CHRISTINA MACKENZIE / PARIS, STEWART PENNEY / ST ATHAN & FLEETLANDS
Tight procurement budgets have increased the importance of maintaining ageing military aircraft around the world
Although military aircraft manufacturers tend to concentrate on developing new aircraft and capabilities, the reality is that most of the world's air forces operate increasingly ageing aircraft, and maintaining them becomes more and more difficult as they become older.
Fatigue and stress play a part but industrial issues also come into play, not least the paucity of new programmes and production work, which is forcing original equipment manufacturers (OEMs) to find other means of keeping highly skilled personnel employed. As a result, more OEMs are moving into logistics and support, while procurement contracts increasingly include at least five years of some form of contractor logistics support. This adds a dimension - a seismic shift in the shape of the industry - to the complexity of maintaining old aircraft.
Although military aircraft, like commercial aircraft, undergo varying depths of maintenance, keeping combat jets airworthy is different. Combat aircraft fly less than airliners but low-level operations and high-g manoeuvring place a heavier toll on structures than a typical civil profile. Unlike commercial operators, which lose money if their assets are on the ground, air forces tend not to be concerned if an aircraft is in a hangar for a considerable period.
Most UK military aircraft, fixed- and rotary-wing, are maintained by the Defence Aircraft Repair Organisation (DARA), a Ministry of Defence agency that is increasingly having to compete for work that it and its predecessors have done for many years. Fixed-wing maintenance is concentrated at St Athan, near Cardiff, UK, and its helicopter and engine overhaul work is based at Fleetlands, near Portsmouth, UK.
DARA sees the whole gamut of ageing aircraft issues because it maintains the Royal Air Force's 1960s vintage BAC VC10 tanker-transports and all its fast jet types, the youngest of which, the BAE Systems/Boeing Harrier GR7, entered service as the GR5 in the late 1980s. The agency also performs upgrades such as the Jaguar 96 and Jaguar 97 programmes for the Sepecat-built fighter and is replacing the aircraft's Rolls-Royce Adour 104 engines with the 106 variant.
Reducing to produce
Avionics and systems upgrades have been used to address the sustainability of ageing aircraft, says DARA Harrier maintenance facility (HMF) production manager Glenn Jones. Avionics and systems can be impossible to maintain because core components are no longer available, a particular problem for avionics because of the short manufacturing life of components. This is partly overcome by acquiring large stocks of spares at service introduction. "Reducing to produce" is another means of acquiring spares by recovering components from scrapped aircraft, says Andy Lethardy of the HMF .
Another issue is the economic repair of components. Early in an aircraft's service life, it is cheaper to use a new item than perform repairs. Later, when either the spares stock is exhausted or the manufacturer is no longer in business, it becomes necessary to repair components that were once considered beyond economic repair, says Lethardy. DARA therefore has manufacturing capabilities and builds from pattern when the drawings are unavailable, which is often the case with ageing aircraft, says DARA Fleetlands site director Paul Jones.
When an aircraft is not upgraded, the problem can be finding suitably trained personnel. "Apprentices are trained for fly-by-wire and modern technologies, not old-fashioned equipment and old systems," says VC10 process manager Jeff Morgan.
DARA Jaguar facility manager Flt Lt Mark Sapsford agrees that upgrades help sustainability. "Jaguar 96 took the aircraft into the 20th century; Jaguar 97 took it into the 21st century," he says. The Jaguar was to have been retired by the middle of this decade, but Eurofighter delays mean Jaguar's out-of-service date has slipped to at least 2008, and probably later. As a result, some aircraft are being cleared to 6,800h of flying while others are being brought out of storage with only 2,000-3,000h. One Jaguar arrivedat St Athan after 12 years in storage, needing all intervening modifications, including the Jaguar 96 and 97 upgrades.
One reason for the Adour 104 to 106 engine change is to improve maintainability, but delays to the programme have a knock-on effect on the frontline fleet and the supportability of the aircraft. One aircraft was redelivered to the RAF 147 days late because BAE - the UK half of the Sepecat consortium - took 56 days longer than scheduled to provide the data for the upgrade, and components for the work were 68 days late. The conversion should take 60 days. BAE cannot supply a single set of data because each aircraft is different, says Sapsford. The aircraft were not built in a uniform way in the 1970s, and in-service modifications and repairs and different operational lives further complicate matters.
Maintenance squeeze
Maintenance delays and lack of spares increase the burden because the aircraft that are available fly more hours, which reduces the time before the next maintenance cycle. "So you get into a vicious spiral," says Kevin Sargent, DARA head of Fleetlands' rotary-wing operations unit.
Spares for the Panavia Tornado are owned and managed by the RAF, which can cause problems because the process is complicated, involving DARA, the RAF, the Defence Logistics Organisation (which manages the supply of spares and maintenance schedules and programmes) and the OEM. One proposal under consideration is for DARA to buy its own spares, which would ease the problem, says Tornado maintenance facility manager Jim Moore.
Lack of uniformity in structural repairs causes delays and problems, each occurrence requiring design authority approval. Ageing aircraft also tend to have common problems. Jones says the Harrier GR7 has problems with the aft bullet fairing that have worsened since the RAF began deploying the jet to Royal Navy aircraft carriers, which increases the aircraft's exposure to corrosive salt water spray. A systematic scheme to repair frame cracking around the forward engine nozzle has not been introduced. "The same area is repaired rather than beefed up because that could send the problem somewhere that cannot be inspected," says Lethardy. As a result, some aircraft have been repaired two or three times, requiring several repair schemes, says Jones.
