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WEAPONS AND EQUIPMENT, Japan
Date Posted: 01-Mar-1997
International Defense Review
THE PROGRESS OF THE F22 FIGHTERPROGRAM
TEXT: Late in May, Lockheed Martin test pilot Paul Metz is due
to take the F22A fighter up on itsmaiden flight from Dobbins Air
Force Base, Georgia, next to Lockheed Martin's Marietta plant.
Itwill be a longawaited milestone in what has become the US Air
Force's (USAF's) most importantprogram of the 1990s, and possibly
one of the most significant programs in its history. ThePentagon is
currently preparing the Quadrennial Defense Review (QDR), the
secondterm followon to the 1993 bottomup review of US military
plans. The 1993 review cut the planned number ofF22s from 648 to
442: there is a risk that the QDR will further reduce this.
Congress fears a`tactical aircraft trainwreck': a situation in
which increasing expenditures on the F22, the USNavy's (USN's)
F/A18E/F and the Joint Strike Fighter (JSF) reach a point where it
is impossible toretain all three programs. The F22 is the most
prominent of these programs and the mosttempting target for
budgettrimmers. Annual cuts imposed by Congress and the Pentagon
havealready delayed the program and increased its costs. Further
cuts will be more expensive in thelong run, while building fewer
aircraft at a lower rate will increase its unit costs. The
USAF'sdefense of the F22 is farreaching and fundamental. In the
latest revision of its postSovietdoctrine, air and space
superiority is listed as the primary USAF `core competency'. Air
and spacesuperiority is intended to provide US forces with freedom
of action, while preventing hostileaircraft and missiles from
interfering with US operations and denying them sanctuaries where
theycan operate. "Too many people fail to understand how the
country depends on air dominance,"Air Combat Command chief Gen
Richard Hawley remarked at an Air Force Association symposiumin
Orlando in January. "How long will information from Rivet Joint and
Joint STARS be available ifthose aircraft are threatened by
longrange AAMs [airtoair missiles] launched from
sanctuariesprotected by surfacetoair missiles [SAMs]? Will we be
able to sustain precision attack operationsagainst adversary
fighters? Will ground forces be able to maneuver as they did in
Operation`Desert Storm' if the enemy's reconnaissance aircraft can
see them?" The USAF's case is that airsupremacy is an unstated
prerequisite for US military operations. Consider that the US
Armyspends relatively little on its own air defense, mainly using
SAMs to defend fixed targets or to dealwith `leaker' aircraft. The
USN's air defenses are designed for bluewater operations. Joint
forcesrely on force multipliers such as the Airborne Warning and
Control System (AWACS) and JointSTARS, carried on vulnerable
transports. To put it bluntly: what did more for the ground forces
in
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the 199091 Gulf War the USAF's control of the air, or USN
deepattack missions? F15s haveshot down 96 adversaries with zero
losses in air combat. However, the USAF argues that a morelethal
and survivable replacement is needed to counter the proliferation
of advanced fighters andSAM systems. Two factors support the need
for a fighter which outclasses the threat, rather thanmatching it
(as an improved F15 could). First, US and allied forces intheater
are likely to beoutnumbered in the early stages of a conflict, as
they arrive and establish their bases. Second, theUS public and
political leaders expect quick success and minimal losses. A
balanced assessment ofthe F22's capabilities and the status of the
program suggests that it should win the approval ofthe QDR and
Congress. However, as Hawley said: "If the facts are allowed to
speak, the outcomewill not be in doubt. At this juncture, I'm not
sure that will happen." While Hawley remarked thatmany people do
not understand the F22's mission, however, he could also have added
that fewpeople understand its capabilities either. The F22
represents the greatest one generationadvance in fighteraircraft
capability in 50 years. It brings about the greatest increase in
sustainedspeed since the advent of the jet, flying most of its
missions at speeds that other fighters attainonly in short sprints,
and accelerating and maneuvering at speeds where today's fighters
areworking hard to fly in a straight line. It will equal and
probably surpass the agility of any otherfighter, including the
Su35. It embodies allaspect, widebandwidth radiofrequency (RF)
andinfrared (IR) stealth. Its integrated avionics and sensorfused
displays are a generation in advanceof anything known to be under
test elsewhere. The F22's basic shape was devised in three
hecticmonths in 1987, after Lockheed decided that the design with
which it had won a place in theUSAF's demonstration/validation
(dem/val) program was both technically and
competitivelyunacceptable. The fundamental challenge was to
reconcile the demands of stealth, supersoniccruise and agility.
Stealth influences the shape and angle of all external surfaces,
and requires thatall weapons and fuel be carried internally,
demanding an airframe of much greater volume than anequivalent
nonstealthy design. Supersonic cruise requires low supersonic drag,
which usuallyimplies slenderness and thin wing and tail sections,
which are not inherently compatible with largevolume. Agility is
achieved through a large wing span and area and effective controls:
this is hardto reconcile either with the need for a small, thin
wing for supercruise, or with the fact that thebest tail for a
stealth aircraft is no tail at all. The initial goal was a fighter
with a 22.5tonne cleantakeoff weight, but that proved impossible,
and the F22 tips the scales at 27 tonnes. In generallayout, the F22
is a moderately swept (42) delta of a kind that has not been seen
since theJavelin and Skyray of the 1950s: little of the F22's mass
lies behind the line of the trailing edge.The wing and body are
highly blended onethird of the total wingspan lies between the
wingattachment points making room for the weapons bays and much of
the fuel. The delta wingcombines ample volume and a low
thickness/chord ratio for supersonic drag with enough area tomeet
maneuverability requirements, and still fits in standard NATO
aircraft shelters. It isstructurally efficient and stiff. At high g
loadings, the ailerons deflect upwards to offload thethinner outer
sections. The wing is more sophisticated than it looks; large
leadingedge flaps andcomplex camber make it more efficient at low
speed and high alpha (angle of attack) than earlierdeltas. The F22
was designed to reach extreme angles of attack while remaining
under full
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control: the objective was `carefree abandon' handling, allowing
the pilot to exploit a very largealpha/airspeed envelope without
overstressing the aircraft or causing it to depart from
controlledflight. Another goal was to avoid stability and control
deficiencies that would require limits on theangle of attack. The
F22 is designed to be immune from deep stalls and to recover from
highalpha, poststall conditions with both engines flamed out.
