1992 Airbus Technology Briefing

A briefing on the preliminary report on this accident was given by Airbus and will be discussed later in this article, however it can be said at this point that once again it appears that the aircraft was not at fault.

The story of Airbus Industrie began in the mid 60s when the British, French and German Governments agreed to cooperate in the development and production of a European airliner. Against all odds it was agreed to manufacture a widebody aircraft, the A300, with the three countries each responsible for the construction of a major sub assembly which would be brought together for final assembly at Toulouse in southern France. Subsequently other European countries were involved including CASA of Spain.

The Current Product Line

The A300, which first flew in October 1972 wasan immediate success and was soon followed by the smaller A310 when the demand for a lesser seating capacity was recognised. The A300 seated between 250 and 280 passengers whereas the A310 seated around the 220 mark The A300 continued to be developed however, with the latest model being the A300-600R or extended range version. Firm sales of the A300/310 currently stand at 716.

The next aircraft to follow in the Airbus range was the A320 which is a narrow body with a seating capacity of 150. This aircraft represented a most significant advance in civil airliner design featuring FBW (fly by wire) flight controls operated by Side Stick Controllers plus EFIS (electronic flight instrumentation system). The A320 entered airline service in early 1988.

Astretched version ofthe A320, designated A321, is presently being manufactured and is expected to make its first flight in March 1993. The stretch has been achieved by inserting plugs fore and aft of the centre section to increase seating capacity to 186. The aircraft is otherwise essentially the same as the standard A320. Interestingly, final assembly of the A321 is being carried out in Finkenwerder, Hamburg by Deutsche Aerospace. To date there has been 662 firm sales of the A320 and an additional 143 for the A321.

An interesting proposal is to take a plug out of the standard A320 to produce the A319, a lesser capacity aircraft for the short haul. To date interest appears to be luke warm but Airbus lndustrie believes there is a market for up to 450 A319s. A crucial meeting has been scheduled to resolve differences between the partners as to where the final assembly of the aircraft should take place. Deutsche Aerospace wants to add the A319 to its A321 production line but Aerospatiale wants the new aircraft to be assembled at Toulouse. Once this important question is resolved, Airbus Industrie intends to actively seek launch customers for the new aircraft.

The Next Generation Aircraft

Recognising the needs of those airlines operating “long thin” routes, Airbus set about designing an aircraft capable of carrying 295 passengers in typical three class configuration over a distance of 13,250km (7,150nm). The aircraft designed to meet this specification is the four engine A340 wide body which made its maiden flight in October 1991 and which is due to enter service with Lufthansa early next year. A total of 1 15 A340s have been ordered to date by 14 operators.

A shorter version known as the A340-200, will be able to carry 262 passengers over the longer distance of 14,360km (7,750nm). Coincidentally the first A340/200 made its maiden flight on Wednesday April 1 this year duringthe technical press briefing.

Also featuring as a part of the press briefing was the opportunity to witness the “industrial roll out” of the A330 which is essentially a two engine version of the A340. The A330 has been designed for the medium to long range high density routes and will be capable of carrying up to 440 passengers. Over 150 firm orders have been placed for this aircraft so far, with its first flight scheduled for October 1992. Interestingly, the A330 test programme requires the aircraft to be certificated with three different engine options viz, Rolls Royce, General Electric and Pratt & W hitney.

A340 Development Status

Turning to the A340 in more detail, six aircraft will be involved in the flight test programme, four A340-300 and two A340-200 with a total of 2,000 flight hours scheduled. Due to the extensive systems similarities between the two models, a large number of tests performed on one model will be valid for the other. The first two A340-300s have flown as has the first A340-200. The first three aircraft have extensive test equipment installed but the subsequent aircraft will have the complete commercial installation from first flight.

At the time of the press briefing some 350 hours had been logged on over 80 flights including the “Singapore Fling” as Airbus terms it, when the first aircraft was flown non stop to Asian Aerospace in Singapore earlier this year.

The full flight envelope has been explored including speeds up to 360kts/0. 86m, and stalls in all configurations at forward and aft CofG. The aircraft has been flown at its MTOW of253. 5 tonnes andithasto date successfully handled a 20kt crosswind. Because of the unique characteristics of FBW it was possible to rapidly develop the flight control laws (refer p. 61 Dec 1991 AA fora a briefdescription ofcontrol laws in the A320) as these can be adjusted in flight through a power:Jul flight test computer. Normal, alternate and direct law have been frozen which is a remarkable achievement in the short time the aircraft has been flying. Spoiler and speedbrake kinematics have been set as have the flap and slat configurations for takeoff, the approach, and landing.

