Reported Braking Action GOOD == DRY R/W ??

[lion-g]

Hi Guys,

I was trying to search for more information but to no avail. Just wanted to ask, especially guys flying in and out of Europe, how do you guys calculate the landing and takeoff performance IF only the braking action is reported?

For what I have gathered, Braking Action Good is not equivilent to DRY RW condition and neither it's the same as wet ... so if only braking action is reported, what do you guys assume when you do your calculation ?

Thanks in advance,
lion-g

[rudderrudderrat]

Hi,

I cheat and look out of the window.

[de facto]

I use braking action good in Qrh for wet runways to calculate landing distance.
If not sure,get the dry figure and multiply by 1.15.

[Denti]

The EFB program offers a selection of Dry, Wet, Slippery, Contaminated. If i choose slippery it offers various braking actions, one of them is Good. Sooo, if the runway is not reported wet i use slippery/good braking action for calculation, and if a look outta the window is reason for any doubt in that report i use a lower braking action value. Better to be safe than sorry.

[bfisk]

Braking action "good" only means that the friction coefficient (mu) is better that 0.40.

Depending on where you look, you will find different typical friction coefficients between rubber and concrete: Wikipedia says 1.00 (dry) and 0.30 (wet), while this site (http://hypertextbook.com/facts/2006/MatthewMichaels.shtml) quotes various sources between 0.60-0.85 (dry) and 0.25-0.75 (wet).

From my experience, grooved wet runways, ie uncontaminated but not dry, will have braking action good, that is to say better than 0.40. However, the fact that braking action is reported to be good, does not indicate that the runway is dry. The only way to know for sure before you get there, is to obtain information on the runway state. This is sometimes given by ATC automatically, by request, via ATIS or via SNOWTAM or MOTNE codes.

[STBYRUD]

In any case, to my knowledge the braking action is by definition always less than optimal if any is reported - I choose wet in my software, no way to select a braking action directly.

[Koan]

Generally dry means "dry". Or damp, with no mesureable depth of precipitation.

[safetypee]

lion-g I think what you are looking for is in ICAO Annex 14. AFAIK this applies to a wet runway or worse conditions, thus ‘good’ is not the same as a dry runway.
“If the surface is affected by snow or ice and the braking action is reported as “good”, pilots should not expect to find conditions as good as on a clean dry runway. The value “good” is a comparative value and is intended to mean that aeroplanes should not experience directional control or braking difficulties, especially when landing.”

Thus landing calculations should be based on ‘good’ wet performance, i.e. as per a dispatch factor of 1.92. However for an in-flight check before landing, the QRH landing data (assumed to be the basic unfactored distance or nearly the same) should be increased by a factor according to the reported conditions, and as required by operational regulation.
For EU-OPS 1 this is generally taken as using the departure factors which should provide adequate safety margin and thus meet the requirements of EU-OPS 1.400 – a safe landing (… the condition of the runway intended to be used should not prevent a safe approach, landing …).

However, note that wet conditions includes a range of reduced braking friction short of ‘contaminated’ which might initially be reported as ‘good’, but in reality turn out to be ‘medium’, thus checking the performance for these conditions would be a wise move and help prevent any ‘short final / on runway’ surprises.

de facto, some manufactures QRH data is similar to the basic unfactored landing distance which is unlikely to be achieved in operation, thus on a wet runway there may not be any safety margin at all. Even when factoring the data by 1.15, the distance might only equate to that which an average pilot might achieve with an accurate touchdown and max braking; there would be little or no safety margin for error, etc.
Also there could be many unknowns;- runway surface texture, tyre condition, late change of wind, etc; and beware PIREPS, they may not match your aircraft type / operation / judgment.

Winter Operations | Flight Operations | Safety Regulation (http://www.caa.co.uk/default.aspx?catid=1428&pagetype=90&pageid=8169) ‘Winter Operations’

Note UK latest info: http://www.caa.co.uk/docs/33/srg_asd_NOTAL201009.pdf
and
http://www.ead.eurocontrol.int/eadbasic/pamslight-6F6B3199B23109BC790F635B1CF28D96/7FE5QZZF3FXUS/EN/AIP/AD/EG_AD_1_1_en_2010-12-16.pdf

UK AIP 1.1.2. para 5 Assessment and Notification of Runway Surface and Allied Conditions.
AD1-1
see para 5.4.5, AD 1-2

NATS | AIS - Home (http://www.nats-uk.ead-it.com/public/index.php.html)
select: UK Aeronautical Information Publication (AIP)
select: Aerodrome Information Generic
choose: AD 1-1 or AD 1-2

[9.G]

At the moment the industry doesn't have a uniform standards for assessing the RWY conditions causing lots of confusion and misjudgments based on potential misinterpretations of available info. FAA once again has a head-on approach to that and developed a so called TALPA concept supposedly to be implemented in mid 2011. Here's the link EASA - European Aviation Safety Agency (http://www.easa.europa.eu/.../Report%20Volume%201%20-%20Summary%20of%20findings%20and%20recommendations.pdf) :ok:

[lion-g]

Hi guys,

Thank you so much for the reply. Was stuck in LHR for a while.

Merry Christmas and a happy new year.

Cheers,
lion-g

[HEATHROW DIRECTOR]

UK airfields do not report braking action and have not done so for many years.

See: http://www.pprune.org/atc-issues/437257-caa-disallowing-braking-action-reports.html

[9.G]

That explains among the others the jam at the airports in the UK...

[PENKO]

I cannot insert ANY braking action in my landing distance calculations. I could on the 737, I can't on the Airbus. So if BA is reported medium, I have no way of knowing exactly what my landing distance will be. I can insert the contamination (compacted snow, wet snow, icy) but that's about it.

So what do I do when there is fresh snow on the rwy, BA medium?
Depends on the day and what I see and hear, which is no professional way to do aviation, but what else can I do?

[9.G]

PENKO, as mentioned before that's the current dilema of the industry there's no common concept of the RWY conditions assessment and reporting to the PIC. Each and every state choses it's own methods based mostly on liability criterion. At the moment, unless you have the LPC software enabling one to use the TALPA ARC conversion table, the only way to reliably assess the landing performance is to get it from the performance engineer department using approved software. Nowadays can be done easily via ACARS.:ok:

[PENKO]

ACARS, well, I'll hold another 45 minutes untill they come up with a reply ;)

[safetypee]

Airbus publishes contaminated performance data relating to contaminant coverage, type, depth, and extent for each third of the runway. This is usually provided by UK airports – see CAA refs # 8. You should be able to enter the Airbus performance data with this information to get the required aircraft performance.

Updated links to UK AIP re # 8, reports in AD 1-2

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select: Aerodrome Information Generic
choose: AD 1-1 or AD 1-2

[maxed_out]

This is what I do.

If BA-good and water equivalent depth is less than 3mm :
fc >0.40 use table for wet rwy
fc < 0.40 use table for slippery runway, F.c or what you might call it

Water equivalent depth more than 3 mm, use table for actual contamination.

If BA is reported and chemicals on the rwy I never use tables for dry rwy even if the rwy is grooved. I go safeside.

As someone pointed out this is sometimes hazy in companies. Generally the provider of the performance charts/program should state how to go about it but it is often left out. Good thing this is not an issue of great importance:uhoh:?

[XPMorten]

From a 737 manual

http://www.xplanefreeware.net/morten/DOCS/Braking.png

[kasperl]

"Thus landing calculations should be based on ‘good’ wet performance, i.e. as per a dispatch factor of 1.92. However for an in-flight check before landing, the QRH landing data (assumed to be the basic unfactored distance or nearly the same) should be increased by a factor according to the reported conditions, and as required by operational regulation.
For EU-OPS 1 this is generally taken as using the departure factors which should provide adequate safety margin and thus meet the requirements of EU-OPS 1.400 – a safe landing (… the condition of the runway intended to be used should not prevent a safe approach, landing …)."

JAA operators´ flight crews presently do not have to apply safety factors when checking the landing performance in flight!!!
That means you are perfectly legal, even on slippery(a runway is defined as slippery when BA reported GOOD!)/contaminated runways, if your actual landing distance equals the LDA.
The FAA presently requires an in-flight safety factor of 1.15 for normal landings on all types of surfaces beside the same dispatch requirements as required by the JAA.

merry christmas...

[9.G]

Kasperl,
merry Xmas to you too mate. Under EU-OPS regulation, at time of dispatch the Landing Distance Available for contaminated runway at destination must be at least 115% of the ALD for contaminated runway, and never less than the RLD for a wet runway. So it's whichever greater not just wet RWY performance. Credit for reverse thrust use is allowed at time of dispatch. Note that under FAR 121, dispatch to runways reported as “wet or slippery” at destination is made based on wet runway aircraft performance only.
It's worthwhile to mention that those distances are computed in accordance with the regulatory requirements as per EASA CS25.1591 meaning ALD is computed with air distance = 7 sec with 7% speed decay from VLS, sea level no wind (corrections available)and ground roll as per EASA CS25.1591 taking into account the contaminant drag. IOW it's a perfect test pilot landing with about 400 ft/min ROD till touchdown + immediate max brake pressure application assuming equal contaminant distribution.

The landing distances that Airbus publishes in the operational documentation for in flight reference are in fact the same as those defined by regulation as the basis upon which additional margins are added for the dispatch requirements. Because of the large regulatory dispatch factors, these distances constitute the maximum aircraft performance capability demonstrated with specific flight test techniques and are therefore not an adequate representation of a realistic aircraft performance capability achievable by a line pilot. Airbus has in the past recommended in training material, that the distances published for automatic landing with auto-brake should be used to determine realistically achievable landing distances, both when an automatic landing and when a manual landing is planned.
Let's see a practical example:
AD sea level and ISA A 330 LW 170 Tonnes both reversers operative Flaps Full NO auto brake contamination slush more than 3 mm.

ALD: 1630m+8% Vapp increment- 7% reversers credit= 1646m (perfect test pilot landing)
RLD wet: 1905m (factored perfect test pilot landing)
ALD for AUTO LAND with AUTO BRAKE MEDIUM: 2110 -9% for reversers= 1920m (somewhat realistic performance)

As you can see all distances are different and that's the reason why next year the regulators will introduce a common concept of operational landing distance which reflects more or less a realistic average pilot performance based on actual tests and additional safety margins. I still would strongly encourage to assess carefully the landing performance as you'll never fly in the perfect world with test pilot performance. :ok: