posted on Jan, 31 2006 @ 01:34 AM
And why is it related to the F-22? I was expecting an F-16 or F-18 chase plane or something, not a passenger plane next to the F-22.
Even with air to air refueling and full telemetry, an F-22 has limited persistence and the lack of 2 seaters further inhibits systems development with
separate software loads for front and back cockpits among other things. OTOH, the 757 can carry, in full security, the brassboard (Engineer Speak for
jury rigged with system components that functionally equate to the final system but often use different subsystem elements or processing/integration
sources) avionics package AND the engineering team to repair it and look at the compiled code flow. All in real time.
i.e. If you need a mini-Cray equivalent 'server' and 2-3 databus systems to separate and annotate datastreams from each sensor package before trying
to fuse the whole in a much tinier Raptor volumetric it helps immensely to be able to exploit a cabin volume in which you can essentially set
everything into avionics racks as large (and well cooled) as required.
Don't like the component functionality? Rip it out and replace.
All this can occur for hours at a time with the full functionality (radiating apertures) of the hardware in play rather than a mathematical simulant
whose GIGO factor is always questionable on a more closed-loop testbed.
And it can happen without overtaxing an already limited EMD test fleet busy with physical envelope clearance qualification (though in this case the
757 flew years before the F-22A did).
Additionally, it should be noted that, before the AF foolishly dumped the EOSS and replaced it with some kind of NCTR in the wingroots (I've heard
that is the 'left/right' receive elements for a 2D ISAR system similiar in signal exploitation function to the ALQ-128/APG-63 doppler harmonic
system on the F-15 but don't quote me.), there were also 'mail box' cheek apertures under the nose for an advanced dual-aperture IRST.
Does it involve stealth systems? What is with the wing on the top front of it?
All airframes operate within a hopefully sealed EMI environment internally which terminates at the external apertures. As such a radio frequency
compatibility map must be generated for particularly the CNI (Comms, Nav, Identificaction) suite so the mutual interference is avoided and sensitivity
confirmed. This keeps them from juking each other and allows for various airframe masking and azimuth/elevation sensitivities to fine tuned as a
function of setting software gains against RF predictor models. Again, in real time.
It should be noted that the F-22 has a LOT of further 'conformal' antennas associated with it's ALR-94 in particular and by 1:1 recreating the
various embedded striplines which have largely replaced the blade/button suites of previous generation aircraft, you get a more complete idea of their
functioning outside a sterile anechoic chamber environment. Of course this means you also have to have a fairly dense 'thicket' of live threat
emulators ready to replicate the modes and lobe behaviors of various RF threats. But we have quite a few emitter complexes that can do this at China
Lake and Nellis among others.
If stealth is involved, it more likely is relative to modeling the total system effects of an active LO system. There are those who look at the
aircraft's general configuration and compare it to the smaller F-117 signature as a function of questioning how it can achieve deep penetration
without some kind of signal loading system. E-2Cs were tracking Nighthawks at 150nm in DS (topside=hotside). But so too were British destroyers at
P.S. The F-35 team uses a similarly configured 737 and I believe the X-32 effort employed a BAC-111 systems hack. Even the X-45 employs a couple
bizjets and a T-33 surrogate. Not a big deal and actually /less/ common today than it was in bygone years wherein you might have multiple airframes
testing various systems (The A-3 Skywarrior was a particularly cross-bred lab rat but everything from C-141 to A-4s have also been employed at one
time or another...).