Mu 35 Runway 34 via #$%&?

[sorrygottarunway]

I hear this on the ATIS quite a bit, and as a captain now I'm sometimes embarrassed to ask certain questions, as "I should know this by now." Its not in the book, and this one I can't even google, because I don't know how its even spelled!

"mu for runway 34, 35-40 as reported by a capply."

Tapply?
Caplink?
Cabby?

I am sure its referring to the airport ops SUV driving at breakneck speed down the runway, but what is it?

[Ian J]

"As reported by county vehicle," I'm guessing you heard.

[SteveC]

Stole from a government site:

1. Name of Item

Braking Action

2. Description of Item

Braking Action Coefficient of Friction. The ratio of the tangential force needed to maintain uniform relative motion between two contacting surfaces (aircraft tires to the pavement surface) to the perpendicular force holding them in contact (distributed aircraft weight to the aircraft tire area). The coefficient is denoted by the Greek letter Mu. It is a simple means used to quantify the relative slipperiness of pavement surfaces. Friction values range from zero to 100 where zero is the lowest friction value and 100 is the maximum friction value obtainable.

3. Benefits

Accurate, frequent, and timely reports of braking action contribute to the safety of flight. FAR 121.601 (a) (c) require that the aircraft dispatcher apprise the pilot in command of conditions and keep the pilot updated when changes occur. The tower Air Traffic Controller is also required to provide the pilot with braking action advisories. Individual airlines obtain braking action reports and maintain them in their own field condition reporting systems. The timely transmittal of braking action information among the airlines would enhance the safety of flight. Every winter season air carrier aircraft encounter runway conditions that lead to incidents.

4. Source of the Data

Braking action data is gathered either from a pilot or a ground source. Reports from a ground source are communicated to the ATC tower which then has the responsibility to advise aircraft. ATC may also solicit braking action reports from inbound flights. Pilot braking action reports as well as MU meter reports may be stored in each airline's data base.

5. Nature of the Data

Pilot braking action reports include the aircraft time, the runway or other airport surface, the time, and the reported condition. Pilot braking action reports are subjective. Airport ground source reports are reported in Mu meter readings or as RCR readings or pilot reports of Good, Fair, Poor, or Nil.
Mu-meter and RCR decelerometer reportsare numeric and come from the airport authorities. Pilot reports are subjective and based on braking action experienced by that pilot in that type of aircraft.







Mu-meter Readings.40 and above = Good
.36 to .39 = Ice and Snow Fair to Good
.30 to .35 = Ice and Snow Fair
.26 to .29 = Ice and Snow Fair to Poor
.25 and below = Ice and Snow Poor
.30 to .39 = Water and Slush Fair
.29 and below = Water and Slush Poor





RCR Readings
5 and Below = Nil
6 to 12 = Fair to Poor
13 to 18 = Fair
19 to 23 = Fair to Good
24 and above = Good

Pilot Reports

BRAG = Good
BRAF = Fair
BRAP = Poor
BRAN = nil

[sorrygottarunway]

Originally Posted by Ian J

"As reported by county vehicle," I'm guessing you heard.

I swear it sounds like capply. Its like he goes into micro-machines voice when he says it

recording here: phone 607-729-8335

[Milesar]

Originally Posted by sorrygottarunway

I swear it sounds like capply. Its like he goes into micro-machines voice when he says it

recording here: phone 607-729-8335

Doesn't sound like county vehicle, I would think it would be something like SteveC posted as he said it was "35". Capply? I could hear it too.

[qflyer]

It's Tapley...

"The Mechanical Tapley Meter

is a small pendulum-based decelerometer that consists of
a dynamically calibrated oil-damped pendulum in a sealed housing. The pendulum is
magnetically linked to a lightweight gear mechanism to which is attached a
circumferential scale that shows values as percentage of g, 1 g = 32.2 ft/sec2. A
lightweight ratchet retains the maximum scale deflection reached upon completion of a
test. The mechanism is enclosed in an aluminum case and the scale is covered with a
glass face. The whole assemble is mounted in a cast-base plate by means of a fork
assembly, Each meter is statically tested and dynamically calibrated before being issued a
calibration certificate. When the meter is used in a fiction survey, it is placed on the floor
of the vehicle. The data have to be visually read and recorded by the operator.

