The F-35 has a low radar cross section
primarily due to the materials used in construction, including fibre-mat.
The F-35 also has a more stealthy shape than past fighters, including a
zigzag-shape weapons bay and landing gear door.
In spite of being smaller than the F-22, the F-35 has a larger radar cross
section. It is said to be roughly equal to a metal golf ball rather than
the F-22's metal marble.
The F-35's main engine is the Pratt &
Whitney F135. The General Electric/Rolls-Royce F136 has been developed as
an alternate engine. The STOVL versions of both power plants use the
Rolls-Royce LiftSystem, patented by Lockheed Martin but built by
The Lift System is composed of a lift fan, drive shaft, two roll posts and
a "Three Bearing Swivel Module" (3BSM). The 3BSM is a thrust vectoring
nozzle which allows the main engine exhaust to be deflected downward at
the tail of the aircraft. The lift fan near the front of the aircraft
provides a counter-balancing thrust. Somewhat like a vertically mounted
turbofan within the forward fuselage, the lift fan is powered by the
engine's low-pressure (LP) turbine via a drive shaft and gearbox. Roll
control during slow flight is achieved by diverting pressurized air from
the LP turbine through wing mounted thrust nozzles called Roll Posts.
The F-35B's lift fan achieves the same 'flow multiplier' effect as the
Harrier's huge, but supersonically impractical, main fan. Like lift
engines, this added machinery is just dead weight during horizontal flight
but provides a net increase in payload capacity during vertical flight.
The cool exhaust of the fan also reduces the amount of hot, high-velocity
air that is projected downward during vertical take off (which can damage
runways and aircraft carrier decks). Though complicated and risky, the
lift system has been made to work to the satisfaction of DOD officials.
To date, F-136 funding has come at the expense of other parts of the
program, reducing the number of aircraft built and increasing their costs.
The F-136 team has claimed that their engine has a greater temperature
margin which may prove critical for VTOL operations in hot, high altitude
The F135/F136 engines are not designed to supercruise in the F-35.
In late 2008 the Air Force revealed that the F-35 would be about twice as
loud at takeoff as the F-15 Eagle and up to four times as loud upon
landing. As a result, residents near Luke Air Force Base, Arizona and
Eglin Air Force Base, Florida, possible homes of the jet, have requested
that the Air Force conduct environmental impact studies concerning the
F-35's noise levels.The city of Valparaiso, Florida, adjacent to Eglin
AFB, threatened in February 2009 to sue the Air Force over the impending
arrival of the F-35s, but this lawsuit was settled in March 2010.
Moreover, it was reported in March 2009 that testing by Lockheed Martin
and the Royal Australian Air Force revealed that the F-35 was not as loud
as first reported, being "only about as noisy as an F-16 fitted with a
Pratt & Whitney F100-PW-200 engine" and "quieter than the Lockheed Martin
F-22 Raptor and the Boeing F/A-18E/F Super Hornet."
The F-35 includes a GAU-22/A four-barrel 25mm cannon. The cannon will be
mounted internally with 180 rounds in the F-35A and fitted as an external
pod with 220 rounds in the F-35B and F-35C. The gun pod for the B and C
variants will have stealth features. This pod could be used for different
equipment in the future, such as EW, reconnaissance equipment, or possibly
a rearward facing radar.
Internally (current planned weapons for integration), up to two air-to-air
missiles and two air-to-air or air-to-ground weapons (up to two 2,000 lb
bombs in A and C models (BRU-68); two 1,000 lb bombs in the B model
(BRU-67) can be carried in the bomb bays.These could be AIM-120 AMRAAM,
AIM-132 ASRAAM, the Joint Direct Attack Munition (JDAM) – up to 2,000 lb
(910 kg), the Joint Stand off Weapon (JSOW), Small Diameter Bombs (SDB) –
a maximum of four in each bay (Three per bay in F-35B, the Brimstone anti-armor
missiles, and Cluster Munitions (WCMD). The MBDA Meteor air-to-air missile
is currently being adapted to fit internally in the missile spots and may
be integrated into the F-35. The UK had originally planned to put up to
four AIM-132 ASRAAM internally but this has been changed to carry 2
internal and 2 external ASRAAMs.It has also been stated by a Lockheed
executive that the internal bay will eventually be modified to accept up
to 6 AMRAAMs.
At the expense of being more detectable by radar, many more missiles,
bombs and fuel tanks can be attached on four wing pylons and two near
wingtip positions. The two wingtip locations can only carry AIM-9X
Sidewinder. The other pylons can carry the AIM-120 AMRAAM, Storm Shadow,
AGM-158 Joint Air to Surface Stand-off Missile (JASSM) cruise missiles,
guided bombs, 480-gallon and 600-gallon fuel tanks. An air-to-air load of
eight AIM-120s and two AIM-9s is conceivable using internal and external
weapons stations, as well as a configuration of six 2,000 lb bombs, two
AIM-120s and two AIM-9s.With its payload capability, the F-35 can carry
more weapons payload than legacy fighters it is to replace as well as the
F-22 Raptor.Solid-state lasers were being developed as optional weapons
for the F-35 as of 2002.
