777-200 flare

[pax2908]

Hello,

I think I have noticed that sometimes flaps are retracted on 777-200 during the flare, before the wheels actually touch the runway. I have not seen this on other types (however I most often happen to be on 777). Is it just an impression? If it is indeed true, why is this done?

Many thanks !

[BAe 146-100]

Hi,

It may just be a optical illusion.

http://www.airliners.net/photos/small/5/0/5/291505.jpg

BAe 146-100

[mutt]

The flaps retract on the B777 during the flare........ are you sure????? what happens if the crew have flared too high??????



Mutt.

[NigelOnDraft]

I don't know the exact details, bit the 777 has some whacky "variable drag" "constant thrust" feature, which involves the flaps moving to maintain speed. Suspect this and what you have seen are related...

NoD

[woodpecker]

Flew it for abour five years and there was certainly no flap retraction in the flare!

[slingsby]

visual perspective to a fast moving object changes with aspect/ratio, ie it will look different as the aircraft passes you or changes attitude in the flare.

[ETOPS]

Just to nail this firmly on the head - The Boeing 777 does not alter it's flap setting in the flare! Land flap is set to F30 and speed reduced to vref +5 no later than 1000' AAL and the approach is continued in an entirely standard format from there. This is almost identical to the B737,757 and 767 all of which I have operated .

Nigel on Draft

I think you might have dreamt this Constant thrust business as there is no such thing on BA 777s. You might be confusing our SOP to leave autothrottle engaged all the time (even when hand flying) and the automatic flap load relief which is operated by exceeding flap limit speed......

[Thomas_Cook_757-300]

Hi,
Do you think this may be a mix up with the Slats being retracted on 747s when Reverse Thrust is applied?

Thanks

Thomas_Cook_757-300

[ratarsedagain]

ETOPS,
Actually, NoD is on the right line. The 777 does have the ability to move the flaps to maintain speed on final approach, but it is neither mentioned on the technical course, or in the Technical Manual.
With F30 set for landing, if the speed starts to reduce significantly below the bugged speed, then the TE flaps do infact retract slightly to reduce the drag, and hence recover the lost speed, without excessive (if any) thrust lever movement. Conversely, if the speed gets too high, then the TE flaps will extend slightly from the nominal F30 position to increase the drag and bring the speed back again.
The whole idea being to maintain a (relatively) constant thrust setting on final approach.
However, I doubt either would be of sufficient magnitude as to be seen by someone watching the aircraft landing.

Hope this helps.

[pax2908]

Thank you for the replies. I should have said, more precisely, that I thought I hear the noise of flaps moving, just prior to feeling the touchdown (1-2 seconds before). This happened on more than one occasion, and each time was a normal, "firm", touchdown. But it is now clear, from your replies, that there is no deliberate action to start retracting flaps at that stage.

[ETOPS]

ratarsedagain

I know this is nit picking, but if it's not in the tech manual or mentioned on the course how do you know?

I will ask our backroom guys when I get back from Brazil....

[ratarsedagain]

ETOPS,
Fair question!
One of our Trg Capts who did the the course with Boeing enlightened me. Came up during a discussion as to why some excessive speed excursions occur on finals.
Get a bit slow, put a bit of pwr on, flaps retract a bit at same time(unbeknown to you)-speed shoots up. Conversely, get a bit fast, pull a bit of pwr off, flaps go out a bit at same time, speed drops below Vref.
Be nice if they told us this stuff!

Enjoy the K. C. in Brazil ;)

[NigelOnDraft]

ratarsedagain

Thanks for the backup... I'll see whether ETOPS withdraws hid comment to me (not that is it that harsh....!)

I don't even drive the thing (unlike possibly ETOPS if he's in Brazil!), but was sure someone mentioned it to me as the basis for the reason for why the Nigel 777 guys are not encouraged to disconnect the ATHR.. you get into a sort of PIO (so above...)

NoD

[ETOPS]

Just back from GRU - Flew G-YMMP and took 11 hrs 10mins so off to bed real soon.

No I'm still not convinced about unheard of flap modulation during the approach and will give MP a ring tomorrow. As he is BA's 777 Tech manager I will abide by his answer.

It's a BA SOP to fly with autothrottle engaged at all times. It is actually easier to hand fly with it disengaged - like most Boeings, but the Fly by Wire system takes any power induced trim changes out of the elevator feel. When you set a pitch attitude (either manually or thru' the autopilot) the elevator system treats that as a flight vector and actual elevator movement bears no relation to stick position if power is altered at the same time. Thus you have to work very hard and make coarse control inputs to induce PIO at any stage. Simply put - she goes where you point her and a single blip of trim syncronises speed and feel. PFM........

[ETOPS]

Just had a word with the BA 777 fleet tech manager (Core) ((whatever that means!!) who agrees with me that there is no flap movement on approach with land flap set - even if speed is low. He points out that there is a autoslat feature that will deploy the leading edge slats from "sealed" to "gapped" if low speed protection is triggered (alpha floor in airbus speak) but as the slats are fully deployed at flap settings beyond F20 this is not what is being discussed here. Similarly the flap load relief operates at a high speed and would be very exciting during final approach where speed should be stable by 500' AAL.

Hope this is the definitive answer we need.........

[NigelOnDraft]

ETOPS...

I have just spoken to my source, and without prompting, reiterated what I said above... As also indicated above, my source's source* got it from Boeing, and its not in the Tech Manual etc.!

As I said, not my plane guv, but will be interested to see if it's true, and significant enough to be seen as a "Flap Retract" during the flare from the cabin...

ATB
NoD

* A previous 777 Tech Mgr, and they're flying together soon, so he'll try to get some more info...

[aviate1138]

Hope this is the definitive answer we need.........

The trouble is we have such complex aircraft now, that the question provokes wild theories from people who also believe in UFO's, Aliens, and religion. It is in the human psyche to always fill an unknown quotient with an answer - right or wrong - hence Jesus and Allah and the X-files, Conspiracy Theory and the Bermuda Triangle! The question about the possible movement of flap prior to touchdown on a 777 is sure to be answered eventually but with any aircraft being controlled more by computer than human the Engineers will have the answer, more likely than the pilot! Anything designed by many will have many problems. ETOPS has provided the answer I am sure, via the Tech Manager.

BJ

" I spend my money on light aircraft, women and booze, the rest I just waste."

[ratarsedagain]

ETOPS,

Call me cynical, but when do we ever get a definitive answer from the fleet management!;)

As with Nod's source, the info came (via A Senior Trg Capt in my case), from Boeing. The info was given to him by one of the Boeing test pilots they got to know whilst doing the course in SEA.

It's obvious you doubt the credibility of the information, that's your prerogative, however, I've no reason to dispute it. After all, i'm sure there's a huge amount of other stuff goes on 'behind the scenes' on the 777 (and probably the Airbus too) that isn't in the Tech Manual or Tech course.................

Cheers for now:D