Finals and the gear's down but are the flaps?

[Magic90]

Hello one and all - This is my first blog but perhaps not my last as i progress through my licenses in the months sorry years ahead. You will gather from my query that I am not of the Flight Deck persuasion or civilian crew, but ex-military with my last flying tour of some 3000hrs on type. I felt I should mention this, because at least I have sat on the flight deck for more ccts than I can remember watching student and staff pilots bring it all together for the final 20 seconds…which is where my question lies. Very recently I was returning from a delightful 10 days in the West Indies on a 777.:cool: Slightly ahead of schedule were ushered directly into Gatwick; I wasn’t paying too much attention but as we descended through the cloud base we had a quite a bumpy introduction to the UK weather, it’s always difficult to judge height when not directly next to a window but I believe we were on long finals. The flaps were stepped down and the gear extended and whilst occasionally watching the aircraft telemetry, I followed us down until I could see the perimeter fence pass beneath, at this point I noticed that the flaps appeared not to be fully extended (i was sitting adjacent to the trailing edge), however, as the tarmac appeared the flaps moved to their final position. I clocked the speed at 156mph c.132 kts and then 5-8 secs later we hit the tarmac, port u/c first with lots of screeching - then the stbds hit flowed by, I can only assume, much tramping of the rudder bar to keep us on the dotted line. It was, quite a lively landing, and one I would not want to repeat in a hurry - i done landings with 33 kts across and not been as concerned. So my questions are: 1. At what point should the 777 be in its final landing configuration? 2. Was the landing speed good (it felt a little hot)? Although flap 30 (?) was eventually set what affect to the aircraft does this late setting have to its handling? This is purely for my own edification, but it may also remind others that FRCs are there for a reason…Wg Cdr Spry would have loved this one! Thanks for reading.

[wiggy]

Well FWIW ....

as the tarmac appeared the flaps moved to their final position.

Many companies specify the aircraft should be fully configured by 1000' agl, below about 800' agl the crew would get multiple GPWS "nags" about configuration as in: "too low, flaps", or similar. Given that it's difficult to explain what you saw.

I clocked the speed at 156mph c.132 kts and then 5-8 secs later we hit the tarmac.......Was the landing speed good (it felt a little hot)?

I just happen to have a 777 FCOM in front of me ;) It says at 180 tonnes ( a fairly typical landing weight) Flap 25 Vref is 134 knots, Flap 30 Vref is 128. Given that you fly VRef +5 on final I'd say 132 knots sounds like a fairly normal final speed to me, it's certainly not "hot".

we hit the tarmac, port u/c first with lots of screeching - then the stbds hit flowed by,

Well you mentioned it was bumpy, so perhaps it was windy and there was a crosswind. From the Boeing 777 FCOM's section on crosswind landings: " If using a sideslip technique .....the sideslip should be stabilised before the flare".. In other words it is perfectly permissible to land the 777 wing down. It feels very (very) alien if you've spent a lot of time hours on something where the crosswind landing method is pushing the drift off and keeping the wings level. The sideslip/ wing down technique works really well on the 777, right up to the limiting crosswind of 40 knots.

[NSEU]

however, as the tarmac appeared the flaps moved to their final position. I clocked the speed at 156mph c.132 kts

Since you were not in the cockpit, I would imagine that you were looking at the inflight entertainment screens with the flight data displayed on them. The entertainment systems I'm familiar with use groundspeed, rather than airspeed. Therefore, the approach airspeed may have been higher than 132kts.

[H Peacock]

Nothing wrong in taking the last bit of flap right at the bottom. I believe the B777 can land with Flap 25 or Flap 30 anyway, so it won't get any sort of config warning on the way down like other ac will. I guess Flap 30 just makes it easier to stop at the bottom, ie for shorter runways.

I don't think the in-flight data is a very accurate way to extract actual landing speeds etc.

[Type1106]

In my experience it was perfectly normal to use a reduced flap landing in gusty/crosswind conditions - as you clearly were in the situation you describe. A small addition to Vref can added. In the old VC10 it was 5kts if you chose not to use the last stage of flap and 10 kts for one stage above that.

Looks like the modern jets use the same technique.