The F-35 utilizes a new substance called fiber mat embedded in the
composite skin. This avoids the need to use stealthy appliqués and
coatings that come off in flight. Fiber mat is also part of the aircraft's
load bearing structure.
The Teen Series of fighters (F-15, F-16, F/A-18) were notable for always
carrying large external fuel tanks, but as a stealth aircraft the F-35
must fly most missions on internal fuel. Unlike the F-16 and F/A-18, the
F-35 lacks leading edge extensions (LEX) and instead uses stealth-friendly
chines for vortex lift in the same fashion as the SR-71 Blackbird. The
small bumps just forward of the engine air intakes form part of the
diverterless supersonic inlet (DSI) which is a simpler, lighter and
stealthier means to ensure high-quality airflow to the engine over a wide
range of conditions
The F-35 features a full-panel-width "panoramic cockpit display" (PCD)
glass cockpit, with dimensions of 20 by 8 inches (50 by 20 centimeters). A
cockpit speech-recognition system (Direct Voice Input) provided by Adacel
is planned to improve the pilot's ability to operate the aircraft over the
current-generation interface. The F-35 will be the first US operational
fixed-wing aircraft to use this system, although similar systems have been
used in AV-8B and trialled in previous US jets, particularly the F-16
VISTA. In development the system has been integrated by Adacel Systems Inc
with the speech recognition module supplied by SRI International.The pilot
flies the aircraft by means of a right-hand side stick and left-hand
A helmet-mounted display system (HMDS) will be fitted to all models of the
F-35. A helmet-mounted cueing system is already in service with the F-15s,
F-16s and F/A-18s. While some fighters have offered HMDS along with a head
up display (HUD), this will be the first time in several decades that a
front-line tactical jet fighter has been designed to not carry a HUD.
The Martin-Baker US16E ejection seat is used in all F-35 variants. The
US16E seat design balances major performance requirements, including
safe-terrain-clearance limits, pilot-load limits, and pilot size. It uses
a twin-catapult system that is housed in side rails.
Sensors and avionics
F-35's sensor and communications suite provides situational awareness,
command-and-control and network-centric warfare capability. The main
sensor on board the F-35 is its AN/APG-81 AESA-radar, designed by Northrop
Grumman Electronic Systems. It is augmented by the Electro-Optical
Targeting System (EOTS) mounted under the nose of the aircraft, designed
by Lockheed Martin. This gives the same capabilities as the Lockheed
Martin Sniper XR without compromising the aircraft's stealth.
Six additional passive infrared sensors are distributed over the aircraft
as part of Northrop Grumman's AN/AAQ-37 distributed aperture system (DAS),
which acts as a missile warning system, reports missile launch locations,
detects and tracks approaching aircraft spherically around the F-35, and
replaces traditional night vision goggles for night operations and
navigation. All DAS functions are performed simultaneously, in every
direction, at all times. The F-35's AN/ASQ-239 (Barracuda) Electronic
Warfare systems are designed by BAE Systems and include Northrop Grumman
components. The communications, navigation and identification (CNI) suite
is designed by Northrop Grumman and includes the Multifunction Advanced
Data Link (MADL). The F-35 will be the first jet fighter that has sensor
fusion that combines both radio frequency and IR tracking for continuous
target detection and identification in all directions which is shared via
MADL to other platforms without compromising their low observability.
Unlike older generations of aircraft, such as the F-22, all software for
the F-35 is written in C++ for faster code development. The Integrity
DO-178B real-time operating system (RTOS) from Green Hills Software runs
on COTS Freescale PowerPC processors.
The final Block 3 software for the F-35 is planned to have 8.6 million
lines of software code.
Helmet-Mounted Display System
than maneuvering with thrust vectoring, or canards to line up the target
directly ahead of the aircraft, like 4.5 Generation jet fighters, the F-35
does not need to point at the target to hit it. It uses combined radio
frequency and infra red (SAIRST) "situational awareness" to continually
track all nearby aircraft, the pilot's helmet-mounted display system (HMDS)
for displaying and selecting targets, and High Off-Boresight (HOBS)
weapons. The helmet system replaces the display suite-mounted head-up
display used in previous generation fighters. Because of this, Northrop
Grumman claims that "maneuvering is irrelevant".
The F-35's systems provide the edge in the
"observe, orient, decide, and act" OODA loop; Stealth and advanced sensors
aid in observation, automated target tracking helps in orientation, sensor
fusion simplifies decision making, and the aircraft's controls allow
action against targets without having to look away from them.