Runway Friction Index

Capt.Doug wrote:
"Icebound" wrote in message WHY would not the US adopt it?


The US already has a system?

The big airports can provide runway traction reports measured in 'Mu'. These
reports are much more useful than pilot reports.

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.

Friction is a variable, a wheel has friction in the wheel
bearing and on the tread to the pavement. The pavement when
clean and dry has a fairly stable Mu which is a coefficient
from perfect friction to no friction.

If there is water or ice, the actual friction may change
second by second as the temperature changes or more
precipitation falls.

It would be nice if somebody built a runway 3,000x24,000
feet with a Teflon surface so pilots could practice
controlled landings. How slick is oiled Teflon?


--
James H. Macklin
ATP,CFI,A&P

--
The people think the Constitution protects their rights;
But government sees it as an obstacle to be overcome.
some support
http://www.usdoj.gov/olc/secondamendment2.htm
See http://www.fija.org/ more about your rights and duties.


"Newps" wrote in message
...
|
|
| Capt.Doug wrote:
| "Icebound" wrote in message WHY would not the US
adopt it?
|
|
| The US already has a system?
|
| The big airports can provide runway traction reports
measured in 'Mu'. These
| reports are much more useful than pilot reports.
|
| 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.

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.

I've never heard of mu numbers in this context. How are they used?

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

They give us three numbers, such as 33 35 38, for the thirds of the
runway. It was an attempt a few years ago to standardize the runway
condition so the number means the same thing to everybody and removes
the subjectiveness of braking action fair. It is so useless we don't
put it on the ATIS anymore and when we get asked for the runway
condition we give it to them in the old way, good, fair, etc. Nobody
ever asks for the mu number. Ever.



Jose wrote:
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.


I've never heard of mu numbers in this context. How are they used?

Jose

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.