[763 jock]

Anything like the third landing? (http://www.youtube.com/watch?v=HK6jDsact3c):D

[Magic90]

Wiggy - many thanks for your speedy and comprehensive response, and to all of you who have humoured my inquisitiveness by posting replies.

I have to conclude that, the aircraft was well within the limits set by Mr Boeing and my clear lack of experience in the use of the sideslip technique coupled with the old saying, "a little knowledge is dangerous" has some part to play with my over excitement.

Although I still think it somewhat alien to be still configuring the aircraft over the threshold but, at the end of the day it would appear to have played little part in the whole scheme of things – and, of course, we all walked away…bonza! :ok:

[wiggy]

I believe the B777 can land with Flap 25 or Flap 30 anyway, so it won't get any sort of config warning on the way down like other ac will. I guess Flap 30 just makes it easier to stop at the bottom, ie for shorter runways

It can but the normal setting for a manual landing is F25. You'd opt/be required to use for F30 for a variety of reasons one of which is indeed shorter runways, but Gatwick's main runway is not that short, even with the displaced thresholds (and for interests sake in some circumstances you can land the 777 using F20).

Nothing wrong in taking the last bit of flap right at the bottom.

That would very much depend on who you fly for and what you mean by "right at the bottom" - taking final flap below 1000' would certainly be against some airlines stabilised approach policy and could well earn you a phone call. Taking final flap over the concrete, as the OP claims he saw happen, would probably qualify for an interview at some airlines....without the tea and biscuits.

edited to add: Magic90 - you're very welcome, good luck with the licences:ok:

[Magic90]

763 Jock - Excellent footage of boeings flying sideways. Fortunately, our landing was no where near the limits these guys were on but yes, no. 3 does look similar to the effects I believe i experienced.

Do i assume correctly that by using the sideslip technique the max crosswind limit for the airframe is increased? Or does the rudder still give enough authority for a wings level landing under the same max crosswind conditions? (hope that makes sense).

[wiggy]

It's a 40 knot limit irrespective of the technique.....FWIW the 777 will even Autoland with 40 knots across :eek: though you have to have CAT 1 RVRs....

[Magic90]

Wiggy - Bless you again for the gen and I promise I will leave you alone but, what's the benefit of a sideslip over wings level landing? Or am I not thinking out of the box enough?

[wiggy]

This is probably something a trainer would be better at answering, but I'll give it a go ...with the kick off/wings level technique if you get the flare wrong and you float you can start being blown downwind, towards the runway edge. On the other hand with sideslip/wing low technique you can get the fuselage and gear aligned with the runway well before the threshold, so as long as you hold the sideslip during the flare you shouldn't start drifting sideways.

Personally having gone to the 777 having spent a long time on the jumbo, where you got a wing low at your peril (risk of outboard pod strike), I'm more comfortable with the old kick off technique but then transition to a bit of a sideslip in the flare.........it's a bit hybrid but I've noticed a lot of guys do similar.

[Magic90]

Yes I understood it completely and although I shall never reach the commercial world of aviation I will remember your explanation – thank you.

[cosmo kramer]

I fly 737. Normal landing flap settings are 30 and 40 deg. Depending on airline policy normally flaps 30 is used due to lower drag (hence fuel consumption and noise). Besides the obvious uses of flaps 40, e.g. short runways etc, Boeing recommends to use flaps 40 for tailwind landings.

It's not uncommon that you plan a flaps 30 landing only to realize there is tailwind during the approach. In such case I normally opt to call for flaps 40. Of course the decision has to be made somewhat before the flare, say above 200 feet.

I am not that familiar with Gatwick, but Wiggy mentioned above that the main runway has a displaced threshold. Hence, when you saw the perimeter fence the height could may well still have been a couple of 100 feet = not too late to make the calling for the next flap setting.

This does not go against the "stabilized approach concept" since it says the aircraft has to be in "landing configuration" - both flaps 30 and 40 are landing configurations, so in my opinion I am allowed to switch to flaps 40 if I desire. At least, I did so more times than I can count and no one ever complained.

I could imagine the same principles would apply for the 777 as well.

