Twin ... I'd have thought this was the same as tyre "creep", which was one of the things that I was told to check for during the daily inspection, when I first learned to fly. I'm pretty sure that "creep" happens for a lot of reasons other than touching the brakes after take-off.

When flying my first retractable u/c aircraft, I well remember the instructor telling me to touch the brakes after take-off, to ensure the wheels had stopped spinning before retraction. I'm not aware of any prangs that could be attributed to this practice, but have seen many instances of tyre creep.

I'm still inclined to stop the tyres rotating before retracting them these days. And if I'm in any doubt about the amount of creep that I detect, I'll always get an engineers opinion about replacement because I know that it could spoil me day if I ignored it.

Any other ideas out there?

<<tom775257 So why don't you explode when you surface>>
Sorry to go off topic:
Simply breathe normally on a standard ascent, and allow the pressure to equalise from within your sinuses/ears. Sub-aqua does has the unfortunate side effect of upon ascent, the entire contents of your sinuses ends up out of your nose, all over your face due to the increasing volume of air in your head. This is especially bad if you have a cold..... Seriously though, on a fast ascent you run the risk of damaging your lungs. Regarding pressure and the like: When diving in Egypt, due to getting thirsty under water (water water everywhere, but.....), we used to take capris-sun down with us to drink (a drink in a foil pack), as it had no air in it, it didn't compress, hence no problem.
On a vaguely aeronautical note, our club tried many things to enhance communication under water. The best way by far we found was a pair of the old pneumatic headphones given to PAX. The person you want to talk to puts on the headphones; you blow out the water, then speak through it. Worked very well! I used to have a set attached to my stab jacket.
Cheers, Tom.

On all large aircraft the brakes are automatically applied when the gear is retracted.
So it should work just as weel on small ones, by manual application.

In the same vein, but only different, I have oft wondered why the brake temperatures don't cool from typical after t/o temps of 100 - 150C to much less than 15C after upward of 4 hours at -60C. Any ideas?
Cheers,
mcdhu
'Interesting - but only marginally so!'

Idiot's guide
 

To get a simpler view on this tyre (tire, US) explosion business, I find its much easier to work with numbers as well, rather than word equations alone.

Example:
Tyre pressure gauge (gage, US) indicates tyre is inflated to 600 lbs/square inch.

Outside (or ambient) air pressure gauge indicates 15 lbs/square inch on the ground.

Outside air pressure gauge at a typical airliner cruising altitude indicates 2 lbs/square inch.

Actual tyre pressure=Indicated tyre pressure - outside air pressure

Tyre pressure on ground=600 - 15
which equals 585 lbs/square inch.

Tyre pressure at altitiude=600 - 2
which equals 598 lbs/square inch.

So the total difference between the pressure on the ground and at altitude equals 13 lbs/square inch (15 - 2).

The tyre is only therefore increased in pressure by 13 lbs/square inch, which is not a lot, so the tyre is not under enough strain to burst or explode.

I hope that has helped!

Cheers, Tri

Thanks to those taking the trouble to explain why tom775257 doesn't explode when surfacing from a dive.

I guess I left out the :D :D :D . It was tongue in cheek! Sorry!

I doubt tyre creep could be caused by braking after takeoff, unless the mass, and therefore momentum of the tyre was significantly higher than that of the wheel hub. Much more likely to happen during landing.

I was told by an instructor that landing in a crosswind without getting the aircraft lined up with the r/w puts was a major source of creep due to the sideways forces pulling the tyres away from the rim at the same time they start to rotate. Any truth to this?

On gear retraction... Would gyroscopic progression be a reason to brake the wheels before retraction? Obviously only for gear that retracts perpendicular to the rotation of the wheel, i.e. most main gear. Heard this mentioned on this board before but nobody knew for sure.

Stopping gyroscopic effects is an important reason for stopping the wheel rotation prior to retraction.

Trislander

I think you've made an error with your formula.

For the tyre gauge to indicate anything the pressure on one side of the gauge must be greater than the other. It's a differential instrument. In this case it's comparing pressure inside the tyre to ambient pressure outside the tyre.

To use your example, for the gauge to indicate 600 psi the pressure in the tyre has to be 600 psi greater than outside the tyre.

The pressure outside the tyre is 15 psi so the total tyre pressure must be 615 psi & not 585 psi in order for the guage to read 600 psi

Actual (total) tyre pressure = indicated plus ambient




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