The Super Hornet upgrade to the F/A-18 is the platform for a multifaceted mission system revamp

When Boeing and the US Navy completed development of the Super Hornet in 1999, the task of taking the F/A-18 into the 21st century was not finished. The F/A-18E/F upgrade tackled the limitations of the original airframe and engine, but budget constraints and risk considerations ruled out a similar revamp of the avionics. Now, even as navy crews prepare for the first E/F fleet deployment in June next year, Boeing has begun a multi-faceted upgrade of the mission system.

The Super Hornet structural upgrade, which involved scaling the F/A-18 up by 25%, was designed to address range shortfalls and weight growth which were eroding the design's combat capability when operating from the US Navy's aircraft carriers. In addition to extending range and increasing the weight of unused weapons and fuel which can be returned to the carrier deck, the E/F upgrade improved survivability, expanded growth capacity and, ultimately, increased mission flexibility.

To reduce cost and risk, it was decided when E/F development was launched in 1992 that the Super Hornet would enter service with essentially the same avionics suite as the last production lot of F/A-18C/Ds. Although the F/A-18's avionics have evolved significantly since the aircraft entered service in 1983, the Super Hornet today lacks some of the capabilities to be found in its likely competitors and potential adversaries, particularly in the area of advanced sensors.

Advanced radar

By 2005 the F/A-18E/F will incorporate those capabilities, including active electronically scanned array (AESA) radar, as a result of the upgrade effort now under way. Because of budget constraints, different systems are being developed to different schedules, but Boeing and the US Navy have worked to package provisions for all the envisioned improvements in a single standard of Super Hornet, the Block 2, which will be delivered from 2003. Upgrades will then be "plugged into" Block 2 E/Fs on the production line and in service, as they become available.

Raytheon's APG-79 AESA radar is the biggest change planned for the Block 2 Super Hornet, replacing the same company's APG-73 mechanically scanned radar. Exploiting the AESA's substantially increased capability requires other changes in the aircraft, including new mission computers and displays, high-speed data and video network and, for the two-seatF/A-18F, and advanced crew station.

"There are a number of things the navy wanted in the Block 2 aircraft, but funding means that not all are available at the same time," says Dick Niehaus, Boeing's F/A-18E/F Block 2 mission system lead integrator. "The AESA is not ready soon enough, but we will build [the Block 2 Super Hornet] as an AESA aircraft. It will also accommodate the APG-73 and the aircraft will be ready for upgrade when the AESA becomes available."

The Block 2 strategy differs from the USN's previous approach to updating the F/A-18, which saw configuration changes introduced with each new production lot of aircraft. The result is a mix of fighters with different combat capabilities, which drives up the cost of retrofitting the fleet. "The Block 2 vision is to limit the number of aircraft configurations and to maintain configuration across multiple lots," says Niehaus. "Today different lots have different warfighting capability. Getting all the capabilities into all the aircraft will provide the navy with more flexibility."

The new approach also separates funding for development of the upgrades from the cost of retrofitting the aircraft. "It was easier to get funds for the AESA only, as opposed to the aircraft modifications and the radar," says Niehaus.

But building the aircraft to one configuration reduces the retrofit costs, he says. "Previously it was not usual to provision the aircraft for upgrades, resulting in a high cost to retrofit. With Block 2, retrofitting will involve plugging the box in."

Two standards

There will be two basic standards of Super Hornet. Aircraft up to production Lot 25 will be built in, or retrofitted to, Block 1 configuration. "Block 1 does not have everything architecturally that is planned for Block 2," says Niehaus. "Full-rate production [48 aircraft a year] begins with Lot 26, which makes it an appropriate point from a risk standpoint to break in the Block 2 upgrade." Of the 222 F/A-18E/Fs to be delivered from 2001 to 2005 under the current multi-year procurement contract, 144 will be built as Block 2s.

Lot 25 aircraft, to be delivered in 2002, represent the end state of Block 1 and the jumping off point for Block 2. The Block 1 upgrade tackles obsolescence issues with the legacy F/A-18 displays, engine controls and other systems. It also introduces the advanced mission computer (AMC) and Integrated Defensive Electronic Countermeasures (IDECM), and includes the Advanced Targeting Forward-Looking Infrared (ATFLIR), Joint Helmet-Mounted Cueing System (JHMCS), Multifunction Information Distribution System (MIDS) and Positive Identification System (PIDS) also being retrofitted to F/A-18C/Ds.

Block 2 will add the AESA, fibre-optic data network, digital video map computer (DVMC) and the advanced crew station (ACS) with large, 200 x 250mm (8 x 10in), situational awareness display. It will also introduce more capable versions of the new mission computer and IDECM self-protection suite. The Block 2 upgrades, and particularly the AESA, will be accommodated in the F/A-18E/F by a redesign of the forward fuselage, known as engineering change proposal (ECP) 6038, which is also part of Boeing's "must cost" initiative to drive the price of the Super Hornet down to $40 million (see panel on P31).

The most eagerly awaited element of the Block 2 upgrade is the APG-79 AESA, which promises major improvements in situational awareness, lethality, survivability, supportability and affordability, says deputy programme manager Mike Pingsterhaus. Compared with the current APG-73, the active-array radar provides significantly increased range against air targets and higher resolution synthetic-aperture radar (SAR) ground imaging.

The "inertialess" electronically scanned beam allows air-to-air and air-to-ground modes to interleave sequentially, providing near-simultaneous operation. "The front seater can do air-to-air and the backseater can do air-to-ground and they can designate different targets," says Pingsterhaus. "The radar can track four air targets with weapon-aiming quality while doing a SAR map." The AESA's "much lower" radar cross-section and the long stand-off ranges possible increase survivability, he says.

Tim Adrian, Boeing's chief engineer, AESA, says the APG-79 is designed to cost "the same or less than the APG-73". Total ownership costs will be much lower, says Pingsterhaus. The mean time between critical failures is projected to be greater than 15,000h and, because performance calculations assume a certain percentage of the solid-state transmit/receive modules have failed, "it is unlikely you would change any during the life of the aircraft", he says.

Integrated system

Of all the Block 2 upgrades, incorporating the AESA requires the most changes to the aircraft, and is enabled by the ECP 6038 forward-fuselage redesign. This prevents retrofit of the active-array radar to F/A-18s produced prior to Lot 26. The environmental control system is uprated to provide liquid cooling to the array, which receives power from an upgraded electrical system. The fibre-optic network is needed to carry the radar data, and more powerful mission computers are needed to run the additional software.

"This is a highly integrated system," says Pingsterhaus. In addition to the array and its liquid cooling system, there is a new wideband radome, and modifications to the radar warning receiver (RWR) and jamming suite are required to ensure compatability. Because of the AESA's importance, development work began under Boeing and Raytheon funding in 1999, in advance of navy funds becoming available early this year. "We have already built a lot of hardware," including modules, subarrays and radomes, he says. "We have really reduced the risk in the programme."

Flight testing is to begin in the second quarter of 2003, with production deliveries beginning early in 2005. In the first year of production (Lot 27), only eight of 48 E/Fs built will receive APG-79s, the rest being fitted with APG-73s. Full-rate production is to begin in 2007 (Lot 30). Around 280 US Navy Super Hornets will be fitted with AESAs during production, with retrofit bringing the total to around 400 out of the 548 aircraft planned.

AESA developer Raytheon is also supplying the ASQ-228(V) ATFLIR, a third-generation targeting pod that replaces three pods now carried by the F/A-18. The intake-mounted pod houses a mid-wave infrared, electro-optical camera and both tactical and eye-safe training laser rangefinder/designators, all sharing a common optical path in a gimballed sensor head. There is also a separate laser spot tracker and a navigation FLIR in the pod adapter.

Early operational capability of the ATFLIR is scheduled for the first E/F fleet deployment in June next year, with a combination of three refurbished development and three pre-production pods, says Boeing ATFLIR programme manager Keith Smith. Compared with the current targeting FLIR, range is improved "four to five times", he says. "The laser is improved by the same margin, plus it operates at higher altitude and is more reliable."

The self-protection suite on the Block 1 Super Hornet - IDECM Block 1 - comprises the Raytheon ALR-67(V)3 RWR, Northrop Grumman/ITT ALQ-165 onboard jammer and Raytheon towed decoy. The full-up IDECM Block 3 will come with the Block 2 aircraft, and includes the Northrop Grumman ALQ-214 techniques generator and associated ALE-55 fibre-optic towed decoy. Whereas the ALE-50 simply repeats the received signals, the ALE-55 transmits signals generated on board the aircraft by the ALQ-214.

The backbone of the Block 2 upgrade is the advanced mission computer and displays. F/A-18C/Ds and initial E/Fs have dual AYK-14 mission computers with limited throughput and assembly-language software which is costly to maintain. Under its Bold Stroke initiative Boeing has been developing and testing mission computers based on commercial technology, and the dual AMCs for the Super Hornet will use PowerPC processors with increased throughput, the Fibre Channel high-speed data network and software written in C++ , a high-order language (HOL) easier to use, test and maintain, the company says.

The advanced mission computer, supplied by General Dynamics Information Systems, will be developed in two stages. The AMC Type 1, in Block 1 aircraft, will begin the transition to HOL software, running the existing operational flight programme (OFP) translated from assembly language to C++. Later OFPs will expand combat capability and integrate Block 2 components. "Commercial software tools, such as compilers, result in big savings," says Rob Deadrick, programme manager, F/A-18E/F advanced mission computer and displays. "We are seeing tremendously faster integration. It is taking half the time to dissect and fix problems - and we can use college graduates to produce software."

The AMC Type 2, in Block 2 aircraft, will use a much faster PowerPC G4 processor, but the new mission computer architecture isolates the software from hardware changes. This allows development of software modules, such as the navigation function, which can be reused between platforms. The compartmentalised, or object-oriented, software design also increases programmer efficiency and simplifies regression testing, Deadrick says.

Additionally, the upgrade involves replacing the obsolete cathode-ray tube (CRT) multi-purpose displays with 130 x 130mm liquid crystal displays (LCDs) and, in Block 1 aircraft, replacing the moving-map display with a 150 x 150mm projection CRT, also because of obsolescence. At the same time, the cockpit displays are removed from the aircraft's 1553 databus to provide loading relief. The next step, in Block 2 aircraft, is the introduction of a fibre-optic data network with 1,000 times the capacity of 1553.

Deadrick says the need for a high-speed network is driven by the amount of data generated by the AESA and the desire to provide growth for high-resolution digital video. The fibre-optic network in the Block 2 Super Hornet will handle 1Gbyte/s of data and video. Harris is supplying the dual-redundant Fibre Channel network switches, with the capacity to link up to 16 systems, including the AESA, ATFLIR, SHARP reconnaissance pod, IDECM, mission computers, digital video map computer and the 200 x 250mm display in the F-model aft cockpit. "The fibre-optic network is an enabler for the AESA, and is required for the 8 x 10 [200 x 250mm] display," he says.

Operator functionality

The two-seat F/A-18F is the US Navy's intended replacement for the Grumman F-14 in both air superiority and precision strike roles. This requirement, and the potential for high crew workload in poor weather and dense threats, generated the need for decoupled cockpits enabling near-simultaneous air-to-air and air-to-ground capability. "The key driver is the need for increased operator functionality. The aft cockpit does not have a lot of functionality now," says Lana Lechner, programme manager, F/A-18E/F advanced crew station.

A complete redesign of the aft cockpit is made possible by the new ECP 6038 forward fuselage. This allows the 200 x 250mm situational awareness display to be located in the centre of the instrument panel, flanked by two multi-purpose displays and with the upfront control panel for data entry relocated above the glareshield. There are new hand controllers, handles to grab during electronic-countermeasures manoeuvres and push-to-talk footswitches for the intercom. Using the hand controllers, the rear-seat weapon system operator can select radar modes, arm the laser rangefinder/designator, launch air-to-air weapons, release air-to-ground munitions and control the IDECM self-protection suite.

The 200 x 250mm LCD replaces the 150 x 150mm projection CRT in Block 1 aircraft. "The increased display size provides 30% more look-ahead area, which improves situational awareness," says Lechner. The larger display also provides higher resolution to support digital sensors, including the AESA, ATFLIR and SHARP. To drive the display, the TAMMAC moving map is upgraded with the DVMC digital video map computer and fibre-optic network interface, which provides the capability to drive independent maps in the front and rear cockpits, she says.

Initially, the operator will be able to scroll through five formats on the display, Lechner says: horizontal situation, situational awareness, electronic warfare, ATFLIR video and AESA SAR. In addition, the two multi-purpose LCDs will provide simultaneous air-to-air and air-to-ground radar displays. Physical changes will be introduced with the first Block 2 aircraft, but advanced crew station capabilities will be phased in as systems become available, and be fully functional by Lot 28 in 2005.

With development of the Block 2 Super Hornet well under way, thoughts are turning to a "Block 3" upgrade. Boeing vice-president F/A-18 Tony Parasida identifies reduced signature as one area of interest. "We could put the ATFLIR in the nose. That would reduce radar cross-section," he says. Whatever is decided, the Super Hornet structural upgrade has provided a platform for further development of the F/A-18. "The aircraft will be around to 2020. There will be future threats, but now there is room for growth," he says.

Source: Flight International