Crosswind takeoffs and landings
All motor gliders equipped with a retractable engine have a problem at takeoff due to their crosswind vulnerability. The reason is the asymmetric pull action of the prop. It results in an increased torque because the prop is mounted on top of the plane. Therefore a movement of the horizontal axis occurs and lifts the empennage off the ground, turning the whole plane into the wind.
As can be read in the operation manual the maximum tolerable and demonstrated crosswind speed is 8 kn or 15 km/h (e.g. 3 Beaufort) – not a really high number.
Naturally we DO NOT advise you to take off or operate the plane under situations such as the one described, nor are we accepting any liabilities resulting from such actions. We as the manufacturer will accept NO LIABILITIES resulting from such actions. The following tricks are only to be regarded as kind suggestions if you do absolutely wish to operate a plane under those situations knowing about the dangers.
All limitations of the owner and flight manual have to be obeyed.
We suggest you follow the tested procedure for a crosswind component of up to 15 km/h (which may be 21 km/h total if the wind comes from a 45° angle) in a DB-808B.
- LINE UP
- Flaps +8°
- Full throttle
The following suggestions are only to be of any help in gusty conditions or when facing more wind.
1. Line up on the lee side of the runway.
The plane will naturally try to turn the nose into the wind. Lining up on the outmost opposite side of the runway will give you more time before crushing a runway marker. I assume wind from the right. Therefore you'll have to line up close to the left edge of the runway.
2. Push the flaps all the way to the front
You'll achieve the following results:
a. You have full aileron
b. You'll lift the aileron from the ground – recommended for uneven surfaces
c. You apply an extra pressure to the tail wheel.
I believe this need's some more in depth explanations since every pilot believes that more negative flaps results in a downward movement of the nose. This would indicate an upward force in the empennage.
This has proven to be false:
We know from experiments the a downward movement of the empennage is caused by a forward movement of the center of pressure on the airfoil. The performance of the airfoil will change to a low drag and small lift status. This causes the wing to actually drop down. The plane will pick up speed.This effect will not be noticed while rolling on the ground. The force that remains under those circumstances is the downward force of the empennage or tail of the plane.
d. You can pull on the stick as hard as you like with no need to worry about a stall speed takeoff. Once you reach a speed of 90 km/h you can apply +8° flaps and take off.
3. Drop the wing on the lee side and advise your aid
This may well be a different and hard to learn task.
In case you have an aid assisting you during takeoff (although there is actually no need for help with a DG-808B) please advise him or her to stand on the lee side of the plane – which would be the left side under our circumstances (wind from the right!). Aids often show a tendency to restrain the wing – especially if they are untrained. A lot of aborts have been caused by aids holding on to the wing and causing a movement along the vertical axis. Nevertheless it can be of some help if done correctly and on the lee side. But you are well advised to give it some training.
In any case the aid should stand at the outer side of the wing and hold on to the wing with his / her right hand (at the trailing edge). Tell your aid not to hold on to the leading edge. This will eventually end in a problem – he or she just needs to stumble and will cause the plane to turn around.
It works just as well without any aids:
Drop the wing to the lee side – exactly different to what you have learned for parking. The roll drag of the wing will compensate the windmill effect of the rudder (empennage). You can further assist this effect by applying aileron towards the ground. The wind on the upwind side will assist you as well as the grass and the aileron.
But of course this is a possible technique only, if the ground for the wing tip wheel is not to dirty and free of stones.
Keep in mind: “Leave the stick in the back left position!”
Do never start with a low wing on the upwind side. All drag induced to that will be of absolutely no help in a crosswind situation!
4. Increase the throttle slowly!
Do never apply throttle abruptly! The DG-808C will lift the tail up immediately! Some other types may even drop the nose.
The airflow around the empennage will slowly axis you in keeping the plane on track once the speed increases if you apply throttle smoothly. The tail wheel will slowly become replaced by the empennage. An aid can assist you up to a speed of 15 to 20 km/h if needed.