The Electronic Tapley Airfield Friction Meter

provides a recording of the data taken
during a fiction survey, including averages for each segment (one third) of the runway.
The meter is a pendulum-activated, semi-automatic, recording decelerometer, and it
operates on the same principles as the original Tapley Mechanical decelerometer. When
preparing to conduct a friction survey, the operator places the meter on the floor of the
test vehicle. The actuating pad is fitted to the brake pedal, and the command module is
attached to the vehicle window by a suction pad in front of the driver’s side or at another
suitable location that is readily visible to the operator. The power leads are connected
either to the vehicle battery or to a separate battery. The equipment is now ready for
testing the runway. These devices should only be used on runway surfaces covered with

4

ice and/or compacted snow, because, under dry and most wet-runway conditions, RCR
vehicle wheel lockup becomes inconsistent and vehicle stability is degraded.

[SteveC]

Maybe "Tapley"?

More information here. Here's a snippet:

The Mechanical Tapley Meter is a small pendulum-based decelerometer that consists of
a dynamically calibrated oil-damped pendulum in a sealed housing. The pendulum is
magnetically linked to a lightweight gear mechanism to which is attached a
circumferential scale that shows values as percentage of g, 1 g = 32.2 ft/sec2. A
lightweight ratchet retains the maximum scale deflection reached upon completion of a
test. The mechanism is enclosed in an aluminum case and the scale is covered with a
glass face. The whole assemble is mounted in a cast-base plate by means of a fork
assembly, Each meter is statically tested and dynamically calibrated before being issued a
calibration certificate. When the meter is used in a fiction survey, it is placed on the floor
of the vehicle. The data have to be visually read and recorded by the operator.

The Electronic Tapley Airfield Friction Meter provides a recording of the data taken
during a fiction survey, including averages for each segment (one third) of the runway.
The meter is a pendulum-activated, semi-automatic, recording decelerometer, and it
operates on the same principles as the original Tapley Mechanical decelerometer. When
preparing to conduct a friction survey, the operator places the meter on the floor of the
test vehicle. The actuating pad is fitted to the brake pedal, and the command module is
attached to the vehicle window by a suction pad in front of the driver’s side or at another
suitable location that is readily visible to the operator. The power leads are connected
either to the vehicle battery or to a separate battery. The equipment is now ready for
testing the runway. These devices should only be used on runway surfaces covered with
4
ice and/or compacted snow, because, under dry and most wet-runway conditions, RCR
vehicle wheel lockup becomes inconsistent and vehicle stability is degraded.

[SteveC]

Holy cow. Looks like we found the same source...

[Swen]

BOW Bowmonk Decelerometer (Bowmonk Sales) BRD Brakementer-Dynometer ERD Electronic Recording Decelerometer (Bowmonk) GRT Griptester (Findlay, Irvine, LTD) MUM Mark 4 Mu Meter (Bison Instruments, Inc.) RFT Runway friction tester (K.J. LAW Engineers) SFH Surface friction tester (high pressure tire) (SAAB, Airport Surface Friction Tester AB) SFL Surface friction tester (low pressure tire) (SAAB, Airport Surface Friction Tester AB) SKH Skiddometer (high pressure tire)(AEC, Airport Equipment Co.) SKL Skiddometer (low pressure tire) (AEC, Airport Equipment Co.) TAP Tapley Decelerometer (Tapley Sales) VER Vericom (VC3000)

Could they have said Tapley?

[Swen]

Doh!

I'll have to settle for the bronze.

[sorrygottarunway]

Thanks guys. I love this website!

[Seggy]

NEVER EVER EVER trust the braking action reports.

No guarantee the meter is working properly or an airport operations department is a little to anxious to have an airplane land.

[OldTownPilot]

Yep, the braking action is always 'poor'

[minitour]

Originally Posted by Ian J

"As reported by county vehicle," I'm guessing you heard.

I think "MU" is latin for "drunk redneck in pickup truck", is it not?

-mini

[mikecweb]

Yeah we've also had to go around because an airplane reported nil braking yet was able to turn off just past midfield. The only time nil braking should be reported is when you slide of the end of the runway.

[Ian J]

Landing at BDL right before they closed the airport for icing the other night I wanted to report the braking action as "exciting."

[minitour]

Originally Posted by mikecweb

Yeah we've also had to go around because an airplane reported nil braking yet was able to turn off just past midfield. The only time nil braking should be reported is when you slide of the end of the runway.

What don't people understand about that? Why is it so hard?

I also like "We're getting a trace of light rime here..." Which is it?

-mini

[skyrunner1500]

Originally Posted by Seggy

NEVER EVER EVER trust the braking action reports.

No guarantee the meter is working properly or an airport operations department is a little to anxious to have an airplane land.

And if it comes to Russia and Belarus operations they code everything different.
An ICAO FC of 0.30 is medium, whereas the Russian so-called "normative FC" of 0.30 is less then poor...

[sorrygottarunway]

In soviet Russia, braking action stop YOU!