Odd optical effect

[Self Loading Freight]

(Not sure where to ask this, so I thought I'd try it out among those of us who get the most time to gaze out of the window...)

Was on an unpressurised VLM Fokker 50 from London City to Schipol yesterday, which meant a nice low potter across the briny on a sunny day (trying not to hum the theme to 633 Squadron). The water surface was spotted with white capped waves, and there was a visible swell. Very pretty, possibly less so if you're down there too.

Thing is, the swell appeared to be well below the white caps. The view looked like nothing so much as a shallow sea with a rippled bed and a few metres of clear water on which rode the white stuff. The illusion was so strong that I couldn't shake it, and I can't work out which visual cues I might be misinterpreting.

Has anyone else noticed this? Any ideas what's going on?

R

(I did see it on the way _in_ to Amsterdam, in case you're wondering...)

[Final 3 Greens]

SLF

Are you sure that you were not misinterpreting low stratocumulus cloud as the wave caps?

http://www.fas.org/irp/imint/docs/rst/Sect14/CloudRipples.JPG

[Self Loading Freight]

Yes - there were ships down there too pushing out wakes at the same level, and we were low enough that I could watch the caps evolve and break down. No mistaking them.

R

[Sl4yer]

Unpressurised? Maybe that caused you to see funny things.

I flew VLM from MAN to LCY last month, and it cruised at 15000 feet. I'd expect it to go at least as high to AMS.

[Self Loading Freight]

The only reason I think it was unpressurised was that there was no mention of oxygen masks during the safety demonstration. Is that an incorrect assumption?

R

[Reimers]

Indeed it is not a correct assumption. OXY Masks need to be demonstrated only on flights cruizing higher than FL240, the reason being that if pressurization fails below that level, the flight crew (who will put on their masks) will bring the aircraft down below FL120/12000ft within the time that you remain conscious, which for FL240 is around 5 minutes. So, even if you do not put on the mask, you may feel dizzy for a while, but as the aircraft descends, your body will receive more oxygen and any symptoms pass again.

If it were indeed an unpressurized flight, it would have stayed below 10000ft. This occasionally happens if there is something wrong with the pressurization system.

[liteswap]

C'mon Rupes. It was on the way _back_ wasn't it??