The Airbus A321XLR is in the final stages of its journey towards certification. The extra-long range Airbus narrowbody is the latest offering from the European OEM and has already joined the order books of some of the world’s leading airlines. Airline orders so far include American Airlines (AA), United Airlines (UA), Qantas (QF), IndiGo (6E) and Wizzair (W6). This month, we gained exclusive access to the first long distance route proving flight of the type, kicking off a series of flights the aircraft will have to complete on its journey to certification.
So, what exactly is a proving flight, and what goes into successfully managing the aircraft and crew? We joined the Airbus team on board Airbus flight AIB02AB to find out.
What is a route proving flight?
Route proving is a common phrase referring to Functional and Reliability Testing (FnR), essentially an international flight testing campaign that contributes to the upcoming EASA type certification required for new commercial aircraft.
The main objective of route proving is to demonstrate that the aircraft’s systems are practical, reliable and effective in typical service conditions, commonly referred to as ‘systems maturity’. To do this, the aircraft must fly for around 100 hours over 10 days without powering down any of its systems. The flights undertaken are designed to mirror the flights that airlines will likely use the aircraft for, from simulating different inflight weather and climate conditions to demonstrating the ability to turn around quickly at a destination airport. Our flight takes place around two hours after a previous flight around the Mediterranean (AIB01AB), and will be followed by a flight around the UK and the Canary Islands (AIB03AB) shortly after.
Our flight is the first of the longer route proving flights; an 11-hour round trip from Toulouse to the Northern Polar region and back. Deeparting around 21:00 local time , we take a more Easterly track on the way up and a more Westerly one on the way back down. The plan is to return by around 08:00 the following day. In fact, once we’re done, F-WWAB will have been flying for 22 of the preceding 24 hours.
Who is on board?
On the flight deck are three pilots, Olivier Falipou, Sebastien Audet and Gilbert Savary, all experienced Airbus pilots. Their job is to fly the aircraft in shifts to best manage the test schedule. Also on the flight deck is Rémy Vallois, Test Flight Engineer. Rémy occupies the center jump seat position monitoring and testing aircraft systems throughout the flight.
Towards the rear of the aircraft you will find Jim Fawcett and Jean-Philippe Cottet, Airbus’ senior Flight Test Engineers for the program. We recently met Jean-Philppe when we interviewed the A321XLR’s display crew at the Paris Air Show. The Flight Test Engineers will define the structure of the flight from two monitoring stations in the economy cabin. They measure vital parameters via computer screens and feed instructions via intercom directly to the flight deck.
Also in the cabin are Ground Test Engineers Thibaut Guillaume and Hervé Quesada. Jim describes Ground Test Engineers as ‘walking encyclopedias’ of the aircraft and its systems as they are responsible for proving the effectiveness of pretty much every system that isn’t directly flying the aircraft. On this flight, they are also testing the practicality of the aircraft for cabin crew, using the galleys to simulate a typical meal service and delivering a typical, albeit intimate, aircraft safety briefing.
And then of course, there’s us! I am pleased to say I am the first civilian (non-Airbus employee) ever to fly on the A321XLR, which is pretty special. We’re also joined by several members of Airbus’ external communications and audiovisual teams. A huge thank you to Sam Rizzo for helping us be here, and to Sylvain Ramadier and Arthur Allen for their help with media.
And they’re off…
After shadowing a preflight briefing in which we learned we were not expecting any significant weather on-route, we boarded F-WWAB at around 20:30 local time.
Following a further safety briefing from Ground Test Engineer Hervé, we proceed to take our seats in the ‘business class’ section of the cabin. Alpha Bravo is one of three Airbus A321XLR testbed aircraft, but the only one fully fitted with mixed class passenger seating. This is the aircraft that will shortly go on to test fly full simulated passenger loads of up to 200 people.
