Poseidon & EP-X

Features

The P-8A features some 30 per cent more cabin space than the P-3, and has been designed from the start to not only perform the traditional anti-submarine (ASW) and anti-surface warfare (ASuW) missions, but also for the intelligence, surveillance and reconnaissance mission in maritime, littoral and even overland environments. The airframe is based on that of the 737-800 airliner but has been substantially modified, and is mated with the larger wings from the 737-900. It is powered by two commercially derived CFM56-7E engines each rated at 27,300lbs of thrust, and each fitted with 180kVa generators the same as those on the Wedgetail AEW&C aircraft to power the myriad of electrical systems on board and to cater for future growth. The CFM56 is also in use on navy E-6C (707) communications aircraft, and the P-8’s engines are identical to those used on commercial aircraft and have not been re-designed or treated for low level overwater operations, although specific wash procedures have been specified in operational use.

The US Navy’s requirement calls for a four hour low level mission to be conducted 1200nm (2220km) from base in a typical hi-lo-hi profile, although this can be extended through the use of air-to-air refuelling via an air force type UARRSI (Universal Aerial Refuelling Receptacle Slipway Installation) receptacle located above the cockpit.

The P-8A will have a maximum take off weight of 189,000lbs (85,700kg), a cruise speed of Mach .78, and a service ceiling of 41,000 feet, substantially faster and higher than the current P-3. Few of the P-3’s systems have been carried over to the P-8, although the P-8’s acoustic suite will be based upon that of the P-3C, albeit without the P-3’s tail-mounted Magnetic Anomaly Detector (MAD) ‘stinger’, and the Raytheon APY-10 radar is a distant development of the APS-148 radar used on later P-3Cs.

Boeing says it has changed 75 per cent of the 737-800’s primary structure for the P-8A, mainly in the use of stronger gauge materials for the expected flight profiles of the military aircraft. Other keys changes include the installation of the UARRSI in the forward upper fuselage, dozens of antennae for the various communications and sensor suites, and of course, the addition of an internal weapons bay and above that, an integral fuel tank in the aft third of the fuselage which is where most of the changes have been made.

Apart from the internal weapons bay which has five hard points each rated to 1450lbs (650kg), the P-8A also has two hardpoints on each wing outboard of the engines, each rated for 3000lbs (1361kg), and two hardpoints in tandem on the centre-forward fuselage, each also rated for 1450lbs (650kg).

The new integral fuel tank is in addition to six auxiliary fuel tanks carried in the belly of the aircraft, three forward and three aft of the wing box. The six aux tanks are standard fit on the US Navy P-8A and any ‘delete options’ of any of these tanks by buyers with lower range requirements will need to be certified.

Other key external features include the Wescam MX-20 electro optical/infra red (EO/IR) turret which is stowed in a ‘box inside the lower forward fuselage; an ESM dome antenna on the lower fuselage just behind the wing, two CDL antennas in ventral domes aft of the weapons bay, an INMARSAT antenna on the top of the fin, and a DIRCM turret similar to that used on the Wedgetail just below the APU exhaust in the rear fuselage. The raked wingtips are developed from those used on the 767-400, increase fuel efficiency in the cruise by about three per cent, and are less prone to icing that the more familiar near-vertical winglets used on most commercial 737NGs.

Inside, from front to back the P-8A features the Raytheon APY-10 radar in the nose, a commercially derived 737 flight deck with additional military radios and display screens, a crew rest area behind the cockpit, banks of power distribution racks, two observer stations, rear facing seating on the starboard side for take off, landing and ditching, five workstations on the port side, storage lockers and communications racks, a mission planning desk with four chairs, additional equipment racks, sonar buoy storage racks and launchers, and for long missions, the all important lavatory and galley at the rear.

Each of the five cabin mission consoles have two high definition display and have been designed with modern human/machine interface ergonomics in mind. Like the RAAF’s AP-3C Orions, any mission can be done from any station using specific logins. The hardware is similar to that designed for use in the Wedgetail AEW&C aircraft but is specific to P-8, and the aircraft’s systems have been designed around an open architecture backbone for later enhancements or the easier development of different variants.

