Watch: What is inside a B777-9 test cabin?

One of the most highly anticipated premieres in the aviation world is that of the Boeing 777X series. 

The latest iteration of Boeing’s popular long-haul airliner has not had an easy development process, to say the least.  

The Boeing 777X aircraft family, which comprises the baseline 777-9, a shortened 777-8 and a 777-8F freighter (a 777-10 stretched variant had previously been proposed, but has yet to materialize), was expected to be in the market by 2019, but things did not turn out according to plan. 

Technical issues have continued to emerge during the development process, resulting in repeated delays in the certification process. On top of that, external developments not directly attributable to the B777X program, such as the B737 MAX debacle and the COVID-19 pandemic, have also taken a toll on Boeing’s business, causing further delays. 

As a result, the Boeing 777X did not complete its first flight until 2020 and is not expected to enter service until at least 2025. 

Boeing, however, has not missed a chance to showcase the 777X at several major international air shows, such as those taking place in Singapore, Dubai, Farnborough, and Le Bourget.  

On board the Boeing 777-9 

At the last Paris Air Show in June 2023, not only was the public able to witness the rather impressive capabilities of Boeing’s new airliner during a customary flight display, but the American manufacturer also welcomed a limited number of journalists on board one of its testing 777-9s. 

In a rare opportunity to witness a side of the aerospace industry that usually remains behind-the-scenes, AeroTime was able to have a look inside the first Boeing 777-9 ever built (registration N779XW), while it was sitting on the tarmac between flight displays. 

Not surprisingly for an airframe that has been used intensively during the B777X flight test program, N779XW’s cabin had been turned into a giant flying lab, brimming with all sorts of measuring equipment. 

The cabin, which in a standard two-class commercial configuration would seat more than 400 passengers, was arranged as a large diaphanous space fitted with rack upon rack of instruments. Even the lateral walls, bare of wall finishings and fixtures, added to the work-in-progress vibe that pervades the place.   

The cabin felt cramped at some points, and it was necessary to pay attention to where you put your feet, given the phenomenal quantity of cables that crisscross the cabin, often protected by rigid metal sheaths.  

These are the nerves of the instrumentation system, bringing in vast amounts of data collected by sensors located all throughout the aircraft. This data flow is then monitored and analyzed in real time during flight tests by Boeing’s engineers, who sit at screen-fitted workstations along the sides of the aircraft. 

Cables, computers, and precision instruments are expected to be found in this environment. But what seemed to arouse the curiosity of pretty much every visitor was the presence of what appeared to be several large black metal barrels at the front and back of the cabin.  

Those, it turned out, contained water that acts as a ballast. The different sets of tanks are linked by a network of pipes allowing engineers to transfer water between them, filling them up or emptying them in order to simulate different weight distributions during flight tests.  

This is not the only weight testing device onboard the aircraft. The cabin is also fitted with designated spaces prepared to hold lead-laden pallets, which serve the same purpose. 

Testing different weight distributions is essential to better understand how the aircraft behaves when its center of gravity shifts.  

Another curious element found on board the 777-9 test aircraft was a prop placed there for visiting media, rather than part of the testing equipment. Towards mid-cabin, an arched panel several centimeters thick and running floor to ceiling, the whole height of the cabin’s side walls, showed the difference in cabin width between the 777X and its closest competitor, the Airbus A350. 

Unique features of the Boeing 777X 

To gain a good glimpse of two other distinctive elements of the Boeing 777X, you had to get outside the cabin. 

The foldable wingtips are unique to the 777X. But why would Boeing over-engineer this part of the wings?  

By having foldable wingtips, the 777X benefits from the aerodynamic advantages of a larger wingspan, while keeping the aircraft within the size limits that allow the aircraft to be categorized as Category E (instead of the more restrictive Category F) while on land. Being classified as Category E expands the potential number of airports that can handle the 777X. 

A switch in the cockpit triggers the wingtips’ straightening process, while the system folds them automatically upon landing when the aircraft reduces beyond a specific speed. 

The massive GE9X engines were also eye-catching, with a constant stream of visitors queueing to get a photo taken in front of them. It is the most powerful airliner engine in the world and was developed exclusively by GE for the 777X. 

The road to market 

If all goes well, the 777-9 is expected to enter service by 2025. 

The original launch customer was meant to be Lufthansa, which ordered 34 of the type back in 2013. But after the German flag carrier changed its mind and reduced its order to just 20 (plus 14 options), the honor of being the launch customer passed to Emirates, which has placed the largest 777X order to date at 115 aircraft (also reduced from an initial 150-strong order).  

As of July 2023, Boeing has received 363 orders for different versions of the 777X, with the most recent of those being a 20-strong order placed by a resurgent Air India in May 2023.  

Other prominent carriers that have ordered the 777X in its different versions include Cathay Pacific (21), Etihad (25), Qatar Airways (74), IAG (18), Singapore Airlines (21), and All Nippon Airways (20). 

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