A small number of problems have been identified and corrected. Firstly there was an uncomfortable buffet from spoilers 2 and 3 in high lift configurations which was corrected by inhibiting them in normal manoeuvres. Next, aileron jerk was experienced which induced wing structural response; this was corrected by inhibiting the outboard ailerons in cruise. Buffet induced by the speed brakes was resolved by limiting them to half extension for normal use which gives a rate of descent of 4000fpm which is adequate for normal operation. Full speed brakes are available for emergency descent. A problem with the ground spoilers and the main undercarriage was resolved by setting their operation to function with the front and rear main wheels spinning. Finally a small problem with dutch roll damping of the natural aircraft was resolved by having the back up yaw damper unit active at all times.

Special attention has been paid to cockpit comfort in terms of noise, temperature regulation and the pilots’ seats because of the long haul nature of the A340. This has even extended to fitting silencers in the air conditioning ducts to the cockpits to reduce cockpit noise levels.

Experience to date indicates that there is a marked improvement in systems reliability over previous Airbus aircraft at this stage of development. The Singapore flight involved a round trip of 33 hours with just two minor faults. In the words of Airbus Industrie “overall, the A340 is already demonstrating a high level of maturity”.

A340/A330 structural testing is proceeding on schedule with many items already static tested to their ultimate load. Fatigue testing is under way for the nose forward fuselage specimen and other specimens are on schedule. No major issues have arisen to date.

The first two aircraft were weighed prior to their first flights and were found to be lighter than had been predicted; Airbus expects the final figure to be 1. 5% better than their commitment to the launch customers. Similarly with fuel, projected figures have been proved to have been conservative and it is expected that fuel volume will be at least 2,700 litres more than specification on entry into service.

Performance figures obtained so far indicate that the low speed parameters of CLmax (max lift),Vmu (minimum unstick speed), VD (lift/drag), and Vmc (minimum control speed with one engine failed) meet, or are better than target figures and hence all takeoff performance commitments will be met. Interim results indicate that landing performance will exceed commitments and lower than predicted approach speeds will be possible.

Experience to date with the CFM56-5C engines has indicated that the engine/aircraft marriage is successful with the engine giving good overall reliability. The deterioration rate has been better than the goal figure with only a 0. 5% loss of SFC. There have been no problems with vibration and no inflight shutdowns, flameouts or cancellation of a test flight due to engine problems.

During 1991, investigations were carried out into higher wave drag (Mach number effect) than the design aim and it was determined that slat 1 was responsible. Anew slat with a 10% increase in chord has been tested on the second aircraft and has shown a 1. 5% drag improvement. The new slat is now in production.

In summary, the A340 programme is running ahead of schedule, with the major flight envelope parameters already successfully explored. Airbus states with confidence that the aircraft’s payload/range commitments will be met.

Airbus Training Philosophy

Airbus has its own training organisation known as Aeroformation, which since 1973 has trained 42,000 people including flight crew, maintenance personnel, cabin attendants and other personnel.

Airbus Industrie maintains that in designing its aircraft,it has concentrated on the man/machine interface with particular emphasis on the cockpit and its associated instruments and utilisation procedures. In other words their aircraft are adapted to man.

Aeroformation’s objectives are to give Airbus customers the initial training required for the operation and maintenance of Airbus aircraft. It is specifically orientated towards standard use of certified procedures, as recommended by Airbus. In other words, Aeroformation then proceeds to adapt individuals to an aircraft type.

Training is based on an entry level corresponding to pas port category aircraft. As might be expected, the experience level varies enormously, however Aeroformation has been successful in overcoming what might seem insurmountable difficulties in terms of not only experience, but language,and very importantly, cultural differences.

Emphasis is placed on demystifying the high technology associated with FBW and EFIS aircraft and to stress that it is not necessary to be a computer expert to understand the aircraft. Extensive use is also made of computer based training both in the classroom and the various flight simulators. The latter include cockpit procedure trainers, fixed base simulators and lastly full six axis motion flight simulators.

