I learned about flying in snow today - but still need more answers

[knobbygb]

Had to make my first go/no-go decision as a real pilot today, and despite ending up flying through a snow-shower I still probably think it was right to go.

Beautiful blue skies, scattered at 4000ft, ground temp +1C, but with occasional snow showers forecast throughout the day, mainly further east, near the coast. All the club instructors and solo PPL's were flying, and the general consensus was to go but just avoid the snow showers.

Anyway, once airbourne we soon came upon a band of thick dark snow clouds down to about 800ft, clearly defined and moving slowly north towards us and stretching as far as we could see in either direction, completley blocking our route to a local airfield 30 miles to the south. The outside air temp at that point was -5C so I was VERY aware of avoiding any precipitation which might cause airframe icing. Anyway, there was a gap in the cloud - looked a mile or so wide and clear blue sky could be seen on the other side so I decided to nip through the gap. No problem I thought, except about a mile before the 'gap' we were suddenly in near blizard conditions with snow all around and poor visibility, although still VMC (just). Pitot heat on, and a quick and very steep 180 turn later and we were back in clear skies (much to the surprise of my first passanger who I didn't have time to warn about the steep turn) :D

Anyway, we did a few stalls and PFL's back near base by which time the cloud had cleared to the west. Continued down to Gamston in near perfect weather with virtually unlimited visibility and a beautiful day was capped by watching the Red Arrows practicing their stuff in the Scampton overhead 10 miles away - complete with smoke-effects and everything.

So, I leared to be VERY wary of snowstorms (which I sort of knew already, really), and to think at least three times before trying to get through small gaps in weather, but have a couple of questions for the more experienced out there:

1) Why did we find ourselves in snow while still a mile upwind of the cloud? We had a 10kt tailwind and I assumed the actual snow would be on the other side of the cloud, blowing away from us) and didn't see any falling until it was all around us.

2) Common sense tells me that rain falling on a freezing airframe would be much more dangerous than snow. Is this a fair assumption? I imagine the (relativley) heavy raindrops hitting the leading edge, spreading out and freezing on contact, but the snow just seemed to follow the airflow around the wing - none seemed to stick - I was looking very carefully - believe me!

Obviously I'm not condoning deliberatley flying into snow, but I just didn't feel the situation was particularly dangerous especially as I turned back at the first sign of snow - probably in the snow for less than 20 seconds. Would others have done the same? Anybody got any particularly nasty 'snow stories'?

[charlie-india-mike]

knobbygb

I know what you mean. (First flight post getting my licence)
On Saturday and I flew into and rapidly out of a small snow shower at 2000 ft past Stapelford heading East. Had just said godbye to them to talk to Southend, 60 seconds later, hello I'm back heading West. Great day for flying although a bit cold.

C-I-M

[slim_slag]

Well there is always the potential of icing if the temps are right and the snow is wet. You really do not want to come across ice, nasty stuff.

A potential problem you didn't mention is getting caught in a whiteout and losing visual reference. Sometimes you just don't know what is in there, and 20 seconds at 120 knots is plenty of time to find this out! Cold snow or ice crystals is fun to fly through, if the temps are right, and you can fly on instruments.

Anyway, you lived to tell the tale, and that's always a valuable lesson!

[FlyingForFun]

Sounds very similar to my first pax's experience - it was rain, not snow, but also involved nipping through a gap in the clouds, and then a quick 180 when I realised it couldn't be done! Perfectly safe, but pax later admitted she was a little scared by it... so, as a result, not something I'd ever do again with non-pilot pax.

To answer your questions, though - or at least attempt to. First of all, the snow up-wind of clouds. Could it have come from a layer of clouds above you? Or, alternatively, could the wind above you have been blowing from a different direction? If there was a clearly defined layer, it could well have been associated with a front (I didn't look at any met yesterday, so I don't know whether there were fronts around) - this would fit in well with a "slanted" cloud layer, as well as different winds at different levels.

You are right - if precipitation is already frozen, it won't really stick to the airframe as much as rain - but there's still a chance. And it's simply too dangerous to take that chance. (The most dangerous type of icing is rain-ice, which you get in something called the "rain-ice triangle" - an idea which the ATPL met examiners are very keen on. It's basically the area just below a warm front. Rain falls from the clouds in the warm area of the front, and as it falls it enters the cool area of the front, where it becomes super-cooled and forms clear ice on the very cold airframe. Only marginally relevant, but never mind!)

