Question - How much lift on a tied down RAA say 600kg aircraft with gusts or a storm.

[Old Guy]

We had some pretty strong winds last week in Melbourne - many large gum trees down, power outages etc. The media reported gusts of 124km/hr (~67 knots).

 

Our local airfield (Lilydale) has many GA aircraft on tiedowns (including a few ligher ones like C150's, Tomahawk etc), but no RAAus registered aircraft on tiedowns that I have ever noticed... even "cheap" Jabirus are all in (expensive-to-rent) hangers. I have seen a couple of older Jabiru J120's on tiedowns and covered up at Coldstream a few km's away, curious to know how they faired in the recent storms.

 

Has anyone had good experiences keeping RAAus registered aircraft outdoors in windy locales?

Reality bites eh. i fly a storch muster and had a very severe wind storm event when parked up at my home field overnight while i was away the aircraft was wheel chocked and tied down into wind. The pilots who were present at the time were not game to try and relocate her because of the conditions. On arrival next morning i found her standding on tippy toes with the landing gear legs at almost full extension as when flying, the chocks (one piece fwd and aft ) were to each side of the wheels which had lifted gradually up and inboard. While counting myself very lucky at the time. On reviewing what happened i am convinced that your assesment of the aircrafts attitude being held under the stall angle of attack is the real reason it survived without damage. Ps their were no other aircraft tied down at that time,

cheers Mick

 

I was weathered in January with bushfire smoke and then heavy rain. With flooding forcast my Jab 120 had to be parked on high ground in a exposed position. The flood did go through at about 5 feet but the aircraft was several feet above that.

I used 2 x pegs for the wing and tail points (star posts) in clay with a 30 degree spread using nylon ropes pulled taught. Brakes on full nose down trim.

2 storms went through over several days with continuous high winds and both had maximum recorded gusts gusts of 60+ knots. The aircraft was parked tail into the wind and did not move at all.

Much to my relief.

I had prepared myself for disaster but it all held tight.

[SGM]

I guess my assumption is that GA aircraft handle tiedowns better than RAAus lighter aircraft - for extended periods anyway

[Downunder]

Yes, they are heavier and have a higher wing loading generally.

I was parked amongst some RV's. My wings were rocking in the breeze and the RV's were dead still....

[RFguy]

I recall a lift destroyer that was round? section (about6") rubber Foam? or such and was tied along the top of each wing length wise. Also put gust locks on elevators and rudder. Nev

REMOVE BEFORE FLIGHT ?

 

I am taught to anchor the stick back with harness when aircraft is parked. Is that what you mean Nev? or some sort of pins at the control surface ?

[Jabiru7252]

I'm curious - why not put tail into wind and stick full forward when tying down? As for the force on the tie downs - gravity is pulling my plane against the ground at 3139.2N (that's 320kg x 9.81m/s^2). To get my plane off the ground the force on the tie downs would have to be equal to and opposite to gravitational force. (Actually, it would have to exceed gravitational force). Just for the record, gravitational force is the weakest of the four forces. But I guess falling out of the sky knowing that doesn't help one iota. Man, I can rabbit on...

[RFguy]

see my post #4 of this topic.... that force comes EASILY!

you need to consider the aircraft wing in aerofoil mode could become a high lift device....(the tailplane-elevator wont do much, its for flying balance)

OR you can consider the wind or fuselage as a flat plate wind cross section and it is like a simple kite......

 

The surface area of the wing is not insignificant. and at 50 m/s each square meter of wing is about 200kg !

so 10 square meters of wing flat (NOT operating as an aerofoil- just a piece of flat pate) can lift 2 tons.

Edited August 30, 2020 by RFguy

[Reynard]

interesting what a tied down plane can do while you’re sleeping.
 

https://www.facebook.com/reel/2413059642482637/?fs=e&fs=e

[facthunter]

There's a way of reducing that Lift by fixing a roll of something along the top surface of each wing. 2 struts have broken so both wing structures are suspect damage by twisting forces.  Nev

[Thruster88]

When this dust storm hit Narromine SAAA flyin in 2019 I was glad the thruster was tied tail into the wind.

 

[Blueadventures]

56 minutes ago, Thruster88 said:

When this dust storm hit Narromine SAAA flyin in 2019 I was glad the thruster was tied tail into the wind.

 

On the 26th November at Narromine this year the cable failed unfortunately damaging two gliders.  (Cable was likely overdue for replacement.)

Edited December 13, 2025 by Blueadventures

[Thruster88]

Hopefully the cables will be replaced and not just removed to reduce liability. 

