Aviation knots

[RadioSaigon]

Yup, knots of the tying kind :ok:

Wondering what wonderous knots people use when tying their aircraft down, and do you have a particular reason for using a particular knot?

What knots are best for load-bearing, ease of tying, ease of release after repetitive strain... that sort of thing??

[Di_Vosh]

A Round turn and 2 1/2 hitches (or variants of that) works pretty well. It's about the only one I do for aircraft. Easy to tie, (relatively) easy to undo, doesn't weaken the rope, etc.

Just did a 2 minute google search, and this website had a decent amount of info.

The Most Useful Rope Knots for the Average Person to Know (http://www.layhands.com/Knots/Index.htm)

From what I've seen, most pilots can't tie knots, and just do "If you can't tie knots, tie lots" :E

DIVOSH!

[maui]

A lot of pilots can't knot ties either. But that's another story .

M

[the wizard of auz]

I always use a bowline. will take all you can put on it and undo it without dramas. if you have a tail left on the rope when your finished, a couple of half hitches around the rope finishes it off nicely. :ok:

[Bevan666]

And clove hitches when you need to attach a rope to a wire rope along the ground

:ok:

[Fark'n'ell]

Bowline.Wont slip.Therefore it cannot come undone.

[Q300]

And here was me thinking you meant knots as in speed... :hmm:

Anyways, I use the bowline knot and the good old granny knot (or whatever your standard, rubbish knot that you first ever learn to tie is). Plus bows... you gotta tie your shoes somehow.

[compressor stall]

FWIW, we use inch thick rope that has slightly different characteristics than your average nylon rope. We tie an overhand bite (or an alpine butterfly) halfway up to the tiedown point. Then the free end goes through the tiedown, back through the bite, is tensioned and tied off at the bite with with three half hitches.

It regularly survives gusts up to 100kts and occasionally beyond. :eek:

[OZBUSDRIVER]

Bowline is the go, once you learn how it works you can adjust very easily to get the right tension with little effort......it looks neat and professional to boot:ok:

[OZBUSDRIVER]

Stallie, that knot looks interesting. Good properties, load is not transmitted through the knot. Inch thick? Would be a solid looking knot.

Alpine Butterfly (http://www.realknots.com/knots/sloops.htm)

[Yakka]

Im with Compresser stall on the Alpine butterfly, easy to tie and always comes undone. You can tie it with gloves on as well.

[compressor stall]

Its best use is where you want a knot pulling around 90deg to the line (ie a holding a fallen climber tied into the middle of a rope between two others). In that scenario it has significant advantages over just about every other knot.

However, when the load is pulled parallel to the rope, then the AB's loop performs similarly to other some other knots. This would be the general aircraft tiedown scenario so it's horses for courses whether you use it or not.

My personal favourite though (not for aircraft) is a double headed figure of 8 on a bite - which I did use a lot back from my SRT caving days.

And you bowline aficionados, can you tie one completely one handed? :p;)

[triadic]

Round turn and 2 half hitches does the job most of the time. Otherwise as said above a Bowline is good if you don't want it to slip or get tight.

Largest problem I have observed in tying down aircraft is that they leave the rope slack - very slack. May as well not tie it down!

The secret is to how little slack. Tight is often better.

Army procedure used to be pull it tight with one foot on the rope at the ground end - width of boot was the slack - would be less for a low wing.

[The Green Goblin]

I used to cringe when i saw pilots pulling down on the ropes making sure they were nice and tight...........

I used to use a bowline when flying pistons and having to tie down.

[compressor stall]

I used to cringe when i saw pilots pulling down on the ropes making sure they were nice and tight...........

Is that because you are worried about rope shrinkage? Most modern nylon ropes -especially kernmantle style (climbing or yachting) ropes- have relatively insignificant shrinkage.

It's the older hawser style cotton ropes that swell when wet that shrink, possible straining the wings (equivalent to neg g's) if ties really tight when dry.

[fatboywings]

1/ I also use the bowline. I have a tigermoth and it really doesn't like wind, on the ground or in the air.

2/ I have always found after securing the aircraft that some healthy size chocks in front and behind the mains will help stop the aircraft twisting in any big gust, also, The other place I see that people forget to tie all to often is the control's. I always tie the stick hard back and align aircraft with the forecast strong wind direction the night before, helps stop been run over when alseep under the wing.

edit
oh yeah and triple peg if on grass.

regards
Ben

[The Green Goblin]

No its because the ropes are not meant to be tight or loose just half way in between therefore not placing stress upon the airframe but preventing it from being blown away in a wind gust/willy willy etc.