According to test pilot Metz, the first F22A will fly with a set of
flight control system (FCS) laws that address the full flight
envelope andall configurations. Although testing will be
incremental (as always), the prototype YF22 and windtunnel
experience suggests that no major changes will be necessary. Thrust
vectoring is not usedto expand the envelope. At low airspeeds,
vectored thrust gets the F22 from one maneuver stateto another more
quickly, but the aircraft is controllable in any part of the
envelope without it andcan always recover with a failed engine. The
same benefits could have been achieved withconventional controls,
but it would have meant increasing the size of the tails by 30 per
cent andadding 180kg to the empty weight. Given that the
twodimensional (2D) nozzles were needed tomeet stealth
requirements, thrust vectoring added only 1322kg to the aircraft.
The nozzles vectoronly in pitch, but they make the F22 more nimble
in roll because, with the vectoring systemoperational, the
horizontal tails can be exploited more fully for roll control. The
fourtailconfiguration was selected because it provides adequate
stability and linear control response inpitch, roll and yaw over a
wide speed and alpha range. The verticals are located well forward,
sothat even at high alpha they are not blanketed by vortices from
the body, and stability and ruddereffectiveness are retained. The
horizontal tails are carried on booms projecting aft of the
nozzles,and their root leadingedges fit into cutouts in the
flaperons. The FCS runs the horizontal tails,the rudders, the
vectoring nozzles, the wing surfaces (flaperons, ailerons and
leadingedge flaps)and even the nosewheel steering. There are no
speedbrakes: for inflight deceleration, theflaperons go down, the
ailerons deflect up and the rudders move outwards. On the ground,
theentire trailing edge deflects up to spoil the wing lift. Almost
17,000h of wind tunnel testing wereperformed during the engineering
and manufacturing development program, involving 23 modelsin 15
facilities. The basic program was completed in mid1995, but a
further 900h of work on GBU32 and AIM9X weapons (see below) release
will be completed this year. No significant changeshave been made
as a result of tunnel tests. The F22's stealth design clearly
evolved from that ofthe F117, with a preponderance of flat, canted
surfaces and a sharp chine line from the nose tothe wingtips.
Better modeling and testing techniques have allowed the designers
to incorporatesome curvature in the surfaces. In the nowfamiliar
manner, surfaces and edges are aligned withone another; large
openings such as the landing gear and weapon bay doors have
serrated edges,aligned with the wing and tail edges; and small
apertures are diamond or rhombusshaped. Gapsbetween control
surfaces are delicately sculpted to avoid 90 angles as they move.
The object isto concentrate radar reflections in a small number of
lobes, using preflight and onboard missionplanning software to
minimize the time during which any lobe `dwells' on a known or
detected RFthreat. A basic difference between the F117 and the F22
is that radar absorbent material (RAM)is not applied to the entire
aircraft, but selectively to edges, cavities and surface
discontinuities.
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Lockheed Martin builds all the edges of the aircraft, which
probably consist of wideband radarabsorbent structures.
Heatresistant ceramicmatrix RAM is likely to be used on the
exhaustnozzles. The radome is a `bandpass' type which reflects
signals at all frequencies except theprecise wavelengths used by
the F22 radar. Radar crosssection (RCS) problems were
discoveredduring early fullscale model tests. There was no single
reason for the failure to meet thespecification: rather, the
problem was traced to the difficulty of maintaining tolerances in a
largenumber of apertures and serrations. The result was a detailed
redesign of the surface of theaircraft. Access panels and drain
holes were eliminated or combined, and some serrated edgeswere
modified with fewer, larger teeth. Recent tests of a modified RCS
pole model have indicatedthat the problem is solved. The F22
structure includes less composite material than the
designersplanned, but the weight goal 25 per cent lighter than an
allaluminum airframe was achievedthrough the selective use of
highstrength, highstiffness composites and the largescale use
oftitanium, which makes up 41 per cent of the airframe weight.
Composites account for only 25 percent, mostly in the wings and
tails where their stiffness is valuable. The heart of the structure
isthe midbody section, built by Lockheed Martin Tactical Aircraft
Systems in Fort Worth. Itincorporates the four weapon bays, the
main landing gears and the complex inlet ducts (seepicture on
left). The midbody accomodates much of the fuel. Apart from the
discrete bays for themissiles, landing gear, gun and environment
control system, the midbody is plumbed and sealedas set of integral
fuel tanks. An onboard inert gas generating system produces
nitrogen, which ispumped into the tanks to reduce the risk of
explosion from battle damage. The midbody alsoaccommodates much of
the fuel. Apart from discrete bays for the missiles, landing gear,
gun andenvironmental control system, the midbody is plumbed and
sealed as a set of integral fuel tanks.Nitrogen produced by an
onboard inert gas generating system is pumped into the tanks to
reducethe risk of explosion from battle damage. Attached to the
midbody are the forebody,accommodating the cockpit and avionics,
which is built by Lockheed Martin in Marietta; and thewings, aft
fuselage, engine bay and the tailbooms, built by Boeing. Five
massive titaniumbulkheads in the midbody absorb most of the
structural loads. The largest measures just under4m between the
wing attachment points and 1.8m from top to bottom, and is produced
as theworld's largest titanium forging by WymanGordon, weighing
2,975kg. Some 95 per cent of itsmass is removed during machining,
leaving a 149kg finished part. The widest of the forgingsmeasures
4.62m from tip to tip. The midbody and rear fuselage include some
unusual structuralfeatures. The inlet lip and the fittings that
support the wing and rudder are hot isostatic process(HIP)
castings, made from titanium alloy powder formed under very high
pressure. HIP wasoriginally developed for disks in engines, but is
used to form highly loaded, rigid, complexshapedcomponents with a
minimum parts count. The tailbooms are electronbeam welded
titanium: theaft fuselage is 67 per cent titanium because of high
temperatures. Carbonfiber/bismaleimide (BMI)composite is the
primary material in the wings. BMI replaced the thermoplasticmatrix
compositeused in the YF22 because it was stronger and less
expensive. Thermoplastics had previously beentougher and more
damagetolerant than BMI, but improved BMI resins became available
during
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dem/val. Thermoplastics tolerate higher temperatures than BMI,
so the change to BMI in the EMDaircraft meant a reduction in
maximum Mach number, from 2.0 to 1.8. The wings incorporate
sinewave spars in which the web is an undulating curve produced by
a resintransfer moulding(RTM) process developed by Boeing and
Dow/United Technologies. In the RTM process, drycarbonfiber fabric
is laid up in a mould and BMI resin is injected at high pressure.
