Advertising
  • News
  • Airbus reveals A380-linked pilot systems secrets

Airbus reveals A380-linked pilot systems secrets

Until now, Airbus has been keeping secret two radical new safety-related avionics solutions that have emerged during its A380 development programme, but which are likely to be certificated soon for all its types.

The manufacturer happens also, in the course of A380 tests, to have broken the world record for landing weight, but says it has not bothered to declare that because it thinks it will soon break the record again. On 8 December 2008 an A380 landed at Istres air base, France, at a weight of just under 600t. Airbus says the landing weight was 591.7t.

RUNWAY OVERRUN

Meanwhile, Airbus has developed a runway overrun warning and protection system that should be certificated in July. Known at Airbus as the ROW/ROP, the system will be standard on the A350 XWB, but an optional retrofit on the rest of the Airbus fleet.

Airbus
 © Airbus

It is a development of the planned A380 system called brake-to-vacate (BTV), which allows a crew, once they know which runway they will be landing on, to pre-select the runway exit they wish to use so they can minimise runway occupancy time.

The aircraft then automatically brakes to achieve that exit. Airbus's BTV system specialist and experimental test pilot Capt Armand Jacob says it is particularly useful when visibility is extremely limited, or when carrying out land-and-hold-short operations in the USA.

RESOLUTION ADVISORY

In addition, the manufacturer has flight-tested a system that will enable the autopilot to fly TCAS (traffic alert and collision avoidance system) resolution advisory profiles. This would replace the present system in which, on receipt of a resolution advisory, the pilot has to disconnect the autopilot, transfer his attention to the resolution advisory indicator on the primary flight display, and fly the advisory manually.

Also the new system, if the pilot happens to be flying the aircraft manually when a resolution advisory occurs, enables the pilot to fly it manually using the flight director as guidance, instead of the TCAS resolution advisory demand - although that will also be visible. This system, dubbed AP/FD TCAS, has been independently validated for performance and consistency, and it should be certificated in August. It will be retrofittable to all Airbus fly-by-wire types, says the manufacturer.

Airbus has developed the AP/FD TCAS system because air navigation service providers have long reported that pilots often exceed the vertical speed rate and the altitude change indicated by the normally quite delicate resolution advisory demand, and this has the potential to compromise traffic separation.

There is also a certain perversity in the current status quo: at present when a resolution advisory demand is triggered, the flight director bars are retracted, the autopilot has to be tripped out, and the vertical manoeuvre has to be flown according to the indications of a display that is rarely used - unlike the flight director.

The ROW/ROP system was developed in response to the now-acknowledged need to find a solution to runway overruns, because they are the single most common of all aircraft accidents. Even if they are usually non-fatal, they are frequently damaging and costly. ROW/ROP works using the same data inputs, monitors and software algorithms as BTV.

The two fundamental data inputs on which both systems work is the aircraft's constantly updated real-time GPS position, and a terrain database that has precise runway location and dimensions embedded in it, along with full airport details.

The continually updated comparison between the aircraft's actual position in three dimensions and the relative position of the runway enables the system to assess whether, according to the actual approach performance, the aircraft can land safely within the runway length, whether wet or dry.

If it cannot, the pilots are warned aurally and on the navigation display (see picture and system explanation), giving them the option of going around, or of landing and being provided with maximum possible braking provided automatically.

Although Airbus will not say whether it is planning to develop a take-off performance monitoring system based on the ROW/ROP's capabilities, Jacob says that the system could be adapted for such a purpose. Take-off performance monitoring remains a holy grail that many have attempted to develop commercially without success, so if Airbus can provide a working system, it is likely to be universally welcomed.

HOW AIRBUS'S RUNWAY OVERRUN PREVENTION SYSTEM WORKS

Airbus's ROW/ROP runway overrun warning and prevention system uses satellite navigation to provide continual real-time knowledge of the aircraft's position, combined with a terrain database that contains detailed runway and airport layout data.

These two capabilities allow the system to have a constantly updated sense of where the aircraft is relative to a nominated runway, and whether the latter is long enough for the aircraft to land safely, given the aircraft energy state and weather parameters.

Before or during the top of descent briefing, the crew can designate the chosen runway by calling it up from the database on to the navigation display (see illustration, which relates the ROW/ROP display in real time to the actual Toulouse approach seen from the A380 performing it), placing the display cursor over the landing threshold and clicking to designate.

Airbus 
 © Airbus

When this has been done the system will generate two magenta arcs across the runway, one for the stopping point on a dry runway, another (further along) for wet. These assume a normal final approach profile crossing the threshold at 50ft (15m) at reference speed.

If the crew departs in any way from the normal speeds or profile, the stopping points will instantly be amended. Even a prolonged flare will have that effect. If, at any stage on the final approach, the system computes that the aircraft can no longer land within the runway length, an audio and display alert is generated, saying "runway too short", and one or both of the arcs will move beyond the runway end.

If the runway friction makes the difference between success and failure, the alert will say: "If wet, runway too short." In any case, the computation continues to update data throughout the landing roll, according to the braking and reverse thrust applied. If the crew decide to land despite a warning, the aircraft will provide maximum braking automatically upon touchdown.

If the crew want to use the brake-to-vacate (BTV) function, when they designate the runway they can also choose to designate the chosen exit by clicking on it too, and the aircraft speed will be reduced to 10kt (18km/h) within 50m of the chosen exit. If it is a fast-exit taxiway they can cancel the BTV. If they demand an exit too close to touchdown, the system will make that clear.

 

Advertising
Related Content
Advertising