Author Topic: Ski ops and questions  (Read 1004 times)

RCarter

Ski ops and questions
« on: February 25, 2019, 01:11:02 AM »
So I finally got my LW-3600 skis installed.  Actually got them installed two or more weeks ago, but I got the flu and didn't really get a chance to fly them other than a quick test until this weekend.

Well weather this weekend was excellent and I put a couple of hours on the ski plane.  Did a few stop and goes on a public ski strip, but it was mostly smooth ice with a few inches of snow on top.  Nothing all that different form normal wheels.  From there I went off to some lakes and landed on moderately groomed runways and in fresh untracked snow.  Both were a bundle of fun!  Super super fun to land, turn 20 degrees and take off again, then overfly the tracks to see exactly where you touched down, stopped and then broke ground again.  Today was a total blast.

However, ground handling on skis was troubling.  It seems that on both the lightly packed/groomed (snow machine tacks) and on the untracked snow the tailwheel wanted to turn sideways and stay there while taxiing.  On the groomed stuff it took a prodigious amount of power to taxi and while I didn't look at anything it felt and behaved as though the tail ski was perpendicular to direction of travel and was behaving like a boat anchor.  At one point I felt the ski straighten out for 50 or so feet and it taxied relatively well.  Then, independent of control inputs it decided to turn perpendicular again and stay that way.  It must be terrible for the airframe to have that much drag and stress going on at the A-frame, yoke, and a-frame mount.  In soft snow I was able to power out of it and fly away, in wet heavy snow it would be a disaster.  After a few very distressing and concerning attempts I decided to use the tail-wheel lock.  Worked well for straight taxis, but how do I turn?  I cant unlock the tail wheel for fear of the ski going sideways again and never straightening out.


I have heard rumors of this happening to others with the LW-3600 tail ski, but only rumors.  Those who have flown the LW-3600 skis, was this an issue for you?  How did you resolve it?  What did you to do turn in snow if you cant unlock the tail wheel?

Look forward to hearing some good thoughts and tricks.  The skis are a blast so far, performance seems good when all three skis are pointing the same direction, and they are great insurance when flying over lots of snowy stuff.  But what are the helio specific tricks for when I am on the ground?

Thanks,


Russell

Louis

Re: Ski ops and questions
« Reply #1 on: February 25, 2019, 04:27:47 AM »
A photo of you installation would help.  A photo of you tail ski.  To be able to see the angle.

You dont have any bungees on the tail skis ?

Louis

RCarter

Re: Ski ops and questions
« Reply #2 on: February 25, 2019, 10:52:45 AM »
It is a Landis tail ski, and the Landis drawings and stc do not include any check cable or bungee for the little ski. 

I will stop at the hangar on the way home and snap a photo or two. 

Louis

Re: Ski ops and questions
« Reply #3 on: February 25, 2019, 02:11:39 PM »
We have one Helio here with a tailski Landis.  We did put some bungee on this one because it was doing sideways.  The tailski that we have have a lot of surface in front of the wheel.  So it does want to catch snow and turn sideways .  For whatever reason, it then keep sideways instead of turning 180 rearward.  The bungees helps.

The angle is very important.  Not enough, and it will turn sideways when touching snow. 

Another trick, used on the Pilatus ski, is a fin at the rear of the ski.  At least it will realign itself in the air and be able to relock it.

On some tailski on my big 800, i had put a second wheel at the back of the ski.  So it would realign itself when touching snow.

However you mentioned that yours is able to behave correctly with the tailwheel lock.  ( We have very limited success with tailwheel lock, breaking them too often ) then don't change anything and use it with your tailwheel lock.  Want to turn ?  Push up the stab at full power.  You have penetration skis, so your brakes are working to help you turn.

On skis, a radius of 200 feet to turn 180 degrees is often a minimum.  Sometimes, it can be four times that.  If you need to turn inside a smaller path, unlock the tailski, turn, realign yourself, and if the tailski is still sideway, stop the engine, go out and straighten it.  Relock. Restart.  An Helio is not a Cub, it does ask for more energy from the pilot to operate it on skis.
And don't do what we all have done:  taxi toward the bank of the river-lake, approach it that way and park it close to the bank, pointing at it.  When ready to go away, then we are stuck without a way to turn it.  I know a lot of ski pilot, and they all did that mistake.  Only once, however. 