RTM providesbetter yields and lower costs for relatively small,
complex parts. One in four of the spars is stillmade from titanium,
a change made after livefire damagetolerance tests. Alliant
TechSystemsprovides two of the largest carbonfiber/epoxy components
on the aircraft: the 2.8m horizontal tailpivot shafts. The
tapewound shaft is up to 490 plies thick and blends from a long
cylinder (on theaircraft side) to a flattened, sweptback spar
buried in the tail. A few thermoplasticmatrixcomposites are still
used the largest components are the landing gear and weaponbay
doors,where damage tolerance is important. Weight has been an
issue, but Lockheed Martin disputesthat it has been out of control
and says the projected empty mass is now lower than it was in1994.
There is no weight specification for the F22: the requirement is
written in terms ofperformance. As a result, some weight growth has
been accepted at the expense of small changesin performance. The
totally frameless Sierracin canopy is unique. Most canopy
specificationsrequire nearperfect optics only in the forward field
of view, but the F22 will have a helmetmounted sight and therefore
needs `zone 1 quality' throughout. The F22 canopy is made fromtwo
9.5mm sheets of polycarbonate, sandwiched between two sheets of
optical glass, fusionbonded in an autoclave, and drapeformed over a
canopy blank at 400C. Birdstrike protectionremains an issue. The
F22 canopy is not as inherently tough as the multilayer F16
canopy.Although the F22 canopy can withstand a 450kt birdstrike,
the impact initiates a wave throughthe canopy which, at its lowest
point, strikes the headup display (HUD) combiner, sendingfragments
into the pilot's face. HUD supplier GEC Avionics is working with
Lockheed Martin ondesigns for a collapsible combiner. The size and
cycle of the F22's Pratt & Whitney F119PW100engines was driven
by the supercruise requirement. Although the F119 is similar in
size to theF100, with a roughly similar airflow (about 125kg/s), it
has a very different cycle. The F119'sbypass ratio is 0.2:1 or
less, versus 0.7:1 for the F100, so its core handles at least 50
per centmore air. Although the thrust of the F119 is officially
quoted as `in the 155kN class', informationobtained by IDR suggests
that the actual thrust may be more than 170kN with full
augmentor,implying an intermediate (non augmented) rating of 113kN.
This is compatible with statementsthat at supersonic speed, on dry
thrust, the F119 generates twice as much power as the F100PW200.
The F119 has not been shown in public, but General Electric has
exhibited the rival F120 inpartly disassembled form, mounted
alongside an F110 the difference in the size of the coreblading was
considerable. These are huge engines, capable of delivering 180kN
withoutafterburning when fitted with a larger fan for the Boeing
JSF design. The F119 has completed aformal qualification program at
the USAF's Arnold Engine Development Center (AEDC) inTennessee, and
initial flight release has been obtained. By late January, the
first two flighttestengines had been delivered to Marietta, and
preparations were being made for engine runs.Results have been
good, says program manager Walt Bylciw, and the engine's early
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developmental troubles (which necessitated an extensive redesign
of the turbine and some otherfinetuning) are behind it. The F119
has a threestage fan, a sixstage compressor and singlestage low and
highpressure turbines. Each has fewer blades than an F100 stage, so
in all theF119 has 40 per cent fewer aerofoils. The counterrotating
shafts eliminate a stator between theturbine stages, saving weight,
reducing the engine's length and cutting the requirement forcooling
air. Integrally bladed disks are used throughout the fan and
compressor; the hollow firststage blades are made separately and
joined to the disk by linear friction welding, a technique inwhich
the blade is rubbed so hard against the disk that it bonds to it.
Early in the design process,Pratt & Whitney engineers joined
operational USAF F15 maintainers on the flightline. As a result,the
designers selected a small set of wrenches, ratchets and sockets
and built the engine so thatall exterior maintenance could be
carried out with those tools, and restricted themselves to a
fewtypes of clips and fasteners. Virtually all the engine's
plumbing is accessible without removing theengine itself, and all
lines are colorcoded. The F22 inlets are fixedgeometry, one of many
waysin which the USAF's decision to forgo a highMach capability
(seldom used on the F15) savedtime, weight and money. Boundarylayer
turbulence is controlled by drawing air through pores inthe duct
wall, and the air is dumped overboard through exhaust grills and a
bleed door. Each inletduct has a larger bypass door just ahead of
the compressor face, which can open during rapiddeceleration. The
philosophy of the design is that no doors are open except during
maneuvers orengine transients. The vectoring nozzles can divert the
full augmented thrust 20 upwards ordownwards in a second.
Twodimensional nozzles are necessary for stealth in both the RF and
IRbands: the edges of a 2D nozzle can be aligned with the other
edges of the aircraft, and its shapetends to flatten the exhaust
plume and promote mixing with the ambient air. In a
twinengineaircraft, too, a 2D nozzle helps to provide a smooth,
lowdrag aftbody shape. The nozzles arelargely made of burnresistant
Alloy C titanium and incorporate a sophisticated internal
coolingsystem. The F22's main armament comprises six AIM120C
Advanced MediumRange AirtoAirMissiles (AMRAAMs). Three missiles are
carried in each of the ventral bays, which are covered bybifold
doors. The AIM120C was designed for internal carriage on the F22,
with clipped wing andtail surfaces. Its performance is virtually
identical to earlier AMRAAMs and it will be the standardversion for
all USAF fighters. The AIM120s will be propelled from the weapon
bays bypneumatic/hydraulic AMRAAM Vertical Ejector Launcher units.
