Flying in snow
 

Dear All

What experiences does anyone have flying in snow/freezing conditions?

What I really would like to know are the DO's and DONTs obviously things like visibility,recirculation white out in the hover are some problems which can be expanded on but my main concern is are there temperatures and snow types you avoid flying in.
I have done some flying in snow but would appreciate anyones experiences (good and bad)so that hopefully I can learn some more.

Obviously flight into known icing is a definite no go.

I hope someone can enlighten me !!!!!

Regards
hoverbover

PS
Most of my flying is in the UK.

hoverbover - We don't know what you fly so it's a little tricky giving any advice. I can only advise that if you haven't been given any specific training in this field then don't do it - It's a very quick way to get dead......

PurplePitot
Its a NOTAR.
I understand your wise words, but its difficult to get specific training in the UK as it doesn't snow that much! Any ideas??

Regards
hoverbover

Surely your flight manual will tell you the limits?
If you aren't famil with those, try these:

Do not fly in visible moisture below 0 degrees, is good karma for MOST civvy pilots. Due to the venturi effect at the engine intakes (Po) this drops further causing freezing and the engines could cut out!
The same for snow. Don't fly in snow below 0 degrees due to icing. Down to this is ok provided you MONITOR the "stickability"...i.e. if it is building fast and obscuring your view or building too much near the intake(s) then vacate the area. NORMALLY this only becomes a problem when the viz drops to <500m.
White out can wipe you out within seconds. IF you have to land in fresh snow, then adopt a zero / zero technique landing. This keeps you inside the snow vortices for the min amount of time. Don't practice Z/Z's for the first time in snow!!!!
Same goes for the takeoff.

Happy Christmas..


Edited due to some absolute b****cks I printed earlier!
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Thermal runaway.

[This message has been edited by Thomas coupling (edited 06 March 2001).]

TC
Please would you explain zero/zero.
Thanks

Zero airspeed / zero rate of descent...all coming together at the same time and place! It tends to be 'positive arrival' compared to pussy footing about in the hover prior to touchdown. Take off: pull take off pwr and rotate immediately...in that order!!

Problems: If you don't know what the surface is like (depth etc) then because of the positive landing, there is a risk you may sink thru the light surface and damage the undercarriage. If you try and lighten the touchdown by pulling some power...you'll white out!
Take off: If you've been on the frozen deck for too long, you may stick to it sufficiently to overtemp an engine trying to break free!!

Fun and games....


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Thermal runaway.

Thanks TC.

Hoverbover,

I had a recent experience in snow / icing conditions last weekend which nearly cost me an R22.

Following a training flight with a student i departed the airfield to return home. Due to poor visabilty (1km) / snow showers i decided to land the aircraft in a field and wait for the snow showers to clear.

The snow did not clear and i abandoned the helicopter. The ground was very soft and boggy.

I returned to the helicopter the following morning with a student, the conditions clear blue sky minus 5 degrees prefect flying conditions. Whilst walking to the aircraft i was explaining the dangers of dymanic rollover.

We arrived at the aircraft and as i suspected the aircraft skids were frozen to the ground. We stamped the ground down both sides of the skids to free the aircraft from the ground. We preceeded with the normal preflight check / start up. We are now at full power and ready to lift, the aircraft became light on its skids and i inputed left and right yaw pedals to slide the aircraft from side to side to free the landing gear from the ground. I made a special point of yawing the aircraft to free it from the ground having flown serveral weeks in the Swiss / French Alps and experinced this several times previously. We are now light on the skids and looking outside the student at the controls whist i followed through he continued raising the lever within a split second the aircraft lifted on the passenger side and possibly the front part of the landing gear to the pilots side. The aircraft almost went over i dumped the lever and shut down the aircraft. After exiting the aircraft it became apparent that whilst shuffling on the ground i had in fact shuffled the rear spade part of the landing gear under the very soft suface (Crisp and hard on the surface very soft below)preventing the aircraft from lifting.

Very close call. I will be extremely cautious in future

Any simular occurences?

