Flaps 25 or 30 for landing?

[JulietAlphaSierra]

Good day everybody, hope you are all doing well today, just a quick question, what determines the choice of flap setting for landing? 25 or 30? What considerations are there for deciding on an optimum flap setting?
Thanks!

-Jo

(I know this is probably in documentation somewhere but I don't know where to look in the FCOM)

[PSX747atlas]

It's down to various factors, such as Standard Operating Procedures with the airline, Runway Length, Weather conditions, aircraft weight, and any defects.

[Will]

Additionally, flaps 25 means the engines don't work as hard, and there is less of a noise impact on the communities below the final approach course. Flaps 30 gives a slower approach and thus a shorter landing distance. Flaps 30 also means a lower pitch, which could translate to (somewhat) better visibility and more stable transfer of the nose gear to the runway.

At least one published source says this: "For normal landings, use flaps 25 or flaps 30. When conditions permit, use flaps 30 to minimize landing speed and landing distance. Flaps 25 provides better noise abatement and reduced flap wear/loads. Note: Runway length and condition must be taken into account when selecting a landing flap position."

Tip: When extending the flaps from 20 to 30, don't make an intermediate stop at flaps 25. :-)

[macroflight]

At max landing weight in a 744F (302t), your Vref will be 165 kt, so the lowest possible Vapp is 170 kt. That is uncomfortably close to the maximum speed for flaps 30, so you might want to use flaps 25 for those landings, especially with a lot of (or gusty) headwind, which would increase Vapp even more.

Anyone know what typical airline policy is here? Are you allowed to plan for a flaps 30 approach if Vapp is 170? 175? 180? I assume there would have to be some kind of maintenance inspection if you exceed 180 with flaps 30?

[Captain_al]

At Boeing we always used and taught Flap 30 landings unless it was an overweight landing, then Flaps 25 was used, so standard Boeing is Flaps 30. There was in the syllabus a cargo fire after a max weight takeoff, leading to an overweight landing. At Northwest Airlines however, we always considered a standard landing was Flaps 25 and Flaps 30 was only used if you wanted a shorter landing distance.

[Mawea]

This philosophy changed in the last years to be more in favor for the 25 landings. So asking yourself is there anything that would exclude an approach with Flaps 25? Landing distance wise, steep glide slope, tailwind, low visibilty, brake temps etc. reverse wet or contaminated rwy.
In general I agree on all the above adding the Load Relief feature which will retract the Flaps to relief the load and not generate maintance work if the speed would exceed as macroflight assumed would happen in a overweight or heavy landing config with Flaps 30 selected. 178kts iirc they start to retract from 30 to 25 and to Flaps 20 when faster than 203kts . * edit (...) 748 even further to F10 when around 240kts.

For macros question, we should plan on a F25 landing when Vref 30 and wind correction exceeds 167kts.


 

[Hardy Heinlin]

and even further to F10 when around 240kts

Is that a 748 feature or a 744 system update? On the 744 the automatic relief used to stop at flap 20.

[Mawea]

Sorry, no 744 update it's a 748 feature. For 20,25,30 to retract up to Flaps 10

[Jeroen Hoppenbrouwers]

Mel Ott said: "Every landing is a short landing."