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How About An Engine In The Wing For Airplanes?  
User currently offlinePanais From Cyprus, joined May 2008, 468 posts, RR: 0
Posted (5 years 10 months 2 weeks 4 days 12 hours ago) and read 7261 times:

Crazy idea, not sure if I can validate it.

How about a commercial airliner with the engines in the wing.

Not hanging from the wing but being part of the wing. This will greatly reduce drag and therefore, make the plane faster and more fuel efficient.

This new concept plane is not a flying wing like the Blended-Wing-Body. Instead it is like a B737/A320 or B777/A330 with the engine inside the wing like the Vulcan for example.
http://news.bbc.co.uk/2/shared/spl/h.../sci_nat_enl_1157113941/html/1.stm

Because of size the airplane can have 2 or 4 or 6 engines.

Any comments?

51 replies: All unread, showing first 25:
 
User currently offlineJgarrido From Guam, joined Mar 2007, 340 posts, RR: 0
Reply 1, posted (5 years 10 months 2 weeks 4 days 11 hours ago) and read 7219 times:

you mean like the De Havilland Comet?


View Large View Medium
Click here for bigger photo!

Photo © Peter De Jong



User currently offlinePanais From Cyprus, joined May 2008, 468 posts, RR: 0
Reply 2, posted (5 years 10 months 2 weeks 4 days 10 hours ago) and read 7198 times:

Yes, something like the Comet.

I would expect that the engines will be as further away as possible from the cabin.

Thanks for the picture.


User currently offline113312 From United States of America, joined Apr 2005, 574 posts, RR: 1
Reply 3, posted (5 years 10 months 2 weeks 4 days 10 hours ago) and read 7197 times:

The reason Boeing and Douglas designed their earliest turbojet planes with engines in pods were:
Get the engines away from the fuel tanks.
Isolate each engine from the other in case of fire or disintegration.
Isolate the engines from the wing structure for above reasons.
Facilitate maintenance and engine change.
Minimize the airflow disturbance on the wing.


User currently offlineFLY2HMO From , joined Dec 1969, posts, RR:
Reply 4, posted (5 years 10 months 2 weeks 4 days 10 hours ago) and read 7189 times:



Quoting Panais (Thread starter):
B737/A320 or B777/A330

I don't think even a small CFM (compared to the GE90) would be feasible, or any other HBP turbofan for that matter. The fan's diameter is just too large. And I'd presume having an engine pod/shroud conformed into the wing would be quite heavier with engines like these than the standard engine mountings used today. Not to mention engine removal for MX would be a pain, but I guess a rail(?) system like many fighters have, where the engines just slide in and out, could be feasible.

Quoting Panais (Reply 2):
Yes, something like the Comet.

Considering how tiny those turbojets are, then yeah, they could pull it off. But there are very very few planes that ever had this configuration.


User currently offlineMoose135 From United States of America, joined Oct 2004, 2379 posts, RR: 10
Reply 5, posted (5 years 10 months 2 weeks 4 days 10 hours ago) and read 7189 times:

With high-bypass turbofans, this concept isn't very feasible. You would need a *large* intake opening and "tunnel" through the wing, much larger than the Comet shown above, and that wouldn't work very well. Also, it makes the wing structure much more complex, adding weight to allow sufficient strength around the engines. Also, in the event of an engine fire, I think the last place you want the engine is buried in the wing, where the fire could more easily spread to fuel, electrical, hydraulics and other systems.

I have some friends who once worked for Grumman, and we were talking about the E-2 Hawkeye recently. There is a "hole" through the wing spar structure for the engine to pass through, and one of the struggles they had with trying to upgrade the engines was the diameter of the engine - Allison proposed a more powerful engine, but it had a larger diameter turbine, and Grumman wouldn't redesign the wing structure to accommodate the larger opening needed.



KC-135 - Passing gas and taking names!
User currently offlineKELPkid From United States of America, joined Nov 2005, 6428 posts, RR: 3
Reply 6, posted (5 years 10 months 2 weeks 4 days 8 hours ago) and read 7116 times:



Quoting Panais (Reply 2):
I would expect that the engines will be as further away as possible from the cabin.

The reason engines tend to be placed as close to the centerline of the aircraft as possible is to reduce the roll/yaw moment caused by an engine out situation, and keep Vmc (the minimum control airspeed with a single engine inoperative) within reason. If the pilot allows the aircraft's speed to fall below Vmc while climbing with an engine out, the plane will roll over onto it's back  Wow!



