Introduction & History
Since the starting days of aviation, the technology has improved and new records were often achieved; aircraft could reach higher altitudes, became faster, and could fly longer distances. When it comes to longer distances, there is no single definition.
According to the Federal Aviation Administration (FAA), a flight of more than 16 hours is considered an ultra-long-haul flight. However, other definitions put the start of an ultra-long-haul flight at the 12 hours mark. This fact indicates there is no clear definition and only an approximate value can be assumed.
In addition, the differentiation can be made by flight distance covered. In this case, there are also two different options: calculating the great circle distance (shortest way between two points) or by ground distance traveled. Depending on wind or other influencing factors, even long distances are faster and more economical to operate.
A look into history clearly states that the technology to fly distances of more than 17,000km is available for more than 30 years when a Qantas aircraft mastered a distance of 17,016km in 20:09 hours. However, the economical result was not interesting, as the revenue did not cover all costs.
Why is ULR now interesting?
Since October 2018 Singapore Airlines serves the routing Singapore – New York with an A350-900ULR in 18:45 hours. Why?
As recently the fuel prices were declining and the technology improved (more efficient engines), many airlines do see a way to operate these routings in a commercially appealing way. With dropping fuel prices, it is profitable even when using four-engine aircraft. However, operation with two engine aircraft is more effective, as fuel consumption is reduced. As fuel prices might increase again, the fuel efficiency of the engines is a crucial aspect of the operation.
Besides the fuel efficiency of the engines and the fuel price, the weight of the aircraft is the main contributor to fuel consumption. The heavier the aircraft is, the more fuel is needed to operate. The goal is to use a material that is as light as possible, but also strong and reliable.
|Aluminium||Steel||Titanium (very expensive)||Graphite-epoxy (composite material)|
A potential future lies in the development of microlattice by Boeing. It consists of 99.99% air and is lighter than a dandelion.
Even though technology improved and ULR flights are possible also from a financial perspective, there are some open questions to be considered, before opening such a route:
- Are there enough rest facilities for the crews on board?
- What if a passenger dies during flight?
- Is special medical service on board needed?
- Is ETOPS also applicable for such long flights?
- Is cabin circulation with fresh air guaranteed?
Besides these questions, the main factor is passengers’ acceptance. Are passengers willing to stay almost a day in an aircraft? As the passenger’s comfort and acceptance might be a key factor of the idea, the cabins and the service available to passengers will have to be optimized. Airbus is undergoing a trial to establish sleeping berths in the cargo holds. A further improvement, such as a gym, better lights, and nicer air are already implemented or are under consideration.
The limit is no longer the endurance of the engines. It is the endurance of passengersAlan Epstein