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-   -   Deploying flaps - when? (https://www.pprune.org/passengers-slf-self-loading-freight/576506-deploying-flaps-when.html)

OntimeexceptACARS 22nd Mar 2016 18:36

Deploying flaps - when?
Have always been used to flaps deploying a little (maybe 1 or 5) when above 3000 or 4000 feet, and maybe something like flaps 20 on long finals, then full flaps on short finals or DME 5 (please bear with me, spotter and SLF estimates here). Last week inbound to LHR aboard TK1985, A330-300 the aircraft was full flaps up until levelling out for finals on 09L over White Waltham. Looking at the TV screen in front of me ground (I know not airspeed) had fallen to about 123mph (wasn't calibrated in knots). I know it wasn't a windy day, probably less than 10kt on the ground. FR24 playback shows the aircraft at 145 kts at 700ft, I know that can be unreliable, and falling to about 128 knots by 200ft.

I just felt that the flaps went out far too late, they were fully stowed on the base leg, not even flaps 1. I have a photo of the wing over the Dorney boating facility with flaps just gone out (maybe 5 or 10?). FR24 estimates 1975ft there, at 158kt.

Any thoughts from flight crew more in the know than me? Is the big wing an advantage here? The flight was maybe 80% full.


Hotel Tango 22nd Mar 2016 20:58

Have to say that flaps fully stowed on base is not that unusual in some environments. I've experienced it many times. Early deployment too. It all depends on so many possible scenarios including what ATC wants in terms of speed as they vector the inbounds. Some aircraft, subject to weight, can fly clean at much lower speeds than others etc etc. I fly often on the Canadair CRJ-900 to Birmingham. Initial flap deployment varies all the time.

+TSRA 22nd Mar 2016 22:51

Weather, ATC, weight - it all plays a part. I've been told many times to keep the speed up for as long as possible, especially in the first minutes of rush hour. That means everything goes out a little later than the normal plan, but if the energy is managed properly then it's not an issue when the plane starts getting dirty. Granted, there is a "lower limit" for when you gotta be configured, but that's what managing the plane is all about!

OntimeexceptACARS 23rd Mar 2016 23:17

Thanks for the replies guys, what briefly worried me was a definite surge of power when on base leg - worst thought was the protections on the A330 kicking in, but all SLF conjecture, even after 500 flights and a lifetimes enthusiast experience!

Hotel Tango 23rd Mar 2016 23:27

I can only guess that the "surge" of power was as the aircraft leveled off, especially if still in a clean flap configuration (i.e. the power adjustment would be much more noticeable).

AerocatS2A 24th Mar 2016 00:03

Power surge could also be as the aircraft decelerated to and achieved its selected speed. Power will increase from idle and some auto throttle systems aren't subtle.

PAXboy 24th Mar 2016 08:23

I have noticed that there is no pattern as to when power returns or is reduced. On a short 1 hour sector this morning (E90) it was different again due, probably to the small size. It was all good!

+TSRA 24th Mar 2016 18:51

I can only guess that the "surge" of power was as the aircraft leveled off, especially if still in a clean flap configuration (i.e. the power adjustment would be much more noticeable).
I would add that a descent conducted at idle plus the above quote would make for a very noticeable "surge." If the aircraft was very light too (low passenger numbers, at the end of a flight) that'll play into it compared to the same aircraft but heavier.

fujii 24th Mar 2016 21:24

Final, not "finals." You are only allowed one final per approach.

Piltdown Man 31st Mar 2016 09:52

In general, if you don't need the flaps, you don't use them. I fly an E190 and if I'm given complete control of my flight I'll not start lowering flap until I have about seven miles to run at 2,000'. However, ATC regularly place constraints on speed, level, and descent rate resulting in a requirement for us to lower flaps earlier than we would without the constraints. The speeds at which they are actually deployed vary with weight, icing conditions and the requirement for drag.


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