You will find in the 520 manual ( plus other 500 variants ) you may fly in falling snow providing you have the following. No centre seat pax ( never been able to work this out or find anyone who knows - anyone enlighten me ? ); autorelight on and armed, I would suggest that anti ice is on as the temp will be below 5 degrees and you certainly have visible moisture.

Other points, as you will have cabin heat and anti ice on watch your TOT espically if you are heavy. TOT starts to rise the inlet may becoming blocked - unlikely but possible.

Heed everyone else's advice get someone to show you

What Notar do you fly in UK, presumably a 600 as there are no 520 in UK I think ???

I think no centre seat front passenger might be to keep C of G more rearward.500 has a problem in snow[especially wet snow] that it can build up on the top of the perspex then break off going through the compressor in a big chunk. A lot of weight in front would givea more nose down attitude.I personally have had this happen and on one occasion over a large densely wooded area had 3 flameouts in ten minutes,relit each time by the auto relight.Problem exacerbated by the fact that in these conditions of heavy wet snow speed is back around 60 knots because of the vis and also you will be at a low altitude for the same reason.
I would guess that the no centre seat pax rule is an attempt by the manufacturer to address this problem.Its a while since I flew a 500 and I don't recall any similar restriction was in the 500D manual, but the problem was well known to those of us flying it in winter. I'm only guessing the reason its there for a 520.

With a passenger in the centre seat, you may not be able to reach and open the auxiliary air inlet, should the particle sep become blocked with ice/snow. I don't believe it has anything to do with CofG. I've had it flame-out & relight while in straight and level while slinging. The a/c was no more nosedown than in normal flight.

If you do want to fly in falling snow, get ahold of a proper snow deflector. That way there's no flameout problems.

Make absolute sure that your skids are clear, and free from the ground before you start up. With an R22 take hold of the T/R gearbox, and pull down. It should go down with reasonable ease. Our engineer said that the force needed to lift the skids will not harm the tailboom or it's attachment. The same goes for the 500 series. Pull down on the tail, until both skids squat, then lift it back up.

If you don't have experience in snow that is deeper than ankle deep, I recommend you get instruction (try a holiday to Canada, or Switzerland where they get snow)!!! It is very easy to put the a/c into dynamic rollover if you aren't very careful. If you've shut down, get out and remove the snow from around the skids, to check to make sure the skids are clear. It's best if you can give yourself something to use as a reference. A stake, or clearing a spot right down to the ground. Be easy on the controls, and once clear of the surface, get out of the snowball quickly.

There is a good saying that may help. "If in doubt, don't".

knhxyy

There was a thread on skids frozen back in December, it might be worth a read.

In brief though, lower tail (as above) or even use a pole as a lever under the skids, anything to ensure that the skids are not stuck before a start.

Also beware that latent heat from the skids may melt ice/snow on landing, only to refreeze in minutes. Never trust that ice or snow even if you have landed for two minutes
and not shut down....

Doesnt Canadian Helicopters have a mountain flying flight school at Penticton. Just wondering if they teach flying in these types of conditions.

To all

Many thanks for the info, keep it coming, all the warnings are taken on board.And hopefully others will learn as much as possible, like me.

To TC

As you say the RFM allows flight in snow but their are no limits on temperatures etc.(except for the operation of the anti ice below +5 c with visible moisture, personnaly any time the temp is lower than +5 c I use the anti ice anyway visible moisture or not)
Many thanks for your sound advice, You learn something every day (I had always guessed that 0to+3 C would be the worse conditions for snow accreation and it would get less sticky the colder it got under 0C.)

To Hughes500

Thanks for the info, on the subject of aircraft could be !!!!!! But there is a 520 Notar in the UK (on the N reg at the moment)
and all advice is gratefully received

Thanks to EVERYONE and keep the info coming, and please don't worry I have no desire to fly in snow without the proper training(anybody got any ideas on who/where)but would like to be prepared.

Regards
hoverbover

Randy G, can't be anything to do with filter by pass its located by your right ear on HS,C and D models not sure on Notars. I like the C of G idea though or perhaps is there a danger of centre seat pax knocking off autorelight with a foot. The switch on all machines is about 2" off the floor ???

