness to chord ratio as constant, for aerodynamic reasons.



wheat and dairy can screw up your brain
User currently offlinecobra27 From Slovenia, joined May 2001, 1012 posts, RR: 0
Reply 27, posted (1 year 4 months 1 week 4 days 18 hours ago) and read 4079 times:

Quoting Starlionblue (Reply 17):
Could you clarify this? I don't quite understand what you mean. AFAIK all 152s have swept tails.

It could have been Cessna 150, I don't remember exactly. Majority of customer choose swept tail because of look.

And I don't think Mooney straight tail is for distinct look only.

Take a look at this airplane Pipistrel Virus
http://en.wikipedia.org/wiki/Pipistrel_Virus
http://www.pipistrel.si/plane/virus-sw/overview

It has a small rudder, again for better aerodynamics. But is harder to fly coordinated turns, you have to use rudder pedals really hard


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17039 posts, RR: 66
Reply 28, posted (1 year 4 months 1 week 4 days 18 hours ago) and read 4073 times:

Quoting cobra27 (Reply 27):
Quoting Starlionblue (Reply 17):
Could you clarify this? I don't quite understand what you mean. AFAIK all 152s have swept tails.

It could have been Cessna 150, I don't remember exactly. Majority of customer choose swept tail because of look.

Umm, no. They chose the swept tail because that's what was offered by Cessna.

You are seriously overestimating the aerodynamic impact of a swept tail on a light piston.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineCaptCufflinks From UK - England, joined Dec 2012, 96 posts, RR: 0
Reply 29, posted (1 year 4 months 1 week 4 days 18 hours ago) and read 4058 times:

Quoting cobra27 (Reply 27):
It could have been Cessna 150, I don't remember exactly.

They're effectively the same aeroplane, a few differences but nothing that major.

Quoting cobra27 (Reply 27):
And I don't think Mooney straight tail is for distinct look only.

I'm almost 3,000% sure he was joking with you.


User currently offlineptrjong From Netherlands, joined Mar 2005, 3944 posts, RR: 18
Reply 30, posted (1 year 4 months 1 week 4 days 11 hours ago) and read 3951 times:

Quoting cobra27 (Reply 25):

Yes, early 150s had a straight tailfin. Early 172s, too.

View Large View Medium
Click here for bigger photo!

Photo © Peter De Jong
View Large View Medium
Click here for bigger photo!

Photo © Peter de Jong


And you're saying this fin has better... range? Please clarify.

[Edited 2013-05-08 11:24:09]


The only difference between me and a madman is that I am not mad (Salvador Dali)
User currently offlinecobra27 From Slovenia, joined May 2001, 1012 posts, RR: 0
Reply 31, posted (1 year 4 months 1 week 4 days 11 hours ago) and read 3936 times:

On some versions it is even more straighter.

User currently offlineptrjong From Netherlands, joined Mar 2005, 3944 posts, RR: 18
Reply 32, posted (1 year 4 months 1 week 4 days 10 hours ago) and read 3921 times:

Oh, so what?

filler blah blah



The only difference between me and a madman is that I am not mad (Salvador Dali)
User currently offlineboeingfixer From Canada, joined Jul 2005, 531 posts, RR: 0
Reply 33, posted (1 year 4 months 1 week 4 days 6 hours ago) and read 3830 times:

Quoting cobra27 (Reply 15):
OK, If I remember correctly, the vertical fin on Cessna 152 has around 3% better range than swept back tail. This is quite a lot for only small angle of sweep
Mooneys have also non swept fins to increase speed.

Where do you come up with this information? It's just making me scratch my head.  

The 152 has always had the same swept back tail as the 150, except for those 150's built prior to 1966 with the straight tails. If you're comparing range between the straight tail 150 and a swept tail 152, there are a few variables to decrease the range of the 152 without taking the straight tail into account. First is the larger engine on the 152 and secondly is the higher empty and gross weights of the 152. The 152 has an almost 10% higher empty weight and an engine with 8 more horsepower than the 150. to loose only 3% in range is testament to the swept back tail and overall design improvements.

As far as the Mooney is concerned, do you have any verifiable data that the Mooney would be slower with a swept fin? The overall design of the distinctive Mooney tail has it's genesis with the Mite. The design incorporated an entire movable tail, for pitch trim, which actually changed the sweep of the vertical fin.

Quoting cobra27 (Reply 31):
On some versions it is even more straighter.

If this is a comment regarding the Cessna straight tails on the 150 and 172's all I have to say is, Huh!? Really, no, Really..... you need to do some serious research before you blurt out random thoughts as fact.

