Maritime Air: Exploiting 21st Century Technology - The US Navy Multi-Mission Maritime Aircraft
15 Nov 2004
In early June 2004 the US Navy (USN) made a watershed decision when it awarded a $3.9Bn contract to Boeing for the development of a 737 Next Generation (NG) aircraft as its 21st Century platform to meet the Multi-mission Maritime Aircraft (MMA) requirement, with the primary emphasis on the anti-submarine warfare (ASW) mission.
For over 30 years, Lockheed Martin has essentially owned the ASW fixed-wing aircraft market. They achieved this market dominance by selling over 80 per cent of the fixed-wing Maritime Patrol Aircraft made up of 755 land-based P-3 Orions and 187 carrier-borne USN S-3 Vikings probably worth around $60Bn to Lockheed. The P-3 Orion has provided outstanding maritime patrol aircraft (MPA) capability, evolving to meet changing operational requirements through introduction into service of the P-3A, B, and C models and with avionics updates such as Update III. The Update IV was cancelled in the early 1990s as the cost of development could no longer be justified with the receding Soviet threat. In addition to the USN P-3s, another 113 were built for 12 countries by Lockheed with another 100 by Kawasaki Heavy Industries (KHI) under licence for
From a weapon perspective, the first Iraq war, Bosnia and Kosovo, and Afghanistan helped drive the evolution of the P-3C from an ASW and anti-surface warfare (AsuW) platform into a full-up, ‘flying battle cruiser’. The USN integrated the latest air-to-ground weapons and deployed the P-3C as its reconnaissance and strike platform using its long endurance to orbit the battlefield ready to react quickly when threats were detected. Figure 1 illustrates how the P-3 ‘battle cruiser’ capability evolved and how the USN’s MPA capability will naturally continue the evolution with the 21st Century USN/Boeing 737NG MMA.
MMA will fill a capability gap worldwide and, as Lockheed did with the P-3, should reap Boeing a similar international and domestic sales dividend. Up to 150 MMAs could eventually be sold to the USN and 100–150 more sold to the international market where only the Nimrod MRA4 will have anything like comparable capability. The technical and cost overrun woes of BAE Systems in modifying cannibalised Nimrod MRA2 airframes is well publicised and the UK MoD’s decision to cut back further the Nimrod MRA4 force from 18 to 12 (having originally contracted for 22) in the latest round of defence cuts takes Nimrod out of the sales marketplace.
MMA Requirements and Contractor Responses
Figure 2 summarises the US Navy’s MMA requirements. Undersea Warfare (USW), with ASW as the linchpin, was the key specified MMA mission – one which could not be performed by any other platform including unmanned aerial vehicles (UAVs). However, the core ASW and ASUW sensors and weapons will provide Intelligence, Surveillance and Reconnaissance (ISR) and secondary mission capability, with full network centric warfare connectivity and information creativity, which will provide a huge payoff to the warfighter.
The watershed MMA decision was really a twofold one. The first was the USN decision to change from what has been a purely military customer product (albeit with its roots in the 1950s Electra commercial airliner) to a commercial-derivative aircraft. The second was the decision to switch from turbo-propeller engine power, which has traditionally powered MPAs worldwide, to turbofan jet engine power.
The fiercely contested competition was extremely well orchestrated by the USN, who first funded initial feasibility studies to evaluate whether they should go for a new aircraft or continue their ‘SLEP-ping’ (Service Life Extension program) of the P-3C. These studies and exhaustive structural inspections of operational P-3s convinced the USN that buying a new aircraft for MMA was essential and that they should look at commercial aircraft to reap the benefits of logistics commonality. The USN then awarded two risk-reduction phase contracts to Boeing and Lockheed totalling $31M each over 36 months to examine in depth the relative merits of the two contenders’ very different offerings and approaches. These risk reduction initiatives analysed these two fundamental issues exhaustively with vocal supporters and detractors for both concepts.
Lockheed sought to reaffirm the ‘you know what you know with the aircraft that always gets you home’ mantra by staying with a traditional MPA approach also epitomised by the turboprop-driven Atlantic I and II, CN235/295 family, and ATR 42. Orion 21 would have had four 21st Century new turbo-prop engines with eight-bladed composite propellers installed in a digitally designed and built airframe.
Boeing sought to show that the advantages of having a base of 5000 commercial 737 model twin-jet aircraft, and of having experience of converting over 2000 commercial aircraft into military platforms (accounting for about 94% of the world conversion market), far outweighed the merits of ‘warmed over 20th century turboprop technology’.
