Tying down aircraft

[Rabbs]

Is there any rule of thumb around tying down an aircraft overnight, I wasn't taught anything on the PPL and wondered if anyone had any thoughts/experiences or are there any references. I've googled it and can find a million tie down kits but no advice..

Obviously if there are storms expected then it would be prudent to hanger/tie down - do people generally tie aircraft down if leaving outside for a couple of days or not bother unless strong winds are forecasted and what would be classed as a strong wind?

Aircraft is PA28..

[rsuggitt]

My club ties down every non-hangared aircraft every night.

[privateer01]

If its YOUR aircraft...its funny how you tie it down every night.

You believe the forcasts?

Tie it down if you want to be assured it will be there and in one piece when you return.

Additionally locking the controls is extremely prudent...even if its with a seatbelt.

[Duchess_Driver]

What always makes me laugh is when you see people tying their beloved investments to a block of concrete or a stack of concreted tyres.

The wing is designed to lift far more than a concrete block and a few tyres!!!!! There was an incident where an aircraft took off with one still attached - shows their worth. (Newcastle rings a bell somewhere!)

Personnally, always tied mine down at the end of the day. Tightly, with a good knot. Never really thought too much about the tightness - some people advocate a loose tie down others get it as tight as possible. Always liked a little bit of flex!

[jxk]

Just to keep the subject going. Tail into wind or not? Tailwheel v nosewheel? Elevator/Stabilator up or down?

[Duchess_Driver]

Tail into wind or not? Tailwheel v nosewheel? Elevator/Stabilator up or down?
Today 17:40

Not really sure it makes alot of difference in the long run....who's to say where the mighty wind will blow from tomorrow. Some aircraft are tied down for weeks / months.

Just make sure the controls are locked as Privateer says.

[percy prentice]

Keep the tie downs loose. If you use those corkscrew pegs & the rope is taught you will find that any movement will make the corkscrew looser in the ground & if a big gust comes along it would not be strong enough to stay in. As said by others the control lock is very important. In really extremes tie the nose wheel down.

[polohippo]

I always teach my students to tie down the aircraft after every flight even if I know if it is being used again that day. The way I see it is that you are responsible for that aircraft and you must do everything to make sure it is safe. It gives you peace of mind that you did everything in your power to make sure it would be ok!!

Also, some friends of mine borrowed a brand new C172 G1000 with 100 hours on it, went to Atlanta, went out for dinner and when they came back the ground crew were sweeping it up with a dust pan and brush after a freak storm!

It's better to be safe than sorry!

[Piper.Classique]

You can tie the aircraft down to really good ground anchors, using steel cable, but sometimes it just ain't good enough. :{

Picasa Albums Web - Barbara - an2 (http://picasaweb.google.fr/piper.classique/An2?feat=email#)

http://i689.photobucket.com/albums/vv253/piper_classique/000_2911.jpg

[eharding]

Depending on the aircraft type, and the severity of the forecast winds, attaching surprisingly small cross-section wooden strips to the upper side of the wing can act effectively to destroy the lift the winds would otherwise generate, thus reducing the strain on any tie-downs. I've seen some rather cunning wing covers which have padded lift destroying features on the upper side to achieve the same effect.

The other tip is that having secured your own aircraft, have a damn good look at how well everything else parked in the general area is tied down - nothing worse than returning to your stoutly secured aircraft to find someone else's pride and joy has been blown on top of it.

[Pilot DAR]

Some older Cessna publications state that to be effective, the tiedown must have a tensile capacity of 700 pounds. This means that the rope or strap must have that capacity, which is reasonable to expect from anything 3/8" or more, and the attachment to the ground is at least that firm. Mi opinion of "doggy tiedowns" is very poor. I have seen many airplanes lying on their backs with ropes and doggie tiedowns still attached by ropes. I would only use them as a last resort. I disagree that ropes should be slack. If they have to be slack to not pull out the anchors, the anchors are inadequate. If you're piling concrete blocks, or other mass, make it at least 700 pounds. A 5 gallon pail filled with concrete is hardly enough. Think of it this way; could you hold the plane down in the big wind? How much do you weigh? If you can lift the tiedown block, forget it!

Tie only to tiedown points provided for that purpose - not around propellers, wingstruts, oleos etc.

If at all possible, park the plane into the wind you expect.

If you are going to secure the controls (which is good), secure them at the control surface if possible, not at the cockpit control. You don't want the forces applied to the flight control, being applied right through the whole control system. Control system damage is very hard to detect!

Be very sure all contol locks and plugs are very conspicuous!

Ask the person providing the aircraft to you, how they would like it tied down!

Pilot DAR

[skywagondriver]

This is a good write up on the subject

http://www.caa.govt.nz/safety_info/GAPs/Secure_Your_Aircraft.pdf

[Chuck Ellsworth]

When leaving a light aircraft parked outside for any length of time I always tie them down.

I always tie them down as tight as I can pull the rope and make sure the knots will not slip.

Leaving any slack in the ropes will only allow the airplane to move and may eventually break something.

[Tinstaafl]

Like Chuck, I use a taut rope or webbing strap to secure an aircraft. Tying down an object is the same whether it's a load on the back of a truck, a structure to the ground or an aircraft on the apron. The goal is to 'weld' the object to the supporting surface and not to give it leeway to buck around in gusts or whatever. Ideally, an aircraft should also point into the expected wind. If it doesn't then there will be aerodynamic loads that will try to weathercock it.

The type of knot used makes a difference. I've lost track of the number of times I've seen people use what are effectively slip knots that aren't cinched tight against the bight. It's common in the SE USA for two widely separated single half hitches to be tied half way down the rope. Damned if I know why they bother. It's about as secure as wrapping a horse's reins a couple of times around a hitching post. If the two half hitches were tied against each other to make them lock and at the bight so the standing end can't be pulled through it would be reasonable, but the knot in use barely qualifies as a 'knot'.

Additionally, you should chock the wheels and use gust locks (at the surface if possible, as suggested by another contributor to this thread. If strong wings are expected, consider using spoilers on the upper surface of the wings. Mind you, if it's expected to get that bad, I'd be looking for hangar space or ferrying away if possible.

[Chuck Ellsworth]

I carry ratchet straps in the Husky, they are excellent and easy to tighten and don't work loose.

[Tinstaafl]

I use a truckie hitch (aka power cinch, haymaker's hitch or harvester's hitch) when i'm using rope and think I need to really ensure the aircraft is secure. It forms a pully from the rope so getting adequate tension isn't an issue. Use a doubled or tripled hitch and you could pull the tie-down rings out of the aeroplane.

[Laundryman]

If you have a cowl and cabin cover its worth making sure the ends of the straps are securely tucked away (its amazing how efficient the end of a flapping strap is in removing your expensive paint job)

[BroomstickPilot]

Hi Tinstaafl,

"truckie hitch, power cinch, haymaker's hitch or harvester's hitch"

Are these the same as the highwayman's hitch? (So named because it was supposed to have been used by highwaymen to make a quick getaway after robbing wealthy stage coach passengers ).

In the highwayman's hitch there are two lengths of rope extending down from the knot. One is tight and goes to the tie down ring in the ground, the other is a loose end that can be pulled smartly to release the knot.

I must say, I have often wondered why the highwayman's hitch is not used for tie downs.

Broomstick.

[Pilot DAR]

I can't resist, the AN-2 reminded me of a story from my notes:

During my latter high school days, one of my classmate’s father very kindly allowed me the use of his Cessna 172 every Sunday. It was their family preference to follow their spiritual path on Sundays, and this did not involve the use of the plane. In his kindness, father thought that I would enjoy the use of the aircraft those days, and I certainly did!

The plane had been kept at the owner’s home, but the 900 foot runway was a little less than he (or most other pilots) could safely handle, and the plane had come to some harm there as a result. It was thus moved a few miles away, and kept tied down at a local grass runway which was everything that a 172 could want. The residents at that farm, though not aviators, certainly made every effort to help, and came to rely on me for aircraft matters. I became the sort of caretaker of the plane, always willing to do what I could to keep things in order to repay the generosity.

