Electric aircraft, 600kg LSAs and the return of Horten tailless designs. CHRIS WRIGHT from the RAeS General Aviation Specialist Group gives an overview of some of the most exciting highlights and innovation from this years AERO Friedrichshafen GA exhibition, held on 1-4 April.
The ‘Global Show for General Aviation’ has run for 27 years at Friedrichshafen in southern Germany. Friedrichshafen aeronautical history extends to aviation’s beginnings with literal giants of Zeppelin and Dornier, and continuing today with the Airbus, MTU, ZF and – Zeppelin. Lake Bodensee, its surrounding countryside, beautiful old towns, and excellent Zeppelin and Dornier museums, demand a longer stay; this was my first visit to AERO.
First impressions were of the sheer size of AERO: 12 large hangar-size halls full of GA aircraft and related exhibitions. Over 700 international exhibitors and over 300 aircraft were present, from trikes to helicopters and business jets. A paradise for well-heeled GA flyers – and many onlookers. AERO describes itself as the ‘trade show of Innovation’. “For innovation go to AERO, for more old timers – go to Oshkosh” was suggested to me – not entirely correct I’m sure.
After my first circuit, follow-on impressions were of the quantity of two seat aircraft in the 600kgs LSA market, some interesting and surprising historic and ‘retro’ aircraft, an attractive variety of Gyroplanes, many colourful avionics and simulator displays, a large display of elegant sailplanes and interesting AkaFlieg developments, and surprisingly, fewer electric powered development aircraft than I had anticipated. I was hoping to see more visibility of e-VTOL and Urban Air Mobility vehicle development. Fellow attendees had seen more in previous years.
Following is a selection of aircraft and powerplants attracting my attention, however I could not possibly do justice to many aircraft and exhibits that might appeal to others.
Vintage delights
The first metal commercial aircraft – the 1919 Junkers W13 (via author)
A highlight for me was a replica of the first all metal commercial aircraft from 100 years ago, the 1919 Junkers F13 - yours for Eu2.5m.
Nearby was a 1930’s WACO WMF-5 Biplane 3 seater being reintroduced as a new build, and immaculately presented.
1930’s WACO WMF-5 Biplane 3 seater (via author)
Other reintroduced aircraft included the aerobatic CAP10 and a full scale Stampe biplane by Ultralight Concept, redesigned within the LSA limit with a modern powerplant.
Ultralight Concepts full scale LSA Stampe biplane (Via author)
Horten returns
Two seater Horten Aircraft HX2 flying wing prototype. (via author)
Another ‘updated’ design was the elegant two-seater Horten Aircraft HX2 flying wing flying prototype with retracting undercarriage. The prototype had flown for just a few hours before being flown to the exhibition.
ScaleWings 70% Mustang (via author)
Further very impressive ‘yesteryear’ aircraft were the 70% scale Mustang (sw51) by ScaleWings, displayed previously, and a private build 76% scale FW190.
Remarkably the sw51 was detailed with every panel and to the last visible rivet (of nearly 100,000 rivets) and is made from composite mouldings. The aircraft can be powered benignly with a 100hp Rotax 912 to meet the 600kg limit, up to a 600hp turbocharged Chevrolet LS300 with MTOWs of up to 1200kgs. Maximum Vne with the high-power version is 323kts. The +6g and -4g loading applies to all variants.
Norwegian Aerosport’s 5.4L V12 (via author)
Displayed separately in another hall was the also impressive Norwegian Aerosport Engineering ASE-650 SAGA 5.4 litre V12 engine of, presumably, 650hp. Designed for scaled Mustang and Spitfire type of aircraft, this engine looks ripe for sw51: no doubt the sound and aircraft performance would make heads turn.
76% scale FW 190 – a builder’s dream! (via author)
The FW190 is a very realistic realisation of a 30-year dream by its builder – powered by a nine cylinder 360hp radial engine.
Ultralight JH Aviation Corsair – 120kg empty weight (via author)
Finally in this field of oldtimers are the Ultralight JH Aviation Corsair – with a fixed undercarriage and an empty weight within the German UL 120kgs empty weight limit, and a Piper SuperCub update with wheels sized to please farmers - and STOL enthusiasts. The Supercub is again aimed at the 600kgs LSA market.
