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The era of the ‘PLJ’ is here... in the shape of the D-JET Ever since the jet engine was invented- generations of general aviation pilots have yearned for a safe- affordable jet aircraft that could move them- and their families- at a higher speed- and in much greater comfort than a single-engined propeller driven aircraft. The main problem has been finding a light enough- and fuel efficient enough- jet engine to fit into a relatively small airframe. Today- however- the new ...

Mike Vines   |   1st July 2006
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The era of the ‘PLJ’ is here... in the shape of the D-JET

Ever since the jet engine was invented- generations of general aviation pilots have yearned for a safe- affordable jet aircraft that could move them- and their families- at a higher speed- and in much greater comfort than a single-engined propeller driven aircraft. The main problem has been finding a light enough- and fuel efficient enough- jet engine to fit into a relatively small airframe. Today- however- the new generation of small turbofan engines are light enough for just two fit people to lift.

As you know- the term ‘VLJ’ (Very Light Jet) is a recent one with the likes of the twin-engined Eclipse 500- Cessna’s Mustang and Embraer’s Phenom 100. But now their single-engined 4/5 place counterparts have been dubbed PLJs or Personal Light Jets.

Diamond Aircraft Industries GmbH of Austria with its D-JET says ‘PLJ’ is probably the acronym that will stick- as it does sit much better than the ‘mini-jet’ or ‘micro-jet’ titles that have gone before.

'Current pilot-owners want to move into the jet-age and we see the D-JET as the right aircraft at the right time-' said Peter Maurer- Diamond Aircraft Industries’ North American president. 'Many factors have coincided to make this dream come true: Reliable lightweight composite structures and light; low-burn- new-tech turbofan engines with FADEC; have combined with the latest developments in avionics.'

The D-JET will have five seats- two pilot positions and a three-seat luxury cabin. The Garmin G1000 is at the heart of the digital cockpit and will have an optional three-panel system with two 12-inch primary flight displays (PFDs)- a centrally located 15-inch multi-function display (MFD)- FMS controller- glareshield mounted Autopilot Controller- and dual AHRS/GPS/ Magnetometer sensor system. The Williams FJ33-4 engine will be flat-rated at 1-400 pounds at 72 degrees F and incorporates dual-channel FADEC. Certification is currently planned for early 2008- followed soon after by first deliveries.

Diamond says that the largely composite D-JET will be certificated at 5-070 pounds MTOW; carry five people up to 25-000 feet; have a cabin altitude of 8-000 feet; and cruise at speeds of 315 kts. The company also claimed originally that the D-JET would be capable of operating from 2-000 ft runways (but this is still to be confirmed) and reach its cruise altitude (25-000 feet) in just eight minutes. Fuel consumption is expected to be around 34 gallons per hour.

'In a nutshell- the D-JET is the Beech Bonanza of the 21st Century-' explained Maurer. 'It is aimed at- say- Lancair Columbia- Cirrus SR22- Beech Bonanza- and Diamond DA42 pilot owners- who want to step into the jet age. It is a high performance- new technology- simple to operate aircraft which can be safely flown by the typical private pilot.'

The prototype D-JET (SN 001 C-GVLJ) flew for the first time on 18th April from Diamond’s North American base at London International Airport- Ontario. After a series of high-speed taxi and rotation tests the aircraft was flown for one hour- six minutes- and according to the flight test plan was evaluated through 19 distinct test points.

After take-off and climb to 12-000 ft- stability and control with flaps and landing gear extended and retracted and was successfully tested. As Diamond’s CEO Christian Dries said at the recent Berlin Airshow- when asked about the risks involved with retracting the undercarriage on the first flight- 'no risk – no fun'.

The test speeds ranged from slow flight at 1.1 Vs to 160 kias. Engine and systems operational tests were successfully performed and followed by roll rate and lateral directional stability tests- and simulated landing at altitude. Dries flew the Diamond Twin Star chase-plane in close formation on this flight and monitored the recycling of the undercarriage as well as supplying the platform for air-to-air ‘stills’ and video photography. The D-JET performed a ‘normal’ landing with a 5kts crosswind component.

'We were absolutely delighted with the flight'- reflected Dries. 'It went exactly to plan. What more could you ask for? Our crew did a fabulous job and we are very grateful for the support received from Williams- Garmin- Parker- Argotech and our other partners.'

After that flight the aircraft logged a total of 11 hours flight test time in just 10 days. It then went back into the hangar for planned modifications that could not be completed in time before first flight. Maurer explains- 'We had intended to do some modification work to the engine inlet fairing before first flight but this would have delayed it. The other main reason was that the aircraft initially flew with limited flight test equipment- again because we needed to fly the aircraft.

'During the down-time- real-time telemetry download instrumentation has been fitted in the aircraft.' Pi Research (which is part of Cosworth Engineering) supplied the telemetry equipment- which was developed from real-time Formula One racing car telemetry and sensor know-how. 'This equipment will allow us to speed up the test flying program as our ground engineers can follow real-time information coming from the flight test aircraft.'

