How Boeing’s 777X Folding Wingtips Actually Work

July 6, 2019

 

Much of the sour publicity surrounding Boeing’s 777X development has focused on delays due to the durability of the aircraft’s GE9X engines. Boeing plays down the hiccup and suggests the type’s folding wingtip system and in-cabin innovations will blow the competition away.

The 777X (777-8 and -9) was launched in November 2013. Within two years Boeing had received 326 orders for the type. “X” Customers included Lufthansa, Etihad Airways, ANA and Singapore Airlines.

Boeing had initially hoped to begin the 777X flight test program in March. But due to various events in the early part of the year, the target date was pushed back. In June of this year the aircraft finally made its runway debut, and showed off its (in)famous folding wingtips.

Following ongoing re-working of the components of the GE9X Boeing hopes to have the new variant flying by the end of 2019. Writes Aviation Daily, “GE will require several months to develop and test fixes to the engine and first flight now looks set to be more likely in the October-November timeframe.”

The aircraft is still slated for the commencement of passenger flights in 2020. And the company expects to deliver the first twin-engine, wide-body to Emirates by 2025 (even though the UAE carrier may defer its multi-billion-dollar order.)

The wing of the 777X is based upon the design of the 787’s wing. It has less of the sweep of the 787 but 10% more surface area (increased from 4,702 to 5,562 sq. ft.). The re-shaping has led to a higher lift-to-drag ratio which in turn increases usable fuel bulk from 320,863 to 350,410 lb.

The type will have a range of over 14,000 kilometers (8,699 miles).

Boeing’s motivation for its including folding wingtips within the design was not wholly steered by fuel economy. With a fully-extended wing span of 71.8 meters the new 777X falls within the ICAO’s aerodrome Code F. But with raked and folded wings (and a span of 64.8 meters) the type can comfortably arrive at gates designed for Code E. Aircraft currently in this group includes the current 777.

Are folding wingtips safe?

According to Boeing, yes! In May 2018 the FAA rubber-stamped Boeing’s new folding wingtip system. But public mistrust of the airline’s fastidiousness in respect of innovative technology is at an all-time high.

B777X in flight over clouds (rendering)
FAA rubber-stamped Boeing’s new folding wingtip system in May 2018. Photo: Boeing
In May 2018 the FAA was urged to issue special conditions in reference to the safety of the 777X’s wingtips. In the course of their deliberations the FAA demanded several assurances from Boeing.

The company was required to prove beyond doubt the viability of the wingtips’ load-bearing. It also needed to show how the wingtips affected ground handling in poor weather, and what alerts the crew would receive about a malfunction.

The FAA granted Boeing certification on the basis of the following provisions:

More than one means must be available to alert the flight crew that the wingtips are not properly positioned and secured prior to take-off.

In addition to a take-off warning, a means must be provided to prevent airplane take-off if a wingtip is not properly positioned and secured for flight.

The wingtips must have means to safeguard against unlocking from the extended, flight-deployed position in flight, as a result of failures, including the failure of any single structural element.

How do they work?

The exact details of how the wingtips operate have not been made public. But Boeing states that it approached the design of the fold mechanism, locking pins and latches with the same thoroughness as it would any of its flight control systems.

On landing, the wingtips automatically fold within 20 seconds of the aircraft slowing to 50kts. The display of malfunctions and “ready” statuses will be displayed on the cockpit EICAS. Should there be a malfunction this will be relayed to the pilots via a master caution light and audible tone.

In a statement to FlightGlobal, the company said of the wingtip safety compliance, “Boeing designs its airplanes so that redundant systems are independent, and failures or external threats cannot compromise both primary and backup systems simultaneously.

“The folding wingtips are simple and highly reliable with redundant deploying, retracting and locking mechanisms. We are designing the folding wingtips like every other flight critical system so they meet safety requirements.” 

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