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