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineSEPilot From United States of America, joined Dec 2006, 7012 posts, RR: 46
Reply 7, posted (5 years 10 months 2 weeks 4 days 7 hours ago) and read 7071 times:

The Comet was designed by engineers still used to piston engines, and buried the engines in the wings because that was similar to the way prop engines were mounted, at least in terms of the location of thrust vectors. But as 113312 points out, Boeing and Douglas found that there were decided advantages to pod mounting (Boeing actually developed the pod design for the B-47, and found that it had almost no aerodynamic penalty, as well as the functional advantages described.) Once turbofan engines came on the scene with their larger diameters, the structural problems of burying them have made any thought of burying them in the wing a total non-starter. This has also led to the death of tri-jet, as the larger the engine the more problems encountered in trying to mount one in the tail. Remember that the more complicated a structure, the heavier it will be, and having to go around a large engine greatly complicates any structure.


The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offline474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9
Reply 8, posted (5 years 10 months 2 weeks 4 days 6 hours ago) and read 7008 times:



Quoting KELPkid (Reply 6):
The reason engines tend to be placed as close to the centerline of the aircraft as possible is to reduce the roll/yaw moment caused by an engine out situation, and keep Vmc (the minimum control airspeed with a single engine inoperative) within reason. If the pilot allows the aircraft's speed to fall below Vmc while climbing with an engine out, the plane will roll over onto it's back

If you have an effective rudder system the engines can be place further outboard on the wings, providing the paying passenger with a quieter flight. A perfect example is the DC-10 and the L-1011.


User currently offlineMD-90 From United States of America, joined Jan 2000, 8508 posts, RR: 12
Reply 9, posted (5 years 10 months 2 weeks 4 days 1 hour ago) and read 6907 times:



Quoting SEPilot (Reply 7):
(Boeing actually developed the pod design for the B-47, and found that it had almost no aerodynamic penalty, as well as the functional advantages described.)

Well, credit does need to be given to the Germans. I believe they were the ones to discover that mounting engines in pods was the best way to go and Boeing got their hands on some of that data after WWII ended.


User currently onlineStarlionblue From Greenland, joined Feb 2004, 17108 posts, RR: 66
Reply 10, posted (5 years 10 months 2 weeks 3 days 23 hours ago) and read 6879 times:



Quoting 113312 (Reply 3):
Get the engines away from the fuel tanks.
Isolate each engine from the other in case of fire or disintegration.
Isolate the engines from the wing structure for above reasons.
Facilitate maintenance and engine change.
Minimize the airflow disturbance on the wing.

AFAIK yet another reason is that engines slung forward alleviate wing twist. The wing tends to twist "back" and the weight of the engines counteracts the tendency.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineKELPkid From United States of America, joined Nov 2005, 6428 posts, RR: 3
Reply 11, posted (5 years 10 months 2 weeks 3 days 23 hours ago) and read 6864 times:



Quoting 474218 (Reply 8):


If you have an effective rudder system the engines can be place further outboard on the wings, providing the paying passenger with a quieter flight. A perfect example is the DC-10 and the L-1011.

Well, the DC-10 and and L-1011 were also trijets, not twins, which meant that losing a wing engine wasn't as big of a deal as losing one engine in a twin. The tail engine is also providing thrust, so the roll tendency isn't as great as it would be in, say, a 777-200LR  Wink [where you know that, should you lose an engine on takeoff, the other engine will be instantly cranked up to an insane 115,000 lbs. of thrust!]

I did get a few opportunties to fly on DC10-10s, thanks to AA, who used to use them on intra-Texas routes  Smile I remember it being a really cool experience, but I don't remember "quiet" being part of that experience (and come to think of it, I don't think "quiet" really descibed any McDonnell Douglas product particularly well  Wink ). The first plane that I recall really being blown away by how quiet it was was the 767...

I never did get to try the DC-10's competition, the L-1011, much as I wanted to...  Sad (and a crying shame that is!  crying  )



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 12, posted (5 years 10 months 2 weeks 3 days 22 hours ago) and read 6831 times:



Quoting Panais (Thread starter):
Not hanging from the wing but being part of the wing. This will greatly reduce drag and therefore, make the plane faster and more fuel efficient.

I think it's pretty unlikely to reduce drag. Although the wetted area will go down, the weight is almost guaranteed to go up because now you need to carry wing bending loads around the engine (check out the banjo fitting on a DC-10 to see how ugly that can get). Also, with a modern high-bypass turbofan, the engine diameter is so large relative to wing thickness (especially if you stick it far outboard) that you've basically added two more fuselages (from the aerodynamic point of view). Wing-fuselage aerodynamics is among the toughest to optimize and it causes a bunch of problems...putting the engines in the wings makes this three times as bad.

