Aerodynamics then and now.

[Flitzer]

I'm no expert but I've often wondered about areodynamics in respect of underwing ordinance, fuel tanks etc.


For example all through WW2 and indeed through the 50's bombs seemed to be restricted to one or two mounted underwing on fighters/fighter bombers. Main bombers always more or less carried their bombs internally. All presumably in aid of areodynamics.


With modern military aircraft it seems this is no longer as important. The number of pod, bombs, rockets, fuel tanks and missiles carried can at times make underwing areas look like an old fashioned butcher's shop. Therefore clean areo must be a problem.


Is it because most modern fighting aircraft need to be multi-role capable and often there has to be a compromise between areodynamics and what needs to be carried? Or are there other reasons?


Any thoughts


Curious P ???

 

[Steve Pace]

In the case of fighter-type stealth aircraft -
After they have eliminated all of the ground-to-air threats (AAA and SAMs) and air-to-air threats (enemy fighters), achieved total control of enemy airspace, they are free to attack strategic targets. Since they no longer need stealth, agility, high speed and maneuverability they can be loaded up with air-to-ground weapons - the more the better, to help the dedicated bombardment-type aircraft destroy an enemy's will to fight and bring about surrender.
Just my humble opinion. -SP

 

[Avimimus]

A lot of Russian and British designs had internal bomb bays into the 1960s... but then you have American aircraft like the F-84 which quickly started carrying a lot of underwing ordinance.


It might be:
Better engines (Increasing power-to-weight & power-to-drag ratios) + Increased volume of weapons (so they are harder to fit inside without reducing fuel load) + the benefit of having the option of flying with only air-to-air weapons or having a smaller volume during the return flight after releasing bombs.

But this does raise an interesting question in my mind: All of the early cold-war interceptors which had internal missile bays... Did those bays exist to shelter the delicate electronics of the missiles, or did they exist to reduce drag during an era when engines were less powerful?

 

[Flitzer]

Thanks Guys.
Still wonder even with today's super efficient/powerful engines clean aero would mean better speed/economy.
Of course to carry as much hardware as they do, internal carriage would mean much bigger aircraft. Bigger = weight, so I guess we have what we have as a kind of compromise.
Just thinking out loud really.


P

 

[sferrin]

A lot of Russian and British designs had internal bomb bays into the 1960s... but then you have American aircraft like the F-84 which quickly started carrying a lot of underwing ordinance.

Didn't realize there were any Russian ones that did. (The only British one that comes to mind is the Buccaneer. ) In the US you had the F-101, F-102, XF-103, F-105, F-106, XF-108, YF-12A, and F-111 as far as non-stealth, non-bomber aircraft with internal bays. (I guess the Vigilante sort of maybe qualifies too.)

 

[Jeb]

Thanks Guys.
Still wonder even with today's super efficient/powerful engines clean aero would mean better speed/economy.
Of course to carry as much hardware as they do, internal carriage would mean much bigger aircraft. Bigger = weight, so I guess we have what we have as a kind of compromise.
Just thinking out loud really.

Clean aero definitely means better speed and range. The F-22, for instance, can fly profiles with a full weapons load (all internal) that even the latest F-15 just can't match with the same loadout, and the F-15's carriage probably isn't that draggy.

 

[Jeb]

A lot of Russian and British designs had internal bomb bays into the 1960s... but then you have American aircraft like the F-84 which quickly started carrying a lot of underwing ordinance.

Didn't realize there were any Russian ones that did. (The only British one that comes to mind is the Buccaneer. ) In the US you had the F-101, F-102, XF-103, F-105, F-106, XF-108, YF-12A, and F-111 as far as non-stealth, non-bomber aircraft with internal bays. (I guess the Vigilante sort of maybe qualifies too.)

There was that weirdo Russian CAS bird that had individual bomb bays in the wings.

 

[Steve Pace]

The F-105 had a weapons bay but in the Vietnam War it was sealed off and used to house an extra fuel tank. -SP

 

[sferrin]

The F-105 had a weapons bay but in the Vietnam War it was sealed off and used to house an extra fuel tank. -SP

Sure, and the F-111 usually carried a fuel tank in it's bay. But they had them if they needed to use them.

 

[Steve Pace]

The F-105 had a weapons bay but in the Vietnam War it was sealed off and used to house an extra fuel tank. -SP

Sure, and the F-111 usually carried a fuel tank in it's bay. But they had them if they needed to use them.

I was talking about the F-105 as an example. What does the F-111 have to do with my statement? -SP

 

[Bill Walker]

I think a number of factors combine when we see "fashion trends" in aircraft design.

Early jets with internal bays were interested in high speed and best possible gas mileage with the early engines, so they were willing to put up with the weight penalties and maintenance headaches of internal bays. At the same time when engine design had evolved, and as operational experience showed that flat out speed was not always that important, a demand arose for larger and odd shaped external stores (early smart weapons and jamming pods for example), so there was a shift away from internal stores. Note that both the F-105 and F-111 bays were designed primarily for nukes, but neither aircraft carried them in earnest. Also note that distributing the stores along the span reduces wing structural weight, like distributing engines on the 707.

Lately we see a shift to smaller stores and an emphasis on stealth, and internal bays are making a come back. It will be interesting to see what a typical F-35 loadout looks like after a few years of operational experience.

 

[Steve Pace]

Interesting analysis. -SP