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Old Sep 24, 2009, 02:08 PM
If it can-it will!
cliffhanger's Avatar
Gower South Wales UK
Joined May 2007
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How best to land on slope away mountain top?

Couple of weeks ago I backpacked up one of the local Brecon Beacons in Wales. Quite a trek but the views and the lift from the top at 800 m (2600') were fantastic.

Flew the Prodij in~25mph winds but landing was a problem.

As can be see in the pic. the back of the mountain slopes away considerably, and even flying back several hundred yards the rotor was still wicked.

In the end I dumped as best I could- luckily the top is boggy grass!

The very top edge of the slope is a bit rocky and the edge so sharp, that maybe trying to land coming along the slope top is not that feasible.

Any advice from flyers with similar l.z's? (I'm hoping to go back up again early next week)
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Old Sep 24, 2009, 03:43 PM
I love living near the Bwlch!!
clayts75's Avatar
United Kingdom, Wales, Bridgend
Joined Aug 2009
175 Posts
One possibility would be to come in VERY low on the front side and fly straight up the slope, trying to judge the total loss of momentum for a soft plop at the top of the slope on your toes. So far, I have only done the above with foam
Cheers
Clayton
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Old Sep 24, 2009, 04:15 PM
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Daemon's Avatar
Lakewood, Colorado
Joined Aug 2002
28,712 Posts
You almost never want to come "straight" up the front. If you misjudge,
it stalls below you, or over your head, and the plane is hosed. The trick is to
dive deep down the front and come up at a 30 degree angle off perpendicular
so that if you misjudge it'll turn and you can go around again. Instead of just
hoping that you intersect the lip at the right moment, you change the approach
angle to intersect it at the time when the momentum is lowest.
In the case of the above pictured slope, there's no reason you
have to land close to you. If you come up at an angle and burn off
the last of your speed at the edge of the lip 10-20 yards away,
then just let it dump over the edge and drop on top wherever it happens.

The biggest problem I see most people have is they just don't fly low
enough in the front to burn off all the necessary energy on the return
and they don't immediately dive back down the front when they
know they've missed the approach so they have to start over
with same or even more energy than before.
If you come up at an angle, you can just keep going around, diving
lower each time, until the timing is right. You may have to dive several
hundred feet down the front. You may find that doing 2-3 really tight
horizontal turns will help to burn off enough energy.

Otherwise I'd work on figuring out how to manage the rotor.
Sometimes flying crosswise through the rotor works better than
coming straight in from behind where it often gets a tailwind right
at the worst moment. If you're crosswise to it, you can correct
for sudden induced rolls much quicker, and you may even be able
to soar it in for an angled approach similar to the frontside
approach. Practice with foam.

ian
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Old Sep 24, 2009, 04:18 PM
Mike R. I find sink.
West Covina, California
Joined Aug 2004
395 Posts
Parker Mountain in California is a knife edge ridge with nowhere nice to land on top. Whever I fly there, I come in as slow as possible from behind the slope, skim over the top of the slope, and softly plant it into the grass on the front of the slope.

That being said, rotor is variable. Find the spot behind the slope with the least amount of rotor and make your approach from there. Aim for grass.

*edit* All this ^^^^ is assuming you have flaps. Otherwise it's the bleed off speed in front of the slope thing.
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Old Sep 24, 2009, 04:51 PM
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KurtMc's Avatar
Sacramento, CA
Joined Sep 2003
1,154 Posts
You might try landing it like a harrier (I gotta practice this trick)

Here' what I mean in this video at about 1:10.

Dynamic 80 @ Mars Hill (NEW) (2 min 10 sec)
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Old Sep 24, 2009, 07:18 PM
Flagstaff, AZ
dawsonh's Avatar
USA, AZ, Flagstaff
Joined Mar 2003
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Cliff:

What a beautiful site! You seem to have quite a few.

Too bad you couldn't haul a Le Fish up there... she slows down so nicely. It would be perfect to experiment with the landing. Maybe you need to build a packable version.

My flying site at Mt Elden has a similar problem... huge steep front side and sloping away LZ... huge rotor... especially in stronger winds. If I go deep I am often at the mercy of wild recirculating air flows.

I often find that the best place to land is a few yards back from the lip. You site looks very smooth... I bet the air flow is pretty laminar and horizontal. I like to burn off speed as Ian's suggests and make a mostly cross wind approach from the front/below. I control the crabbing angle (with rudder) so I drift up to the top/lip with little forward speed and let her drop in. If you have the 4th axis thing going try some spoilers while making the approach (to help kill some lift) and a bit of flap to "stop" and soften the landing.

Good luck. Shoot video.

Dawson
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Old Sep 24, 2009, 07:28 PM
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I fly at a place with a similar problem. The LZ is very steep, but it's the only grassy spot. Add in a wingeron/pitcheron with no brakes and it gets interesting..

I fly down the face, and fly a full 360 degree circle as far below me as I can see comfortably, then fly up the face at an angle. Depending on how much energy I have remaining, I can stretch the final turn (or not) to get to the LZ.

If I come up short, I just bail out and fly back into the lift. If I'm withing the speed range I can land at, I bank and fly it onto the ground and slide the remaining speed off. Sort of a cross-contour/crosswind final.

