FARNBOROUGH 2008: Boeing 737 embarks on its Poseidon adventure

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The first  Multimission Maritime Aircraft (MMA) is nearing completion, having achieved ‘power on’ on June 9. A ‘programme of record’ covering the building of 108 aircraft for the US Navy is now in place.

Though the prototype has yet to fly, Poseidon has a strong presence at Farnborough. Many see a link between Boeing’s high profile marketing effort for this advanced sub-hunter and the troubles presently afflicted BAE’s Nimrod MRA.Mk 4 programme for the RAF. Boeing is certainly stepping up its efforts to sell more of these state of the art sub-hunters to other air arms, and the company will be briefing potential customers about the programme at the show – perhaps including the RAF.

The MMA requirement emerged in 1990, after the previously planned US Navy P-3 Orion replacement (Lockheed’s Orion-derived P-7) was abandoned. Boeing proposed a version of the 737-800ERX to meet the renewed requirement to replace the Navy’s 196 P-3s. Boeing converted a Model 737 BBJ2 to serve as a technology demonstrator for the P-8, integrating a pair of functional mission system consoles on the aircraft. This demonstrator made a tour of five US Naval Air Stations in December 2003.

The BBJ/737-based design, which combined the fuselage of the 737-800 with the wings of the 737-900, was selected in June 2004, and the US Navy placed an order for five test airframes.

The new aircraft incorporates eleven weapons stations, for carrying torpedoes or air-to-surface missiles. These include five hardpoints in the belly weapons bay, just aft of the wing, (each capable of carrying 1,450lb) and two similarly stressed under-fuselage hardpoints further forward. The aircraft also had four - originally six - under-wing pylons, each capable of carrying up to 3,000lb. The aircraft also has three rotating ten-shot launchers for the 126 sonobuoys it carries.

The aircraft was designated as the P-8A in March 2005, and soon after lost its characteristic up-turned 737 winglets soon afterwards, replacing these with plain backswept wingtips manufactured by Stork Aerospace of the Netherlands.

The P-8A passed its Preliminary Design Review (PDR) in November 2005, and passed its Critical Design Review (CDR) in July 2007, opening the way for Boeing to begin production of the first of five test aircraft for System Design and Development (SDD) in December 2007.

 boeing p-8a poseidon

The first aircraft (T-1) is due to make its maiden flight in March 2009 before making the short journey to Boeing Field for the installation of mission systems. This will be virtually ‘plug-and-play’. The aircraft will then fly again in September 2009, before moving to the US Navy's flight-test centre at Patuxent River in Maryland in October.
Packed with flight test instrumentation, T-1 will be used for airworthiness testing and envelope expansion, and later for weapons carriage and release trials. T-2 is expected to fly in January 2010 and will be used for mission system testing, before going to Eglin AFB, Florida, for climatic chamber testing. T-3 will be deployed to Patuxent River for electromagnetic compatibility testing, for performance testing, and as a back-up mission system testbed.

The three test aircraft will undertake a 2,300h, 700-sortie flight test programme, backed up by dedicated static and fatigue test articles (S-1 and S-2). Though the P-8A is based on the 737-800, it will operate in a very different environment, to very different flight profiles (at lower altitude and pulling higher g), making new full-scale static tests and fatigue testing to the equivalent of two 15,000 flying hour lifetimes absolutely essential.

Four additional development aircraft are likely to be ordered following the US Navy design readiness review this August, for use in the initial operational test and evaluation scheduled to commence in April 2012, with a planned Initial Operational Capability (IOC) date set for 2013.

Full-rate production will begin in 2012. The annual production rate was originally planned to be 16 aircraft, but this was reduced to 13 for budgetary reasons. With P-3 availability a concern, though, the US Navy is understood to have asked Boeing to look at higher rates, and the manufacturer believes that it could build 18-24 aircraft per year.

Previously, Boeing has produced military versions of its civil airliner designs (like the 737-based Wedgetail AEW&C aircraft and the KC-767 tanker) by building ‘green’ aircraft on the normal commercial line, before then flying them to a modification centre to be stripped and rebuilt. The P-8A, however, will be a fully provisioned military aircraft built on a third, ITAR-compliant 737 assembly line at Boeing’s Renton plant in Washington.

This will give the Navy extraordinary affordability, according to P-8 programme manager Bob Feldman. “When the P-8 is in full production we will build them, just like every other 737, on a moving production line.” This line could be used to build commercial 737s if Boeing needed more airliner production capacity.

The P-8A is far from just another 737, however, with extensive structural changes to allow it to fly demanding ASW mission profiles, and with a weapons bay in the lower aft fuselage and with new weapons stations under the belly and below each wing. The P-8A has about 40% parts changed from the airliner 737. Designated as a 737-800A, the P-8A has a fuselage based on that of the 737-800, married to a 737-900 wing, with raked wingtips.

The Poseidon is fitted with a Raytheon APY-10 radar and a comprehensive ASW mission systems suite, including ESM, and Link 11 and Link 16 datalinks, though the planned Magnetic Anomaly Detector has been removed to save weight. The P-8A will be integrated with Mk. 54 torpedoes and SLAM-ER cruise missiles initially, but there will be provision for a range of future weapons.

To remove the need for the P-8A to waste fuel and airframe life by dropping to low altitude to identify surface targets, the US Navy is believed to be looking at the use of UAVs to augment the Poseidon. These are believed to include the Lite Machines Voyeur – a 24in long coaxial rotor expendable UAV that has been designed to be launched from a standard sonobuoy tube.