F-18 Super Hornet pylon angling

[Hummingbird]

Does anyone know the reason behind the crazy decision to angle the SH's wing pylons outwards?

 

 

I can only imagine the enormous amount of extra drag this is causing, and this instead of simply re-designing the pylons, positioning or fuel tanks? :doh:

[Kuky]

Most likely to reduce air drag (at particular speed), air doesn't flow parallel to aircraft, as it hits the nose and rest of the fuselage parts, it changes direction and creates high pressure pushing out air more distanst from the aircaft also... but then this creates lowe pressure further down along the aircraft frame... making the air suck in closer... so basically air curves in and out around the airframe, and at that part where the fueltanks are attached, is most likely where air travels towards the airframe, so they angle fueltank to follow this air stream.

[NoJoe]

I'd always wondered this too, and some reading on Google suggests it may have been due to weapons separation issues and clearance from the fuselage, or possibly with bomb accuracy. Is there any truth in that? I really can't find much info on it other than "it's apparently due to ...".

 

Whatever the reason, it's just another example that everything in aircraft design is about compromise, and optimizing the configuration for a specific mission. If the canted pylons actually increase drag, then that's a trade-off the designers chose. On the other hand if it decreases drag, then it's a trade-off between performance and how cool the plane looks. ;)

Edited April 6, 2015 by NoJoe

[Kuky]

Well yeah, could be other reason(s) other than to reduce drag, only way to know for sure is to ask the manufacturer. :)

[Tirak]

Weapon clearance. The Super Bug crams two more pylons onto the wing over the Legacy Hornet, in order to meet weapon clearance requirements for safe release, they had to be canted away from the aircraft. This has the lovely benefit of having six semi deployed airbreaks at all times, if you were using all of them, which hurts range and speed, something the plane doesn't have a whole hell of a lot of to begin with.

[mvsgas]

Not sure if this is related, to be honest this is way above my head and beyong my comprehensions.

Direct PDF link

UNSTEADY SUBSONIC AERODYNAMICS FOR MANEUVERING WTNG/FUSELAGE/PYLON/STORE.

CONFIGURATION AND STORE SEPARATION INCLUDING WAKE EFFECTS

[mvsgas]

looking for info on the weapons pylons I found an interesting pdf

direct link to download the pdf

operational lessons learn on the F-18E

[26-J39]

IIRC the C variant had issues with the pylons/payload oscillating at certain speeds causing excessive fatigue.

[Hummingbird]

Most likely to reduce air drag (at particular speed), air doesn't flow parallel to aircraft, as it hits the nose and rest of the fuselage parts, it changes direction and creates high pressure pushing out air more distanst from the aircaft also... but then this creates lowe pressure further down along the aircraft frame... making the air suck in closer... so basically air curves in and out around the airframe, and at that part where the fueltanks are attached, is most likely where air travels towards the airframe, so they angle fueltank to follow this air stream.

 

I really doubt that is the case, esp. seeing as no other aircraft has adopted such a thing. Also you'll note that it isn't just the fuel tank pylons that are angled, no its ALL of them:

 

Edited April 6, 2015 by Hummingbird

[Hummingbird]

Weapon clearance. The Super Bug crams two more pylons onto the wing over the Legacy Hornet, in order to meet weapon clearance requirements for safe release, they had to be canted away from the aircraft. This has the lovely benefit of having six semi deployed airbreaks at all times, if you were using all of them, which hurts range and speed, something the plane doesn't have a whole hell of a lot of to begin with.

 

Yeah, I hope they come up with some fix for this later because those angled pylons must hurt performance quite a bit.

 

There must be a better solution to achieve the necessary clearance other than having to angle the pylons. Just seems like a really lazy ass solution, and probably one dictated by some politician -_-

[Tirak]

Yeah, I hope they come up with some fix for this later because those angled pylons must hurt performance quite a bit.

 

There must be a better solution to achieve the necessary clearance other than having to angle the pylons. Just seems like a really lazy ass solution, and probably one dictated by some politician -_-

 

There really isn't another solution for several reasons. Firstly, without the cant, the inner pylons are useless for deployable ordinance, so you get a station only capable of holding TGPs or EFTs, which defeats the purpose of adding in the additional pylons. You can't move the pylon outboard without redesigning the whole wing to be more structurally sound. You can't only can't the inner pylons to clear the fuselage without then interfering with the other pylons on the wing. It's one of a host of problems the Super Hornet has that makes it a pretty crappy plane.

[SkateZilla]

There are other AC other thab the SB woth angled pylons.

 

There isnt a "fix" this is a perm. Angle of all production SBs, you cant "patch" it

 

The Inner Pylons were canted 3-4° to resolve fuselage clearance and a few other issues, the rest were angled because the inner.ones were angled.

[Hummingbird]

I find it quite amazing that such a thing wasnt tested early on so that the wing could've been redesigned BEFORE it went into production :doh:

[mvsgas]

I don't think is that big of a deal. Of course they tested it, I'm sure it was the best solution when considering design cost, weight, structure, etc, etc. We don't even know the exact reason for the pylons angle.