The only other aircraft to reside at that runway, was a Seabee, which I never saw fly, and whose owner I never met. It was tied down several hundred feet away, across the “apron” such as it was, with it's tail into the prevailing wind direction. Both planes were tied down to stacks of patio stones, (whose total weight I would estimate at a few hundred pounds), around which ropes had been tied Flintstone’s style. Nobody had ever bothered to actually hammer in metal stakes to make proper tiedowns. It seemed to work, for a while…

Early one morning, the lady of the farm phoned me, and with a very upset tone, stuttered out “the planes blew into each other over night, come and do something!” Uh oh, I was the last one to tie down the 172 with it's nose into the prevailing wind direction, facing the Seabee across the apron. I thought "those Seabees are pretty dense, so if a plane was blowing around, it must somehow be my fault". Needless to say, school had to wait…

I arrived on scene to find the 172 exactly as I had left it, with the only difference being the Seabee shadowing it! The two planes were nose to nose, at ninety degrees to each other, and the Seabee wing was right over the 172 wing, without having touched it at all! The only contact was the tiedown rope of the Seabee wing, which still had the pile of patio stones attached, now took a path from the Seabee wing tiedown fitting, over the trailing edge of the 172 aileron, and straight down from there to the now swinging stack of patio stones! There was a crease in the trailing edge of the aileron, but with the weight of those concrete slabs, I was amazed that the aileron was not completely folded into the rear spar. Luckily the rope passed very close to a hinge, where the aileron was strongest. What a relief! I had not failed the 172 and it’s owner!

The Seabee, on the other hand was in rough shape. It had obviously cartwheeled across the apron, as both wingtip floats were torn off, the wing tips curled up, and the rudder and aft fuselage damaged. The fact that the wing tip float was gone by the time it got to the 172 saved the day, as it would have really hurt the Cessna wing of it had hit.

After great effort cutting and untying tiedown ropes, and moving the 172 bit by bit, I got it out from under the Seabee, and made it a new home a safe distance away, with many more patio stones this time. With some delicate bending, I got the aileron looking pretty presentable. I retied the Seabee's patio stones, lest it come to even more harm.

The 172 received the required inspection to assure that the aileron control system had not come to harm, and it was fine. The Seabee sat there for some time in it’s damaged state, with my knots in the tiedown rope, and then one day was gone. It sure did not fly out!

[RatherBeFlying]

Ah Yes, the 5 gallon cement filled container. One of my favorite C-150s had the tail tied down to same and all went well for many years until a strong North wind came up. I hear there was at least one husky fella hanging on the tail to no avail:ouch:

As for knots, I use the Taut-line aka. Midshipman's Hitch, viz: Taut-line hitch - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Taut-line_hitch)

This is not a knot for slick polypropelene ropes. Braided nylon will stand up to a few years of sunlight and provide a little give.

And yes, it helps to have the tail of a nosedragger placed so that it will not be exposed to the wind.

[Tinstaafl]

Broomstick,

Truckie's hitch is different. Trucker's hitch - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Trucker's_hitch) shows the version my dad taught me when I was a kid (no prizes for guessing what he did for a living).

This type of hitch forms a fixed loop on the standing end with the running end passed down and around the restraint point, back up through the loop and finally back to the restraint point to be tied off (although you can tie it off around the knot itself if rope length is limited). All that passing down, around, back up, through the loop & down again forms the pulley and gives a 3:1 mechanical advantage.

If you allow enough room you can form second hitch on the running end to increase mechanical advantag to 9:1, a 3rd hitch on No.2's running end to give 27:1 etc. Need a fair bit of rope & room though.

[philipnz]

http://www.hartal.co.nz/tiedown.jpg

[BackPacker]

I don't like the picture that goes with that Wikipedia article. There is absolutely nothing but the friction of the two half hitches that keeps the upper part intact. Depending on the type of rope and its surface friction, I think that top end will work itself loose very quickly.

If you follow the link to the Animated Knots by Grog website you'll see a variation where the upper part cannot come undone, other than by undoing the whole knot. The top end is then either a slipknot or a noose, or a figure-eight slipknot or noose.

On the other hand, that Grog website suggests that once under tension, you tie the free end of the rope off with two half hitches. I would never do that with anything that's under tension, preferring a slipknot with a double half hitch instead. A plain half hitch that's been under tension is almost impossible to undo. When still under tension - forget it.

[Say again s l o w l y]

What's wrong with a nice simple Bowline? If it's under tension, then undoing it is difficult, but why would you be undoing a knot under tension?

