From: nlappos@bellsouth.nospam.net
Subject: Re: Scary snow experience
Date: 14 May 2000
Newsgroups: rec.aviation.rotorcraft

In article <391E0AA1.FDBCEC96@worldnet.att.net>, DJS@worldnet.att.net wrote:
>Had one of those experiences today that was both magnificent and
>terrifying.  It had to do with landing on snow.  Now I've done this
>countless times but today was completely different.  I was landing in
>the crater at Mt. St. Helens working on a feature story for the 20th
>anniversary of the eruption.  The fact there were some goofy winds
>didn't help but the real problem was trying to figure where to land in
>the featureless landscape.  The floor of the crater's about 5700' and
>the lava dome is around 800 feet higher.  Right now it's all pretty much
>covered in snow which runs from the floor up the sides.  After a couple
>of fly-bys, we decided to try to set down near some rocks sticking our
>of the snow.  I made my approach to them and once I was hovering, it
>didn't look too level so I moved around losing sight of the rocks.  Now,
>all I see is white.  I could have been 1 foot or 50 feet above the
>snow....I just couldn't tell.  No one else on board could either.  As I
>attempted to turn around to face the opening of the horseshoe shaped
>crater.  I caught a skid on the snow.  I thought I was at least five
>feet above the ground. The ship rocked to the left, but I was able to
>catch it, pull up and face out of the area.  Thank God for the 407's
>power as we had no problem flying out even with four on board and a
>bunch of gear.  Flew out of the crater gathered my thoughts and
>re-entered making my approach to an area about a hundred feet lower
>where the snow had melted.  No problem after that.  I had never
>experienced that kind of disorientation before and my thoughts flashed
>immediately to the three TEMSCO ships that flew into the ground in
>Alaska.  The overall experience, though, was breathtaking.  I hope I can
>land there when the snow's all gone...maybe on the lava dome itself (as
>others have done in good summer weather).  Anyone have any suggestions
>or experiences with snow disorientation?  I learned a valuable lesson
>today.
>
>Dann

Dann,
I flew at the Ice Spray rig that the NRC ran in Ottawa, which gave me similar
experiences.  The rig put out a cloud of steam, ice and snow that I had to
immerse the rotor in, while facing the spray tower and rig, which are made of
rather unforgiving steel.  The rig is in a bowl about 100Meters in diameter,
and with a berm about 3 meters high at the perimeter.

In the desired low wind conditions, the steam and ice blended into the snow on
the ground, and I had literally nothing to look at.  I found (after 3 or so
hasty exits up and backwards, while glued to the attitude indicator) that
several orange boards placed in the snow where my chin window kept good clear
visibility were very helpful, similar to the rocks you found.  After that, the
job was easier, but still somewhat nerve-racking.  I flew about 10 hours
hovering that way in the next week, and developed a healthy respect for
white-out, and a crick in my neck from staring down while hovering.

I had a chance to practice dust problems (brown-out) in Yuma, with about 15
hours of hover to qualify an engine filter in dust.  There, I also found the
chin window to be my only friend, along with the comfort of having enough
power to simply drive straight up if all else failed.  Every now and then you
see the films of that flying on the tube, with a Blackhawk entering an
enormous ball of orange dust and settling in to land.

I almost lost a Cobra in Vietnam that way, with no power and no options, and
no chin window.  Luckily, I landed with little sideward speed, and after one
big lean on one skid (I couldn't even tell you which way!) we settled down
with a thump, and I got to tell the story.

The rules seem to be:

1) Don't do it unless you have to.  Anticipate lose dust/snow as a problem and
avoid if possible.  Never plan to hover at lower than a height of  1 to 1.5
times disk diameter in the stuff, you must land or not but don't get stuck in
between.  Also, think thru your escape plan, which is probably an instrument
take off, with lots of climb.  You will leave the cloud easily at a height of
about 1.5 times disk diameter.

2) Look for the cloud to form behind the helo as you make a running hover at
about 12 to 15 knots of airspeed.  The cloud will be behind you at 15, and
will find you as you slow to about 8 knots or less.  Still air is your enemy,
since you will have to enter the cloud as you slow down.

3) Pick a landing attitude and spot the touchdown carefully as you slow and as
you anticipate the cloud sweeping up to you from behind.  At 8 to 10 knots and
slowing down, just commit to the landing, so there is no need to make any
control movements as you touch and simultaneously lose vis.  You should not
make a smooth touchdown, this wastes time with the wheels just touching.
Plant it positively before the cloud finds you.  Slight nose up, tail first,
and down collective.

4) The cloud will find you when you are on the ground, maybe rolling at 5
knots or so,.  Just neutralize the controls and wait with flat pitch, the
cloud will die in about 10 seconds.

Turn the vent blower off before you do this or you will polish everyone's
teeth with the dust you blow into the cabin and cockpit.

These are Black Hawk and S-76 rules, probably useful for others, but I am
reluctant to recommend running landings with skids, so maybe some other poster
can help with skidded helo rules.

Nick