135.385 Landing Distance

[osy007]

And how do you even find a thread that began 2 years ago. Talk about digging through some 'ol shee-ite.

 

[Excel'n]

It may be the case, but the division is the correct way to do it. 0.6 comes from the FARs that state 60%. 60% is 60 out of 100 or 6/10 or 0.6. Multiplying by 1.67 is not quite the same, and yields a slightly higher number than dividing by 0.6

So after two additional years, do we agree yet that 1/.6 = 1X1.67? OK, for starcheckdriver, that's actually 1.66666666666666666 etc.

 

[osy007]

Starcheckdriver is correct..

 

[osy007]

This is one of the most misunderstood aspects in 135 flying. Everyone thinks you factor the landing distance given in your AFM. Actually you factor the runway.

Example:5000ft rwy X .60=3000ft required. If your AFM landing distance is 3000 or less you meet the 60% rule. Most people look at the landing distance and multiply it by 1.6. end quote}

In this example, 8900.1 gives an example on how to factor in th 60%.

4)Runway conditions (including contamination). Runway features, such as slope and surface composition, can cause the actual landing distance to be longer than the calculated landing distance. Wet or slippery runways may preclude reductions from being taken and, in fact, require 115 percent of the distance derived from calculations, whether a reduction was used or not. This distance is calculated by increasing the distance required under dry conditions by an additional 15 percent (i.e., if Aircraft Flight Manual (AFM) data shows the actual landing distance will be 2,000 feet, the effective runway length required is 3,334 feet using 60 percent in this example. If the runway is expected to be wet or slippery upon arrival, the effective runway length required is 3,834 feet). Braking action always impacts the landing distance required as it deteriorates. Always consider the most current braking action report and the likelihood of an update prior to the flight’s arrival at a particular airport.

In their example, they factor the AFM numbers and not the runway. This is the way I have been doing this for years.

By using this example, you would not divide the runway legnth by .6, but the AFM numbers.

Who is correct?

 

[ABurgh]

I've always factored the AFM numbers as well, not the runway (divide the AFM number by .6).

And from the example in 8900.1, it looks like that is the correct way to do it.

 

[Excel'n]

Starcheckdriver is correct..

Gee, that quote is the same line I used for my first post to this thread. Mobie suggested and I clarified the simple mathematical fact that 'one divided by point six is the same as one times one point six seven' (rounded of course). This must be one of those "new math" anomalies.

 

[Corp Pilot]

osy007 "And how do you even find a thread that began 2 years ago. Talk about digging through some 'ol shee-ite."
Answer- On 5/24/2008 CFIIer and 5/25/2008 B737Dvr replied to post bringing it to the top of the list. Kinda thought you might figure that one out by yourself. Guess I was wrong.

osy007 "Took him 2 years to find the answer that someone else already answered...lol"
Comment- Guess I missed the previous post (and I am sure you can point it out) which answered the original question by locating the FAA reference which in part states "the airplane must only be able to land on the effective runway length as shown in the flight manual performance data."

Original question posted by Star Checker (2 years ago)
What does everyone think/do in their operation? Do they use it for planning only? Or, do you abide by upon arrival, even it means landing on a less favorable runway for wind purposes?


135.385 in all its glory refers to planning and does not prohibit you from landing with less than 60%/80% in accordance with FSIMs. My post of 5/26/2008 provides not my opinion, but the facts as documented by the FAA.

I apologize to those that I have confused or caused undue stress.

 

[GREAT LAKES]

135 Landing Distances

Here is my 02 cents:

Pre-takeoff planning:
AFM numbers X1.67 (per SAFO below)
Then multiply by the following Factors:




Runway Condition Reported Braking
Action
Factor to apply to
(factored) dry runway
landing distance*
Wet Runway, Dry Snow Good 0.9
Packed or Compacted Snow Fair/Medium 1.2
Wet snow, slush, standing water, ice Poor 1.6
Wet ice Nil Landing is prohibited
Table 2. Multiplication factors to apply to the factored dry runway landing distances when
the data for the specified runway condition are unavailable.
* The factored dry runway landing distances for use with Table 2 must be based on landing
within a distance of 60% of the effective length of the runway, even for operations where the
preflight planning (factored) dry runway landing distances are based on landing within a distance
other than 60% of the effective length of the runway (e.g., certain operations under part 135 and
subpart K of par t91). [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.(table did not paste correctly)

Upon Arrival use AFM numbers X 1.15 if contaminated (under Part 135, the FAA does not differentiate between contaminants, nice!, however in the 8900 they mention if contaminated data exists (even non-approved) you "should" use it. Usually the contaminated data in AFM'S is every thing other than WET, ie. compacted snow, wet snow, standing water. So if it is only wet use the AFM landing distance X 1.15. This is certainly not a black and white subject. There is a lot of information out there, ie 8900, SAFO's, REGS. I always use the most conservative number. So if ever in a court of law, I can fully explain my decision to land on a particular runway. Good luck out there guy's!!!

 

[GREAT LAKES]

135 Landing Distances

Here is my 02 cents:

Pre-takeoff planning:
AFM numbers X1.67 (per SAFO below)
If contaminated then multiply by 1.15
If runway data is not available use the following factors:




Runway Condition Reported Braking
Action
Factor to apply to
(factored) dry runway
landing distance*
Wet Runway, Dry Snow Good 0.9
Packed or Compacted Snow Fair/Medium 1.2
Wet snow, slush, standing water, ice Poor 1.6
Wet ice Nil Landing is prohibited
Table 2. Multiplication factors to apply to the factored dry runway landing distances when
the data for the specified runway condition are unavailable.
* The factored dry runway landing distances for use with Table 2 must be based on landing
within a distance of 60% of the effective length of the runway, even for operations where the
preflight planning (factored) dry runway landing distances are based on landing within a distance
other than 60% of the effective length of the runway (e.g., certain operations under part 135 and
subpart K of par t91). [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.(table did not paste correctly)

Upon Arrival use AFM numbers X 1.15 if contaminated (under Part 135, the FAA does not differentiate between contaminants, nice!, however in the 8900 they mention if contaminated data exists (even non-approved) you "should" use it. Usually the contaminated data in AFM'S is every thing other than WET, ie. compacted snow, wet snow, standing water. So if it is only wet use the AFM landing distance X 1.15. This is certainly not a black and white subject. There is a lot of information out there, ie 8900, SAFO's, REGS. I always use the most conservative number. So if ever in a court of law, I can fully explain my decision to land on a particular runway. Good luck out there guy's!!!