EXCLUSIVEFLIGHT TEST REPORT

72 February 2014 www.combataircraft.net

THOUGH THE BOEING Company has been extremely reticent to talk about the F-15SA program at all, Combat Aircraft has learned that the three-aircraft F-15SA test fleet

has moved to Palmdale, California, to begin a new phase of flight test operations. The three prototype F-15SAs flew to their new home on November 1, leaving behind the security of operating from the factory airfield as they departed from the company’s facility at Lambert-St Louis International Airport, Missouri.

The F-15SA is the newest and most advanced production variant of the combat-proven Eagle, providing improved performance and increased survivability at a lower life-cycle cost than existing variants. Based on the multi-role, two-seat F-15E Strike Eagle, the F-15SA builds on the enhanced F-15K and F-15SG variants built for South Korea and Singapore respectively, adding further features and capabilities. A mark of the F-15SA’s advanced nature lies in the fact that its avionics and systems are largely the same as those adopted for

Boeing’s stealthy F-15SE Silent Eagle. Consequently, the new Saudi Advanced Eagle is in many ways more capable and more sophisticated than any of the US Air Force’s own Eagles, though the F-15E Radar Modernization Program will add a refined version of the F-15SE’s AN/APG-63(V)3 active electronically scanned array (AESA) radar in the shape of the AN/APG-82(V)1, which incorporates technology from the Super Hornet’s AN/APG-79, and allows the Strike Eagle’s radar and electronic warfare system to function simultaneously.

Saudi Arabia has ambitious plans to upgrade and modernize its armed forces, and, according to some sources, such as the Washington Post’s David Ignatius, the Saudis will ‘roughly double their armed forces over the next 10 years’, predicting an air force expansion of about 400-500 new aircraft. Never keen to put all of its air power eggs in the basket of a single seller, it was always inevitable that Saudi Arabia would augment its 72 Eurofighter Typhoons (whose purchase was announced in August 2006) with another fighter type. Moreover, and despite reports of Saudi interest in the Dassault

Rafale, it was always likely that the Saudis would want to turn to the US to complement the European Typhoon, which was purchased via a government-to-government deal between the UK and Saudi Arabia.

Why F-15SA?The Saudi F-15SA requirement, which covered more than 150 aircraft, including upgrades, formed the centerpiece of the Royal Saudi Air Force F-15 Fleet Modernization Program and represented potentially the most valuable Foreign Military Sale to date.

With the F-22A not cleared for export, and the F-35A similarly ‘off limits’ and further hindered by being unlikely to be available in time to meet Saudi timescales, Saudi Arabia’s attention soon settled on an advanced version of the F-15. The Eagle was already in service with the RSAF in fighter (F-15C and F-15D) and strike fighter (F-15S) forms, and was heavily pushed by the US side, not least since a substantial Saudi order promised to save the type’s production line from closure following the completion of orders for Korea and Singapore.

In an exclusive first for Combat Aircraft, we present the most detailed description to date of the F-15SA, its genesis and its test program. The F-15SA is the most advanced Eagle flying today — superior in some respects even to the US Air Force’s examples.

report: Jon Lake

Complete with ‘Fly-By-Wire’ titles under the cockpit, one of the three F-15SAs engaged in the current flight clearance trials returns to Palmdale in December. Dan Stijovich

F-15SA SAUDI ADVANCED EAGLE

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Initially, the US offered an F-15S+ configuration, with Link 16 capability, Sniper targeting pods and F110 engines, and with the AN/APG-63(V)1 radar, like that fitted to the South Korean F-15K Slam Eagle. The APG-63(V)1 features a fully digital back end, married to a mechanically scanned array. This would give a performance improvement over the baseline APG-70 radar and would see the prospect of adding an AESA antenna array at a later date. This proved to be too modest a proposal for Saudi Arabia.

It is believed that Boeing, seeking a launch customer for its stealth-modified F-15SE Silent Eagle, hoped to sell the aircraft to Saudi Arabia, though in the end this advanced low-observable Strike Eagle derivative was not offered to (or possibly was not selected by) the RSAF. This may have been due to growing US sensitivity over the export of advanced and sensitive technologies, reflected in an ever more stringent and cumbersome International Traffic in Arms Regulations regime, or specific concerns about exporting the aircraft to Saudi Arabia — perhaps primarily driven by the Israeli lobby, which has historically

limited the military capabilities exported to that nation’s Arab neighbors.

