Rachet tie down question

Domenick said:
The problem with ratchets is knowing when to stop. You can crank them down hard enough to bend something.
Personally, I don't and wouldn't use ratchets. I use retired climbing ropes.
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MauleSkinner said:
hurricanes are wimpy. A good midwestern thunderstorm generated 96 knots a few days ago, and a number of years ago 110 knots is what took the hangar apart that my Maule was in. Fortunately the part I was in (and the plow truck we were hiding under) stayed together.
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"Wimpy" hurricane Michael has entered the chat.
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I was parked in Cody, WY once and we had a good blow. It caused the legs of one of my claws and some of the "nails" to bend (but didn't give way). To their credit, the claw people replaced all the parts that were damaged. I was just using the ropes that came with it.
 
455 Bravo Uniform said:
How much lift can your plane generate? If it’s a 1,500 airplane, it can lift itself off and then some. So three 500 lb straps will not be enough. ...
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The wings are designed to handle much positive lift. They are NOT designed to handle nearly as much negative lift which is what the tie-downs generate.
In other terms, your fuselage hangs from the wings and the wings are designed to support it. The wings are not designed to handle as much force in other direction.

Gary Ward said:
They used chains at the flight school that were left a little loose.
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Dan Thomas said:
Chains have been known to wreck the airplane. The airplane starts jerking around, and comes up suddenly against the chain as the slack is suddenly gone. Torn-out tiedown rings, damaged spars and/or struts. Not good at all.
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The few times I was forced to use chains because the tie-downs were for a much larger aircraft, I used as little of the chain as possible by snapping my terminal carabiner into the chain and using as much rope as usual.

At Pemerton, BC, Regional Airport, I encountered something unique to my experience. A heavy steel cable was run lengthwise across a grass field anchored to the ground at numerous points. You tied down to the cable. I always wondered how the cable was anchored and how the anchors would behave if a dozen planes all started bucking.
 
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Clip4 said:
Whats wrong with quality 1/2” nylon rope with a breaking strength >5,000#? The rope will break before the knots fail.

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I'm old-school, and I won't use anything except nylon rope. There's a reason all of the most popular tie-down kits come with it! Storm Force, The Claw, Fly-Ties, TacAero
 
Eric Pauley said:
Yup. What are the tie down eyelets rated for? I doubt they’re rated to hold the entirety of the max aircraft flight load.
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exactly!
Could you even hang an aircraft upside down at EMPTY weight from the rafters of the hangar from those tiedown points, without damaging something?
(in that case, would it be called a hanger?)
 
Dan Thomas said:
Chains have been known to wreck the airplane. The airplane starts jerking around, and comes up suddenly against the chain as the slack is suddenly gone. Torn-out tiedown rings, damaged spars and/or struts. Not good at all.
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I do wonder if having a small section of chain at the bottom would help function a bit like the chain lead on an anchor. Helps absorb some of the shock from lighter gusts from disturbing the anchor point (especially when using an auger-style tie down in grass). The upper section of rope would absorb any shock loads to the tie-down eye on the wings when the chain was fully stretched in heavy winds.
 
Brad W said:
exactly!
Could you even hang an aircraft upside down at EMPTY weight from the rafters of the hangar from those tiedown points, without damaging something?
(in that case, would it be called a hanger?)
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Imagine you have infinite-load tie-downs. A strong storm hits and the load (which I think we've concluded the aircraft has no coherent rating for) damages the airframe invisibly. You now have a damaged plane but don't know it.

In contrast, the person with the 1000lb tie downs had them snap and got a total loss check from their insurance. Who came out ahead?
 
JScarry said:
Tiedown ropes capable of resisting a pull of approximately 3,000 pounds should be used . Manila ropes should be inspected periodically for mildew and rot. Nylon or dacron tiedown ropes are preferred over manila rapes .
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Half inch braided nylon rope has a breaking strength of over 5,000 lbs. Nylon rope has some stretch, which can help reduce damage. Chains and ratchet straps are overkill.
 
Eric Pauley said:
Imagine you have infinite-load tie-downs. A strong storm hits and the load (which I think we've concluded the aircraft has no coherent rating for) damages the airframe invisibly. You now have a damaged plane but don't know it.

In contrast, the person with the 1000lb tie downs had them snap and got a total loss check from their insurance. Who came out ahead?
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What “invisible damage” would occur?
 
Brad W said:
seems to me that the likelihood that the angle of attack to reach full lift is pretty much zero. I've always figured that tying down is at least in large part to keep the thing stable... so it doesn't start rocking and swaying, lifting a wing or a tail, etc...
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With a Tri-cycle gear likely true. I actually raise the tail of my glider when tying it down mostly for just that reason.

Brian
 
Eric Pauley said:
Yup. What are the tie down eyelets rated for? I doubt they’re rated to hold the entirety of the max aircraft flight load.
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Cessna uses an AN eyebolt with a 5/16" diameter shank. Its strength would be roughly the same as an AN5 bolt, which is made of alloy steel with a strength of 125ksi. That 5/16" bolt therefore has a strength of around 9500 pounds, in tension. Two them? 19,000 pounds. I think they would hold just fine.

That stuff is made of a ductile nickel steel, usually. It will bend quite a bit without cracking. I saw this numerous times when students banged the tail on the runway and bent the tail tie-down bolt way back. 1/4" shank. One student managed to break one, once.

Those strut eyebolts are actually part of the aircraft's strength. They are in place of the uppermost rivets in the strut holding the aluminum fork in the strut. They are loaded in shear in flight.

They are this strong:

1722881947851.png

Look closely at the top ends of the struts. They're bent, and that's why the wings are pulled down. There is likely plenty of damage to the wing spars, too. Those tiedown rings were that strong.

The tail tiedown failed there, and the strong wind pushed the airplane forward, causing the tiedown tensions to go way up. Serious wind.
 
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Eric Pauley said:
I don't want to speculate too much since I'm a statistician and not an engineer, but if I had to guess I'd say hard landings.
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How many hard landingS in a one-time event, and were the proper inspections completed prior to the next flight?
 
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donjohnston said:
"Wimpy" hurricane Michael has entered the chat.
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got to disagree with you sir, page field saw gusts of over 170kts during ian. that was before the wind equipment blew away.

as to the original post, i have experience in this. during ian my pa28 was tied down on the ramp at KFMY. it had two ratchet straps and a rope on each tiedown. only one of the ratchet straps failed. they were all the six to a pack straps from HF. however, all three tie down mounts failed, including the tail skid on the PA28 it ripped the structure apart. they ropes and straps were laying on the ground intact, still hooked to hooked to the failed rings. the plane ended up about 90 feet away after doing a full roll.
 
Clip4 said:
Whats wrong with quality 1/2” nylon rope with a breaking strength >5,000#? The rope will break before the knots fail.
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In my experience that hard part is knowing if the rope is "quality" or not. Here's exactly that, a rope failing before a knot.

 
Lowflynjack said:
I'm old-school, and I won't use anything except nylon rope. There's a reason all of the most popular tie-down kits come with it! Storm Force, The Claw, Fly-Ties, TacAero
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I feel very confident that the reason is that it's cheap. :)
 
rwellner98 said:
I feel very confident that the reason is that it's cheap. :)
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LOL, could be part if it, but I've seen the ratchet break on straps. I saw a 152 flipped over in high winds and the nylon rope was intact, but the concrete ripped out of the ground.
 
When you start seeing 100+ mph winds, be it in a hurricane, thunderstorm, or whatever, pretty good odds that SOMETHING is going to fail. Maybe the rope, maybe the anchor, maybe the tiedown, maybe the aircraft structure ... but something is going to give. Not to mention other stuff starts flying.

Here is the result of a glancing blow from a Cat I that passed 50 miles away. Fortunately the shade hangar fell away from the aircraft.

