Nimrod MRA4 makes debut at last

Nimrod is a legendary name, literally. In the Bible, he’s an ancient king of Babylon, described evocatively as ‘a mighty hunter before the Lord’. For the UK armed forces, it’s also a legendary name: the broad-winged marine-patrol aircraft that has been searching the seas for enemy submarines and suspect shipping for 40 years. More recently, it has become legendary for all the wrong reasons — for the cost and scheduling over-runs on its latest incarnation, the Nimrod MRA4. But the much-delayed aircraft is now ready for service. Has it been worth the wait?

At BAE Systems’ Warton site in Lancashire, the Nimrod MRA4 has an impressive presence. The biggest aircraft on the base, it is almost 40m long, with a similar wingspan and a distinctive bulbous shape, sharp nose and bristling aerials. ‘But it’s not entirely dissimilar to the Mark 2, which it’s replacing,’ said BAE Systems’ military liaison, Drew Steel, a former RAF officer who served his entire career on the Nimrod fleet. ‘You’d have to be a pretty heavy-duty anorak to spot all the differences.’

This encapsulates many of the problems that MRA4 has had in terms of perception. It looks like the Nimrod MR2 and uses the same fuselage; it’s often described as a refit, which has made the aircraft’s chequered history difficult to understand. But, as Steel took great pains to point out, MRA4 is to all intents and purposes an entirely new aircraft.

‘Only 10 per cent of what you see on the Tarmac comes from an older aeroplane,’ he explained. ‘It’s literally just the shell of the fuselage, the cigar-shaped tube. Everything else is new: the wings, the engines, the flight deck, the onboard systems and layout.’ The older aircraft in question was derived from the DeHavilland Comet, the world’s first significant airliner, and that is an indication of just how long the Nimrod name has been around. It replaced the Avro Shackleton, which was derived from the Lancaster bomber. Removing the last echoes of that vintage was key to the MRA4 project, but that is not apparent until actually entering the aircraft.

Going inside an MR2 is like stepping back in time. The flight deck, although it used modern equipment, had the layout and instrumentation of a 1950s airliner, with a four-person crew — pilot, co-pilot, navigator and flight engineer. Back in the body of the aircraft, the mission team sat in a layout derived from the Shackleton. The workstations — all different, designed for a single operation — were angled in such a way that the team couldn’t turn around and look at each other, or communicate at all without intercom. The commander’s desk was at an odd angle to the axis of the fuselage, which left him prone to airsickness. ‘There was never any great thought given to the human factor,’ Steel added.

In the MRA4, the flight deck has been brought more up to date, but it is still a familiar look. ‘We’re not talking 25th Century Buck Rogers stuff,’ Steel said. ‘It’s a 1990s airliner glass cockpit, derived from an Airbus A340; it’s proven kit that’s well established; the navigation system is essentially a Boeing 737-800 set-up, which has millions of flying hours. But the magnitude of the change from what we had before is significant.’ The flight crew also now have a display screen showing mission information and targets, unlike in the MR2, so they can set their own course rather than depend wholly on instructions for the mission team.

Inside the mission area, the differences are also clear. The team’s workstations have a common design and feel, and are arranged either facing along or perpendicular to the fuselage axis, so the crew can look at each other; this, Steel said, helps to increase their effectiveness.

The on-board systems have also been updated. The MR2’s systems could cope with about 200 pieces of information before they started to ‘wobble’, as Steel put it. ‘The screens can’t cope with the volume of information and they flicker, and the crew wobbles as well.’ On the MRA4, system integration means that five times that volume of data causes no problems and new intelligible plots on the displays mean that the mission commander has a clear view of the situation.

But to a casual observer, the main difference is the engines, a cause of a tricky problem for BAE Systems’ engineers.

The engine placement on the Nimrod is probably the biggest flashback to its Comet precursor. Rather than hanging from nacelles below the wings, or clustered around the tailplane in the familiar configuration for a large jet, they are smoothly incorporated into the root of the wing. But the MR2 used Rolls-Royce Spey engines, high-bypass turbojets, which are fairly small. The new aircraft was to use Rolls-Royce BR710 turbofans, more than 25 per cent more powerful than the Speys and much larger.

‘The project specified the Rolls-Royce engine, but it wasn’t designed to be incorporated into a wing,’ said Steve McGregor, who has been design and development director on the MRA4 since the beginning of this year and is responsible for bringing the aircraft into service.

‘We couldn’t mount the engines below the wings,’ he said. ‘We take off power from the engines to generate electricity for the on-board systems and it’s far less complicated to do that when the engine is integrated into the wing. That’s why we ended up with the much longer, broader wings on the MRA4.’ The new wingspan is more than 3m longer than the MR2.

The engines also give the MRA4 one of its most important advantages over its predecessor; they increase its range. ‘Once this big platform is out there, it’s very important to keep it there for a long time,’ Steel explained. ‘It reduces the number of handovers you need and whenever you hand over to another aeroplane you have the potential to drop information. The longest test flight we’ve done on the MRA4 was 12 hours and that used 43 tonnes of fuel. The total capacity is 50 tonnes.’

In-flight refuelling could be an option, and the first production MRA4 is fitted with a refuelling probe. But this is not qualified for use, and after the crash of an MR2 in Afghanistan in 2006, caused by fuel pumps, and a fuel leak during air-to-air refuelling on another MR2 a year later, the RAF may decide that the increased endurance negates the need for refuelling. Besides, Steel pointed out, it’s not practical to task a Nimrod crew with very long missions; exhaustion would impair them.

The endurance also explains the smaller than originally envisaged fleet. ‘If you look at a two-hour on-station mission, the range of the MRA4 covers a large proportion of the world,’ Steel said. ‘From RAF Kinloss, where they’re based, they could cover all of north Africa, much of the Middle East, a big chunk of Russia and the whole north Atlantic. The MR2 was restricted to western Europe and a little bit of north Africa.’

McGregor confirms that this was a factor in reducing the fleet. ‘The increased endurance was always part of the specification,’ he said. ‘Once we’d confirmed we could do that, there were careful calculations to determine what was the minimum number we could have to fulfil the role mapped out for the system.’

For Steel, one of the most vital parts of the refurbishment also resulted from that longer persistence. ‘We had to have a kitchen,’ he said. ‘Nimrod crews are legendary for the amount they eat. You have no idea how welcome a hot sausage is on a long flight.’



Sidebar

Flight of fancy - The long and difficult journey of the MRA4, from conception to launch

The Nimrod MRA4 has had a troubled history. First commissioned in 1993 to replace the Nimrod MR2 (the Mark 3 was an early-warning aircraft), the original plan was for BAE Systems to supply 21 aircraft, envisioned as a refit of the MR2 fuselage.

Trouble began almost from the start. The RAF supplied MR2 airframes for conversion, but none of them were to a common standard, so BAE transferred the task from a subcontractor to its own facility at Woodford in Cheshire. The Woodford team discovered there was a problem with the design of the new wing, which led to the project being put on hold while a new wing was designed. By 2004, the cost of the project had risen from a projected £2.8bn to £3.5bn and the schedule had slipped by six years. The number of aircraft in the order slowly slipped, from 21 to nine.

Each aircraft cost around £400m — four times the initial estimate — and the in-service date is autumn 2010, seven years behind schedule.