If you can truly bury the engine in the fuselage, like fighters and UAV's do, then you can ditch most of these problems. However, for obvious reasons, you can't do that on a commercial jet.

Tom.


User currently offlineHAWK21M From India, joined Jan 2001, 31702 posts, RR: 56
Reply 13, posted (5 years 10 months 2 weeks 3 days 21 hours ago) and read 6818 times:

The Comet was what came to mind almost instantly.
Talking about the comet.how was the dry bay around the engines ensured?
regds
MEL.



Think of the brighter side!
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 14, posted (5 years 10 months 2 weeks 3 days 20 hours ago) and read 6791 times:



Quoting HAWK21M (Reply 13):
Talking about the comet.how was the dry bay around the engines ensured?

I'm not positive, but I'd assume they didn't start the fuel tank until outboard of the engines.

Tom.


User currently offlineDw747400 From United States of America, joined Aug 2001, 1264 posts, RR: 1
Reply 15, posted (5 years 10 months 2 weeks 3 days 19 hours ago) and read 6767 times:



Quoting KELPkid (Reply 11):

Well, the DC-10 and and L-1011 were also trijets, not twins, which meant that losing a wing engine wasn't as big of a deal as losing one engine in a twin.

Moving the engines outboard also provides structural benefits. Even in a twin, engineers will tend to move the engines outboard to maximize wing bending relief--they are just more restrained than in three and four engined jets.

If you talk to an engineer who worked on the L1011, they will point out that the wing engines are further outboard, providing a more efficient wing structure when compared to the DC-10. The -10, with its tail mounted engine, has less rudder area, and thus less rudder authority, than the L1011 with its buried engine. Some Lockheed guys are REALLY proud of this!



CFI--Certfied Freakin Idiot
User currently offlineAlessandro From , joined Dec 1969, posts, RR:
Reply 16, posted (5 years 10 months 2 weeks 3 days 18 hours ago) and read 6744 times:



Quoting MD-90 (Reply 9):
Well, credit does need to be given to the Germans. I believe they were the ones to discover that mounting engines in pods was the best way to go and Boeing got their hands on some of that data after WWII ended.

Even better, Boeing got hold of German designers whom contributed a lot to the B707.
It seem a bit old fashion, Tu-104 and Tu-124 also had this design.


User currently offlineDocLightning From United States of America, joined Nov 2005, 20194 posts, RR: 59
Reply 17, posted (5 years 10 months 2 weeks 3 days 16 hours ago) and read 6720 times:



Quoting 113312 (Reply 3):
The reason Boeing and Douglas designed their earliest turbojet planes with engines in pods were:
Get the engines away from the fuel tanks.
Isolate each engine from the other in case of fire or disintegration.
Isolate the engines from the wing structure for above reasons.
Facilitate maintenance and engine change.
Minimize the airflow disturbance on the wing.

And Area Rule. Putting engines out in front decreases the sudden cross-section change of the wing area.


User currently offlineAlessandro From , joined Dec 1969, posts, RR:
Reply 18, posted (5 years 10 months 2 weeks 3 days 16 hours ago) and read 6713 times:

Yes, many advantages of the current design, one of the few advantages I can see is less risk for FOD with things from the ground sucked into the engine when it´s higher up.

User currently offlineHAWK21M From India, joined Jan 2001, 31702 posts, RR: 56
Reply 19, posted (5 years 10 months 2 weeks 3 days 16 hours ago) and read 6706 times:



Quoting Tdscanuck (Reply 14):
I'm not positive, but I'd assume they didn't start the fuel tank until outboard of the engines.

If true.Structurally that would a huge load outboard.
regds
MEL



Think of the brighter side!
User currently offlineJambrain From United Kingdom, joined Sep 2008, 251 posts, RR: 0
Reply 20, posted (5 years 10 months 2 weeks 3 days 7 hours ago) and read 6546 times:

Some of the blended wing designs have engines at least partially in wing e.g.
http://www.aoe.vt.edu/research/groups/bwb/
To get the airflow to achieve high propulsive efficiency (it is more efficient to accelerate a large mass of air less) you would need a set of fans driven by gears otherwise the fan diameter would be too large.

see this paper for an overview of performance:-
http://www.grida.no/publications/oth...src=/Climate/ipcc/aviation/094.htm

this paper gives some idea of the improvement in propulsive efficiency that comes from ‘filling in the wake’ with an engine in the wing
http://www.aoe.vt.edu/research/groups/bwb/presentations/ATIO-Nov03.pdf



Jambrain
User currently offlineSEPilot From United States of America, joined Dec 2006, 7012 posts, RR: 46
Reply 21, posted (5 years 10 months 2 weeks 3 days 7 hours ago) and read 6526 times:



Quoting HAWK21M (Reply 19):

If true.Structurally that would a huge load outboard.