Keep in mind to pull on the stick until you reach a speed to lower the flaps. If that is accomplished you can return the stick to it's normal position and take off.
Be aware to give it some training on a large airfield
before testing these suggestions on a narrow airfield with a narrow runway!
Landing:
Due to a lack of asymmetric torque it is usually possible to land the aircraft even under worse conditions (more wind) as the set limit. This does not need to be that way though as I have experienced myself a couple years ago:
I encountered crosswind problems during the takeoff run at our airfield in Oerlinghausen. The wind had increased heavily and unnoticed by me during the whole flight. At that time you did not need to communicate via radio at our airfield. No position calls and nothing else was needed – therefore I was totally unaware of the crosswind situation. I know – it's been bad, but that's the way it was.
It had rained the days prior to my flight and the airfield was well known for being muddy in parts due to a missing drainage. Well, I didn't want to hit the muddy parts and decided to fly to the end to get to a full stop as close to the hangars as possible……
I'm not quite sure what I did “on impact“. I may have pulled the stick or I may have drifted due to the crosswind – nobody knows – it all happened too fast.
The aircraft was slowed down incredibly fast. The tail rose up into the wind and the whole plane slid on the fuselage for a moment. Then the plane turned – just like a windmill into the wind and continued to slide, finally coming to a full stop facing in the direction I came from. An uncontrollable movement along the vertical axis had been caused while sliding through the mud.
Result:
- A deep scar in the runway
- A dirty plane
- 20 min. time “wasted” to take the plane apart in mud
- An interesting picture on the next day!
Keep in mind:
- Always gather information on the wind prior to landing!
- Please try to avoid muddy runways!
- A spare tail wheel hinge is of good use!
We had a spectacular repair lately:
A customer had often destroyed the tail wheel hinge and decided to strengthen it. He had welded a strong metal (steel) plate to it. He thought that that would to prevent damages in the future….
Well, now the whole fuselage broke off just in front of the empennage....
Nobody buys steel plated for his or her car, welds them on and thing he will do a great job in accident prevention... right?
- friedel weber - 
- translated by Thiemo Gorath - 
Well the suggestions were too late for a friend - unfortunately:
He drove to Vinon with my brand new DG-808C while I was still in Albuquerque for the SSA Convention.
He had heavy tailwind / crosswind on his initial takeoff – stronger than allowed by the operators manual. He started with the flaps at +8 (Section 2!), the upwind wing was dropped (Section 3!) And he applied full throttle on takeoff (Section 4!)
The plane lifted the empennage, turned by 150° into the wind and all that happened before he could even think of reducing the throttle...
Result: A damaged tail wheel hinge and the wing tip wheels were ripped out.
Our conclusion?
Always read the DG Flugzeugbau Website!
The suggestions were posted 7 days prior to the accident! What a shame….
X-Wind Takeoff Procedures
Von: Pete Williams
Dear K-F:
I am still not positive if the left wing is on the ground at the beginning. If it is, it is in the dirt or stones. Putting the left wing on the tarmac of course moves the bird to the right out onto the runway. Sure would help if you had an overhead drawing.
FYI some USA pilots start a X-wind takeoff with the upwind wing up. Its all a matter of individual pilot technique and it makes good sense to NOT attempt a X-wind takeoff if the pilot is unsure of his ability to handle it. Weather cocking can take place in the blink of an eye and off you go into the boonies! Please remember in the USA most launches are from paved runways 75-100' wide.
The last time my DG-808B flew in Germany it collected some German grass and dirt in the wheel well which fell to the tarmac when I first lowered the MLG here in the states. Launching off of hard surface tarmac means faster acceleration, faster liftoff and faster weather cocking. In the USA
West winds are never steady in direction and velocity. Gusts are common and the airspeed
on final can vary 10 kts. The pilot "stirs the cake" with the stick all the way to touchdown, then immediate negative flaps to "nail" the bird on the deck.
Minden landings are always a challenge as the takeoff's in gust conditions which occur Winter Spring, Summer and not so bad in the Fall.
Regards,
Pete Williams