The side bays will each hold oneGMHughes AIM9X Sidewinder, carried
on the AIM9 Trapeze Launcher (ATL), a mechanicallyextending rail
incorporating an exhaust plume deflector. The ATL will be extended
automaticallyas the F22 nears the point of achieving launch
parameters on the target, allowing the IR seekerto lock on before
launch. A General Dynamics M61A2 20mm cannon, a lighter version of
the M61with longer, compositewrapped barrels and a redesigned
breech, is mounted above the rightwing root. The muzzle opens on to
a shallow trench in the fuselage, covered by a sidehingeddoor. The
F22 carries 480 rounds of ammunition in a linear feed system aft of
the weapon bays.In 1994, the USAF asked Lockheed to develop an
airtosurface capability for the F22, and thelower weapon bays have
been modified to accommodate the 450kg McDonnell Douglas GBU32
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Joint Direct Attack Munition (JDAM). The F22 can carry two each
of JDAMs, AMRAAMs and AIM9s. JDAM is guided by a GPS/inertial
system, with a specified circular error probable (CEP) of
13m.Development of a programmable seeker to provide a 3m CEP,
equivalent to a laserguided bomb,is due to start in 2002. A
synthetic aperture radar (SAR) mode is being added to the F22's
radarfor airtosurface operations. Other weapons have been studied
for the F22, but not funded. Theaircraft could carry a pair of Wind
Corrected Munitions Dispenser (WCMD) weapons for useagainst area
targets. A compact version of the HARM missile is under study for
the F22. New andmuch smaller weapons are developed for production
early next century and are particularlyattractive for the F22.
Examples include an operational derivative of the Miniaturized
MunitionsTechnology small hardtarget weapon, eight of which would
fit inside the F22, and the LowCostAutonomous Attack System, a
miniature cruise missile capable of detecting, identifying
anddestroying military vehicles. When stealth is not critical, the
F22 can carry up to 2,270kg ofexternal stores on each of four
underwing pylons. For ferry flights, each of these canaccommodate a
600gallon (2,270liter) fuel tank and a pair of AMRAAMs, reducing
the need fortanker and cargo support. However, none of the F22's
attributes could be exploited properlywithout the fighter's least
visible element: its avionics system. It is revolutionary, in part
becauseit has to be. The F22 brings new complexities to the fighter
mission. The air battle will unfoldmuch more quickly in front of
the pilot, because of the fighter's greater speed. The F22 relies
onits stealth for protection against hostile air defenses, but
stealth can be compromised by emissionsfrom its own systems.
Stealth gives the pilot a new set of variables to consider; the F22
is morestealthy against some radars than others, and its RCS
changes according to the radar's bearing.Stealth imposes
limitations on sensor design and operation. "I have to minimize
power, and buryall my apertures," said avionics team leader Marty
Broadwell. "If I don't do it this way [that is, theintegrated and
fused approach used on the F22], I can't see anything." Metz looks
at the problemfrom a slightly different angle: "If you look at
history, very few fighter pilots are effective," hesaid. In the
Second World War, only 21 per cent of fighter pilots made kills and
about one in six ofthese (3.6 per cent of the total) became aces.
During the 195053 Korean War, the 4.8 per cent ofpilots who became
aces made 38 per cent of the total kills. "What if we can increase
the ratio ofpilots who make kills from one in five to one in two,
or three?" said Metz. The implications interms of force
effectiveness are clear. Metz outlined three principles in the F22
design which areintended to accomplish that goal. One of these is
to eliminate `housekeeping' tasks throughautomation and selftest.
Launching the F22 is a matter of inserting a Data Transfer
Modulecartridge which sets up the displays according to the pilot's
preferences switching the batteryon, holding the auxiliary power
switch in the on/start position and setting the throttles to idle.
Theengines start automatically and the avionics run through their
diagnostic routines, and within aclassified but extremely short
time the fighter is ready to go. The second principle is the
`carefreeabandon' flying qualities which relieve the pilot from
worrying about the flight envelope or possibledeparture. The third
principle, and the driving force behind much of the avionics
design, is to`maximize information and minimize data'. The F22's
sensors and displays meet this challenge in
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three basic, interrelated ways: sensor fusion. Combining data
from all different sensors to displayone target on the screen and
relieving the pilot of the need to monitor and compare
differentdisplays; sensor management. In normal operation, the
pilot does not control the sensors. This isdone automatically
according to the tactical situation; and emission control (EMCON).
One of thetasks of the sensor management system is to keep
electronic emissions at the lowest possiblelevel. The F22 cockpit
is dominated by four large activematrix liquid crystal display
screens.There are no dedicated backup instruments: these are hosted
on smaller monochrome LCDpanels. The GEC holographic HUD is
designed so that the bulk of the optical system is locatedbehind
the panel, allowing the central 203mm{2} Tactical Situation Display
(TSD) to be movedupward and making room for three 152x152mm screens
left, right and below. The architecturebehind the displays is
revolutionary. In the traditional sense, the F22 has no radar,
electronicwarfare (EW) system, or communications, navigation and
identification (CNI) systems. Instead,like the displays, they are
peripherals serving the fighter's GMHughes Common
IntegratedProcessor (CIP), which consists of two banks of 32bit
liquidcooled computer modules housed inthe forward fuselage. The
entire system runs on 1.7 million lines of code hosted by the
CIP.Fiberoptic highspeed databuses link the sensors to the CIPs and
the CIPs to the displays. Apractice sortie in Lockheed's concept
demonstrator a mediumfidelity, securityapprovedsimulator shows how
the system works from the pilot's viewpoint. The pilot's main
sources ofinformation in the beyondvisualrange fight are the TSD
and the screens on either side: the leftfor defense, and the right
for attack. These both take a subset of the data on the TSD and
addmore detail to it. All the screens use the same symbology and
the same perspective: `God's eyeview', with the F22's track
pointing up the center of the screen. The symbols are `dualcoded'
as far as possible, they differ both in shape and color. This makes
them easy to distinguish andensures that the displays will be
workable if the pilot has to wear laserprotective goggles. Other
F22s in the formation are represented by blue circles, and other
friendlies by green circles. Eachsymbol has a vector line which
shows its direction and approximate speed. As the practice
missionproceeds, four yellow squares appear at the top of the TSD.
This symbol indicates thatidentification is incomplete. The targets
were probably detected by an AWACS and transmitted tothe F22 by the
Joint Tactical Information Distribution System. All the pilots in
the formation willsee the same displays. As well as a datalink that
can import information from AWACS, the F22 isfitted with an
IntraFlight Data Link (IFDL) which can transfer system and target
informationamong F22s. The IFDL operates at low power and in an RF
band which attenuates rapidly in theatmosphere, so it is difficult
for an adversary to detect or track. The F22's
NorthropGrumman/Texas Instruments APG77 radar could identify the
targets, but it will not do so to beginwith. The F22's sensor
management and EMCON functions divide the airspace around the
fighterinto concentric zones. In the outer zone, targets are not
close enough to be a threat, and thesystem will not break radar
silence to identify them. As they get closer and enter the
`situationalawareness' zone, the system is programmed to identify
and track them. The next zone is defined
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as that within which the F22 pilot has the option to engage or
avoid the threat. The inmost zoneis bounded by the range of the
threat's missiles. In each case, the system uses the radar only
asmuch as is necessary to maintain a track. As the target gets
closer, the radar will revisit it moreoften. In the simulated
engagement, one of the targets gives the game away by using radar.
TheF22's LockheedSanders ALR94 EW sensor suite "does not compare
with anything out theretoday it's vastly superior," remarks a
Lockheed engineer. It can determine the target's bearingand, to
some extent, its range. CIP software compares the incoming radar
signal with other targetdata. Its source correlates with the
unidentified targets being tracked by AWACS, so it is placed inthe
same `track file'. The software selects the highestquality data
from each sensor to build thedisplay. The target symbols change to
red triangles hostiles. The CIP computes the detectionenvelope of
the hostile's radar against the F22 at its current bearing. It
appears on the defensescreen as a blue cone emanating from the
target. The CIP will do the same for any SAM radars,placing a
circle around them on the defensive display. If the F22 turns to
present its morereflective side or rear to the radar, the envelope
will expand visibly. The pilot can choose whetherto risk detection
or change course. As the targets enter the engageoravoid zone, the
F22 pilotsteers a cursor over them and presses a bar on the
throttle. This activates a `shoot list': thetargets are placed in
order of priority and tracked for engagement. The targets may be
dividedamong the formation using the IFDL, and only one radar at a
time need be used for tracking.Targets on the shoot list are
represented by numbered circles. The pilot can override the
shootlist. It is one of a number of techniques pioneered by the
USAF Pilot's Associate. One of the goalsof Pilot's Associate was
`adaptive aiding' in which automation would be there to help the
pilot inhighworkload situations, but would not take over against
the pilot's wishes. The objective is tohelp the pilot make good
decisions quickly, rather than automating the decision process.
Similarly,the defensive screen will show countermeasure and
maneuver options against an imminent threat.The target formation
appears in a larger scale on the righthand attack display. On the
left of thescreen is an altitude display. On the right, the targets
appear on a range scale, compressed to onedimension, which shows
the maximum range of the F22's missiles and the lethal envelope of
thetarget's missiles. The F22 pilot can use that information to
decide whether to fire as soon aspossible and break away earlier or
whether to allow the range to close and give the target lesschance
to escape. The shootlist function selects and arms missiles. A
`SHOOT' cue appears onthe attack display and HUD when the target is
within range. Once the missile is in the air, thesystem steps to
the next target. The withinvisualrange (WVR) fight has not been
ignored. TheHUD regarded as a primary flight display, for the first
time on a US fighter uses a combinationof UStype symbology,
emulating verticaltape displays, and counterpointer symbols. The
F22 willenter service with the Joint HelmetMounted Cueing System
(JHMCS) and AIM9X missile for offboresight engagements.
(Elbit/Kaiser and Honeywell/GEC teams are competing to
produceJHMCS.) The displays and datalink will be important in WVR.
Simulations have shown that thedatalink reduces ambiguous voice
calls. It also means that a target that is within the radarenvelope
of one aircraft in the formation is visible on the displays of all
of them. Anothertechnology which may well be added to the F22 is
threedimensional (3D) sound. The F22 has a
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Bose audio system to provide active noise reduction, and
research is showing that 3D audioprovides a very accurate and
reliable bearing and elevation cue. The F22 display system has
beenextensively simulated since the late 1980s, including many
realtime sorties using multipleinterlinked dome displays. The
results, says Lockheed Martin, show that the F22 system isintuitive
and easily learned, and raises the performance level of an
inexperienced pilot. Lockheedengineers say that it would not be
easy to emulate the F22 avionics system on an existingaircraft. The
system works, they say, because the barriers between the different
sensors havebeen broken down. The most powerful sensor is the
APG77. Its activearray antenna consists ofnearly 2,000 fingersized
transmit and receive modules (produced by Texas
Instruments)embedded in a fixed array. The cost of these modules
has been the critical issue in the radar'sdesign since the USAF
decided to aim for an activearray radar in the Advanced Tactical
Fighterprogram in the early 1980s. They have entered production for
several programs and the USAF issatisfied that the APG77 will be
affordable. A pair of the EMD modules weighs a mere 15g andputs out
over 4W of power. The modular design of the APG77 antenna and power
supplyeliminates the cause of many radar failures. The APG77 is
also expected to be extremely agile,and capable of changing the
direction, power and shape of the radar beam very rapidly to
acquiretarget data while minimizing the chance that its signals
will be intercepted or tracked. The F22could be described as
bristling with CNI and EW antennas if any of them had been visible.
The 30plus apertures are all flush with the surface of the
aircraft, including largeaperture arrays in thewing leading edges.
The EW system includes azimuth and elevation arrays to provide 3D
targetdata. Windows for the electrooptical Missile Launch Detection
system are located around theforward fuselage, and four dispensers
for flare, chaff and active radar decoy cartridges areinstalled in
the lower wing surfaces. An IR search and track (IRST) system was
part of the originalATF requirement. It was deleted during dem/val,
but the Avionics Directorate of the USAF WrightLaboratories has
continued its development with Lockheed Martin as the contractor,
and space,weight, power and cooling provisions for IRST are still
on the aircraft. A lowobservable IRSTwindow for the F22 was tested
for stealth and durability last year. IRST is valuable for
raidassessment, because of its high angular resolution. It is also
useful against tactical ballisticmissiles, and it can double as a
thermal imaging system for ground attack. The F22 is the firstUSAF
fighter in many years to have a specially developed life support
system. It includes the HGU86P helmet, developed by Helmets
Integrated Systems of the UK. The antig garment covers moreof the
body than earlier gsuits and can exert pressure on more of the
body's blood supply. Theoxygen mask and counterpressure vest are
designed for positivepressure breathing and arecontrolled by a
breathing regulator and antig garment (BRAGG) valve which reacts to
the rate ofg onset. Research at the USAF's Brooks Laboratory in San
Antonio has shown that positivepressure breathing, the smart valve
and improved antig suit increase g tolerance, reduce the riskof
ginduced loss of consciousness and allow the pilot to sustain g
with less physical strain and
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fatigue (an important factor in sustaining high sortie rates).
