Flight limits in falling snow

[rotorspeed]

With widespread snow the UK at the moment be interesting to know what limits apply to flight in falling snow in various helos, in terms of minutes flying permitted in a given vis. Any offers and views?

[TunaSandwich]

Prohibited in B412 without snow deflectors installed.

[Winnie]

the Jetbox requires Eng anti ice, Particle separator, snow baffles and automatic Re-ignition.

there should be 4 items anyhow.

Hovering limited to 15 minutes in falling snow.

Don't recall that there are any other limits.

The AS355F2 (FX2) was only a eng anti ice limit if I recall correctly

Cheers

edit: corrected the 4th element of the ice...

[Camp Freddie]

AW139 flight in falling or blowing snow allowed as long as not in icing conditions (vis <1000m + true air temp 0c or less)

CF

[ReverseFlight]

Not to mention possible white-out on landing ...

[SASless]

.....or Whiteout on takeoff and enroute.

[skadi]

BO 105 only with "continous ignition system" on.

skadi

[rotorspeed]

It's a while ago now, but seem to recall that the AS350 had no limit on time over 1500m vis, 10 minutes 800-1500m and was not permitted less than 800m. FM I've seen for AS355 doesn't specify anything. A109? AS365? S76?

[ShyTorque]

A109 not approved for flight in icing conditions in basic configuration.

S-76 similar.

[206Fan]

Is the L1,L2,225 puma fleet at abz approved for flight in icing conditions like today?

Just curious :ok:

Dave

[AAKEE]

Falling snow is not icing condition in (at least) 99.9% ot the cases.
Falling snow and limitations in flight often refers to risk of flame out if lot of snow has formed on roof of heli or at engine inlets. This could make the engine flame out if a lot of 'clogged' snow comes loose and goes into the engine.

Bell jetranger: snow defelction plates should be mounted.
MBB bo105: min 800 meter visibility. Possible to mount continous ignition probably allows lower vis. (dont know the civilian POH to 100%, but flew a military version).
AS332 super puma: no restriction in snow visibility, but about how long time ground run as allowed without check on roof(max 20min in 400m or less)

[skadi]

Check this thread for S76:

http://www.pprune.org/rotorheads/271681-s-76c-certified-falling-blowing-snow-ops.html

[John Eacott]

I can't recall the 212 limits, but the early days of the Brent Field we found the particle separator worked pretty well in passing snow showers ;)

FWIW, the external door hinges were/are the best ice accretion indicator on the 212. The wiper blade arm shows ice early, but is difficult to monitor compared to the door hinges.

http://www.eacott.com.au/gallery/d/2985-1/Brent+212+snow.jpg

[SASless]

What happened to all this Global Warming Al Gore has been bleating about?

[ShyTorque]

Perhaps we're paying enough extra taxes now, so it's no longer such a problem.... :hmm:

[Backward Blade]

As far as I know as per my POH the A-Star limitations (D,BA,B2, FX2 ammendment) as previously stated are correct although god/God knows why as sometimes the limited visibility is not always created by "falling snow" but also embedded fog.

That being said if you are running an FDC filter don't forget that once the light goes on in falling precip/snow you are GROUNDED! Just a little hint here... if your light goes on in flight pay attention to your T's and P's and you may not have to land "immediatly" and may be able to land at a spot that's a little more convenient. (Note:if you are questioning what I said just follow the book)

Don't forget to DI the workings of your bypass doors prior to each flight as well. If they don't work you are grounded and is not CLEARLY mentioned in the POH. Also, when landing for any length of time in falling snow when running the FDC filter, don't forget to put a cover on it....if you get a build-up of snow on it you can/will activate the low-flow light on start-up (Could also be indicated by T4) or just after lift-off. Don't mean to be a smart-ass but once you put the cover on don't forget to WALK AROUND YOUR A/C to make sure you took it off!!!

That being said does anyone know where the limited visibility flying in snow came to pass in the POH. Just curious as I fly in Northern Canada all the time, with and without FDC filters down to 1/2 mile and have never had an issue.

Any input from you boys over on the other side of the Pond would be greatly appreciated as here in Canada, no-one can get a straight "not covering my ass" answer from the "Makers"

Fly Safe ALL

Backward Blade

[[email protected]]

Our Sea King limits (we have a particle separator) depend on OAT and visibility; if the vis is above 2000m or the OAT below minus 6 degC then there is no limit.