[Tinstaafl]

Tied properly with sufficient length of the bight through the half-hitches it won't come loose. The tension locks the two half hitches in series. Neither can come undone unless the other is loosened 1st. What tends to happen with slippery ropes like polypro. is that the loop around which the half-hitch is formed slips through. More of a problem if only a single half-hitch is used instead of the two in tandem. An alternative is to add an extra half-twist to form a loop instead a proper half-hitch. That can be done with each half-hitch for a belts-and-braces approach.

My dad & I have secured all manner of loads for travel over outback roads using this knot & it's never come loose if tied correctly. It relies on tension to hold together so if the rope isn't pulled tightly then it can come loose.

[BroomstickPilot]

Thanks Tinstaafl,

I'll have a look at that Wikipedia article.

Regards,

Broomstick.

[BackPacker]

SAS, a bowline is good if you can do, and undo it without tension being applied.

The nice thing about the truckies hitch is that you can apply a lot of tension (three times your own weight, if you do it properly) and then tie it off. But that tension will usually be there (unless you've had a load shift, which is what you're trying to prevent) so it has to be undone under tension as well.

[Tinstaafl]

Most of the time for tie-downs I just pull the rope tight without using any fancy knots then use a slipped half-hitch for the 1st knot. That's followed by a 2nd half hitch using the bight just formed to lock the 1st hitch. Both hitches must be snug against the attachment point otherwise all that's formed is a slip knot with room to slip loose. If the bight or running end is long enough to flail around then I use more half-hitches as necessary to secure the loose bits to the standing end.

[BackPacker]

Tinslaaf, sounds like the exact same thing I would do.

Fortunately we have chains with carabiners permanently installed at our little corner of the field. Can't do much wrong with those.

[Say again s l o w l y]

Chains....Eeeek!

[IO540]

I like PilotDAR's contributions :ok:

IMHO, the most vulnerable planes are going to be lightweight ones with a low wing loading, and preferably high wing.

A C150 etc gets blown away easily, as do rag/tube taildraggers.

The least vulnerable will be relatively heavy low wing IFR tourers with high wing loading. I never tie down my TB20, though most of the time it is hangared. I carry the screw-in tiedowns but have never yet used them. With chocks, it is almost un-movable. I reckon it would take a 60kt wind to move it at all.

Regarding weights, anything a human can lift is going to be next to useless. A tiedown rope needs to attach firmly to the ground, so either to the rings fixed into a concrete apron, or the type which screws into the soil. There have been a good number of cases of pilots flying away with these tiedowns still attached (not sure how good the preflight check was ;) ).

The rope needs to be tight. It is a bit like a wooden panel fence in strong wind; as soon as there is any play in it, the wind will rapidly rip it apart.

[mikegolfpapa]

The lower the stall speed the easier they blow away and tail draggers have the added disadvantage of sitting at an angle of attack that helps this to happen.
I used to park my J3 tail to a strong wind with the controls locked, wheels chocked and tail wheel and wings tied down to screw in tie downs.

[RatherBeFlying]

This is a excellent, if ignored, knot -- and easy to learn, tie, adjust and untie.

Taut-line hitch - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Taut-line_hitch)

It's still my favorite knot for tying things down securely. You can tension the rope as you tie it and can even adjust the tension as it will slide like a Prussik; in fact arborists sometimes use it to climb trees. That makes it a knot that professionals are willing to trust with their lives:ok:

A good knot or hitch can be untied after being loaded and this hitch does not jam.

I have done several thousand miles with a canoe or two on top of my car at 75+ mph and the hitch has always held in 1/4" nylon laid rope.

While I am quite comfortable doing aerotows in a glider behind laid polypropelene rope, remember that glider tow ropes are done with eye splices as knots in the stuff are not dependable.

Polypropelene rope is not something I would trust to tie down anything worth serious money, but it is adequate for throw bags where you need length and light weight.

Bowlines can be shaken lose as some mountaineering accidents have shown; so, it's not something to trust unattended for a week or so unless seizing is used. It is also difficult to adjust tension with Bowlines.

