Source : The Indian Defence Review, © 1995 by Lancer Publishers & Distributors.
Introduction Maintenance of electronic equipment is now an advanced technology in which extensive use of In-Circuit Testers (ICTs), Automatic Test Equipment (ATEs), Built-In Test Equipment (BITE) is made by the maintenance staff. By the use of computers in maintenance support even further improvements are possible. The features that make avionics maintenance different from the rest are the imperative flight safety and air-worthiness, which place wide implications on the maintenance of airborne electronic equipment. This article brings out these special requirements and features and explains how the Indian Air Force (IAF) organises itself to meet the challenge. Many references to Civil Aviation are also made.
Today's fighter aircraft is aptly called Wings on Electronics. However, the IAF operates not only the modern aircraft such as MIG-29, Mirage and Jaguar but also older ones such as Hunter and Canberra. Likewise the IAF electronic equipment varies from valve versions to GaAs devices. The geographic spread of the units operating such variety of assets renders the management of maintenance activities more complex than the mere pursuit of air-worthiness and flight safety. Maintenance of avionics should not only be done but appear to have been done. Some third person must certify to the pilot or the passengers that everything is fit for happy landings. This concept is becoming more significant with the airline operators due to the increase in legislations and litigations related to flight safety. Something similar is true when it comes to military aircraft wherein Inquiries are invariably ordered into incidents, accidents and crashes.
Classification of IAF Equipment The IAF electronic equipment can be classified in a variety of ways as follows:
Conformance to Specifications: International organisations such as International Civil Aviation Organisation (ICAO), International Air Transport Association (IATA), Joint Aviation Requirements (JAR Europe), Federal Aviation Administration (FAA) of USA, Civil Aviation Authority (CAA) of US, as well as the Indian counterparts DGCA, IAAI and NAA are continually striving to lay down requirements for safe operations of air transports. The degree of stringency varies for light aircraft, wide bodied heavy transports and military aircraft. These are elaborated in Certificate of Air-worthiness (C or A), Permit to Fly, Air Operator's Certificate (AOC), Light Aircraft Maintenance Schedules (LAMS), CDSO schedules for military aircraft in UK and in Indian Air Force etc. Any operator, be it Airlines, Air Taxi or Air Force is expected to conform to specifications both for operations and maintenance as laid down by one or more of the above.
Operational Considerations:The effectiveness of a major system such as aircraft is defined by three considerations - availability, reliability and maintainability. Reliability and maintainability are two important subjects adequately covered in literature. Aircraft systems are designed for these attributes. However, in case of IAF aircraft the aspect of availability assumes significance due to the nature of our operations. Survivability and portability contribute towards availability and therefore, our designs and maintenance keeps these in mind. In addition to these stipulations, two other considerations direct the philosophy for maintenance.
Modifications: Changes made in aircraft sub-systems either to remove design defects, enhance capabilities or safety etc. are all required to be approved by suitable authority. Repair and maintenance to aircraft avionics is, therefore, not open to innovations at the technician level. Similarly, the spares used must bear type approval from the concerned Organisation.
Documentation: Recording of flying as well as maintenance work is a legal requirement since safety is now becoming more prone to litigations.. The maintenance activity is consequently required to be supported by legislation and certification. This involves two major types of documents; schedules to define the work content and log books to record whether the maintenance conforms to specifications. In IAF we have a form 700 whose sanctity for these purposes is religiously maintained. It is neither questioned nor compromised.
Maintenance Reviews: It is not feasible to inspect each and every aspect of maintenance at all its occurrences, therefore regular maintenance reviews are carried out to certify that maintenance practices are correct and directed to the laid down specifications of safety and mission accomplishment. In the IAF we have a Directorate of Maintenance Inspection for this purpose, whose teams visit each and every flying wing regularly.
Licensing of Maintenance Staff: British Civil Air-worthiness Requirements are published by CAA. This covers grant, extension and renewal of aircraft maintenance engineers licenses, and the approval and recondition of applicable training. This document also recognises CAO's licences. In the IAF the authorisation for maintenance is derived from the training imparted by the Air Force Technical College to officers and by schools to technicians.
