Auxilliary Fuel Tank

BBJ (Boeing Business Jet) can travel longer range compared to conventional 737 due to this extra fuel tank added in its cargo hold.

Depend on certain configuration per customer specific need, this extra tank can be placed at aft area of the forward cargo or forward area of aft cargo hold. This is to ensure center of gravity of the aircraft remain close to the center of the aircraft.

Each tank can hold around 1800 liters of fuel which if converted to kilograms will be around 1500 kg except the master tank which will have much higher capacity.

All fuel from auxiliary tank will be routed to the center tank of the aircraft before goes to the engines. What unique about this system is, fuel from auxiliary tank is "pump" to center tank using differential pressure from the cabin which will start once fuel in center tank dropped to certain level.

During initial refueling before the flight, the fuel will be added to the wing & center tank fuel first, extra fuel required for the flight then will be filled up in this auxiliary tank.

It's hard to see how this aux tank looks like, i found this extra tank kept in the store, it has been removed form one of the BBJ due extra cargo space required for the baggage. if you need extra range for the distance, cargo space has to be sacrifice for the fuel tank...

CFM Engine Using BioFuel

BBJ is using CFM56-27 engine for it propulsion system, what i want to highlight here is in June 2007, the engine manufacturer CFM International has successfully carried out an initial test of a CFM56-7B engine using an ester-type biofuel at Snecma’s Villaroche facility near Paris.

CFM56 engines are produced by CFM International (CFM), a 50/50 joint company of Snecma (SAFRAN Group) and General Electric Company.

The biofuel used for this test is 30 % vegetable oil methyl ester blended with 70 % conventional Jet-A1 fuel. This test was designed to check the operation of a jet engine using a fuel made from biomass, without making any technical changes to the engine. With this type of biofuel, the target is a net reduction of 20 percent in carbon dioxide (CO2) emissions compared with current fuels.

CFM is running engine tests to develop solutions based on mixtures of jet fuel and second-generation biofuels. For instance, it is currently focusing on the evaluation of alternative fuels made using biomass (offering properties closer to those of jet fuel), which also offer better environmental performance.

For alternative fuels to be used in the aviation industry, there are a number of major technology challenges that must be met, including energy density, thermal stability (avoiding coking at high temperature), use at very low temperatures (freezing) or high temperatures, lubricating effect with materials used, and the availability of mass production facilities worldwide.

Even though it is only 30% "vegetable oil" as a start, it is a major step toward greener emission from aviation industry.