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Ed Haywood said:
When you start seeing 100+ mph winds, be it in a hurricane, thunderstorm, or whatever, pretty good odds that SOMETHING is going to fail. Maybe the rope, maybe the anchor, maybe the tiedown, maybe the aircraft structure ... but something is going to give. Not to mention other stuff starts flying.

Here is the result of a glancing blow from a Cat I that passed 50 miles away. Fortunately the shade hangar fell away from the aircraft.

View attachment 132143
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Yup, exactly.

This is from a microburst in Mesa last year. The tie downs of the Piper in the lower right corner held the plane to the ground, but the wind was still strong enough to bend the outer wings up. There is a pic of a Cessna with both wings outboard of the tie downs bent up, but try as I might, I can’t find it.

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Dan Thomas said:
Cessna uses an AN eyebolt with a 5/16" diameter shank. Its strength would be roughly the same as an AN5 bolt, which is made of alloy steel with a strength of 125ksi. That 5/16" bolt therefore has a strength of around 9500 pounds, in tension. Two them? 19,000 pounds. I think they would hold just fine.

That stuff is made of a ductile nickel steel, usually. It will bend quite a bit without cracking. I saw this numerous times when students banged the tail on the runway and bent the tail tie-down bolt way back. 1/4" shank. One student managed to break one, once.

Those strut eyebolts are actually part of the aircraft's strength. They are in place of the uppermost rivets in the strut holding the aluminum fork in the strut. They are loaded in shear in flight.

They are this strong:

View attachment 132133

Look closely at the top ends of the struts. They're bent, and that's why the wings are pulled down. There is likely plenty of damage to the wing spars, too. Those tiedown rings were that strong.

The tail tiedown failed there, and the strong wind pushed the airplane forward, causing the tiedown tensions to go way up. Serious wind.
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I once had a guy who bought eye bolts from the hardware store to install in the strut's of a 172 that was being rebuilt that was bought from an insurance salvage company. I was helping him a little for the experience. I said no way. He says that he would weld the eye shut to make them stronger. Said originals were too expensive. I bet they were removed at the salvage yard because of that?
That was the last day I saw that plane. I am not even sure if it ever flew again?
 
WDD said:
www.sportys.com

All-Weather Tie Down Kits

These modern all-weather tie-downs are easy to use; with one quick pull the rope is taut.
www.sportys.com www.sportys.com

Carabiners won't slip off, and its quick pull ratchet isn't going to over tighten. Your wing will bend before these break.
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I have these on my pa-28; been tied down outside in (admittedly occasionally) windy Las Vegas. Year 5 and no problems so far - although the high UV has probably degraded their strength enough that I'll be buying another set after this summer.
 
Lowflynjack said:
LOL, could be part if it, but I've seen the ratchet break on straps. I saw a 152 flipped over in high winds and the nylon rope was intact, but the concrete ripped out of the ground.
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Yeah, for sure. If one if going to pick ratchets, gotta pick ones with ratchet mechanisms that are strong enough for the task. I've accumulated probably a couple dozen over the years here at the farm that I'm very confident are strong enough to hold a tarp on whatever I'm trying to keep dry under a tarp, but would break the first time the plane wobbled in a moderate wind.
 
Clip4 said:
Ever hear of West Marine?
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Nope. But google told me. My point is more about the fact that rope (and straps, in fairness) start degrade the first time they are exposed to weather, sun or tied in a knot. The storm that took my plane was very strong, but it's also true that I haven't trusted ropes provided by an FBO since.
 
rwellner98 said:
Nope. But google told me. My point is more about the fact that rope (and straps, in fairness) start degrade the first time they are exposed to weather, sun or tied in a knot. The storm that took my plane was very strong, but it's also true that I haven't trusted ropes provided by an FBO since.
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Yep. I used to do a lot of rock climbing as a younger guy, where great attention is paid to rope strength for obvious reasons. Several things deteriorate Nylon, with age at the top of the list. FBO ropes are fine for a sunny Sunday afternoon or overnight tiedown, but for long term storage I would provide my own and replace every few years. Marine stores sell rope rated to a recognized standard, since line strength is also a BFD in that world.
 
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