Improve That Design: How Aircraft Could Have Been Made Better (Cold-War Edition)

[XBe02Drvr]

couldn't they have just changed the payload-train to an internal weapons bay or conformal storage?

If you've ever seen an RA5C fuselage in skeletal form, with all panels off and guts removed, you'd know why that kind of mod wouldn't work. There was a heavy central keel that tied tailhook, landing gear, engine mounts, and catapult hooks together. A downward drop bomb bay just wouldn't be practical in that structure.
Take a good look at that airframe. Where would you mount conformal tanks or ordnance without generating a huge drag increase or disrupting the additional lift generated by that broad airfoil shaped fuselage?
The Vige only survived combat by being a GFMF. Pre/post strike photos required "first in/loiter/last out", then wrestling the squirrelly beast back back down into the wires. Big brass ones!

 

[Zipper730]

If you've ever seen an RA5C fuselage in skeletal form, with all panels off and guts removed, you'd know why that kind of mod wouldn't work.

What I was talking about was the original design, designated NAGPAW which called for high-subsonic low-altitude penetration with the payload-train to allow maximum separation. When the requirement changed from high-subsonic low-altitude penetration to supersonic: I assume there would have been substantial design changes made. After all, you're taking a plane that was designed without supersonic performance in mind (except, maybe, in a dive) to one that would be built for supersonic performance at high altitude and subsonic penetration at low altitude. I don't know what latitude the USN would have given North American but the design probably already underwent massive changes that would effectively be tantamount to a redesign.

Further, given that the payload train was ejected during a LABS maneuver, it raises questions as to the need for the feature from the outset as well.

 

[XBe02Drvr]

What I was talking about was the original design, designated NAGPAW which called for high-subsonic low-altitude penetration with the payload-train to allow maximum separation. When the requirement changed from high-subsonic low-altitude penetration to supersonic: I assume there would have been substantial design changes made. After all, you're taking a plane that was designed without supersonic performance in mind (except, maybe, in a dive) to one that would be built for supersonic performance at high altitude and subsonic penetration at low altitude. I don't know what latitude the USN would have given North American but the design probably already underwent massive changes that would effectively be tantamount to a redesign.

Further, given that the payload train was ejected during a LABS maneuver, it raises questions as to the need for the feature from the outset as well.

You seem to be better informed on this than I, but from what I've read and I've heard from the troops that had to fly and fix the beast, the airframes were built as supersonic bombers from the get-go. The subsonic low altitude design you mention, I believe, was a "paper airplane" for which metal was never cut. Planes were rolling off the production line and flying in the fleet by the time the ordnance separation issues were acknowledged to be unsolvable. Remember this was all happening at the height of the "missile gap" and the "space race" and "nuclear paranoia", our ICBMs were still a question mark, as were the brand new Polaris submarines, and that big ol' Russian Bear was looking mighty ominous. We needed every potential nuclear delivery system to be online ASAP, so in accordance with McNamara's new "off the shelf" streamlind procurement policy, the A3J production lines started to roll long before the plane was thoroughly tested and tactics and doctrine established. When it was finally accepted that the rearward ordnance ejection system couldn't be made to work reliably, half the airframes in the initial order were on the assembly line or already flying. A complete rebuild of all those fuselages just wasn't in the cards at that point, as the perceived nuclear balance of power had shifted a little, reducing some of the delivery system urgency.

 

[Zipper730]

You seem to be better informed on this than I, but from what I've read and I've heard from the troops that had to fly and fix the beast, the airframes were built as supersonic bombers from the get-go. The subsonic low altitude design you mention, I believe, was a "paper airplane" for which metal was never cut.

NAGPAW was a paper design. However, it's the origin of the rearward ejecting payload train. It was carried over when the design switched from subsonic to supersonic.

in accordance with McNamara's new "off the shelf" streamlind procurement policy, the A3J production lines started to roll long before the plane was thoroughly tested and tactics and doctrine established.

