Emirates Airline chief executive Tim Clark is campaigning for another thrust increase for the Boeing 777X engine family as negotiations over the final details of the aircraft design enter a crucial phase ahead of an expected launch at the Dubai Air Show in less than two weeks.
Boeing and GE Aviation have decided to remove a water injection system that would have provided more effective power for the GE9X turbofan engines, Clark tells Flightglobal.
As a result, the larger 777-9X may need more thrust to lift the maximum amount of payload during the hottest month in the Middle East, as higher temperatures weaken the power produced by the engines with a 132in-diameter front fan.
"The only solution is more thrust, probably 105k," Clark writes in an emailed response, referring to a rating of 105,000lb-thrust for the GE9X.
The demand by Emirates – possibly, the biggest customer for the 777X programme – could put Boeing and GE in a difficult spot with other customers who do not need the higher thrust ratings needed only at a few airports for about a month a year.
Boeing declines to comment on specific demands by Clark, but says it is "working closely with all of our customers to ensure we develop and offer an airplane that delivers ground-breaking value for our customers".
GE, meanwhile, says it "continues to work with Boeing to ensure we meet the thrust requirements for the airframe".
The GE9X is already slightly more powerful than originally conceived as a "100,000lb-thrust-class" engine at the beginning of the year. By June, GE executives raised the highest power setting of the GE9X to 102,000lb-thrust, but that still was not enough to meet Emirates' desire for maximum lift during the hottest month of the year in Dubai.
High temperatures in the region reach a peak in August of around 49°C (121°F) with up to 25% humidity, according to the National Centre of Meteorology and Seismology in Abu Dhabi.
Instead of increasing the thrust of the GE9X still higher, Boeing and GE considered inserting a water injection system into the engine. Such systems were once used to boost the take-off power of first generation turbojets. GE still uses water injection for industrial power turbines that are derived from aircraft engines.
Max Kingsley-Jones contributed to this report.