Nice topic this one espically as I had 2" of snow at the weekend on Dartmoor - ha ha I hear you say.
Cheers

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Randy G has a point. When it happened to me the day I had multiple failures,I was only doing about 60 knots [vis about half a mile]so there wouldn't have been a big nose down attitude.That day was probably an ideal combination of temperature, moisture etc to get that heavy wet and sticky snow.We had resisted snow deflectors up until then as the TOT increase from them restricted our ability to move drills at the altitudes required. Used them after that if it even looked like snow.

My point was more that Flight Manuals these days are written by lawyers and they come up with all kinds of protective measures when a known weakness exists.When I can't think of an obvious reason for something that's what my suspicious mind concludes.

This was lifted from the FAA preliminary accident data report.

1996 BELL 406 HELICOPTER DROPPED OFF SKIERS, RETURNING TO
REPOSITION, SET HELICOPTER DOWN, SNOW CAVED, HELICOPTER ROLLED,
TAILBOOM OFF, ROTOR BLADE DAMAGED, JACKSON, WY


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The Cat

The no centre seat occupant restriction in falling snow on the Hughes 500 is because the original engine relight switch box was located lower on the console, and was difficult to reach with the centre seat occupied. All of our 500's (I'm talking in the 80's) had the relight moved to the upper right of the panel, and the centre seat restriction was lifted. It has nothing to do with C of G or the Filter Bypass door.

It is difficult to nail down blanket rules for flight in snow, as each helicopter and situation are unique. Not sure I can go along with the 'zero/zero' technique. This may work for very light snow conditions at airports but is not appropriate for use in heavier snow or unprepared sites, and can lead to more trouble than its worth.

One method commonly used for take-off in snow is to start to apply a little power until the snow begins to fly, retaining reference with the ground. Continue to apply power without going airborne until the snow has diminished to the point where a good reference is available. Lift the aircraft into a low hover, keeping your reference visual, then climb to a high hover and depart over the snowball. The main thing is to keep some reference available at all times.

For landing, plan your approach to a spot with some form of reference available. This can be the side of a building, a small tree, a fuel drum, etc. Bring the aircraft into a high hover, while maintaining reference with your spot, and allowing the downwash to clear the snow. Slowly lower the aircraft to the landing site as the clearing snow permits visual contact to be maintained.

Thomas Coupling...I have to take exception with several of your points. You say "Do not fly in visible moisture below +5 degrees, is good karma for MOST civvy helos. Due to the venturi effect at the engine intakes (Po) this drops to just above freezing and the engines could cut out!" This is absolute rubbish.

You also say "This time don't fly in snow below 0 degrees due to icing." Again, rubbish.

And...."If you've been on the frozen deck for too long, you may stick to it sufficiently to overtemp an engine trying to break free!!" Over temp in winter? What exactly do you fly?

Flight in snow, when properly equipped is as safe as flight in rain. There are places in the world after all where flight in heavy snow conditions are a daily occurance, and operations are conducted in a safe and efficient manner. Mr Coupling...If you don't know what you're talking about, please don't impart your dangerous level of inexperience on others.



[This message has been edited by Tiercel (edited 06 March 2001).]

And of course in winter weather: DON't place your tongue on any part of the cold frozen heli, it might stick to it, and you will look silly. :)

(Well ... I had to add somethin ...)

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Marc

[This message has been edited by RW-1 (edited 06 March 2001).]

To Tiercel

All great advice, what about in flight conditions to avoid like certain temperatures etc.(i know its an open ended queston but any advice is greatly appreciated)

To Hughes500

Must have been pretty at the weekend, wasn't too far away myself but it was dark.

Again I hope others are learning as much from this thread as me,

Regards
hoverbover

My personal favourite for snow landings is to come to high hover, with escapes, and blow as much of the lose snow away.

zero speed landings are all very well, but as pointed out before you have no idea what is below the snow.

Unless there is a tactical reason for not blowing the snow I think that a high hover is a top plan. IMHO of course.

Greetings from the Great White North. Some good points brought up so far (and some REALLY bad ones), and if I may add a few, hopefully good ones, of my own......

