FLUG REVUE September 2006: Falcon 7X test programme advances

September 2006

TESTING THE DASSAULT FALCON 7X

By Volker K. Thomalla

The Dassault Falcon 7X is not just the aircraft with the longest range that the French manufacturer has ever built, but it is also the most advanced business jet in the world. The three-engine Falcon 7X is the first business jet to have a fly-by-wire system under which the pilots' control inputs are no longer delivered to the control surfaces via control sticks or cables but via an electrical data link. On the Falcon 7X, the pilot does not move any control surfaces directly but enters a control pulse via the sidestick which the flight control computers convert and send to the controls as commands. Dassault is not entering virgin territory with the fly-by-wire control system, as the company already has extensive experience of this technology from military products such as the Rafale fighter aircraft. But it has never yet been implemented in a business jet.

With a wingspan of 26.21m and a length of 23.19m, the Falcon 7X is one of the biggest business jets that is currently being built. Powered by three Pratt & Whitney Canada PW307A turbofans, each of which delivers 6,400lb (28.47kN) of take-off thrust, the aircraft can fly distances of up to 5,950 nautical miles (11,019km) at a speed of Mach 0.80 non-stop. The Falcon 7X has an ultra-modern EASy-Cockpit which has been designed by Dassault in partnership with American electronics conglomerate Honeywell. Four very large colour displays present all the flight-relevant data to the pilots along with information about the status of the individual systems. Operation of the EASy cockpit is highly intuitive. To enter information in the system, as well as the usual keypads for the flight management system, the pilots also have two tracker balls which are situated in the central console between the seats. As on a PC, these can be used to retrieve menus, enter data and move a cursor.

The design of the Falcon 7X is completely digital. To this end, the company summoned its suppliers and development partners to Saint Cloud, where the new type was undergoing project definition. Some 400 designers from 27 companies and seven countries worked on the basic design of the Falcon 7X in Saint Cloud. This required 250 workstations equipped with the CATIA design software plus 220 PCs. The various industry representatives involved then designed their components back at their companies, remaining digitally connected throughout to the digital original model of the 7X, which is stored on a computer at Dassault.

In December 2003 definition of the Falcon 7X was frozen and production of the first parts commenced. In June 2004 the first fuselage was ready and was transported to the final assembly line in Bordeaux. The maiden flight of Falcon 7X took place on 5 May 2005, marking the start of the flight test programme. However accurate the engineers have been in their calculations, and whatever data wind tunnel testing generates, with a new aircraft programme it is always necessary to demonstrate whether the calculations were correct during the flight test phase before it can be certificated. Dassault expects that 1,350 flying hours will be required to meet all the necessary tests and provide all the necessary proof. Four aircraft and one mock-up for ground testing will be needed for this.

When FLUG REVUE visited Dassault's flight test centre in Istres and the production facility in Bordeaux-Mérignac at the end of June, four Falcon 7X's were flying. The first 7X had had its maiden flight on 5 May 2005, the second on 5 July 2005, the third on 20 September 2005 and the fourth on 8 June 2006.

As of the beginning of July 2006, the test fleet had completed 275 flights and over 850 flying hours. The aircraft were flown not only by the Dassault test pilots but also by pilots from the Federal Aviation Administration and European Aviation Safety Agency (EASA), the European certification agency.

On 21 July, Dassault achieved two important milestones on the path to certification of its new business jet: the static and fatigue tests. For this purpose the French testing agency CEAT had suspended a complete Falcon 7X airframe in Toulouse in a specially constructed frame and simulated 40,000 takeoffs and landings over a period of 16 months. This corresponds to twice the number of flight movements which a Falcon 7X is expected to complete over its service life and was the first time that Dassault had used a single airframe for both test series, as opposed to the normal two airframes. CEAT had gone to great lengths to damage the airframe: 64 computer-controlled actuators moved the various hydraulic systems which subjected the aircraft to rough treatment. 2,000 sensors measured the loads acting on the airframe. The results achieved what the manufacturer had been hoping for: the test air frame took everything without complaint. The wing survived being bent by up to 2.5m with the aid of hydraulic systems, without sustaining any damage. As a result, the testing agency established proof of the required strength at 150% of the maximum forces likely to be encountered during flying operations. “This is not just a major accomplishment for the programme, but it also speaks volumes about the design and structure of Falcon 7X,” said Dassault Chairman and CEO Charles Edelstenne.

Before that, from 6 to 10 April 2006, the second Falcon 7X had to prove its reliability under extreme weather conditions in the low-temperature tests. For this purpose, it was transported from Istres in the hot south of France to Iqualuit and Resolute Bay in northern Canada in search of the temperatures required. The aircraft had to cool down overnight and then start up again the next day. At first the 7X could not be started. However, this was due not to the aircraft but to the weather: it had snowed so heavily overnight that the aircraft had disappeared in a one-metre deep snowdrift. Only after the test team, armed with shovels, had removed the icy load – which was not exactly a lot of fun at temperatures of up to -33ºC – that the 7X was able to power up, which it accomplished at the very first attempt.