SuperCub with super STOL wheels. (AERO Freidrichshafen)
LSAs on display
Aero & Tech Nexth (via author)
Amongst the many more LSA aircraft displayed, several caught my attention due to quirky impressions as well as some remarkable ultra-smooth composite structure, retracting undercarriage aircraft.
The Black Aero & Tech Nexth aircraft comes in both ULM/Microlight and LSA form of 472.5 and 600kgs respectively. Its angular slab-sided all-metal structure seems reminiscent of the F117A stealth aircraft: with dark colouring and strongly tinted windows it appears somewhat Sci-Fi – flown by Darth Vader.
B&F Technik FK LeMans open cockpit experience (via author)
Two other interesting LSA aircraft are the B&F Technik FK LeMans with side by side open air cockpits with individual windscreens, and the all carbon Italian Innovaviation FX1 with its high mounted Rotax 912 power unit and roomy cockpit.
Innovaviation claims the widest cockpit. (via author)
More conventionally the Shark Aero Shark and the Swedish Blackwing BW635RG and many similar aircraft have very slick shapes and high performance on 100hp; still within the 600kgs LSA requirement.
The French Elixir broke new ground in production processes, with most (carbon fibre) parts made with a one-shot process. For example the entire wing (including several spars) is created in one moulding process, with eight parts comprising the full airframe.
Seaplanes make a splash
For those who wish to operate off water AERO Exhibition LSA examples included: The Rotax 582 powered two seater Catalina by FLY Synthesis, the Flywhale Adventure IS, and the Dynali H3 Easyflyer helicopter with floats and also Rotax-powered.
FLY Synthesis two seater Catalina (via author)
Flywhale Adventure IS seaplane (via author)
Dynali H3 Easyflyer helicopter with floats (via author)
Electric flight:
During most days there were symposia on all aspects of GA. During the second day, on the topic of electric flight, Siemens, who are heavily engaged with electric power and control systems development - predicted that pure electric flight is unlikely to be readily available across GA for distance flying for possibly three decades. This reflects the present and anticipated state-of-the-art of batteries. GA rides on the back of massive development effort by automobile manufacturers: the energy density slowly rising whilst the price is falling more rapidly. Near-term hybrid systems will provide range capability; these are still in the state of active development. Hybrid systems use internal combustion engines, gas turbines or fuel cells in combination with electric motors driving propellers. Fuel cells provide direct electrical power to supplement batteries and have flown however no fuel cell systems were seen ‘in the flesh’ nor were indications of the degree of progress displayed. Internal Combustion engines or gas turbines in some cases drive a propeller in series with an electric motor, or alternatively drive a generator system to drive propellers via one or more electric motors and also to charge batteries.
Electric flight is entirely practical for niche markets: especially for self-launching flight, racing and aerobatic flight and relatively short duration training flights. Electric -owered sailplane derivatives are however beginning to push duration beyond two hours for practical cross country flying.
SD70D 70kW motor for small two seat aircraft (via author)
Siemens had a large stand illustrating both pure electric driven flight and hybrid systems. Three brushless motors were displayed with illustrations of their applications in the background. The smallest displayed was the SD70D 70kW motor for small two seat aircraft.
The SD260D 260 kW motor (via author)
The SD260D 260 kW motor was illustrated mounted as pushers on the wingtips and tail of a small 6-10 seat commuter aircraft.
SD200D motors provide the power for the CityAirbus eVTOL. (via author)
Eight SD200D motors drive 4 sets of co-axial propellers on the CityAirBus e-VTOL project in collaboration with Airbus. The motors are tailored to low rpm, high torque output, keeping noise levels as low as possible.
Multi-engine hybrid systems were illustrated on the Siemens stand. One illustration showed two electric motor driven propellers on outrigger pods, deriving power from a single 115kW diesel engine generator mounted within the fuselage. Greater efficiency is claimed due to the propellers being outboard of fuselage interference.
The APUS i6 multi engine research aircraft (via author)
Another illustration showed a multi engine research aircraft - the APUS i6, as a hybrid using fuel cells driving 7 motors. The APUS i6 is also a technology demonstration platform for testing and certificating a variety of hybrid powerplants and distributed power systems including fuel cells, gas turbines and diesel engines, for conventional flight as well as for eVTOL vehicles.