When flying in snow.....
-Slow down.

-Beware of the fact that visual cues can be lost, even when visibility doesn't seem too bad, i.e. cloudy day when flying over lakes or vast expanses of unbroken snowcover. Approaches to snow covered areas in poor light conditions should always be made to a point or line of reference, which must be kept in sight at all times, as tiercel said in the landing / takeoff brief.

-When approaching a valley crossing or downslope in poor wx, slow down and plan your escape route/180º turn early to avoid shooting yourself into a whiteout condition. Also make sure your split-as$ed 180 doesn't take you over more unbroken white, this time at 60º of bank.

Most of this stuff is just plain common sense.

Accumulation is a different thing, and let's not confuse snow with ice. The RFM will provide restrictions regarding flight in moisture / snow and may offer relief when certain kits are installed (i.e. snow baffles / deflectors, relights, etc). Also, many operators in snowy climes develop and certify their own kits for their particular needs. When operating in these environments, it is imperative that the aircraft be properly equipped, as Randy G said.

Wet snow can accumulate on the fuselage, but in reality, the visibilities associated with heavy wet snow are usually so poor that prolonged flight is not an option anyway. If the vis is not reduced such as to slow you down, there likely won't be much in the way of accumulation. This build-up does not in any way affect the rotor or tail rotor, but may pose a problem for unprotected intakes, unheated pitot static systems etc.

Colder (< approx -5º) snow poses little threat in most PROPERLY EQUIPPED aircraft during reasonable flight conditions (vis > ½ mile), that meaning having the appropriate snow deflectors or what have you for that type. Again, there may be an RFM restriction or specified minimum vis.

Another thing to be careful of when working in a cold environment is the ability of blowing snow to infest every cavity in the aircraft. If the helicopter has been left outside for a prolonged period of SBS, you may find the tailboom, transmission deck, or engine bay full of hard packed snow. This can not only cause problems when it melts (and refreezes), but may also have C/G implications.

I add my hat to the ring of supporters of the high hover approach and slow, planned, visual departures. As the previous post said, avoid the 'zero-zero' thing unless you REALLY know what your doing, OR, if you're on fire, getting shot at or making movies....


[This message has been edited by CTD (edited 06 March 2001).]

is there a common recommendation on how to remove frost or sticky snow from rotor blades? (other than waiting for it to melt)

If sticky wet snow or precip has melted then refrozen on your blades you have a problem,but the normal hoar frost/light icing associated with overnight parking outside on both main and tail rotors will burn off rapidly at 100% Nr and some pitch is pulled.

I've had to do that on medium Bells where it takes 100% torque to hover with a less than maximum load initially but after a few seconds, performance improves remarkably as the ice burns off.Sounds crazy,I know, but as long as there is no imbalance all blades will clean very rapidly.

Picking up ice in flight is different, especially on the tail rotor which,from my experience, often sheds ice unevenly causing imbalance and serious vibration.Picking up ice in flight on the main blades can appear to have little effect, but the buildup is usually on the slower sections of the blade and affects the autorotative sections.To be avoided obviously,especially in single engined machines.

Aside from the ice building up on rotors,the sheer weight of ice on the fuselage can be surprisingly high.

Tiercel,
I flew the 500D in the early 80's and had no restrictions on the centre seat because of the relight switch. Was this restriction in your Hughes Flight Manual or was it a directive from the Aviation Authority in your country?

I may be able to answer that (from a Canadian perspective at least, I'm not sure where Tiercel operated his).

I seem to remember it as a flight manual restriction, because I think I can still recall the temporary pages in the book. If memory serves, it resulted from an accident on the James Bay hydro development (around 1980?) where a 500 flamed out in falling snow and crashed. The investigation revealed the Auto Relight, which was located on the lower console between the passenger's feet was not turned on. The investigators also concluded that the Auto Relight could not be seen by the pilot if the center seat was occupied, and therefore the pilot could easily miss it if it were not on. The result was the restriction.

