Lange Factory Visit, April 2009
I (Dave Nadler) visited the Lange Aviation factory in March/April 2009, and attended the huge Aero Aviation Convention in Friedrichshafen with Lange as well. The Lange Aviation factory is very busy cranking out gliders, finishing the sustainer installation design for the Antares 18T, and building the DLR-sponsored H2 hydrogen-powered research aircraft .
For competition in the 18-meter Racing Class, the Antares 20E was originally designed to accept smaller wingtips (shortening the wingspan from 20-meters to 18-meters). Most European 20E customers were not interested in the short tips, so this project was on the back burner. In the USA, more of us want to race the 20E in 18-meter as well as open-class competitions, so now Lange Aviation has completed testing and made this option available for aircraft with experimental registration.
While you might think that shortening the wing span should make it easier to avoid flutter, this is not necessarily correct. With a very thin and very high aspect ratio wing like Antares, calculation showed that the flutter margin was similar to the 20-meter case, and consequently flutter testing was required prior to releasing the wingtips to customers. Tests required included 12 different configurations (with water and dry, different flap settings, etc).
Flutter testing is a very serious business ! Tests are conducted from FL150 (15,000 feet altitude), which requires ATC permission, oxygen, and of course clear and smooth weather. The test aircraft is fitted with masses to simulate the worst-case allowed control surface moments on the flaperons and elevator (the masses are the difference of the test aircraft moments and worst-case). This ensures the no examples of the design will flutter, even years later when someone refinishes the flaperons and changes the control moment to the specification limit. For Antares 20E tests, an aero-tow to FL100 followed by self-powered climb to FL150 is used - it takes an hour to reach the start altitude as the aerotow climb is slow at the higher altitudes.
18-Meter Test Flight Photos
Here's Dick Van Grunsven's Antares 20E ready for the 18-meter tip
flight-test.
Note the external masses on top of the flaperon for
flutter testing.
Axel Lange preparing for the flight test, complete with
oxygen mask and flight test information on his knee-board.
Axel Lange returning from the successful flight test in RV.
RV at long last leaves the factory next week,
starting the journey to its new home in Oregon.
On this trip, I spent a lot of time working to organize repair parts for a customer's damaged Antares. The accident that damaged this Antares is the stuff of nightmares. The pilot did everything right, but as he was accelerating down the runway, a tail-dragger with no radio and limited forward visibility entered the runway from the opposite end and started to take off. The Antares pilot slowed down as best he could but eventually steered off the runway to avoid a head-on collision. Fortunately the pilot is OK, but the glider was badly damaged.
Master-craftsman Dave Nelson has completed the major structural repairs of this glider, but a lot of detail remains. One of the problems with a big repair is accurate positioning of all parts, especially interior parts such as control-system supports. The factory uses big jigs to position interior parts, but they are not useable for a repair. So, this past week we built fixtures for holding parts in the correct location, and took numerous measurements for verification of a perfect repair.
Plus the usual work of carefully reviewing customer option lists (I'm told customers become agitated when their new glider arrives with the wrong contest letters). A lot of work !
OK, As I have been asked a million times: Why would a company that has delivered 50 electric-powered motor-gliders use a gasoline-powered sustainer motor in the Antares 18T ? The answer lies in the energy required for a sustainer. Pilots expect a sustainer to be able to cruise for a long distance in order to get home. The energy required for this very long cruise is a good fraction of the energy required for a self-launch ! Most of the cost and weight of an electric motor-glider power system such as Antares 20E is in the batteries and battery management systems (heating, cooling, charging, balancing). The electric motor itself is not so big or heavy or expensive as alternatives. So, an electric sustainer with reasonable performance is a good chunk of the cost and weight of a self-launch ! Not a very good idea.
The sustainer in the Antares 18T uses a large Solo motor (originally used in the Ventus CM), with a large propeller and reduction drive. This will yield excellent climb rates at sea-level, and acceptable climb-rates at high density altitudes. Lange has also done significant work to minimize the vibration of this installation - many sustainers suffer reliability problems due to high vibration, which Lange hopes to avoid.
Antares 18T Sustainer Photos
Lange technicians work to install the motor in the prototype sustainer.
Preparing for opening at the Aero show (sorry the lights were not yet on full).
In foreground is an Antares 18T with installed sustainer,
with an Antares 20E electric-powered machine in the background.
The H2 research machine is a massive undertaking. In addition to its research value, it is good to have a steady source of work to keep the factory humming in the current difficult financial environment.
H2 holds the fuel cells in an underwing pod. The hydrogen tank is carried in another underwing pod on the opposite wing. Compared to the Antares 20E, the H2 wing structure is greatly beefed up, adding mounting structure for the two underwing pods. And of course, lots of plumbing and cabling and electronics to move around hydrogen fuel and electric power. This is a very heavy machine (we'll see what the final weight is shortly). First flight should be during the week after Easter.
H2 Construction Photos
Fuel cells ready for mounting.
DLR technicians testing the fuel cells, mounted in the pod structure.
The hydrogen storage tank, which lives in the underwing pod
opposite the fuel cells.
Wing mounting attachment for underwing pods.
There is a lot of structure in back of the mounting pins !
This was a very interesting trip ! Seeing the factory over a couple of weeks let me watch the steady progression of gliders through the construction process. I saw an Antares 18 (for a North American customer) go from incomplete fuselage halves in the molds to a fuselage ready for interior parts installation, and a 20E (bound for Switzerland) complete initial assembly and head off to the paint shop. Not to mention all the activity on the H2 and sustainer projects. A very busy time at Lange Aviation !
Next week I'm off to California to brief two new Antares 20E
owners on operation of their new toys,
then hopefully a quiet few weeks home in Boston.
From Zweibruecken, Best Regards, Dave "YO electric"
For more information on the Antares 20E and the Antares 18S/18T,
contact Lange's North American representative Dave Nadler at:
Dave.Nadler@nadler.com or at 978-263-0097 (EST).
On the web, see:
www.Nadler.com
Lange web site
Copyright © 2009 - Dave Nadler - All Rights Reserved