The airplane first flew in 1958, which was during the Eisenhower administration. It entered operational service in the early 1960's.

Regardless, what I was suggesting was that between the subsonic design and the change to supersonic, one simply removed the payload train and carried the bomb in a bay. Since the design was under major change, it would be quite possible to do as it wasn't frozen.

 

[marathag]

Regardless, what I was suggesting was that between the subsonic design and the change to supersonic, one simply removed the payload train and carried the bomb in a bay. Since the design was under major change, it would be quite possible to do as it wasn't frozen.

F-105 had a bomb bay, and Supersonic from the start

with the mock-up finished in October 1953. it was pre 'area rule' and was redesigned, got the larger J75 and the YF-105A first flew two years later, but with the smaller J57 as the J75 was not yet ready

 

[XBe02Drvr]

Regardless, what I was suggesting was that between the subsonic design and the change to supersonic, one simply removed the payload train and carried the bomb in a bay. Since the design was under major change, it would be quite possible to do as it wasn't frozen.

Problem is, the unsuitability of the linear bomb bay wasn't discovered and confirmed until long after the design was frozen, metal was cut, airframes delivered, and in squadron service. For a long time there were attempted work-arounds before defeat was accepted. The central keel was a necessary part of the design, as the A3J was second only to the A3D "Whale" in takeoff and landing weights, and it's speeds were higher, giving it the highest catapult and arresting stresses of any carrier based aircraft. Weight was an issue, and any "hole in the keel" for a bomb bay would have necessitated much heavier structure to provide load paths for the stresses.

 

[XBe02Drvr]

F-105 had a bomb bay, and Supersonic from the start
View attachment 717163
with the mock-up finished in October 1953. it was pre 'area rule' and was redesigned, got the larger J75 and the YF-105A first flew two years later, but with the smaller J57 as the J75 was not yet ready

It didn't have to deal with catapults and arresting gear, and it's takeoff and landing speeds were too high for a carrier.

 

[marathag]

It didn't have to deal with catapults and arresting gear, and it's takeoff and landing speeds were too high for a carrier.

Design trade-offs. Small wings was one of the choices made.

I brought up the Thud just to point out that there was supersonic delivery via bomb bay by 1953, so that was an option in place of the NAA Tunnel setup

 

[Zipper730]

Problem is, the unsuitability of the linear bomb bay wasn't discovered and confirmed until long after the design was frozen, metal was cut, airframes delivered, and in squadron service. For a long time there were attempted work-arounds before defeat was accepted. The central keel was a necessary part of the design, as the A3J was second only to the A3D "Whale" in takeoff and landing weights, and it's speeds were higher, giving it the highest catapult and arresting stresses of any carrier based aircraft. Weight was an issue, and any "hole in the keel" for a bomb bay would have necessitated much heavier structure to provide load paths for the stresses. It didn't have to deal with catapults and arresting gear, and it's takeoff and landing speeds were too high for a carrier.

I did a little research and found something from a member of the Secret Projects forum. You might want to read.

 

[XBe02Drvr]

Design trade-offs. Small wings was one of the choices made.

For the F105, sure. The Vige's wings were massive by comparison, for aircraft of roughly comparable weights. Necessary to keep takeoff and landing speeds down to carrier compatible levels.

I brought up the Thud just to point out that there was supersonic delivery via bomb bay by 1953, so that was an option in place of the NAA Tunnel setup

In concept only. It wasn't an operational reality until 1959-60, and not truly reliable until later than that. Early Thuds had well over 100 man hours maintenance per flight hour.

 

[XBe02Drvr]

I did a little research and found something from a member of the Secret Projects forum. You might want to read.

Very interesting! I see the NAGPAW was apparently envisioned as a single seater. Given the avionics of the day, that would have been one very busy pilot. Task saturation in the low level environment tends to lead to CFIT. I like the A3J and it's terrain avoidance system, with a RAN (Radar Attack Navigator) to tend it, a lot better.
Still the fact remains that the central keel precluded a conventional bomb bay and any kind of structural work-around would have added unacceptable extra weight to an already overweight aircraft.

 

[SaparotRob]

I just like the acronyms.

 

[Zipper730]

Very interesting! I see the NAGPAW was apparently envisioned as a single seater.

Yeah, I agree a two-seater was a far better arrangement

Still the fact remains that the central keel precluded a conventional bomb bay and any kind of structural work-around would have added unacceptable extra weight to an already overweight aircraft.

From the wording described in the patent, I don't specifically see anything that indicated the arrangement was specifically to allow for effective catapulting. That said, it was stated that the arrangement made the aircraft more compact and had the potential to shave up to 150 cubic feet from the aircraft (something that would invariably cause a weight loss).

That said the aircraft did have an interesting requirement that dictated the ability to catapult while fully loaded with no WOD in order to allow for a retaliatory strike with minimum warning, eliminating the requirement to turn the carrier into the wind. While this would probably require larger loads from the catapult, the problem was also to be accomplished by enlarging the wing (North American didn't like this because it'd increase gust response for the low-altitude penetration). Shortly after this the requirement was changed to a design that required supersonic performance at altitude primarily with a secondary low-altitude capability.

 

[XBe02Drvr]

From the wording described in the patent, I don't specifically see anything that indicated the arrangement was specifically to allow for effective catapulting. That said, it was stated that the arrangement made the aircraft more compact and had the potential to shave up to 150 cubic feet from the aircraft (something that would invariably cause a weight loss).

No, it wasn't solely for effective catapulting, it was to limit aircraft weight by allowing the use of a central keel to tie all the highest stress components together in the simplest, strongest, and lightest way possible.
And all the weight loss from the keel/tunnel arrangement would have returned in spades as a weight gain if the linear bomb bay had been discarded in favor of a conventional one. This in an aircraft that was already nudging the limits of what catapults, arresting gear, and flight decks of the time could handle. Remember Forestal class supercarriers were just making their first appearance and the CV fleet consisted of Essex class and the three 27Charlies.

 

[SaparotRob]

Okay, the Vigilante is beautiful. Assuming a clean sheet design, what do you think would've been a more useful layout but looking the same? You know, scoop out the innards but leave the delicious candy coated outside.
Form follows function. Blah blah blah. Let's have fun! Hey, what could we do with the XF-90?

 

[XBe02Drvr]

Okay, the Vigilante is beautiful. Assuming a clean sheet design, what do you think would've been a more useful layout but looking the same? You know, scoop out the innards but leave the delicious candy coated outside.
Form follows function.

Hmm. Well you could start over with the same exterior appearance, but with a conventional bomb bay, and the keel along the top of the fuselage. This would require exotic metals (titanium?) to keep the weight down, a challenge with a project already looking like a probable budget buster. The classic answer to this sort of weight problem had always been magnesium, but that's way too susceptible to corrosion for a seagoing environment.

 

[Zipper730]

Well the F-8 did use magnesium, but when the XF8U-3 was designed the USN wanted all the magnesium removed.

 

[swampyankee]

In the late 1980s, the DoD wanted to get rid of magnesium on all engines. I'm not entirely sure why -- the magnesium was in large forgings or castings, which don't have the flammability issues of sheet metal -- and replacing magnesium with titanium drove weight and cost up considerably. The specific case I'm thinking of is the ALF-502, where the fan frame and compressor housing, shared with the T55, where magnesium alloy.

 

[XBe02Drvr]

Well the F-8 did use magnesium, but when the XF8U-3 was designed the USN wanted all the magnesium removed.

Corrosion control, a never-ending task at sea. Hard enough with aluminum, impossibly difficult with magnesium. Our T34 had magnesium alloy wing skins and needed constant maintenance.