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Old 20th May 2007, 09:50   #1 (permalink)
 
Join Date: Apr 2005
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B737-800 Flap speeds

Our FCOM contains a phrase: Select Flaps passing through the minimum flap speed on the speed tape. This reduces wear on the flap tracks. Using Flaps as speedbrakes is not recommended"

We operate into an first world airport with third world ATC somewhere in the south of Europe where a visual approach is offered when some 7-8000 above profile. Now we are big boys and have no problem asking or demanding more track miles if needed, that is not the question. The technique I have seen is: LVL CHG, Speedbrake out, speed 230 Kts, Gear down at 260Kts (Max Speed -270kts), Flaps 1 and 5 at 245Kts (Max speed 250Kts). This produces a very steep descent rate and we can regain the profile before 10 miles final.

The max flap speed is 250Kts for 1 and 5 and the minimum clean is 210 kts. We did not breach any aircraft limitations. But is it good practice to operate the aircraft just inside the flap and gear limitations like that?

Last edited by Telstar; 20th May 2007 at 10:06.
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Old 20th May 2007, 10:18   #2 (permalink)
 
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The answer to you question is NO it is not. Respect limits and be kind to aircraft. In the same way that G-limits on landing is 2G.....we don't routinely aim to land just shy of this....or do we!?
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Old 20th May 2007, 10:30   #3 (permalink)
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Whilst flap assemblies ARE 'stressed' for the max speeds, the fatigue life assumes they are used more often at 'normal' speeds, hence you do them no favours.

Why not 'plan ahead' and get the profile sorted out for that (expected) visual? Most operators also discourage excessive rates of descent near to MSA which is worth bearing in mind as you drop like a brick. Often the best way is min clean, gear/flap to approach flap when cleared for the visual (with appropriate flap manoeuvre speeds) and set your company 'limit' on R of D in V/s. The reduced ground speed will help lose the height in the least track miles.
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Old 20th May 2007, 10:39   #4 (permalink)
 
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Why accept the visual approach? Why don't ask for a 360 to loose hight? Do you have an ideea about the noise landing gear makes inside the plane when extended at high speed? Do you tell the pax you'll extend the gear,so they should expect very high noise and maybe vibration? I bet not....
So ,again ,why should one accept and perform such a manouvre? We have a strict data monitoring program ,and I suppose after few of these approaches , a talk will take place between the company CIFS and that particular airport officials.
I know that some controllers, and unfortunatelly pilots also , think that we are flying fighters.We are not.
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Old 20th May 2007, 10:59   #5 (permalink)
 
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Not really...

Telstar,

Next couple of times this happens to you, try to experiement. I think you'll find that the first few increments of flaps/slats add very little drag, and the only thing you're accomplishing is beating up the flaps/slats and the passengers.

This is mainly why Boeing states this is not recommended. You're not really helping yourself. (What you want and need is drag...and you're not getting it with low flap settings.) Boeing has a publication somewhere (I remember reading it years ago.) about energy management in descents. If you can get your hands on this, it'll explain a lot.

The best way to 'slam-dunk' is with gear and speedbrake....keep your speed up a bit. It'll drop like a rock. The other alternative is to grit your teeth, slow up and work out your flaps, then gear, then more flaps (extend flaps on the normal schedule), until you get to approach speed plus a bit. Once you have full flaps, gear, idle thrust, you'll find the thing will come down nicely. (The trick is to be patient while you get to this configuration.) Of course, you must be careful to arrest the sink rate and be spooled at the proper time.

The idea of not using flaps/slats as a speedbrake applies to most airplanes. Again, it's drag you want and need, but flaps/slats don't give you what you need...unless you have everything hanging out.


Fly safe...


PantLoad
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Old 20th May 2007, 17:25   #6 (permalink)
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Hello first of all, I'm new to the forums first post. I've pondered the rapid altitude loss configurations also, here is the note in the FCTM that says "the use of speedbrakes with flaps extended should be avoided, if possible." "The flaps are normally not used for increasing descent rate."
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Old 21st May 2007, 09:32   #7 (permalink)
 
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Thanks for the replies. All Gates and Limits were respected, and no aircraft limitations were busted, and I take on board what you are syaing about fatigue life BOAC.

