Realistic Drag during Flight?

[Matt00 0]

Hello all future NGX owners ;)In the old 737 I was always wondering how the drag works. My experience is that if the speedbrakes are extended the plane only decelerates very slow, also when using a low vertical speed. Is this an realistic behaviour or was this a not perfect realization of the speed brake function in the old bird?So, I would like to know how the NGX behaviour is in the case speedbrakes are extended? Does it react realistic? And what is realistic? Does the speed decreases faster or slower when speedbrakes are extended? In my opinion the break efficiency is too low but I am not a real pilot so please apologize if I am wrong ;)Is my objection legitimate or am I just a bad pilot?

[PHXMD-11 86]

I thought the speed was supposed to decrease quicker with speebrakes deployed and engines at idle. But what do I know? I'm just an aspiring pilot. And realistically, the speedbrakes on the NGX should be as realistic as it gets with PMDG...

[KristianN 10]

The word "speedbrakes" might be a little misleading when it comes to the Boeing 737NG series. If you deploy them below 10.000 feet you won't see the effect at all.... So if you want to slow down you better do it above 10.000. And even up there you just feel a little turbolense and a weak noise (and only a very small amount of slowing the aircraft down) - they simply do not provide the amazing brake experience some flight simmers are expecting. (Not pointing my fingers at anyone!)Where I fly, we have a word for the speedbrake handle.. Just don't remember what it is EDIT: Don't get me wrong. They DO work. Just not as much as someone would expect :(

[SpeedbirdA320FO 27]

The word "speedbrakes" might be a little misleading when it comes to the Boeing 737NG series. If you deploy them below 10.000 feet you won't see the effect at all.... So if you want to slow down you better do it above 10.000. And even up there you just feel a little turbolense and a weak noise (and only a very small amount of slowing the aircraft down) - they simply do not provide the amazing brake experience some flight simmers are expecting. (Not pointing my fingers at anyone!)Where I fly, we have a word for the speedbrake handle.. Just don't remember what it is EDIT: Don't get me wrong. They DO work. Just not as much as someone would expect :(

You're spot on. I know on the airbus using speedbrake is useless below FL200, if wr really have to slow up quick for something then wr usually use the gear, dropping that early does the trick - immensely draggy!

The word "speedbrakes" might be a little misleading when it comes to the Boeing 737NG series. If you deploy them below 10.000 feet you won't see the effect at all.... So if you want to slow down you better do it above 10.000. And even up there you just feel a little turbolense and a weak noise (and only a very small amount of slowing the aircraft down) - they simply do not provide the amazing brake experience some flight simmers are expecting. (Not pointing my fingers at anyone!)Where I fly, we have a word for the speedbrake handle.. Just don't remember what it is EDIT: Don't get me wrong. They DO work. Just not as much as someone would expect :(

You're spot on. I know on the airbus using speedbrake is useless below FL200, if we really have to slow up quick for something then we usually use the gear, dropping that early does the trick - immensely draggy!

[steve inwood 67]

Sometimes in the FMC you will notice Drag required...I'm sure it's something to do with the speedbrakes. Well deploy them in the air but im sure they only semi deploy as this is whats called drag, to help loose height and speed rapidly.But i may be wrong. Steve

[PHXMD-11 86]

Sometimes in the FMC you will notice Drag required...I'm sure it's something to do with the speedbrakes. Well deploy them in the air but im sure they only semi deploy as this is whats called drag, to help loose height and speed rapidly.But i may be wrong. Steve

I don't think you can select full in flight. Just once the mains touch down.

[KristianN 10]

You're spot on. I know on the airbus using speedbrake is useless below FL200, if wr really have to slow up quick for something then wr usually use the gear, dropping that early does the trick - immensely draggy!

It really is. I've also heard about colleagues starting to use flaps right after getting below 250 indicated. When you're really in need of drag the speedbrakes are, ironically, almost useless. So they started with flaps 1, then 5 etc etc.. Simply to increase drag.But as you say - the landing gear is VERY useful as well.

I don't think you can select full in flight. Just once the mains touch down.

Correct. The spoilers are fully engaged by main wheel spin-up, at least for the 737NG. Don't know about Airbus..

[badderjet 181]

It really is. I've also heard about colleagues starting to use flaps right after getting below 250 indicated. When you're really in need of drag the speedbrakes are, ironically, almost useless. So they started with flaps 1, then 5 etc etc.. Simply to increase drag.But as you say - the landing gear is VERY useful as well.

Interesting. Maybe it's a philosophy thing but I heard you'd actually slow down and THEN extend the flaps and not USE the flaps to slow down... I know flaps 1 are certified up to V_FE like 250ish knots or so, yet wouldn't you (normally) start to extend them at clean maneuvering speed (or UP speed in NG terms)?