Certainly Israel would have found a stealthy long-range strike aircraft (perhaps armed with stand-off precision-guided munitions) in the hands of one of the most powerful Arab nations in the region a bitter pill to swallow. There are numerous examples of weapons systems deemed as being ‘not conducive to regional stability’ — often shorthand for ‘problematic for Israel or its friends in Congress’ — being withheld from Arab customers. Such systems included conformal tanks for the original Saudi F-15S, whose radar also had to be downgraded to appease Israeli sensitivities, with a detuned Doppler beam-sharpening capability giving an effective reduction in resolution (to about one third of that enjoyed by USAF F-15Es) and range.

But some believe that, rather than being withheld, the fully-modified stealthy F-15SE may have been viewed by the Saudis themselves as unnecessary, unproven, and perhaps not cost-effective. Others speculate that the Saudis may have been offered the choice between the F-15SE’s low-observable

features, including internal weapons carriage, or a non-stealthy version of the aircraft armed with advanced long-range stand-off weapons systems like the Boeing AGM-84K SLAM-ER.

With budgetary pressures forcing the US to reduce its own permanent military presence in the region and driving it to ‘burden-share’ with its regional allies, giving those allies the tools to do the job gained a greater imperative. Given a resurgent Iranian threat, an AESA-equipped F-15SA promised to allow the RSAF a far higher level of interoperability with US air forces, and better-tailored capabilities for dealing with small, dispersed target sets — exemplified by the dispersed elements of Iran’s Islamic Revolutionary Guards Corps (IRGC) and for the kind of asymmetric warfare required for combating rebels, insurgents and non-state actors like the Houthis or al-Qaeda in the Arabian Peninsula (AQAP) on the Yemeni border.

Accordingly, on October 20, 2010 the Defense Security Co-operation Agency notified Congress of a possible Foreign Military Sale to the government of Saudi

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Arabia of 84 new-build F-15SAs (together with the conversion of 70 existing RSAF F-15S aircraft to the same standard) and a package of weapons and equipment items for the aircraft. The US Congress approved the $29.4-billion package in 2010 and President Obama signed the agreement in 2011.

The DSCA notification gave an early glimpse of the advanced nature of the F-15SA, since it revealed many of the aircraft’s planned systems and weapons, including the Raytheon AN/APG-63(V)3 AESA radar — the most advanced radar for export F-15s. The new F-15SAs would be powered by General Electric F110-GE-129 Increased Performance Engines (IPE) and would also feature the BAE Systems DEWS (Digital Electronic Warfare System), JHMCS (Joint Helmet-Mounted Cueing System) helmets, Lockheed Martin AN/AAQ-33 Sniper surveillance and targeting pods and AN/AAS-42 Tiger Eyes IRST (infra-red search and track) pods, as well as LANTIRN navigation pods. The weapons package notified to Congress included AGM-84 Harpoon Block II anti-ship and surface-attack missiles, AGM-88 HARM anti-radiation missiles, GPS-guided Joint Direct Attack Munition (JDAM) bombs and CBU-105 cluster bombs, dual-mode laser/GPS-guided bombs, as well as DB-110 electro-optical reconnaissance pods.

On December 24, 2011, after some analysts had predicted a looming F-15 production gap, Saudi Arabia signed a $29.4-billion letter of acceptance (LOA) to buy 85 new F-15SAs and upgrade 70 existing F-15S Strike Eagles, as well as all of

the accompanying weapons named in the original DSCA notification, together with a 10-year support and training package for some 5,500 Saudi personnel that would run through to 2019. The latter was originally expected to include a CONUS-based training unit at Mountain Home AFB, Idaho, using 12 of the aircraft.

The formal order for the 84 new-build F-15SAs was placed in March 2012, while a contract for the conversion of 68 F-15S aircraft to F-15SA standards was placed on June 26, 2012 — two of the original 70 F-15S airframes having been lost in the interim. This contract, initially valued at $1.837 billion (covering an initial work package only), was subsequently amended on November 2 to $4 billion and again on March 14, 2013 to $3.544 billion.

The conversion contract included Country Standard Time Compliance Technical Order (CSTCTO) development, CSTCTO integration and testing, the fabrication of trial kits to support validation and verification activities, and the procurement and installation of four base stand-up kits.

