Landing performance calculation in flight

[herbuel]

Question still about landing performance calculation.

If I understand correctly, once in flight, we use an actual landing distance calculation. I do it with the Fenix EFB and before the flight also with Simbrief.

1/ SOPs usually say it’s better to do both calculations before the flight (Actual and factored landing distances because in some cases, we can find once in flight an actual landing distance > Factored landing distance. How is it possible?

2/ Airbus suggests to take 1,15 * Actual landing distance in flight to add a security margin (and to get a Factored distance). How do you calculate it in Simbrief?

Thank you! Alain

[SimBrief]

Hi Alain,

Regarding your points 1 and 2:

1/ This probably depends on the airline SOP, but of course, it is never a bad idea to also check the inflight calculation before departing. But you will also still need to do one before descent to ensure it reflects the latest weather conditions.

I am actually not sure in what cases the inflight calculation might be longer than the dispatch calculation, but since they use such different methodologies, I guess it could be possible. Perhaps when the runway is contaminated with ice or snow, or when using low autobrakes for example. SimBrief doesn’t calculate contaminated runways unfortunately, but perhaps the Fenix can.

2/ Just to be sure, I think it’s worth clarifying the different landing distance definitions:

• Actual Landing Distance (ALD): The minimum possible distance from 50 feet above the runway threshold to a complete stop. It is determined by test pilots during certification, and assumes a firm touchdown exactly at the touchdown markers.
• Dispatch/Required Landing Distance (RLD): The distance used during flight planning to ensure an aircraft can land at its destination or alternate. Normally the Actual Landing Distance (ALD) * 1.67 (dry runway) or 1.92 (wet runway).
• Operational Landing Distance (OLD): A more realistically achievable landing distance, normally used for inflight calculations. While the ALD assumes a perfect landing, the OLD allows for imperfections in landing technique, such as a 7 second float during the flare.
• Factored Landing Distance (FLD or FOLD): Is the Operational Landing Distance, with an additional 15% margin (OLD * 1.15).

In SimBrief, you can calculate using either the “Inflight Method” or the “Dispatch Method”. And you always get 2 results, the “Actual Distance” and the “Factored Distance”:

Regardless if you choose the “Dispatch Method” or “Inflight Method”, the Actual Distance value is the ALD (first in the list above; the minimum possible distance, measured by test pilots).

If you choose the Dispatch Method, SimBrief’s “Factored Distance” will be the RLD (second in the list above, equal to the ALD * 1.67 or ALD * 1.92 if wet).

If you choose the Inflight Method, SimBrief calculates the FLD/FOLD (last in the list above, 7 second flare time with a 15% extra factor).

So to answer your second question more clearly, yes, SimBrief already includes the 15% buffer in the Factored Distance when using the Inflight Method.

Hope this helps!

[Rodeo314]

@SimBrief

Regardless if you choose the “Dispatch Method” or “Inflight Method”, the Actual Distance value is the ALD (first in the list above; the minimum possible distance, measured by test pilots).

If you choose the Dispatch Method, SimBrief’s “Factored Distance” will be the RLD (second in the list above, equal to the ALD * 1.67 or ALD * 1.92 if wet).

Actually, when you use the Dispatch Method, and the runway is wet:

• Simbrief’s Factored Distance matches Simbrief’s Actual Distance x 1.67
• so it seems Simbrief’s “Dispatch Method” Actual Distance is ALD x 1.15
  when the runway is Wet

For example:

SimBrief - Dispatch

Regards,

Tim

[SimBrief]

Sorry yes, that was already mentioned in the previous thread. Which I probably should have merged this post into in hindsight.

@SimBrief

The “Actual Distance” that appears in the wet calculation, is basically the dry distance x 1.15. Which is how the regulations arrived at the 1.92 factor in the first place (1.92 = 1.67 x 1.15, or in other words, the factored distance on wet runways should equal the factored dry distance with an additional 15% increase).

The Required Landing Distance (Factored Distance when using the Dispatch Method) for wet runways, is actually still calculated using the Dry Actual Distance, but with a higher factor of 1.92. But it didn’t seem right to show the Dry Actual Distance when calculating wet runways on SimBrief, so we simply increased it by 1.15 when displaying it.

Best regards,

[herbuel]

Thank you for all these interesting and precise information!

Just to play with data, I calculated the distance flying during these 7 sec at VAP. Then added a 15% margin to the ALD. I’m then pretty closed to your FOLD!

Once again, many thanks. Alain

[herbuel]

Thank you. How do you display a “formatted” version of the landing calculation? I saw that on different videos, but never find ho to. I just have the text one…

Thank you. Alain