High flyers can finally enjoy real espresso coffee mid-flight, and now there's authentic draught beer too.
KLM's beer trolley trundles down the business class aisles of selected European flights serving Heineken on tap, after years of experimenting with keg designs to produce a perfect pub-style schooner at high altitude.
It's quite the challenge, you see.
Aircraft are pressurised at 6,000 to 8,000 feet above sea level, an altitude at which a beer tap will "only dispense a huge amount of foam" explains Heineken's Edwin Griffioen.
"We do have dispensers that work on air pressure, but these were too big to fit in a plane," while CO2 cartridges used in home tap systems are banned from aircraft.
Another challenge: getting all the necessary kit into a cabin-friendly size, specifically a standard-sized airline trolley.
"It was one big jigsaw puzzle," Griffioen recalls. "The keg of beer, the cooling system and the air pressure compressor all had to fit in an airline catering trolley."
"In the end we had to leave out one of those pieces to make it all fit, so with pain in our hearts we had to leave the cooling behind."
Hang on – does this mean that the Dutch airline is serving warm Brit-style beer?
Not quite: four ice-cold kegs of beer are loaded onto each flight at Amsterdam Airport, with the trolley – created using a 3D printer – resembling "a giant Thermos flask" in which an insulated container keeps the suds under 5° C for a cold, crisp pour.
KLM's draught beer trolley is pressurised to compensate for the 'negative pressure' on board, so as to generate sufficient tap pressure for serving a refreshing beer rather than a glass of foamy head.
“We managed to set the diameter of the tap and the air pressure to exactly the right combination, which delivers at 36,000 feet (11,000m) exactly the same beer as you would get on the ground," Heineken's Griffioen beams.
The cost of creating this high-tech trolley means that, for now, there's only one in the entire KLM fleet, with the airline intending to roll it out "as much as possible for special flights and events."
KLM isn't the first airline to put a keg above the clouds, however.
Japan's ANA debuted a 'dry ice' tap system in 2010 on selected domestic routes out of Tokyo, with frozen CO2 stored in a low-pressure container.
As the CO2 changed state from solid into gas, it was piped into the container of beer to force the beer out the tap. But passengers felt the CO2-beer combo didn't taste nearly as good as the real deal, so ANA went back to cans of beer and sake.
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