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Flying VFR in Rain?

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Flying VFR in Rain?

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Old 1st Nov 2018, 20:42
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Flying VFR in Rain?

Am I right in thinking that you can fly VFR in rain provided visibility is above the minimum distance (I could check the METAR for visibility)? And what about snowing conditions in a C172 which has no anti-/de-icing except pitot heat? Would it be prudent to turn back? Thanks!
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Old 1st Nov 2018, 21:10
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Rain is fine providing inflight visibility is above your license and airspace minimums. And it is above freezing.. which leads nicely into your next question. For it to be snowing you are likely flying in visible moisture in icing conditions.. often doesn't end well.
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Old 2nd Nov 2018, 01:02
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* When below 3,000 ft amsl or 1,000 ft above terrain, whichever is higher:
  • Clear of cloud and in sight of the ground/water;
  • Flight visibility 5 km.
* Special VFR: visibility of 1.5km and aircraft need to remain clear of clouds and some other requirements depending of CTR class etc. ( 3km for europe i think?)

- as tangoalphad said, visible moisture in icing conditions (most aircrafts with no anti/de-icing equipment prohibits flying into expected or known icing conditions, read your POH regarding that

- take into consideration the intensity of rain and type of droplets
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Old 2nd Nov 2018, 10:30
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Originally Posted by WestBoundPilot View Post
Am I right in thinking that you can fly VFR in rain provided visibility is above the minimum distance (I could check the METAR for visibility)? And what about snowing conditions in a C172 which has no anti-/de-icing except pitot heat? Would it be prudent to turn back? Thanks!
Yes, like TangoAlphad said, depending on visibility and also distance from clouds you can.
But of course pay attention to wich type of rain is, and clouds. We might fly below Cu and stratus but not below Cb or TCU, in this case just go around clouds otherwise turn back.
Consider to cancel the flight if you are not sure about embedded Cb, like a broken with Cb would lead me to cancel the flight.
IMHO flight under snow with an aircraft not IFR eqpd is a no go.

Have a safe flight.
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Old 2nd Nov 2018, 16:11
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That makes sense, thanks both!
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Old 4th Nov 2018, 01:13
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Sure you could. But don't confuse legal with smart behaviour or good pilotage. The primary purpose of VFR is to see and avoid. Judging visibility in rain is one thing but being able to see other traffic another. Depending on the type of airspace and situation, it might be tolerably ok or not. Also the question of disorientation / lack of visual reference might well make it unwise depending on your ability and skill level.

As for whether snow counts as known icing, again, good question. But the same points arise, Could it be legal, yes sure. You can have snow without icing. But also the converse is true. And the viz and disorientation points arise again. Actually, you can look at the freezing level to assist your decision. So the real answer is to think about and understand the weather in more detail and to decide if you really need or want to be putting yourself in that situation , taking in to account your currency, skill level and equipment.
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Old 4th Nov 2018, 12:03
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i'd like to echo what custardpsc said. As far as the rain goes - it depends where it's coming from - if you have patchy showers coming from small cumulus clouds, generally you can see through it and its fine. If however you are looking at warm fronts/nimbostratus clouds, you're looking for trouble, the visibility will not be uniform, you can enter the rainy bit and still see for a while, but the vis can drop rapidly and you can end up in a cloud in no time. Generally use common sense - if you see what's behind the shower - its fine, if you don't - don't go in it!

Snow wise it's the same story, however with an added risk- rain generally falls vertically down and as you fly through it you will notice the droplets going downwards and towards you which will feel natural. Snow however, if the flakes are light can go sideways depending on the wind. This can cause illusion that you are turning

Icing wise - unless it is really really cold, you will get air frame and prop icing sooner or later. They say that in order for the ice to not form you need to be in below -40'C, so yes - falling snow is icing conditions, don't go in it
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Old 6th Nov 2018, 03:18
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It's important to remember that this minimum is "in flight visibility". It doesn't take into account the loss of visibility from the rain hitting the window..... you may very well have great difficulty seeing through the glass even if you've decided the viz is above mins.
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Old 6th Nov 2018, 09:20
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In general I never set out to fly in rain. So that takes out frontal conditions - we are doing it for fun and enjoyment after all. But it does happen, most usually when showers or worse thunderstorms break out when the probability of them was low or before the forecast time. In that case I will try to avoid the worst heaviest showers but accept a light shower in a deteriorating situation to get home before heavier showers/thunderstorms break out, constantly trying to have an alternate in mind.
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Old 6th Nov 2018, 14:45
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Originally Posted by TangoAlphad View Post
Rain is fine providing inflight visibility is above your license and airspace minimums. And it is above freezing.. which leads nicely into your next question. For it to be snowing you are likely flying in visible moisture in icing conditions.. often doesn't end well.
So here is the jackpot question, what temperature would you consider to be above freezing? To be able to fly in rain conditions, without anti ice/ de-ice on your aircraft?