Positivepressure breathing alsoprovides altitude protection. USAF
fighters are normally limited to 50,000ft because, if power
andcockpit pressure are lost, the pilot will lose consciousness
before the aircraft descends into thickerair. The F22 lifesupport
ensemble has been chambertested to 66,000ft and its emergencyoxygen
system will function long enough to reach lower altitudes. The
lifesupport system includesan aircooling garment underneath the
gsuit and counter pressure vest, and optional suits thatprotect the
pilot from chemical and biological agents and cold water immersion.
Up and halfwayThe F22's first flight marks only the midpoint
between the start of EMD and the fighter's entryinto service. Nine
EMD aircraft are being built. The first three (40014003) are
dedicated toairframe and engine testing and weapon release
clearances. The second of these is due to fly inApril next year and
the third the following September. They will have nonstandard
displays, nomission avionics and simpler, flighttestdedicated
communications equipment. Conducting the firstflight at Marietta
was cheaper than disassembling the completed prototype and
transporting it toEdwards AFB, which had been considered. A mission
control center has been set up at Marietta,and the first flights
have been rehearsed extensively using the
pilotandhardwareintheloopsimulator in Fort Worth. Lockheed Martin
plans a physical rehearsal of the first flight, using an F15
escorted by F16 chase aircraft. After eight flights, the F22 will
be ferried to Edwards AFB nonstop, with inflight refueling. In July
last year, the USAF deferred development of the F22B twoseater to
save money and eliminated two F22Bs from the test program. This was
not a `painless'decision, says Metz, but the fighter's carefree
handling and straightforward flying qualities shouldmake it easy
and safe to fly, while recording devices and the debriefing
functions built into theBoeingdeveloped training system allow a
pilot's performance to be reviewed on the ground. Thefourth to
ninth aircraft (40044009) will fly between April 1999 and May 2000,
and are alldedicated to avionics testing. The plan calls for all
these aircraft to be kept identical: as newhardware and software is
available, all the aircraft will be retrofitted at the same time.
Softwareand hardware will be released in blocks. The first three
test aircraft will fly with Block 0, whichincludes the inertial
reference system, the stores management system and the displays.
The firstmajor milestone in avionics testing is Block 1, which
includes radar and CNI. Altogether,comments Broadwell, Block 1
includes almost half the lines of code in the final system, and
itssuccessful completion will prove a number of principles. "If we
survive Block 1, we'll know a lotabout software integration, and
we'll know how to debug the system. We won't be wrestlingfunctional
and infrastructure issues at the same time." With radar and CNI,
too, Block 1 willdemonstrate the first elements of sensor fusion.
Block 1 will be available for testing almost a yearbefore F22 4004
is ready, and will fly first aboard the Boeingbuilt Flying Test Bed
(FTB), amodified 757 airliner fitted with the APG77, other sensors,
CIPs and displays. If the FTB tests gowell, Broadwell hopes that
the F22 test aircraft can be updated quickly to the Block
2configuration, which adds radar modes and some EW functions and
should be available in mid1999. Block 3, originally planned as the
final preinitial operating capability (IOC) release of thesoftware,
should be released in April 2000 and includes all EW functions. It
will be followed in late
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2000 by Block 3.1, which includes provision for JDAM. Although
the task of developing such aradical system is not trivial,
Broadwell believes that solid progress is being made. "We surprised
alot of people," he said, by keeping the current total of 1.7
million software lines of code (SLOC)relatively close to the 1.3
million SLOC that was predicted in December 1990. "If we can hold
thegrowth to 25 per cent we'll amaze the world." Every piece of
hardware intended for the systemhas been built and is working in
the laboratory, including a complete radar array, which is
lookingout over the airport at Northrop Grumman's Baltimore plant
and is linked to a CIP. Softwaredevelopment so far has stayed on
track, and the Block plan is mostly cumulative: "When you adda
block in CNI, you add a function. When you add a block in radar,
you add modes. It's done, andit doesn't change." Flight tests
should confirm that the F22's `conservative' looks belie
itsperformance. Details are classified: however, the immense thrust
should provide remarkableacceleration and speed. A chart published
in 1991 shows that the F22 is slightly faster onintermediate power
than an F15C on full burner, when both aircraft have eight AAMs on
board.(The speeds are probably around Mach 1.61.7.) "We expect that
this will be one of the thingsthat surprises the air force," said
Metz. "If you don't know what you're doing, you'll besupersonic."
Unlike most fighters, too, the F22 achieves its highest rate of
climb at supersonicspeed. It is almost as fast with afterburner as
without. The augmentors will be used mainly foracceleration and
supersonic maneuvering. Metz believes that the "afterburner will
generally not berequired", and that when it is used it will be in
bursts of seconds and tens of seconds, at theoutside. The principal
breakthrough in terms of straightline performance is supercruise.
The USAFhas stated that "about 30 minutes in a onehour mission" can
be flown at supersonic speed, threeto six times the supersonic
endurance of any fighter using augmentors. On a typical mission,
the F22 can sustain supersonic speed for most of the time that it
is over hostile territory. Supersonicendurance varies with speed: a
supercruising F22 may vary its speed between Mach 1.1 to
Mach1.5plus according to the tactical situation. Supercruise has
many tactical advantages. A fasteraircraft retains engagement
control: if its pilot chooses to fight, the adversary cannot run,
and ifthe F22 pilot disengages, the adversary cannot sustain the
pursuit. The F22 can maneuveraround a slower adversary to engage it
from the rear, and enters the fight with greater energyand
overtaking speed. Supersonic speed goes along with a higher
altitude capability: both shrinkthe lethal envelope of SAMs.
