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Aircraft Reliability (And Availability)
Part of a business aircraft’s value is that it flies on your schedule- observes David Wyndham. If the aircraft is not available for service- cannot fly due to a mechanical problem or is significantly late departing- its value is compromised. The terms reliability and availability measure how well the aircraft satisfies transportation needs.

Reliability- or more precisely Dispatch Reliability- is defined as the percentage of departures that leave within a specified period (typically 15 minutes) of a scheduled departure time. Is the aircraft ready to fly when scheduled? Ninety-eight percent reliability is a standard that many business aircraft operators achieve.


Availability is defined as the percentage (typically measured in days per year) when the aircraft is ready for dispatch. Time spent in the shop either for scheduled maintenance or for an unscheduled (unexpected) event that requires special attention detracts from the aircraft’s availability. Due to many factors- aircraft availability typically is less than dispatch reliability.

If an aircraft does not make its scheduled departure- what is the reason? Weather- Air Traffic Control (ATC) delay- crew delay or maintenance delay? Weather and ATC are beyond your control- but the other two should be at - or very near – to zero.

CREW ISSUES
The crew needs to observe a duty day limit in order to maintain an alertness and high degree of safety- and in some cases in order to comply with Federal Air Regulations. Pushing the crew beyond these limits is not a good idea and may be illegal. But- the crew is responsible for keeping you informed of this limit and for making other arrangements if needed.

If your crews are routinely running out of allowable duty time- do you need to augment them with an extra pilot? It is not uncommon for global business jets to fly with three pilots on very long missions. Sometimes- an intermediate stop is needed to swap out crews. These situations should be planned for well in advance.

DISPATCH RELIABILITY
Dispatch reliability should be at or near to 100%. Can you remember the last time your car didn’t start? Neither can I… While the aircraft is a much more complex machine- the level of maintenance it receives should ensure reliable operation. A few years ago- an Aviation Manager and client of ours related this anecdote: He was called downtown to report to a Senior VP. When he arrived- the VP was irate. His flight was cancelled the day prior to its scheduled departure due to a maintenance issue. In other words- the aircraft was not available for the mission.

To make matters worse- this was the second time in less than a year that it had happened. Fortunately- our Aviation Manager was well armed with information and was able to show that the Senior VP happened to have the unfortunate distinction of being on the only two trips in the past two years where the aircraft was unavailable due to unscheduled maintenance.

A key to maintaining both aircraft availability and dispatch reliability is the quality and timeliness of the maintenance. If the aircraft breaks more often than rarely- do you need to replace the aircraft- get better training for the maintenance team or find another maintenance vendor?

Aircraft manufacturers are seeking ways to better monitor and predict the upcoming maintenance requirements without increasing maintenance costs by replacing or overhauling components that still have sufficient- safe operating life remaining.

One area that is relatively new for business aircraft is in-flight condition monitoring. Numerous operating parameters are measured- collected and reported to a maintenance analysis facility. The purpose is to correlate changes in the data with maintenance issues. The goal is to reduce unscheduled maintenance and possibly generate data that can extend inspection intervals- thus increasing aircraft availability and dispatch reliability.

This sort of data collection requires the cooperation of the aircraft owner and operator. The payoff may not be immediately obvious as it takes time to collect and analyze much of the data. If your aviation department has the opportunity to install and use such equipment- however- it may reduce surprises and be a worthwhile- long-term investment.

Do you have any questions or opinions on the above topic? Get them answered/published in World Aircraft Sales Magazine. Email feedback to: Jack@avbuyer.com

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