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Zanimljiva analiza (izgleda od Karla Kopa jos iz 1991godine)
Citat:
Author's Commentary Added to 1991 sci.military Internet Newsgroup Posting
Topic:
Why did the USAF make the decision it did and select the Lockheed and Pratt's designs in preference to the Northrop and GE designs ?
The decision criteria for selection were pretty broad and covered performance and ability to meet the design spec, ability to meet manufacturer's internal spec, price, life-cycle-cost and development risk. The USAF have stated that the criterion of industrial base was not important, but informed sources advise me that this was not entirely true and that the USAF looked at the issue very seriously.
On the strength of what has been published about both aircraft and engines, the US taxpayer would have gotten an excellent deal in terms of system performance with either aircraft, they are both top performers. The final comparison appears as such:
1.Performance
Both aircraft apparently met the USAF's performance specs. Northrop were a bit faster, longer ranging and stealthier, whereas Lockheed were a bit more manoeuvrable. It appears that the performance margins between both types were not dramatic.
The GE engine performed somewhat better in the trials than the P&W engine, but the final P&W proposal included an enlarged fan and hence higher thrust for production aircraft, presumably equalising the difference.
2.Price
Apparently Lockheed and P&W were cheaper, by how much does not appear to have been published anywhere (anybody know ?)
3.Development Risk
Northrop were penalised in a number of areas. Firstly Lockheed did more aggressive flying (played their politics right by doing it very visibly) during the dem/val program and demoed high AoA manoeuvres and missile launches well in excess of nominal dem/val requirements.
Secondly Lockheed built a very conservative airframe design with very conservative materials, ie an F-15/F-18ish almost hybrid planform geometry using a lot of aluminium and titanium alloys, unlike Northrop who opted for cca 50% empty weight in composites, using a very stealthy airframe geometry, never used before in a fighter.
Thirdly Lockheed did not suffer the development pain which Northrop did with their stealthy exhaust ducts. The lining of the YF-23 exhausts is a laminated alloy structure full of tiny cooling holes fed by engine bleed air. It was apparently rather heavy and may have required major design changes to bring it to production. Also the main weapon bays of the YF-23 apparently stacked the Amraams vertically and the USAF were unhappy about the potential for jams in the launcher mechanism preventing the firing of subsequent missiles.
Northrop, true to their tradition, created a showpiece of the state of the art in technology - ie a high performance truly all aspect stealth airframe with better speed/range performance and bigger weapon bays than its rival. The price of innovation was the loss of the contract, as the YF-23 combines a lot of new ideas which have never been used before. Whereas the Lockheed F-22 is clearly an evolutionary development of current aerodynamic/stealth technology, the Northrop YF-23 is very much revolutionary. Therefore risky.
Similarly, the P&W engine was conservative, whereas the GE engine was a radical variable bypass ratio design never used in production before.
4.Industrial Base
MDC and Northrop have ongoing commitments for the C-17, F/A-18 and B-2 respectively, whereas Lockheed and GD don't really have any real military projects left once the P-3 and F-16 are completely closed. Similarly GE will be building F110s and F404s for F-16 and F-18 production to the end of the decade, whereas P&W only have the F100 for which the biggest user, the USAF F-15 force, is unlikely to seek additional purchases.
Therefore, a decision to buy Northrop/GE could have seen both Lockheed and P&W end up shutting down their military airframe/engine businesses around the end of the decade.
Summary
The US taxpayer is getting the cheaper and more predictable product with some penalty in top end performance and long term performance growth potential.
The USAF however had NO choice in this matter as the Administration killed the A-12 Avenger in January due cost overruns resulting from high risk R&D. By killing off the radical but high performance A-12, the Administration set a clear precedent. The A-12 was considered a very secure project politically because its cancellation would mess up Navy deployment plans for the next decade (the A-6Es are very old, basic airframe design 1958) and cause all sorts of problems.
In comparison with the A-12, the ATF was considered politically expendable as it is seen (incorrectly in my opinion) as a dedicated killer of PVO/VVS aircraft, while the F-15s will remain viable for at least another decade.
As a result, the USAF had no choice than to pursue the lowest risk design options regardless of any other criteria. As it turns out, both Lockheed and P&W were desperate enough to submit lower bids and hence the decision could not have really gone the other way. If the USAF chose the F-23 and it got into difficulties say in 1994 due R&D problems, it would almost certainly die the death of the A-12. Politicians generally seem to have little respect for air warfare strategy.
As for the future of the F-23, it may not end up being adopted by the Navy simply because the Navy is having real money problems, ie. buying F-18s instead of its preferred F-14s. Therefore the Navy is unlikely to buy any Naval ATFs until the end of the decade, by which time the Lockheed product will have matured whereas the Northrop one will have been sitting on the shelf.
Alternative roles for the airframe could be theatre strike and reconnaisance, but it is basically too good an airframe for these jobs and hence cheaper options could be found.
Final Observation: politics is always a stronger decision criterion than technology or air warfare strategy.
http://www.combatsim.com/review.php?id=45&page=2
Inace u kasnijem tekstu (koji sam postavio iznad) Karlo Kop se ispravio po pitanju agilnosti YF-23. YF-23 iako nije imao vektorski potisak je bio vrlo agilna letelica, sto je i logicno ako se pogleda smesno opterecenje krila (268kg/m2) 1.36 odnos potiska i mase (sa 10tona goriva) i specifican dizajn vertikalaca.
Ne treba zaboraviti da je Nortrop planirao da malo izmeni F-23 tj. da ga produzi za dodatno spremiste (za dva AIM-9M), sto bas nije za pohvalu jer jedan avion je poslat na ocenjivanje da malo drugaciji su planirali da naprave.
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