Manufacture

Boeing had originally considered shipping standard 737-800 fuselages from the fuselage manufacturer, Spirit, in Wichita, Kansas, and then performing the necessary modifications on its Renton assembly line. But early in the process it decided to build the unique P-8 fuselages in whole alongside those of commercial 737NGs at Spirit, and then conduct final assembly only at Renton. “It didn’t make sense to cut up the standard fuselage after assembly,” Boeing’s Deputy P-8 Program Manager, Chuck Dabundo told AA at a briefing in Seattle.

The P-8’s wings and empennage are built from scratch at Renton alongside the equivalent commercial structures, and are added during final assembly.

The assembly model being used for the initial test aircraft is essentially the same as that which will be used during production. Boeing says it is doing that so it can ‘lean’ out the process as much as possible on the test and development aircraft in order to find efficiencies on the line before the first production aircraft start coming down.

At the end of a P-8’s first flight, the aircraft lands at nearby Boeing Field where the final systems fit out and checks will be carried out, and the flight test program conducted.

Boeing points out there are clear benefits of building the P-8 alongside commercial 737s at Renton. The whole Renton facility and its workforce has now been made ITAR compliant so it confirms to US military security regulations, which means the facility and the workforce don’t need to be compartmentalised. This allows the company to switch workers between lines as required, and also to make better use of factory and post production spaces. Being currently builds 31 commercial 737s per month and has a backlog of nearly 2000 aircraft. During low rate production of the P-8 only one aircraft is expected to be built per month, rising to 1.5 aircraft in a multi-year buy.

Boeing says it is also using the P-8 production line as a model it hopes to be able to apply to future commercially derived military platforms such as its proposed USAF 767/777 tanker line, or other 737 derivatives in future.

The other benefit of basing the P-8 on a commercial product is that any improvements offered by Boeing for 737s on order or in service can also be leveraged to the P-8. For example, CFM’s recently announced efforts to improve the fuel burn of its engines by one per cent via hardware and software changes.

US Navy Requirement

The US Navy now has a ‘program of record’, if not full funding, for 117 P-8As to replace its dwindling P-3C fleet. To date, three aircraft have been built while a fourth is currently in final assembly.

The six flight test aircraft will be dubbed T1 to T6, while the two static test and fatigue test airframes will be S1 and S2 respectively. To date, T1 and T2 have both flown, while S1 is already in the static rig at Renton and has commenced its load testing. T1 will be the primary airworthiness test aircraft checking flying qualities, performance testing, in-flight loads and air-to-air refuelling, and as such will not carry a full mission suite and will be heavily instrumented. T1 first flew in April, and is expected to commence its flight test campaign later this year once sufficient data has been gleaned from S1’s static rig.

After flying just once on June 5 including a low pass at nearby Whidbey Island Naval Air Station, T2 is currently being fitted with a full mission suite. T2 will be used to test the aircraft’s mission suite and sensors and will fly again in early 2010. T3 is currently in final assembly at Renton and will be the primary mission system and weapons clearance and certification test aircraft, and is due to commence its flight test program around April 2010.

S2 will commence assembly shortly and will enter its fatigue test rig early next year. S2 will complete two lifetime fatigue cycles, that is double the expected 25 year or 25,000 hours life cycle of the P-8. An interesting point to note here is, whilst commercial 737s often operate for 75,000 hours or longer, military aircraft fly a lot less than their commercial cousins, and also operate in different and often harsher environments. This is expected to be particularly true for the P-8 which is expected to spend a lot of its time at low to mid altitudes over water and in the weather, whereas as commercial aircraft deliberately avoid weather and operate at much higher and smoother altitudes.

Following on from S2 will be T4, T5 and T6, all of which will be production representative aircraft and will be used for initial fleet training and to conduct the P-8’s Operational Evaluation (OPEVAL) prior to Initial Operational Capability (IOC) in 2013.

