Forum: General F-22A Raptor forum

checksixx wrote:

Heat tiles?? Behind the YF's engine's? I don't think that had anything to do with it as the rest of the aircraft had no 'tiles'.

The tiles behind the engines were more than enough problem. And the issue wasn't production of the tiles but maintenance of them. Just like the shuttle, every time they were allowed to cool down and contract, as well as every so often just due to wear and tear, someone had to go inside the exhaust tunnels and inspect every single tile for damage, loosening, and gaps. The tiles were not there for show; they were there to keep the hot engine exhaust from destroying the plane. If an inspection found anything wrong with even one tile, they had to repair it -- cool everything down to room temp, remove the bad tile without damaging any of the other tiles around it, remove the adhesive residue, replace the tile(s) without damaging the new ones or any of the other tiles around it, and wait for the new adhesive to set -- taking the plane out of commission for hours if not days. Plus look at a good picture of the tiles. Can you imagine the logistics nightmare of having to keep all those different shapes in stock, in adequate numbers for the replacement rate of that particular tile, at every single base that flies YF-23s?

While it was an astounding prototype (I remain a YF-23 fan and lament that it ultimately lost to the YF-22), it was not a combat capable aircraft as long as it relied on those tiles. The tiles were an affordable stopgap measure to get a flyable YF-23 prototype into the air (a prototype having long downtimes between flights anyway), but they were not intended to be the production heat shields for the exhaust tunnels. Northrop-Grumman promised a more durable replacement for the tiles if the plane went into production. But they couldn't afford to develop such a replacement unless the plane went into production. Unknown development problems and costs of a durable, relatively maintenance-free heat shield of the size required for those exhaust tunnels was one of the uncertainties that made the YF-23 lose to the YF-22. I think it's almost universally conceded the YF-23 was the better plane. Economically, though, the F-22 has proven itself to be more than good enough against any potential threat, at a lower cost point than even the most ardent YF-23 fans could claim for the better plane. It was the better program to meet the minimum needed objectives at the lower cost; that's why it won.

I'm also very skeptical of claims that the YF-23 would've been a mini-SR-71. Just like the F-22, the thermal and mechanical limits of its materials (especially the stealth coatings of its day) would've kept it hard-limited well under Mach 2.5 regardless of any aerodynamic/propulsion limits allowing it to go faster. Aerodynamically, an F-22 can probably do Mach 3 on the F-119 engines if the nacelles were properly shaped for it; it has an apparently better thrust to drag ratio in the supersonic regime than the SR-71 as it is now. But that would break a lot of other things far more critical than some 1950s concept of the importance of raw speed. Same with the unbuilt F-23.

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sprstdlyscottsmn wrote:

F-22 has 2 ailerons, 2 flaps, 2 rudders, 2 stabilators, and technically 4 TVC paddles. 12 control surfaces.
YF-23 has 2 ailerons, 2 flaps, and 2 ruddevator stabs. 6 control surfaces.

Not to nitpick, but...

The F-22's "flaps" are actually flaperons. And I think the other posters are counting the forward slats as surfaces (on both planes).

Also, I'd count the F-22's TVC as effectively a single pair of pitching surfaces. So for me the tally would be YF-23=8 and F-22=12 (incl. the TVC "pair").

(And yes, supacruze's site is awesome.)

At 1:18 you can see the tiles, they are actually perferated.
http://www.youtube.com/user/strykerxo?f ... 9-n3tNrec0

On inspection of the wing it sounded pretty solid, does anyone know if the wing was wetted or solid?

Don't know about the YF-23, but the F-23A drawing shows wet wings, Tanks 4 & 5.

em745 wrote:

sprstdlyscottsmn wrote:

F-22 has 2 ailerons, 2 flaps, 2 rudders, 2 stabilators, and technically 4 TVC paddles. 12 control surfaces.
YF-23 has 2 ailerons, 2 flaps, and 2 ruddevator stabs. 6 control surfaces.

