Airbus is working on a 7,000nm A330-900


A330-900 new capabilities

The present target is to certify the A330-900 to a Maximum Take-Off Weight (MTOW) of 242 metric tonnes. This gives room for 89 tonnes of fuel in the wing tanks of the A330neo when carrying 287 passengers and their bags in a three-class cabin. The tanks can hold 107 tonnes, so there is no lack of space for added fuel. What’s missing is weight margin.

The way then to increase the range is to increase the fuel that can be loaded before the aircraft reaches its MTOW. Airbus is now working on increasing the limit to 251 tonnes. This gives nominal room for another nine tonnes of fuel.

But the increased loads on the aircraft requires local beefing of the aircraft structure. Allocating 0.5t for this beefing, we end with 8.5t of increased fuel capacity when the cabin is full.

The range is then increased to 7,000nm when using Airbus loading and flight assumptions. To compare the A330-900’s range with 787-9 we need to compare apples-to-apples regarding the measurement conditions. Airbus and Boeing use different assumptions for passenger+bags weights, en-route reserves and how to stow passenger bags.

Measuring of maximum range by Airbus and  Boeing

The airliner OEMs agree on how to measure an aircraft’s maximum advertised range. The aircraft is loaded to 100% load factor with passengers and their bags. Then fuel is added up to the aircraft’s Maximum Take-Off Weight (MTOW) or to full tanks, if it comes first.  But Airbus and Boeing differ on several areas in how the aircraft is loaded and with what margins the flight is done.

The Boeing assumptions, in its new STD rules, are closer to how airlines apply rules of loading and margins for flight (the previous rules, IAC, were worse than Airbus rules). Airbus flies with lower weights for passenger+bags. It counts 95kg/109lbm per passenger with bag instead of Boeing’s 225lb/102kg. Boeing also counts the container weights for the containers holding the bags; Airbus doesn’t.

Airbus also applies tighter route reserves for unforeseen winds or route changes, 3% instead of Boeing’s 5% (most airlines use 5%). The OEMs  agree on the circling minima, 30 minutes, and alternate distance, 200nm.

The companies also differ on how the cabin is made up. Airbus’ count is with a three-class cabin (Business, Premium economy and Economy) while Boeing stays with two classes (Business and Economy). A three-class cabin weighs more but holds fewer passengers.

A like for like comparison

The result is the advertised maximum ranges for Airbus and Boeing aircraft can’t be compared. One needs an aircraft performance model to load all the OEM data and assumptions and then change the rule-set to a neutral one.

When we do this, we get the following results:

  • The present 242t A330-900 has a maximum range of 6,100nm with 294 passengers in a normalized two class long-range cabin. We use the IATA recommended 100kg per passenger with bag.
  • Flying with the same ruleset, the 254t 787-9 flies 292 passengers 7,700nm.
  • If we change the MTOW of the A330-900 to 251t, we increase the range to 6,700nm.

The prototype A330-900 is just about to fly from Toulouse Blagnac. It has finally got its Trent 7000 engines from Rolls Royce. The engines, which are lightly modified 787 Trent 1000-TEN engines, were delayed by a hick-up in the TEN test program (an improved compressor seal turned out to be no improvement at all, back to the original design).

The test program will go on until late spring 2018, when the first A330-900 will be delivered to its lead customer, TAP Portugal. This will be a 242t aircraft. The certification of a 251t version is a follow-on activity. It’s not clear when this version will hit the market.

When it does, the gap to the 787-9’s range will close, but there is still a 1,000nm difference when comparing apples-to-apples. A 6,700nm nominal range for A330-900 creates a very useful aircraft. The weight variant with additional 600nm will be popular with the airlines.

To read the rest of the article Login or Subscribe today.