[Tirak]

I find it quite amazing that such a thing wasnt tested early on so that the wing could've been redesigned BEFORE it went into production :doh:

The wing was completely redesigned, several times. Granted, mostly to address cracking because it's too thin but initial prototypes didn't have the cant, but they found they couldn't safely release weapons. And since the Super Hornet had to carry more than the Hornet, they couldn't very well say "Oh well it can carry more, it's just that the inner pylons are for fuel tanks you can't jettison, so you're buying a bigger, more expensive, slower, less maneuverable aircraft, but you'll get more range because we can haul more bags, but carry about the same amount of weaponry." So they went back in, canted them out so all the pylons could be used as weapon stations. The huge joke of course being, that barring an actual conventional war, the inner pylons are only going to be used for fuel tanks anyway, and no pilot is going to dump them without having to explain to their CO why they just dumped that much cash, and that's if they've still got enough range to get back to the ship.

[Hummingbird]

So now they have to deal with extra drag and reduced service lift of attachment points, not to mention that apparently the missiles are now being subjected to constant forces they weren't designed for and as such are wearing out as well.

 

What a fiasco...

[Hummingbird]

Found this: https://ericpalmer.wordpress.com/2009/01/16/the-super-hornet-stores-story/

 

I think this quote from one of the engineers is rather telling:

"The major conclusion is that store separation problems should be analyzed as early as possible in the aircraft design, and not analyzed after the design is completed."

 

:doh:

Edited April 7, 2015 by Hummingbird

[Kuky]

So now they have to deal with extra drag and reduced service lift of attachment points, not to mention that apparently the missiles are now being subjected to constant forces they weren't designed for and as such are wearing out as well.

 

What a fiasco...

 

What do you mean by "missiles are now being subjected to constant forces they weren't designed for"? You saying missiles are not designer to widthstand a few G's? :doh:

 

At the end of the day, if this was such a huge problem that you make it out to be surely people that design aircraft (professionals) wouldn't have done it. :music_whistling: You don't think they weigh the pro's and cons of each setup, design and what not?

Edited April 7, 2015 by Kuky

[Hummingbird]

What do you mean by "missiles are now being subjected to constant forces they weren't designed for"? You saying missiles are not designer to widthstand a few G's? :doh:

 

Sure they are, I'm not talking about G's, I'm talking about constant vibrations and torsional forces on the attachment points. If you'd have cared to read the link I provided you would've known it isn't something I just pulled out the wazzoo either :doh:

 

At the end of the day, if this was such a huge problem that you make it out to be surely people that design aircraft (professionals) wouldn't have done it. :music_whistling: You don't think they weigh the pro's and cons of each setup, design and what not?

 

Ah so you're saying that there are no other factors involved here? Such as cost maybe? :music_whistling:

 

Blind faith is never a good thing.

[Hummingbird]

Either way a solution seems to be on the way:

[Kuky]

Of course cost is ALWAYS a factor, if not everyone would be making new airframes instead of "reusing" them :) Well time of development of new airframes is a factor also... politics is factor also (how much is wanted to spend on weapons etc, what are they needed for, what to expect in future... many many things). So rotating few pylons a few degrees is maybe least of their "worries".

[Tirak]

Either way a solution seems to be on the way:

 

Yeah because a bunch of little airbrakes wasn't dumb enough, let's but a really big one on the bottom, call it a stealth pod while putting it on a non stealth aircraft. Genius.

[Gladman]

A real bunch of armchair airframe engineers in this thread :)

 

Wow!

[Hummingbird]

Yeah because a bunch of little airbrakes wasn't dumb enough, let's but a really big one on the bottom, call it a stealth pod while putting it on a non stealth aircraft. Genius.

 

Actually it should decrease the signature quite abit. Remember that the aircraft was designed with stealth in mind from the beginning, hence the new rectangular intake design over the rounded ones on the legacy hornet.

 

Also it wont act as an airbrake or cause any significant drag increase, it being centered and not in any way canted, thus only causing about as much drag as a regular centerline tank would.

 

Infact this arrangement will remove a lot of drag as the ordinance is now hidden away, and all the drag that would've otherwise been present from the pylons on the wings is gone. The extra fuel is then intead carried in low drag conformal fuel tanks on top of the fuselage which, because of their shape, in theory should also increase lift.

Edited April 7, 2015 by Hummingbird

[Hummingbird]

Of course cost is ALWAYS a factor, if not everyone would be making new airframes instead of "reusing" them :) Well time of development of new airframes is a factor also... politics is factor also (how much is wanted to spend on weapons etc, what are they needed for, what to expect in future... many many things). So rotating few pylons a few degrees is maybe least of their "worries".

 

It was simply the only solution left if they didn't want a further increase in cost and delays because of the stupid decision not to test out seperation behavior BEFORE they finished the design of the aircraft.

 

As one of the engineers said, it was a planning failure, pure and simple - one the USN & USMC will have to live with until the government decides to pour money at a redesign, which isn't likely to happen considering how much of a money hog the F-35 has turned out to be.

 

Good thing they still have the legacy hornets and that they're in the process of being upgraded.