Design Of Lockheed Martin F-35 Lightning II

Design

The F-35 appears to be a smaller, slightly more conventional, single-engine sibling of the sleeker, twin-engine Lockheed Martin F-22 Raptor, and indeed drew elements from it. The exhaust duct design was inspired by the General Dynamics Model 200 design, which was proposed for a 1972 supersonic VTOL fighter requirement for the Sea Control Ship.For specialized development of the F-35B STOVL variant, Lockheed consulted with the Yakovlev Design Bureau, purchasing design data from their development of the Yakovlev Yak-141 "Freestyle". Although several experimental designs have been built and tested since the 1960s including the navy's unsuccessful Rockwell XFV-12, the F-35B is to be the first operational supersonic, STOVL stealth fighter.
The F-35 has a maximum speed of over Mach 1.6. With a maximum takeoff weight of 60,000 lb (27,000 kg),the Lightning II is considerably heavier than the lightweight fighters it replaces. In empty and maximum gross weights, it more closely resembles the single-seat, single-engine Republic F-105 Thunderchief, which was the largest single-engine fighter of the Vietnam war era. The F-35's modern engine delivers over 60 percent more thrust in an aircraft of the same weight so that in thrust to weight and wing loading it is much closer to a comparably equipped F-16.
Acquisition deputy to the assistant secretary of the air force, Lt. Gen. Mark D. "Shack" Shackelford has said that the F-35 is designed to be America's "premier surface-to-air missile killer and is uniquely equipped for this mission with cutting edge processing power, synthetic aperture radar integration techniques, and advanced target recognition."

Some improvements over current-generation fighter aircraft are:

• Durable, low-maintenance stealth technology, using structural fiber mat instead of the high-maintenance coatings of legacy stealth platforms;
• Integrated avionics and sensor fusion that combine information from off- and on-board sensors to increase the pilot's situational awareness and improve target identification and weapon delivery, and to relay information quickly to other command and control (C2) nodes;
• High speed data networking including IEEE 1394b and Fibre Channel.(Fibre Channel is also used on Boeing's Super Hornet.)
• The Autonomic Logistics Global Sustainment (ALGS), Autonomic Logistics Information System (ALIS) and Computerized Maintenance Management System (CMMS) are claimed to help ensure aircraft uptime with minimal maintenance manpower.However the Pentagon has moved to open the sustainment for competitive bidding by other companies.This was after Lockheed admitted that instead of costing twenty percent less than the F-16 per flight hour, the F-35 would actually cost twelve percent more.The USMC have implemented a workaround for a cyber vulnerability in the system.
• Electrohydrostatic actuators run by a power-by-wire flight-control system.

Lockheed Martin claims the F-35 is intended to have close and long-range air-to-air capability second only to that of the F-22 Raptor.The company has suggested that the F-35 could also replace the USAF's F-15C/D fighters in the air superiority role and the F-15E Strike Eagle in the ground attack role, but it does not have the range or payload of either F-15 model.The F-35A does carry a similar air-to-air armament as the conceptual Boeing F-15SE Silent Eagle when both aircraft are configured for low observable operations and has over 80 percent of the larger aircraft's combat radius, under those conditions.
Lockheed Martin has said that the F-35 has the advantage over the F-22 in basing flexibility and "advanced sensors and information fusion".
Structural composites in the F-35 are 35% of the airframe weight (up from 25% in the F-22). The majority of these are bismaleimide (BMI) and composite epoxy material.However the F-35 will be the first mass produced aircraft to include structural nanocomposites, namely carbon nanotube reinforced epoxy.
The F-35 program has learned from the corrosion problems that the F-22 had when it was first introduced in 2005. The F-35 uses a gap filler that causes less galvanic corrosion to the skin, is designed with fewer gaps in its skin that require gap filler, and has better drainage.
A United States Navy study found that the F-35 will cost 30 to 40 percent more to maintain than current jet fighters.A Pentagon study found that it may cost $1 trillion to maintain the entire fleet over its lifetime.
The relatively short 35 foot wingspan of the A and B variants is set by the F-35B's requirement to fit inside the Navy's current amphibious assault ship elevators. The F-35C's longer wing is considered to be more fuel efficient.

Engines

The F-35's main engine is the Pratt & Whitney F135. The General Electric/Rolls-Royce F136 was under development as an alternative engine until December 2011 when the manufacturers canceled work on it. The F135/F136 engines are not designed to supercruise in the F-35,but the F-35 can achieve a limited supercruise of Mach 1.2 for 150 miles.The STOVL versions of both power plants use the Rolls-Royce LiftSystem, designed by Lockheed Martin and developed to production by Rolls-Royce. This system is more like the Russian Yak-141 and German VJ 101D/E than the preceding generation of STOVL designs,such as the Harrier Jump Jet in which all of the lifting air went through the main fan of the Rolls-Royce Pegasus engine.
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 is near the front of the aircraft and provides a counterbalancing thrust using two counter-rotating blisks.It 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 unheated engine bypass air through wing-mounted thrust nozzles called Roll Posts.Like lift engines, the added lift fan machinery increases payload capacity during vertical flight, but is dead weight during horizontal 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.
To date, F136 funding has come at the expense of other parts of the program, reducing the number of aircraft built and increasing their costs.The F136 team has claimed that their engine has a greater temperature margin which may prove critical for VTOL operations in hot, high altitude conditions.
Pratt & Whitney is also testing higher thrust versions of the F135, partly in response to GE's claims that the F136 is capable of producing more thrust than the 43,000 lbf (190 kN) supplied by early F135s. The F135 has demonstrated a maximum thrust of over 50,000 lbf (220 kN) during testing.The F-35's Pratt & Whitney F135 is the most powerful engine ever installed in a fighter aircraft.
The F135 is the second (radar) stealthy afterburning jet engine and like the Pratt & Whitney F119 from which it was derived, has suffered from pressure pulsations in the afterburner at low altitude and high speed or "screech". In both cases this problem was fixed during development of the fighter program.
Turbine bearing health in the engine will be monitored with thermoelectric powered wireless sensors.