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Tue, Jan 04, 2005

Innovative German Twin Begins Taxi Tests

From The Birthplace Of The Space Age, A Space-Age Airplane

By ANN Senior Correspondent Kevin "Hognose" O'Brien

The importance of the island of Usedom to aerospace depends on your frame of reference. To an aerospace historian, it's where guided ballistic and cruise missiles got their start, at the German Army and Air Force test centers on the island's tip at Peenemunde. For an 80-year-old RAF Bomber Command vet, it's a memory of a tough, well-protected target. For a Cold War vet, it might have been a home base or a target folder (depending on what side you were on). For modern Germans, it's a nice place for a summer vacation on the Baltic Sea. But for us, today, it's the birthplace of a GA twin like none you've ever seen, the TT62 Alekto by High Performance Aircraft (HPA). The prototype, D-IXTT, has not yet flown, but began taxi testing on December 29th. Only some full-system vibration testing remains before the German Civil Aviation Authority clears the new twin for flight tests.

At first glance, the Alekto looks like any composite twinjet. It has straight wings, a swept T-tail, seating for five. Except that where the jet engines should be, the Alekto has two propellers. Not propeller engines... just two smallish five-bladed propellers, made by Germany's own MT-propeller. Where did they hide the motors?!? The propellers are driven by two 4.0 liter Centurion diesel V8s that are buried in the rear fuselage, behind the cabin (roughly where the engines were in the tractor-propelled Bell P-39). The pylons that the propellers are mounted on also contain the radiators for the liquid-cooled engines.

The aircraft is priced very aggressively at around a half million Euros, and HP Aircraft claims to have sold sixty of the machines already. Their "how to buy" web page is being overhauled, which may portend a price hike.

The structure is composite, nothing new to Europeans, who've been building composite gliders for fifty years. The cabin is pressurized to a differential of about 5 PSI, with seats for five people, and unusually large windows for a pressurized plane -- to take advantage of the cabin's excellent position for visibility.

Along with the new airframe, the design has new engines, and an entirely new conceptual design and powerplant layout, and, as you might expect, a cutting-edge cockpit, with sidesticks for control and three displays: primary flight display, multi function display, and engine control display. The MFD displays radar, navigation including approach charts, and collision-avoidance data. The TDI engines dispense with mixture and carb heat; a single power lever controls each engine. (The prototype is at present fitted with an interim panel, including a six-pack of normal flight instruments, and the standard Thielert engine management gages).

The December start of taxi testing is an important milestone in the HP Aircraft program, which aims at civil certification for the Alekto. The individual systems of the aircraft have been tested and overtested, because the managers of the firm are determined to do flight and certification testing right the first time, and not have to do it over. The company works closely with the German certification authorities at each step along the way. If certification can be completed by January 2006, it will be done to JAR 23 Amendment 1 (a later completion may require certification to subsequent Amendments of JAR 23). Because JAR 23 and FAR 23 standards are close, reciprocal certification should be simply a matter of paperwork at that point.

At this early stage of development, all flight performance data are calculated or estimated. But these data do reveal the intended strength of this airplane vis-a-vis its competition. Thanks to the frugal turbodiesels, and the slick aerodynamics, the machine should be a range king. The developers expect about 50 nautical miles per gallon, and a 1,700 nm range with IFR reserves, at speeds of over 200kt.

It hasn't been an easy ride for the German company. In August, 2003, company founder Heiko Teegen (HIGH-ko TAY-gen, with a hard G) collapsed next to his parked motorcycle, and couldn't be revived. While Teegen was best known to German-speaking pilots as the longtime publisher of the general-aviation magazine Pilot und Flugzeug, he was involved in many other aviation activities, from lobbying for sensible regulations (always a problem in Old Europe) to heading up HPA. It is a measure of his skill in selecting subordinates that most of his projects, including HPA, continue. HPA renamed their R&D hangar in his honor.

While the engines seem radical to American eyes, and they are new, they have already achieved certification in Europe and are expected to be certified soon in the USA. The Centurion 4.0 V8 is the big brother of the 4-cylinder Centurion 1.7 that is available in Diamond Aircraft's twin-engine DA42 and, in Europe, in the single-engine DA40. These 310 HP engines run on Jet A and have dual-redundant FADEC, making them economical and simple to operate. In November, 2004, engineers from HPA and Thielert gave Alekto's powerplant, to include its propellers and driveline, a 50-hour test, which is part of the certification requirements. The only anomalous result was that temperatures in the main reduction gearboxes did not go as high as originally expected. The sound of the engine and propeller combination is unique, like a cross between a large turbofan at idle and a powerful sports car. (You can hear it for yourself in the movies on the HP Aviation website).

Some people will worry about having the engine behind you in the event of a crash. P-39 pilots used to worry about that. (At least the Alekto doesn't have a driveshaft running between the pilot's legs). The designers of Alekto have taken great care to ensure that the engines will stay put; they are held back by a titanium structure that is designed & tested to 26G, and that also serves to isolate the engine compartment in case of fire.

What about that name, Alekto? Pull out a copy of Bulfinch's Mythology and all will be revealed. Alekto (often transliterated Alecto in English) was one of the three Furies of Greco-Roman myth, her name means "the relentless one" or "unceasing, untiring" one. The Furies, of course, had wings, rather like the Christian depiction of angels.

Introducing any new aircraft is difficult, as anyone who has tried can tell you (whether he succeeded or failed). The more radical a design, it seems, the harder it is for it to win acceptance. So HP Aircraft has quite a challenge ahead. They have an interesting, attractive design, and promise good numbers.


FMI: www.hp-aircraft.de

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