Until the MMA decision, only the Nimrod (first in service in 1968) and the Viking (1970) were powered by turbofan jets (
The Nimrod was derived from the Comet aircraft, which was a rather more successful airliner than the Electra. The Nimrod MR1 & 2 saw extensive service in the Falklands war and its MRA4 variant was the winner of the
Commercial Derivative or Military New Build?
The Boeing 777 was the first commercial aircraft to be designed in the digital 3D environment and then produced on a digital production line with a total absence of holding fixtures, jigs and towers; and making extensive use of lasers to ensure every hole was drilled in the identical place and, hence, any wing would fit any fuselage. The 737NG illustrated in Figure 3 was the second commercial aircraft to be digitally designed and built so that every 737NG MMA will roll off a state-of-the-art production line which has turned out as many as 24 aircraft a month with an almost total absence of ‘shims’. Shims are wedges inserted in aircraft structure to make mismatched aircraft structure to fit together during assembly. A P-3 typically needed 80lbs of shims. A 737NG uses less than 1lb of shims – providing a huge indication of the benefit of digital design and production. The application of shims is a maintainer’s nightmare as the resulting gaps around the shims are natural havens for salt water and, hence, corrosion. Criticism was levelled at the 737 saying it was not designed for over-water, low-altitude MPA operations. However, unlike the P-3 which is washed down with fresh water after every flight, Aloha airlines washes down its 737NG on an opportunity basis as it makes hundreds of flights a year below 5000 feet over water flying between Maui, Kauai, Oahu and the Big Island. A major focus of the 737 redesign for the NG was stringent corrosion measures which: redesigned parts which had suffered from corrosion in the 737 Classic; optimized use of corrosion-resistant materials; or introduced specific anti-corrosion features. The commercial customer was the driver for all of these, but it will be the USN and their military allies which will reap the military benefit in their 737 MMAs.
The commercial market of the 21st century is extremely demanding. Low-cost, ‘no frills’ carriers like EasyJet, South West and Ryan Air all baselined their fleet’s operation on a single model – the Boeing 737. South West was the very demanding launch customer for the 737NG. The ‘no frills’ airlines live or die by some simple metrics – total aircraft reliability to ensure on-time departure and arrival and simple and easy maintenance to maximise fleet availability and minimise downtime. The military customer will struggle to comprehend the huge benefit that the commercial market drivers will bring to their MMAs. For example, on average, and based on more than a 100 million flight hours, the dispatch reliability of a 737NG is over 99 per cent, far greater than any military MPA.
The Air Vehicle
A 737NG is usually ordered out of a rather thick catalogue. It comes in four ‘length flavours’: 737-600, -700, -800, and -900 (Figure 4). A 737-700 is a -600 with two 3m (10ft) plugs, one in front of, and one behind, the wings. A -800 is the same to -700 and so on such that the longest, the -900, is 18m (60ft) longer than the shortest, the -600. The wings have the same aerofoil design planform, but are successively strengthened internally to take the additional weight. The customer can choose whether he wishes to buy the elegant 8ft winglet option, which increases range 4–6 per cent, and selects from one of six engine thrust options up to 27klb thrust.
Boeing had decided that the USN MMA Operational Requirement could be met with a 737 Increased Gross Weight (IGW) defined as a 737-700 with -800 wing plus winglets, max thrust CFM56-7B27 engines, and 90KVA generators (there is another 90 KVA Auxiliary Power Unit in the tail).
The USN later decided that they needed more space and power, so Boeing got their 737 aircraft catalogue back out again. This time, they immediately responded by offering a 737-800IGW, namely a 737-800 with -900 wing. Boeing met the increased power requirement by adding 180kVA (vice 90kVA) generators, which had already been developed by CFMI for the 737 Wedgetail AEW & C programme. By contrast, the military aircraft designer – in this case Lockheed – was faced with enormous problems. Radically changing the weight or volume of their Orion 21 design was clearly going to be high risk compared to a 737NG changing its weight or volume with its base of millions of flight hours, hours of wind tunnel test data, and exhaustive structural analysis.
As a result of inputting the faster/more reliable dispatch performance data into a 737NG MMA model, the operational analysis told a telling story. Studies showed that 32 737NG MMAs could provide total worldwide, ‘round the clock’ ASW coverage without repositioning. In contrast, 40 P-3s were needed, with assets repositioned to every base, except Roosevelt Roads, to achieve the same coverage and, hence, cost far more in fuel alone, let alone wear and tear on the aircrew.