I would be more curious to know what kind of reliable equipment you have in a C-172 that can confirm you are not flying in potential freezing conditions?

Originally Posted by 22/04 View Post
In general I never set out to fly in rain. So that takes out frontal conditions - we are doing it for fun and enjoyment after all. But it does happen, most usually when showers or worse thunderstorms break.
Generally the forecasts for Thunderstorms are fairly conservative, more often than not you will see TS in the TAFs if there is any. My general attitude if there is TS around, I will never fly close to it, so that way no chance of flying in any rain from thunderstorms, because if you do, than that might be your final flight ever.
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Old 7th Nov 2018, 01:29
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Rain can seriously affect the lift and drag characteristics of certain wing aerofoils.
Anything with a laminar flow wing may have degraded performance in rain.
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Old 7th Nov 2018, 03:29
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Rain can seriously affect the lift and drag characteristics of certain wing aerofoils.
Anything with a laminar flow wing may have degraded performance in rain.
Well... no certified airplane will be dramatically affected by rain on the wings. Certain amateur built designs are reputed to be more sensitive to airfoil contamination. If you're flying one of those types, you should be seeking specialist type wisdom.

Rain, in and of itself should not be a problem for VFR flight in a certified plane. However, visibility, possible thunderstorms, and the risk of icing in cold air really do need to be understood. Flying in near freezing temperatures, which may include needing to climb, or flying toward colder air, can take you into freezing conditions. The discussion of icing is it's own huge topic, and well worth either understanding thoroughly, or avoiding entirely.

Similarly, flying in snow must be well understood. In very cold air (> -10C), you're usually fine, as long as the visibility is adequate. Warmer than that, and again, you must be very careful, in that as the snow can begin to accumulate as airframe ice. Though I am hardly conversant in Canadian original languages, it has been said that the Inuit people of the far north have seven distinct words to describe snow. That sounds entirely appropriate to me! The fact that it's white and falling does not define what it's going to be like to fly through it! For those in locales where snow is less common, the differences in snow may elude understanding. Look down at the lawn - you see grass right? Look more carefully, how many different leaves and species can you distinguish? Similar with snow, and yes, you can have more than one type of snow at the same time.

So, when you're in snow at all, be more aware of it than just "the grass" of the lawn. Consider it's consistency, temperature, flake size, and stickiness. The consider the ambient air it's falling in. With those in mind, consider the affects of impacting it and aircraft skin which may be a different temperature than the air you're flying in. Experienced mentoring flying is the best way to get to learn snow. Next to that, is being hyper aware while you fly very locally in snow. If it starts to stick to the airframe, return the wisely short distance to home right away. The other thing is to know where on the airframe to first expect to see accumulation. On strut braced single Cessnas you'll see the snow accumulate first on the upper corner of the windshield, where it takes the shape of the leading edge of the wing. The fact that it is not accumulating on the center of the windshield does not mean that it's not accumulating dangerously on the leading edges of the wings!

The saying that good judgement comes from experience, and experience comes from using poor judgement really applies to flying in snow!
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Old 7th Nov 2018, 05:19
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On strut braced single Cessnas you'll see the snow accumulate first on the upper corner of the windshield, where it takes the shape of the leading edge of the wing.
Thanks PD, I didn't know that. Useful to know, even though I probably won't be flying in snow in the 182 I fly. In my military Chipmunk days, where we routinely climbed and descended through stratus in icing conditions, the tank vent, sticking up above the wing, made a good icing indicator. It was amazing how quickly the ice built up.

Your post reminded me of Kate Bush's album 50 Words for Snow. Worth listening to - I mean how often do you hear Stephen Fry on a pop album?

Concerning flying in rain, during the first time that I flew in a rain shower - virga, so the visibility wasn't an issue - out of caution, I applied carb heat. The immediate rough-running was so intense, that I instinctively closed the control! Only after a few moments, did I realize it was due to the engine swallowing the melting carb ice. I had never had carb icing demonstrated to me!