Cheers,

John



Cheers, John YYC
User currently offlineTSS From United States of America, joined Dec 2006, 3068 posts, RR: 5
Reply 34, posted (1 year 4 months 1 week 4 days ago) and read 3728 times:

Quoting rfields5421 (Reply 22):
Quoting cobra27 (Thread starter):
I am more in favour of foldable tail

Looking back over this - are you talking about a variable geometry tail, not a foldable tail?

One which would pivot back to take much of the frontal area out of the forward wind resistance, and put it in the trailing wind turbulence?

I assumed that was what he was talking about from the beginning, and I dismissed the idea as impractical for the reasons you've listed in your post.

That being said, I'd think a V-tail configuration would be a much more reasonable way to reduce the drag caused by having three stabilizers on the rear of a conventional aircraft, but I'm not familiar enough with the drawbacks of the V-tail configuration to know if it would work on an airliner or even if it has been considered for that role.



Able to kill active threads stone dead with a single post!
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17039 posts, RR: 66
Reply 35, posted (1 year 4 months 1 week 4 days ago) and read 3729 times:

Quoting TSS (Reply 34):
That being said, I'd think a V-tail configuration would be a much more reasonable way to reduce the drag caused by having three stabilizers on the rear of a conventional aircraft, but I'm not familiar enough with the drawbacks of the V-tail configuration to know if it would work on an airliner or even if it has been considered for that role.

There's an idea. It certainly decreases drag. The extra complexity of control input vs surface output should not be a big issue on a FBW airliner.

I think pitch trim would be a problem. Any pitch trim movement of the entire surface would entail added drag as the surfaces converge and diverge along the yaw control direction.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinecobra27 From Slovenia, joined May 2001, 1012 posts, RR: 0
Reply 36, posted (1 year 4 months 1 week 3 days 20 hours ago) and read 3713 times:

V-tail seems workable

Quoting boeingfixer (Reply 33):
As far as the Mooney is concerned, do you have any verifiable data that the Mooney would be slower with a swept fin?

No I have no data, its no brainer.

On jets like 737 you need swept wing, because of higher speed. But am not 100% on it


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17039 posts, RR: 66
Reply 37, posted (1 year 4 months 1 week 3 days 20 hours ago) and read 3707 times:

Quoting cobra27 (Reply 36):
Quoting boeingfixer (Reply 33):
As far as the Mooney is concerned, do you have any verifiable data that the Mooney would be slower with a swept fin?

No I have no data, its no brainer.

How is it a no brainer? Please explain.

Quoting cobra27 (Reply 36):
On jets like 737 you need swept wing, because of higher speed. But am not 100% on it

Technically you don't need a swept wing but it is a very good idea. It has to do with delaying shockwave formation at transonic speeds.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinerfields5421 From United States of America, joined Jul 2007, 7607 posts, RR: 31
Reply 38, posted (1 year 4 months 1 week 3 days 18 hours ago) and read 3661 times:

Quoting cobra27 (Reply 36):
No I have no data, its no brainer.

The Mooney forward swept tail fin is a marketing device. Pure and simple.


User currently offlinerfields5421 From United States of America, joined Jul 2007, 7607 posts, RR: 31
Reply 39, posted (1 year 4 months 1 week 3 days 16 hours ago) and read 3644 times:

Quoting TSS (Reply 34):
I assumed that was what he was talking about from the beginning,

I guess my years in the US Navy made me focused on the word "fold" which has a very different meaning than the F-14 swept wings.


User currently offlinecobra27 From Slovenia, joined May 2001, 1012 posts, RR: 0
Reply 40, posted (1 year 4 months 1 week 3 days 15 hours ago) and read 3631 times:

We love to fly. Fast.!!!

May I propose a question:
How much of the total drag does 737 or A320 goes to tail?


User currently offlineRoseflyer From United States of America, joined Feb 2004, 9635 posts, RR: 52
Reply 41, posted (1 year 4 months 1 week 3 days 14 hours ago) and read 3616 times:

Quoting cobra27 (Reply 40):
How much of the total drag does 737 or A320 goes to tail?

Are you talking about the verticial stabilizer? If so, very little because there is no induced drag in cruise. There is only parasite drag. The horizontal stabilizer produces far more drag since it produces induced drag as well. I gave you an idea about that, but you seemed to ignore it.



If you have never designed an airplane part before, let the real designers do the work!
User currently offlineViscount724 From Switzerland, joined Oct 2006, 25300 posts, RR: 22
Reply 42, posted (1 year 4 months 1 week 3 days 10 hours ago) and read 3566 times:

Quoting Starlionblue (Reply 20):
The full size of the fin and rudder are only needed at low speed with an engine out. At cruise speed the fin and rudder can be much smaller. A variable geometry fin which shrinks at high speed would reduce drag.