Not to nitpick, but...

The F-22's "flaps" are actually flaperons. And I think the other posters are counting the forward slats as surfaces (on both planes).

Also, I'd count the F-22's TVC as effectively a single pair of pitching surfaces. So for me the tally would be YF-23=8 and F-22=12 (incl. the TVC "pair").

(And yes, supacruze's site is awesome.)

Forgot about LEF, and yes if I was using terms like stabilators and reddevators I should have said flaperons as well. Thank you.

From what I've heard, the military chose the F-22 because it had better maneuverability.

There were other reasons too. They were mainly political though and the technical reasons may have been simply due to the YF-23 being a more complex and exotic design that would have been more expensive to develop and mass produce by Northrop. The YF-23 had heat tiles to insulate the engine exhaust and those might have been quite expensive to build and maintain. The YF-23 was an incredible aircraft though. From VLO design to raw straightline speed and high altitude performance there was no comparison; the YF-23 was beyond comparison.

I wouldn't say "political" so much as contractual. It has been stated both planes met or exceeded all requirements. If the contract wasn't set up to weight the margin by which each aircraft exceeded the requirements, a YF-22 just a hair north of meeting those requirements would beat a YF-23 that surpassed all requirements by a country mile, merely by the YF-22 being quoted a penny cheaper. Presumably, the contract was set to request a plane that gave us what was needed. The requirements were evidently already set with a margin of error: nothing even comes close to the F-22 as it is. Giving us more than that wasn't useful, so why should we have to pay anything more than the cheaper YF-22 proposal's price? The cheaper plane is already more than we needed.

pbever wrote:

From what I've heard, the military chose the F-22 because it had better maneuverability.

In the flight regime occupied by an air superiority fighter, the YF-23 had better maneuverability than the YF-22. The YF-22 was only more maneuverable at low airshow speeds, and supposedly in its maximum instantaneous rate of turn. Otherwise the YF-23 was better the whole competition.

I had heard it was documentation. Northrop supposedly did not document how to build the titanium forward bulkhead, so therefore they had no proof that they could, 2 flying examples notwithstanding.

This threads current direction has got me thinking, how many different (conspiracy)theories are there as to why the YF-22/F119 was chosen??

sprstdlyscottsmn wrote:

I had heard it was documentation. Northrop supposedly did not document how to build the titanium forward bulkhead, so therefore they had no proof that they could, 2 flying examples notwithstanding.

I think it's not so much proof they could build it, but proof they had a specific method planned to produce serial examples of it on an assembly line at a predictable cost. Like not having a production replacement for the heat tiles planned out, the possibility of having to hand-build each curvy forward section, like they did for the prototypes, was one of the unknowns that contributed to the YF-23's rated higher cost. (And I think it's obvious its more complex structure would have cost more than the YF-22, even mass produced.) But the government loves its paperwork, and I'm sure every single lack of a documented SOP for how to produce certain parts added to the calculated cost disproportionately to even the reality of those costs.

New F-23 info just released. See details here: [Link pending approval]#!/yf23net

Cool!

supacruze wrote:

New F-23 info just released. See details here: twitter.com/#!/yf23net

Anyone with (as compared to mine) real aerospace knowledge have an opinion on the drawings of the F-23 NATF version? Would it have been effective at least as far as flying characteristics?

I see the F-22 win purely as a function of meeting the ATF requirements at a more favorable pricepoint/lower risk design. The YF-23a's airframe was and still is revolutionary. As such though, it dictated greater developmental/production risk and associated higher cost(s). IF the stealth/supercruise and other performance parameters were THAT much better, it's likely that technology survived - somewhere.

The production F-22 far exceeds the prototype though, IMO and is a fine aircraft. The fact it's known to supercruise above Mach 1.7 is incredible - that's half a mach faster than the prototype established, if memory serves. One can only imagine how fast the production F-23 would have been...
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Forum: General F-22A Raptor forum

YF-22 vs YF-23