Back to home pageHistory & Development of the Boeing 737 - NGs

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Contents

Illustrated technical information covering Vol 2 Over 800 multi-choice systems questions Study notes and technical information Close up photos of internal and external components A compilation of links to major 737 news stories with a downloadable archive Illustrated history and description of all variants of 737 Detailed tech specs of every series of 737 Databases and reports of all the major 737 accidents & incidents General flightdeck views of each generation of 737's Description & news reports of Advanced Blended Winglets Press reports of orders and deliveries Articles from the press and official sources following the troubled history of the rudder PCU Details about 737 production methods A compilation of links to other sites with useful 737 content Get the book of the website A quick concise overview of the pages on this site

History & Variants

Select a version:

Originals:

100 | 200 | 200Adv | 200C / QC | T43A | Surveiller

Classics:

300 | 400 | 500

NGs:

600 | 700 | 800 | 900 | BBJ | C-40 | AEW&C | MMA | SIGINT

Max:

-7 | -8 | -9

 

Click here for technical specifications of all versions

See more details about the book

All of the information, photographs & schematics from this website and much more is now available in a 360 page printed book or in electronic format.

*** Updated 15 Oct 2014 ***

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Next Generation

The Boeing 737-X programme was launched on 29 June 1993, with a 63 aircraft order from Southwest Airlines for the 737-300X. This became the 737-700, 22cm (9in) longer than the original 737-300, seating up to 149. The main differences of the 737 Next Generation (NG) are as follows:

  • Performance: Faster cruise M0.78, Higher ceiling 41,000ft, Lower take-off & approach speeds, Higher MTOW, lower fuel burn.
  • Engines: FADEC controlled CFM56-7, 2.5deg nozzle tilt, redesigned struts, improved nacelles with increased airflow and improved noise treatment, 7% more fuel efficient than CFM56-3.
  • Fuselage: Strengthened for increased tail loads and design weights, new wing-body strake.
  • Wings: New airfoil section, 25% increase in area, 107" semi-span increase, 17" chord increase, raked wing-tip, larger inspar wingbox with machined ribs.
  • Fuel Tanks: Main tanks smaller at 3900kg each but centre tank much larger giving total fuel capacity of 20,800kg. (compared to 16,200kg on classics).
  • Tail: 4ft 8in taller, 60 sq ft root insert, modified rudder, segmented rudder seals, digital yaw damper.
  • Flight Controls: Increased elevator PCU capability, aileron and tab span increase, new double slotted continuous span flaps, new leading edge Krueger flaps, additional slat, additional spoiler.
  • Nose Gear: Stroke increased 3.5" to relieve higher dynamic loads and wheelwell extended 3" forward.
  • Main Gear: Longer to reduce tailstrike risk, one piece titanium gear beam, 43.5" tyres, digital antiskid.
  • Flightdeck: 6 programmable LCD's, replacing EFIS CRT displays and most conventional instruments.
  • Systems: Most systems developed particularly: electrics, powerplant & navigation.

The NG's have 33% fewer parts than the Classics which reduces production time. One of the main production differences with the NG is the single moving assembly line, this has the capacity to produce 21 aircraft a month with a flow time of just 13 days.

In April 2009 Boeing announced a series of planned improvements to the 737, which they say “will result in a 2% decrease in fuel burn and a marked upgrade in cabin comfort and utility.” The fuel improvements come partly from the new CFM56-7BE engine (see powerplant) the first of which was delivered in July 2011; and partly from various airframe drag-reduction improvements such as: refined wing control surfaces, redesigned wheel-well fairing, a re-shaped anti-collision light and an ECS inlet/exhaust modulation.

 

737 NG Key Dates:

17 Nov 1993: Boeing directors authorize the Next-Generation 737-600/-700/-800 program. Southwest Airlines launches the -700 program, with an order for 63 aircraft.

5 Sep 1994: The 737-800 is launched at the Farnborough Air Show.

15 Mar 1995: The 737-600 is launched with an order for 35 from SAS.

9 Feb 1997: The first Boeing 737-700 makes its maiden flight, with Boeing Capts. Mike Hewett and Ken Higgins at the airplane's controls. At 10:05 a.m. PST, the aircraft took-off from Renton Municipal Airport. After heading north over Lake Washington, the pilots flew north over Tattoosh, east to Spokane and then back to Western Washington before landing at Boeing Field in Seattle.

