Rain repellent system on windshield .
 

How do these work ??

Rain repellant.
 

Rain repellant when applied to a windshield causes the rain to run off faster and easier than if there was no rain repellant. Something like if you apply Rain-X to your cars windshield. I believe that most rain repellant reservoirs are no longer filled with rain repellant due to environmental concerns.

Rainex applied to the 737 windscreen before take off works perfectly. Some pilots in SA Asia carry a bottle in their nav bags.

bet security like the bottle
 

try explaining to the TSA that it is your windscreen washer fluid.

back to the question, i am assuming that it all to do with surface tension, the liquid sticks to the perspex, and the rain just can not stick to the n
ew surface.


glf

Washer fluid is different to rain repellant!

Rain repellant systems have been deactivated on a lot of a/c, ours have a hydrophobic coating applied at regular intervals to the utside of the windscreens (glass bit), works a bit like rainex I guess.

Rain Repellant
 

On those aircraft with Rain Repellant systems the normal method of using the system was to NOT APPLY the repellant until the windscreen was wet. To apply to a dry windscreen was a NO NO.

It is a hydrophobic silicone polymer that forces water to bead and roll off.

Rain-X's primary active ingredient are polysiloxanates, the primary one being hydroxy-terminated polydimethylsiloxane.The polysiloxanes have functional groups that bind to the hydroxyl group of the glass surface.

The most important disadvantage of RainX is in the fact, that a large part of the liquids that splash on the cars windshield is not the pure water from the sky, but dirty water from the road. This water contains small droplets of oils from the road. While the water does not wet the modified glass surface, the oil droplets adhere to it very well.

These oils have very high boiling point and, unlike water, do not evaporate easily after the rain. This could lead to smearing if a significant amount of oil is deposited on the windshield. However, this can be cleaned off with washer fluid or with a squeegee.

There are 2 types.

First, where rain repellant is 'polished onto' the windscreen by the engineers and wipers are not used. Rain will run off the windscreen in large globules leaving a relatively clear screen.

Second, where a fluid is squirted on to the windscreen when heavy rain is obscuring your vision and it 'clears' a path for you to see through.

I prefer the first!