Fly-by-wire for airliners carefully dobs it

Vocabulary: emergence, application, stage, to reach, requirement, mechanical reversion, to investigate, distribution, to prevent, flutter, aft.

Exercises:

I. Read the text and answer the questions:

1. Is the time interval between the emergence of a new technique and its operational application long or short?

2. What does the load reduction lead to?

3. How is the load distribution investigated?

4. How may the increased flight range be achieved?

5. How is the drag reduced?

6. What does the CG shift lead to?

7. Will A31O-300 be equipped with a gross weight and center of gravity calculator?

2. Read the text paragraph-by-paragraph and enumerate each paragraph

3. Determine the theme of each paragraph.Определите ведущую тему каждого абзаца.

3. Write down the theme of each paragraph to get the logical plan of the text.

4. Think about the plan and combine it in a logical order.

5. Make a summary.

3. Entitle the text.

The new technologies developed during recent years have opened up new vistas¹ for the airframe designer. But the time interval between the emergence of a new technique and its operational application remains very long. In the military field, both the designers and the operators try to reduce the interval to the minimum, but in the civil airliner business a variety of external factore delay the introduction of new developments.

The Airbus Industrie plans to approach the full application of the new techniques by stages. The first stage will consist of fitting the long-range version of the А310, the A31O-300, with a fuel trim tank in the tailplane so that it is able to fly with a reduced static stability margin². The second stage will be reached with the 150-passenger A320, which will be fitted with electronic flight control in roll and pitch only.

Several airlines have already stated requirements for airliners with electronic flight controls without mechanical reversion. Some operators have even requested the kind of full electronic control which will make it possible to limit flight loads on the wing and therefore to lighten³ the structure.

A wind-tunnel test program, investigated the aerodynamic pressure distribution over a wing on which the spoilers and trailing edge control surfaces were being operated according to various patterns of fly-by-wire control. ONERA made use of a large-scale half model for these trials. But this fundamental research is in its very early stages end Airbus Industrie has no intention yet of applying such advanced control techniques in all three axes; or of using them to control structural stresses in the wing; or of preventing flutter; or for such new techniques as variation of wing camber.

Five “intelligent” tons. The reliability of modern engines makes it possible to operate twin-engined airliners on the majority of airline routes, provided the aircraft have the necessary range capability.

In order to increase the range capability of the А310, it had to be fitted with additional tank age. The placing of the additional fuel tank in the tailplane presented an elegant solution for carrying five additional tonnes of fuel while, at the same time, reducing the drag of the aircraft and thereby⁴ improving its efficiency. The principle is quite simple. The tailplane tank is connected to the main wing fuel tanks in such a way that, by using appropriate⁵ pumps, a certain amount of fuel can be transferred aft to modify the centre of gravity of the aircraft. The resulting rearward movement of the CG eliminates some of the necessary downward trimming load on the tailplane in cruising flight. This reduces drag and also reduces the loads on the mainplane. The gains which can be achieved by moving the CG rearwards, as well as the handling improvement achieved with slightly relaxed stability, have been demonstrated in the third A300, the company development prototype. Trials have been flown with the centre of gravity at 44 per cent of the aerodynamic mean chord of the wing, compared with a normally permitted maximum aft CG of 35 per cent. Equivalent trials have yet to be flown with the A310, but no surprises are expected because of the basic similarity between the two types of aircraft.

Moving the centre of gravity of the А310-300 rearwards by some eight to ten per cent should result in a reduction of some two per cent in overall drag, plus an improvement in the buffer margin. During normal operations, when the rearward limit of the centre of gravity is 35 per cent MAC in the A300 and 35.5 per cent in the A310, the airlines are using a conservative stability margin of between seven and eight per cent. The ability to shift the CG in flight will certainly make it possible to cruise with the centre of gravity beyond these limits. Thus, although the А310-300 will probably not be certificated to fly with a centre of gravity further aft than 40%, the real gain in flight should be of the order of eight to ten per cent (because the airlines currently do not operate at anywhere near the certificated limit).

Certification of the tailplane fuel trim tank in the A310-300 will require Airbus to snow that the aircraft can still be flown safely in all conditions at the aft CG, if the transfer pumping system should fail. It is this which limits the ultimate aft CG shift.

The basic A310-300 will not be equipped with a gross weight and centre of gravity calculator. According to Airbus Industrie, these devices are expensive and not altogether satisfactory. They are, at present, mainly an additional aid for the operator.

The manufacturer is looking for a system which is tailored⁶ to the basic certification standard of the aircraft.

The presence of the tailplane trim tank will only have a marginal effect on the electronic flight controls. Because the control surface movement for a given G loading increment is smaller, the system gains are changed, but the hardware remains unaltered⁷.

4100 знаков

Notes:

1. vista – перспектива

2. margin – граница, предел

3. to lighten – облегчать

4. thereby – тем самым

5. appropriate –соответствующий

6. to tailor – to attach

7. unaltered – unchanged

UNIT 19