Why don't they design the vertical stabilizer so the entire stabilizer can pivot around a central point, similar to the way the entire horizontal stabilizer on most larger aircraft can pivot around a central axis. It seems to me that if the vertical stabilizer could pivot the same way (and not just the rudder) it would permit a smaller vertical stabilizer. It wouldn't have to be used very often, but for example in the event of an engine failure on takeoff, if the stabilizer could pivot in addition to the rudder, it would provide enough side force to keep straight without the need for a very tall stabilizer as on aircraft like the A380 and 747SP.

Quoting Stitch (Reply 16):
The Boeing 377 Stratocruiser had a foldable vertical stabilizer, but that was just so it could fit in short hangars.

Photo:

http://www.ovi.ch/b377/articles/speedbird/hangar.jpg


User currently offlinethegeek From Australia, joined Nov 2007, 2638 posts, RR: 0
Reply 43, posted (1 year 4 months 1 week 3 days 6 hours ago) and read 3514 times:

Quoting Starlionblue (Reply 24):
I think that gives you more drag in total for the same amount of authority.

Presumably, or they'd be doing it.

Quoting TSS (Reply 34):

That being said, I'd think a V-tail configuration would be a much more reasonable way to reduce the drag
Quoting Starlionblue (Reply 35):
There's an idea. It certainly decreases drag. The extra complexity of control input vs surface output should not be a big issue on a FBW airliner.

I think pitch trim would be a problem. Any pitch trim movement of the entire surface would entail added drag as the surfaces converge and diverge along the yaw control direction.

Interesting thoughts. Indeed the entire negative lift required from the stabiliser would have a self cancelling component so you would have a loss there. I don't see where the benefit comes in, actually, except shorter total protrusion. I doubt that would cancel out the aforementioned loss.


User currently offlinecobra27 From Slovenia, joined May 2001, 1012 posts, RR: 0
Reply 44, posted (1 year 4 months 1 week 2 days 21 hours ago) and read 3444 times:

Quoting rfields5421 (Reply 38):
The Mooney forward swept tail fin is a marketing device. Pure and simple.

Am a little confused with the terminology used. Is it really forwardly swept? Looking at the pictures is straight - perpendicular to the airflow. If you make it that way, you can have a smaller fin

[Edited 2013-05-10 02:00:51]

User currently offlineStarlionblue From Greenland, joined Feb 2004, 17039 posts, RR: 66
Reply 45, posted (1 year 4 months 1 week 2 days 19 hours ago) and read 3426 times:

Quoting cobra27 (Reply 44):
Quoting rfields5421 (Reply 38):
The Mooney forward swept tail fin is a marketing device. Pure and simple.

Am a little confused with the terminology used. Is it really forwardly swept? Looking at the pictures is straight - perpendicular to the airflow. If you make it that way, you can have a smaller fin

The leading edge is perpendicular to airflow. The trailing edge is forward swept.

I still don't understand how you can make a smaller fin that way...



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinerfields5421 From United States of America, joined Jul 2007, 7607 posts, RR: 31
Reply 46, posted (1 year 4 months 1 week 2 days 16 hours ago) and read 3393 times:

Quoting cobra27 (Reply 44):
Is it really forwardly swept?

The forward edge is vertical, the rudder side is forward swept.

Mooney photography for their website and brochures is shot at an angle to make the optical illusion that the stabilizer is forward swept to enhance the impression of speed.

Mooney sells their aircraft based on the marketing of the aircraft speed, not fuel economy.


User currently offlineKlaus From Germany, joined Jul 2001, 21461 posts, RR: 53
Reply 47, posted (1 year 4 months 1 week 2 days 15 hours ago) and read 3377 times:

Quoting Viscount724 (Reply 42):
Why don't they design the vertical stabilizer so the entire stabilizer can pivot around a central point, similar to the way the entire horizontal stabilizer on most larger aircraft can pivot around a central axis.

You'd need a rather massive hinge mechanism for that, even more massive than the one for the horizontal stabilizer (which is already substantial), because that one is symmetrical which keeps the resulting bending moment on the hinge at balance because the entire horizontal stabilizer is just one single piece with an integral beam running through the fuselage, linked to a common hinge and a motor-driven trim screw.

An all-moving vertical fin would concentrate a very large asymmetrical bending moment (not least because of the long, single moment arm) in the hinge assembly as a single point of failure, which would also require substantial structural support to transfer those loads safely to the fuselage.