15 Mar 1997: The 737-700 reaches an altitude of 41,000 feet, flying higher than any other 737 in aviation history. Flying up to speeds of 0.81 Mach, Boeing Capts. Mike Carriker and Paul Desrochers fly the second 737-700 flight-test airplane to its new altitude during certification testing for climb and descent. 

1 Apr 1997: The last 737-700 flight-test airplane makes its first flight at 10:55 a.m. and lands 1 hour and 47 minutes later at Boeing Field.

22 Apr 1997: YA001, the first 737-700, makes its 100th flight weighing 172,900 pounds -- the highest Boeing 737 takeoff weight ever -- and with an engine thrust of 27,000 pounds. During the flight the airplane conducts pre-certification flight testing to capture data for the 737-700 Increased Gross Weight (IGW) airplane. Commenting on the flight, Capt. Mike Hewett said the airplane's wings performed exceptionally well and "the stability control data points looked very good for the flight-test conditions."

31 Jul 1997: The 737-800 makes its first flight, with Boeing Capts. Mike Hewett and Jim McRoberts at the airplane's controls. At 9 a.m. PDT, the 129-foot, 6-inch 737-800 takes off from Renton Municipal Airport in Renton, Wash. After heading north over Lake Washington, the pilots fly north to the Straits of Juan de Fuca and conduct a series of flight tests between there and Tatoosh. Three hours and five minutes later, the airplane lands at Boeing Field, Seattle.

3 Sep 1997: Boeing launches the 737-700C with an order for two from the U.S. Navy. The Navy calls the model, a cargo version of the 737-700, the C-40.

7 Nov 1997: The 737-700, earns type certification from the U.S. Federal Aviation Administration (FAA). The certification formally recognizes that the newest 737 airplane has passed all the stringent testing requirements mandated by the FAA and is ready to enter passenger service.

10 Nov 1997: Alaska Airlines announces an order for 10 737-900s and 10 options, launching the series. The aircraft is the longest 737 built, with a length of 138 feet 2 inches.

8 Dec 1997: Exactly a year to the date after the world premier of the first Next-Generation 737-700, the first 737-600 rolls out of the Renton factory. The ceremonial event marks the manufacturing completion of the 102-foot-6-inch airplane -- the smallest member of the Next-Generation 737 airplane family. The airplane will be the first of three 737-600s that will participate in the 737-600 flight testing and certification program.

17 Dec 1997: Boeing delivers the first 737 NG - a 737-700 to launch customer Southwest Airlines. The event is marked by a brief ceremony at Boeing Field. The airplane later departs for Love Field in Dallas, Texas.

22 Jan 1998: The Boeing 737-600 makes its first flight.

19 Feb 1998: Europe's Joint Aviation Authorities (JAA), which comprise the aviation regulatory authorities of 27 countries, recommends type validation of the 737-700. The individual countries will award actual type certificates.

13 Mar 1998: The 737-800 earns FAA type certification. JAA follow suit on 9 Apr 1998.

14 Aug 1998: The 737-600 earns FAA type certification. JAA follow suit on 10 Sep 1998.

1 Sep 1999: 737 NGs are certified for 180 minute ETOPS Operation.

11 Oct 1999: Boeing launches a second Boeing Business Jet model, the BBJ-2, a modified version of the Next-Generation 737-800.

14 Feb 2000: Aloha Airlines begins first 180-minute ETOPS service, introducing Nonstop service between Honolulu and Oakland, Calif.

27 Jan 2000: The 737 becomes the first jetliner in history to pass 100 million flight hours.

18 Feb 2000: Boeing announces availability of advanced technology "blended" winglets as an option on Next-Generation 737-800.

14 Apr 2000: First flight of the 737-700C.

3 Aug 2000: First flight of the 737-900. Flight-test program begins.

26 Sep 2000: First flight of the 737 with blended winglets.

17 Apr 2001: The 737-900 earns FAA type certification. JAA follow suit on 19 Apr 2001.

8 May 2001: "Blended" winglets make their world debut in revenue service with German carrier Hapag-Lloyd Flug.

17 Sep 2001: BBJ adds Flight Dynamics' latest head-up guidance system.

2 Nov 2001: Boeing delivers first Next-Generation 737-700 Convertible with Quick Change options.

19 Mar 2002: Boeing introduces the Technology Demonstrator airplane, a 737-900 outfitted with a suite of new and emerging flight deck technologies to assess their value for enhancing safety, capacity and operational efficiency across the Boeing fleet of airplanes.