It was interesting to learn that training has been reduced from 31 days for the A300 which included 14 days classroom, five daysprocedure trainer, eightdaysfull flightsimulator plus six hours in the aircraft; to 25 days for the A340 of which ten days will be classroom, seven days procedure trainer, seven days flight simulator and only 0. 5 to 1. 00 hour in the actual aircraft. This latter figure was queried as hardly being worth while, but Aeroformation was firm in its opinion that it was sufficient.

On the question of air safety, Aeroformation like most aviation organisations around the world has discovered the need for “cockpit resource management”, however they prefer to term it “aircrew integrated management” or AIM. This recognition has come about through analysis of aircraft accidents where it is clear that 75% are due to the human factor.

As a precursor to its training courses proper, Aeroformation takes its students through a one day AIM workshop which covers situational awareness, the error chain, communication, communication skills, barriers, synergy, synergy and crew concept, accident case study and lastly cockpit behaviour.

In conclusion it was readily apparent that in its 19 years of training, Aeroformation has successfully refined and developed its courses to meet the needs of a diverse range of students. It is now ready to meet the demand that will be generated by the introduction of the A330/340 new generation aircraft.

A320 Strasbourg Accident

On the night of January 20th 1992,an Air Inter A320 crashed whilst conducting an instrument approach into Strasbourg airport killing most of the crew and passengers. Of the 96 persons onboard, only nine survived.

The Captain, who was the pilot flying the aircraft, was 42 years old with 8,80 6 flying hours ofwhich 162 were on the A320. The copilot was 37 years old with 3,615 flying hours of which 61 were on the A320.

The aircraft had a total of 6,316 hours over 7,194 cycles and was fully serviceable at the commencement of the flight. A HUD was installed on the left hand side of the cockpit.

In accordance with French law, a preliminary report was sent to the Minister of Transport within the required 30 days. This report was strictly factual, did not contain any analysis, and did not draw any conclusions. The full investigation into the accident is expected to take one year to complete.

Following the accident, there was much media speculation that the cause was most likely confusion on the part of the First Officer in setting the flight path angle as directed by the Captain. The flight management system (FMS) has the facility for setting either a rate of descent in feet per minute or a glide slope angle in degrees. Apush button on the flight control unit (FCU) is used to either select track/flight path angle or heading/vertical speed. The selection is indicated by letters in the FCU and also appears in the upper portion of the primary flight display (PFD) but in addition, the presentation on the latter changes depending on the selection to either an aircraft symbol or flight director bar.

It was conjectured by the media that the First Officer had erroneously selected a rate of descent of 3,300fpm instead of a flight path angle of 3. 3 degrees. The rationale for this theory is that both flight path angle, and rate of descent are selected on the one control box by switching from one selection to the other. The flight path angle, or rate of descent is then adjusted by rotating a lrnob. However, in view of the change in presentation on the PFD, it is hard to image that the pilot flying the aircraft would be unaware as to which mode the FMS was in.

The brief circumstances of the accident were that the Captain had intended to carry out a runway 23 ILS approach and then to execute a circling approach to land the opposite way on runway 05 because of a 30kt downwind component on the ILS runway. The alternative to this would have been a VOR/DME approach on runway 05. The weather conditions at the time were wind 040130kt with 3/8 cloud at 1,100ft and 6/8 at 2,600ft, with a visibility of 10km. The cruise had been made at FL180 and an open/idle descent was made. This was the last Auto Flight System mode change called by either pilot.

rounding the accident both by French law and litigation. However the company was prepared to make the following statement:

• The company accepts that it is possible to make an error in selection; this is possible with any control panel and on any type of aircraft. In this case, however there were numerous methods available to each pilot for detecting the error by applying the prescribed verification and cross check procedures.

Without discussion as to which approach the Captain intended, ATC cleared the aircraft for the VOR/DME 05 approach. There were three aircraft to depart which would have seriously delayed an ILS on 23.

The Captain accepted the ATC clearance although he was unhappy with it as it meant that the approach would be rushed as the aircraft was high and fast. Strasbourg is 500ft ASL and the approach was commenced from the published entry height of5,000ftat a distance of 11nmfrom the runway threshold. The VOR/DME is located 2. 4nm short of the runway threshold. The aircraft impacted the ground on a hill called “la Bloss” which is 2,660ft high approximately 0. 5nm off centre line, at about 7nm from the DME site and 10nm from the runway threshold. The speed at impact was approximately 185kts (343kmh) and the rate of descent just under 4,000fpm. Sadly the aircraft was not fitted with a ground proximity warning system ( GPWS) although full provision is basic to the aircraft. The option was not taken up as this equipment is not required by French regulations. The aircraft was equipped with an emergency locator transmitter (ELT) which did not operate and was found completely destroyed by the impact.

Unfortunately the digital flight data recorder (DFDR) was severely damaged by •fire and the tape melted. Information however was available on an unprotected flight data recorder (QAR) up until the last 20 seconds offlight. The cockpit voice recorder (CVR) was damaged but its tape could be read.

As outlined at the beginning, no analysis as to the likely cause of the accident is yet available. However, because of the media conjecture, three recommendations were made to the Minister in the preliminary report. These were firstly that all operators of A320 aircraft be advised of the possible risk of confusion between the “vertical speed” and “flight path angle” modes. In conjunction with this that modifications to the ergonomics of the aircrafUcrew interface be studied with the view to reducing the risk of error inselection. Secondly that the French regulations be amended as soon as possible to make the installation of a GPWS mandatory on transport aircraft under the same technical conditions as those specified by the Chicago Convention. Finally it was recommended that the regulatory conditions for the approval and the installation of ELTs on board aircraft be·reviewed in order to ensure a higher probability of good operation after an accident.

Following the preliminary report, the investigation committee will be considering the following matters:

• the possibility of setting 3,300 vertical speed instead of the possibility of a deliberate setting of a high rate of descent due to visual aberration,confusion between the distances to the VOR/DME and the runway threshold, or that there may have been a feeling that the descent was late with respect to the procedure,

• the possibility of erroneous distance information, ie, DME error, map display error, or false flight management system (FMS) position.

• undetected autopilot failure (pitch down hard over). In making its presentation on the accident, Airbus Industrie was obviously constrained by the legal circumstances surrounding the accident both by French lawand litigation. However the company was prepared to make the following statement:

• The company accepts that it is possible to make an error in selection; this is possible with any control panel and on any type of aircraft. In this case, however there were numerous methods available to each pilot for detecting the error by apply Undetected autopilot failure is extremely unlikely. Furthermore, for such a remote failure to occur and remain undetected by the crew is even more improbable.

• the list of assumptions may not yet be complete. For instance a rapid descent may have been initiated intentionally, directly towards the minimum decision height (MDH).

As mentioned earlier, it is likely to be at least a year before the full accident investigation is completed. Whilst it would be possible to draw a conclusion as to the likely cause, it would presumptuous to do so in view of the ongoing investigation. However there is concern in the world aviation community that automated glass cockpit aircraft do present unique problems in cockpit workload in busy terminal areas, particularly if there is a requirement to reprogramme an approach to meet ATC requirements. It is possible for an inexperienced First Officer to end up head down punching buttons at the very time that he shouldbe monitoring the approach as a part of the CRM team. Clearly training should be structured to take this new aspect ofaviation into account.

Notwithstanding the above, from the initial investigation the A320 appears not to be at fault, however it would not be surprising if the final report picks up the need for thorough system awareness, particularly under high work load, stressful ATC situations

Airbus A350

FinallY, very briefly touched on at the press briefing was the A350 mass transporter or ultra high capacity aircraft (UHCA). The concept is for an aircraft capable of carrying up to 1000 people over the present long distance routes to cope with the growing airport and airspace congestion in many parts of the world. However, some airports are already at their limit with the Boeing 747-400 (64. 31m wingspan) in terms of terminal parking. There is also the problem of runways and taxyways. Contingency plans are inhand at the more modern airports to cope with a 85m wing span but even this means that folding wings are being looked at by some manufacturers.

Airbus Industrie is being innovative in its approach and is looking at the possibility of a flying wing with a double deck, although the final design ofsuch an aircraft is wide open at the present time.

Finally,it is interesting to note that a larger size aircraft will reduce manufacturing costsand that Airbus has seta target of 15% better direct operating costs than that of the present 747. It is also seeking to contract out a 20-35% workshare outside the consortium, with Mitsubishi, Kawasaki and Fuju which are Japanese heavy industry companies.

Conclusions

During our visit it was announced that the conflict which had arisen between the American aircraft industry and Airbus Industrie over government subsidies to the latter had been resolved. This perhaps more than anything marks the coming of age of Airbus Industrie which is now recognised as a mature manufacturer of aircraft. Anyone visiting Toulouse for the first time and seeing the massive assembly hangar plus dozens of Airbus aircraft awaiting test would have absolutely no doubt as to the truth of the above statement.