That is actually an advantage; the more you can distribute the load over the wingspan the easier it is on the wing spars.

Quoting Alessandro (Reply 16):

Quoting MD-90 (Reply 9):
Well, credit does need to be given to the Germans. I believe they were the ones to discover that mounting engines in pods was the best way to go and Boeing got their hands on some of that data after WWII ended.

Even better, Boeing got hold of German designers whom contributed a lot to the B707.
It seem a bit old fashion, Tu-104 and Tu-124 also had this design.

What is your authority on this? I have read "The Road to the 707" by William Cook, who was one of the engineers on the project; he says nothing about any German engineers. And the Boeing design was quite different from the German design; the Germans had the engine tight against the wing (like the 732, which might have been influenced by the Germans) but the B-47 was suspended away from and in front of the wing, which was done to provide sufficient airflow between the engine and under the wing to avoid an increase in drag. This is something the Germans had not done. The idea of sweeping the wing was gotten from the Germans, as well as a lot of the jet engine technology, but I never heard that the podded engine ever was.



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offlineScooter01 From Norway, joined Nov 2006, 1207 posts, RR: 8
Reply 22, posted (5 years 10 months 2 weeks 3 days 2 hours ago) and read 6454 times:
Support Airliners.net - become a First Class Member!



Quoting SEPilot (Reply 21):
Quoting MD-90 (Reply 9):
Well, credit does need to be given to the Germans. I believe they were the ones to discover that mounting engines in pods was the best way to go and Boeing got their hands on some of that data after WWII ended.

Even better, Boeing got hold of German designers whom contributed a lot to the B707.
It seem a bit old fashion, Tu-104 and Tu-124 also had this design.

What is your authority on this? I have read "The Road to the 707" by William Cook, who was one of the engineers on the project; he says nothing about any German engineers. And the Boeing design was quite different from the German design; the Germans had the engine tight against the wing (like the 732, which might have been influenced by the Germans) but the B-47 was suspended away from and in front of the wing, which was done to provide sufficient airflow between the engine and under the wing to avoid an increase in drag. This is something the Germans had not done. The idea of sweeping the wing was gotten from the Germans, as well as a lot of the jet engine technology, but I never heard that the podded engine ever was.

I believe MD-90 is onto something there. As we know, some of the German engineers went to the Soviet Union, where Bruno Baade was in the design-team that developed the Alexeev 150 bomber:
http://www.aviastar.org/air/russia/alekseev_150.php

and after that he and some other engineers returned to East Germany and came up with this design:
http://www.aviastar.org/air/ddr/veb_152.php

Not that any of these aircraft became any successes, they had other problems that plagued them, but one can clearly see where the podded engines and the bicycle type undercarriage came from.

About engines buried in the wings, I cannot help thinking about the Avro Canada Jetliner:
http://www.avroarrow.org/Jetliner/JetlinerIntro.html

How quickly we forget...

Scooter01



"We all have a girl and her name is nostalgia" - Hemingway
User currently offlineBsergonomics From United Kingdom, joined Jan 2002, 462 posts, RR: 0
Reply 23, posted (5 years 10 months 2 weeks 3 days 1 hour ago) and read 6444 times:

The wing-bending argument is irrelevant in the current age of material sciences. However, as Boeing found out (by accident) very early on, if you mount the engines further outboard and under the wing (the former is the important bit rather than the latter), it prevents wing flutter at higher Mach numbers.

So, (ignoring for the moment the arguments about risk assessments, maintenence, fuel capacity, etc.) if you want to mount an engine inside the wing, the big pay-off will be if you mount it in the middle of the wing, rather than close to the fuselage.

The Comet was a world-leader that was killed by its windows, not by the airframe, nor by the engines. However, there is a good lesson to be learned from the Comet - don't mount your engines next to each other. If one lets go, it's liable to take the other one with it.

Enjoy!



The definition of a 'Pessimist': an Optimist with experience...
User currently offlineAlessandro From , joined Dec 1969, posts, RR:
Reply 24, posted (5 years 10 months 2 weeks 3 days 1 hour ago) and read 6431 times:



Quoting SEPilot (Reply 21):
What is your authority on this? I have read "The Road to the 707" by William Cook, who was one of the engineers on the project; he says nothing about any German engineers. And the Boeing design was quite different from the German design; the Germans had the engine tight against the wing (like the 732, which might have been influenced by the Germans) but the B-47 was suspended away from and in front of the wing, which was done to provide sufficient airflow between the engine and under the wing to avoid an increase in drag. This is something the Germans had not done. The idea of sweeping the wing was gotten from the Germans, as well as a lot of the jet engine technology, but I never heard that the podded engine ever was.

This book, http://www.stenvalls.com/shop/Stenva...ages/shop/1840373113_Boeing707.jpg


25 OldAeroGuy : In the end though, the Comet configuration was a dead end design. What commercial airplane uses it today? The B-47 configuration lives on in every Ai
26 Post contains links Dw747400 : I'm not an expert on materials, but I don't see how the basic rule that reducing loads allows a smaller, lighter structure changing. It may shift on
27 Post contains links OldAeroGuy : I believe that 14,400 lb is total thrust rather than thrust per engine. See this reference for the Derwent V: http://www.absoluteastronomy.com/topics
28 Dw747400 : Thanks, makes much more sense! I'm used to specs listing thrust per engine... should have read a bit closer. By the way OAG, do you have any thoughts
29 OldAeroGuy : I don't understand the following comment. Perhaps Bsergonomics will explain in more detail.
30 HAWK21M : Considering the Weight of the Engines & the fuel on the outboard side,The wing root attachments would need to cater to a lot of weight. Understandabl
31 Tdscanuck : It's still a big deal. If it wasn't, both Airbus and Boeing wouldn't be spending oodles of R&D on active load alleviation as a weight saving measure.
32 Bsergonomics : The comment about wing bending is being taken out of context. Firstly, wing bending is important, but not paramount. The amount of wing flex on the A3
33 SEPilot : I don't understand your point. My point is that any weight that is carried directly by the wing is not transferred through the wing root attachments.
34 Tdscanuck : I don't believe this is right. Although having the engines outboard will increase the wing root moment when you're parked on the ground, I'd be reall
35 SEPilot : I would argue this. I know that Boeing has constantly played with all kinds of configurations, and I strongly suspect that all of the other manufactu
36 Starlionblue : I agree with Tdscanuck in challenging this. The wing tends to bend over backwards and wing twist is actually counteracted by slinging the engines for
37 HAWK21M : The load on the wing root would be much more for a longer span wing & fitted with Engines too,add the outboard distribution of fuel load. true there
38 Alessandro : No they didn´t, the engine pod designs for the A300 was bought from McDonnell-Douglas. Sure the Il-62 and Vic-10 later had 4 engines stacked in the
39 SEPilot : Wrong. The wing distributes lift over its span; any weight that gets distributed over the span is lifted directly, almost like a balloon. That weight
40 Moriarty : Just a note: Concorde... among others. The Concorde crash was a result of a chain of events, one of them was the fact that the engines are/was close t
41 VC10 : You can possibly enlighten me on accidents were both engines have failed due to being along side each other, but I cannot think of any at the moment,
42 Dw747400 : Remember, "wing bending relief" is not the same thing as wing flex. Its all about balancing the loads in an optimum fashion, regardless of how the wi
43 Tdscanuck : This isn't exactly true. Although SEPilot is right that the wing is holding itself up, so the wing weight isn't transferred through the wing/fuselage
44 Post contains links Viscount724 : It didn't involve an accident, but an LX Avro RJ100 had an uncontained failure on an AMS-ZRH flight in 2004 which resulted in some damage to the adja
45 Alessandro : I didn´t say that!
46 VC10 : " target=_blank>http://aviation-safety.net/database/...809-0 Thanks for the information, which is another example to show that engines on pylons are
47 SEPilot : You're right, I oversimplified. But weight added on the outer parts of the wing span reduces the moment on the wing root, especially if it would othe
48 Tdscanuck : Absolutely agreed. This is also why airliners burn center fuel first, to keep fuel weight outboard in the wings as long as possible. Tom.
49 HAWK21M : any notes available? regds MEL.
50 SEPilot : I don't have any notes, but perhaps I can explain it better. Consider a flying wing built like a balloon, with just skin and no spars (which would re
51 HAWK21M : Thanks for trying to explain.Appreciate it. Was considering dynamic loading as well & long term stress on the Wing root over time. regdds MEL.
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