Aircraft chocking
 

Do you always chock your aircraft or rely on the park brake to hold it (even on an obvious slope)

Are there any guidelines on when to chock or is it once of those 'common sense' items that falls under the term 'airmanship'?

Never rely on the parking brake. If rolling is possible or harmful, chock, or tie down.

It depends to some degree on the plane.

A Cessna (high wing) is much more affected by surface winds, and routinely needs to be tied down if parked in an open area. Chocks are necessary but not enough.

A low wing plane is less affected. Mine (TB20) is quite heavy (1400kg) but I still always chock it, even though I know that, on a flat surface with no brakes set, it would probably take about 30-40kt of wind to shift it.

One cannot rely on parking brakes alone because the hydraulic pressure can be relied on to leak out, generally overnight.

Speaking of chocks, I had something funny happen to me a short while ago: I parked at Lydd, and when I got back ~ 3 hours later, the plane had moved about 5 yards but was still chocked, and one of the two aluminium chocks (both were still in place) was totally flattened - obviously been driven over by a truck. How is that possible?

What makes me laugh is the tyre with a slug of concrete poured in it being used as a tie down anchor. There about as much use as a tits on a bull.

All they do is add max 3knts to the wind speed that the thing will takeoff on its own. The rest of the time they just sit there stressing the airframe by putting a point load on it and jerking depending how tight the bit of rope is.
Quite a few have managed to get airborne with them still attached.

I have seen a C172 picked up and shifted with 3 of them dangling off it along with a tommy which was not tied down. This was due to a Seaking landing about 100 meters away from them.

Again this something the yanks have more of a clue about with aviation. Most GA parking areas have upside down unbrella ground anchors or sunk eyes in the apron concrete with cables running that you actually tie onto.

AL is used as a low friction metal in alot of designs linked with its low density. Unless it is pre loaded I am not suprised it moved. Its also quite springy under small loads so has a tendency to ping out. Persoanally a half round wooden fence post cut down the middle with a bit of rope linking the 2 sections makes a better chock. Those AL chocks are only good for kidding the refueler on that its chocked so they will start pumping.

I've seen a C172RG pivot 180 deg. around a concrete tie down anchor. Aircraft was left with tie down on one wing only and no chocks. Fortunately no aircraft park in immediate vicinity.

I saw a pilot try to taxy away once with a rear concrete tie down block attached!

(Allegedly) one or two people have managed to become airborne with tie down blocks still attached.

it makes sense to back up the brakes with chocks for the simple reason that brakes don't always hold. If you are parking for any length of time though it is certainly worth using tie downs. It is worth however considering a few things when using tie downs.

Assuming that the aircraft is on level ground to start with (if not then tie it down) what is the wind expected to do. As long as it is parked into wind I am quite happy to leave a Cessna 172 without tie downs in up to 35-40 knots. Any more than that and I sleep better if it is tied. However it is best to tie it in a way that it can weather cock into wind because they will bounce quite happily without any risk of turning over, something I have witnessed in 50 G 60 winds. I cannot speak for other types however. It has always puzzled me why many light aircraft have their controls locked with the seatbelt ie full up elevator and aileron in one direction or another. A wing that was at 0 angle of attack has its AoA increased as the wind gets up and wants to roll as well asking for a light aircraft to fly earlier than it otherwise would. Cessna have a wonderfully simple system of the wire lock on the column so the windier it gets the more it pushes nose down therefore increasing the windspeed needed before it wants to fly.

Another post mentions the stupidity of using concrete filled tyres, a total wast of time. Equally so is connecting a suitable tie down to your aircraft using very thin rope! Something you see at almost any airfield. Just remember that while most light aircraft have useful loads of 200 to 600 kgs the wind pays no attention to poh maximums and the aircraft will easily carry more with a few extra knots of airspeed so the only rope worth using is that which has a breaking strain in proportion...........on each wing!

Personally if the plane is goin to be sitting for anything more than a week I would chock all three wheels and leave the parking brake off. It will stop you getting problems with the brake pads binding to the disks. As well you can get areas of rust forming on the exposed bits of the disk and none under where the pads are giving you differences which will cause judder and possibly warping. This is but a theory so good be bollocks. Hopefully A and C will be along to correct me if i am wrong.

The other important reason for not leaving the brakes on is that, in many cases, the plane needs to be moved, and if you left the brakes on, they can't do it unless the door is unlocked.

Also, sometimes some stupid person with a tug will try towing it without checking if the brakes are off, and rip off the nose gear...

I have seen a fully chocked and tied down aircraft break loose and destroy my aircraft in the last week.......

As a matter of interest what was it tied down to? And how much wind did it take to move it?

It was tied down to the planet and took the wind generated by 2400rpm of Gipsy major engine to move it..........

goes back to texs point about using rope not bits of string.

Bugger hope it gets fixed up soon.

It's written off. The bloke did not apologise and I had to find out his insurance details and contact the assessor off my own back. Lets just say I am not amused.
:*:*:*:*:*

Right thats another pilot who is on the list for SAS's attitude correction technique.

What on earth was he doing at 2400rpm near parked aircraft.

Hand swinging his aircraft with the throttle wide open.......

What was yours again a C152?

It was my Auster that was killed (by another Auster oddly enough) not my 172.

Bose-x - i can relate to your incident which is why I started the thread in the first place. An unchocked aircraft (recent arrival) rolled down an obvious slope and hit my car (causing considerable damage) and I was curious to see how others viewed the subject. Like your incident the pilot did not apologise either so another candidate for attitude correction and appreciation of airmanship & common sense.

Good luck getting it sorted.