It was only recently when I stumbled across the newly developed eFan engine by Airbus Group on twitter. I am certainly the Airbus eFan will revolutionize the airline industry, or at least greatly contribute to it. Having worked in the airline industry for over 7 years as a Ramp Agent, Operations Ramp Controller and Flight Dispatcher; I’ve come to an understanding how and why certain operational decisions are made by airlines. It is usually not all about cost, but it can sometimes be a contributing factor.
You might be thinking, what has this got to do with the eFan? The eFan will completely revolutionize the way airlines operate in the future. The eFan may actually help airlines once again become hugely profitable companies. Many people may not understand the connection between fuel and aircraft limitations. Before I get started, I’ve listed some basic facts you need to understand about aircraft. These limitations apply to all airlines in all countries around the world. Mainly due to the inescapable forces of gravity.
Keep these facts in mind. A typical Airbus A320 burns approximately 2,500kg (5,500 lbs)** of fuel per hour in flight. For the average Airbus A330 the fuel burn is approximately 5,000kg (11,000lbs)** per hour. As you can imagine for long haul flights, that is a huge amount of fuel and weight. Not to mention the cost of purchasing that amount of fuel. A330 flights from Hawaii bound for Australia typically held a total of about 60,000kg (132,000lbs)** of fuel onboard at take-off. That figure would vary from flight to flight, depending on forecast winds, availability of company approved ETOPS suitable airports enroute, destination weather forecasts, etc etc. The point is, fuel weighs a lot and costs a lot for airlines to purchase. As aircraft fly, they burn off a lot of fuel, resulting in the total weight of the aircraft to reduce by the amount of fuel burned off in flight.
Another key point you need to keep in mind when planning flights; aircraft weight limitations. Every aircraft, from the Airbus A380 right down to the smallest Cessna 152 have weight limitations that legally cannot be exceeded. It is illegal to intentionally exceed aircraft weight limitations! (The only exception would be for the flight crew to declare an in-flight emergency.) The key weight limitations that immediately come to mind are the Maximum Take-Off Weight (MTOW) and the Maximum Landing Weight (MLW). These weights will vary from one aircraft type to another. You CANNOT exceed either of these weights! Fuel weighs a lot and MUST be included towards calculating the MTOW and MLW. With a lot of fuel on board the aircraft, that reduces the amount of remaining weight available for passengers and baggage before reaching the Maximum Take-Off Weight. The next questions is; How much fuel is going to be burnt inflight? If you Take-Off at your MTOW, will you burn enough fuel to be at or less than your MLW upon arriving at your destination? (Remember, you CANNOT exceed either the MTOW or MLW.) You may want to make sure your at or below your MLW upon arrival at your destination. If not, you will have to sit in a holding pattern until you burn enough fuel to get to your MLW. Not to mention, the airline will not pay for the flight crew to burn unnecessary fuel in a holding pattern when they could be on the ground prepping for the return flight. That’s bad planning and they have a schedule to meet. As you can see, the thought process behind how much fuel is legally required, versus the MTOW and MLW play a huge part in airline operational decisions.
Coming back to the eFan, with all of the facts listed regarding the cost and weight of fuel and its effect on aircraft weight limitations, this changes quite a few things. Obviously the eFan does not run on fuel, it runs using electricity stored in batteries. I am not an expert on batteries by any stretch of the imagination, but I think it is safe to guess that batteries weigh the same if they are fully charged or completely flat. Assuming that is the case, this means the actual Take-Off Weight will be the same as the Landing Weight. (Provided nothing is thrown off or dumped from the aircraft in-flight). I can already picture this making flight planning a lot easier in the future.
Which brings me to the next step regarding the eFan engine, the endurance. This seems to be the largest limitation the eFan currently faces. The average flight time for the eFan 1.0 is approximately between 45 minutes and 1 hour before recharging is required. If the problem of endurance is solved, this will change almost everything with regards to airline operations. I believe there are at least two viable solutions that may just solve this.
The first thought I had was using an Auxiliary Power Unit (APU) to provide electrical power directly to the eFan engines. An APU is used to provide electrical and hydraulic power on the aircraft when operating on the ground or parked at the gate. It is also used to provide air conditioning on the ground. All airline aircraft and corporate jets have APUs installed. When an aircraft is parked at the gate, if you see exhaust fumes coming out of the aircraft tail, that is from the APU. They run on the same fuel used by the jet engines, but the rate which fuel is burned is a lot lower. The A320 APU typically burns approximately 150kg (330lbs)** of fuel an hour. (Remember the A320 typically burns approximately 2,500kg (5,500lbs) in-flight.) That’s a 94% reduction in fuel burn per hour. That alone is huge! As it turns out, the Airbus Group and Rolls Royce have been working on this concept for some time, and it is called E-Thrust. Ok so my thought was not original, however it is most certainly on the right track. Which brings me to my other potential thought.
The other thought I had to possibly extend the current limitation of the eFan endurance, is by adopting some wind turbine technology on a much smaller scale. What do I mean by that? Basic wind turbines spinning in the airflow as the aircraft flies enroute. Aircraft such as the A330 have what is called a Ram Air Turbine (RAT), which is a propeller blade which sticks out into the airflow to generate emergency electricity. Typically these are very rarely deployed and are only for in-flight emergencies. When they are deployed they increase the drag, which is something you want to try and avoid as much as possible. However, what if a slight increase in drag was the small price to pay for a large increase in electrical power? How?
Every wing tip, due to the nature of aerodynamic airflow in-flight, create wingtip vortices. I realise aeronautical engineers have designed wingtips to reduce drag caused by the wingtip vortices, but it has not been completely eliminated. What if you placed a small wind propeller behind both wing tips, using the wing tip vortices and airflow to spin a small wind propeller? Each propeller would be spinning in the opposite direction, but it will still work. With a small propeller spinning at a high speed in-flight behind each wing tip, it could be used like an alternator system in cars with a belt to turn an alternator or multiple alternators inside the wing area. Will this idea work? I don’t know for sure, but I wanted to make sure the idea is out there for the Airbus Group or anyone else to consider it as a possibility to improving the endurance of the eFan aircraft. I believe it has potential to work. This potential idea will not eliminate the need for batteries on board the eFan aircraft.
Having worked for several airlines in the United States and Australia, once the eFan aircraft officially receives government certification, batteries will still be required. That, I am absolutely certain of.
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