[Heady]

When doing my UK NPPL pilot license exams a few months ago - I had to know and calculate contaminated runway hydroplaning speeds.

During a drive in the wet the other night it got me wondering why this is never discussed during driving license exams.

This video presents some general info regarding hydroplaning & car tires.
examine it! Aquaplaning | drive it - YouTube

This video shows the 1960s FAA/NASA formula taught for pilot exams...
Hydroplane formula - YouTube

Dynamic Hydroplane Speeds - Tires Rotating (1960s FAA/NASA)

PSI	knots (9*√PSI)	mph	km/h
29	48	56	90
30	49	57	91
31	50	58	93
32	51	59	94
33	52	59	96
34	52	60	97
35	53	61	99
36	54	62	100
37	55	63	101
38	55	64	103
39	56	65	104
40	57	66	105

Dynamic Hydroplane Speeds - Tires Not Rotating (1960s FAA/NASA)

PSI	knots (7.7*√PSI)	mph	km/h
29	41	48	77
30	42	49	78
31	43	49	79
32	44	50	81
33	44	51	82
34	45	52	83
35	46	52	84
36	46	53	86
37	47	54	87
38	47	55	88
39	48	55	89
40	49	56	90

Although, the following report shows that the 1960s FAA/NASA formula may not be valid for the current newer (2001) aircraft tires!
http://www.nlr-atsi.nl/downloads/hydroplaning-of-modern-aircraft-tires.pdf
Actual experimental data showed the current newer (2001) aircraft tires broke away at a lower speed than that predicted by the 1960s FAA/NASA formula!

Anyone have any additional info?

Just noticed that suferdude mentions up to 40PSI here so have updated the tables above.
Tyre Pressures

[The Gonz]

I always have mine as 41psi so I'm safely off the chart.

[Surferdude]

I can only speak with regard to road tyres, not aircraft tyres but I can't imagine how any meaningful figures could be obtained for the road.
Tread depth, various types of uneven wear, footprint width, speed, rim width in relation to tyre size and tread patterns would all have a bearing on the results.

[The Gonz]

Same here. I can't take those readings seriously.
They'd be a very rough indication of escalation with no direct value to a given situation.
Even atmospheric temperature, humidity and pressure would have a bearing.

[Heady]

Same here. I can't take those readings seriously.
They'd be a very rough indication of escalation with no direct value to a given situation.
Even atmospheric temperature, humidity and pressure would have a bearing.

This is what I find interesting... 
Those equations correct or not are a go - no-go calculation for aircraft flights. 
Almost all aircraft flight manuals I have read reference them and failure to heed them would affect legal liability & insurance. 
So even if wrong - those equations must be considered "safe" for variable levels of safe for that industry.

However, I cannot find much in the way for cars.  Everyone says its complex... but given the number of cars compared to number of aircraft - I would have thought that there would be a larger body of evidence.
This is where I was hoping that maybe suferdude with his contacts might be able to help?
Or if someone on this forum has contacts into police RTA forensics?
Or if someone has friends in formula 1 racing where millions are spent modeling this type of thing?

I have found this written in 2015 - so it is a bit more recent than 1960s and is focused towards vehicle crash forensics.
http://www.crashforensics.com/papers.cfm?PaperID=56
Which only includes vehicle speed, tread depth, water depth, pavement texture, & tire pressure.  Doesn't mention anything relating to temperature, pressure etc...    ????

[The Gonz]

Interesting read but suspiciously quantitative proposing a 'best fit' formula to what had been determined in an entirely qualitative way.

[Surferdude]

http://www.tirerack.com/winter/tech/techpage.jsp?techid=3

We had a Goodyear Eagle Aquatred for a while. Two massive hydra channels around the tyre and a directional tread pattern. It would disperse 7 litres of water from the footprint EVERY SECOND at highway speeds.

But at the end of the day, regardless of pattern and all, the other elements,  a road is not like an airport runway. It has dips and hollows everywhere and if you hit a puddle with one or both sides of the car, you're going skiing,  like it or not.

[AlanHo]

I would imagine that the tread pattern would play a part. From my casual observations - commercial aircraft tyres - if they have a tread pattern - have just circumferential grooves around the tyre. Hence they only dissipate water in the longitudinal direction (fore and aft!!).  A major difference between aircraft and vehicle tyres is that aircraft favour using cross ply tyres because of their stiffer walls whereas vehicles tend to favour radial tyres which maintain a flatter tread. 

Vehicle tyres also have circumferential grooves but also lateral or angular grooves which enables them to dissipate water sideways as well as fore and aft.

( Facts brazenly stolen from the Dunlop aircraft tyre website)

[Heady]

... It would disperse 7 litres of water from the footprint EVERY SECOND at highway speeds.
...

That is quite impressive.

[Heady]

... they have a tread pattern - have just circumferential grooves around the tyre. Hence they only dissipate water in the longitudinal direction (fore and aft!!).  A major difference between aircraft and vehicle tyres is that aircraft favour using cross ply tyres because of their stiffer walls whereas vehicles tend to favour radial tyres which maintain a flatter tread. 
...

My understanding is that aircraft tyre design is mainly for straight braking.  Aircraft tyres don't have to steer around bends at high speed.

Anyway - it has been a good thought experiment and I've learnt a bit.

I'm thinking of contacting the AIM (Advanced Institute of Motorists) here in the UK and asking the same question to see what the response is...

[FatBoy]

I visited an aircraft tyre factory in Melbourne about 25 years ago, a very interesting place.  What I found most interesting is that aircraft tyres are designed to be retreaded, and that nearly every airline (well, the smart ones) use retreads on their aircraft.  They have a code on the sidewall that lists how many times it has been done, and when.

[The Gonz]

Yes, I routinely inspected an aviation safety equipment warehouse in my last job. Tyres stacked to the ceiling among other things. I saw then how retreading is common.