FFF
--------------

[M14P]

I had two very interesting experiences recently.

The first was in Berlin on New Year's Day. It had been about -9 degrees for some time but we could see from the synoptic that a warm front was on it's way. Whilst we were in the bar (luckily) the rain started to fall thus encasing everything in ice, making our walk back from the bar near impossible and causing chaos at the airport. If your aircraft was stitting outside in that then it would look like a popsicle by the time you got back. The saving grace was that the air beyond the front was above zero so everything had thawed by the time morning came.

The second was -22 degrees conditions in Oslo. There was virtually no icing risk because the precipitation was so cold. The little ice crystals just bounce off. Despite landing on a contaminated runway there was no impingment ice on surfaces etc. Clean as a whistle!

It just goes to show - what they tell you in the met books is right. Icing risk is worst between Zero and -8 degrees.

That said, if you are flying in heavy snow in a piston (injected or carb) there exists the possiblity that you might choke up the air inlet. For those of you with injected engines who wondered what the Alt Air lever was for this is just such a case.

[knobbygb]

Thanks all. FFF, no, there was no cloud above to speak of and as far as I know the wind was fairly constant. There was a cold front moving north at the time, but I thought it was still further south, going off the F214 I'd checked pre-flight. Perhaps it was that, though.

Some of the clouds further away had rather wispy looking anvils developed above them, so I did expect turbulance around the clouds which could have blown the snow in the 'wrong' direction, but there was none that I experienced.

All I can assume is that I misjudged the distance from the cloud and also perhaps the size of the gap, after all there was nothing really to give an idea of scale on the plain grey background. Also we were doing about 125kts ground speed to the south and the cloud appeared to be moving north at perhaps 15kts, so at a closing speed of 140kts it's easy to misjudge. Main thing is - lesson learnt.

Aren't there a lot of threads about icing at the moment? Grounded or airbourne, us lot just can't stop complaining about the weather can we? ;)

[bluskis]

Added to all the physical hazards of flying in snow is the danger of disorientation due to the visual confusion caused by the snow hurtling towards you then veering away all around you . I expect the larger the flakes the worst the effect.

[knobbygb]

Actually that bit was quite fun ;) - actually FELT like we were doing 130mph! Sounded like a load of very noisy little things being tipped into an empty roses-tin too! (sorry, creative writing was never my strong point). Hmmm... perhaps it was a bit of light hail rather than snow...

[slim_slag]

knobby

A very sensible rule for low time VFR pilots is that if you come across rain/snow and you cannot see all the way through to the other side, keep out. As for hail, even the big boys keep away from that stuff. They keep the jets a long way from those anvil clouds as thunderstorms can throw lumps of ice further than you might think.

[bluskis]

Another point to be aware of. England looks very different when everything is white, so navigation needs careful planning.

[Send Clowns]

Congratulations on surviving your first dangerous situation, seemingly with calm, correct action!

As as been said probably the greatest danger you were in was white out. This is a thing helicopter pilots hear more of than fixed-wing, as they tend to disturb the snow near the ground (run on landings are the answer - they don't hover above snow). It has on two occasions I know of brought down three helicopters in succession, the 2nd and 3rd coming to the rescue of the first! White out is when there is snow or cloud around and the ground is also snow-covered, so even if visibility is OK there is no defined horizon for reference, and disorientation can lead to spiral descent.

It is always worth reading up about winter flying before the first sortie of the season. At military bases there is often a winter-flying brief sometime in November to cover all the points, especially from the flight-safety officer (A chap called Rory Underwood gave this when I was at Cranwell!) de-icing before flight, night flying (dark early) and getting caught unexpectedly night flying, snow, icing and rain ice (the bugbear already mentioned by FFF, possibly the most dangerous weather regularly found in the UK after thunder storms).

[TheSilverFox]

Knobby.

Welldone on the decision to get yourself back into more comfortable flying conditions. But why the steep turn????
With reduced visability (and probably horizon) there is a far greater chance of messing up your steep turn and finding yourself recovering from a spiral dive!
If you find yourself in a similar situation in the future, dont panic,
set up a nice gentle rate one turn if the vis is really bad, or a medium level turn if you still have a reasonable visual horizon and you will be out of the snow in no time.

I wonder how good your lookout was prior to commencing that steep turn?

Finaly, speaking as somebody who has spent many hours flying passengers in light aircraft. The one manouver that is guaranteed to scare your passenger (and possibly make them sick) is a steep turn, particularly if they are not given any warning(even in good VMC)