At 21:00, it’s time to go. We are taken a considerable distance by the pushback tug, so the aircraft performs a relatively short taxi to runway 32L at Blagnac. We depart on time and head North out of Toulouse into an incredibly clear sky. Thanks to Airbus’ wonderful hospitality I am able to experience the takeoff from the second jump seat in the flight deck. I notice a slight difference during the departure – the APU is powered on until after takeoff. The APU (Auxiliary Power Unit) is typically used on the ground in normal operations. Sebastien explains that taking off with the APU on is just one of many conceivable scenarios an airline crew might experience, and that this is a great example of how these route proving flights test system maturity.
Chicken or Fish?
After settling back into my seat the first meal of the flight is ready. There are two options – Chicken or Fish. For fans of the 1980 movie ‘Airplane’, the joke is not lost on the flight crew, and the test pilots are required to select different options just as airline pilots do. (Yes, I know it was Steak in the movie). I go for the chicken option, which is a very tasty fillet served with Polenta, a bean salad, bread and butter, a cheese box (because France) and a sweet Almond tart dessert. This was followed up almost immediately by a large sandwich, which I missed due to being busy nerding out on the flight deck (being born in 1990 I have only vague memories of open-door cockpits on commercial jets, so I wasn’t going to miss the opportunity). In addition to the surprisingly tasty food, an almost bottomless supply of fresh coffee is available.
Down to business – what are we actually testing?
It’s now around 11:30 pm, and I decide to head to the back of the cabin to chat to Airbus Flight Test Engineers Jim and Jean-Philippe. The two engineers have been pivotal to the testing and certification of countless Airbus civilian and military aircraft over the years, including the Airbus A380 and A400M.
I take a seat in one of the monitoring stations. In front of me is a familiar picture – a PFD. The Primary Flight Display (PFD) is a common sight to any pilot – an artificial representation of the aircraft’s attitude, level and speed. The screens have tabs which allow the user to scroll through a deep dive into pretty much any aircraft system. Jim explains that this essentially gives the Flight Test Engineer an immediate view of the data that is buried in the digital pages of the Electronic centralized aircraft monitor (ECAM) on the flight deck. We can see everything from flight control positions and navigation data to the electrical loads and temperature readings throughout the fuel tanks.
Jim now talks through the specifics of what we’re testing tonight, namely the cabin and fuel systems, which have been notably modified compared to the existing A321. We will also be testing some specific scenarios linked to Polar navigation, a relatively new area for the narrowbody A321. Jim clarifies what we’re looking for at the Pole: “Polar navigation can refer to operations in the far north or far south of the globe. In those areas the aircraft has to use a true heading reference rather than a magnetic heading reference. The aircraft systems have to be configured to make that change. We want to check that when we fly into a polar region those systems kick in, both automatically and manually”. The pilots are alerted to change the heading reference to ‘true’ approaching a latitude of above 73 degrees north or below 60 degrees south. If the pilot does not make the change, the autopilot performs this action and an aural alert is issued to the pilot. I am later invited to the flight deck to watch this in action.
Jim also explains that whilst we’re effectively testing everything as part of the 10 day period, there is an added focus on the systems which are new and unique to the XLR, namely the fuel system computer and the flight control computer. They are being tested for what is referred to as ‘system maturity’ – essentially their ability to operate constantly and under varying circumstances as they might in an airline environment. This is done by operating a large number of short flights, interspersed with a small number of long ones, and changing configuration between each.
Whilst we are talking, I notice one of the pilots heading to the back of the aircraft to take a break, and decide this is a good time to ask Jim about how crew rest works on the A321XLR. The duty hours and rest times on board Airbus test flights are set out in the company operations manual, just as they would be at an airline. For an 11 hour flight, the Airbus manual requires three pilots and a minimum of two Flight Test Engineers. The pilots tell me that they typically take shorter, more regular breaks of around 1.5 hours every 2 to 3 hours. The Flight test engineers work slightly more flexibly depending on their workload and the circumstances.
