Contaminated rwys

[Snowonice]

How much of the landing distance available can a pilot use as stopping distance when landing his 737 on a snowcovered (contaminated)runway?
What kind of rules and regulations must be adhered to?

[JB007]

Knew that ATPL JAR-OPS exam would come in useful for something:

If the runway is expected to be contaminated at the time of arrival the landing distance must be increased by a factor of 1.15.

If the A/c manual gives additional info on landing on contaminated runways, this may be used if it gives a lesser distance from that above.

This is irrelavant of A/c type.

[john_tullamarine]

Snowonice,

There have been a few threads in the Tech Forum on this problem.

The 15 per cent fudge factor traditionally has addressed the simple wet (not flooded) runway case and, for that matter, operations on gravel using seal data.

For flooded or ice/snow/slush contamination it all gets a whole lot more complex and the approaches adopted in trying to allow for the imprecision of rolling and braking data in the real world scenarios lead to an interesting variety of engineering guesswork.

[no sig]

Not to mention the fundamental requirement of an adequate braking co-efficient.

[Snowonice]

Thank you gentlemen , I will be more specific: As far as I know there is no AFM data from Boeing concerning stopping distances on contaminated rwys. There is advisory data issued in the QRH describing stopping distances on different braking actions (good , medium and poor) for a specific landing weight.
When using these data (+ 15% ) do a commander have to stop within 60 % of LDA?(JAR-OPS 1.520)

[john_tullamarine]

Snowonice,

If your particular AFM doesn't give you the data you seek, try the relevant Boeing performance programme or approach Boeing Customer Support for more data.

I might be looking at a different 737 QRH here but, subject to that caveat, my conservative view is that one ought to treat unfactored data with extreme caution. I suggest that unfactored means, in effect, routinely unachievable and needs to be factored by the pilot in any case for comparative assessment of emergency strategies.

For instance, a reasonable approach for landing distance assessment is to assess the conditions (ie select the table) conservatively (keeping in mind that one's assessment is at best a guess) and then factor the resulting unfactored distance by 43 percent and 67 percent (call it 50 and 70 for ease of calculations) which gives data bearing some relation to the (in some jurisdictions valid) alternate and the normal destination landing distances.

If the pilot has an available distance in excess of the highest figure, then the operation is akin to a normal landing, if between the highest and the middle figures, then the landing ought to be treated with considerable caution and care and, if between the middle and unfactored figures, then the landing becomes an emergency situation with a heightened risk of runway excursion. If the available distance is less than the unfactored, then one ought to anticipate a guaranteed overrun.

Perhaps with luck we might get Mutt's observations on this as he has lots of good gen on contaminated runways ....

Do keep in mind that the certification data in the AFM are determined for artificially structured circumstances which may not be reflected in the real world case at the time the pilot has to make his decision ...

I suggest that the 15 percent factor only is appropriate for using normal dry data in wet (not flooded) conditions.

[ 10 January 2002: Message edited by: john_tullamarine ]</p>

[mutt]

snowonice

FAA regulations do not require aircraft manufacturers to account for contaminated runways, therefore this data is not contained in the AFM. Boeing does supply limited data in the operations manual and the QRH. This data comes in two forms, one is “planned landing” distance and the other is “actual landing” distance.

The QRH charts are usually “actual landing” distances for use in flight, they do not account for the 60/40 rule and should be corrected accordingly prior to flight. Once you are in flight you can theoretically use these landing distances without correction. But as John_Tullamarine has explained, you must treat unfactored landing distances with extreme caution; they are seldom achievable in normal airline operations.

Mutt <img src="smile.gif" border="0">

[john_tullamarine]

Having been involved in certification takeoff and landing flight test in years gone past, and certification generally, my attitude is that anything published and claiming to be unfactored effectively means, for the line pilot, unable to be achieved. My comment ought to be viewed in terms of the data becoming a limiting boundary condition ... hence my preference to get students to apply the normal factors as part of their assessment and decision-making processes when it comes to weighing up to which runway does one divert ...