You have to shovel down to the ice the two main ski to be able to turn the plane on it's wheels without breaking your landing gear.  Trying to turn the plane by the tail with a skidoo or many helper, when the skis are still on the snow, is a perfect way to crack your landing gear.  They are not made for torsional force. 

After we have done the mistake once, we approach the bank almost parallel to it, so we have an exit angle.

Louis
« Last Edit: February 25, 2019, 02:18:14 PM by Louis »

Louis

Re: Ski ops and questions
« Reply #4 on: February 25, 2019, 02:22:26 PM »
The pilatus ski with a fin at the back, and a lot of skis area behind the wheel instead of front of the wheel ( like on Helio and other )  So it straighten it self in the air, and don't have too much tendency to go sideways when touching a skidoo track

With that, you can manage without bungees


Louis

Re: Ski ops and questions
« Reply #5 on: February 25, 2019, 02:27:29 PM »
One of my Helio when i was leaving the bungee unattached.  It would turn sideways in the air.  Grrrrrrrrrr


Louis

Re: Ski ops and questions
« Reply #6 on: February 25, 2019, 02:29:39 PM »
Don't forget when you want to turn to remove flaps, and push the stab full forward.

Louis

Doug Johnson 1

Re: Ski ops and questions
« Reply #7 on: February 25, 2019, 07:43:45 PM »
link to previous post on C-GBYA http://flyhelio.com/smf/index.php?topic=920.0

And here's one on tail ski rigging  http://flyhelio.com/smf/index.php?topic=1447.msg6653#msg6653

There are more if you do a search for skis
« Last Edit: February 25, 2019, 07:49:56 PM by Doug Johnson 1 »

RCarter

Re: Ski ops and questions
« Reply #8 on: February 26, 2019, 01:09:37 AM »
Had to work late today, so no picture today.  Tomorrow! 

Louis thanks for the thoughts.  I will continue to use the tail-wheel lock I just don't like relying on it for fear of it breaking.  Was hoping for another option.  You did mention changing the angle of ski so the tail drags lower helping to center it.  That is an easy adjustment and it crossed my mind on Sunday evening when I was scratching my head looking at things.

I didn't try raising the flaps when turning to help lift the tail.  Does that just allow more propwash to contact the tail and lighten it, whereas with flaps down they block prop wash?  Sounds like a good idea I wil certainly try it next time I am out.

Thanks again for the suggestons.  I will start with the easy ones and work up from there!

RCarter

Re: Ski ops and questions
« Reply #9 on: February 26, 2019, 09:04:40 PM »
Made it out of the office on time today.  Here are some pictures of the set up. First thought it so follow Louis's advice and increase the angle of the ski with the ground.  Hopefully that helps the tail catch sooner and keep it straight.  Another thought, was to use some UHMW and extend the tail of the ski till it contacts the ground. The theory being that there is too much ski in front of the pivot point, and for stability there needs to be more ski behind the pivot point than there is in front of it, similar in theory to a bogey wheel extended out behind the ski.

Further thoughts?


Louis

Re: Ski ops and questions
« Reply #10 on: February 26, 2019, 09:49:40 PM »
The angle is perfect and near maximum.

We could discuss clutch and spring.  Vs the rudder.  A lot of Helio have 185 spring.  Too flimsy.  You push the rudder to have some control of the direction of the tailwheel- ski, and then the clutch opens.  Bingo, you loose control on the tailwheel-ski. 

We did put beef-up direction springs once and it did miracle for crosswind taxiing on wheels.  The next winter, we saw it was also helping a lot on skis.

You mentioned tailwheel lock to keep the skis aligned.  We can also use the rudder to align the ski straight or with direction.  But we have a small margin since the clutch disengage at some small angle.  We do need strong springs to be able to control the tailwheel-ski with the rudder.  And well adjusted.  And keep the rudder within certain deflection angle so the clutch does not open.  With means to loose some rudder deflection because we need to keep the rudder in the deflection the clutch will stay close.

Louis





« Last Edit: February 27, 2019, 07:04:51 AM by Louis »

Louis

Re: Ski ops and questions
« Reply #11 on: February 27, 2019, 07:11:06 AM »
Anything that will keep the ski straight would be better than touching the snow and have the ski going sideways.  Bungees, strong springs and not using the rudder to the point the clutch opens, aerodynamic fin, more contact at the back of the ski to the ground.

If you let it go sideways in the snow, it is just a matter of time you will ripoff something.

Louis