Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: MK-84 on January 02, 2013, 07:20:00 PM
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In theory would putting jet engines immediately aft of a wings slipstream help to increase lift or improve airflow to an engine? Could a jet engine "suck" air across a wing?
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There are a few designs which blow the thrust across the top of the wings to increase lift:-
(http://upload.wikimedia.org/wikipedia/commons/e/e1/Antonov-An-74.jpg)
(http://upload.wikimedia.org/wikipedia/commons/8/88/Yc14-1_072.jpg)
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There are a few designs which blow the thrust across the top of the wings to increase lift:-
The problem with this design solution is that it results in a very ugly plane.
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The problem with this design solution is that it results in a very ugly plane.
^ Troof
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The problem with this design solution is that it results in a very ugly plane.
Yes. The elusive connection between form and function.
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Yes. The elusive connection between form and function.
I meant more like the connection between function and fashion. I will not dare to be seen in public holding the stick of such a plane... :P
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There are a few designs which blow the thrust across the top of the wings to increase lift:-
(http://upload.wikimedia.org/wikipedia/commons/e/e1/Antonov-An-74.jpg)
(http://upload.wikimedia.org/wikipedia/commons/8/88/Yc14-1_072.jpg)
Are you sure thats why the design choice was made?
I would think it has more to do with ground clearance working out of small narrow airfields.
Hitech
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The problem with this design solution is that it results in a very ugly plane.
:airplane: And a very high loss of wing lift! I would think this aircraft did not make production because of poor stall performance and in a "Deep Stall", undoubtedly the elevator would lose control much more quicker than a "clean" wing. Most designers want the wing to stall from the fuselage outward, where you can maintain wings level attitude, until the whole wing stops producing lift, hence you will get a aircraft with straight ahead stall feature. Some of the high performance aircraft actually had a different angle of incidence at the fuselage than at the wing tip, just to produce a straight ahead stall. Some aircraft had "stall strips" installed on the wing to force the wing to stall first in certain area's to promote a stright ahead stall. Anything on top of a wing, other than the wing surface, is going to effect the performance of the wing!
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Hitech is right that the engine placement is primarily to avoid fod from being sucked into the engines. However, on the An-72 and Boeing YC-14 the Coandă effect makes the jet exhaust "stick" to the flaps and bend down towards the ground, increasing STOL performance.
The most impressive implementation of this design was perhaps NASA's QSRA prototype, here in carrier trials: https://www.youtube.com/watch?v=k_eDutgh4IU
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Are you sure thats why the design choice was made?
I would think it has more to do with ground clearance working out of small narrow airfields.
Hitech
Yes for short field operation I thought.
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The most impressive implementation of this design was perhaps NASA's QSRA prototype, here in carrier trials: https://www.youtube.com/watch?v=k_eDutgh4IU
Nice. I've always liked this one and think it should be immediately added to Aces High and armed :old:
https://www.youtube.com/watch?v=buh7_xLG4ZE
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Having the engines at that location would most likely reduce objects from getting sucked in. Generally speaking having wing mounted engines will reduce overall plane weight. Anything mounted on the wings will act as a cantilever. After the WWII the latest craze was to mount fuel tanks near the wing tips like the P-80 for maximum cantilever effect. What the cantilever effect does is reduce the amount of weight and structural strength needed at the wing roots.
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Yes for short field operation I thought.
I would imagine its more for unprepared fields, i.e keep the engines away from the dirt and the stones and all the nasty stuff that engines dont like.
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Yes also, but the original question was about increasing lift. :old:
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Yes also, but the original question was about increasing lift. :old:
You mean this thread is not going to diverge like every other ? Dam. :rolleyes:
I stand corrected.
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Yes also, but the original question was about increasing lift. :old:
Thank you :)
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I think it's funny how some saw my much abbreviated appraisal of this design format as an opportunity to imply I am ignorant. I actually know all about the Coanda effect, I use Coanda aftershave to repel unwanted females :old:
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What? I hope you're not referring to me... :old:
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GScholz uses Rancid Polecat by Calvin Klein :old:
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I most assuredly do not! :furious
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GScholz uses Rancid Polecat by Calvin Klein :old:
:lol
(I'm glad I wasn't drinking when I read that!)
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Why put engines to wings when you can just strap them to your helmet?
And who needs wings anyway?
(http://farm1.static.flickr.com/175/483490088_0302a53719.jpg)
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I most assuredly do not! :furious
...and 'Dirty Slapper' by Lady Gaga :old:
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In theory would putting jet engines immediately aft of a wings slipstream help to increase lift or improve airflow to an engine? Could a jet engine "suck" air across a wing?
I would imagine putting the engines aft of a wing would cause a lot of turbulent air to enter the engine. Probably not going to be very nice. Plus, if mounted to the back of the wing, the elastic axis of the wing would move back (assuming its a fairly straight wing) which wouldn't be too nice for flutter either.
But as other have shown, there are planes whose engines create lift over the wing. It's news for me too! :cool:
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But as other have shown, there are planes whose engines create lift over the wing. It's news for me too! :cool:
Almost all prop planes create some lift from the slip stream of the prop.
HiTech
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I would imagine putting the engines aft of a wing would cause a lot of turbulent air to enter the engine. Probably not going to be very nice.
^this^
One of the sacrifices of pusher prop aircraft such as the long-ez and vari-ez. The prop is going to be much more efficient out front in clean air.
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^this^
One of the sacrifices of pusher prop aircraft such as the long-ez and vari-ez. The prop is going to be much more efficient out front in clean air.
Any reason they made the B-36 a pusher
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Any reason they made the B-36 a pusher
To achieve better laminar airflow for the wings.
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Any reason they made the B-36 a pusher
:airplane: The propulsion system alone made the B-36 a very unusual aircraft. All B-36s featured six 28-cylinder Pratt & Whitney R-4360 'Wasp Major' radial engines. Even though the prototype R-4360s delivered a total of 18,000 hp (13 MW), early B-36s were slow and required long takeoff runs. The situation improved with later versions delivering 3,800 hp (2.8 MW) apiece. Each engine drove an immense three-bladed propeller, 19 ft (5.8 m) in diameter, mounted in the pusher configuration. This unusual configuration prevented propeller turbulence from interfering with airflow over the wing, but also led to chronic engine-overheating due to insufficient airflow around the engines, resulting in numerous in-flight engine fires.
Another consideration which I was told back in the 50's were the unusal long, (2), two bomb bays, which could carry a 76,000 bomb payload. Because of weight and balance consideration, it had a much longer center of gravity moment arm with the engines in the rear, as opposed to engines mounted on the front of the wing. The last B-36 built was the "J" model, of which only 33 were built before the B-36 production line was closed. The wing, at the fuseledge was 7.5 feet thick and crew members could, if neccessary, actually do some light repairs while in flight, although, I was told, this was never a common practice. This was one of the GREAT bombers produced by the U.S. during the 40' and 50's.
For more info: http://en.wikipedia.org/wiki/Convair_B-36#Design
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Any reason they made the B-36 a pusher
You mean like a guy in a hoodie standing outside of the school gate?
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Almost all prop planes create some lift from the slip stream of the prop.
HiTech
Hah, how could I have overlooked that. Although I guess downwash only on one wing would be a disadvantage as we know from the stall and trim characteristics of these prop planes (excluding contra-rotating prop planes).
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So in theory can a jet's intake "pull" turbulent air over the wings, making it flow better? Or at any realistic speed it no longer provides a suction force?
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So in theory can a jet's intake "pull" turbulent air over the wings, making it flow better? Or at any realistic speed it no longer provides a suction force?
It does not work exactly this way. Continuity must be kept, this is why a turbulence is created along the trailing edge of the wing. If you suck the air from above the wing, what will come in its place? The answer will really depend on the fine details, but most likely, you will end up with more drag and a less efficient engine.