You used to see fellas at places like JT using the ole truckies hitch getting their back right into it..........:ugh:

[SystemsAreGo]

The terrorist comes out the hole, goes round the tree, then back in the hole.

The bowline instructions with a 21 century twist :}

[The Green Goblin]

I always tie the stick hard back and align aircraft with the forecast strong wind direction

Perfect attitude to create a bit of lift and leap of the ground with a stiff breeze on the nose eh :P

Have a look at how most factory control locks place the elevator!

[fatboywings]

Hi there,
With the limited notes on the Tiger (most have not even seen a takeoff and landing chart) and been a tail drager, what would you suggest? I am always open to any ideas that will see me through a bad situation (if i am dumb enough to put myself there, i guess we can all expect a blonde moment and if we don;t we are not following the golden rule, be prepared.)

thanks in advance
Ben

ps stick hard back = stall

pps Stall = loss of lift

[kingRB]

I always use a bowline. will take all you can put on it and undo it without dramas. if you have a tail left on the rope when your finished, a couple of half hitches around the rope finishes it off nicely.

I religiously learned to tie a bow line when I read it was "the" knot to use for tying down... It is fantastic on one end, either on the aircraft or on the ground, however i've found its pretty useless tying a bowline on both ends, as its next to impossible to get decent tension on the rope once one end is already tied down..

I'vealso tried using a bowline with two half hitches on the other end, and while it is secure, again, I always end up with too much slack in the rope, and you have to spend way to long stuffing around with it to try and get it taught.

I have some mates who can tie a "truckers hitch" - and this one seems to be by far the best i've seen. You can easily adjust the tension on it once the knot is in place - and any pulling force on either end only tightens the knot further. Only problem is I havnt been able to master tying it by myself yet - it is not the easiest knot to learn.

[The Green Goblin]

ps stick hard back = stall

pps Stall = loss of lift

ppps Stall = AOA relative to the airflow

Think about the AOA on the ground basically the rigging angle of the particular airframe and if we consider something such as a 150 she needs to achieve 16 degrees to stall, sooooooo logically thinking, she'll go nose up with a stiff breeze, leap into the air, stall once exceeding the 16 AOA and plunge to the ground once gravity exceeds the lift being produced.

[fatboywings]

The truckers hitch has a god and bad history. In Australia our work place safety dept "WOrkcover" outlawed the knot several years back due to a few too many incidents occuring with the knot letting go. Just a heads up on o few $100,000 spent on reasearching the causes of the accident and the actual knot it's self.

[fatboywings]

Are we forgetting the tiger is tied down and the tail will never let the wings exceed 16 degrees RAF. Enough defence of what i do already, I am yet to hear your suggestion that is relative. I don't believe (due to the quality of your previous comment) that you realy are so lame as to stand there and shake your head and not offer your advice to my previous question. Please tell me what could be a better solution?

thanks
Ben

edit
I see you have made further comment about the 150 and I may have made a bistake previously with my comment about the AOA. A tiger will sit on the ground with about a critical angle for a 38knot head wind. with that in mind and knowing that we tie down the tiger wing so that they a a little slack ( enough to let the wings rise and exceed the 16 degrees and stall the both top and bottom) and the tail is fastened so that it is unable to rise, we do not encounter the problems you mention above.

You obviously have a good understanding of flying, are you endorsed on tail draggers? if not i can totally understand your previous comments and do not believe you to be lame, still want to hear your suggestion though.

[The Green Goblin]

fatboywings

Never flown a Tailwheel, your logic makes sense however if you left the stick in the aft position into a 38kt wind, and for one reason or another you did not tie the tail wheel down immediately or the wings for that matter, the slats open (which you may have forgotten to lock) due to the AOA being close to the critical angle and before you know it............

Are we forgetting the tiger is tied down and the tail will never let the wings exceed 16 degrees

ps stick hard back = stall

pps Stall = loss of lift

Interesting logic you apply! from memory with the slats open the ole moth can get close to 23 degrees nose up before a stall............whats the AOA on the ground?

Having said all that, never flown a tail dragger so Ill leave you to it!

