Does SAFO 06012 trump FAR 135.385?

[somewhereupthere]

Conditions are as follows:

Contaminated runway
Wet Snow
Braking Action Poor
Unfactored landing distance of 2500 without use of reversers (published data for my plane assumes no reversers)

I take 2500 * 1.667 which = 4,167.5'

Because I don't have reverse thrust: 4167.5 * 1.2 = 5,001'

Finally, 5,001' * 1.6 = 8,001.6', or 8,002' factored landing distance.

So this factored landing distance must now be 60% (to comply with 135.385) of the available runway, or 13,337'?

Am I interpreting this correctly?

For my airplane, at max landing weight, the 135 DRY factored distance is 4100', still assuming no reversers.

So 4100 * 1.2(no reverse) * 1.6 = 7872 / .6 = 13120

So do I need 13120' of effective runway available to land with these conditions?

A 15% margin is already built into the contaminated factored numbers for the SAFO.

So my factored distance is now 7872, or let's just call it 7900. This then has to abide by 135.385 and be within 60% of the available effective length correct? Well, 7900/ 0.6 = 13167', or let's call it 13,200'.

So am I safe to assume that legally all I need is 4100 + 15% (4715'), making a landing distance available length of 7860' (4715 / .6)?

Or, to avoid a "reckless" operation claim, I should operate at a 7900' LDA / 0.6 and make the total runway needed 13200'?

 

[SFLAX]

With the above conditions, I would not even go, so no need to figure it out. But 13,000 sounds right if I was willing to risk my life and certificate.

 

[SFLAX]

And FAR will trump a SAFO, but your ops specs will determine how to calculate. What that SAFO is saying, is that the data from the manufacture is rough at best and they admit it was done under perfect conditions and you can not 100% rely on it as you are not going into perfect conditions.

 

[SrFnFly227]

If the published data for your plane assumes no reversers, why are you taking the .2 hit for no reversers?

And maybe I'm missing something (I haven't had my coffee yet and I have a newborn at home keeping us from sleeping at night), but why are you factoring your numbers twice? Unfactored landing distance is your distance to stop. Unfactored landing distance is what needs to be 60% of your available runway. Factored landing distance has already done the 60% math for you and is giving you your runway required.

 

[SrFnFly227]

After reading through this again, I'm almost positive that you're doing this wrong. It still looks to me like your double factoring.

Your unfactored, dry landing distance = 2500.

2500 x whatever your contaminated correction is = Your stopping distance.

Your stopping distance / 0.6 = Your factored landing distance.

Your factored landing distance = Your runway required.

 

[gotWXdagain]

There is only a small number public use airports in the united states with runways over 13,000'. So unless you are flying some combination of DEN, ABQ, JFK, LAS, CSM, MWH, COS, AMA, DFW, YUM, and VCV, you are illegal. Something about that does not make sense.

 

[Itchy]

Makes perfect sense to me. ...




if you're flying a space shuttle.

 

[Boskru]

I agree, I believe that you're adding an extra step or two. The reversers are not considered so they don't need to be compensated for.

Unfactored of 2500 needs to be "factored" by the conditions (snow, wind, elevation, etc) and then divided by .60.

For your DRY example (no winds). 4100 /.60 = 6833. That is your 135 factored landing distance and the minimum runway required.

This can get very confusing, but I'm sure your chief pilot would be willing to sit down and review things for you. I have to do thing like that from time to time when I over-think things in my head.

 

[Deleted member 27505]

Conditions are as follows:

Contaminated runway
Wet Snow
Braking Action Poor
Unfactored landing distance of 2500 without use of reversers (published data for my plane assumes no reversers)

I take 2500 * 1.667 which = 4,167.5'

Because I don't have reverse thrust: 4167.5 * 1.2 = 5,001'

Finally, 5,001' * 1.6 = 8,001.6', or 8,002' factored landing distance.

So this factored landing distance must now be 60% (to comply with 135.385) of the available runway, or 13,337'?

Am I interpreting this correctly?

For my airplane, at max landing weight, the 135 DRY factored distance is 4100', still assuming no reversers.

So 4100 * 1.2(no reverse) * 1.6 = 7872 / .6 = 13120

So do I need 13120' of effective runway available to land with these conditions?

A 15% margin is already built into the contaminated factored numbers for the SAFO.

