Why I like my Motorglider
Pete Williams, who flies from Minden-Tahoe Airport, Minden, Nevada,
takes us through a flight in his DG-800B.
The article was published in Motorgliding International.
If you want the most exciting soaring experience you have ever dreamed of, then you need to take a flight in the DG800B. The 800B is the new generation of German made powered sailplanes with the capability to self-launch using an engine that is stowed in the aft fuselage.
No aerotow is required and the DG-800B can taxi out to the runway unaided. Looking at the sailplane, it is difficult to believe that in the sleek tail boom there is a powerful engine that has the capability to produce a very rapid and steep climb to the nearest thermal. So let's get started.
Before entering the cockpit, extend the propeller pylon by turning on the master electric and engine master switch and selecting extend on the manual extension switch. You will hear the electric motor raising the pylon as the aft fuselage doors swing open. A flashing yellow light on the engine control console tells you the pylon is moving. Out comes the large paddle blade propeller and a radiator.
To not put undue pressure on the pylon pivot points, do not extend the pylon all the way but to just short of the vertical. Now that the pylon is extended, walk around to the rear of the sailplane and inspect the engine bay. Note the muffler in the bottom of the bay and the connection of the engine exhaust manifold pipe to the muffler pipe.
The engine rotates 90 degrees and is attached to the pylon. As you pull the prop through two revolutions, the 10.9:1 compression ratio is quite evident. This model DG-800B has a British made liquid-cooled Mid-West two-cylinder, two-stroke with an output of over 50 hp at 6250 engine revolutions (2083 prop revolutions at a ratio of 3:1).
It has dual carburetors, dual electronic ignition and dual spark plugs and runs on a mixture of Avgas LL 100 (or auto super unleaded) and two-stroke oil mixed at 40:1 ratio. Check the propeller hub attachment bolts for safety wire integrity and paint marks, as well as several other items found on the printed engine bay preflight check list.
Complete the airframe check list, enter the cockpit and prepare to start the engine. In the dead center of the instrument panel is a horizontal display with switches, lights and a digital liquid crystal readout. This is called the Digital Engine Indicator (DEI) and provides the pilot with all he needs to know about pylon position, temperatures, voltage, ignition, rpm, generator, fuel, engine priming and limits. The Digital Engine Indicator tells you all you need to know
Just to the right of the DEI is the engine compartment fire warning light. After completing the airframe part of the cockpit check list and securing the seat harness, you are ready to start the engine. It's a long reach to the DEI, so make sure you can operate all the switches before the start. Put on the headset because it's going get a bit noisy inside the cockpit. Close the canopy and set the wheel brake. A wheel chock and crew person, while not absolutely necessary, is recommended.
As you place the ignition switch in the up position, the pylon extends fully, a green light will appear on the DEI and you will hear the electric fuel and water pumps running. Flick the prime switch to auto, call "Clear" and push the starter button.
While looking in the rear view mirror you can see and feel the prop cranking. As the engine fights off and settles down to a dull purr, turn off the auto prime, check rpm and temperatures (both CHT and EGT). The red generator light should be off.
Continue the warm up at 2500 rpm until the coolant temperature reaches 60 degrees C. All warning lights should be off on the DEI except the green ignition light. Increase rpm to 3000 and test the dual ignition system. The drop should not exceed 300 rpm.
Hold the wheel brake full on and run up to 5000 rpm. (This may require the crew to keep the nose from dipping towards the ground.) During the full power check, you will notice an increase in noise and vibration. You will also feel the thrust. Check coolant temperatures and EGT, if installed. If a crosswind take-off is expected, make sure the windward wing is the low wing before you taxi. To begin to taxi, reduce to 2500 rpm and release the brake (pull chock).
The DG-800B will immediately begin to move and may require a touch of brake and a slight reduction in power to establish a comfortable taxi speed. Tail wheel steering is responsive and positive.
Head for the runway and keep a lookout for other aircraft during taxi and prior to moving on to the runway. After making sure the runway is clear for take-off, lower the flaperons to +8 degrees, check elevator trim full aft, spoilers down and locked. With all other pre-takeoff checks completed, announce your departure, move on to the runway and add full power when lined up.
As the propeller unloads, the growling acceleration will be more than brisk - it will paste you back in the seat. Aileron control is almost immediate and by the time you can count to eight, the aircraft will be airborne with rotation at 49 kts. The climb rate is guaranteed to exceed your expectations as the 800B literally leaps into the air!
As the ground falls rapidly away, it's time to check temperatures, rpm, rate of climb and altimeter - 1000 ft agl comes quickly. Raise the wheel and climb toward the house thermal. The take-off performance of the DG-800B clearly defines what high performance self launching is all about.
