Navalized F-22 Raptor

[KJ_Lesnick]

I'm wondering, would it really have been all that difficult for the USN to have taken either the F-22 or F-23, and simply add some strengthening in to the undercarriage, sturdier landing-gear legs, a Naval-Aviation grade arrestor-hook, a wing-fold mechanism and a slightly larger wing to compensate for wing-loading differences?

I'm thinking about it and the F-22 and F-23 probably both were very sturdy aircraft designs, and, though I could be wrong, I wouldn't be surprised if they were structurally sturdier than the F-15 in terms of resistance to structural damage (and the F-15 was built like a tank).

The F-15 design had an airframe that in many respects was up to USN specifications.  The requirements that it be able to absorb a considerable amount of damage almost inevitably resulted in such sturdiness.  The design in addition to having good all-around visibility also had good over the nose visibility, though I was told it wasn't quite up to USN standards (Although, I'm not 100% sure, the XF8U-3 looked to have worse visibility over the nose than the F-15, though I'm not sure about that) allegedly the USN griped about the F-14's over the nose visibility and it turned out just fine in operational service. 

There was an F-15 variant that was designed as an alternative to the F-14.  Apparently, it only took 2,700 pounds of extra weight to strengthen up the under-carriage, possibly parts of the airframe, put sturdier gears in, an extendable nose-gear (like the F-4K) to increase AoA for takeoff and landings, allowing lower takeoff and landing-speeds, and a powered wing-fold mechanism.  The design may have also featured leading-edge devices (though I'm not sure about that), and as I understand it, the 2,700 pounds of extra weight may have also included strengthening to carry the AIM-54's the design was to use. 

The standard F-15A weighed around 27,000 pounds empty, weighed 38,100 pounds with a full fuel-load, 40,100 pounds with full fuel and 4 x AIM-7 Sparrows, 40,860 pounds with full fuel, 4 x AIM-7 and 4 x AIM-9 Sidewinders, 45,900 pounds with full-fuel, two external-tanks, 4 x AIM-7, 4 x AIM-9, and a maximum takeoff weight of 56,000 pounds.

With 2,700 pounds of additional weight added, the navalized variant would weigh in at 29,700 pounds empty, 40,800 pounds with a full fuel-load, 42,800 with fuel-fuel and 4 x AIM-7, 43,560 pounds with full-fuel, 4 x AIM-7 and 4 x AIM-9, 48,600 pounds with full-fuel, two external-tanks, 4 x AIM-7, 4 x AIM-9.  Maximum takeoff weight would be substantially higher as the gears would be sturdier, so I have no idea what that would work out to.

While 2,700 pounds is not exactly light, it makes up 10% of the airplane's empty weight, 7.09% of the airplane's weight with a full-fuel load, 6.73% of the plane's weight with full-fuel and 4 x AIM-7, a little under 6.61% of the plane's weight with full-fuel, 4 x AIM-7, 4 x AIM-9, and 5.88% of the plane's weight with full-fuel, 4 x AIM-7, 4 x AIM-9, and 2 external fuel-tanks.  When you factor this against the F-15A's thrust-to-weight ratio of 1.4-to-1 assuming a weight of 40,100 pounds, the 42,800 pound navalized variant would still have a T/W-Ratio of almost 1.312-to-1 which is still extremely high. 

And that doesn't take into account that the thrust figures of engines are often listed lower than they are, and the F-100 while more compact than the J-79 in length, had a pressure ratio that was 40-60% higher, it ran substantially hotter than the J-79 to the best of my knowledge, and it had a bypass-ratio which increases thrust at sea-level and continues to add thrust all the way up into the 30,000 foot-range (An engine with say 24,000 lbf at sea-level that's a turbojet will lose less thrust than a turbofan with the same pressure-ratio and sea-level thrust output as altitude increases.  The higher the bypass ratio, the greater the loss of thrust.  However if I took that 24,000 lbf turbojet, added a fan to it, it's thrust at sea level would increase and it's thrust at altitude would increase to a point as well, though not as much as at sea-level.  This of course applies to a point, as the cooler air from the fan does reduce the exhaust flow of the core for example, and there also is an issue of fan-drag, though I'm not certain at what point this becomes significant in terms of fan-area, bypass-ratio, air-speed, or mach number).  The fan, which was multi-staged, probably would provide a good duct-burning effect too.