The most restrictive limit is with vis less than 500m and the OAT above minus 6 degC when we have a 10 minute limit. This follows the idea that warm wet snow is the most hazardous due to accretion/blocking intakes etc.

[Hughes500]

500

Falling snow is fine as long as auto relight is on and their is no centre seat pax. Not the same in an E model, presume this is because the switch for auto relight in an E is half way up the panel, not at the bottom in pre e machines, where center seat pax foot may turn it off. Unless anyone knows better ???

[albatross]

Hi TunaSandwich:
Stupid question perhaps but why would a 412 require snow deflectors and a 212 not?

I have lots of time in a 212 in snow but all my 412 time is in the hot.

If the 412 requires deflectors could someone post a photo of them.
Just curious

[busdriver02]

Never heard of a falling snow limit before. The 60 is basically retard proof. Just turn on the anti-ice when encountering "visible moisture" below 4* C and you're good. I guess an inlet that heats to above 93* C helps. The power loss sucks though.

[topendtorque]

Al Gore is lauging all the way to the bank, helped mightily by the mightily pathetic platitudes of the 'so called' politically correct who have a habit of spilling their guts in disarray all over the place.

His theories however were soundly debunked by a teenage schoolgirl a couple of years back, who surprisingly didn't get much press about it. I have the article somewhere.

The polar icecap this year has heaps of ice on it, so much that one hairy armpit mob changed the amount on their website at midnight one dark night recently, but, they got sprung didn't they. They had lopped off 500,000 sq kilometres.

[ShyTorque]

The RAF Puma HC1 had a limit (IIRC) of 20 minutes in blowing or falling snow.

Prior to the fitting of polyvalent intakes, snow would accumulate on the fairing between the engine intakes in forward flight. When it slid off, it would go sideways into one of the intakes and had the potential to cause a flameout.

[[email protected]]

TET - I'm with you on this one - the 'global warmers' data about Antarctica was misleading at best and downright dishonest at worst. The only area where ice is reducing in the whole of Antarctica is on the ice shelf that they concentrate exclusively on, conveniently ignoring the remaining 80% of the continent where the ice is increasing.

Another 'inconvenient truth' is that the earth was warmer in the Middle Ages than it is now so they chopped that data off their temperature graphs giving the 'hockey stick' display that appears to show a steady increase in global temperatures.

Strangely the term 'global warming' has lost favour and is now being replaced by 'climate change' by the scaremongers - it's still cobblers though:)

[Jackboot]

Just put my 44 away after a very nice local jolly in the snow. 5 inches on the ground and light snow falling.

I have never done it before so took the precaution of hovering a few inches off the pad just to see what I might expect on the approach.

No drama, lots of fun despite a backbreaking hour shovelling snow first.

Well worth the effort - the scenery was just stunning.

JB

[albatross]

http://i37.photobucket.com/albums/e68/midcanada/HeliSki212Resize.jpg

I think we should ask this guy - he seems to have it in hand.

And if all else fails.
http://i37.photobucket.com/albums/e68/midcanada/jetmanuals-1.jpg

Have fun in the snow.

[Backward Blade]

Albatross, that is just an awsome reality based picture. I myself have done much the same albeit in different machines. Oh the challenges of VFR winter work! If that was you, nice job.

Fly Safe

BWB

[albatross]

Not me but it sure is a nice job by someone.:(

I think it is an Alpine Helicopters 212 on a Heli-Ski contract in Western Canada. Those guys know their way around the mountains and snow is practicaly required in the SOP I think. True professionals!:ok:

I can't remember who sent me the photo but it truely is a beautiful shot. The size was reduced for posting the full sized original is a work of art.:)

[signcutter]

I fly the AS350B3 with the sand filter and there is no limit in falling snow. I also fly the EC120 and the RFM says to avoid prolonged hovering in recirculating snow. The 120 has the barrier filter. Ive done the prolonged hovering thing and didnt have any issues. :cool:

[TunaSandwich]

Hi Albatross, well I could have sworn I'd read about the 212/412 falling snow limitation but now for the life of me can't find it so I must be confused with another type:rolleyes:. It would make sense that the Particle separators would do the job.

Anybody else remember anything about engine inlet snow deflectors for 212/412?