[KristianN 10]

Interesting. Maybe it's a philosophy thing but I heard you'd actually slow down and THEN extend the flaps and not USE the flaps to slow down... I know flaps 1 are certified up to V_FE like 250ish knots or so, yet wouldn't you (normally) start to extend them at clean maneuvering speed (or UP speed in NG terms)?

You are correct. That is how it SHOULD be done.. Personally, I'm not a fan of using the flaps as speedbrakes. However, it IS possible. Same goes for the landing gear - it is not supposed to be used as a speedbrake - again, it IS possible. I believe both options are not being used unless you are in desperate need of slowing down, let it be per ATC or other factors requiring rapid decelleration etc...

Interesting. Maybe it's a philosophy thing but I heard you'd actually slow down and THEN extend the flaps and not USE the flaps to slow down... I know flaps 1 are certified up to V_FE like 250ish knots or so, yet wouldn't you (normally) start to extend them at clean maneuvering speed (or UP speed in NG terms)?

And to answer your question about when to select flap 1,Today it's very common to fly in clean config at green dot speed (clean speed). It's very economical. And by waiting with the flaps until you really need them, you use a lot less fuel (due to the less drag compared to flaps extended).Hope that answers your question :(

[flybywire0386 0]

Sorry to jump in here but in the interests of accuracy I'd love to know where some of this information comes from!Deploying Flap 1 in the airbus (320/1 anyway) at 250kts is likely to remove them from the wings as the VFE for this configuration is 230kts! Plus we would never even take flap that close to the limit unless absolutely necessary - as it increases wear and also leaves you susceptible to an overspeed warning if you hit a gust. On top of that selecting Flap 1 in flight in an airbus actually only gives you the first stage of slats, and therefore provides much more lift and next to no drag - so useless for slowing down. What it does do is move VLS (Lowest selectable speed) down the scale allowing you to use the speedbrakes more effectively. Finally the speedbrakes are far from useless below FL200 - which appears to be an arbiturary figure, and in fact at lower altitudes would provide more drag due to the thicker air. What does make a difference is speed, they are much more effective at higher speeds and become difficult to use as you approach green dot (best lift/drag ratio speed) as extending them often increases VLS above this speed - forcing you to retract them, slow down enough to take some flap, and then re-extend them if necessary.I do agree however that the landing gear does make an excellent speedbrake if required, though only once in my career have I seen it dropped near FL200 - and that was at 17000' when ATC left us in the sh*t with a very last minute runway change :PAnywho, off topic i guess as we're not talking about the NG!

[Tabs 2,790]

Regarding speedbrakes and slowing down in the descent, this is going to be a VERY noticeable difference with the NGX vs. other addons you may have.The speedbrakes are going to seem far less effective than what you're probably used to. You will not be able to extend the speedbrakes and slow down in a 2000 FPM descent with this rendition of the 737. This is entirely realistic and matches up with the actual Boeing performance numbers as well.The 737-800 in particular out of all the variants is an exceedingly slippery airplane even with the speedbrakes out - one of the hardest to slow down in the entire Boeing fleet in fact. One of our tech team pilots flies the 800 exclusively at his airline and he commented multiple times that in the real thing it's almost impossible to descend and slow down at the same time until you're around Flaps 10-15 with the gear out and already on the approach. Vangelis worked extremely hard with the flight model to get this aspect of it right.What all of this means is that you're going to have to learn about energy management and plan ahead. Make good use of the shallow VNAV DECEL segments (assuming ATC allows you to stay on path) to slow down and stuff like that. If you let the airplane get too far ahead of you, the speedbrakes are not going to save you - you'll be high and fast and you'll be doing a go-around.

[KristianN 10]

That us music to my ears, Ryan. I'm happy to hear you managed to model this quite well.

[markadeane 272]

To echo Ryan's point, the NG (and the -800 in particular) is extraordinarily slippery in the descent, and has humbled me more than once or twice. I think those of us with the majority of our time in the MD11 and 747 will REALLY notice this difference.Given the terrain and short runway, I've been using LOWI for a lot of my testing. Anyone who has been in there knows it has a fairly demanding approach, and I learned the hard way to make sure I have the energy management balance achieved nice and early.What's more, each descent profile is subtly different depending on environmental and payload variables so you can't just assume that what worked on the last flight will work on the next!

[Ivan Kovacevic 0]

Deploying Flap 1 in the airbus (320/1 anyway) at 250kts is likely to remove them from the wings as the VFE for this configuration is 230kts! Plus we would never even take flap that close to the limit unless absolutely necessary - as it increases wear and also leaves you susceptible to an overspeed warning if you hit a gust.

Actually, every component on any plane is required to be able to withstand 150% of the maximum limitation to even be certified to fly. So, the flaps at ~10% higher speeds would probably not rip them off the wings. ;)

[flybywire0386 0]

Actually, every component on any plane is required to be able to withstand 150% of the maximum limitation to even be certified to fly. So, the flaps at ~10% higher speeds would probably not rip them off the wings. ;)

Yeah sorry, figure of speech :(