. For the most part it is good not to use them for passsenger comfort if not really necessary.

 

That's really dependent on a/c type on how much buffet they produce. During the VC10 flight testing they chopped of the corners reducing the buffet to almost nil and yet still retaining maximum braking effect.

I think you're mis-understanding what he mean't, he clearly said "energy management" and didn't say they were dangerous. For the most part it is good not to use them for passsenger comfort if not really necessary. However, they are fitted to the aircraft to be used so if you need a rapid descent they can be used.

 

Exactly. Off course they are not dangerous, they are fitted to be used and can be used. But only when absolutely needed, otherwise you burn more fuel unnecceseraly. There are cases where ATC will require you to descend fast, you have to use speedbrakes to stay on glide path in these cases. And as tf51d said it has to do with company policy and/or pilot preference. Autobrakes while landing is another exaple: some pilots use the minimum autobrakes neccesary to bring the a/c to a halt while trying to minimise brake wear (and cost of maintenance). There are other pilots who brake like there s no tommorow so that they use less runway for safety.

pretty much every flight I have been on spoilers are used, so this idea that spoilers are never to be used in flight is something I have never paid much attention to. Good use of the speedbrake, level change pitch mode, those are the two methods I have used to slow down the NGX.

 

Sometimes things have not went as smoothly as they should. Mainly because I was distracted and wasnt ontop of the speed as much as I should, and I used flaps to slow down, especially the slats/flaps 1. I find if you are ontop of the speed early, you will be fine, but if you let it get out of hand, it is very difficult to get it back under control.

Most of the above answers are about decending out of Cruise from FL3xx. However looking at the OP, he mentions Flap speed targets, which to me means he has APP mode engaged, and is likley on an ILS (or maybe RNAV) approach profile, decending on the 3 degree, and already down around 220kts.

 

Which is the usual or "correct" method of slowing down while descending:

- Slowing down by deploying flaps and letting the aircraft reach the respective speed targets, or

- slowing down by manually reducing the speed through the MCP.

 

This appears to be regarding the speed selection via the MCP speed window in SPD mode, or VNAV (blank MCP speed window) on final approach (ie when slower than 220kts, in Approach mode, and decending on the glidepath).

 

At some point the 737NG will dump the VNAV speed, usually around the 160kts mark, but sometimes earlier depending on various factors such as landing gear selection, flap selection, height etc.

 

If ATC give you a speed restriction, you will need the speed window open straight away, but if ATC requirements are not stringent (might happen if traffic is light etc) then there's no real reason to come out of the VNAV speed (Blank speed window) till you want to reduce speed below the 160kts area.

 

As your speed comes up on the flap mark for next stage (ie where the VNAV speed has set the selected speed bug) then open the next stage of flap if you want to slow down more.

 

I believe it's usually flap 1, then 5, then maybe 10 if you need more drag. You will need to lower the gear before flap 15 or else you get config warning. Flap 25 is a good transition if you are using flap 40, If using flap 30 I usually jump from flap 15.

 

It's good practice not to open the next stage of flap before reaching (ie while travelling faster than) the green flap mark for the flap you have set. Eg; Flap 5 when you are established on the flap 1- marking. Flap 10 (or gear down/flap 15) not before your speed is exactly equal to the flap 5- marking.

 

At some point before you hit flap 30 the VNAV speed will disconnect and the MCP speed window will activate. At this point you will just adjust this as required (to say Vref+5 for example).

 

in fact you will have to adjust the MCP speed once the window shows up (isn't blank anymore) cos you won't be able to get it to go back into VNAV speed (blank) again (unless you go around).

 

Since you have no control over the actual speed when in the VNAV mode (speed window blanked) you have to leave this mode if you get a speed instruction from ATC (ie: "ABC123 Reduce speed to 220 knots, turn heading 150 to join the runway 17 Localizer" or "Cleared the ILS runway 34L, maintain 170kts or better to the outer marker".) You would obviously then stay in Speed hold mode till landing or going around.

 

Basics:

You can stay in VNAV (MCP Speed selection window blank) while deploying flaps. When you deploy flap 1, a marking (-1) will appear, and VNAV speed will set the speed bug (Magenta bug on PFD, not showing a number in MCP speed window) to that exact speed. When you reach that speed, if you deploy flap 2 (or 5 even, skipping 2) the green marking on the PFD will indicate flap -2 or flap -5 and the Magenta bug will move down to that mark, causing the autothrottle to slow the aircraft to that exact speed. Again wait till the speed is on the Magenta bug (which will correspond to the flap you have deployed) before deploying more flap.

 

VNAV will handle the speed changes on it's own until it drops out (indicated by the Speed window on the MCP coming up with a value other than blank). This mode change WILL happen on every flight, generally somewhere after selection of any flap value higher than 15, although I believe there is a height value associated with it too.