So my factored distance is now 7872, or let's just call it 7900. This then has to abide by 135.385 and be within 60% of the available effective length correct? Well, 7900/ 0.6 = 13167', or let's call it 13,200'.

So am I safe to assume that legally all I need is 4100 + 15% (4715'), making a landing distance available length of 7860' (4715 / .6)?

Or, to avoid a "reckless" operation claim, I should operate at a 7900' LDA / 0.6 and make the total runway needed 13200'?

You're double factoring methinks.
1. Calculate unfactored landing distance for wet, icy runway... don't add anything for reversers if book landing distance is calculated without them (this should actually give you a modicum of "warm and fuzzy" 'cause you know with TRs you're gonna stop quicker than advertised.
2. If that number comes out to, say 2500ft, just divide that by .60. In this case that would be 4166ft. Now compare that number to your actual landing runway. Is the runway at least 4166ft?
3. You're done.
4. Somebody check my logic and math, but I'm pretty sure you're overdoing your numbers. If you're ending up with distances over ~7000ft, you can be pretty confident you're calculating incorrectly. In the words of high school math teachers around the world, "reality check your answer". I mean, you ended up with a 13000ft required distance. How many 13000 ft runways are there in the world?

 

[PhilosopherPilot]

Here are (a few of) our contaminated runway landing distance charts.
For my airplane at the max landing weight of 97,000 lbs it is possible to get distances over 13,000 feet, but that's on an icy runway with flaps 5. If you land flaps full, which is required on a contaminated runway unless operationally necessary to NOT land flaps full, it is in the 11,000 ft range for an icy runway. See both charts below.

1 inch of wet snow gives you a max manual braking distance of 6370 feet. High Auto Brakes is 6850 feet.

 

[Inverted25]

You need to tell your company to get ipreflight on your EFB Opspecs. Takes the guess work out

 

[Autothrust Blue]

Here are (a few of) our contaminated runway landing distance charts.
For my airplane at the max landing weight of 97,000 lbs it is possible to get distances over 13,000 feet, but that's on an icy runway with flaps 5. If you land flaps full, which is required on a contaminated runway unless operationally necessary to NOT land flaps full, it is in the 11,000 ft range for an icy runway. See both charts below.

1 inch of wet snow gives you a max manual braking distance of 6370 feet. High Auto Brakes is 6850 feet.

View attachment 33284View attachment 33285

I was going to throw in and say, we need "I forget but large" (like, in excess of 10,000) feet for FLAP 5 and really nasty contamination.

 

[somewhereupthere]

Thank you everyone for the replies. I've found the information to very helpful and informative, as well as clarifying. I think @Crop Duster has it right in saying to "reality check the answer." The reason why is that when I flew this same plane Part 91, we would use 2x the 135 factored DRY distance if we were landing on a winter runway. So in our case, 2x 135 DRY = 8200'

That was the general rule of thumb for us, and we never really found ourselves landing on runways shorter than that anyway. The interesting thing is that the only numbers published for us are dry unfactored numbers (pre Part 25)

This always seemed to work out nicely for us.

Also, @SrFnFly227 I am taking the additional .2 hit because the SAFO says the factor is based on use of reversers. Our AFM numbers are based on not having them. So I assume I have to take the .2 penalty.

Either way, I think it's just an extra margin.

Your unfactored, dry landing distance = 2500.

2500 x whatever your contaminated correction is = Your stopping distance.

Your stopping distance / 0.6 = Your factored landing distance.

Your factored landing distance = Your runway required.

BUT...

To use unfactored dry runway landing distances, first multiply the unfactored dry runway landing distance by 1.667 to get the factored dry runway landing distance before entering Table 2 above

So here is where I am:

Multiply the unfactored dry runway landing distance by 1.667: 2500 * 1.667 = 4168
No TRs factor: 4167.5 * 1.2 = 5002
Poor braking action factor/Wet snow, slush, standing water, ice: 5001 * 1.6 = 8003
Your stopping distance / 0.6: 8003 / 0.6 = 13339

Personally, it would make more sense to do the following:
Dry unfactored runway landing distance, No TRs factor: 2500 * 1.2 = 3000
Poor braking action factor/Wet snow, slush, standing water, ice: 3000 * 1.6 = 4800
Your stopping distance / 0.6: 4800 / 0.6 = 8000