Runway Friction Index

It is so useless we don't put it on the ATIS anymore

It's useless because pilots don't know what the number means, or what to
do about it. Pilots aren't told what it means because it's not much
used. It's not much used because...

So... what do the numbers correspond to? That is, if I hear a mu of 33,
what can I expect?

Jose
--
Nothing takes longer than a shortcut.
for Email, make the obvious change in the address.

"Jose" wrote in message
. ..
So... what do the numbers correspond to? That is, if I hear a mu of 33,
what can I expect?

http://www.newton.dep.anl.gov/askasc...9/phy99x80.htm

So... what do the numbers correspond to? That is, if I hear a mu of 33,
what can I expect?
http://www.newton.dep.anl.gov/askasc...9/phy99x80.htm

Yes, I know that much. But the coefficient of friction depends on what
I am contacting the runway with. And a mu of 33 implies epoxy, not
friction. (I would presume that they mean .33 and leave out the point,
but it may well mean .033, leaving out the .0)

To decelerate uniformly from 100 feet per second (about 60 knots) to
zero in 1000 feet would require 20 seconds, and deceleration of 5 feet
per second per second. This is about 1/3 the acceleration due to
gravity (for the pedants, yes, it's in a different direction). A mu of
about 1/3 (or about .33) would provide the necessary force, assuming the
entire weight of the aircraft is on the landing gear (not that great an
assumption, but good for starters).

So, what are representative mu for various conditions I would encounter
upon landing? (dry pavement, wet pavement, ice, snow, packed snow,
grass, fifth graders...)?

Jose
--
Nothing takes longer than a shortcut.
for Email, make the obvious change in the address.

"Jose" wrote in message
. com...

Yes, I know that much. But the coefficient of friction depends on what I
am contacting the runway with.

Most often it's rubber.

Jose wrote:
It is so useless we don't put it on the ATIS anymore


It's useless because pilots don't know what the number means, or what to
do about it. Pilots aren't told what it means because it's not much
used. It's not much used because...

So... what do the numbers correspond to? That is, if I hear a mu of 33,
what can I expect?

I have no idea. We were told the industry and the FAA got together and
came up with this system and the pilots that wanted the information
would know what the numbers mean. So far nobody ever asks for the mu.

"Newps" wrote in message
Yes, our airport can report in mu. I have yet to find the airline pilot
who finds those three numbers useful. They always ask for the standard
braking action report.

Consider myself found.

One night not so long ago, DTW approach switched runways on us while on the
base leg. It was unplowed. The first airplane to land on it was a Westwind.
The Westwind's crew reported braking as fair. Four inches of snow will stop
a Westwind.

I copied his report but considerd the source. A standard braking action
report is only as good as the crew making the report. Sure enough, the
Westwind's fair braking was down right poor for our big tires and 160,000
pounds. We got stopped, but only because of the thrust reversers.

This was the same night that SWA ran off the runway at MDW.

D.