Ground wind to tip

18 posts in this topic

Posted

Does anybody have any idea how much wind directly abeam that it would take to tip over a 500 lb empty Avid or KF if not tied down?  Sure, one would use appropriate aileron/elevator while taxiing with a headwind or tailwind component, but I'm talking about the case where the wind is directly abeam.  There's got to be quite an experience base out there...

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Posted

It most likely will fly at 30 mph. So head on a 30 mph wind would lift it. From that one can calculate approx. what wind speed would tip it.  Amazing that some are tied down with cinder blocks weighing 50 or so pounds when the wing will lift approx. 950 lbs.

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Posted

On my Catalina I see about 37 Mph stall....which means that at 37 Mph head on steady wind I will land with zero ground speed (cool thing to do), anything above, you're in a bad spot as you will go backwards on touch down. I believe your avid is safe sitting on the ground at any wind velocity below your stall speed. It will produce maximum lift with winds coming head on. When the wind is coming sideways, it will always try to weathervane into the wind. 

If you tie it down obviously the wind can be higher and you're still safe.

This is what I think from what I have experienced.....but have been wrong before..

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Posted (edited)

I don't like to leave mine NOT tied down.  Some areas I have gone to are known for high winds.  Super cool thing about avids and kitfoxes.  If the winds are really bad you can fold the wings and she wont fly or flip.  

Anything much more that a 25 MPH direct cross wind and you might think about having someone help walk it in by holding the strut. Your going to be using lots of brake to keep it from weather vanning too.

 

Edited by akflyer
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Posted (edited)

Yup, Leni, you correctly got my intent.  My real concern, living in the windy gorge, is taxiing, then having to turn into or off of the wind, a maneuver which momentarily places you perpendicular to the wind.  There is no wind component passing over the wing chordwise, so no lift in the traditional sense, but with a dihedraled high wing, there's a chance it could lift up  Once that wing starts lifting up, there's nothing one can do to stop it until the opposite tip hits the tarmac.  Of course, one could get out, go to the windward side, and try to walk it through.

If nobody has any data here, I may just go to my windy airport (just today gusting to 29kts), loosely tie one wing down, orient that wing upwind, get out my handheld wind meter, and wait for a gust.  At least this way I can bound the problem.

So, it's about 25 mph?  No offense, but I will feel more comfy if I validate.  Your gear is wider than my stock gear, and I think you said your bird weighs roughly 100 lbs more than mine.  Sort of a moot question in retrospect!

Edited by Turbo
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Posted

When I was learning to fly my 600 LB mkiv, my instructor who was used to much heavier winds in the larger planes he had flown said we should go out and do some wind practice.  He was a very experienced pilot and instructor but had virtually no time in very light aircraft. The wind was less on average, but gusting to about 30. It was down one of the runways which is why I do not think he was concerned about flying that day even though I was still training for my PPL. Anyway, I was taxiing my little plane with him in the right seat using all of the "tricks" with aileron and elevator. A side gust came up and lifted one wing and tire off the ground high enough to freak my beginner ass out, but fortunately not high enough for the opposite wing to hit the ground. We both put our tails between our legs and got it back to the hangar safely and did not fly that day. This was in a tricycle gear configuration Avid.

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Posted

I use the Kleenex test. Hold a Kleenex out and drop it, if it doesn't land on your feet, tie it down!

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Posted

With a passenger you have a better chance of avoiding disaster as one can get out and walk the windward tip thru the ground turn.  Alone, it's a much scarier (sketchier) situation.  Alternatively one could just sit still in a less dangerous orientation  to the wind, and beg for help over the CTAF!  Still, it's best if you know the limits.  I suppose the critical scenario is taxiing to the tiedowns or hangar after landing, so it's the ground turn away from the wind.  Ostensibly one wouldn't even try flying if the gusts were too high, so turning into the wind is not it,  although the same criterion would apply. Thanks, Chris for that harrowing annecdotal account.  

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Posted

So here's another wrinkle.  The airport's anemometer is likely on the corner of a rooftop, or a tower, and not down where our wings are while taxiing, and where the wind is likely somewhat less.  So there's a "calibration" issue here, or at least some kind of safety factor, say 5-10 kts.  Now the uncertainty is significant vs. the value of the item of interest.  Uggh!