New eVTOLs
Autoflight eVTOL was unveiled at AERO 2019. (AERO Freidrichshafen)
Unveiled on the first day at AERO was the Autoflight e-VTOL aircraft, in configuration somewhat like a Long-EZ with two outrigger booms. The booms carry 3 electric motors each side for vertical flight and a similar sized motor located at the rear of the cabin drives a pusher propeller. The motor power was not disclosed but is guesstimated at approximately 70kw judging by size. The lift propellers park in a fore/aft minimum drag position during forward flight. Flight testing is imminent.
The Jetcopter.EU concept: a five-seat EVTOL with four articulated jets. (via author)
Another new project unveiled at AERO was the Jetcopter.EU concept. This is a 5 seat EVTOL claiming 300 kph maximum speed, using two 375kW motors. These power a pair of fans on the roof of the vehicle, which exhaust through four articulating jets rather in the fashion of the Harrier aircraft lift system.
Alpi Aviation hybrid Rotax and electric drive (via author)
Further examples of hybrid power systems were scattered across AERO. Alpi Aviation displayed a powerplant for a twin engine aircraft. A Rotax engine in series with an electric motor which can draw on batteries to add to the Rotax power. The electric motor /generator can replenish the batteries during cruise. Two further hybrid systems were on display: – a Wankel engine coupled to an electric motor on the Compro stand, which included some smaller direct electric drive systems, and a turbine driven generator system. Compro provide complete electrical systems combining Rotex Electric motors battery management systems and speed controllers.
Compro hybrid Wankel engine coupled to an electric motor (via author)
French start-up Turbotech were showing a 40kg turbo generator with an embedded heat exchanger to recover heat from the exhaust, aimed at light aircraft and large UAVs. The system is capable of running on diesel, biofuel, natural gas or hydrogen. A fuel burn of 12-18 L/hr is claimed for a 90kw turboprop version.
Turbotech 40kg turbo generator (via author)
Geiger Electric motors featured on many aircraft including trikes and a hanglider pod. The Icarus C42 is fitted with a 32 or 50kw Geiger Electric motor and 6 Li-Ion packs weighing 15kg each. A 250cc 4 stroke engine fitted behind the cockpit is a range extender. The other picture shows a Geiger motor powered hanglider pod.
Icarus C42 with Geiger Electric motor, 6 Li-Ion packs (via author)
Icarus 250cc 4 stroke engine range extender (via author)
Geiger motor powered A.I.R hanglider pod (via author)
Sailplane and trike aircraft were the most common pure electrically driven aircraft at AERO.
Retractable electric drive and propeller (via author)
Nose mounted electric motors generally had blades that folded cleanly along the sides of the nose, although two sailplanes had retracting propeller systems: the photo shows a clamshell door system which opened to allow the propeller and motor system to slide forward to operate.
Retractable Electric Pylon on Schleicher 32EI (via author)
Retractable pylons were also common, a 25kW brushless motor is shown on the Schleicher ASW 32EI.
GFW-4 tailboom mounted drive (via author)
The GFW-4 had its fold-out propeller rotating around the tail boom half way towards the fin.
Pipistrel Alpha Electro trainer (via author)
Pipistrel have developed a number of electric powered aircraft - shown is the Alpha Electro trainer. Pipistrel claim a 70% reduction in running costs compared with a conventional trainer. During descent up to 10% of energy is recuperated. In the e-flight hall Pipistrel displayed the further battery storage area behind the cockpit: up to one hour training flight can be achieved with sufficient reserve; recharging is typically 90 minutes. Pipistrel has charging units for installation at airfields around the country.
Summary
AERO 2019 also saw bizjets on display. (AERO Freidrichshafen)
Much at AERO 2019 not been covered in this article: a considerable array of avionics and flight simulators seen would take another article to cover, as also light business aircraft, gyrocopters and helicopters.
The relatively new 600kgs LSA class is a key driver for GA innovation. LSA aircraft are now sufficiently sized for training with load capacity for the instructor, student and fuel. Exciting high performance aircraft with vp propellors and retractable undercarriage, are practical within 600kgs. Certification is easier, enabling faster development of new technology including electric flight and even e-VTOL; manufacturers can trial and optimise concepts at small scale.
So many alternative approaches and technologies exist for e-VTOL development: electric and hybrid power, multicopters, fixed or tilt rotors, distributed propulsion, unconventional layouts and control, computer controlled safe flight with adequate redundancy, autonomous control systems, read-across from UAVs, and more: eVTOL is an inventors paradise!