Primarily for general aviation discussion, but other aviation topics are also welcome.
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By Flintstone
FLYER Club Member  FLYER Club Member
#1613196
cockney steve wrote:?... you can make or buy wing-covers that incorporate profiled foam strips to modify the profile. Racing-cars have long-used aerofoil "spoilers" to strongly push down and thus stick the vehicle very firmly to the deck.



Point of order Mr Chairman but those are two different things. The former is design to reduce lift, the latter to create it (albeit downward). You knew that though. :wink:




cockney steve wrote:So, you need the weight of about 6 persons to have any hope of restraining even a small machine. (around 1/2 a ton! )



Six?! Is that a number from the PAFOOMA* Scale? Pretty sure many of us will have experienced a (ahem) near-max-weight take off in a wheezy training aircraft. Those struggle to get airborne with a turning engine. :D





* Pluck A Figure Out Of My Aaarrrse.
MikeB, PeteSpencer liked this
#1613231
It has nothing to do with levers or where the weight is positioned.

The simple fact is that an aeroplane weighing ~ 1,700 lbs will start to lift off the ground when the air flow over the wings reaches about 65 knots. This is for a TB. Maybe a bit higher because the flaps are retracted.

Note that the 1,700 lbs was the basic empty weight. Given that the same aircraft will lift off when weighing 2,535 lbs (MAUW) and airspeed only needs to be a few knots faster, it's fairly easy to see that adding 120 lbs of ballast will not make any real difference at all. And ballast is all it is - you may as well put the extra weight inside the cabin for all the difference it makes. Tying it to the underside of the wings might make it look like the aircraft is being 'held' down, but all you've done really is add weight, which is why high wing aircraft usually take off perfectly happily with concrete-filled tyres hanging under the wings.

To actually prevent an aeroplane lifting off in a sustained wind that exceeds the airflow across the wings necessary for flight, you need equipment that can withstand the strain of a 1,700 + lb object attempting to move. Remembering the basic forces in flight, lift opposes weight, so for this object the lift force will be a minimum of 1,700 lbs. Your kit needs a breaking strain of more than 1,700lbs, which in practical terms means ground anchoring based on metal set in concrete. Even then, your straps/ropes will probably snap when exposed to such a sustained force, unless you've bought high-breaking strain line designed for sailing boats. Anything less than metal-in-concrete will be pulled out of the ground like it wasn't there.

While not many tie-down systems will withstand full-on attempted flight, what they are very good for is stopping the aeroplane bucking, tilting and being blown around in winds which are insufficient for causing flight but strong enough to cause it to roll, or tip, or come free of the chocks, or whatever.
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By flybymike
FLYER Club Member  FLYER Club Member
#1613237
I agree with all that in so far as it applies to the aircraft taking flight.

Leverage is however relevant in that as correctly stated in your last paragraph, a wind lift of considerably less than 1700lbs (or whatever) is all that’s needed to lift one wing and tip the bloody thing over or send it dancing around the apron, and once it’s upside down or stoved into the side of the hangar or an adjacent aircraft then that’s the show over, full stop.
Application of weight below the wing, as you correctly state will reduce this likelihood by requiring what for the sake of convenience I have referred to as a lever moment.
#1613245
Yes, if we are talking about a wind coming from sideways-on and getting under the wing, pushing up on the underside and making the aircraft move then weight applied at the tip will prevent that to a greater degree than weight applied near the root.

But that's nothing to do with lift or flight. That's just the wind pushing an object about.
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By imperialsam
FLYER Club Member  FLYER Club Member
#1613294
Thanks everyone for the replies. They’ve been very helpful.

What I’m taking away from this is that it’s sensible to use tie-downs if they’re available, but lack of them is not usually a reason to cancel a trip or find another airport, provided that the aircraft is chocked, controls are locked fully nose down, and that we’re not talking 50kt+ winds. This is assuming a TB-like aircraft. As people have pointed out, you might treat a Cub differently.

golfcharlie wrote:If you are obliged to park on hard standing with no tie-down points, take along a two or three 20-litre folding water carriers (camping kit). On arrival, fill with water and wheelbarrow to your parking position.