The P-8 is currently planned to be developed in three versions. Formerly called Spiral Zero or Baseline, the Increment 1 version will be the first to enter service in 2013 with the USN, and will form the basis for the follow-on Increment 2 and Increment 3 versions. Increment 2 is being co-developed between the US Navy and the RAAF, and is expected to reach IOC in 2015, while Increment 3 will follow in 2018.

The initial weapons suite being developed for Increment 1 aircraft includes the SLAM-ER air-to-surface missile, the Mk-54 torpedo, and bombs and mines. Increment 2 weapons and system improvements are currently under study now, but no firm requirements have yet been release, while Increment 3 is a notional upgrade at this point. Boeing says whether earlier aircraft are subsequently upgraded to later Increment versions is yet to be decided, and may depend upon how much hardware will need to be changed out. Regardless, the company says the digital open architecture being built into the P-8 from day one should make it easier to perform hardware, software and weapons enhancements than on previous aircraft with comparatively ‘closed’ systems.

In US Navy service, the P-8 will operate in conjunction with a fleet of globally-based BAMS Global Hawk UAVs, hence the requirement for only 117 P-8s versus the more than 200 P-3s the Navy once operated. Similarly, the RAAF plans to replace its 18 AP-3C Orions with about eight P-8s and a similar number of Global Hawks to cover Australia’s extensive sea-air approaches and overseas commitments.

Whilst Boeing officials wouldn’t be drawn on comparative availability numbers, they did suggest that the P-3 doesn’t necessarily compare favourably with the P-8 on a one-on-one basis. They point out that the P-8 is based on a commercial airframe with a better than 99 per cent dispatch rate, and that its newer and more easily upgradeable systems should provide better availability than those in the 25-45 year old P-3s in service around the world. Additionally, the jet-powered P-8’s higher cruise altitude and faster transit speeds will allow it to get to a search area faster than the turboprop P-3, thus making it more efficient in the prosecution of a mission, although the P-8 can only come close to the P-3’s 12+ hour endurance with the assistance of air-to-air refuelling. Additionally, a suite of high end synthetic devices being developed in parallel with the aircraft should ensure that many training missions including fatigue-eating ‘touch and goes’ are a thing of the past on the P-8.

Boeing hopes to sell the P-8 to up to 18 nations, all of whom it says either operate P-3s now or have a high end maritime surveillance capability requirement, and says recent efforts by Lockheed Martin to market a new wing kit to existing P-3 operators (including Australia) doesn’t appear to have dented interest in the P-8.

Australia and the P-8

In January India became the first international customer for the P-8 when it ordered eight P-8Is, an ‘export’ version of the Increment 1 P-8A.

Australia has long stated a desire for a manned replacement for part of its AP-3C fleet, and in July 2007 then Defence Minister Dr Brendan Nelson said the P-8 was the preferred choice for the manned mission, and earlier this year the RAAF entered into a MoU with the US Navy to jointly define and develop the Increment 2 aircraft with a view to first delivery to the RAAF in 2016/17.

Whilst not fully committing the RAAF to the P-8, this MoU will not only give Australia a ‘buy in’ to the configuration of the Increment 2 P-8, but will also help reduce risk on any future RAAF program by giving it earlier insight into the aircraft’s development and the planned US Navy support model. Commonality with the USN Increment 2 model would also allow the RAAF to buy in to the US Navy’s scheduled upgrade program, ensuring better interoperability and greater levels of support as the platform matures.

The P-8 requirement was reinforced in May’s Defence White Paper, and a little more detail was released in July’s Defence Capability Plan (DCP). Despite industry efforts and the modern systems currently installed in the aircraft, the RAAF appears to have all but closed its mind to the possibility of re-winging its AP-3Cs. Apart from the new wing sets, the Orions would also require additional sensor and system upgrades post-2018, while corrosion and fatigue issues elsewhere in the airframe would need to be addressed.

The RAAF’s decision to defer any decision on acquiring a UAV component for the Orion replacement essentially pushed the manned aircraft to the fore. Current plans are for a decision on the manned aircraft to be made in the 2013/14 to 2015/16 timeframe, and IOC being achieved between 2017 and 2019. The UAV component would then follow a couple of years later.