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Posted

The plane will handle 25kts cross wind just fine much more than that I get a little uneasy taxiing back to the hanger but we get a lot of wind here 8 months of the year so you get used to it if you want to fly year around.  Start with some lighter stuff and work your way up.  The important thing is if you need to land and the wind is blowing 25+ the plane will handle it.  Just as well get used to it if you live in the Gorge.  If it's blowing the spray off the swells, go wind surfing instead!

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Posted

and if its blowing 25 knots just land into next to the hangar.  The ground roll will be next to nothing.  

:BC:

 

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Posted

This is a tough one.. A few times in my life I arrived at my destination, low on fuel and high winds.... ONe time I landed and absolutely could not turn the plane, IN fact the gust were occasionally picking up one wing or the other off the ground. I thought I was going to lose the plane... I took off and did like Leni said. I came around and landed with a big hangar about 100 feet in front of me and taxied up 4 ft from the hangar with tail in the air.I landed across the runways at a 45 degree angle in about 25 feet.. .This was in a Super CUb at Black Rapids Glacier in INterior Alaska south of  Delta Junction, AK....I have seen planes picked up and blow over backwards just after the pilot got out. Less weight, high wind. 

IF flying local you have to decide before you take off. IF the wind is close to your marginal limit better to be on the ground then up in the air wishing you were on the ground....

I have flown the kitfox 4 in 20 gusting to 30 mph but that is pushing it... you start to get that pit in your stomach that you are on the verge of losing control so that is about too much wind...

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Posted

So... Just helicopter taxi to the tiedown and land!  But seriously guys, 25 kts is a lot of wind.  Of course a typical installation has the airport's anemometer 30 to 33 ft up!  25 kts reported is likely less on the ground, at wing level.

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Posted

My last (I hope) very bad experience.

Morning 6th May 2019, airport Piestany (LZPP) Slovakia, RWY concrete, standard international airport (rather small). I was departing after Festival of Aviation 2019 cancelled on Sunday due to bad weather and we had to leave airport due to forced end of event, no place in hangars and expected weather getting worse.

My plane is low wing taildragger Bristell TDO, Rotax engine, 780 lbs Empty, about 1100 lbs actual TOW. Wind steady 25 kts, gusting 30 kts headwind for T/O (means exact crosswind for taxi to RWY). I successfully used all the tricks as was mentioned above till the RWY shoulder ... just turning to the T/O direction RWY 01 and then gust 36 kts reported from TWR lifted my right wing and immediately all plane from ground. Fortunately I applied full power at the same time when lift started and didn't hit ground again, taking off across the RWY01 diagonally ... very bad experience. And good luck in the same time.

I've landed about 1 hour later at the airport 80 NM far to east in moderate weather conditions, still rainy but no extreme wind. There were some damages of the planes parked and tied down at the airport later the same day due to bad stormy weather (i.e Trojan),

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Posted (edited)

Does anybody have a provision to tie the stick forward for such conditions?  I'm thinking this might allow one to get out with the plane facing the wind, then walk the windward wing thru the turn to downwind.  Prop stopped, of course.  Most likely you wouldn't be able to muster the leverage for that direction change though...?  Provision to lock either side's brake could make this possible, perhaps.

Just a thought, maybe a bad one.

Edited by Turbo

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Posted

Jenki,

That is one heck of a story! Nice piece of flying on your part to decisively pour on the throttle and make the airplane fly! 

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Posted

Short hijack here...  One of my favorite books written by an Alaska flying warden back in the 70s and 80s.  Great stories in here and this topic reminds me of one where he was holed up in a shack with crazy winds... the (supercub?) was actually flying in the tiedown ropes!  Read the book to see the rest of the story when they decided to fly it out!

And BTW my favorite story is Chapter 18!  Just about died laughing!

"From a Bush Wing: Notes of an Alaska Wildlife Trooper" by Stephen Santiago Reynolds.

Start reading it for free: http://a.co/gN3RM7k

 

 

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Posted

I agree with Nick.  Nice, decisive flying Jenki!  One nice feature of the Avids is their ability to essentially levitate when power is added!

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