Breaking Action Reports

cj610

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This latest band of weather passing through the midwest and northeast has me once again thinking about breaking action reports. Now before I go showing my ignorance, I should go look in my AIM to see if this stuff is there. But I'm to lazy for that and find that posting my question and getting my answer from this forum will be much easier.

Now I know we have a few different measures of breaking action. The first being nill,poor,fair and good. Which in my mind equates to very scared,little scared,not to scared and not scared at all.

Then we have MU (I'm not sure of the spelling) reading. I usually come across this at bigger airports. They give me this number which is suppose to be some friction index. It has been my experiene that below 30 is nill(very scared),30-35 is poor,35-45 is fair and 45 and above is good.

Now don't go using my numbers because I am probably wrong on this stuff anyway. Also w/ this friction index thing, I think it differs w/ type of aircraft. Some jets rely fully on their brakes for stopping whereas most turboprops can get it stopped on the runway using very little if any brakes.

Now all this stuff is leading to a question and I actually have many question on this subject. I guess what I hope, is that we can get a discussion going here so that I can finally get this stuff straight.

Here are some of the things I want to talk about:
1. What are the different types of breaking action reports(ie poor/good, MU reading, ...ect)?
2. What are the best way of getting the most current of these reports?
3. What are some of your experiences on icy runways?
 

tarp

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A.) Break - to smash, split, or divide into parts violently; reduce to pieces or fragments: He broke a vase.

B.) Brake - a device for slowing or stopping a vehicle or other moving mechanism by the absorption or transfer of the energy of momentum, usually by means of friction.

1.) Braking action reports such as good, fair, etc, come from landing aircraft and are subjective in nature. Mu meter reports are more scientific being taking by an airport vehicle dragging a meter behind it. When a Mu-meter goes below 40, it means the tire on the meter has begun to lose friction. AIM 4-3-8 and 4-3-9.

2.) The best reports are those made by airplanes that landed just before you did taking into account weight and type. A light weight Dornier Jet with no reversers and carbon fiber brakes will give a completely different report than a B-767 heavy.

3.) Ops specs prevent me from landing on NIL (makes sense!) and I have never had a problem with any of the other conditions. The anti-lock multi wheel systems on modern aircraft work great. Have more problems negotiating the turn off the runway than landing straight ahead.
 

avbug

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When it's bad, just remember to keep thrust symmetrical, and always slow to the point where you have to add power to taxi clear of the runway. Never roll off using energy from the landing. Always land and slow or roll until it takes extra power to clear the runway. That one little thing may save you a lot of grief, and you company many millions of dollars.
 

Speedtree

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I too was curious. as previously mentioned AIM 4-3-8 (9). There is no correlation between MU and the pilot reports of good, fair, poor, and nil. MU values are from 0-100 where 0 is the worst and 100 is the best. 40 is the value at which aircraft braking action begins to be affected. A note states that it depends on the type of friction measuring device also although no mention of types except it should be FAA approved and stated in the report. when 1/3 of the runway is 40 or less a report is supposed to be generated. I do not have much experience with this although we did land in wyoming last week and the braking action was probably fair with patchy snow and ice. I believe the MU reports were in the high 20s and 30s.

That's all I have to say about that.
 

avbug

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The primary difference is that braking action reports are a subjective "best guess," while runway friction coefficient is a calibrated standard for the given system in use.
 

jetdriven

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at airmidwest we are prohibited from landing on a runway that is reported "nil" from a similar aircraft. (baron size and up are ok, c152 with student pilot is not). we are also prohibited from taking off on a runway that, in the captains determination, is considered "nil" for his aircraft. tapley readings below .30 and MU meter readings below .20 are considered "nil"..
 

starchkr

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By all means DO NOT rely on braking reports more than 10 minutes old. I did once and almost ended up in the grass, through the fence, and in the neighborhood at the end of a runway in Little Rock. I will tell you one thing though, it only takes one time to learn a hard lesson, and i will never do that again.
 

bin LAAidoff

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at Brand X, we had a table, in the runway analysis book, corelating MU reports to the fair/poor/nil. AeroData was the company that produced the table. Where they got the data, I do not know, or if it was "calibrated" for type (737).

Might dig through your manuals somewhere, might have it...
 

Simon Says

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Amen, Avbug for stating that you better slow down enough on the runway so you need to add power to clear. There is nothing more that bugs me than people not slowing down adequetly before clearing.

Anyways about the braking action reports and MU. In our op specs we also put crosswind into the equation. For example for a runway reporting poor braking action you cannot exceed 5-10kts crosswind. For braking action good we can land in a 35kts crosswind. (although allowed to land very few people do in a 35kt crosswind.)
 

mar

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OpSpecs prohibit landing when 'nil'?

I'm joining this discussion a little late but I have a question about exactly where in the OpSpecs it prohibits anyone from landing when the braking action is reported as nil.

I've looked everywhere for some concrete regulation or stipulation and cannot find anything. Can someone cite chapter and verse?

Obviously it's not a good idea to land *or takeoff* when the braking action is nil. This is a good way to be found careless and reckless when you head for the weeds, but a couple of people seem to be convinced that it's written down somewhere. I'd like to know where.

By the way, there's one more reason (that no one has mentioned) not to operate when 'nil' is reported:

Engine failure on the takeoff roll at speeds too slow to have the rudder effective.:eek:
 

bin LAAidoff

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Brand X and Y manuals prohibited landing with breaking action "nil".

This was in our GOM, under Adverse Weather Operation, and perhaps a reference elsewhere (runway analysis? de-ice manual?)

Don't know that you would ever see it it the "OpSpecs" literally (faa issued, not company written), but I know many who collectively refer to GOM/Ops Manual as OpSpecs.

Hope that helps.
 
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