As a solution to the problem, most Canadian operators then relocated the Auto Relight to the outside of the instrument panel on the copilot's side, where the pilot could see it. If your 500 already had this or an equivalent mod applied, there would be no restriction. I think Tiecel may have his dates a little off, by the early eighties this would have already been done, I believe.

I haven't flown a 500 for 8 years, but that's how I remember it. Hope it sheds some light.

Tiercel: well where did you crawl from under?

You are quite correct in spotting my mistake regarding flight below +5 degrees in visible moisture,,,blah blah. It should have been 0 degrees. Sincere apologies to all for this.

Regarding the rest:

Last month a 6800hr russian ex mil EMS pilot killed himself doing a high hover approach to land. He cleared the lose snow from about 50' then descended and whilst doing so, shifted some more - lost vis references and struck the deck with a MRB. Good advice tiercel!

Engines overtemping whilst taking off: If the skids stick to the deck and you pull power to overcome the problem, depending on your a/c type and the amount of overcontrolling certain pilots may inflict on the controls one is in danger of overtorquing leading to an overtemp (it's happened, I've seen it) - dimbo...what other overtemp is there apart from me reading your drivel!

I learned my snow flying in Nova Scotia/Newfoundland and the Rockies military style...I suspect you've been reading about it or worse still teaching it without any quality experience....

I'm concerned that a newbie to the rotorhead forum feels that he has to respond with such venom. A shame really, I was beginning to appreciate this particular forum because of its more relaxed position on matters. Perhaps you've jumped across from another more agressive forum like: wannabees....! ;)

By all means question my contribution but blatant slagging only serves to dilute the purpose of this thread.

Go and have a drink on me.....with ice http://www.pprune.org/ubb/NonCGI/tongue.gif




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Thermal runaway.

Pac Rotors yes CHC does operate an advanced/mountain school in Penticton, B.C. Be a great place to go and learn some good techniques on flying in/around snow. Good skiing around there too. :)

There are arguments (for/against) for either technique high hover vs no hover. Some in heli-skiing use the no hover landing with great success. While myself and others have not had any problems with an approach to a hover to wait for the snow to clear.

I recommend cleaning all contaminants off of any critical surface before you start up. Unless you really know your a/c, you may not know when the contamination is gone. I won't gamble with peoples lives. It may be a pain in the butt to brush the snow/frost off the rotors, but it sure beats any of the alternatives. If you operate in an area where frost/snow is a problem, then use covers. They prevent rotors from developing frost, and snow won't freeze to the blades.

http://randyspics.tripod.ca/206winter2.jpg


You can see the blade covers on this 206, we also covered up the engine area and used an electric heater to keet the engine warm. Using the blade covers, I never had to clean frost off the blades.

Cheers

Randy_G

If you can't stand the heat ...

Then turn up the airconditioning !! :)

p.s. talk about irony, here I am downunda in the Land of Aus giving tips on flying in the snow. http://www.pprune.org/ubb/NonCGI/tongue.gif In case any of you don't think I know anything about winter flying, I have flown all over western Canada, and in the Cdn Arctic in the winter.

pity the helo above didn't have itty bitty little covers on the tail rotor blades too.
All dressed up and no snow to blow!!!

One further piece of advice. Despite all the problems your aircraft may have, the loss of visual cues close to the ground is what kills most people in these conditions, both during take-off and landing.

As well as external whiteout, beware of misting-up of the transparencies before and during take-off. Try to keep the doors open as long as possible while you are getting strapped in and started up, especially if you have been working hard to sweep off all that snow, free the skids etc. This will make sure any perspiration, heavy breathing etc (!) goes outside.

If you do get canopy misting make very sure you don't lift off until it is cleared; the last thing you want is your own self-induced IMC hover. Keep a soft cloth available to wipe the screen and use the screen demist if you have it.

In colder climates where the OAT gets lower than about minus five or so, canopy misting is likely to be less of a problem as the air is drier. Use of screen heat (or any inside heat) may not then be be a good idea as it may put snow contacting the airframe back into the sticky range causing build-up on the outside. Also, if you are carrying pax with snow on their clothing (skiers, soldiers, whatever) you don't want it to melt as it will make them wet which doesn't help them once they go back outside into the cold.

