Landing flap; use of A/T

[alf5071h]

Researching landing overrun accidents:-
Where there is a choice, what proportion of operators use less than full flap for landing ?
What are the factors in the choice, operational, economic, ….
Are these reviewed according to runway condition reports.

What proportion of operators use auto thrust in manual flight, and fly the approach and landing with A/T for speed control ?
Again, what factors would be considered, operational, workload, safety, …
Does use of A/T detract from speed awareness.

[flyfan]

Regarding your question for the landing flap: I'd say 90% of the time I use F30, instead of F40, on the 737...F40 gives you a little lower Vref, but a lot less margin to run into the flap overspeed (175kn vs 162kn; GUSTS!). Additionally the airplane is, in my opinion, nicer to fly with F30. Nonetheless, if operationally required d/t landing distance, steep approach, contaminated runway etc F40 is used. I don't think there's a huge economic impact on using F40 instead of F30: Flaps come out very late so fuel burn isn't really an issue, maybe less wear on the brakes...

For the A/T: I guess it really depends on the type of the airplane - Airbus logic in general is to leave A/T in till 20(?) ft, when the ship tells you to retard (SOPs can be different though, AFAIK LH group does it differently). Boeing's logic is different and all over the place. for example the T7 cancels A/T only when selecting reversers, while the 737's A/T system works acc FCTM in a way of AP off = A/T off (Even though you could leave either engaged, with the other off). Yet I know of a few guys keeping it armed on approach (not engaged, just armed) for low speed protection. Personal preference and/or SOPs I guess.

[vilas]

Despite the fact that only 112 B737 800 operate In India as against 411 A319/320/321 B737 is involved in most overruns. Two airlines operate 737. In 2019 monsoon there were 5 over runs in 72 hrs four of them were B737 three from one of them and one from the other. The other had a fatal overrun in 2020. The reason generally is high threshold speed, crossing threshold above 100ft+, incorrect flare and long float and touching down between 1000 to 1600mtrs. It appears that training and checking standards, operating culture is at fault. As far as AP/ATHR procedure is concerned 737 is both on or both off, Airbus recommends to keep ATHR even without the AP but no embargo on manual thrust. And only in auto landing retard call is signal to retard thrust, in manual it's pilots call.

[alf5071h]

Thanks for the inputs;

Re 737 overrun statistics, this has been noted in this forum. A cursory review of overall accident records also suggests a pattern; however without further study this is only an association. *

The margin from flap limit speeds is interesting; this suggests that the lesser flap (by choice) allows a greater speed deviation in an un-noticed unstable approach.

Similarly the use of auto thrust with low speed protection, which could relieve crews of the burden of speed monitoring (reduced IAS scan), focussing more on the flight path. Thus an acceptable path might be achieved at the expense of a high speed, flare - float - long touchdown.

Further questions on landing performance;

Which aircraft / operators now use operational landing distance opposed to un-factored / factored certification data ?

If the performance is tabulated against aircraft mass, is this used as a simple ‘below the weight required for the runway’, or can the margin between the limiting and landing mass be translated to additional distance margin - for choice of braking level, inaccurate reported braking action ?

* 737 Accident News (http://www.b737.org.uk/accident_news.htm)

[FLX/MCT]

Speaking for the A220:

My outfit uses per default a reduced landing flap setting.
Full flap is recommended for contaminated and short fields (short field is not defined through policy and decision is up to the crew). Full flap is mandatory per manufacturer for approaches steeper than 3.5° angle.

A/T use is generally recommended but prohibited for steep approach. 5 kt speed increment are required by manufacturer if the A/T is used for landing. As this has quite an impact when operating on short runways, you might end up flying man thrust with Vref in limiting conditions.
We apply "operational landing distance" for in-flight calculations.

[FullWings]

777-200/300 operator here. We have a choice of F25 or F30, and with adequate margin I have no problem using the lower setting as it only adds 6-7kts to Vref. There is a technical fuel saving for the last 5nm of the approach, but if it’s going to mean missing an exit and increasing the taxi distance there’s not much point. We’ve done quite a few modules in the sim on overrun prevention and I feel my Company would rather I used all the flap on some of our more limiting runways, even if the figures didn’t look too bad. Condition reports, wind components, etc. all used in the decision.

Manual thrust not allowed, unless dispatched with no A/T. Many of us would think twice about accepting this defect for an ULH flight...