Upgrades to helicopters also have an effect on their structure, tending to increase the machines' empty weight. The RN's Westland Lynx HMA8s are operating at maximum weight, says Sargent, which is putting additional wear on the lift frames. "Probably one in three Mk8s is given frame repairs," he adds. The fasteners in the frames are under increased stress and although the holes can be enlarged, this only works for a finite period, so the frames need replacing, which in turn requires the helicopter to be placed in a jig at Fleetlands. A second jig is being installed for this work.
Sargent says repair organisations can also perform work that OEMs are reluctant to do. Fleetlands, for instance, is rebuilding a Boeing Chinook HC2 that suffered a heavy landing by grafting on the rear end of another airframe, so maintaining the size of the UK's Chinook fleet. Similarly, France's SMA took two years to restore to airworthiness a Dassault Mirage 2000 that was severely damaged in a birdstrike.
Support from OEMs can be poor, say some DARA personnel, who believe this will resolve itself once each company has decided how it wants to provide support in the future. If an OEM is going to provide the service itself, it will not help suppliers such as DARA, says one source. But if the OEM decides to work with DARA, the situation should improve, the source adds. A lack of work in some OEMs' repair organisations means that where DARA once carried out most MoD overhauls of some items, the agency now has to share the work, which reduces its workload and makes its processes more expensive, says another source.
Reduced volumes mean it can be difficult to maintain a capability because not enough components flow through the system for personnel to maintain some skills, says Dave Edmunds, head of DARA Fleetlands' engines operations unit.
Operator conflict
There is a dichotomy between the needs of military and commercial operators, says Edmunds - commercial operators will pay extra for shorter turnaround times, but military operators want reduced costs rather than a quicker return of equipment to service. This can make it difficult to justify new equipment and capabilities, he adds.
New equipment needs heavy use to justify the investment, says Edmunds. As a result, the new turboshaft test cell at Fleetlands is compatible with all shaft engines in UK military service, rather than being dedicated, as were earlier test rigs.
In France, two defence ministry organisations are charged with maintaining military aircraft - SIMMAD (Structure Integr‚e de Maintenance des Mat‚riels A‚ronautiques) is responsible for management, while SMA (Service de Maintenance A‚ronautique) performs the work.
SIMMAD head Gen Michel Asencio says the organisation was formed in December 2000 to "optimise the availability of aircraft at lowest cost" by creating an organisation which has cut costs and the duplication that occurred when each armed force was responsible for maintaining its own fleet. It is only since 1 January this year that SIMMAD has had full responsibility for all 2,000-odd French fixed-wing and rotor aircraft.
"It is more important to have aircraft when and where you need them rather than aiming simply for a percentage objective of availability," says Asencio. But a French parliamentary report released in October last year shows availability has improved under SIMMAD's management. For example, Jaguar A availability rose from 71% to 77% between 1997 and 2002.
The SMA says that as a fleet such as the Jaguar approaches the end of its life, "we look at all the aircraft and decide which need the most repairs. These are then taken out of service and cannibalised so that all usable parts can be used as spares for the remaining aircraft in the fleet." Economies of scale are also achieved by working with the UK.
The 70-odd Franco-German Transall C160 transports are less of a success, however. The aircraft are 36 years old and must last at least another six years before they are replaced by Airbus Military A400Ms. Last year's report indicates the C160's availability dropped from 69% in 1997 to 55% in 2002 and annual maintenance costs are €180 million ($207 million). But Ascencio says: "The Transall does not pose any particular problems while awaiting the A400M."
SIMMAD awards maintenance contracts on a competitive, pan-European basis. Last year it awarded the maintenance of France's 14 Lockheed Martin C-130H/H-30 Hercules to Portugal's state-owned OGMA military maintenance company, which beat French company Sogerma to the six-year deal.
The SMA has a research and design centre to decide the most cost effective means of repairing an aircraft and to design a new spare part if necessary. "It could be cheaper and just as safe and effective to make our own spare part using new technologies such as carbonfibre to replace metal than to buy the ready-made spare part from the manufacturer," says a senior SMA official. "It is rather like replacing part of your car engine with a generic piece of equipment instead of the more costly spare made by your car's manufacturer," he adds.
Renovation requests
During an aircraft's life, the first important maintenance phase is renovation, says the official. "We're at this stage for the Mirage F1 and the Mirage 2000D." Renovation requests come from the operator "notably during exercises with other nations, which are a very good opportunity to note equipment and so on, which they may have and we do not", he says, or from the DGA procurement agency "during regular technical meetings with counterparts from other nations". The DGA decides whether to proceed, while the OEM or SMA will perform the work.
The SMA has three maintenance sites - at Bordeaux specialising in engines, at Clermont-F‚rrand for combat aircraft, and at Cuers-Pierrefeu for naval aircraft and helicopters. "We do not have to make a profit," says the SMA. "We do have the obligation of not losing money, but the fact of not having to make a profit means we can maintain our ageing aircraft at the lowest possible costs."
The manufacturer usually maintains an aircraft initially, with the SMA gaining the necessary experience to take over in the longer term. "The French state decided to maintain its own competence so that it can undertake long-term maintenance to counter the problems raised when the manufacturer stops making or maintaining the aircraft," says the SMA.
The second phase is preparing the aircraft for retirement. "We need considerable advance warning, usually three to five years, so that we can optimise the withdrawal process," says the organisation, and not have to retire an aircraft that has recently undergone a major overhaul. The last major overhaul is done three years before the aircraft is withdrawn. Spares stocks can also be managed "so that ideally, when the last aircraft in a fleet is retired, we have no or very few spare parts for it in stock".
Source: Flight International