As always, get some instruction from someone who is used to the local conditions!

TC...I read my original post again, the one which seems to have offended you, then I read your reply and I stick by my original statement....."if you don't know what you're talking about......". I still don't get the overtemp though, seems to me the last thing you'd want to do if you were "stuck" in a helicopter would be to pull full power. Ever hear of dynamic rollover?

Randy G brings up a good point that some of the heli-ski pilots use the no-hover ldg technique, and I use it from time to time as well. To clarify my response to hoverbover's question for the benefit of Randy and others, these heliski guys are very high time mountain pilots, with heaps of experience flying in winter conditions. The person asking for advice in this forum has very little winter experience, and my response was tailored to that level.

BTW Thomas, to answer your off-handed comment about my lack of experience and having read about some of these things..... I'm a mid-time (just under 8K) ATPL who has spent most of his time in Western, Eastern and Arctic Canada, among other hot spots. And no, I do not currently share my lack of 'quality experience' with others on a professional basis.

Thomas stick to your guns, Tiercel, you are in error. I for one have flown in 1 type where engine anti-icing was required below +10 deg C and another that required engine anti-icing at +3 deg (in visibility <1000m due to moisture) both due to the temp drop in the engine intakes. Granted there are types which do not suffer as much, it is a product of the design of the air intake and such extras as FOD guards. (Remember P1 V1 T1 / P2 V2 T2 from your ATPL?)

Personally, I favour the zero/zero (no hover landing) technique and at least 1 reference. While I was doing supply trips in the antartic, if there was no suitable reference I used to use fire a flare (smoke if poss) into the snow, it gave me a reference and a good wind cue, very good if you are making an approach in a bowl where the surface wind could be 180 different from the 500' wind. (Why do chaps always want their stuff dropped halfway up a mountain in a bowl?)

BTW, 173mm icing in one sortie!!! look at http://www.gkn-whl.co.uk/eh101news/e...rrent/hot.html

To all

2 Days 31 Posts and counting,excellent info from everyone,keep it coming.

To TC and Tiercel
Please don't start fighting, you both have more experience than I will ever have, don't fall out over this pleeeeease!

Thanks to one and all,keep the info coming !!!!

regards
hoverbover
PS
One thought I have had, are the blades warmer(friction) or colder (wind chill) than OAT,when flying ?

Grey Area! Whooaaa laddie! You are correct in what you say, but read again.....I didn't for one second say that ANTI ICE wasn't required below anything...what the man said was "Do not fly in visible moisture below 0 degrees, is good karma for MOST civvy pilots. Due to the venturi effect at the engine intakes (Po) this drops further causing freezing and the engines could cut out!" That is what I responded to, the "do not fly". Anti ice is different, true.

As I said in my last post, I use the no hover technique as well, but wouldn't recommend it until one becomes very comfortable with the other aspects of winter flying, which hoverbover by his own admission appears not to have achieved yet.

HoverB, Blades will be warmer due to friction.

hover boy, wind chill only effects fleshy things like you and I.....

as far as the high hover versus zero zero, wouldn't it be better to lose visual reference (if inevitable) at ground level than in a high hover? how can you tell just how high that blowing snow will go?

Hover Bover...During flight operations the blades cannot physically get any colder than ambient, they will be slightly warmer due to friction. This will vary by type, tip speed and temperature.

‘Wind chill’ occurs when an object is cooled below ambient by the heat lost during the evaporation process, or ‘latent heat of vaporization’. So, unless the blades were sweating, they can’t be subject to wind chill! :) :)

Imlanphere: Not necessarily....to lose visual reference near ground level may not leave time to recover if you have a high closure rate, as you likely would in a no hover landing situation. Not good anywhere of course!

The high hover vs. no hover could be debated for ever. I use both up here in the Great White Wasteland, depending on the situation or loading. Both have their issues, and both must be used with caution and finess.

In the high hover method, the letdown must be smooth, slow and controlled, ALWAYS maintaining reference. This precludes its use when very heavy for some helicopters. The no hover method requires a precision approach, faith in what lies below, and a zero speed touchdown while staying ahead of your downwash. Not too bad in a 25 kt wind, but it can get very sporty on a calm day.
I personally believe it requires more skill and experience on the part of the pilot, and have to agree that it should be avoided, or at least practiced in a controlled environment, by folks who aren't winter current.

Thomas Coupling, I flew in all those places too. When were you in Newfoundland? Who were you with? From there?

[This message has been edited by CTD (edited 07 March 2001).]

To Hover Bover:

The only time snow is really a problem for take-off or landing is when it is newly fallen. After it has been on the ground for 3 or 4 days it usually doesn’t blow around much.
I prefer the techniques mentioned by Tiercel and CTD. When you arrive in a high hover ( 30 to 50 feet depending on snow and down-wash of aircraft) it takes a bit of patience to wait for the snow to clear , make sure you have good references when you're waiting. If its windy , with a lot of snow on the ground your reference for landing is sort of straight down out the side window; I would recommend practicing some landings using side window references for practice. You have to be sharp to do the no hover technique and it is certainly no something that I would use going into a night helipad.

There is one point that no one has mentioned and that is , after landing in deep snow you usually “pound it down ” i.e. pump the collective up and down until the skids reach the ground or the aircraft belly is resting on the snow. This prevents the gear from braking through the crust unexpectedly with the aircraft at ground idle. ( Canadian operators use bear paws on the back of the skids to keep the tail rotor clear .)

With regards to over-temping, I can’t comment on all aircraft but I know that if any aircraft that I’ve flown in the winter were to over-temp , I would bet that it couldn’t pass a power assurance check..

PS. Spend a winter season flying in Canada and all the snow mysteries will become clear.
IHL


[This message has been edited by IHL (edited 08 March 2001).]

There will always be disagreement and discussion among pilots about approach and landing techniques for snow,as well as mountain technique.Having read with interest all in this post I thought I'd add a bit more for the benefit of those seeking information.The experienced people on this forum have their own ideas and are unlikely to modify them much now.There is one thing here that hasn't really been mentioned and thats to use a method with which you are comfortable.

When I first went Heliskiing I was forced to do approaches in a way that my instructor and boss swore was the "Correct way".It may have been to him,but I was more comfortable using a different[more flexible]technique that I developed over time and I believe I was safer doing what I was comfortable with than operating an obviously legitimate way but made me uneasy.In my opinion,listen to all the suggestions in here,but be comfortable with whatever you adopt.

I have been taught both flat and steep approach to landing technique and several methods of landing in snow.All of them have their good and bad points so I usually adapted a technique dependant on the conditions at the time,ie knowing how to use any technique and knowing which one would be safest.Most of the time I didn't have the luxury of being able to enter a high hover due to weight and altitude,so no hover was the only option.So,for those of you wanting info,learn all the techniques because you may not have the option of choosing the one you want.

Having re-read one of my posts I would like to clarify one thing.My remark about burning off hoar frost by hovering applies in conditions of no precipitation.ie the aircraft sitting outside on a cold clear night.It burns off frost evenly and quickly,I've never had an imbalance.If somehow there is contaminate on the blades that affects lift you'll notice it with a power check and there'll be loss of lift and vibration.This remark was made more in the context of discussion between experienced people and I was unwise to suggest it be adopted by newcomers to winter flying.An intimate familiarity with the aircraft is essential and would probably only be felt by someone operating an aircraft professionally on a daily basis.Having said that,to remove/melt frozen precip off rotors is time consuming and must be meticulously done to avoid imbalance between the blades or else you'll have serious vibrations that will not go away.

Tiercel, I've now reset the eyes/brain and foot/mouth circuit breakers. Apologies.

Addition to ShyTorque's good pointers on misting...... if it gets reeeeeeeeal cold, the problem becomes frosting. Even though the air is dry, the surface temperature of the windows can be -30 or -40º. The moisture from all those heavy breathing pax sticks hard, and at those temperatures, without windshield heat, can take forever to get rid of. As ShyQ says, leave the doors open (Brrrr), or start before loading pax and run the heater/defrost.