Plan Landing

Next generation efficient aircraft such as the Boeing 787 Dreamliner and Airbus A350 XWB have faster cruising speeds which, combined with the efficient use of fuel, are now making possible more point-to-point direct flights over longer distances than ever before. Alongside the cost-effective move to two engines as opposed to four, these continued innovations in engines and airframes are enabling airlines to set new records for non-stop flights.

In September of last year, Singapore Airlines took delivery of the very first Airbus A350-900 ULR – an ultra-long-range, twin-engine aircraft that can fly for up to 20 hours non-stop. Using this model, Singapore Airlines launched its non-stop flight from Changi International Airport, Singapore, to Newark Liberty International Airport, New York. Travelling approximately 16,700 km in around 18 hours and 45 minutes, it set the new record for the longest non-stop passenger flight in the world.1

Maintenance considerations

The larger engines needed to power these ultra-long-haul flights have been developed to be both more fuel efficient and reliable. For example, advances in engine design mean that more efficient thrust can be generated by fewer, lighter blades. This helps to provide propulsive efficiency while also reducing the weight of the engine. As well as making longer non-stop routes commercially viable, new technologies have the potential to deliver broader financial benefits to airlines. Jet fuel will always be a key cost consideration for operators, and so any technology that helps to deliver greater fuel efficiency will be welcome.

However, these advancements alone are not sufficient to guarantee efficiency. The distances these planes will travel invariably creates higher temperatures in engines - which can have a significant impact from a maintenance perspective. One consequence is that the higher engine temperatures can increase the temperature of the turbine engine oil (TEO) being used. This can have a negative impact on TEOs not designed specifically for such conditions, potentially resulting in unwanted and costly carbon deposits in the engine – a process otherwise known as coking. This can be very costly from a maintenance perspective and can necessitate more frequent engine overhauls.

Mitigating costs

Choosing the right TEO is one of the most effective, yet simple, ways for airlines to handle the maintenance pressure of ultra-long-haul flight on their engines. Just as the trend towards longer flights is the product of decades of manufacturing advancements, engine oils have likewise been adapting over this time to continue to service the requirements of the latest engines. As engine efficiency and reliability has been improving, even with higher turbine temperatures, engine oils with better thermal stability, along with enhanced anti-coking and high load carrying ability have also been developed.

Using high thermal stability or high-performance capability oils can play a key role in helping airlines to ensure their engines are equipped for the demands of longer flights. Oils that are designed specifically to provide long-term thermal and oxidative stability can continue to provide engine lubrication at higher temperatures, for longer. This reduces in-service maintenance burden, which creates further costs and disruption, therefore increasing aircraft utilisation and resulting in saved costs overall across the engine’s lifetime. For example, using AeroShell ASTO 560 (AeroShell’s HTS oil) for PT6 engines operated by a large US based Piltatus PC 12 operator can extend the time between overhaul from 3,000 to 5,500 hours when combined with other good maintenance practices.

An increasing trend

The push to put ultra-long-haul flights on the market shows no signs of slowing and passengers can expect more direct flights over longer distances in the coming years. In the weeks following Singapore Airlines’ setting a new flight time record, Philippine Airlines announced a direct non-stop service to New York JFK from Manila – a 16-hour flight.2

While there is much to be celebrated about the return of ultra-long-haul routes, there is a need to ensure that it doesn’t come with a higher maintenance bill. A proactive strategy in choosing the appropriate engine oil will ensure that airlines are prepared to compete in this market without paying a higher price in maintenance costs to do so.

1Singapore Airlines, “Singapore Airlines To Launch World’s Longest Commercial Flight”, (12th October 2018) https://www.singaporeair.com/en_UK/us/media-centre/press-release/article/?q=en_UK/2018/April-June/ne2018-180530

2World Airline News, ‘Philippine Airlines launches its nonstop New York route’, (31st October 2018), https://worldairlinenews.com/2018/10/31/philippine-airlines-launches-its-nonstop-new-york-route/

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