9 Sep 2002: Boeing Business Jets announced the availability of a lower cabin altitude modification for BBJ operators. The new feature will offer 6,500-foot cabin altitude instead of the standard 8,000-foot cabin, providing passengers with an improved level of comfort.

31 Oct 2002: Rollout of the 737 AEW&C - "Wedgetail".

28 Jan 2003: Boeing delivers a suite of three leading-edge display and flight management software for the 737. The new flight-deck technologies, which include the Vertical Situation Display (VSD), Navigation Performance Scales (NPS) and Integrated Approach Navigation (IAN), promise to reduce flight delays and enhance flight-crew efficiency.

13 Jun 2003: The Next-Generation 737 fleet surpasses 10 million flight hours within five years of entering service, a record and a feat equal to one airplane flying more than 1,141 years nonstop.

12 Oct 2004: Boeing Electronic Flight Bag available for retrofit on BBJ. Boeing is offering an avionics-installed "Class 3" version of the EFB comprising Jeppesen software and data, and electronics and display hardware from Astronautics Corp. of America.

5 May 2004: First talk of a replacement for 737NG - the Y1

21 May 2004: First flight of the 737 AEW&C - "Wedgetail". Flight-test program begins.

24 May 2004: A BBJ completes the first North Atlantic flight by a business jet equipped with the advanced Future Air Navigation System (FANS), a system that streamlines communication between airplane crews and air-traffic controllers.

14 Jun 2004: The U.S. Navy awards The Boeing Company a System Development and Demonstration contract worth $3.89 billion for 109 of the Multi-mission Maritime Aircraft, which is based on the 737-800.

24 Jan 2005: The first Next-Generation 737 without "eyebrow" windows rolled out of Renton. The first eyebrowless aircraft was 737-700, N201LV, L/N 1650, first flown on 3 Feb 2005 and was delivered to Southwest 16 Feb 2005.

12 May 2005: 737NG First airliner to be certified for Cat I GLS approaches.

18 July 2005: 737-900ER Launched.

31 Jan 2006: Boeing launches 737-700ER

26 Jan 2006: Boeing Announces 737 Signals Intelligence aircraft

13 Feb 2006: Delivery of the 5,000th 737.

1 Feb 2007: FAA certification of the 737-700ER.

20 Apr 2007: FAA certification of the 737-900ER.

1 Aug 2008: First 737 delivered with carbon brakes to Delta Air Lines on a 737-700.

16 Apr 2009: Boeing delivers its 6,000th 737 to ILFC and operator Norwegian Air Shuttle.

27 Apr 2009: First flight of P-8A Poseidon.

21 July 2011: Delivery of the first 737 with 7BE engines.

Click for technical specifications

 

 

737-600

FF 22 Jan 1998

68 built.

The 737-600 was the third of the NG's to be built and originated as the 737-500X with a similar length fuselage, seating between 108-132. The launch order came from SAS on 15 March 1995. The fuselage is essentially that of the -700, with two plugs of 1.37m (fwd) and 1.01m (aft) removed giving an overall length of 31.2m (102ft 6in).

Other differences include:

  • Engines derated to 19,500lbs.
  • Forward cargo door and crew oxy bottle installation of the 737-500.
  • Locally increased gauge on wingtip skin panels to avoid flutter.
  • Wing-to-body faring modified to fit aft fuselage contour.


737-700

FF 9 Feb 1997

Approx 1050 in service plus 84 on order.

This was the first of the NG's to fly.

The first -700 was retrofitted with winglets on 11 Sept 2001 for Kenya Airways.

The 737-700C (Convertible) has a 3.4 x 2.1m side cargo door and can carry 18,780kg of cargo on eight pallets. The ceiling, sidewalls and overhead bins remain in the interior while the airplane is configured for cargo. There have been 21 737-700Cs ordered, mostly for the US Navy where they are known as C40As.

The 737-700ER is an all business class long range airliner, similar to the BBJ. It has a range of 5500nm an should enter service in early 2007.

Click for flightdeck photo and description


737-800

FF 31 Jul 1997

Approx 3262 in service plus 947 on order.

The 737-400X became the 737-800 but is significantly longer at 39.4m (129ft 6in) and seats up to 189. The project was launched on 5 September 1994, with commitments for over 40. First delivery was to Hapag Lloyd in April 1998. This is by far the most successful series of 737 and the huge backlog of orders will ensure the 737's production until at least 2012.

Differences from the -700 include:

  • Fuselage plugs of 3m (fwd) and (2.84m (aft).
  • Engine thrust increased to 26,400Lbs.
  • Additional overwing exits (similar to -400)
  • Tailskid added to section 48 (same as -400).
  • Environmental Control System riser ducts added (same as -400).
  • Re-gauged skins and stringers in wing and centre section.
  • 44.5in (1.13m) tyres, heavy-duty wheels and brakes.
  • Resized main landing gear structure.

The -800 has been available with winglets either as standard or retrofit since May 2001. These reduce aerodynamic drag thereby reducing fuel consumption by up to 7%.

MTOW of the HGW version is 78,960kg

A short field performance improvement package was developed in 2005/6 to allow GOL airlines to operate their 737-800's into the 1,323m (4,341ft) Santos Dumont airport. Since then it has also become an option on all 737-800's and standard on the 737-900ER.

 

737-800 ERX

This is a proposed heavier (83,500kg MTOW), longer range version of the -800 designed to meet the needs of the MMA.

Due for delivery in 2007, it will have various components from the -900X (see below) including its heavier gauge wing, nose & main gear and section 44 (wing-body join section). It will also have some parts from the BBJ1. Unique features to the -800ERX will include strengthening to the empennage.

 


737-900

FF 3 Aug 2000

55 built.

Boeing began work on the 737-900 in April 1997 which was stretched to compete with the 185/220 seat, Airbus A321. It featured a 2.4m (7ft 10in) fuselage extension giving it an overall length of 42.1m (138ft 3in), actually 40cm longer than the 707-120. The 900 has 9% more cabin floor space and 18% more cargo space than the -800; however Boeing opted to use the same NG emergency exit layout, with 4 main exit doors and 4 overwing exits, thereby still restricting the maximum passenger load to 189. Due to slow sales it has been succeeded by the 737-900ER.

 

737-900F

Boeing revealed the 737-900F study group in Sept 2003. The project was believed to be aimed at FedEx who are looking to replace their 727 fleet. It would use the side cargo door from the 700QC and be capable of taking 11 standard 2.24 x 3.18m pallets, 3 more than the -700QC and only 3 less than the 757. The -900 also has a hold volume of 51.7cu.m.

This project is now believed to be shelved.

 

737-900ER

FF 1 September 2006

Approx 260 in service, 261 on order

The -900ER (formerly known as the -900X) has the same length fuselage as the -900. Seating for up to 215 passengers has been achieved by adding a pair of Type II doors aft of the wing for passenger evacuation regulations and installing a new flattened aft pressure bulkhead which would add an extra fuselage frame (approx 1 row of seats) of cabin space. The flat bulkhead will become standard on all 737s from 2006 and the Type II door will be standard on all series 900s although operators may choose to have it deactivated.

Range is increased to 3,200nm with the addition of two 1,970ltr aux fuel tanks (or 2,800nm without aux tanks) and optional winglets. The 900ER will have reinforced landing gear legs, wing-box and keel beam structure to handle the increased MTOW of 85,139kg (187,700lbs). Take-off and landing speeds (and hence field length) are reduced by the short field performance improvement package originally developed for the 737-800, this is standard on all 737-900ERs. MZFW will be 67,721kg (149,500lbs) & MLW 71,400kg (157,500lbs), making it similar in weight to the 727-200; the brakes will be upgraded as a consequence.

Production started in 2006 followed by a two aircraft, 7 month, flight test program starting 1 Sep 2006. FAA certification was gained on 26 Apr 2007 with the first aircraft delivered to Lion Air the following day.


737-BBJ

BBJ1 FF 4 Sep 1998

95 BBJ1 & 13 BBJ2 ordered.

A corporate version of the 737-700 dubbed the Boeing Business Jet (BBJ) was launched on 2nd July 1996 as a joint venture between Boeing and General Electric. It combines the fuselage of a 737-700 with the strengthened wings and undercarriage of the 737-800. Up to 12 fuel tanks, giving 37,712kg of fuel can be fitted as a customer option. The BBJ pictured here (N737ER) was designed for medical evacuations and charter operations and flew a record 6,854 nautical miles (12,694 kilometres) from Seattle to Jeddah in 14 hrs 12 minutes. The aircraft still landed with 2,700kg of fuel remaining!

So far private individuals have bought 40% of the BBJs. Another 36% have been bought for government heads of state and the rest were sold to corporations and jet charter operators.

There is also a BBJC which is a BBJ with a side cargo door which is aimed at governments which may have multi-mission requirements.

