TECHNOLOGY ADVANCES

Airbus brake-to-vacate technology has wide-ranging applications

A380 developments include runway performance tool that can improve business aviation safety.

By Peter Berendsen
ATP/CFII. Boeing 747, MD11


Author Berendsen over southern France in the left seat of F-WWOW, the original A380 prototype used for flight testing.

When Airbus engineers worked on the A380 design, they realized that such a heavy aircraft would probably create a lot of wake turbulence and a need for more separation for following aircraft.

As runway capacity is at a premium at the world's airports, a need for quicker runway exits at predetermined taxiways seemed obvious to Airbus engineers.
A lot of American professional pilots will say, "Sure, that's my daily job—I will land safely and exit quickly. I get paid for that."

But Airbus engineers believe in cockpit automation, since they have to sell their aircraft to a fast-growing worldwide market with limited supplies of qualified and experienced pilots. They imagined a system where pilots would enter a runway and specific taxiway intersection in their FMS, and then let the autobrake system slow down the aircraft at such a precise pace that 10 kts taxi speed would be reached at that exit.

Brake use and heat would be minimized, turnaround times reduced and runway occupancy time (ROT) kept to a minimum. Airport capacity would be improved markedly—especially on foggy days (low-visibility operation)—if most aircraft had such a system.

Airbus named the system brake-to-vacate (BTV) and first flew it in 2005. It is now an option when you order your A380, and will be offered on smaller Airbus jets in the future.
But, from my perspective as a believer in pilot skills and pilot-directed use of automation, the really interesting aspect of this system is something else.

For certification, any system in aviation needs to have warnings that inform the pilot if things don't go as planned. In the case of the BTV system, warnings were needed for an unstable, too-high or too-fast approach, a long flare or any other condition that would make it impossible for the autobrake system to slow the aircraft down within the available runway length.

In order to calculate the precise deceleration and braking intensity necessary to exit at a predetemined point, you need to input a lot of data. You need runway location and length, airport geometry, precise aircraft position, groundspeed (GS) and trajectory, aircraft actual weight, performance data and more. In short, the system needs to know exactly where the runway is, where the aircraft is, and how they relate to each other.

And yes, these data are exactly the same that you would need to predict a successful landing.

So, as Airbus engineers designed the BTV system to a certifiable state, they added 2 features—runway overrun warning (ROW) and runway overrun prevention (ROP). ROW will warn a pilot on short final if he/she is poised to overrun the landing strip. ROP will apply maximum brakes and instruct the pilot to deploy maximum reverse if he touches down anyway, in order to achieve a minimum speed at the runway end and overrun.

A hands-on demo

Berendsen (L) and Airbus Senior VP & Test Pilot Claude Lelaie prepare for departure in the spacious front office of F-WWOW.

To demonstrate this new concept, Airbus invited me to their facilities at TLS (Blagnac, Toulouse, France) to fly and see this system at work.
A380 serial number 1 is registered F-WWOW. This big lady is the original prototype and test aircraft. Now she was parked on the ramp in front of the Airbus flight test building in the southern part of TLS.

After a detailed briefing with engineers and the flight test crew, we boarded the huge aircraft. The interior was not at all luxurious. Instead, there were rows and rows of water tanks to simulate various CG locations.

Cables to flight test instrumentation were taped to the walls and a full flight test engineer station, with repeaters of cock­pit instruments and other parameter displays, was installed near the center of the main deck cabin. You can walk all the way to the back on the main deck and then take the aft stair to the upper deck, where a glass dome in the ceiling allows observation of the empennage.

On the forward part of the upper deck a few passenger seats offered moderate comfort. To complete my interior walkaround, I took the forward stair back down to the spacious entrance area. From there, 3 steps lead up to the flightdeck, which is arranged at a midlevel between upper and lower decks.

In addition to the 2 pilot seats in the roomy flightdeck, there are 3 full observer seats. Large windows and comfortable crew seats make the A380 front office a very desirable workplace.

Map display, zoomed down to airport diagram, shows selected runway and available runway length. BTV exit still needs to be selected.

The man responsible for the entire A380 flight test program, Airbus Senior VP & Test Pilot Claude Lelaie, took the right seat. I was invited to the left seat and we started to go through the pre-takeoff routines.

I quickly felt at home—2 years earlier I had been here for my first A380 flight experience.
The A380 cockpit is a modernized version of the Airbus family of aircraft flightdeck, and it should be easy for Airbus pilots to transition to this type.

There are, of course, a number of differences, one of the most not­iceable being that data are entered after placing the cursor in the correct field with a cursor control device (CCD). There are 2 of these on the center pedestal, one for each pilot. Similar to the pistol grip in Gulfstream's Plane­View cockpit, the CCD allows data entry in a comfortable way, even when in some turbulence.

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