{"id":13501,"date":"2016-12-05T17:12:32","date_gmt":"2016-12-05T16:12:32","guid":{"rendered":"https:\/\/www.dg-flugzeugbau.de\/en\/?page_id=13501"},"modified":"2017-10-13T14:53:46","modified_gmt":"2017-10-13T12:53:46","slug":"safety-paint-sailplanes","status":"publish","type":"page","link":"https:\/\/www.dg-aviation.de\/en\/library\/safety-paint-sailplanes","title":{"rendered":"Safety Paint on our Sailplanes"},"content":{"rendered":"

For improved visibility it is recommended that the sailplane is painted as noticeable as possible.
\n Unfortunately dark colors have the undesirable characteristic that they heat up enormously in the hot summer months. The greatly increased temperature decreases the strength of the material.
\n To provide universally applicable guidelines as to which parts of a sailplane can be painted, Wilhelm Dirks has issued aService-Info, which is also of interest to many owners and repair shops:<\/p>\n

Service-Info 2011-72 Safety Paint<\/a><\/span><\/h4>\n

– w-dirks –<\/p>\n

\n

That is the “official” position of the manufacturer<\/p>\n

Some pertinent remarks:<\/h2>\n

I have not been able to find a study of the differences in visibility of sailplanes with or without such paint.
\n Has anyone seen such a study?<\/p>\n

I had the personal experience in fairly poor visibility to meet a two seater almost head-on that I recognized only clearly after seeing two stripes of reflective foil on the leading edges of the sailplane.
\n In southern France they attach bright red reflective foil to may airplanes, such as is used on military jets. This is not permissible according to the above standard . But because the sun is not as strong in the spring and the foil itself provides some insulation this practice may be acceptable.<\/p>\n

Please remember that a manufacturer must base his recommendations on extreme conditions which could arise when a sailplanes sits in the sun in Namibia and the pilot then executes an overly stressful winch launch.
\n The best paint would be daylight reflective paint such as a reflecting red. But to paint this on is more difficult and so more expensive than regular red.<\/p>\n

And please remember that only an authorized shop can install safety warning paint and has to be checked out by an licensed inspector. The rudder is especially sensitive to increase weight due to the extra paint. It could cause flutter.<\/p>\n

\n

We received news from Austria that it is planned to make safety paint mandatory even in regional contests to improve the visibility of sailplanes They also provide a sketch on how to install the paint.<\/p>\n

Wilhelm Dirks has replied to this news as follows:<\/p>\n\n\n\n
The painting shown in the sketch is not authorized, at least not in high ambient temperatures. We have begun tests of the heating of the surfaces. We found that the reflective paint does not heat as much as regular paint, but still more than white surfaces.
\n We tested Scotchcal Fluortape 7725-404 (yellow-orange). This tape is only 0.05 mm thick and is better than painting since paint would be thicker and also heavier, and is more difficult to replace when faded. But because our test were made at winter temperatures and sunshine we are not willing yet to approve it.
\n Because the destructive testing on glass and carbon fiber takes place at 54 C, these parts should not get warmer than that in actual use.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

translated by Albin Schreiter, CDN<\/p>\n

\n

A short Comment:<\/h3>\n

The U.S. Department Of Defense did work on this topic years ago.\u00a0 I’m not sure where you’ll find it — perhaps on NASA, Navy, or Air Force public web pages.<\/p>\n

One finding that I have heard is that darker coloring of the extremities of the aircraft can actually make it harder to see at a distance.
\n Apparently it has an effect of shortening the apparent size of the aircraft.<\/p>\n

Thanks for your newsletters,<\/p>\n

Jack Beavers
\n <\/a><\/p>\n

\n

An Investigation:<\/h3>\n

After the report that came out from Austria, we wanted more exact data and knowledge about the subject. Therefore we decided to make a \u0093scientific\u0094 investigation of the thesis. We made large sheets of sandwich material of the type used for wing skins. These sheets were divided into squares which were painted with different colors. The panels were laid out in direct summer sunshine and the temperatures were measured between the outside glass layer and the CFK layer with NiCrNi junctions.<\/p>\n

Here is a summary of the results which are, of course, not specific to DG but would apply to all sailplanes. It must be said in advance that in the certification process, the material must have a specified strength at a temperature of 129 deg F.\u00a0 (54 deg C)<\/p>\n

At an outside temperature of\u00a0 88 deg F (31 deg C) in direct sunlight on the white part of the panel, a temperature of\u00a0 111 deg F (44 deg C) was measured. The specifications are based on an outside temperature of 100 deg F (38 deg C) so that in such a case the surface temperature would be 124 deg F. (51 deg C)\u00a0 If the measurements would be made in equatorial latitudes with higher sun angles, then it is quite possible, that under these circumstances, on white surfaces, the specification temperature of 129 deg F (54 deg C) will be exceeded.<\/p>\n

This establishes the first finding:
\n White paint is sufficient to protect a glider from heating up to the specified 129 deg F (54 deg C) under extreme temperature conditions. Any color that leads to a higher temperature would cause a temperature higher than the specified temperature. This means that under these conditions, the glider would become illegal to operate with respect to the specified structural integrity.<\/p>\n

The next thing to do was go through the measurements of the other colors.
\n Using our previous setup, which achieved a temperature of 111 deg F (44 deg C) under white paint, the highest temperature among all of our test panels, the classic red warning paint, warmed up to 147 deg F. (64 deg C)\u00a0 That was 36 deg F (20 deg C) more than the white patch!<\/p>\n

Much less warmer were the daylight colors “Yellow-Orange”.\u00a0 The surface stayed about one degree cooler under the same colors which were not painted on, rather applied as foils.
\n Using a mirror finish like aluminum foil resulted in a cooling by one degree.<\/p>\n

The results were not a surprise.\u00a0 The more the absorption of the heat of the sun’s rays, the hotter the surface became.\u00a0 What is the practical result of this test?<\/p>\n