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Oliver Branaschky

Flaps 1 producing ridiculous amount of drag and lift

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Guest BeaverDriver

Actually, come to think of it, I don't think the slats extend until you go to Flaps 2 or even 5. I know the old 727's wouldn't, and I seem to recall not seeing the slats caution light not illuminate until I go greater than Flaps 1 on the 737. I'm not at home now so I'll check tonight if I get time.

 

Now I don't mean to imply there's no drag with the slats, but it is minimal. Certainly not in the order of what the OP is complaining about. On the NGX, I feel virtually no difference when I go flaps 1 or even 2, except a very slight pitch up. I'm not usually extending flaps until nearing the FAF anyway unless ATC has me slowing down below 180. To that point, if I need drag, I'll use the speed brakes, which is, after all, their function (but they sure don't add lift <LOL>).

 

well... nope. The purpose of leading edge devices is not to generate additional lift, but rather to allow for higher AoA (which leads to higher potential lift, but not higher lift at the same airspeed, and also makes possible lower airspeed due to altering stall behaviour).

 

OK, you are going to have to quote me sources on that one! In all the ground schools I took that goes against everything I learned. I'll re-ask my friend who assisted me on this question as well, since he's a 757 and 767 senior captain. I think he'll disagree, but I'll find out and let you know.

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The LE devices extend to their first position with flaps 1 on the 737. I do agree however that what OP is experiencing is beyond what should happen.

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I had the issue you described but it was due to fsuipc. If you don't have issues at flaps 0 its not the same problem.

 

Also, flaps 1 at 240 kts is excessive and not proper usage.

Max speed for flaps 1 is around 210 kts.

 

Does the issue persist after a reinstall, and does it happen at slower speeds? ?

 

Just to be clear max speed for flaps 1 is 250Kts. My company has a self imposed max speed of 240Kts. In real world operations it is not at all uncommon to extend flaps near the 240kt limit.


Tom Landry

 

PMDG_NGX_Tech_Team.jpg

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Just to be clear max speed for flaps 1 is 250Kts. My company has a self imposed max speed of 240Kts. In real world operations it is not at all uncommon to extend flaps near the 240kt limit.

 

Well I didn't know that. Always went off of the flap tick marks on the speed tape.

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Those tic marks are the Boeing recommended minimum speed for each configuration. You'll notice when you start extending flaps the red barber pole will move down to the current flap settings maximum speed. You'll also see a yellow hook appear which shows the maximum extension speed for the next flap setting. One thing to remember is that the yellow hook only gives the speeds for flaps 1, 5, 15, 30, and 40. Even though it doesn't show for all flap settings its still a nice to have reference.


Tom Landry

 

PMDG_NGX_Tech_Team.jpg

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One thing to remember is that the yellow hook only gives the speeds for flaps 1, 5, 15, 30, and 40.

 

1, 5, 15, 30 with CDS Software Upgrade - BP02/04/06, which is installed on NGX.

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Guest BeaverDriver

OK, just spoke to my friend who flies 757's for a major carrier. The drag from slats and 1* of flaps is extremely minimal. They are there to increase wing camber which generates more lift, making it more maneuverable at slower speeds. The jet's wing is designed to operate at very fast speeds. You can't have it both ways so they are rather crappy at slow speeds. Thus, the slats lower the stall speed and allow you to fly slower than you otherwise could without them. He also noted that some aircraft don't extend leading edge devices until Flaps 5, some even have a Flaps 0 that extends the LE devices only, and some extend as soon as you start extending the flaps at all. But insofar as drag goes, slats produce a LOT less than flaps, and frankly flaps don't even start making much of a difference until you get beyond 20 degrees. That's probably why on most floatplanes we used 20 to 25 degrees of flap to take off with, and due to the lower inertia, you'll feel the effects of drag from flaps more on those than you do on the big machines.

 

Bottom line is, something is up with the OP's system. You should barely notice any change at all when going Flaps 1. Like I said, I'd stand outside behind or above the aircraft (you can do this on the ground) and see if your flaps really are going to 1*. If not, you need to find out why. If so, you need to find out why so much drag is happening. Now, this will sound really dumb, and I'm not insinuating you're "not all there", but for sure you aren't accidentally extending the speed brakes instead, are you? I know, dumb question, but hey, we've ALL done one thing thinking we've done something else. It's human nature.

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OK, thank you all for your input. Good to know that this behavior is obviously not normal. Also good to know I'm not misusing the flaps ;-)

 

I will try

 

a) whether or not the problem also occurs with the "original" Air Berlin livery and the PMDG ones,

B) whether or not there's any visual hint of the flaps extending beyond the indicated Flaps 1 position, and, if a) and B) don't shed any light on this issue,

c) re-install.