Have you ever DS'd that hill? Looks awesome.
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Old Sep 24, 2009, 09:02 PM
Just Toss It !!!
MATIN's Avatar
United States, CA, San Diego
Joined May 2004
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Looks to me like it needs a Cajon style landing.

Matin
does it with his eyes closed......from fear!
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Last edited by MATIN; Sep 25, 2009 at 07:17 AM.
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Old Sep 25, 2009, 09:29 AM
If it can-it will!
cliffhanger's Avatar
Gower South Wales UK
Joined May 2007
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Thanks for the suggestions - looks like Iíll have to try the dive down low and crab up the slope a few times to judge a plop and drop method.
Done that a few times on my coastal slopes, but the lift on the top of this ridge is phenomenal. I launched the Prodij with my usual settings for ~20 mph wind and the thing just went straight up a hundred feet or more!

This was the first time I'd been here- the hike up taking just over one and a half hours.

Dawson- yep thereís some good slopiní in these parts. When the Anglo Saxons invaded Britain they pushed the indigenous Celtic peoples to the more mountainous areas, which are now Scotland, Wales and Western Cornwall.
Fifteen hundred years on little did they know that they gave us the best places to throw off toy planes!!
Couple more pics. included showing the views from the 802 metre trig point to whet your appetite- wheníre ya cominí over??
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Old Sep 25, 2009, 09:55 AM
Not so fast....
Boulder, Colorado
Joined Apr 2005
518 Posts
Good grief, that is a totally epic slope.
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Old Sep 25, 2009, 10:05 AM
"Still Crashing since 1960"
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Pierre, SD, USA
Joined Dec 2001
1,112 Posts
Quote:
Originally Posted by cliffhanger
Thanks for the suggestions - looks like Iíll have to try the dive down low and crab up the slope a few times to judge a plop and drop method.
Done that a few times on my coastal slopes, but the lift on the top of this ridge is phenomenal. I launched the Prodij with my usual settings for ~20 mph wind and the thing just went straight up a hundred feet or more!

This was the first time I'd been here- the hike up taking just over one and a half hours.

Dawson- yep thereís some good slopiní in these parts. When the Anglo Saxons invaded Britain they pushed the indigenous Celtic peoples to the more mountainous areas, which are now Scotland, Wales and Western Cornwall.
Fifteen hundred years on little did they know that they gave us the best places to throw off toy planes!!
Couple more pics. included showing the views from the 802 metre trig point to whet your appetite- wheníre ya cominí over??
WOW that is fantastic! What a hill and view!
I would come over to fly NOW, But (and there always is one) I am to broke to pay attention

Them hills are what dreams are made of.

nut
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Old Sep 25, 2009, 05:44 PM
Twisted and Confused
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Joined May 2003
4,337 Posts
Have you walked back further from the lip to see what the rotor is like? Back say 40m+?? I flew at a slope not too different (though not quite as high) and I found that an approach at speed a bit further back than normal got me out of most of the rough stuff and into something a little smoother, but I did need more speed than normal to get through the ground effect.

i.e. follow Ian's approach, but instead of making the final leg 10m back from the slope, come in at higher speed to make the cross wind leg 30-50m behind the lip, turn to final approach and fly it down into the ground to stop it running out of airspeed in the ground effect and nose diving in from 10m up which happened to me a couple of times and I saw it quite a few times.

Of course you only really get one shot at it (unless you're really honking in which case a bail out to the front is easy) but as long as you have enough forward speed to overcome any ground effect you should be fine if the rotor isn't too bad.

Steve
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Old Sep 25, 2009, 05:57 PM
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Daemon's Avatar
Lakewood, Colorado
Joined Aug 2002
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If the lift is as big on that slope as I suspect it is, then I'll bet
the rotor extends a lot more than 50m back behind the lip.
I'd guess more like 200m.

We've got slope nearby with a 180 meter draw and the top 12-15m
are vertical. The top is dead flat. I've gone 158mph in a frontside dive there.
To land crunchies we get the plane up high on the front, and then start
walking back away from the lip for 50-70 yards, until it becomes
tough to fly the plane that far away, then we make a slow high
downwind approach 50 meters above the ground, and above the rotor
while increasing our walking pace away from the lip so that by
the time the plane is some 250 meters downwind of the lip, can dive it
down behind the rotor and bring it in skimming the ground at a good clip
and stuff it into the grass. If you come in too slow, the rotor
will still catch it down low from behind and flip it over.

Attached are a couple diagrams I made of this approach a couple years ago.

His frontside is bigger. The big difference is that our
frontside lip is vertical and made of rough lava rock, so the plop and drop
method isn't an option. He's got a rounded lip and smooth area to
drop into.

ian
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Old Sep 25, 2009, 08:43 PM
Just Toss It !!!
MATIN's Avatar
United States, CA, San Diego
Joined May 2004
6,022 Posts
Ah!!!.....Now we are showing off our CAD skillz??!!!

Matin
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Old Sep 25, 2009, 08:57 PM
Registered User
Daemon's Avatar
Lakewood, Colorado
Joined Aug 2002
28,712 Posts
... or hand scribbles in paint program.. sure.

ian
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