[wiggy]

This does not go against the "stabilized approach concept" since it says the aircraft has to be in "landing configuration"


Perhaps this varies from airline to airline - I can only quote from our stabilised approach criteria which are quite specific across all fleets: you are meant to be "in the planned landing configuration by 1000' ", my emphasis on planned. I know a plan can change ;) but switching from one permissable landing flap setting to another at a couple of hundred feet, would certainly "ring bells", so to speak...but other operators obviously use a different intrepretation - each to their own I guess.

[Avenger]

Hmmm?? Boeing say the normal flap is 25 or 30 for landing and the aircraft should be stabilised by 1000 AGL. IMC and 500 AGL VMC. The 777 FCTM Chapter 5 sets out the requirements for a " stabilised approach", one of which is the correct landing flap, Selecting flap 30 from 25 or visa versa is not a good idea. Also, the sideslip technique is to be removed form the FCTM and QRH limitations as Boeing now state " Crab" is the safer method and as it affords a greater XWC, on all boeings, this is to become the normal method in training.
Ex: 777 XWC limit DRY RW Crab 45 KTS, Sideslip 31 kts (772), 35KTS (773) ,

Landing distance and Vref also vary with flap, Vref by about 8 kts, so if you alnd F30 with F25 Verf inc the A/T addition, you are 13 kts into the max 20 Kts allowed on Vref.. Easier to fly it as Mr Boeing wants, saves Tea and No biscuits with the Boss

[BOAC]

At least, I did so more times than I can count and no one ever complained. - we must assume then that your airline has no safety monitoring system!

[wiggy]

Avenger

the sideslip technique is to be removed form the FCTM and QRH limitations as Boeing now state " Crab" is the safer method and as it affords a greater XWC, on all boeings, this is to become the normal method in training.
Ex: 777 XWC limit DRY RW Crab 45 KTS, Sideslip 31 kts (772), 35KTS (773) ,



Thanks for the heads up, I'm now really looking forward to having a go at 45 across...:eek: :\

[cosmo kramer]

BOAC:
- we must assume then that your airline has no safety monitoring system!
Of course. FOQA is a requirement in all EU ops companies today, is it not?
We are required to be stabilized by 1000 feet like almost everyone else in "landing configuration".

The stabilized approach criteria was invented to prevent pilots to attempt landing from rushed or messed up approaches.

Lets say I have a perfectly stabile approach at 1500 with a reported 10 knots crosswind. Passing 500 feet the controller give the landing clearance along with the information that the wind has shifted to 10 knots tailwind. Which option would you prefer?

1) Go around (due to not being at the Boeing recommended flap setting for tailwind landings)?
2) Land with a flap setting that is not recommended for tailwind?
3) Select flaps 40, push the nose a bit along with a little thrust increase - and land? :ok:

In my opinion this goes under the common sense category of flying the aircraft. Apparently I am more fortunate that you were, that my company recognize that.

[BOAC]

At least, I did so more times than I can count and no one ever complained. - I feel sorry for you - you have obviously been dealt a really rough lot of landing weathers.1) Go around (due to not being at the Boeing recommended flap setting for tailwind landings)?
2) Land with a flap setting that is not recommended for tailwind? - i have never been fortunate enough to have this recommendation in any of my manuals. Can you tell me where you have it? FCTM?OPS manual? You would need to beware the 'Texas Tailwind', though.................

I am also impressed with your ability to check the LDR with a 10kt tailwind from just 500'. Terrific!

[Avenger]

The landing distance difference between Flap 25 and Flap 30 at 180T braking action good is 55' the tailwind adjustment Flap 25 is 225' and Flap 30 220, there is a net difference of 60' and the Vref flap 25 is plus 6kts.
The time it takes to run to flap 30 and adjust the Vref, is it worth it? most people float for more than 60' Lastly, I don't think you will ever find Boeing recommending a flap setting for tailwinds..

[Lord Spandex Masher]

The stabilized approach criteria was invented to prevent pilots to attempt landing from rushed or messed up approaches.

Edzackery! Yet you are happy to be reconfiguring below 500'.

That seems like a rushed and/or messed up approach to me.

My preference would be to go around, plan for a tailwind or the other end.

[Avenger]

My choice would be to land with a 10kt tail wind, the 777 is approved for this. But, for those interested, some food for thought:http://www.skybrary.aero/bookshelf/books/1148.pdf