[Piper.Classique]

I don't think it really matters which is your knot of choice, as long as it will stay taut and non slip until you want it to. The antonovs that blew away in Poland were all tied down to rings set in concrete. I don't know if it was the cables that broke or the tie-downs pulled out of the wings. Point is that sometimes the wind is just so strong that it will blow away hangars, not just aircraft :ugh:

[Tinstaafl]

I think there's an important qualifier in your statement that should be emphasized, Piper.C, viz. "...as long as it will stay taut and non slip...". There are lots of knots that look good and seem to hold but don't stand up to loading eg a granny knot. Also, as a general rule all knots become a weak point in a rope, some more than others so the type of knot can be important. No good using a 1000lb rope if the knot used breaks at some much lower value.

I found it surprising just how many people couldn't tie an effective knot. That's why I used to make sure my students knew how to tie rope tie-downs simply but adequately.

[TheGorrilla]

That's why I used to make sure my students knew how to tie rope tie-downs simply but adequately.

Fair enough.... As for the gimp mask???

[moggiee]

Not really sure it makes alot of difference
Trimming nose down for an aeroplane with tricycle (nosewheel) undercarriage makes a huge difference. When trimmed nose down, with the nose into wind, the upwards force from the tail keeps the nose low, reducing the amount of lift generated by the wings.

I've seen it first hand when we hand strong winds last year - our PA28s were skipping around until we trimmed nose down and locked the control columns forward.

Taildraggers are tricky, though!

[BackPacker]

our PA28s were skipping around until we trimmed nose down and locked the control columns forward.

The problem is that, unless you have Cessna-style control locks (pin through the yoke assembly), the advice in the POH is generally to restrict the control movements by wrapping a seatbelt around the yoke or stick. At least, that's the official advice I've seen from Piper and Robin. And this normally means that you have full-up elevator.

Locking the elevator full-down requires addition brackets or other things which might get lost or misapplied. And it contravenes the advice in the POH, although I don't know how serious that is in this case.

And furthermore, lift is not determined by the position of the elevator, but by the angle of attack of the wings. As long as the wind is not strong enough to lift the nosewheel clear off the ground, or extend the oleo to a sufficient length, it should not matter whether the elevator is trimmed or positioned up or down.

[Tinstaafl]

Lift will be affected by elevator position. As wind strength increases tailplane forces will cause the nose to pitch up or down, pivoting around the main gear (nosewheel types). Locking the elevators in a down position will produce a nose down pitching force, which in turn will aid reducing the mainplane's AoA.

[moggiee]

What he said (beat me to it).

The winds in question were 35kt gusting to damn near double that. In other words, the gusts were around PA28 rotate speed! Even with the controls tied back with the seat belt, full nose down trim made a noticeable difference. Our T-.tail Arrow was repeatedly lifting the nose wheel as the tail pushed down - ending up on the tail skid at one point. The trim settled it right down

[kbaybob]

I always tie my Seabee down with three 1/4" double braided nylon ropes (tensile strength 2,300# each). One on each wing and one on the tail, with the controls locked by the seatbelts, a bracket on the rudder pedals, and two pins on the rudder hinge. The tiedown points are three 1.5" pipes 7 feet long pounded into the ground with the ropes never coming straight up; always at an angle to the line of the tiedown stakes. I also chock the wheels. The the tail ring is the weak point on this Seabee. I loop the rope over the tiedown ring on the airplane and loop the other end around the ground tiedown ring, cinch it tight via a loop in the middle of the rope and apply two half hitches. It's similar to a trucker's tiedown, except that the loops are permanent.

If there is a big storm coming (over 40kt), I tie two more ropes onto different tiedown rings on the wing strut two different stakes in the ground that are just like the others, and another on the tail ring so the two ropes diverge at about a 45° angle. In addition, in those circumstances, I put two spoiler boards (2X4s) on each wing, covering the entire wingspan. The straps on those boards (ratcheting nylon tiedown straps) also help lock the ailerons and flaps.

If I am REALLY worried, I put water in the hull to increase the weight far past the gross weight limit.

I have always tied down my airplanes.

So far so good.

[Romeo Tango]

I have had my Robin Aiglon for nearly 30 years. I used to worry when it was windy and he was outside but have learnt not to. I now only tie down if the airfield wants me to and/or other aircraft in the vicinity are tied.

In my opinion if there is enough wind for the tie down to come into play then the aircraft is going to go, either with the tie down or leaving a bit of aeroplane if the anchor is the permanent type. (This probably does not apply to vry light types).

Though I do believe in control locks and the lift destroyers mentioned above sound useful.