DC-ATE
Not having tail anti-ice doesn't mean it won't accrete, it just means the accretion won't affect control and stability as prescribed in FAR 25. The 4 inches was there, it just didn't have a control effect.
I think there is something to the "bow wave" effect forcing some of the water droplets to not impact and accrete on the airframe. The bow wave of a C-5 approaching a tanker is amazing and quite noticeable 50 feet back. I can see were the bow wave of a jet at 200 knots would have a centrifugal separator effect. Like I said, we didn't have any wing anti-ice on either the A-10 or the C-5 and they have flown around in lots of ice in NA and Europe without problems. I've flown in icing, for 4 hours around the traffic pattern, with ice detectors indicating icing with zero wing accumulations. Surface temps were about 0 C. I have seen ice build on the pylons and bombs on the A-10 but little to none on the wing.
GF