[Monopole]

23 degrees nose up is differant to 23 (or 16 for that matter) degrees to the relative airflow.

Also the aircraft does not come: plunge to the ground once gravity exceeds the lift being produced. rather the centre of pressure moves aft along the mean aerodynamic cord causing a pitch down moment. So using your logic Green Goblin, and based on fatboywings account of the AOA of the Tiger Moth (on the ground), the CoP would be behind the CoG and the 'ol moth' should not be leaping anywhere :}:}:confused:

[clark y]

What about all the other types that get controls tied full back with the seat beats. Seen a partenavia and lots of piper singles. I suppose if the knot lets go (which is the original question) then you would see how the flight controls would guide the aircraft on its solo flight downwind. I suppose the trick is to tie the aircraft down so the knot does not let go.

p.s. also a big fan of good chocks.

[The Green Goblin]

I worded it wrong, 23 degree AOA on the 'ole moth before a stall. Regardless the COP has to move forward with increasing AOA before it moves aft at the stall.

Also dont forget that a Moth has a swept upper wing and with swept wings the COP moves forward and inboard at the stall causing a pitch up :ok:

[the wizard of auz]

I have some mates who can tie a "truckers hitch" - and this one seems to be by far the best i've seen. You can easily adjust the tension on it once the knot is in place - and any pulling force on either end only tightens the knot further. Only problem is I havnt been able to master tying it by myself yet - it is not the easiest knot to learn.

Actually, its called a sheet shank. Its a pretty handy knot. if you use a hard nylon style of rope, it can be a problem, but if you use an extra twist and loop on it, its fine. If you can't tighten a bowline, you just need practice. its a pretty easy knot to learn and takes no longer to tension than a sheet shank.
I personally like a little slack on the rope to let the aircraft wobble about and do its thing in medium winds. never hurts to throw a couple of chocks under the wheels either.

[HarleyD]

A tiger will fly quite happily from a stationary three point attitude in a good stiff wind with two persons on board.. I recall some years ago I was maxed out at 1950 rpm watching a squall line approaching the air field that trying to get to in a 15 kt headwind. The line was picking up a lot of dust and was moving very fast from the opposite direction. I arrived over the perimeter fence at about 200 ft when the wind hit and actually the sprog the Tiger and I ceased all forward motion until I dived to ground level and crawled across the field at about walking pace to the grassed area in the centre of the runway triangle where I had about 3 or 4 goes at landing. When I reduced power to try a three point attitude the mongrel thing went about 20 feet in the air and started to go backwards..HMMM… tried a few wheelers, but every time I tried to lower the tail the thing would slide backwards, the skid would stick in the ground and the mains would lift off again, so full noise and back up into the hover. Eventually a few concerned individuals appeared form the hangars and looked like they would assist so I hovered over , settled down between two hangars and chopped the switches as about 20 guys grabbed onto struts and the rear fuselage and anywhere else there was a space and trundled it straight into one of the hangars. Time for ‘tea and medals’.


I do not recommend leaving a Tiger unattended outdoors, regardless of the apparent security of the tie downs. Use 1 inch rope and do a double bowline sheep shank with 222 and a half hitches, the rope and the tie down rings will most likely be there the next day, but not so sure of the Tiger….. still no great loss I suppose, they are a very poor excuse for an aeroplane, though it seems they are highly valued by collectors and enthusiasts (of Tigers that is) and sometimes they are quite a lot of fun, but only sometimes.


I have used some sort of knot that I was taught as a young ag pilot, by another aggie who was also a seaplane/flying boat pilot, don’t know what its called but its halfway between a partial bowline finished with a couple of half hitches, locks tight when under load, but very simple to release, even when wet.


HD

[The Green Goblin]

What about all the other types that get controls tied full back with the seat beats. Seen a partenavia and lots of piper singles.

You are going to need at least a 60kt wind to make her do anything, so I suppose the benefit of the elevator locked in the aft position (nose up) out weighs the penalty of something unfortunate happening, besides the Partenavia doesn't want to fly even when she is supposed to (ugly bloody thing)

My comments were more aimed at something 'light' The moth being a good example, 150 or any LSA type aeroplane.

Thanks HarleyD I love hearing stories such as that!

[Lodown]

HarleyD, I'm repeating this secondhand from a guy who has probably passed on by now, so forgive me for any errors of recollection. He had some wonderful stories about training in Tasmania.