There are fighter jets with such all-moving fins as far as I'm aware, but they are geared for performance first and foremost, with economy (=range) as secondary concerns. Plus, their pilots have ejection seats.

The conventional static fin bolted to the fuselage in multiple places (thus distributing the load) and with split rudders for increased redundancy looks like a pretty good idea for airliners which need to be safe and efficient above all else.

[Edited 2013-05-10 09:02:15]

User currently offlinecobra27 From Slovenia, joined May 2001, 1012 posts, RR: 0
Reply 48, posted (1 year 4 months 1 week 2 days 11 hours ago) and read 3344 times:

Quoting Klaus (Reply 47):

There are fighter jets with such all-moving fins as far as I'm aware, but they are geared for performance first and foremost, with economy (=range) as secondary concerns. Plus, their pilots have ejection seats.

Which one? Almost all fighter have horizontal moving fins, but what about vertical?


User currently offlineKlaus From Germany, joined Jul 2001, 21461 posts, RR: 53
Reply 49, posted (1 year 4 months 1 week 2 days 10 hours ago) and read 3335 times:

This one, among others:
http://en.wikipedia.org/wiki/North_American_A-5_Vigilante


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17039 posts, RR: 66
Reply 50, posted (1 year 4 months 1 week 2 days 3 hours ago) and read 3266 times:

Quoting Klaus (Reply 49):

This one, among others:
http://en.wikipedia.org/wiki/North_American_A-5_Vigilante

Also the Tu-160.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinecobra27 From Slovenia, joined May 2001, 1012 posts, RR: 0
Reply 51, posted (1 year 4 months 1 week 1 day 18 hours ago) and read 3212 times:

Maybe the two smaller fins instead of one big one could be easier to fold or hinge

Quoting Starlionblue (Reply 50):
Also the Tu-160.

Nope, it has fixed vertical fin


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17039 posts, RR: 66
Reply 52, posted (1 year 4 months 1 week 1 day 4 hours ago) and read 3088 times:

Quoting cobra27 (Reply 51):
Quoting Starlionblue (Reply 50):
Also the Tu-160.

Nope, it has fixed vertical fin

The fin is only fixed up to the stabilizer. Above the stabilizer, it is an all moving rudder.


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"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinerfields5421 From United States of America, joined Jul 2007, 7607 posts, RR: 31
Reply 53, posted (1 year 4 months 1 week 1 day 3 hours ago) and read 3065 times:

Quoting Starlionblue (Reply 52):
Above the stabilizer, it is an all moving rudder.

That is really interesting.


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17039 posts, RR: 66
Reply 54, posted (1 year 4 months 1 week 1 day 2 hours ago) and read 3058 times:

Quoting rfields5421 (Reply 53):
Quoting Starlionblue (Reply 52):
Above the stabilizer, it is an all moving rudder.

That is really interesting.

One of very few modern aircraft with both an all-moving elevator and an all-moving fin. In fact I can't think of any others unless you go back a few decades to the A-5 Vigilante.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinemjoelnir From Iceland, joined Feb 2013, 1449 posts, RR: 2
Reply 55, posted (1 year 4 months 4 days 6 hours ago) and read 2797 times:

Quoting Starlionblue (Reply 17):
I get the impression that Mooneys have that particular tail shape because it is distinctive.   Jokes aside, you're talking a plane that does under 200 knots. The aerodynamics change considerably one you start on the transonic speed range.

240 knots, the money M20 is a very fast plane compared to other single piston engine four seat frames.
It is thought to be a very aerodynamically efficient design.
If the straight tail fin contributes aerodynamically I do not know.


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17039 posts, RR: 66
Reply 56, posted (1 year 4 months 4 days 5 hours ago) and read 2792 times:

Quoting mjoelnir (Reply 55):
Quoting Starlionblue (Reply 17):
I get the impression that Mooneys have that particular tail shape because it is distinctive.   Jokes aside, you're talking a plane that does under 200 knots. The aerodynamics change considerably one you start on the transonic speed range.

240 knots, the money M20 is a very fast plane compared to other single piston engine four seat frames.

Wow, 240 knots. Well, you're still talking speeds at which compression is hardly a big factor.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinecobra27 From Slovenia, joined May 2001, 1012 posts, RR: 0
Reply 57, posted (1 year 4 months 3 days 12 hours ago) and read 2715 times:

Quoting mjoelnir (Reply 55):
If the straight tail fin contributes aerodynamically I do not know.

Maybe we can drop it since everbody finds it so oddI


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