Derivatives of the BBJ1 are in service with the US military as the C-40.

 

The BBJ2 (see photo left) has the 737-800 fuselage, wings and undercarriage. It has 25% more cabin space and twice the cargo space or aux fuel tank space of the BBJ1.

The BBJ3 is based on the 737-900ER and will be available from mid-2008. It has 1120 square feet of cabin space and a range of over 5400nm with 5 aux fuel tanks.

Externally BBJ's usually differ from standard production 7/8/900's by having various windows blanked to accommodate interior fittings and more antennas for comms equipment. All have winglets. The BBJ2 only has one overwing exit each side because it does not need any more with the few passengers that are carried.

Boeing is also looking at producing a convertible cargo version of the BBJ based on the 737-700C.

The 737 MAX is also being offered as a BBJ. The BBJ 2 MAX, based upon the MAX 8, will have a potential range of 6,200nm.


C-40

FF 14 Apr 2000

Orders: 8 C-40A, 4 C-40B, 3 C-40C.

The C-40 family are the US military versions of the 737. All have the -700 fuselage combined with the stronger -800 wing and landing gear, similar to a BBJ1.

C-40A: US Navy, Fleet logistics support aircraft.

Certified to operate in an all-passenger configuration (121 passengers), an all-cargo variant or a "combi" configuration that will accommodate up to three cargo pallets and 70 passengers on the main deck. For further C-40A details click here. This is the only C-40 version without winglets.

C-40B: US Air Force, High-priority personnel transport & communications aircraft.

Modified C-40A to include distinguished visitor compartment for combatant commanders and communications system operator workstation. The C-40B is designed to be an "office in the sky" for senior military and government leaders. Communications are paramount aboard the C-40B which provides broadband data/video transmit and receive capability as well as clear and secure voice and data communication. It gives combatant commanders the ability to conduct business anywhere around the world using on-board Internet and local area network connections, improved telephones, satellites, television monitors, and facsimile and copy machines. The C-40B also has a computer-based passenger data system.

C-40C: Air National Guard, High-priority personnel transport aircraft.

Modified C-40A to include convertible cargo area. May be converted for medevac, passenger transport or distinguished visitors such as members of the Cabinet and Congress. The C-40C is not equipped with the advanced communications capability of the C-40B. Unique to the C-40C is the capability to change its configuration to accommodate from 42 to 111 passengers.


E-737 AEW&C (AWACS)

FF 21 May 2004

14 Orders (Australia 6, Turkey 4, South Korea 4)

The 737 Airborne Early Warning and Control planes are designed for countries that can't afford or don't need the capability of the much bigger 767 or 707 AWACS. The base plane is essentially a Boeing Business Jet, which has the 737-700 fuselage with the stronger 737-800 wing to support its extra weight and the BBJ aux fuel tanks.

The AEW&C will use a phased-array, Multi-role Electronically Scanned Array (MESA) radar "Top Hat" sensor developed by Northrop Grumman and mounted in a rectangular faring over the rear fuselage. The antenna alone weighs 2950kg and is 10.7m long. However it provides a practical solution for fore and aft coverage while maintaining a low drag profile and allows the system to be installed on the mid-size 737 platform without significant impact on aircraft performance. A 737 airborne early warning plane costs from $150 million to $190 million, compared with about $400 million for the 767 AWACS. The AEW&C carries a mission crew of between 6 and 10 in the forward cabin.

Additional modifications include a new upper lobe section 46 to support the antenna; a new section 41 with a cut-out for an air-to-air refuelling receptacle, two ventral fins to counter balance the antenna and nose, wingtip and tail mounted counter measure systems. The aircraft will also have chaff and flare dispensers and approx 60 antenna and sensor apertures. The IDG's will be uprated to 180kVA. DOW is expected to be just over 50,000Kg.

The first green aircraft arrived at Wichita in December 2002 for structural modifications. Flight testing of the airframe ran from May 2004 until Jul 2005 with the aircraft logging more than 500 flight hours in 245 flights. According to Boeing “The plane performed superbly in terms of its avionics, structure, systems, flight handling characteristics and performance”. This was followed by flight testing of the mission system, including the MESA radar. All appeared to be going well for the project until 2006 when the first of the delays was announced because of “development and integration issues with certain hardware and software components”. Deliveries began to Australia in late 2009 and reached full operational capability in November 2012.