The commercial market drives not only the aircraft technology, but also key technologies such as avionics. The military customer is too often faced with having to scratch around to find funds for avionics upgrades (such as mission computer with more memory) downstream long after the big-ticket item money for the programme has come and gone. The 737NG cockpit is state-of-the-art, the only change for MMA being the addition of a tactical display. On-going, commercially-funded R&D will provide the USN with the option to select from several on-going commercial cockpit initiatives. A single commercial Head Up Display (HUD) is already going to be an MMA standard, but the Vertical Situation Display, GPS Aided Landing, Enhanced Vision System, Navigation Performance Scales, Electronic Flight Bag, Synthetic Vision System, and Surface Guidance System offer the USN options from a glittering funded R&D programme to pick and choose from based on military benefit.
Boeing did have to address one significant production issue. The Boeing narrow-body production line in
(Turbofan) Jet versus (Turbo) Prop
In the early 1960s, the turbo-prop engined aircraft with a stiff wing presented the best compromise of capabilities for the MPA mission. It could be flown long distances at medium altitudes and was more efficient at low altitude compared to an aircraft powered by a turbo-jet engine, which had poor efficiency at low altitudes. In return for obtaining this mission efficiency, it was recognised that the use of turboprop power (and the associated straight-wing airframe) brought some attendant disadvantages. These were slower speed of transit (which extended the time taken to complete the
In engine sales, the commercial customer for engines clearly drives the marketplace and, hence, the R&D and production. Over the last 40 years, the ratio of turbo prop to turbo jet engine production worldwide has gone from 40:60 to 5:95. MMA is clearly a beneficiary with the CFM 56-7 engine. From a performance point of view, the CFM 56-7 is hard to beat. The GE-Snecma CFM International (CFMI) partnership has been a highly successful US-French partnership. The 56 series powers many commercial Boeing and Airbus aircraft. CFMI made a joint venture company investment in the 737NG to be the only engine supplier. The trend in propellers is towards more and more blades. The CFM 56-7 with a 5.1 bypass ratio has 56 shrouded, wide chord, titanium blades, which makes it essentially an incredibly quiet, vibration-free, 56-bladed propeller.
The 737NG flies at 340 knots just on one engine – 10 knots faster than a P-3 cruising on four engines. A 737NG fails to leave the gate because of an engine issue 3–4 times every 1000 flights. In-flight engine shutdowns take place every 333,000 flight hours – that is one every 3.8 years of continuous flight. The engine comes off the wing for service every 20,000 hours or after every two-and-a-half years of continuous flying. The MMA CFM 56-7 maintainer will become the USN’s equivalent of a Maytag washing machine repair technician who is essentially out of a job because the washer never breaks.
Boeing drove home the advantage of having an already-flying solution by taking their product to the customer. In three sets of flight tests in 2002 and 2003 – two in the
Inside the aircraft was a mission system demonstrator to show the P-3 flight crew’s 21st century mission system hardware and software technology and concepts, including an invitation to the crew to bring their own video game software to the aircraft for immediate downloading.
These demonstrations essentially killed off the turbofan jet detractor lobby by demonstrating that a commercial jet could:
- Fly low and slow (and do so just as economically as a P-3)
- Manoeuvre at low altitude and simulate releasing torpedoes
- Operate just as well and safely on a single engine as two
These demonstration flights also included a maximum-power take-off and a maximum-brake landing as well as descents from 40,000ft in excess of 10,000ft per minute. These untraditional commercial airliner maneuvers showed the 737NG to be a (dark) horse for all courses and clearly turned the heads and opened the eyes of the USN aircrew who had grown up flying their beloved, noisy, vibrating P-3s wallowing and bouncing along through the weather at 280 knots and 18,000ft. Other MMA commercial features such as vacuum toilets, full integrated galley and reclining crew rest seats will seem luxurious to MPA air crew used to carrying on to their P-3s makeshift heating devices and using rudimentary bathroom facilities. The MMA aircrew could be forgiven for thinking they are flying in ‘MPA Business’ class and wondering whether they could claim frequent flyer miles.