The conversion kits were naturally to be accompanied by the appropriate sensors and other equipment items whose installation and integration costs were included in the fighter upgrade contract, but whose purchase cost was included in the new-build contract.

In addition to the Raytheon APG-63(V)3 AESA radar, Lockheed Martin AN/AAS-42 IRST, BAE Systems DEWS, and further systems listed in the original DSCA notification, the F-15SA has two more underwing weapons stations and a digital

fly-by-wire (FBW) flight control system (FCS).

The ‘new’ weapons stations use hardpoints that were designed into the F-15’s wing from the beginning, though Stations 1 and 9 are long dormant, having never been used in service.

The pylons were originally introduced on the F-15A, being intended for planned TEWS (Tactical Electronic Warfare System) pods. According to some versions of the story, the design requirements for the TEWS changed very early during the initial test program, and the sensors that had been intended for the outboard stations were dropped. Others have it that the outboard TEWS pods destabilized the F-15 in pitch to the extent that the original control systems would not have been able to maintain Level 1 flying qualities in a major part of the envelope in the event of any failure to the F-15’s analogue Control Augmentation System (CAS), which the USAF deemed unacceptable.

Digital fly-by-wireIn addition to conferring a really significant reduction in maintenance compared to the mechanical FCS of the original F-15, the new digital fly-by-wire FCS allows for greater flexibility in tailoring control laws for specific flight conditions, loadings, and tasks. It permits Stations 1 and 9 to be re-activated and used for the carriage of a range of weapons and stores, though it represents a major modification to what is otherwise a tried, tested and mature airframe, and one which will require a significant test and certification effort.

This photo and bottom right: The F-15SA builds on the enhanced F-15SG and F-15K variants built for Singapore and South Korea. Jamie Hunter and Gordon Arthur

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software program using time-consuming table look-ups, and then letting the computer decide which control surfaces should be used, for how long at a time, at what deflections, in order to satisfy the pilot control input of rate and/or acceleration’. This ambitious philosophy has ‘never been used on an airframe with so many different loading options, Mach number regimes, and high angles of attack. A similar philosophy was used on the Boeing X-32 with almost disastrous results!’, the source said.

The new FCS has reportedly already made the Eagle a nicer aircraft to fly, but means that Boeing and the USAF will have to re-certificate the F-15SA’s FCS over the entire flight envelope. This airworthiness testing and certification effort will take approximately 18 months to achieve.

An apparent new capability for the Eagle was unveiled in a Pentagon announcement of November 27, 2013, relating to a $15.5-million firm-fixed-price contract modification for the procurement of a disorientation recovery function capability on the F-15SA. Work will be performed in St Louis.

Flight-testingThe new F-15SA and its fly-by-wire FCS made their maiden flight on February 20, 2013, after completing first taxi tests

on February 15. The inaugural flight announcement was not made until March 13, some three weeks later.

The aircraft used for the landmark first flight was actually the second of three instrumented F-15SAs that are serving as prototypes, SA-2 (serial 12-1002). It was flown on the day by pilot Joe Felock, with Mark Snider in the rear cockpit.

The USAF and Boeing said that the sortie had gone as planned, meeting all the test objectives required in order to support the aircraft’s on-schedule development. The first test aircraft, SA-1 (serial 12-1001), followed on March 2.

The three airframes will each have individual responsibilities within the flight test program. SA-1 will be used for weapons testing, SA-2 for flutter and aerodynamics, and SA-3 for electronic attack and awareness testing.

The first two F-15SAs (which subsequently received high-conspicuity dayglo orange markings in a very similar design to those applied to the first F-15As in the early 1970s) are heavily instrumented pre-production aircraft, whereas SA-3 is in the production configuration and does not have so much flight test instrumentation.

Combat Aircraft understands that all flight-Combat Aircraft understands that all flight-Combat Aircrafttesting was put on hold after the first week of April 2013 due to engineering issues with the digital FBW FCS. A ‘stand-down’

The original F-15 has a hybrid control system, with a conventional hydro-mechanical FCS, and an analog dual-channel, high-authority, three-axis FBW control augmentation system superimposed. The F-15E’s system is similar, but with a quadruplex CAS.

Boeing has progressively moved closer and closer to a fully fly-by-wire FCS. The ‘legacy’ F/A-18 Hornet FCS is a quadruplex digital Control Augmentation System with a reversionary Direct Electrical Link and a mechanical link to the stabilator surfaces only.