If my position is a little conservative, so be it.

I think that it would be very hard to argue the toss at the Inquiry after an overrun on the basis that the book said the distance available was the unfactored distance required.

Different matter, of course, if the pilot is faced with an emergency requiring an urgent landing and there is no alternative runway available and that runway was the reasonably assessed best option.

[zeroG]

snowonice.
I think I see your point. As a captain on a 737 in scandinavia, I have been scared more than once - stopping far down a rwy embedded in a huge ball of snow from thundering reversers.
The 60% rule for stopping at dest. are the same both in JAR OPS and FAA FAR for dispatch ( as far as I can understand).
FAR § 125.195 are easy to read, but the original text in JAR OPS throws me off.
Doing an actual landing at dest.:
- are we required to still stop within 60%, or can we skid to the end when it is wet or slippery? (that is - normal landing 50 feet above threshold and 305 meters in and 15% added).
In our airline we are allowed (and certified)to use the whole rwy for ACTUAL landings. The 60% rule are only used for dispatch. Taken into account that braking action numbers are far less than scientific - we are sometimes left with very small margins. A few mental sensors tells me it might not be correct.
How do you other guys operate??

[john_tullamarine]

ZeroG,

I'm amazed that you have been frightened only infrequently .....

[zeroG]

to john_tullamarine first.

Indeed, it may not only be infrequently. If you think our operations are strange, I would like to have a beer with you. Thanks for your answers.

Snowonice.
As I didn't have an answer to your question, I might have stepped on you a bit by just giving your question a different angle.
BUT. I was glad when you opened this topic.
We operate down to 1600 m.(5300') rwy's in dark-cold-windy-icy-snowy conditions. THEREFORE our CAA has certified our operations to NOT stop within 60% of LDA for an actual landing.
Our actual stopping distance (+ 15%) are not to exceed LDA. That's it.
Just as you, I would like to hear from any wizard out there who can tell if that is the correct interpretation of JAR- OPS 1.520.
It may be, but it is no fun.

[john_tullamarine]

.. but, no doubt, you do a carrier approach .. not one knot fast, no/minimal flare, max autobrake, lots of noise from the reversers ? ... with your heart in your mouth every time ? .. and a mandatory missed approach from the flare if you are not on the ground by, say, 1200 feet in from the end ?

I would hate to be responsible for your maintenance cost centre and can only speculate as to the insurance premiums for such an approach to the commercial realities of a nasty runway environment.

If your operator has negotiated it with the relevant authority then one presumes that they have built some fat into the process ... definitely a sweaty way to make a quid for the crew .... and if 15 per is the only fat, then ... rather you than me.

[ 13 January 2002: Message edited by: john_tullamarine ]</p>

[mutt]

ZeroG,

My interruption of JAR-OPS is as follows:

You are required to Plan to land in 60% of the available runway, JAR-OPS 1.515. The available runway is then increased by 15% for a wet or contaminated runway and becomes the minimum distance that you can plan to land on. (JAR-OPS 1.520)

For ACTUAL landing you can use the whole runway and are no longer limited by the requirement to stop within 60%.

This is exactly as you have stated In our airline we are allowed (and certified)to use the whole rwy for ACTUAL landings. The 60% rule are only used for dispatch So you are following the regs.

The rest of JAR-OPS 1.520 goes on to explain that you can use manufacturers data approved by your regulatory agency provided that the required runway length isn’t any shorter than the required dry runway +15%.

I just downloaded JAR-OPS off the internet to answer this question, so someone else might want to add something.

Mutt. <img src="smile.gif" border="0">

[zeroG]

john_tullamarine 12/01.

In short - YES. Except that the carrier boys have one big advantage, they are already at 100% power if they miss the last wire. We are committed when the reversers are out. In Breaking Action We Trust. I confess I miss the drag shute and the hook for the barrier.
But then again. Our safety record doing this is world class.

mutt

Thank you.
On my part I think I'm satisfied.