The 182 I fly has a carburetor temperature gauge - most useful - I wonder why more aircraft don't have one. Even on the hottest summer days, I often encounter temperatures in the yellow arc on the gauge, which call for partial carb heat.
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Old 7th Nov 2018, 07:36
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Originally Posted by 2unlimited View Post
So here is the jackpot question, what temperature would you consider to be above freezing? To be able to fly in rain conditions, without anti ice/ de-ice on your aircraft?

I would be more curious to know what kind of reliable equipment you have in a C-172 that can confirm you are not flying in potential freezing conditions?
Well, in light aircraft you tend to be sticking relatively local so you would have a good idea, if you have done any reasonable amount of pre- planning, if you would be encountering freezing conditions or precipitation and take a cautious approach to it.

There is a thermometer in the windshield however they can be hard to read but I don't suspect they would be wildly inaccurate. My previous airliner suggested +5c in visible moisture should be considered icing conditions and Mr Boeing says +10c. In a light aircraft anything 'indicated ' or suspected to be a few below 5c I'd suspect you could perhaps start to notice something building on the airframe. Either way if you are in suspected conditions keep a very good check on the known ice accumulation areas and if you see signs of anything get out of there now. These aircraft do not fly well with ice.
However, make up your own mind with limits and a plan. I never understood pilots who seemed proud of being 'ballsy' flying an unprotected aircraft into potentially harms way. There are other ways to kill yourself that don't put incident life's at risk.
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Old 7th Nov 2018, 12:12
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With all of these conditions I think it is important to experience them first of all with an instructor so that if you are caught out then you know what to expect and handle it without panicking. Last winter it started snowing heavily from high level which was quite stunning to fly through with no issues - good viz with big flakes. Another time during circuits a far wetter/harder snow came across the airfield and we decided to stay local until it passed.

The lesson was to stay local if the forecast was uncertain - go up to experience the conditions but don't plan for lunch on the IOW as you might not be able to safely get home!
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Old 7th Nov 2018, 18:39
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Cold snow in cold air will tend to bounce off a cold airframe: cold being well below freezing.

Between - 15 to 0C snow crystals soften up and get more sticky. In faster airframes there is some temperature rise, less so in a 172.

Then there's snow density, which is highly variable. Here in Canada I've encountered snow streets and picked out the thin spots. The thick stuff looked IFR to me and I stay away. This is a time when you want to be careful about terrain and towers below the cumulus.

If the clouds are scattered, flying over them can work.


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Old 7th Nov 2018, 19:10
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Originally Posted by syntax321 View Post
* When below 3,000 ft amsl or 1,000 ft above terrain, whichever is higher:
  • Clear of cloud and in sight of the ground/water;
  • Flight visibility 5 km.
* Special VFR: visibility of 1.5km and aircraft need to remain clear of clouds and some other requirements depending of CTR class etc. ( 3km for europe i think?)

- as tangoalphad said, visible moisture in icing conditions (most aircrafts with no anti/de-icing equipment prohibits flying into expected or known icing conditions, read your POH regarding that

- take into consideration the intensity of rain and type of droplets
Actually, in the UK, Class G below 3000' and 140 kts, vis requirement is only 1.5km. Whether you are comfortable with that minimum is yours to decide.
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Old 7th Nov 2018, 20:00
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Having learned to fly on the west coast, half the my instructional (dual) and solo flights were conducted in rain. I initially thought the question was a troll, as no licensed pilot would ask such a question. However...

I was cautioned in basic ground school and again on my Mountain Flying Checkout of the following optical illusion: "Rain on the windscreen can create an illusion of being at a higher altitude due to the horizon appearing lower than it is. This can result in the pilot flying a lower approach. Additionally, when flying in moderate and heavy rain, the crests of hills and mountain tops may appear lower than they actually are. Combined with a lee/mountain ridge downdraft, the flight may result in CFT."

Last edited by evansb; 7th Nov 2018 at 20:32.
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Old 7th Nov 2018, 20:26
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I initially thought the question was a troll, as no licenced pilot would ask such a question.
I don't feel that way. I completed my PPL training (in Ontario) without encountering rain. I recall one of my first flights as a newly minted PPL, blundering into rain in a 152, and wondering if it was okay to fly it in rain. It was. The question is reasonable, and useful to ask, rather than being afraid to ask.
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Old 7th Nov 2018, 21:08
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I'd be very wary of flying under any cloud that might drop snow, for visibility. Often when driving I've encountered visibility in snow that would be severe IMC.
Rain with decent visibility is no problem, as long as cloud base is high enough.
I find the legal minima for visibility far too low.
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