The F-15SA uses an innovative all-digital FCS, taking advantage of Boeing’s experience from a number of previous FBW flight control systems, including those of the experimental F-15 STOL/MTD (Short Take-off and Landing/Maneuver Technology Demonstrator) and its unsuccessful Joint Strike Fighter contender, the X-32. The new system is a full-authority digital FCS, with no mechanical back-up. It uses a mix of dual and quadruplex channels, depending on the criticality of the particular function. It employs a new control law philosophy, according to one program source, ‘dumping everything known about the aerodynamics of the airframe and controls, weight and inertia characteristics, etc into a computer

Shadows of the past — YF-15A serial 71-0280 seen during testing in 1972 wearing the same high visibility markings as carried on the F-15SA test aircraft. USAF

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was always planned for further control-law development, system ground tests, and simulations, but some sources suggest that it occurred earlier and went on for rather longer than expected, and that envelope expansion with the new FCS was slower than anticipated. At one stage there was even a very modest 10kt crosswind limit.

Despite this hiatus, Boeing ceremonially rolled out the first F-15SA for the Royal Saudi Air Force at St Louis on April 30, 2013. The ceremony was attended by an array of VIPs, including Dennis Muilenburg, Boeing Defense, Space and Security president and CEO, and Lt Gen Mohammed Bin Abdullah Al-Ayeesh, commander of the RSAF.

The F-15SA began a final series of test flights from St Louis on October 16, 2013, when SA-2 made a flight of about 1.2 hours, accompanied by a Boeing F/A-18F Super Hornet chase ’plane. This magazine understands that the flight was ‘a complete success’, and that the aircraft completed 35 test points. All flying qualities were rated Level 1, and a couple of points apparently received Cooper-Harper ratings of 1, the best possible rating on this 10-point scale.

Pilot Joe Felock reportedly said that the aircraft ‘handled better than the simulator’ and gave the up-and-away control laws particular praise, especially during a series of air-to-air tracking tasks. The sortie was followed by a planned data review day

during which the team looked at the post-processed on-board data to ensure there were no anomalous characteristics. Flying resumed on Friday, October 18 with SA-2 (accompanied by an Aero L-39ZA Albatros in the livery of the Bulgarian Air Force, leased from Air USA). SA-1 then flew on Saturday and SA-3 on Sunday. The plan was to fly every day, weather and aircraft permitting, and to complete nine sorties by October 28 (joined either by the L-39 or Boeing’s own Northrop T-38A Talon). This was in order to support the planned transfer to Palmdale, originally scheduled for October 30, but actually undertaken two days later on November 1.

The three aircraft departed Lambert Field along with Boeing’s T-38A chase aircraft. Less visibly, a Boeing engineering team is also going to Palmdale for the testing. This team was described by one industry insider as being ‘top-notch’. ‘If anyone can make the F-15SA control laws work as intended, these guys can’, he added.

Transferring flight test activities to Palmdale is not unusual; indeed, the first F-15SG for Singapore was also sent to Palmdale after making its first few flights from St Louis in 2008-09. This is partly down to the fact that as a US government Foreign Military Sales (FMS) program, with the USAF in control, the F-15SA is effectively an Air Force program with Boeing as sub-contractor.

Air Force Plant 42 at Palmdale (which is ‘owned’ by Detachment 1, Aeronautical Systems Center, based at Wright-Patterson AFB, Ohio) has long been a home to advanced and classified test programs. It is perhaps worth noting that the Air Force Life Cycle Management Center at Wright-Patterson AFB is the USAF’s decision authority for the F-15SA program.

Palmdale is ideally situated to make use of the vast Edwards and Nevada test ranges, whereas the airspace around St Louis is busy and constrained. It was always planned that major testing of the F-15SA would be undertaken at the Palmdale/Edwards complex, following the initial flights and a period of further control-law

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development, system ground tests, and simulations.

Palmdale will be home to the aircraft as they undertake critical and higher-risk flight tests including flutter testing, SMI (structural mode integration), stores separation, and flight at high angles of attack, as well as with a variety of external stores. Soon after its arrival at Palmdale, SA-1 was fitted with a prominent nose-mounted test instrumentation boom, while SA-2 was noted flying without its conformal fuel tanks.