The aircraft will be known as the “Wedgetail” by the RAAF after the Australian Wedgetail Eagle, which according to the Aussies, “Has extremely acute vision, ranges widely in search of prey, protects its territory without compromise and stays aloft for long periods of time.” The Turkish AF will call theirs the “Peace Eagle”, presumably for similar reasons. Boeing are hoping to sell up to 30 AEW&Cs by 2016.

Photo: Brian Lockett Goleta Air & Space Museum


MMA / P-8A Poseidon

FF 25 April 2009. 116 Orders (US Navy 109, India 8, Australia 8)

Selected for US Navy contract for up to 109 aircraft

Jack Zerr, the Multi-mission Maritime Aircraft (MMA) programme manager described the aircraft as “A bit of JSTARS (Joint Surveillance Acquisition Radar System), a little bit of AWACS and a little bit of MC2A (Multirole Command and Control), but with the added ability to go and kill a submarine.”

The MMA, US Navy designation “P-8A Poseidon” and Indian Navy designation “P-8I”, is based on the 737-800 fuselage and the stronger 737-900 wing, with raked wingtips that have anti-icing along all leading edge slats. A weapons bay aft of the wing, (effectively in the aft hold) carries internal stores such as Mark 54 torpedoes. There are four underwing hardpoints for AGM-84D Harpoon or similar. The fuselage is strengthened for weapons employment and to permit ASW profiles. Up to seven mission consoles and a rotary sonobouy launcher can be fitted in the cabin. Like the AEW&C, the MMA will have 180kVA IDGs as standard. The MMA also has an in-flight refuelling receptacle over the flight deck.

Northrop-Grumman provide the electro-optical/infrared sensor, the directional infrared countermeasures system and the electronic support measures system. Raytheon provide an upgraded APS-137 maritime surveillance radar system and signals intelligence (SIGINT) solutions. Finally, Smiths Aerospace provide the flight management system and the stores management system. The flight management system provides an open architecture along with a growth path for upgrades. The stores management system permits the accommodation of current and future weaponry. The basic open architecture of the MMA is believed to have 1.9 million lines of code!

Much of the provisioning for the modifications is being done by Boeing during production to save time and cost at the conversion stage. Boeing has built a third production line which is dedicated to the MMA alongside the commercial 737 assembly. After the aircraft are assembled at Renton they are flown over to Boeing Field for mission system installation.

The current P-8As flying are known as “Increment 1” these have the basic tactical system. Increment 2 when it becomes operational in 2016 will have ASW improvements that provide a better performance at high altitude as well as AIS fitted.  Increment 3 with its further improvements is scheduled for 2021

Click here for more details about the development of the MMA.


SIGINT

Announced on 26 Jan 2006, the Signals Intelligence (SIGINT), or EP-8 if ordered by the US Navy, will be based on the MMA airframe. It will be used for airborne intelligence, surveillance and reconnaissance, and also advanced network centric communications.

The Boeing 737 SIGINT variant will have increased mission capability, operational readiness and combat radius relative to legacy aircraft. The design also has built-in growth capacity so payload capacity can easily be increased or upgraded to accommodate future customer requirements.

"A key advantage of this new program is that the 737 SIGINT aircraft will leverage the P-8A's advanced mission system architecture, mature design, and contractor logistics support and training systems approach. For customers that means reduced operating and maintenance costs over the entire life cycle of the system."


January 28, 2008

SigInt battle

U.S. Navy gears up for long-awaited EPX intel aircraft competition

By Paul Richfield

The U.S. Navy has asked U.S. defense contractors to design and ultimately build a new signals intelligence (SigInt) platform to replace the service's aging fleet of Lockheed Martin EP-3E Aries II turboprops. Although the number of aircraft in the potential "EPX" order is relatively small by U.S. procurement standards — 14 to 24 is a popular estimate — the final selection could have a significant influence on how first-tier militaries conduct maritime surveillance for decades to come.

Not only will EPX be the newest Navy aircraft devoted to eavesdropping on enemy communications, it also will be the first to serve as the SigInt element of a networked ISR system incorporating manned and unmanned aircraft, satellites, ground stations and surface combatants. Detailed technical requirements are closely held, although the Naval Air Systems Command (NAVAIR) revealed the basic considerations to prospective bidders at a recent EPX industry day conducted at Naval Air Station Patuxent River, Md.

Kristine Wilcox, a NAVAIR spokeswoman, said EPX will be a manned ISR and targeting aircraft capable of operating in a SatCom-constrained environment, in concert with the P-8A Poseidon maritime patrol aircraft and the UAV ultimately selected for the Navy's Broad Area Maritime Surveillance (BAMS) bid. Wilcox said the competition is open to all interested parties and is expected to attract a diverse range of platform and sensor providers.

"Nothing is decided," she said. "We plan to work with industry to find the best solution."

This could be considered a minor revelation, as it opens the door to alternatives to what many had considered a fait accompli — a dedicated SigInt version of the twin-turbofan P-8A. Boeing unveiled this 737-based aircraft in January 2006, after the Navy dropped out of the Army-led Aerial Common Sensor (ACS) program. ACS was slated to replace the EP-3E and two types of Army reconnaissance aircraft, but the contract was canceled when ever-expanding mission requirements outgrew the winning platform, the Embraer 145 regional jet.

Given this background, Embraer seems an unlikely EPX bidder. But if the Brazilian manufacturer does attempt to scale the Pentagon's wall again, it now can offer the EMB-170/190 family — single-aisle airliners that appear able to carry any reasonable evolution of the EP-3E mission system. Embraer declined to comment on EPX, although senior executives previously conceded a post-ACS wariness of the U.S. acquisition process and specific issues with U.S. defense contractors serving as lead systems integrators.

Another airline narrowbody with potential EPX application is the EADS Airbus A320 family, and EADS representatives attended the Pax River briefing. NATO selected and then dropped a stretched derivative aircraft, the A321, as its platform for the Alliance Ground Surveillance program now in concept development.

General Dynamics' Gulfstream unit seems an obvious EPX contender, and its BAMS partnership with Boeing — built around an optionally-manned version of the G550 business jet — effectively positions both companies for EPX should the Navy call for a platform smaller than a 737. Gulfstream also could proceed without Boeing, but this seems unlikely unless BAMS is awarded to one of the other contenders.

Northrop Grumman is offering an AESA-equipped Block 20 Global Hawk UAV for BAMS, while Lockheed Martin has proposed a long-winged variant of the General Atomics Predator B UAV. The initial contract award was planned for October, but the decision was still pending as C4ISR Journal went to press.

Bombardier's Global Express — the chosen bus for the U.K.'s ASTOR battlefield radar program — is another potential EPX platform, but like Gulfstream, its fate is tied to the size and scope of the mission system. If the Navy keeps the size, weight and power demands within tight limits, observers believe, one of these converted corporate chariots could get the nod.

"Don't count the bizjets out," said Joe Siniscalchi, L-3 Communications Integrated Systems' director of business development. "Processing density has improved, allowing us to drive to smaller systems. With EPX, the biggest challenge is that you have the right size, weight and power to do what you need done. It's really a question of new development vs. reuse, and how much risk the customer is willing to take.

"EPX is very important to us. We're incumbent on the current platform and have been tracking developments for some time. We're very interested in seeing how the Navy program evolves. Clearly, the P-8A and BAMS programs will have an influence, but that being said, the Navy is in assessment mode. Certainly, the mission system will drive the requirements, and [P-8A] is built for an entirely different mission — anti-submarine warfare. With EPX, the big thing is how much onboard processing power will be needed to meet the required level of autonomy.

"On-scene, on-orbit, on-platform processing, tactical dissemination, linking back with the command authority — these are the kinds of things that will shape the EPX requirements. The Navy needs to be able to do what the EP-3E does, but it also has to plan for tomorrow's threats. Do you need 24 people, or will a data link suffice? This is the kind of question that has to be answered. More and more, software is driving capabilities, so it's much easier to build a smaller system that meets the mission but is easily upgraded as the requirements mature."

CONNECTING AN ISR TRIAD

Although the ability to process SigInt data in real time may have a strong influence on the final EPX systems configuration, forging robust electronic links with P-8A and BAMS could have equal weight in the hardware/software procurement arena. Although BAMS remains a wild card until contract award, Boeing hopes the apparent commonality between the P-8A and an "EP" version of the same aircraft will give it the edge, regardless of who wins the UAV contract.

"Our whole approach is to capitalize on the Navy's P-8A investment, as opposed to building from the ground up or refurbishing something to last for another 50 years," said Tim Norgart, business development director of Boeing's ASW/ISR unit, based in Puget Sound, Wash.

"When we first rolled out the [P-8A], there were two variants: Search & Attack and Surveillance & Intelligence. SI went away when the Navy went with the Army on ACS, but we felt confident that someone would eventually come back to an airplane of this size, for this mission. And now, with the Navy out of ACS and EPX a stand-alone program, they have. It's funny how things come full circle.