In the early stages of WWII, there was a training base in Western Junction near Launceston. (I don't know how long it stayed operational.) The Tiger Moths would be all over the place when the westerlies would kick in and the base personnel would wait for the phone calls from the various aerodromes the trainees landed. For the aircraft in the circuit, the ground personnel would line up along both sides of the runway and whoever happened to be nearest the aircraft when it was on or near the ground, jumped onto the wing and fuselage to hold it down. Supposedly it wasn't uncommon for the occasional go-round with an extra pax or two.

On the subject of knots, a bowline, a tautline hitch, a trucker's hitch with a half hitch for security on the loop, half hitches, or a combination. They've all worked for me. Never liked the trucker's hitch that much though. It has to stay tight to work properly even with a half hitch on the loop. I like the alpine butterfly knot that Stallie speaks about. Doesn't work so well if you change aircraft though. The knot may have to be undone when tying down a low wing after previously using the rope for a high wing. And Stallie, any firefighter should know how to tie a bowline one handed.

Regarding tying the elevators: I would have thought it more important just locking them in position - any position -rather than have the elevators flap and bang themselves to bits on the stops and stretch the cables. It would seem to me to be far more important than worrying about whether the AoA on the ground was 10 degrees or 110 degrees.

AoA on the ground and a relationship to elevator position? What garbage! So what you're saying The Green Goblin is that if the wings lift off in a high wind, a back stick and a tied down tail is going to encourage additional pitch up? Maybe a slight chance in a nosewheel where the tail has somewhere to go, but a taildragger? If anything, it's keeping the aircraft on the ground.

[Magarnagle]

I double up the rope (always recommended for nylon ropes, and safer anyway with hemp or other natural fibre ropes) , loop it through the tie down point, and run two or three half hitches (three for nylon) close to the tie down point after taking out the slack. I do it in such as way as to be able to pull the loose end of the rope so the whole knot disassembles itself, and unties without having to fumble around loosening the knot to get it undone. I put another half hitch for the loose end, so it won't untie itself inadvertently.

If there's a stiff wind expected, a variation on a truckie's hitch can do the job pretty well.

[RadioSaigon]

Some beaut responses there guys, thanks... very informative! Thanks also Di Vosh and OzBusDriver for the links -excellent!

Bevan666: you raise an interesting point... with a fixed-line tie-down available, how do you prevent your bottom knot (on the fixed line) slipping along the line? Especially if there is no fixed point to attach your own lines?

I wonder if our web-footed compatriots can add anything further to the discussion? Are there particular knots you find useful in the sea-borne world?

[fatboywings]

harleyd and lodown,

awesome accounts of times gone by and i hope i never find myself in either stuation, but if so i will know to hover around until 20 guys turn up. Tigermoth flying is a different world and needs to be experienced to be appreciated. I would never leave a tiger unattended over night and don't care for been run over so take special care when flying away.

tie tight and fly right.

kind regards
ben

[werbil]

We don't use many knots in the traditional manner. We normally splice loops into the end of our lines The Eye Splice (http://www.animatedknots.com/splice/index.php) as they are very strong and permanent.

All of our floats are fitted with cleats at both ends. We generally secure lines to the aircraft using a cleat hitch The Cleat Hitch (http://www.animatedknots.com/cleat/index.php).

We use an alpine butterfly on one of the fixed lines on our semi-sub to prevent the aircraft moving either forward or aft with a single rope whilst embarking and disembarking passengers.

If we are using someone elses mooring or picking up from a boat we will often tie a figure eight on the bight Figure Eight on a Bight (http://www.spadout.com/wiki/index.php/Figure_Eight_on_a_Bight) so that we can hook the loop over the back half of the forward cleat. We can then let the aircraft float back prior to starting the engine. When we start moving forward the loop falls off the back of the cleat - being attached to another boat/mooring prevents us from drifting into something expensive if the engine doesn't start.

The other knot we use is a bowline to secure the loose end of the anchor rode to the float locker to stop us from losing the anchor.

Rope selection and care is very important. Nylon is excellent as it is very strong and stretches under load. 12mm nylon has a breaking strain of 2940kg compared to only 1260kg for the same sized silver rope. Keep rope out of the sun, dry and away from chemicals to prevent deterioration.

A bare (web) footed pilot.