Testing is expected to continue for about another year. New-build aircraft deliveries to Saudi Arabia are scheduled to begin in early or mid-2015 and will conclude by 2019.

The first two F-15S-to-F-15SA upgrades will be undertaken at the Boeing facility in St Louis, with this first phase ending by the end of December 2015, before the upgrade’s second phase begins in 2016. Interestingly, the original announcement said that four conversions would be undertaken at St Louis, not two.

The remaining 66 aircraft will be converted in Saudi Arabia by the Alsalam Aircraft Company in Riyadh. Originally set up as part of a Boeing offset arrangement, this concern received a $33.1-million firm-fixed-price contract on September 26 to set up the required facility, develop manufacturing plans and schedules, and ready automated performance-reporting tools.

Alongside the manufacturing effort, Boeing and the USAF are establishing a major training program, updating Saudi Eagle training at King Khalid Air Base (KKAB) in Khamis Mushayt to reflect the F-15SA’s new features, and providing ‘differences training’ both for the initial cadre of RSAF pilots and maintainers moving over from other F-15 models, and the first group of USAF aircrew supporting the F-15SA program. The current plan is to train up to six USAF crews and six RSAF crews in September-October 2014, prior to the start of aircraft deliveries to KKAB in January 2015. Up to four additional instructor crews may be trained in the January-March 2015 timeframe.

Powerful arsenalThe new Saudi Eagles will have an impressive array of air-to-ground weapons, including 1,000 Mk82 500lb general-purpose (GP) bombs, 6,000 Mk82 500lb inert training bombs, 2,000 Mk84 2,000lb GP bombs, 2,000 Mk84 inert training bombs,

1,000 500lb and 1,000 2,000lb Lockheed Martin Dual-Mode Laser/GPS-Guided Bombs (DMLGB), 1,100 2,000lb GBU-24 Paveway III laser-guided bombs, and 1,000 GBU-31B(V)3 2,000lb Joint Direct Attack Munitions (JDAM) GPS/INS-guided bombs. There will also be 1,300 CBU-105D/B Sensor Fuzed Weapons (SFW)/Wind Corrected Munitions Dispensers (WCMD). To this package of weapons authorized in 2010 will be added 400 AGM-84L Harpoon Block II missiles, 650 AGM-84H SLAM-ER cruise missiles, 973 2,000lb AGM-154C Joint Stand-Off Weapons (JSOW), and 1,000 250lb GBU-39/B Small Diameter Bombs (SDB).

The F-15SAs will have 10 UTC Aerospace Systems (Goodrich) DB-110 dual-band reconnaissance pods, though eight F-15S airframes are being upgraded to use these in the interim under a specific contract to meet an urgent requirement for a limited integration of the system.

The existing Saudi F-15C/D fleet is not being upgraded, and will be retired — replaced, together with the already withdrawn F-5E/F Tiger IIs, by a mix of Typhoons and F-15SAs. Unit designations for the new F-15SA units are unknown, though it is assumed that the existing F-15S squadrons will re-equip with new-build and upgraded F-15SAs.

The first squadron is likely to be the 17th, a former F-5E unit that was once expected to be the third RSAF Typhoon operator.

Wider importanceThe F-15SA has significance beyond Saudi Arabia. For the US, the F-15SA program safeguards Boeing’s St Louis manufacturing facility, giving the US a second fighter line beyond the F-35 production line at Fort Worth, Texas. It also gives the US another exportable fighter — invaluable in areas where the F-35 cannot yet be offered for export, and where the F-16 or F/A-18E/F might not be quite what a customer is looking for.

Upgraded F-15 variants essentially similar to the F-15SA are contenders in a number of fighter competitions, especially within the Middle East and Gulf, and accordingly the F-15SA development program is the focus of great interest.

Forty-three years after the YF-15A made its maiden flight, the Eagle (albeit in modernized and improved form) remains a viable and competitive fighter, and one near the top of many nations’ wish lists.

This photo: The existing F-15S fleet will be upgraded to F-15SA standard under the new

Saudi deal. USAF

Below: The F-15SA incorporates several advanced features that the USAF has

embodied into its Strike Eagles, such as the Joint Helmet-Mounted Cueing System.

Jamie Hunter

Bottom right: Soon after arriving at Palmdale, SA-1 was fitted with a nose-mounted test

instrumentation boom. Dan Stijovich