Maurer points out that the engine inlet size has been reduced from that shown on the original artist’s impression dating from 2003 to better suit the FJ33 engine. The inlet is now positioned just a few inches forward of the wing leading edge to allow the cabin door to be opened on the left hand side of the aircraft without restriction.

The company is due to hold an official roll-out launch party for 500 guests on July 15th at its Canadian base- where a full size mock-up of the aircraft will be available for inspection for the first time. It is expected that Diamond will release additional program details at that time.

The prototype aircraft will be flown at the roll-out and then a week later will be flown to the EAA AirVenture Oshkosh event- where it will also be demonstrated in the air.

Diamond currently holds ‘more than 200 D-JET orders’ and expects to announce many more after these two major events.

'We expect that the D-JET will be produced in North America-' says Maurer- 'because most of our vendors are based here (Williams are only 90 minutes down the road) and the largest single sales market- estimated at around 60%-70% of world market- is here as well. Our competitors are also based in North America and we will be buying and selling in U.S. Dollars as they do.

'The main production location may well be at London- Ontario- as there is a possibility that funding assistance from local- municipal and federal aid incentives will lessen the cost of finishing the development- certification and putting the aircraft into production-' Maurer added. Some production may occur in Austria or elsewhere but plans are flexible at the moment- he explained.

There won’t be a single solution for D-JET pilot training according to Maurer.

'Insurance companies will probably dictate the final outcome and we certainly want to protect our own exceptional safety record which is probably the best in the GA industry over the last twelve years. We’re very conscious of the need for a proper training program.

'We have our own simulation company; Diamond Simulation Industries- and we will have several D-JET Flight Training Devices online before the first production aircraft is delivered. From the outset we have designed our aircraft so that there are less emergency procedures on the checklist than for a typical VLJ. They have far more because of the high altitudes that they are typically flying. Remember the D-JET ceiling is 25-000 ft- not 41-000 ft.

'There will be a world of difference between qualifying a pilot with 500 hours IFR on a Cirrus SR22 for the D-JET- than say a Cessna Mustang. There is no reason why a D-JET should be significantly more difficult to fly than an SR22 or a Bonanza for example. In fact it should be simpler because of the D-JET’s power management single lever FADEC throttle. Situational awareness in the D-JET’s avionics and the sophistication of the autopilot is fantastic and will definitely lighten pilot work-load-' explained Maurer.

In the past Diamond has said that an emergency descent parachute would be fitted to the D-JET as the last resort final solution in an emergency. Diamond says that it is in discussion with BRS (Ballistic Recovery Systems- Inc.) and other companies- but currently there isn’t a parachute system on the market that could handle the performance envelope and weight of the D-JET. The aircraft is being designed to take such a system- but Diamond’s intent is to design and certify the aircraft without relying on an emergency parachute system.

'We definitely intend to offer such a system and it could coincide with certification and possibly be offered as a delete option. The weight penalty would be over 100 pounds and some pilots might instead prefer an extra 100 lbs of fuel on board-' explained Maurer.

Diamond’s CEO Christian Dries said recently that it was a dream of his that once the technology existed he would prefer an emergency cockpit auto-land button to be fitted instead of a recovery chute system- in dire cases of pilot incapacity.

Maurer said of the D-JET’s underlying philosophy: 'We have designed an aircraft that suits the pilot owner. We don’t expect D-JET pilots to fly very long distances regularly. We don’t consider the need to fly at very high flight levels as critical to our customers as ease of operation- safety and cabin comfort. The aircraft will be operating at lower Mach numbers- which allowed us to optimize the airflow for excellent low speed handling- low stall speed and low approach speeds.

'We have a very docile and comfortable aircraft that is quiet- and has a reliable jet engine. It will also have exceptional cabin comfort- which is important to the owner-pilot.

'If you look at a typical flight profile it splits into climb- cruise and descent portions. Airliners are optimized for the cruise portion- which is the longest portion of the entire flight. When you look at shorter distances that VLJ’s and PLJ’s will typically fly- the cruise portion is a proportionately shorter part of the flight profile- so it makes sense to strike a balance rather than optimize for high-altitude cruise at the expense for lower altitude performance.

'We feel that because most of the VLJs will try to operate in the upper airspace at their optimum altitude of say 41-000 ft- their ATC clearances will be regularly delayed because of the number of aircraft trying for the same altitude. So for at least part of their flight they are going to have to fly at lower altitudes- which- for them- is inefficient.'

The D-JET is also potentially safer than VLJs- Maurer claims. He compares the hazards of a cabin pressurization failure in a D-JET versus VLJ. At 25-000 ft it’s not a crisis in a D-JET but it is potentially a bigger problem if it occurs at 41-000 ft.

For European single pilot/owner certification Maurer doesn’t see any problems operating a D-JET in European skies. It will be just the same as for private owners flying their PC-12- TBM 850 or Cessna Caravans over Europe.

It would of course be a problem for commercial operations as commercial Single Engine IFR restrictions are still in place over most of Europe despite a 15-year running battle to get the rules changed.

More information from www.diamondaircraft.com

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