Assuming I'm right that the F-22 and F-23 designs were both sturdier (which seems to make sense, they're designed for even more aggressive maneuvers than the F-15, both weighed a little bit more than the F-15 despite being made of lighter, stronger materials) it probably would take even less added weight to navalize an F-22 or an F-23.  The weight-difference could be partially negated with a larger wing-area to produce a similar wing-loading.  I wouldn't be surprised if they could have made a more powerful F-119 or F-120 variant (though I'm not sure how much more that would have costed) to produce a similar thrust to weight ratio. 

They both seem to have very good low-speed performance due to their leading and trailing-edge flaps and light wing-loading, so they'd probably be adequate for carrier-ops, they definitely have responsive controls, and can probably retain a good degree of directional stability and roll-control with their gears down (requirement for naval ops).  I assume they'd be able to meet USN requirements for landings (the hard part).  I am nearly certain it would meet takeoff performance requirements just fine.

The radar and sensor equipment of the F-22 is light-years ahead of the F-14 in virtually every respect.  It couldn't carry an AIM-54, but during the late 1980's there was the AAAM development which was designed to replace it.  Granted it was cancelled at the end of the Cold-War, but if the Navy was more willing to make do with the F-22 or F-23 design and navalize it, rather than demand a swing-wing design, they may have been able to use the program as justification to keep the AAAM program on.  I cannot guarantee this, but the missile as I remember it was 650 pounds, and similar in dimensions to an AMRAAM.  I don't know how much stronger the hard-point would have to be, over a standard AMRAAM hard-point though, but I remember reading about ideas to fit F-15's with them, so I assume it wouldn't be too much. 

The AAAM would have given the plane the ability to perform the fleet-defense missions the F-14's used to perform meaning the Navy would have had a complete replacement for the F-14 in the F-22 or F-23 rather than just a partial replacement in the F/A-18E/F.


So, what does everybody think?  Are my conclusions right or wrong?


Kendra Lesnick

[Hobbes]

(firmly in 'armchair general' mode here)
You make it sound so simple. Yes, 2700 lb doesn't sound too bad, and thanks to the huge thrust:weight ratio of current fighters there's plenty of margin to add some weight. But it doesn't stop there. A new wing, leading-edge devices and extendable nose gear mean that the aerodynamics change which means a rewrite of the flight control system. You also need new programming to suit carrier operations (takeoff and landing). The F-22 and F-23 use exotic coatings to provide stealth. How would these stand up to the salt-water environment? I suspect you need new coatings. Probably need to change some of the airplane parts too, to use marine-grade materials.

In an ideal world, the USN might have taken this step. RW, they are political enough not to want hand-me-downs from the Air Force and have settled for incremental development of their own aircraft.

Wrt takeoff weight, I doubt the MTOW would increase much due to the new landing gear. Gear strength isn't the limiting issue, but the amount of lift available. You can't increase takeoff speed indefinitely, you've got a max. takeoff speed that determines your max. weight.

Instead of AAAM, I'd go with a Meteor derivative. Add a booster to increase the range and you're done.

[Taiidantomcat]

Im an arm chair QB, but last i heard they still didn't exactly know how Stealth coatings on the future F-35 are going to hold up in the harsh ocean environment. just something worth thinking about. no A/C hangers on a carrier

[BlackOps]

Very interesting idea. The Raptor would look very good in Navy markings. Sounds plausible to me but I know squat about aerodynamics.

