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Almost every air force of the world is beset with long delays when carrying out depot-level maintenance. There is a need to streamline this maintenance and reduce the time during which an aircraft remains parked at the depot. High-velocity maintenance (HVM) could provide a solution to this problem.

The HVM concept first came to light when US commercial airlines had to reorganise depot-level maintenance. This type of maintenance is patterned after "cycle checks" carried out on the commercial airliners. A take-off and landing is considered as an aircraft cycle. These checks are performed on an aircraft after a certain amount of time or flight hours and are commonly known as A, B, C or D check.

The same concept is now to be introduced in the air force too. The idea behind this exercise is to bring an aircraft in for maintenance more frequently but for shorter durations of time.

For example, a cargo aircraft would be brought to depot once every 18 months instead of once every five years. A C-130 will remain at the depot for 12 to 15 days every 18 months, compared with 160 days at a time as per existing practice.

Reinventing depot-level maintenance

Robins Air Force Base in the US is a pioneer in reinventing depot-level maintenance and is undertaking the maintenance of the first C-130 to validate the concept by subjecting it to a synchronised, integrated, end-to-end process so that maintenance does not impede mission requirements.

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By GlobalData
“Almost every air force of the world is beset with long delays when carrying out depot-level maintenance.”

Through the HVM programme, the maintenance personnel will carry out in-depth inspection of various aircraft systems and preclude the possibility of confronting any surprises. Moreover, irrelevant paperwork is reduced, which saves the maintenance staff from slowing down work at the depots.

Besides saving time, such maintenance work frees flight line personnel, allowing them to focus on sortie generation rather than inspections and repairs. The result is quick sortie generation, reducing turnaround time of the aircraft and enhancing its efficiency.

During the programme’s implementation, aircraft will be inspected in the field before coming to the depot for maintenance. As a result, maintenance personnel will be far better prepared to get work done because they will know the requirements of the aircraft well before it reaches the depot, meaning a substantial reduction in the downtime of the craft.

For example, during the inspection of an aircraft, it was revealed that one of its major parts needed replacement. This replacement could have required numerous additional parts and tools.

As per previous arrangements, the plane would have come in for depot-level maintenance after remaining in the field for five to six years. It then would have been determined through an inspection that the replacement of such a major part was required. This major part, along with its associated parts and the needed tools, would be acquired while the plane was idle in the hangar. Now, the major part and its associated components are collected in advance so that when the aircraft reaches the depot the replacement can be made without wasting time.

As an aircraft gets older, it needs more care. A large number of aircraft are grounded every year, so it’s necessary that aircraft are made airworthy as soon as possible.

In actual practice, a large number of aircraft remain grounded and many aircraft fly with components under exceptional release, i.e. under certification by an authorised person who deems the aircraft safe for flight. The HVM concept amounts to an increase in the average age of an aircraft. Say, the average age of an aircraft in the total fleet of an air force is 24 years. By resorting to HVM, this age could be enhanced to 26.5 years.

When an aircraft is subject to HVM it remains under the constant observation of the maintainers. An engineering assessment and feedback from the field will indicate what has been happening on it and the problem is arrested before it develops into a formidable issue that could result in the grounding of the aircraft.

Testing the HVM concept

To test the concept of HVM, the right data is necessary, complemented by developing the right repairs and ensuring the availability of the required parts during maintenance.

“High-velocity maintenance amounts to an increase in the average age of an aircraft.”

Generally, it is observed that unscheduled maintenance causes the biggest delays. The HVM process is designed to reduce the waiting time for the mechanic. Some problems can be fixed straight away, while others will be documented and deferred. This helps maintainers fix the aircraft on their schedule, not that of the aircraft’s components.

Implementing this new concept can definitely incur some costs, such as increased investment in depot facilities, equipment and other capital needs to start with, but savings will be made in the long run.

A dramatic change

HVM is a dramatic change to the way aircraft maintenance is undertaken and aims to reduce aircraft downtime.

By increasing the speed of maintenance between the scheduled maintenance in the depot you can give the time saved back to the aircraft and increase its availability. It can be said that the increased availability of aircraft will almost have the same effect as buying a new aircraft.

To accomplish such maintenance effectively there should be a single, integrated logistics system that includes transportation, supply, maintenance and repair. There should also be continued investment in technologies for depots that could diagnose a problem without dismantling the aircraft.

Most importantly, there’s the need to follow best maintenance practices in air force depots.