Orbits on final are a very hot issue at the company who I work for after a few very spectacular cock ups. There are restrictions on doing orbits with the gear down and inside ten miles. I think from now on its more track miles for me. I know the aircraft can make it with less track miles, but it doesn't mean I have to!
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Old 21st May 2007, 10:16   #8 (permalink)
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Quote:
Orbits on final are a very hot issue at the company who I work for after a few very spectacular cock ups.
- hmm! Your company is not alone.

I would recommend a 'go' at para 2 of post #3 next time. Folk are SO reluctant to get energy DOWN for the 'expected' visual, and it really does not use much extra fuel/time if for any reason you then decide to take radar vectors etc. The slow speed/gear/approach flap will also save time in the long run if you are 'high' as you will use so many track miles and although it seems to take an age, as PantLoad says, it does not, in fact.

Like PL I caution against gear at high speed for the same reasons - plus the same fatigue issue, and I have a personal 'limit' of 230kts (737) for 'planned' gear extension - and try to make a quick PA beforehand if the situation permits, as it is so noisy and 'unexpected' for the pax (and crew)
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Old 21st May 2007, 10:51   #9 (permalink)
 
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I have been put off orbits a little after our incidents to be honest BOAC, and I certainly wouldn't want to be the guy who ends up in front of the CP for a "No tea, no biscuits, your hat my office, axminster shuffle type interview" after these new restrictions have been published!

Correcting Flight from above the Descent/Approach profile

The only lateral manoeuvring that is acceptable to regain the vertical approach profile is as follows:

• Request entry to a published intermediate holding fix in order to lose altitude
in a clearly defined and controlled manner to achieve the platform or step
altitude at the correct speed and aircraft configuration

• Request an "orbit" that should be executed as a racetrack pattern for stability which is subject to the following:

(1). Not less than 10nms remaining to touchdown
(2). Descent to not below the MSA or 3,000 ft whichever is higher
(3). Max Flap 10, with speedbrake if operationally necessary
(4). Met conditions VMC

• If a visual approach has been requested and approved by ATC that is not
straight in then consider extending the downwind or widening the base leg,
subject to other traffic

• If required conduct a full published Go Around to another approach

• It is not acceptable to join a visual circuit from an incomplete Go Around

If there is any doubt about the successful outcome of the approach a Go Around must be the prime consideration and is preferred over any other method.

This airline does not permit orbiting manoeuvres inside 10nms from touchdown or with landing Gear extended.
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Old 21st May 2007, 11:20   #10 (permalink)
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Well - that nails your options somewhat. Just to be clear - I am NOT advocating any 'orbits', gear up or down. Just forward planning and use of low forward speeds to help you lose the height if you need. That was the only way I could fly the VOR approach onto R35 in Pristina with a high sector MSA. Nothing else allowed me to achieve the profile and worked out to be the most efficient too.

The technique is really applicable to your 'bullet point' #3 and avoids excessive extension.
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Old 21st May 2007, 17:12   #11 (permalink)
 
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If the met for your destination and your knowledge tells you that a visual might be expected, plan your decent for the visual! Is that too simple?
If you really need to get down then you can use the very simple formula of 1000feet/nm. plus two miles to spool up/stabilise at 500agl.
This ROD is achieved once the aircraft is fully configured at 40 Flaps and with the speed stabilised at Vref plus 5 but not more than 140kts. This figure is good for all B737s in still air. The trick is to act against your instincts and pull the nose to above the horizon, stop the decent and configure on the speed schedule, reduce to 140kts. and then, and only then, lower the nose and watch the result!
I have seen it done quite safely from 7500 with 10.5 track miles to run.
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Old 22nd May 2007, 07:30   #12 (permalink)
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Telstar - there should be enough here to give you some ideas. Posts 3,5,8,10 and 11 all advocate another way/ways to 'approach' the problem. Why not try them? No orbits, no breaking company 'rules' and safe efficient flying Enjoy.
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Old 22nd May 2007, 13:20   #13 (permalink)
 
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If you are VMC, there is little wrong with an "orbit". You have to be situationally aware. My compatriots in Germany regularly extended Flaps to 5 and kept the speed at 240 Kts. This seems like bad airmanship but it works a treat.

The speed brake and gear combo is way less effective on the -800W than say on the -300.

What was the BOAC incident?