Firstlook, FirstShot The F22's reduced headon RCS is claimed
toguarantee a firstlook, firstshot advantage against any
contemporary fighter radar. However,where the F22 differs from any
other aircombat fighter is in the importance placed on allroundRCS,
which is described as being in the same order as the slower and
less agile F117 and B2. Allround stealth is aimed primarily at the
SAM threat. Stealth and supercruise are synergistic: theaim is not
to be invisible, but to reduce detection range to the point where
the system cannotcomplete an engagement against a fastflying target
before the range begins to increase. Thephilosophy of `balanced
observables' mandated that the F22's IR signature be reduced so
that IRand radar sensors would have a similar detection range. The
most prominent source of IRradiation from an aircraft is its
exhaust plume. On the F22, plume radiation is reduced by
minimalafterburner use, the 2D nozzles and bypass mixing. Much of
the remaining IR signature
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comprises reflected solar IR radiation and emissions caused by
skin friction heat. IRabsorbentpaint reduces solar reflection; it
is analogous to normal paint except that it absorbs in the IRband.
Friction heat cannot be absorbed by paint, but coatings have been
developed that changethe emissivity of a surface: that is, they
make it less efficient at emitting IR. To some extent,coatings may
also be able to shift the wavelength of the emitted IR energy into
wavebands whichattenuate most rapidly in the atmosphere. Heat from
electronics and other systems can cause IRemissions. The F22's
specialized environmental control system stores peak heating loads
in heatsinks and removes it from the aircraft through airtofuel
heat exchangers. The F22's visualsignature will be managed by a new
camouflage scheme, an overall grey with darker, softedgedareas on
the wings, body and tail. The base color is intended to match the
luminance of the sky attypical combat altitudes and extreme visual
range, while the darker patches send mixed signals tothe eye or to
an electrooptical seeker with an edgerecognition algorithm. Metz
prefers not to bedrawn into the debate over the value of the
lowairspeed, highalpha maneuvers demonstrated bythe Sukhoi Su37 at
the Farnborough air show last September, or by the X31. Some pilots
believethat the ability to fire a shortrange AAM in almost any
direction, by changing the fighter's bodyangle independently of its
flightpath, will be critical in future combats. Others
disagreevehemently, arguing that poststall maneuvers kill so much
airspeed that they are `suicidal' in amanyonmany fight. Whatever
the outcome of the debate, the F22 should be able to acquit
itselfwell, with a very large flight envelope that is actually
usable in combat. (At least some spectacularairshow maneuvers have
involved disabling safetyrelated limiters.) Alphas to 60
weredemonstrated in the YF22 program, and some roll maneuverability
was retained at that extremepitch angle. The acual inservice alpha
limit has not been released. However, the fact that 60was
demonstrated in flight tests, and the F22 fuel system simulator is
built to emulate 60alphas, suggests that the fighter will indeed be
designed to attain 60 in service more than twicethe service limit
of any other fighter. At alphas of 15 and above, the F22 rolls at
least twice asfast as the F15, and the gap widens until the F15
hits its roll limit of 30 alpha. Maximum pitchrates are up to twice
as fast as the F16. The F22's pitch rate is so fast that it is
inhibited by asoft stop in the aft movement of the sidestick.
Pulling the stick through the stop overrides a limitin pitch
acceleration, and it is considered best for the pilot to be aware
that the F22 is about torespond very fast and that the BRAGG valve
will respond in turn. The F22 pilot who decides thatthe tactical
situation warrants highalpha, lowspeed maneuvering may be reassured
by thefighter's controllability and thrusttoweight ratio. The F22
should be able to end a maneuverrapidly when required, and will
accelerate quickly to a safer combat speed. The fighter will
beevaluated against `actual and simulated adversary aircraft'
during its flighttest program, Metzstates. "It will be a great
airshow airplane, too," he added. The F22 is claimed to have more
thantwice the range of the F15C at subsonic speed, with a greater
margin when the mission includessupersonic flight. Such numbers
have to be treated with caution. In this case, the comparison
isprobably based on a full missile load and internal fuel only. The
F22's internal fuel load is greater
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than that of an F15C with three 2,300liter tanks, and it has
much less drag, so it should have agreater combat radius on a
similar mission profile. Despite its remarkable capabilities, the
F22should not be a hardtomaintain, exotic aircraft. Every part of
the aircraft has been designed byan integrated product team that
includes engineers and specialists in production and
maintenance,and the goal is an aircraft that requires onethird as
many maintenance hours per flight hour asthe F15. Builtin test
equipment replaces offboard test equipment, and more items are
designedto be replaced on the flightline rather than repaired in an
intermediatelevel shop on the base. A24aircraft unit of F22s
requires only eight C141Bloads of equipment for a 30day
deployment,versus 18 for the same number of F15s. It requires half
as many people to support the F22 asare needed for the same number
of F15s. So far, developmental problems have been minor, withthe
exception of the turbine redesign, and program managers note that
preflight testing and tightconfiguration control have unearthed
problems before rather than after first flight when therehas been
time to solve them at reasonable cost. The main cause of delays has
been funding.Since the EMD program started, budget cuts have moved
the first flight from August 1995 to May1997, and have IOC from
2001 to 2004. These actions have made the F22 more expensive.