 

At this point you WILL need to change to your Vref(+additive) speed because the VNAV will drop out prior to getting to this setting. If you don't select a new speed it will stay at a speed near 160kts.

 

Trent Hopkinson

Hi

 

It starts with good planning, if the profile is not constrained or messed up by ATC then most A/C will present you at the ILS (or other app) tip in point at the right speed.

 

If not then speed brakes, MCP/FCU speed and landing gear are your friends. Remember if you go faster you will descend faster (you still have to sort out the extra speed later)

 

Speed brakes are there to be used as much and as often as you like. You'd look a bit silly going around due unstable approach because you're afraid to use the speed brakes.

 

Flaps are to keep you alive when you have to slow beyond each min flap speed or green dot, and to get you to Vapp/Vref.

 

 

 

David

You should not use speed brakes and flaps in combination to reduce airspeed. Indeed you will find many checklists that indicate such. Here's an example:-

 

VC10 FLYING MANUAL

APPROACH CHECK

 

Flap Isolate Switches Normal

Flaps/Slats Selected T.O./20°

 

APROACH CHECK – AMPLIFIED

Flaps/Slats

Ensure IAS is less than 229 kts. Then select the Flaps/Slats

to 20°. E/O to monitor the selection and confirm ‘running’

by reference to position indicators and hydraulic panel MIs.

Check that the selected position is achieved by reference to

position indicators and MIs.

Speedbrakes

Select IN immediately after moving the flap/slat selector

lever to T.O.20°.

 

You can see here that the flaps are inhibited at altitude. Once within flaps speed range the practice is to only use the speedbrakes on on landing!

There is a method for a VNAV flight: If you e.g. need to have 240kts/10'000ft in your descend and your FMC tells you "DRAG REQUIRED" it doesn't necessarily mean you have to deploy the SPEEDBRAKES, but you can also press SPEED INHIBIT next to your speed selection and accelerate a little (by 5-7kts). I know you actually want to slow down, but since the physics says "the drag increases with the square of the speed" it means that you will be down faster AND have more time to reduce the speed! (finally: same altitude but less speed - works the same way with the speedbrakes, it's just a different method)

 

I saw a video on youtube about this shortly after the NGX was released, but can't find it anymore, sry

Every flight I've been on no matter if it's a CRJ, ERJ, 320, 737 the speedbrakes are used extensively during descent. They are not fully extended of course but used as to maintain a certain speed and then let go, at one point I see the flaps being deployed in increments and that tells they have reached a target and it safe do so according to policy and specifications. The flaps are fully extended at some point on final and the landing gear comes out. I have a number of cockpit videos, Air Canada, Westjet etc all this is very clear when I watch. When in FS9 I follow the same procedures and it's all clock work to me.

Thanks Trent for your explanation.

I was referring to exactly that phase of flight (below 220 knots until touch down).

 

Christos

Every flight I've been on no matter if it's a CRJ, ERJ, 320, 737 the speedbrakes are used extensively during descent. They are not fully extended of course but used as to maintain a certain speed and then let go, at one point I see the flaps being deployed in increments and that tells they have reached a target and it safe do so according to policy and specifications. The flaps are fully extended at some point on final and the landing gear comes out. I have a number of cockpit videos, Air Canada, Westjet etc all this is very clear when I watch. When in FS9 I follow the same procedures and it's all clock work to me.

 

That's how it is! If you use flaps as "speedbrakes" then you risk ripping them off the a/c or even more interestingly they might take the wing with them! It's happened!!

There is a method for a VNAV flight: If you e.g. need to have 240kts/10'000ft in your descend and your FMC tells you "DRAG REQUIRED" it doesn't necessarily mean you have to deploy the SPEEDBRAKES, but you can also press SPEED INHIBIT next to your speed selection and accelerate a little (by 5-7kts). I know you actually want to slow down, but since the physics says "the drag increases with the square of the speed" it means that you will be down faster AND have more time to reduce the speed! (finally: same altitude but less speed - works the same way with the speedbrakes, it's just a different method)

 

I saw a video on youtube about this shortly after the NGX was released, but can't find it anymore, sry

 

I was looking for that same video (if it's the same one you're thinking about). I believe it was done by one of the PMDG developers, but I might be wrong. Perhaps someone can remember the exact details and post a link.

It was done by a real world 737 pilot adviser to PMDG, Jack was his first name (I forget his last). But yes I have been using that techique with great success, thanks Jack!

 

 

EDIT Found the threads buuuut....

 

http://forum.avsim.net/topic/344441-do-you-really-need-speedbrakes-video/

 

http://forum.avsim.net/topic/344559-do-you-really-need-speedbrakes-video-part-2/

 

The videos don't work anymore.