747-400ER

The 747-400ER is the rarest production 747 of the modern era. Six were built, all for Qantas, and no other airline ever ordered the passenger version.

It was launched on 28 November 2000 on that Qantas order, and the first was delivered on 31 October 2002.

What “extended range” bought

The -400ER offers the operator a choice rather than a fixed gain. The extra capability can be spent one of two ways:

• 805 km more range, or
• 6,800 kg more payload

It is the same underlying increase in maximum takeoff weight, applied at the airline’s discretion depending on the route.

The body fuel tanks

The range comes from tankage, and the engineering is more interesting than the numbers. The -400ER can carry one or two additional 3,240 US gallon body fuel tanks in the forward cargo hold.

These were built by Marshall Aerospace using metal-to-metal honeycomb bonded construction — a technique that achieves an unusually high ratio of fuel volume to dry weight. Every kilogram of tank structure is a kilogram of payload lost, so on an aircraft bought specifically for range, tank weight is the thing that decides whether the exercise is worth doing at all.

The same technology was later applied to body tanks for the Boeing 777-200LR and the P-8A Poseidon.

The routes it was bought for

Qantas used the -400ERs on Melbourne–Los Angeles and Sydney–San Francisco — sectors that a standard 747-400 could not fly with a commercially useful load, particularly westbound against the winds and out of Melbourne in summer.

That is the entire commercial case for the variant, and it explains why nobody else bought it. The number of routes that need more than a 747-400 but cannot be served by anything else is very small — and by the early 2000s the 777-300ER was arriving to serve most of them on two engines instead of four.

The freighter did better

The cargo version, the 747-400ERF, sold 40 aircraft — nearly seven times the passenger version. Freight operators genuinely needed the extra payload, and had no equivalent alternative to switch to.

Qantas retired its 747 fleet, -400ERs included, in July 2020.