DG series gliders are known for their very large canopies. Among the advantages of the large canopy are outstanding visibility and a very comfortable temperature distribution while flying at high altitudes. In Spring flying at altitudes of 3,000 to 4,000 meters over the southern French Alps, I have been comfortable in a thin sweater and ordinary casual shoes when the temperature outside was -18 degrees C. The electric insoles I bought several years ago remain unused! (Does anybody need a pair? For sale cheap!) The large canopy, coupled with a strong canopy frame for crash safety, is a great advantage.
The one minor limitation is the relatively frequent appearance of disturbing reflections. This happens mostly in the foot region where, in other gliders, the instrument panel blocks the view. While it can be disturbing, the easiest solution to this problem is simply to wear dark clothing. I use black jeans and dark colored shoes. A friend of mine flies with thin ballet shoes. This works because of the good temperature conditions under the canopy and the shoes are as comfortable as slippers.
It would be better, of course, to have a more built-in solution to the problem. We have discussed the possibilities with the canopy manufacturer (Mecaplex) in Switzerland. Unfortunately, an anti reflective coating of the type used with eyeglasses is not feasible. These coatings are costly and not very durabl
Mecaplex recommends using a tinted canopy which greatly reduces the reflections. Wilhelm Dirks, our chief designer, has a tinted canopy on his glider. He reports no disturbing reflections, and no problem landing even when it is nearly dark. The loss of transmitted light due to tinting during cloudy weather or in the evening is not a factor. Generally the problem in aircraft is too much light.
On the basis of our experience, we highly recommend the tinted canopy. Not only are the reflections much less bright, the tint is also much easier on the eyes.
We also asked Mecaplex about the transmission of UV light through the canopy. The canopies do not totally screen out UV, but do absorb about 95% of it. That means the sun is no problem. For long flights which may reach high altitudes, pilots with no previous exposure to strong sun should use a topical sunscreen. Direct UV-Blocker are not necessary.
Tinted canopies even give a little better protection from UV rays.
Above you can see a canopy of 1929!
– friedel weber –
I can make the last point clearer by my own experience flying in Namibia:
The sun in Africa stands nearly at the zenith and yet I was able to fly without sun cream and still not burn even during long flights. The canopies seem to be opaque to UV light.
The Myth about Overheating:
It seems logical that under such a large canopy, it would become very hot.
Hotter than under a normal canopy; is that really true?
When the glider sits unprotected in the sun, in Namibia, for instance, naturally it would become unbearably hot in the cockpit. That happens the same in other gliders with normal canopies. Having to wait at the starting point would be impossible.
The quality of the ventilation in flight is what makes the difference as to whether it is noticeably warmer inside the cockpit as compared to outside. Here is a small calculation with respect to this:
The DG-800 has an air intake in the nose that is 38 mm in diameter. The air flows in unhindered and immediately the air passage becomes larger so that the ventilation valve does not hinder the air flow. At 65 knots, 30 liters of air per second flows through this opening. That means that every 10 seconds the air in the cockpit is completely changed if the valve is fully open.
It is easy to see that no amount of insulation is strong enough to noticeably warm the cockpit in 10 seconds!
On the other hand, if you need extra warmth from the sun, for instance at 20,000 ft, it is there. I have experienced flight at this altitude with an outside temperature of -20 deg C and needed only a wool pullover and ordinary shoes if the ventilation was fully closed.
(Translated by: David Noyes)
Improvement of the Canopy Fit:
New canopies on all new sailplanes are difficult to close because there is still stress in them. This cannot be avoided in production.
Interestingly enough, this characteristic disappears after a few months and the canopies close easily.
The reason for this is that the canopy material and the canopy rim need time to fully post harden and relieve the internal stress.
In order for the two to fit properly after ageing, they must be latched together as much as possible.
For this reason, here is an important suggestion:
When the glider is stored, always latch the canopy – especially with new gliders.
This is especially important if you store your glider in a trailer which stands in full sunlight.
Even if the canopy is difficult to latch, it will be okay latest after one year.
Sometimes you just can’t close the canopy of a new glider.
That happens when you leave your glider standing in the sun with a closed canopy. The inside air temperature and canopy heat up to a very high temperature. Simply open the canopy for a few minutes in the wind and it will cool off enough to close without any problem.
But the canopy latching system can be modified to remedy this. Whether this is necessary or not can be determined by looking from the left side of fuselage diagonally back to the opening mechanism. Look at the black metal plate with the hole for the locking bolt and through this hole the mating hole on the fuselage. Both holes should more or less line up.
At higher temperatures the canopy expands and the hole on the fuselage side is misaligned with the hole in the locking metal piece. Loosen the 13 mm lock nut on the fuselage side and turn one turn inwards. In winter it can be turned back out again but probably by then the canopy has fitted itself.
Avoiding cracks in the canopy
If a canopy breaks the reason is almost always that someone has put his hand through the DV panel from the outside and exerted pressure onto the corners of the DV panel. Unfortunately the DV panel presents a weakness in the canopy structure putting pressure on it causes considerable strain and despite the rounded corners of the window you may end up with a crack that will expand unless you drill it. Cracks like that can also very easily originate from the holes for the DV panel rails Im sure you are all aware of that and also that you should never open the canopy by holding on to the DV panel.
Now let me wish you a clear view of things at all times!
Translation: Claudia Buengen
To Avoid Reflections
Especially in two seaters reflections are rather critical.
This photo was not taken in a DG-Glider. You can see very precisely that the white hat of the person on the front seat causes very strong reflections.
In Two Seaters the pilot on the front seat should wear a dark hat only!
– friedel weber –