While you are experiencing some cockpit noise, remember that the outside noise is a very low 57,1 db(A) which is 18.9 db(A) below the ICAO limit. The buried engine and low prop rpm makes possible an environmentally friendly aircraft, thanks to German know-how. When the lift rate on the variometer rises rapidly and remains between 8 - 10 kts, it's a good indication a thermal has been found. Start the thermal turn and if lift is confirmed reduce power to idle. Maintain 45-49 kts, switch off the ignition and watch the propeller in the rear view mirror.
As the propeller comes to a stop the pylon retracts a few degrees. This allows the propeller arc to line up with the rubber prop stop. The pylon will not retract until the propeller is in a vertical position with its tip against the prop stop. Step the propeller to the vertical by pushing the starter button intermittently or nose over to windmill the prop to the vertical.
As the prop stops in the vertical position, the proximity switch activates the electric screw jack which retracts the pylon. The yellow engine traveling light illuminates as the pylon retracts and goes out on full retraction as the fuselage doors bang shut. Activate the total energy system.
When the thermal tops out, select -10 degrees flaperon and accelerate to 75-80 kts. Check fuel quantity, engine coolant temperature and battery voltage, then turn off the master engine switch.
You are now flying a 50:1 high performance sailplane.
The following story was published in the ASA-Newsletters - issued by Pete Williams:
A Short Story by Friedel Weber - President of DG Flugzeugbau
Pete, if you correct my "Doughnut-English"
(good enough to buy a doughnut in San Francisco)
you can publish this note.
"In May 1996 I flew the DG-800B for the very first time. I already was the owner of the DG factory. That means that I bought a DG-800B and after Glaser-Dirks bankruptcy, I bought the whole company before I ever flew a DG-800B!
Well, I climbed up to 10,000 ft and I was very satisfied that the sailplane was flying so stable and so powerful - much better than my DG-400! Then I tried to retract the engine - but nothing happened. The propeller brake of that ship was a completely different design than the DG-800 today and it failed.
So in that moment I was very, very anxious. I thought:
"This is the prototype, and I am the new boss. Of course I can land this plane with the extracted engine, but if I damaged anything, all my new employees would laugh about the piloting ability of the new boss."
I attempted to contact Mr. Dirks via radio about what to do, but he had left the airport already. So I was gliding and gliding and did not know the emergency procedures. (I did not read the handbook at first!!!) I also did not know that the pilot can retract the engine easily without any brake using the prop stop system.
The ship was flying very smooth and so after 20 minutes I made a wonderful landing - Thank Heaven! And from that date on, I was convinced that the DG-800B really is a very easy to fly sailplane.
This was the story of my solo in the DG-800B. It happened with the factory No. 8-8B1, the very same sailplane which some months later was sold to Pete Williams."
Best greetings to all of the ASA pilots and
Always Happy Landings, Friedel Weber
"Microburst"-Flying
Pete Williams from Minden/Nevada wrote the another e-mail to me: |
Dear K.F.
Your newsletter continues to be very informative. Sharing safety information is a good idea.
I experienced a "microburst" recently while flying my DG-800B on a 500 km out and return speed record attempt. Perhaps what I learned can help others.
A camera would have been helpful in describing a thunderstorm day with heavy rain, turbulence, darkness under the clouds and frequent flashes of vertical lightning striking the ground. The location was a few miles north of Mono Lake, California.
I had successfully reached the turning point and the speed was just over the existing record. Perhaps this was THE day! As I pressed on it became evident that I must reach the sun edge of the cloud shelf ahead to get the lift needed to continue. Directly ahead was a heavy down pour of rain which seemed to strike the ground and then curl upward again like an inverted flower. As I got closer, while still clear of the rain, I found smooth lift and climbed alongside the shower to about 13,000' MSL (ground level in this area was 6,500'). Now the task was to circumnavigate the rain and head for the edge of the cloud shelf. I turned left and flew as close as I dared to the shower on my right. Large drops of rain began to pepper the canopy like stones. I turned further to the left.
Suddenly the sailplane began dropping at an alarming rate, almost vertically in very rough turbulence making it almost impossible to keep the wings level. Within 3 minutes I had dropped 5,400' from 12,800' to 7,400' (1800 fpm down!). It was time for the engine!
Out it came slowly as I waited for the green light. It seemed to take forever and the only field available was a small farm about 1,000'
below me. Finally I hit the starter button. The engine started and stopped. I turned on the prime and tried again. This time it ran and almost at the same instant I hit very strong lift and was literally tossed back up to 12,800' in less than 3 minutes. During this climb I noticed 17 kts of lift on the vario. I then shutdown the engine and completed the task.
What was learned?
1. Do not fly close to heavy thunderstorm showers.
2. Raise the engine sooner even if the descent rate cannot be totally overcome by the climb rate with the engine running.
3. Have a suitable landing field nearby.
4. Seek a safer route around T-Storms even if you must deviate widely from your selected course.
Pete Williams
N885N