Thetotal program cost development, 438 aircraft, spares, ground
equipment and construction stands at US$73.5 billion. Much of this
total includes 10 years or more of projected inflation, and ithas
increased as IOC has slipped. Lockheed Martin's development
contract for the airframe wasestimated late last year at US$12
billion. A review last year showed that costs were likely to
risemore than predicted, because defense industry costs are
expected to rise faster than thegovernmentwide inflation rate on
which the Pentagon's budgets are based. The Pentagon hasresponded
by slowing initial production and adding a US$1.45 billion reserve
to the EMD program.This is expected to fund investments in
production and program changes (such as the earlyprocurement of
some avionics components) that will reduce costs in the future, and
includes theintegration of the AIM9X and JHMCS. The total EMD cost,
including Lockheed Martin and Pratt &Whitney contracts, and
work done by the USAF, now seems likely to exceed US$17
billionincluding the sums already spent or committed. The projected
average flyaway price of the F22 isnow US$71 million in 1996
dollars. (This price includes a fullyequipped aircraft but no
spares orweapons.) Some of the added investments being made now,
and other proposals made by thecontractors including multiyear
procurements are intended to ensure that this numbercontinues to
track the budgeted rate of inflation, rather than with defense
industry costs.Lockheed Martin managers argue that export sales
would reduce the cost of the F22 to thePentagon, and the sooner the
better. Department of Defense policy precludes final contracts
untilinitial operational test and evaluation is complete, in
200102, but that does not prevent LockheedMartin from briefing
export customers. The company planned to do this at the Farnborough
airshow, but the Pentagon withheld permission until the cost
picture became clearer. USAF DeputyChief of Staff Gen Tom Moorman
noted in January that "I have no doubt that the F22 will bereleased
for export, and we have some authority to do that now." An
executive committee cochaired by the US Under Secretary of Defense
for Aquisition and Technology Paul Kaminski and
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Gen Joe Ralston, vicechair of the Joint Chiefs of Staff, is
reviewing the security issues raised bythe possible export of a
stealthy aircraft. Some of the stealth features of the F22 are
`modular' innature and could be selectively removed or downgraded
for export. Potential customers include F15 operators such as
Israel, Japan and Saudi Arabia. South Korea is considering a
highend fighterto complement the F16, and Lockheed Martin is
looking at the possibility of selling small `silverbullet' F22
fleets to operators of modern but nonstealthy fighters; even
Eurofighter members arenot ruled out. Granted that cost definitions
are fraught with a lack of international consistency, theF22's
flyaway cost of US$71 million does not appear widely different from
the US$50 million toUS$60 million figures recently quoted (by the
German government audit office) for theEurofighter, as well as
those for Rafale. Eurofighter's claim, repeated at Farnborough,
that itsaircraft is "less than half the price" of the F22 appears
to rest on a comparison between a flyawaycost and a unit program
cost. Lockheed Martin executives appear reasonably confident that
the F22 will survive the QDR and this year's budget deliberations.
Production may be cut to 300350aircraft, but it would not
materially affect the program until 2008 three US elections and at
leasttwo presidents hence. Both Lockheed and the USAF caution
against deeper cuts, partly becauseexperience with AWACS and
similar `force multiplier' assets is showing that the limiting
factor maybe the ability to sustain and retain essential people for
small, highvalue forces that spend monthson end away from home.
This year is pivotal for the F22. If it survives the QDR, it is
likely tosurvive through the tenure of the administration, and by
2001 it should be well established: but bymaking the air
superiority mission and the need for the F22 its top priorities in
the QDR, the USAFis nailing its colors to the mast. If the F22 does
not survive, and the F/A18E/F emergesunscathed, the USAF will not
see another new aircraft before the JSF arrives in 2010. It will be
avictory for the advocates of seabased airpower, and a setback for
the concept of an independentair arm. The continuation of the F22
program, however, would be the starting point for a new,more
forwardthinking airpower doctrine for the 21st century.
CAPTION: An artist's rendition of a visual range confrontation.
The F22 in the picture has pursuedtwo adversary aircraft to low
altitude, destroying one (the `fireball' at the top right of the
picture),and has launched one of its six AIM120C airtoair medium
range missiles at the remaining enemyfighter. The visible
camouflage scheme is one indication that the US Air Force has not
ignored thecertainty of visualrange combat (the retention of a 20mm
cannon and 480 rounds of ammunitionbeing another). Lockheed
Martin
CAPTION: The F22 team is using a unique vertical modular tooling
process for assembly of themidfuselage, which incorporates the four
weapon bays, the main landing gears and the inletducts. Made of
carbonfiber/epoxy, the ducts curve sharply upwards and inwards to
mask theengine faces from radar, changing section smoothly from
rhomboidal to circular, and their innercontours must be smooth and
accurate to maintain their stealth characteristics. Lockheed
Martin
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CAPTION: F22 versus surfacetoair missile attack. A conventional
fighter is detected at point A.The SAM system projects its track
and launches towards intercept point B. The missile retainsenough
energy to counter target maneuvers. The stealthy F22, by
comparison, is flying equallyclose to the SAM system, but is not
detected until point C. The missile will take longer to reach
itsaltitude because the slant range is greater. Coupled with the
F22's greater speed, this means thatthe first possible intercept
point is D a lowenergy, longrange tail chase against a target at
thelimits of the system's tracking range. A moderate supersonic
`jink' at D runs the missile out ofenergy. Source: Lockheed
Martin
CAPTION: The F22 canopy is approximately 3.5m long, 1m wide and
0.7m tall, and weighs about160kg. This test canopy will be mounted
on the rocketpowered multiaxis seat ejection vehicle,and launched
along rails to simulate canopy jettison and seat firing in an
aircraft traveling atvarious speeds. Lockheed Martin
CAPTION: Pratt & Whitney's F119PW100 twinspool augmented
turbofan engine was selected topower the F22 in April 1991. The
first production engine is due in late 1999. Pratt &
Whitney
CAPTION: An airtosurface capability has been developed for the
F22. The aircraft's lowerweapon bays have been modified to carry
two McDonnell Douglas GBU32 1,000 lb (450kg)classJoint Direct
Attack Munitions. The GBU32 is a nearprecision standoff weapon
guided to its targetby means of an inertial measurement unit
updated inflight with data from Global PositioningSystem
satellites. In this artist's rendition, an F22 pilot releases both
GBU32 bombs against anenemy airfield's surfacetoair missile
site.
CAPTION: The tactical display system that will provide
unsurpassed situation awareness for F22pilots. The defense display
on the left gives pilots the information they will need to
protectthemselves against threats. The display in the middle
provides an overall situation awareness andnavigation information,
while on the right is the target attack display. Boeing
CAPTION: Boeing has modified a 757 airliner into a flying
avionics testbed for the F22.Modifications include installing a
wing shape geometrically identical to the F22 on the crown ofthe
fuselage. This sensor wing will include F22 electronic warfare and
communication, navigationand identification sensors. There are also
various apertures to replicate F22 antennas, and the F22 forward
fuselage structure housing a prototype radar. Boeing
8 Images
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F222804
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vertical modular tooling process2805
F22 versus surfacetoair2806
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F22 canopy2807
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F119PW100 twinspool2808
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F22 releases GBU32 bombs2810
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tactical display system2811
Boeing 7572812
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Copyright IHS Global Limited, 2015
THE PROGRESS OF THE F22 FIGHTER PROGRAM