“The definition of the ‘crew rest area’ is up to each customer. On this test aircraft we’ve opted for a class 3 crew rest area, which is dedicated seats in the cabin sealed off with a curtain”. – Jim Fawcett.
Typical long-range widebody aircraft will have a permanent crew rest area situated below the cabin. These are pretty uncommon on single aisle aircraft that don’t typically perform such long flights. For class three crew rest, the operator can reserve either a single business class seat or entire row of economy seating for a resting crew member. On this flight, it seems the crew prefer a row of economy seating to lay down.
Following our chat, another member of the crew alerts us that we are getting our first expected glimpses of the Aurora Borealis. This is a first for me, so I’m straight back to the cockpit and the cabin lights are dimmed for a better view. Nature doesn’t disappoint and we are treated to a brilliant light show for nearly two hours.
With that done it’s time for my first attempt at some shut eye, I head back to the business class seating and manage to get a few hours of nap time before I am woken to the news that we are ready to witness the automatic heading reference system change Jim explained to me earlier. The test works perfectly, both annunciating the change and automatically switching over as we pass 73 degrees North. Soon after we begin a gentle but noticeable 180 degree turn to head back South. It was also interesting to note that the aircraft had switched to communicating exclusively using CPDLC. As we were now in one of the less eventful phases of flight, we chose to take another short rest break.
The journey due north and then immediately due south is a strange one for your body clock. The sun rising and setting either side of you gives you the feeling of experiencing multiple sunsets and sunrises. I’m reminded of Jim’s words about how rest breaks are carefully calculated and how key this would be if I was on the operating crew.
Petit dejeuner
Before I knew it we had around 4 hours to run back to Toulouse. After being treated to some more stunning views on the horizon, breakfast was served as we approached the northern coast of Scotland.The breakfast was a slightly odd affair featuring a hot chocolate brownie and custard. Strange, but enjoyable. This was accompanied by a baguette, coffee, apricot jam, yogurt, orange juice, and a selection of miniature croissants (again, because France). I may have gone back for extra croissants.
The heat is on
We’re now just under 2 hours from landing in Toulouse, and for the first time I notice a series of devices attached to the back of the business class seats. I seek out the oracle that is Jim Fawcett for an explanation.
He explains that these are temperature probes positioned throughout the cabin. Surprised I hadn’t noticed them before, I went for another wander towards the back of the aircraft. In addition to temperature sensors, microphones are placed intermittently throughout the cabin. Jim explains that during earlier test flights, metal dummies of various sizes are installed in the seats that replicate human body heat. This aids the crew in understanding the temperatures each area of the cabin is likely to experience. In order to accommodate up to three classes of travel, the XLR is equipped with three climate controlled cabin ‘zones’ (instead of the two zones found in other Airbus narrowbodies). The microphones were installed to measure background cabin noise, gaining an understanding of the likely noise levels passengers will experience in a narrowbody aircraft over much longer flights.
Noticing we have reached the top of descent, I craftily relocate myself to an economy window seat to get a better view of the landing. My preference for economy Airbus seating is somewhere around 22A, where you get a great view of the high lift devices and ground spoilers in action. I also find that keeping an eye on the flaps gives me a better indication of how far through the approach the aircraft is. After a steep descent aided by the speedbrakes, we make a perfectly smooth landing on Toulouse’s runway 14R, followed by another very swift taxi back to the Flight Test Center amidst the small city that is Airbus Toulouse.
It’s hard to understate just how enjoyable this flight was. Test flights can give the impression of being fiercely private, even secretive. In reality, route proving is a series of logical, practical tests that prove the aircraft and its systems are ready for the flying public. Airbus is anticipating the A321XLR will receive certification from EASA in 2024, and after witnessing the natural synergy and professionalism of the Airbus crew as they went about ticking those boxes needed to get this new aircraft to the airlines, I would say they are well on track.
We will be sharing a full video trip report on this flight soon. Keep an eye on this article, subscribe to our YouTube channel, and follow our socials to see it.
Cover photo: Wim Callaert, JetPhotos