Another spectacular test series was carried out by the test team in Cranfield, England on 4 July. There the team wanted to demonstrate that the Falcon 7X could come to a standstill even on a flooded airstrip and that water splashes would not get into the engines even with reverse thrust in action. For this purpose the engineers set up a trough with 4cm high side panels made of rubber on the runway and filled it with two centimetres of water. Dassault chief test pilot Philippe Deleume then taxied through the water 12 times at speeds of up to 105kt, the trough being refilled after each trial. Despite aquaplaning – as confirmed by a reduction in the speed of the wheels – the aircraft remained on track and could be brought to a standstill safely. Deleume said after the test, “The performance of the PW 307A turbofans from Pratt & Whitney Canada was excellent. They did not absorb any water during the tests, even though we tested them in every possible configuration, including with maximum reverse thrust.”

However, most of the test and verification flights were carried out in France. In Istres, Dassault has a telemetry system that enables data to be transmitted from the aircraft in real time. This speeds up the process of evaluating the data considerably, as the flight test engineers can see immediately whether the data are in order or whether part of a flight will have to be repeated. Previously the data was recorded and only analysed after landing.

But the flight tests do not always produce the desired results. The Falcon 7X was no exception. Jean-Louis Cuvillier, Falcon programme manager at Dassault, said, “On the basis of some of the test data and customer requests we have decided to make some changes to the aircraft. We have extended the range from 5,700 nautical miles to 5,950, increasing the payload.” This means that the originally planned certification date will now slip. The most striking change is to the winglets, which reduce the induced resistance and hence increase the range. Another aerodynamic refinement on the Falcon 7X is the absence of the vertical stabiliser which hitherto has been installed below the horizontal tail unit. The flight trials had shown that this control surface is not necessary to control the aircraft. This means that some weight can be saved. To achieve the additional range, the Falcon 7X has been fitted with a new fuel tank on the fuselage aft of the wing which can accommodate about 800kg of kerosene. As the first 15 aircraft were already in production when the decision to make this modification was taken, these will now have to be upgraded one by one. From production aircraft 16, all aircraft will be built to the new standard from the start.

“We want to set new standards for the availability of long-range jets,” said Jean-Louis Cuvillier. Dassault is aiming for a 7X departure reliability of 99.8 percent from the first day. To put this in perspective, the departure reliability of the entire Falcon fleet is currently around 99.0 percent. On top of this, the company wants to reduce idle time taken up with maintenance and overhaul work to a level below that of the Dassault Falcon 900EX. When it comes to direct operating costs, once again Dassault is taking the 900EX as the standard: the Falcon 7X's direct operating costs should not be greater than those of its little sister.

To achieve all this, the French manufacturer has automated a lot of the work. Spare parts management, the preparation of maintenance manuals, the writing of job cards for maintenance work will all entail accessing the original data on the CATIA digital model of the 7X, resulting in much greater precision than on other aircraft types. Meanwhile the suppliers have had to undertake to meet the targets for their own areas of responsibility as well. For example, on the Falcon 7X Honeywell has increased the reliability of the Primus Epic avionics suite – on which the EASycockpit is based – by 100 percent. At the same time the company has reduced the space taken up by the avionics by 40 percent. Again, engine supplier Pratt & Whitney Canada has uprated the reliability of its engines yet again: time between overhauls (TBO) is now 7,200 flying hours on the PW307A.

To avoid problems when the new aircraft enters into service with customers, Dassault has even set up a “Tiger Team” to provide tailored support for each individual customer. During the first two weeks after delivery of the aircraft, experienced engineers will be seconded to the customer and, if the customer so wishes, a Dassault pilot will even fly along on the jump seat. Furthermore, it is standard within the industry that customers should be offered a 24/7 hotline.

40 Falcon 7X's were in various stages of production when we visited, 12 of these in final assembly in the newly built Lindbergh hall at Bordeaux airport. The manufacturer has no cause to complain about how the new aircraft has been received by customers: so far over 80 Falcon 7X's have been ordered. “We continue to receive new orders at a good rate,” said Jean-Louis Cuvillier. By the end of 2006, 20 aircraft will be in final assembly and eight should be undergoing completion in Little Rock, Arkansas. Final assembly capacity is currently sufficient for three Falcon 7X's per month. However, the company is considering whether to increase the number if required. The demonstration flights for certification by the FAA and EASA should be completed by the end of November 2006. Dassault is hoping to achieve certification at the beginning of 2007, so that the launch customer can take delivery of its new aircraft in April 2007. The first customer is no less a personage than Serge Dassault himself, who has purchased the trijet not for his company but as a private aircraft. And as he will be celebrating his 82nd birthday on 4 April 2007, it is not difficult to guess the date on which the first Falcon 7X should be handed over.

From page 44 of FLUG REVUE 9/2006

Last updated 15 August 2006

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