[onetrack]

I don't understand why you wouldn't use 316 stainless in those cables. The corrosion levels there are horrendous.

[Blueadventures]

12 minutes ago, onetrack said:

I don't understand why you wouldn't use 316 stainless in those cables. The corrosion levels there are horrendous.

316 gives no indication of pending failure and if used would need to be replaced in a shorter time compared to gal steel rope; (sail boat rigging, inspection and replacement intervals is a good indication).

[Reynard]

Those cables may be over 80 years old ? May have been originally gal, but the gal has long gone.

 

316 is certainly susceptible to sudden failure ( usually chloride induced stress corrosion cracking) but Narromine certainly doesn’t have any marine influence, so I would think 316 would be fine.

[onetrack]

Quote

316 gives no indication of pending failure and if used would need to be replaced in a shorter time compared to gal steel rope; (sail boat rigging, inspection and replacement intervals is a good indication).

Blueadventures - Sorry, I have to disagree with you on the above point. Good quality 316 stainless steel with the specified levels of chrome and nickel content, is graded as high tensile, and its resistance to corrosion is excellent.

Steel wire rope must be correctly sized for the intended use, and properly treated when in use. Kinks, flattened wire strands and overload situations are the killer of all steel wire ropes.

 

Galvanised coatings are easily damaged and once damaged, corrosion of regular high tensile carbon steel wire starts rapidly, and continues unchecked. When the corrosion is deep in the cable strands, it is very hard to find.

I do have substantial steel wire rope experience, I started using it the day I left school, and have used it extensively for 60 years. I have never heard of stainless steel wire failing to give indication of impending failure.

The wire strands in SWR start to fracture independently and singly, and give adequate notice of failure, if heard or visually seen snapping - and total failure can be avoided if the load is released, and the SWR inspected accordingly to check for wire strand failure.

 

Unfortunately, there is a lot of Asian-manufactured stainless steel that fails to meet globally-agreed specifications, and the use of this sub-standard stainless steel, has been behind numerous product failures involving stainless steel products.

[tillmanr]

When I visited Narromine a number of times 5-10 years ago the tie down cables were at a glance repurposed old steel wire cables about 25mm diameter and rusty but nothing unusual at regional strips.

[facthunter]

Chains would be easier to check. That wire rope has been there as long as I can remember. Irrigation  areas CAN have more salt than the Beach.  Nev

[onetrack]

SWR needs a coating of lubricant/preservative to ensure it lasts, and performs properly. You can buy a sizeable range of spray or brush-on coatings/lubricants for SWR.

 

The coating protection prevents rusting and the lubricant penetrates the cable strands, and prevents internal friction between the strands, and therefore reduces wear on the strands.

[Blueadventures]

3 hours ago, onetrack said:

Blueadventures - Sorry, I have to disagree with you on the above point. Good quality 316 stainless steel with the specified levels of chrome and nickel content, is graded as high tensile, and its resistance to corrosion is excellent.

Steel wire rope must be correctly sized for the intended use, and properly treated when in use. Kinks, flattened wire strands and overload situations are the killer of all steel wire ropes.

 

Galvanised coatings are easily damaged and once damaged, corrosion of regular high tensile carbon steel wire starts rapidly, and continues unchecked. When the corrosion is deep in the cable strands, it is very hard to find.

I do have substantial steel wire rope experience, I started using it the day I left school, and have used it extensively for 60 years. I have never heard of stainless steel wire failing to give indication of impending failure.

The wire strands in SWR start to fracture independently and singly, and give adequate notice of failure, if heard or visually seen snapping - and total failure can be avoided if the load is released, and the SWR inspected accordingly to check for wire strand failure.

 

Unfortunately, there is a lot of Asian-manufactured stainless steel that fails to meet globally-agreed specifications, and the use of this sub-standard stainless steel, has been behind numerous product failures involving stainless steel products.

My poorly worded post was to mean steel the most cost effective by far and that s/s can have failure issues that are not visible.  Both will give a long in use life.  Cheers.

[facthunter]

 That set up at Narromine would be more affected by weather and age  than any other cause, I Doubt it would ever have been over stressed until weakened. How much Lift is Possible. ???  Easily calculated C/L  A o A Wind speed and wing area.  Easily 2-3 times the weight of the Plane I would suggest. As for stress on the cable, quite a few factors come into Play How straight it is when the cable becomes tensioned? How Jerky the Load is and how large  the Planes inertia when it's jumping about in the wind. A quantity in Proportion to it's Mass. Nev