I think I understand the point. Even if 60kg is nowhere near enough to stop it taking flight in a 70kt headwind, it might just stop a gust from getting under a wing and breaking the aircraft out of the chocks - after which all bets are off. However, the chap at Bergerac already thinks I'm slightly odd for asking about tiedowns and grass parking. I don't know what he'd make of me if I emailed him again asking for 60 litres of water and a wheelbarrow. :D

holyflyer wrote:If you do wish to have a bit of grass to bang the claw into then I can recommend Perigueux (up the road from Bergerac).


Thanks for the suggestion. It actually looks slightly closer to where I’m going than Bergerac, and perhaps less hassle getting fuel than Bergerac when its Ryanairs and Flybes are around, so I’ll check it out.
Last edited by imperialsam on Wed May 23, 2018 6:33 pm, edited 1 time in total.
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By Rob L
#1613297
PB wrote:I've flown my Luscombe round Europe a fair bit in previous summers and decided to not wory about it.

I take three lengths of rope which I use to tie-down to installed anchors if available.

Failing that, I park tail to wind with the stick tied forwards, insert a couple of stout wooden chocks.and go and enjoy myself in la belle France. I've long since concluded that the portable tie-downs (screw, claw, etc.) will be next to useless if there realy is enough wind to tip a 400Kg aircraft over.


I have a different opinion, although your experience is yours. I parked my Taylorcraft (tied down) on the Scillies once in the late 80's, and the airport got hold of me to say there was air under my tyres. Ten burly fireman and I then relocated it to the lee of the tower. Winds were up to 50kt, steady.

What did you do to secure the rudder?

To be fair, mine's a rare case, but not tying a very light aircraft (like a Cub, Taylorcraft or Luscombe) down when you can (if going away) is leaving fortune to the wind :wink: .

Rob
#1613311
The chap at Bergerac is not responsible for your aircraft, so he can afford to think you are a bit 'funny'.

Come the insurance claim, it will look better for you if you took every reasonable and practical precaution. Insurers are not charities but in business to make money.
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By Flintstone
FLYER Club Member  FLYER Club Member
#1613367
Barcli wrote:Whats Vimto ??



Concentrated pish with eight tablespoons of sugar per can disguised as a health drink.



flybymike wrote:An amphibious Twin Pioneer ? :shock:


More a sort of very heavy kite really. :D


There were two at Coolangatta, Queensland when I was first a student and then instructor there in the 90’s. I have a whole 30 minutes logged in one, VH-AIS. it was either the one in the YooToob link below or its partner, can’t make out a registration in the video.


Flyin'Dutch' liked this
#1613374
Meanwhile back in Bergerac........

I have parked my aircraft at Bergerac with no tie downs for weeks at a time with absolutely no problems. You are more likely to be troubled by heat at that time of year. Having said that, Bergerac is a great airport and has excellent facilities, with car hire on site.

I, like yourself, used to worry about things like this when I started to take my aircraft on foreign trips. After a decade of doing it regularly you realise that generally things seem to work out positively and if things like tie downs are needed then they are usually provided, especially in France, where infrastructure is really good.

Bergerac and area is one of the best places for an holiday in France, I’m sure you will have a lovely time and you aircraft will be fine. I’m looking to use some HPB points at the property in the area myself later this year. Will bring sunscreen but no tie downs.
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By PeteSpencer
FLYER Club Member  FLYER Club Member
#1613510
Go to Bergerac: Don't be put off by all this pseudo science and tubs of water: You'll never see a local in France tying his a/c down.

Just exercise due diligence : Check when the RYRs are due in and what time the firemen change shift (They buggered off at 5pm when I went there, leaving five a/c at the pumps -they do/did the fuel too- who had to wait till the following day to refuel.

You can pick up your hire car and drop it off at Bergerac airport and the town itself is simply stunning.

Have a great trip and post pics when you get back.

Peter :thumleft: