A. Concept

In the course of developing the DG-1000 into a whole product family, introduction of a variant with wing flaps was planned as the next step , together with the self-launching DG-1000M.

But to our surprise, ongoing discussions with prospective customers revealed the strong interest in an inexpensive auxiliary engine to allow safe return to the home base during a cross country flight. Particularly clubs are interested in this return capability to intensify cross country training and cross country flying without the risk of out landings. Their established launching capabilities by winch or tow would not justify the higher cost of the self-launch capability.

We listened carefully to our customers and changed our planning. The next addition to the DG-1000 family is the DG-1000/DG1001 Turbo, the variant with the auxiliary engine for return flights.

B. The Power Plant

We did an extensive market research for existing modern auxiliary power plants, not to invent the wheel again. Of course we had investigated different solutions, in particular the use of four stroke engines.

Two-stroke engines are less optimal than four stroke engines in terms of fuel efficiency and emission characteristics, but this is in our case not of significant importance. However, air cooled two-stroke engines excel by unbeatable simplicity. We don’t need a coolant or an oil system and save the associated two pumps. We also avoid cold-start problems and oil leakage when retracting the engine.
A four stroke engine would therefore be much more expensive.

A Cart engine built in Switzerland was offered to us, which would have been a good fit. But after the manufacturer became insolvent, we lost this little 4-stroke engine as an option.

Therefore we selected the well-proven Solo engine again; a two-cylinder two-stroke engine, used in a similar configuration in our LS8-st. This engine is paired with a comparably large two-blade propeller, a custom designby our specialist Dieter Schmidt. It provides a much better efficiency than a smaller and faster turning two blade propeller, or as an even smaller four-blade propeller.

The efficiency of a propeller typically increases with its diameter. But also the engine frontal area becomes less influential with increasing propeller diameter. A small propeller which blows mostly over the engine has obviously more drag and less efficiency.

Have you ever seen the inside of a propeller?
Please click on the picture!

C. Engine Control

 It is already “corporate tradition” that DG seeks for an optimum solution. The DEI in the DG-808C provides already outstanding comfortable engine control, contributing to improved safety. In the DG-1001 Turbo we go even a step further. The following list itemizes the actions required by the pilot to start the engine:

1. Ignition On

The DEI in the DG-1001 Turbo is always on, even in glider configuration (we report on this feature in another report). Therefore after switching the ignition on, the following sequence happens automatically:

• The electric fuel pump and the extension spindle actuator start concurrently
• The engine doors open and the engine is extended
• The fuel valve is always open
• When the engine is fully extended, the starter works, which knob you have hold down
• The primer injects the exact cold-start fuel quantity
• The motor starts and develops full power

2. Next step

Sorry, there is no next step! This was already everything needed!
At DG Flugzeugbau we call this:

“On-and-Go”

Stopping and retracting the engine is similarly “complicated”:

Switching the ignition off will bring engine and propeller to a full stop.

• The propeller stopper is extended into the propeller plane
• The propeller turns slowly until it reaches the propeller stopper
• The spindle actuator retracts the engine
• The engine compartment doors close

Again here is switching the ignition off the only required action, everything else happens fully automatic. In case of a malfunction allows a manual system to retract the engine without the need for any electronic support.

Such a sophisticated control system is not only a convenience for the pilot. It is even more an important safety improvement. An immediate response of the engine is typically needed at low altitudes, when the pilot is exhausted from unsuccessful search for thermal lift. In this stressful situation any single mistake with a conventional engine control system can prevent the engine from immediate starting and result in a dangerous situation for the pilot. Auxiliary engines are usually much less frequently used compared to engines of self-launching gliders. Particularly club pilots tend to be less fluent and trained in the usage of the auxiliary engine systems. The operation of the engine must therefore be as simple as ever possible.

We do not like an experience with the DG-1001T, as pilots with a competing type of glider have had, as they landed in a lake in southern France having forgotten to switch on the ignition….

D. Usage Spectrum

The DG-1001S is already known for its universal talent for cross country flying, pilot training and aerobatics. “Simple Aerobatic” such as Loop, Turn, Spin with positive g-forces are allowed also with the DG-1001T.

Furthermore the DG-1001T is certified also with 18m wing tips. So it remains also suitable for glider education and in this configuration the complete aerobatic program is allowed too.

Theoretically we also could offer a “DG-1001T Club” with fixed gear and fixed 18m wing tips. But practically that will not make any sense.

Last but not least a turbo engine can be used to support an aero tow behind a motor glider or a microlight aircraft.

– Friedel Weber – Translation: Manfred Koethe