Effectiveness of sensors at higher altitude has also helped to change the equation in favour of a turbofan jet as the 21st century MPA engine solution. For example, in littoral surveillance at 36,000ft, there is far less terrain blockage in overland surveillance as well as a potential ground or surface footprint four times that from 18,000ft. This also translates into a quantum increase in sensor search rate. For example, provided an active or passive sensor has the range to utilise the extra height, a 737NG MMA operating at 36,000ft can theoretically search four times the area than that which could be searched by a P-3C or Atlantic turbo-prop operating at 18,000ft. When added to a cruising speed 100-150 knots greater than turboprop MPAs, the turbofan jet MPA could theoretically search a swath five times faster. In addition, modern imaging radars and stabilised EO/IR systems relieve the crew from having to descend to low altitudes and into higher threat areas to gather critical intelligence against surface ships and small targets.
The Federal Aviation Administration (FAA)) rated Extended Twin Operations (ETOPS) for 180 minutes but confirmed 240 minutes based on 200,000 ETOPS flight. Hence, the single engine safety issue was all but ‘put to bed’ but there was one last lingering doubt about a commercial turbofan jet which was the issue of FOD ingestion at low levels. The CFMI technique of firing a chicken through the blades provided powerful evidence that the titanium blades would make mince meat (or rather chicken fricassee) of FOD. The only issue was when CFMI managed to fire a chicken which had not been defrosted into the engine. Clearly, this proved the engine cannot be FOD-certified against 10lb frozen seagulls.
The
Boeing has developed and already delivered many of the required ‘state of the art’ maritime patrol aircraft mission systems to BAE Systems. They are ready for installation in the Nimrod MRA4 airframe when BAE Systems overcomes the production woes and delays stemming from the difficulties of modifying an airframe that was not digitally designed and built. For MMA, Boeing was therefore able to offer a truly open architecture ‘Nimrod ++’ mission system. This used the Nimrod mission system as a start point, but then leveraged other Boeing strategic architecture initiatives, which ranged from the software-defined Joint Tactical Radio System (JTRS) through the Italian 767 Tanker and Australian Wedgetail 737NG Airborne Early Warning & Control (AEW&C) to E-10 (MC2A) and Future Combat System (FCS). This provided Boeing with a real advantage when compared to Lockheed who had evolved their Orion mission system somewhat piecemeal with the Update III, which added new modules for ASW (Block Modification Upgrade Program (BMUP)) and ASuW Improvement Program (AIP) but had never had the opportunity (or funding) to develop a new MPA mission system from the ground up.
Overall, the Boeing mission system story – which included a very smart, customer-friendly offer to turn over all the software source code to the USN – was considered compelling, and even exciting.
Weapons
When it comes to destroying targets, any aircraft without weapons capable of destroying the target is fundamentally just a bus without passengers. MMA will carry the entire gamut of weapons either on wing pylons or in a bomb bay. It will carry the traditional ASW and ASuW weapons such as mines, torpedoes, and anti-ship missiles, but many of these will not be state-of-the-art weapons because the threat drives the weapon evolution and the threat has been all about a ground threat for the last 10 years. For example, the standard Harpoon in USN inventory is the Block IC, which was first fielded in 1984 because it was optimised against a significant Soviet surface threat. MMA’s weapon suite will reflect the growth in the ‘J’ (joint USAF/USN) weapons like the Joint Common Missile (JCM), and Joint Air to Surface Strike Missile (JASSM) as well as the older air-to-ground weapons already in-service such as the Joint Stand Off Weapon (JSOW), SLAM ER, and Joint Direct Attack Munition (JDAM).
Other Benefits of Commercial-Derivative Aircraft for the Military
Boeing’s 737 commercial muscle will also produce huge benefits for the USN in terms of ownership and life-cycle cost. Full-motion aircraft simulators for the 737NG are developed and available all over the world. The airline equivalents of your local ‘Do It Yourself’ hardware stores stock 737NG parts all over the world. This alone will save the USN $1Bn over 10 years. The current 3300 USN maintenance force will be replaced by 840 contractor personnel generating huge manpower savings.
The Bottom Line
MMA will see in the centennial anniversary of MPAs and complete the evolution from 1930s single aircraft submarine chasers to a major network enabled warfare node capable of being a critical node in Network Enabled Warfare (NEW) (Figure 7).
Making a change from what has been a way of life for 34 years is very hard and will be hard. Embracing – and trusting – new technology is difficult. Venturing into a commercial way of doing business is like leaving a military aircraft womb.
But the USN has made an innovative, exciting and smart decision to go with the 737NG as their MMA selection for the 21st Century. The programme will generate excitement worldwide but, most importantly, it will echo right into the hearts and minds of the young MPA aircrew on whom the USN aircraft carriers will depend for protection for the next 50 years.
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