"Transitioning from the P-8A, we see very few changes to the airplane and can easily incorporate all the features needed for the SigInt mission. We do intend to leave the hard points on the wings intact, and the bottom forward section has all that strengthening for weapons, antennas and anything else the Navy wants to install. We'll also have a small ‘canoe' up there, but the structural work has already been done," Norgart said.

"P-8A has an open mission system architecture, and it's only a matter of plugging in the applications needed for the specific mission; you can ride the SigInt applications right on top of this backbone, without them cascading through the entire system. Of course, we'll also leverage the sensors that are already on the P-8A, like radar and [electro-optical/infrared], and the baseline [communications] links.

"The sharing and the workload capacity is there, and our ability to lay down a 14-operator configuration is very easy; you just bolt the work stations to the seat rails and hook up the power and cooling. With the P-8A, the wiring is already there for the power distribution, along with a significant reserve. We don't even make a dent in that figure.

"Our core development team worked together on the MRA4 Nimrod mission system, and we're going to leverage those work stations so the radar, ESM and all those kinds of things remain the same. We plan to stay with the Raytheon team that does the current system on the EP-3E; they're a big part of what we're doing and bring a tremendous amount of experience to this mission area.

"What we will be bringing on are a group of different SigInt providers, talking with all of them, to put a total system together. We're in our assessment phase now. If the Navy moves toward a [lead systems integrator] and wants to compete different parts of it, we'll do that.

"Onboard processing is still a great area for debate and could determine the size of the airplane required, but there are a whole lot of other things, as folks with the first ACS program will tell you. Our approach is really platform-agnostic. We didn't settle on the 737 by accident, or because of the P-8A.

"We take the total requirements picture and apply them to a wide range of air vehicles, and might end up with two vehicles to support the total set of requirements. We've known the requirements for EP-3E and EPX baseline, and they continue to drive our trade study to a 737-based approach.

"Programs that start out on the margins of payload and power capacity — the risk assigned is pretty high, and not many of them have been successful. When the margins are tight, if you want to put something on, you have to take something off," Norgart said.

MOVEMENT TOWARD MULTI-INT

Mission systems providers are conducting their own EPX trade studies on two parallel tracks. One assumes that the Navy will seek only to replicate EP-3E with a more modern platform, with machines replacing humans in some on-board roles. The second — and some say more likely — approach is that the service will regard the Aries II as merely a launching point, with EPX emerging as the first true multi-Int aircraft, and one with networking capability, as well.

"They definitely want to combine additional capabilities related to things on other aircraft; the key is to analyze the time line of the program," said Jim Courtright, director of maritime surveillance programs for Lockheed Martin.

"If you're looking 10 years forward, the technology will be packaged and integrated somewhat differently. The [EP-3E] systems are very federated for compartmentalization, and as a function of their design increments and block upgrade development.

"It's pretty clear that the Navy is going to need an open architecture for upgrades and new capabilities, with a system that fits with the overall system-of-systems architecture in 2015 or 2020. Also, they're going to want to take advantage of all the improvements in antennas, signal processing and other functions."

Raytheon, a major P-8A partner, sees EPX as a "positioning exercise." Jim Hvizd, the company's director of enterprise pursuits, said involvement could range from an upgraded search radar if the Navy goes plain vanilla, to a multilevel sensor suite incorporating SigInt, synthetic aperture radar, ground moving target indication, onboard processing, and UAV control/data collection, with or without help from ground stations.

"It's going to be interesting to see how the requirements flesh out, and we've heard everything from a business jet to a 737," Hvizd said. "The Navy still has to work out how EPX, P-8A and BAMS will work together. We're supporting Boeing on its BAMS bid, and our APS-137 [radar] could appear on the G550 BAMS; our radar for EPX would certainly draw from that legacy. Until the BAMS decision is made, I feel we're pretty constrained.

"Multi-Int on a single platform is a new thing, as is sharing data from multiple platforms, and we look at it as a way to serve the Navy's needs across all the maritime surveillance programs. What we've learned with [the United Kingdom's] ASTOR is how to deliver ISR capabilities unique to specific requirements, but from ASTOR to EPX will be a great leap forward. It comes down to a choice between another patrol plane or a flying battle station that can drastically shrink the sensor-to-shooter loop: That's what the Navy has to decide."

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