[albatross]

James Bay Daze:
Bell 47 with blade ice from flight of 2-3 minutes Ice fog -
http://i37.photobucket.com/albums/e68/midcanada/8c9fc28a.jpg


206's A + B - with particle separator needs snow deflectors.
206's A + B - with no particle separator needs reverse scoops.
206 L (C-20B)- particle separator had to be removed and reverse scoops installed.


I recall at least 2 206s with no particle separator and no scoops flaming out in heavy snow. := ( No not me )

205 - damned if I remember exactly - no scoops or deflectors - can't remember about anti-ice but we used to fly around in some very reduced vis in snow with no adverse effect however.

212 no scoops, no deflectors, no worry - durn things do not have inlet anti-icing - gotta love P+W - snow didn't hack the 90 deg turn down into the intake.

AS 350D carry on as normal
AS 350B I recall we had particle separators all year.

http://i37.photobucket.com/albums/e68/midcanada/d1f1a434.jpg

AS 355 straight intakes no Particle Separator - I think there was a limit if you had a particle separator installed but only flew TwinStars with particle separators installed in Africa where it did not snow much.

Long ago and far away now but that's how I recall the scenario.

[ramen noodles]

The prevelance of snow generally precludes icing, since the two are opposites on how water is suspended in the air - supercooled ice cannot be snow.

The reason for snow limits on helicopters is almost always the threat that gobs of snow afford to the engine's air supply or inlets. The typical problem is with plenum fed engines, were the inlet is typically a hole or slot in a cowling, and the engine is inside somewhere, with its heated bell mouth far away from the initial opening. The deep pockets invite snow to collect where it can be partially warmed and then slog its way into the inlet.
Cures for snow ingestion usually involve shields or diverters that keep snow from forming near the plenum, or heating sections where the snow does for to melt it before it builds up. Flying a helo into snow when it is not approved is a very effective noise abatement scheme, once the engine(s) have quit.

Engines with exposed bell mouths or with heated inlet assemblies are virtually always immune to snow problems, since the ice tests for which the inlets are designed are far worse in heat requirements than the typical wet, heavy snow.

OT personal attack on crab@ deleted. :=

Senior Pilot
Rotorheads Moderator

[SASless]

Ramen,

I would suggest current science technology lacks the ability to accurately measure and quantify all of the data necessary to produce a scientific model that accurately forecasts future results as is required by scientific procedures for a model to be considered valid.

Even the IPCC in their Fourth Assessment (Section 8) point that out and call for more work to be done.

http://www.ipcc.ch/pdf/technical-papers/ccw/chapter8.pdf

Knowing Al Gore's amazing ability to conjure who images of grandeur for himself....as in claiming to have invented the Internet surely poses credibility problems for the man. Just as he relies upon James Hansen who works at the Goddard Institute of Space Studies (GISS) run by NASA. Hansen has been caught out using erroneous and false data in his models and has spurned the use of space based technology in his studies. That alone is an odd situation for NASA funded scientific studies. Is it the Satellite based sensors produce data that is contrary to his theories?

His models fail to accurately future temperatures which alone are enough to invalidate them based upon accepted scientific standards. Has any of his studies been given a legitimate Peer Review? Any of them? Just one even?

I do believe you are falling into the description of Warming Advocates that Roger Pielke, Jr. wrote of in his book "Honest Broker".

[AnFI]

:ok:http://z.hubpages.com/u/401675_f520.jpg

[Senior Pilot]

That's quite enough thread drift into global warming/cooling/climate change/Al Gore/etc. Nothing to do with Rotorheads, nor with "Flight limits in falling snow" :=

Unless you want this thread consigned to the doom and gloom of JetBlast? :hmm:

[[email protected]]

Ramen noodles - sorry to have missed your comments on me, I'm sure they were very informed and erudite - a bit like your knowledge of snow.

Snow can only form when there is an adequate supply of moisture (water vapour) that can condense into a water droplet and then freeze. The more water vapour there is, the bigger the snowflakes but there must also be freezing nuclei for the process to work. In the absence of the freezing nuclei, supercooled water droplets are formed and it is quite reasonable to have both SCD and snow, especially in the cloud from which the snow is falling.

Many icing limitations (ours included) specifically prohibit entry into cloud when it is snowing for exactly this reason.

At the moment in the UK much of the weather is mixed rain and snow (sleet in old money) falling from the same clouds so how can they be mutually exclusive?

BTW what exactly is supercooled ice?:ugh:

[Aser]

Many icing limitations (ours included) specifically prohibit entry into cloud when it is snowing for exactly this reason.