Does Flap ware actually occur whislt operating within the Limitations?
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Old 22nd May 2007, 16:02   #14 (permalink)
 
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There are really only two things to say about all of this:
1) The esteemed gentlemen in DUB / EMA who spend a lot of time writing the books, do not spend enough time going to all those lovely north Italian airports: TRN, VBS, TSF, TRS…
2) You could do, what I would obviously never do: fly speed 220, F5, speed brake out, while looking at the box showing you a flight angle of approx 5,6 deg, all this while quietly thinking about the fact that you can the change the 5,6 to close to double digits by lowering the gear... pure karate flying
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Old 22nd May 2007, 17:31   #15 (permalink)
 
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Boeing recommend you don't use flap as an extra speedbrake.

Funnily enough most companies repeat this advice in their ops manuals. This is to prevent damage to the flap tracks and other bits. A flap track failure at worst may prove uncontrollable.

So do you follow the advice of the manufacturer or your mate on the flight deck ? Seems like a no brainer to me. Use the flap as the manufacturer and your company recommend. To do otherwise is poor airmanship.

Exceptions would be situations requiring you to get on the ground asap. You then can use the full limits knowing that nothing will fall off.

As pilots we often complain when the company rosters us to the edge of legal limits. We observe that while it may be legal it is most certainly not wise over a protracted period as sooner or later there will be an unpleasant consequence. Why is the aircraft any different especially as when we make the rostering complaint we ofton observe that if we treated the aircraft the way the company treats us they would break.

I do work for a large loco in Europe so do know what the pressures are.
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Old 23rd May 2007, 04:55   #16 (permalink)
 
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I have flown in Europe a few years ago but not sure where you are referring to. Northern Italy descending over the Alps?

Why not bring the speed back to min clean while you are being kept up then dump gear/use speed brake and accelerate back to 250kts when cleared to descend.

The flap 40 trick works well but I only use this closer in as it stuffs up traffic flow! I need speed about 155kts with flap 40 at higher weights on the 800W to achieve 1000'/nm.
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Old 23rd May 2007, 09:36   #17 (permalink)
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Interesting thread so far .. two comments I would echo ..

(a) ... If you really need to get down then you can use the very simple formula of 1000feet/nm. plus two miles to spool up/stabilise at 500agl. .... I have seen it done quite safely from 7500 with 10.5 track miles to run.

Personally don't like full flap but approach flap with a bit of speed on works to give around 1/1. I routinely used this to effect DRW-CNS in westerlies .. approaching overhead the upwind end at around 10000 and then a dirty idle descent down to end downwind .. spin up ... landing flap and a normal base and final. Worked a treat and the pax didn't have their teeth rattled out of their heads with turbulence generated gyrations ..

(b) the limitations address the basic structural requirements and a presumed operational scenario for fatigue calculations. He who routinely pushes the gear and flap limit speeds goes outside the normal sort of fatigue presumptions and will experience a significant increase in routine maintenance costs for gear doors etc., and flap hardware. Probably not an accident concern if the routine maintenance is kept up to the mark as the hangar boys (most likely) will find the usual cracking long before things depart from the base structure. But it's a very silly operational and commercial practice. In the occasional emergency situation where you MUST get down .. the considerations are quite different. However, for routine operational use, the sums just don't add up.
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Old 23rd May 2007, 11:13   #18 (permalink)
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Quote:
but approach flap with a bit of speed on
- hence the reason for full flap, JT, to AVOID the "bit of speed on" for those very reasons.
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Old 24th May 2007, 02:54   #19 (permalink)
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Acknowledged but the operator had an SOP along the lines of full flap requiring to be spun up regardless of height so the approach flap was necessary to comply. Only looking at a modest speed delta .. not anywhere near limit speed for the setting.

In any case, provided that one monitored profile progress critically (and we were real good at doing mental arithmetic) there was never a problem with the final transition to landing configuration.
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Old 29th May 2007, 11:07   #20 (permalink)
 
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The way I see it as long as you stay under the limitations you are doing just fine. If they wanted you to fly slower with the flaps and gear out they would put it in your manual(s).

We are paid to fly airplanes not "play" structural engineer and guess/assume that we should operate below the limits. There is no reason to do a 360, especially when you need to get to the hotel bar for drinks.

The limitations are for normal operations, not emergency circumstances... If do don't agree show me where in your books it lists "Prefered Limitations, or Limitations for Normal Use." Untill a my company publishes "Recomended Speeds" that are lower than the current limitations I will use the limitations as my guide.

In an real emergency if I'm 20 knots fast and I want the gear down it's comming down 20 knots fast, same thing with the flaps.
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