[Silver Fox]

It isn't a problem of adding naval specific gear... it's a matter of load paths.

Say you fit a new nose gear and launch bar, where do you attach it? The existing forward fuselage keel wasn't designed for distributing the stress of a cat shot. So you beef up the keel, which changes how it flexes... and changes the load path of the formers. Changing the formers changes how the skin flexes, now you have to change panel shapes and thicknesses.

Changing all that in the nose means the wiring for the black boxes is subject to different stresses, the mounts for those boxes might also need to be changed.

All those changes add weight, it's not the weight of the gear that kills you... it's the modifications to structure. Designing from scratch allows you to avoid the massive weight creep, shapes can be optimized around favourable load paths.

Rumour had it, during the ATF days, that the F-23 was designed around carrier load paths. It was said that the gear attach points were stronger, the hook position was rated for constant arrested landings and the main wing spar was built with detachable outer panels... which would allow for a fold to be installed. Considering the design team involved in the F-23... who knows?

[elmayerle]

Im an arm chair QB, but last i heard they still didn't exactly know how Stealth coatings on the future F-35 are going to hold up in the harsh ocean environment. just something worth thinking about. no A/C hangers on a carrier

*wicked chuckle* Oh, they may know more than you think.  It was a very serious study from before contact award and includes some very specific knowledge that some of the major sub-contractors has.

[KJ_Lesnick]

Assuming it's not classified, was it possible during the time of the ATF program to make stealth composites that were corrosion resistant?


Silver Fox,

Rumour had it, during the ATF days, that the F-23 was designed around carrier load paths. It was said that the gear attach points were stronger, the hook position was rated for constant arrested landings and the main wing spar was built with detachable outer panels... which would allow for a fold to be installed. Considering the design team involved in the F-23... who knows?

Can anybody else verify or refute that statement?


KJ Lesnick

[GTX]

Im an arm chair QB, but last i heard they still didn't exactly know how Stealth coatings on the future F-35 are going to hold up in the harsh ocean environment. just something worth thinking about. no A/C hangers on a carrier

*wicked chuckle* Oh, they may know more than you think.  It was a very serious study from before contact award and includes some very specific knowledge that some of the major sub-contractors has.

Oh I wonder who that would be - given that I'm working closely with them now .

Regards,

Greg

[Silver Fox]

I heard the rumour about the YF-23 from a McAir tech rep at CFB Baden, Germany. That was before the ATF decision and while NATF was still on the table. He seemed pretty confident that his team would take the prize because they were almost NATF compliant with the test vehicles.

Even if radar absorbtive surfaces weren't available for a naval environment in that timeframe, either prototype was a step up for the Navy. They may have planned to settle for some loss of stealth in the near term and use an anti-IR finish like the Hornet. When the right anti-IR/anti-radar finish is available you simply repaint the planes already in the field. 

[KJ_Lesnick]

Silver Fox,

I heard the rumour about the YF-23 from a McAir tech rep at CFB Baden, Germany. That was before the ATF decision and while NATF was still on the table. He seemed pretty confident that his team would take the prize because they were almost NATF compliant with the test vehicles.

I'm surprised they didn't win.

Even if radar absorbtive surfaces weren't available for a naval environment in that timeframe, either prototype was a step up for the Navy. They may have planned to settle for some loss of stealth in the near term and use an anti-IR finish like the Hornet. When the right anti-IR/anti-radar finish is available you simply repaint the planes already in the field.

Why didn't they just do that?  Granted, the ATF depended on stealth, but the shape of the plane itself was stealthy, the RAM surfaces would simply add to it.  It's performance was in excess of probably every plane in the USN's operational-inventory, in both speed and agility, and had state of the art avionics.  Additionally, one of the roles the ATF would have had to fulfill (Fleet-Defense) did not require stealth capability at all, just endurance, speed, excellent radar and sensors, and long-range missiles.


KJ Lesnick