aerial vertical or horizontal

[chris10]

Are all 1090mhz aerial vertical or horizontal on the aircraft, i know the aerial is for indoor use, but i see no problem putting it outdoors, some grease and waterproof tape, renew coax say every two years.
ps; as a radio ham, all my aerial are grounded,take my advice ground all aerials.

chris

[malc41]

I think that they are vertically polarized.

From what I can remember the only aerial on an aircraft that is vertical are the ILS antennas.

But could be wrong?