Now, on the icing topic, what do you think about the generic icing limit "flight into known icing conditions is prohibited" ?

You can enter a cloud in freezing conditions but may or may not get icing on the helicopter, you will never know about the ice until you are inside the cloud.
As I understand you need to avoid that 'below 0C' cloud as far as possible or enter it only if you have enough altitude below in case you encounter icing.

regards
Aser

[ramen noodles]

crab,
The removed sections dealt with your introduction of politics to this thread, and they were (rightly) removed by Senior Pilot as being a bit too rough.

The simple fact is that in many of hours of snow and icing flight, and in the qualification of several helos in snow (the reason why I entered this thread, having experienced at least one engine failure in a prototype due to snow ingestion), I have never seen Ice where there is snow. And BTW, sleet is not snow, unless you decided to change the definition. The boundary between the two forms of precip is usually a temperature change, in my experience, where the temp goes close to zero C and sleet/freezing rain are present. Once moisture makes snow, it does not make ice. The change from sleet to snow can take place in as little as 5 miles of airspace, but I repeat, where there is snow, there is not ice.

Supercooled ice comes in Bourbon, btw.

acer, I certainly agree with you. "Known" would seem to allow one to fly in clouds where no reports of ice exist, but that is a sucker hole. In terms of flight planning, cold clouds mean the reasonable probability of "knowing" there will be ice, period. The cure is simple. Get a helo with blade anti-ice!

However, flight in snow virtually never results in icing, unless the temperature is nearer freezing where you can cross the line between snow and sleet/freezing rain.

[Matthew Parsons]

"flight into known icing conditions" is not the same as "flight into known icing". I think the difference is obvious.

[MightyGem]

Ramen, in the UK sleet is a mixture of rain and snow. In other countries, ie the US/Canada, is is ice pellets.

Sleet - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Sleet)

[[email protected]]

Ramen - snow is an ice crystal so the SCD can evaporate onto the freezing nuclei (Bergeron-Findeisen process) or freeze on impact with a cold airframe. Equally the snowflakes can melt as they fall and again freeze on contact with a cold airframe.

Blade anti-ice only protects the blades and will not protect the rest of the airframe from SCD.

[AAKEE]

Icing conditions: Moist in the air thats colder than zero degree celcius. Clouds, fog or mist can give icing. Depends from time 2 time how much water its contains. Mist usually dont give noticeble icing if the visibility is more then 1km. Freezing rain gives a lot of icing of course.

Ice pellets or snow grain is freezing rain that already has frozen, and is a evidence of icing conditions higher up...usually seen when U have a occluded front above you. Ice pellets/snow grain dont give you ice but it tells you that icing conditions is above you and that it is not unlikely to find freezing rain in any direction, it´ll depend on the occluded front and the temperature variation the front(´s) produces.

Snow: when it snows the snow effectively takes away moist. If you have 1000ft cloudbase and it starts to snow heavily, the cloud dissolves cause the falling snow 'eats' all the small water drops. Heavvy snow takes the clud base away and give you vertical visability instead...in most cases lot higher VV than the cloud base was.

I fly military helis 'on the artic cirlce', never seen the ice warning system even move the needle in snow.

Heavy (wet) snow in about zero degree celcius or above can, as many said before, can form lumps that comes loose and into a engine and make a flame out. This would be tha main reason for restrictions to fly in heavy snow.

*) All above would be the normal. Off course there´s allways exceptions. Being too sure that the normal only occurs probably makes you die when you find out that there is 'exceptions that cornfirmes the rules' :bored:

[[email protected]]

the cloud dissolves cause the falling snow 'eats' all the small water drops

That is the Bergeron-Findeisen process working -the Saturation Vapour Pressure is different over ice and water at the same temperature so the water droplet evaporates and sublimes onto the ice crystal. So therefore the SCDs and the snowflakes must exist at the same time ne c'est pas?

[407 too]

If I may be so bold, both crab and ramen are correct, it just depends where you are flying.

If you are VFR a couple hundred feet AGL, in falling snow, clear of cloud, you will not get icing. It's just snow in clear air.

If you are IFR in cloud that is in the process of making snow, then I agree with Crab, you may get icing.

I would also like to make a distinction in the SCD size. It is microscopic when FORMING snow (attaching to nuclei)

The SCD size that is the worry in aviation can be almost as big as a raindrop.

Both SCD, with great differences in affect.