Engineering Support for Maintenance: Requirements for engineering support necessary for grant of air Operations Certificate (AOC) by CAA are set out in the document CAP 360 Part 11, and this covers:
IAF and Civil Aviation
It is difficult to guess the manner in which operations and maintenance will stabilise with the Indian Air Taxi services such as East and West, ModiLuft, UB, Jetair etc., yet the glaring dissimilarities in the manner operations and maintenance are scheduled and carried out by civil agencies and the Air Force, are well known. The Air Forces are characterised by less flying per aircraft than the commercial airlines, but the low flying coupled with hard manoeuvres in military aircraft subjects systems on these aircraft to higher degrees of strain, For carrying out repairs in far flung locations the Air Force personnel are called upon to demonstrate higher standards to eliminate dependence on specialised engineers of the manufacturers. The access for reaching out to components and sub-systems is much smaller in a military aircraft than in a commercial transport plane. These factors contribute to the differences in maintenance philosophies of military and commercial aircraft fleets.
Maintenance Philosophy
The philosophy for maintenance of electronic equipment on aircraft was outlined for the first time by the FAA in 1960. Before that all aircraft maintenance was based upon the theory of preventive replacements in accordance with laid down life of components and sub-systems. It was a conservative philosophy in which the granted life was less than the life that was actually sustainable. Extensions were granted as the experience built up. This philosophy was not only wasteful but also hid away the premature withdrawals since these never took place.
Under the Maintenance Steering Group (MSG) programme of the FAA, the erstwhile philosophy of hardtime replacement was replaced by a logic based philosophy which provided for inspecting the sub-assemblies and overhauling them on-condition. It catered for an assessment whether a component failure would cause an immediate safety hazard or not. Whether it will abort the mission or its rectification can be deferred for a subsequent visit to the hangar. This philosophy however, placed a greater responsibility on the maintenance staff to make GO-NO-GO decisions in connection with prematured withdrawals, life extensions, flight safety etc., during aircraft operations and maintenance.
The present day maintenance philosophy of aircraft systems considers a few additional factors such as cost effectiveness, productivity and other economy oriented constraints. The main question is that of the ratio of downtime/servicing time to the flying hours logged.
In such a complex environment the question of maintenance is sought to be answered by classifying the maintenance activities as follows:
Maintenance Organisation
The IAF carried out all maintenance classified above, by a complex set-up. The I line scheduled servicing includes first sortie, turn-round and last sortie servicing and is done at the operating units under the guidance provided by CSDO maintenance schedules, The fault rectification and II line scheduled servicing is carried out at better organised facilities at Wings. The III and IV line servicing is more detailed, requiring longer hours off-flying and is carried out at specialised repair agencies which work like production units. The repair agencies are controlled by Maintenance Command whose only responsibility is maintenance, as opposed to operational commands who control the operations of the fleet.
Spares Support
The IAF inventory comprises items procured from a number of countries which follow their own numbering systems. The identification at component level is not exhaustively provided because the suppliers do not expect IAF to undertake repairs on some of the hi-tech devices in the UHF/SHF bands of frequency. In many cases western systems are integrated on Russian platforms. This makes the spares provisioning not only difficult but it inhibits exploitation of industry standard JIT or EOQ philosophies. However, the IAF has excellent experience in managing an 8 lakh inventory, effectively.
Manpower Resources
The IAF recruits 10+2 level students and converts them to the equivalent of ITI graduates within 2 to 3 years by a carefully drafted training methodology. Technicians come from a rural background but become capable of communicating and understanding technical matters in English, by the time they undergo the specified IAF training. Inspite of the fast turn-around due to the tenure policy and an initial term of only 15 years, the quality of our maintenance personnel is something to be proud of. They are capable of undertaking rectifications at farflung operating locations.
CONCLUSION
Smooth conduct of maintenance of IAF electronic equipment requires the support of specialised repair agencies which deal with specific technologies or applications. Naturally these will be geographically spread out. Much that we prefer to have these agencies communicate with each there for production scheduling and monitoring lead times, constraints such as security inhibit exploitation of modern marvels like data communication networks. There is a crying need for encryption equipment of MIL standards so that the IAF operations and maintenance can benefit from modern communication set-ups in the country.
There is just one more difficulty. The use of computers without inhibition. The fear of virus shies us from extensive dependence on computers, since some of the applications could be life-critical. There is also a requirement for a certification agency for software, in the country. The maintenance of software, the less said the better.
A major change in the stance of defence forces towards electronic equipment is the dilution of requirements for ruggedised systems. EMI/EMC, EMP hardening of TEMPEST technologies are being used only selectively. This has come about mainly to reduce costs, yet it helps us in two other major ways. The use of commercially off-the-shelf (COTS) equipment instead of militarised equipment enables us to use state-of-the-art technology rather than the older technologies. Secondly, it reduces our dependence on specialised repair agencies since the repair is available in the industry.
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