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The Gospel according to Airbus

by the Rt Reverend Friar Walter Waldeck. New convert and Training Captain A340 SAA.

Converting to your spouse’s religion when getting married is a bit like converting from Boeing to Airbus. You don’t really want to, but to keep the peace you’ll do just about anything! And man, what a crazy religion this is!
How could they all trace their beginnings back to Kittyhawk, just like the Jews and Muslims to Abraham, and then trudge down such radically different design paths?

Oi vey! These Philistines have taken the Holy Book of aircraft design and desecrated it! Heathens!
Who would design a commercial airliner with the side-stick of a fighter jet? And thrust levers that work more like switches compared to the push-pull throttles of Boeing? An audio panel that defies logic! And as for the FMGS! (That’s Airbus lingo for Flight Management Computer) Whose dark sense of humour lay behind that design? Attila the Hun?

It all worked just fine before so why did they have to go and change it? Simple really. Like faith evolved into many denominations of the same thing so too did aircraft design. And just like religion and politics are a recipe for an argument, so too are pilots discussing the merits of Airbus over Boeing. In the end though, you arrive at only one conclusion. It’s all the same – just different!
I converted to the A340 early last year at that Mecca of aircraft design: Toulouse. Holy Moses what an experience that was! Having done the factory conversion for the Boeing 767 in Seattle, I was keen to compare it with the European Reformationist’s course. Most of my airline career had so far been spent on various Boeings with a brief mystical dabble on the A300 before I was hastily guided back to the Path like a kid off an Ouiji board.
Leaving the Boeing fleet for an A340, I felt like Martin Luther. Either you’re headed out into the wilderness, or you’re going to discover something really mind-blowing out there.
The very first thing my elder converts warned me, with an ominous whisper was, “Don’t compare the two – ever! You’re with company A now, – leave company B behind!”
And they were right. You can’t compare Boeing with Airbus. You have to open your mind to a new way of doing things, a different logic. The Damascus experience; aviation style!
To start with: Fly By Wire. What a wonderful design! There is no mechanical coupling between the side-stick and the flight controls, saving enormous weight and mechanical complexity. Previously the exclusive domain of the fighter pilot, the system makes use of 3 primary and 2 secondary computers to analyze the pilot’s inputs, determine their validity, then apply the controls, using hydraulic power in a fashion that won’t overstress the airframe. It practically makes it impossible to stall the aircraft! The system will limit your angle of bank to 67 degrees, while it won’t allow you to pitch beyond 30 degrees nose-up or 15 degrees nose-down. In an airliner you don’t need more than that.
In an emergency you’d have to lose all five flight control computers, and even then you have a mechanical backup system.
When you first get to fly the simulator (which handles identically to the aircraft) you have to be careful not to over-control the aircraft, as the flight control computers have a set of criteria they analyze. These are called ‘Laws.’ Normal Law, Alternate Law and Direct Law. The computers shuttle between these ‘laws’ at various times and for various reasons.
Depending on the stick displacement the flight control computers will determine what roll “rate” you’re looking for. In simple terms, Direct Law would see the computers manipulating the flight controls to your command much the same way as in a conventional aircraft. At other stages, for example, a crosswind landing: they will look at the roll “rate” commanded by the pilot, and then apply sufficient aileron to achieve that rate regardless of the airspeed. For example: in a Cessna 150 you may need full stick (hence full flight control deflection) to maintain the wings level. While with FBW, the computer can give you full control deflection even if the stick isn’t all the way over since it’s looking at giving you your desired “rate,” no matter how much (or little) aileron is needed to achieve it.
It’s these little eccentricities that require serious understanding of the systems. Another good example is the ‘auto-trim’ function. If you push the stick forward in any aircraft, you trim in the same direction don’t you? Same with the A340 only it does the trimming for you. Now if you didn’t pay attention during the conversion you would have forgotten that the auto-trim locks out at 100 feet agl on the approach before landing. So if you’ve been slightly high on the approach, it will have trimmed that huge stabilizer nose down, which won’t matter much until you start the flare to land – and then realize with a thump the reason you ran out of elevator authority! Old chopper jocks are notoriously famous for “stirring the stick” but even they were humbled to realize that the best results come from flying the aircraft with your thumb and index finger alone. In the arena of manual flying – less is more. Meaning that if you require a 30-degree bank angle, put the aircraft in that position, then leave it alone. The FBW will ensure that it remains there. (To emphasize the point our instructor told us to imagine the stick is covered in dog s***t. To much hilarity he told us not to touch it unless we really had to!)
Once you understand how these laws work, she’s a beaut to fly. Having said that, de-crabbing with rudder and a side-stick just doesn’t feel the same as on a Boeing. But there I go comparing again! (That’s another 20 lashes from the Airbus Monks!) There are simply too many innovative designs to list them all here but one that really impressed me was the fuel system. Fully automatic, it requires the minimum of intervention to shift the fuel between the 8 tanks to the engines. Like the 747-400, (here I go again!) the A340-600 stores six and a half tons in the horizontal stabilizer. But unlike the 400 where you use it as soon as possible (otherwise you exceed the cg limits when the wing tank fuel is depleted,) the A340 periodically shifts fuel forward and aft to ensure minimum aerodynamic down forces on the tailplane thereby reducing drag and saving fuel.
Concorde did the same, so obviously it’s not a new idea, but still very effective. While I’m on the subject of fuel, I must just mention a very interesting snag I had on a direct flight from New York to Johannesburg a few months ago. It illustrates how far this industry has come.
Somewhere over the Atlantic I was awoken from my bunk with the news that we had a ‘fuel problem.’ I can tell you there’s nothing to bring you out of a deep sleep quite as fast as a vision of rowing the oceans in a yellow dingy.
It transpired that all the fuel quantity gauges (which are digitally displayed on a screen) had failed – indicating a problem with one of the Fuel Control Management Computers. After several resets of the computers, all with no luck, we decided to pick up the Satellite phone and call our maintenance experts back home. (“Houston …we have a problem.”)
They couldn’t advise us much beyond what we already knew. Terminating the call we continued searching for answers from the electronic library on our laptop computers before attempting yet another system reset. At that moment the Sat-phone rang with news from our engineering boffins that they had been monitoring our inputs on telemetry and were confirming the procedure we were now trying would indeed work. They had determined from remote system analysis that one of the fuel computers was corrupting the other and needed to be de-powered.
Two minutes later – end of problem.
What this illustrates is the degree of assistance available on a new generation high tech aircraft – naturally within the ground support structure of a technologically advanced airline. It doesn’t help to fly the most advanced aircraft in the world if you don’t have the ground support to optimize the operation.
It certainly is reassuring to be able to draw from as many resources as possible, especially when you have a problem over a remote part of the world.
While it is common to see more computer glitches on Airbus than Boeing, it’s very uncommon not to be able to reset them. Personally, I still think Boeing is a nicer “pilot’s” aircraft to fly. Airbus is built for the computer geek generation that honed their skills on Microsoft Flight Simulator while the rest of us were out chasing chicks and flying taildraggers. But pay no attention – that’s just the ramblings of a heretic. Airbus have done a great job of engineering-out a lot of conventional aircraft undesirable characteristics, and they’ve certainly made infinitely more information readily available to the crew. But it’s still ultimately the pilot who remains both aviation’s strongest and weakest link.
Now let me begone back to the monastery before the cyber inquisition finds me and burns me at the silicon stake. All together now. “Hommmm.”

Note:
I’ve kept the substance of this article deliberately vague in order to not give my friend Gary Wiblin too much help in a wager we have yet to undertake.
Ever sat in the back of an airliner and wondered if, in the event of the pilots becoming incapacitated, you could land the beast – based only on your light aircraft experience? (Like Charlton Heston and the ‘hostie’ in good old Hollywood style…) Well that’s Gary’s next challenge. At some stage we’re going to get him into the A340 simulator and without any help whatsoever see if he can return it to terra firma.

Ladies and gentlemen, place your bets.

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