 

At first, I've also thought about the speedbrakes. But that wasn't the reason, either. Should have gotten a take-off config warning on take-off, anyway, shouldn't I?

 

I'll report back.

 

So long,

 

Oli

 

 

Oliver Branaschky

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Guest BeaverDriver

Yes, very true. If you had the speed brakes out on takeoff, for sure you should have had a warning (although I've never tried this so I'm speculating :smile:).

 

Now, I did look at the plane from the outside last night as I was sitting on the ramp and extended flaps to 1, then 2, then 5. The slats do move a tiny bit at flaps 1, but really they are just coming out of their "parked" position. It's not until you get to at least Flaps 2 (and probably Flaps 5 - I forget now) that they extend beyond that. So they would have a negligible effect at Flaps 1 (and I would venture to say zero effect). You're getting a slight bit more lift at Flaps 1 as the flaps do extend aft a noticeable amount which will increase the wing area, but the overall effect in terms of drag should be none to minimal.

 

Anyway, good luck with this and let us know what you find out. I'm curious about this one.

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Now, I did look at the plane from the outside last night as I was sitting on the ramp and extended flaps to 1, then 2, then 5. The slats do move a tiny bit at flaps 1, but really they are just coming out of their "parked" position. It's not until you get to at least Flaps 2 (and probably Flaps 5 - I forget now) that they extend beyond that. So they would have a negligible effect at Flaps 1 (and I would venture to say zero effect). You're getting a slight bit more lift at Flaps 1 as the flaps do extend aft a noticeable amount which will increase the wing area, but the overall effect in terms of drag should be none to minimal.

 

Okay Glenn something is up with what you are seeing as that is all not really correct. There's a little confusion arising around here with what is actually going on with the surfaces when you select flaps one. Also, it's not really fair to say that these surfaces can increase lift without having an appreciable effect on drag.

 

Anyways, just to make sure everyone is on the same page, this is what your leading and trailing edge devices should look like at Flaps 1.

 

First, a little explanation/reading for ya:

 

A three-position spool-type control valve is operated by the flap control unit. The control valve ports hydraulic fluid (System B) to the leading edge flap and slat actuators. When the trailing edge flaps are between 1 and 5 units, the control valve ports pressure to fully extend the leading edge flaps and extend all leading edge slats to the intermediate position. When the trailing edge flaps are positioned to 10 units or more, the control valve ports pressure to fully extend all leading edge slats.

 

There is also an autoslat system that will fully deploy the slats when you are between 1 and 5 units, and at a predetermined high angle of attack.

 

Here your inboard leading edge flaps should be fully deployed. There is no "park"/intermediate position for these devices. Motion of the trailing edge flap drive system actuates the leading edge flap and slat control valve physically.

2012-9-6_16-29-46-370.jpg

 

Here are your outboard leading edge slats in the intermediate position, an trailing edge flaps at one unit.

2012-9-6_16-29-32-919.jpg

 

As for the drag question, that one's a little more tough. Anytime you see a change in wing area, camber, chord, and all sorts of other things, your are going to increase lift. When ever you increase lift, you increase drag. Period. There's no ifs aboot its. It's the whole nature of aerodynamics and induced drag. You guys are correct though in assuming it's not a linear relationship. All sorts of funky calcs com into play, so it's tough to really put the nail on how much drag you should be seeing with a given increase in camber/chord/wing area/airspeed...etc...etc. First you have to determine what the induced drag coefficient of your airfoil. I don't quite got the patience/know-how to sit down and calculate the 37's induced drag coefficient so I can't show you what the numbers actually are but it certainly isn't negligible. If you are really into it take a look for a program called Aximer. As you can see by the pictures we are seeing a pretty stiff increase in camber there. Especially with the inboard kruger flaps. The air isn't gonna like to have to work it's way all around those big boards...but it will find a way...at the cost of increased drag.

 

The 757 is a much different wing/airplane than all the 37 variants, so I personally think it's a bit of a stretch to compare. The 37's are something with a lot less momentum and a little less aerodynamic...."refinement" perhaps. The NG wing though is a great step above the Original's wings though.

 

But you are all on the right idea in trying to figure this out. I myself may take a rip as well here to see what I see with just Flaps 1 does. I'm really hoping it's a solvable issue though for Oliver.

 

I just wanted to clarify how the devices behave with different configurations.

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Okay, I did some tests and obviously, only the AirBerlin livery works as expected. A visual inspection reveals nothing out of the ordinary.

 

I'm lacking the proper time at the moment, but as soon as possible, I'm going to try some advice by Ryan which I read in another thread: deleting the FSUIPC.ini and letting it rebuild. The issue the other user had looked similar to mine, so I'm gonna give it a shot.

 

So long,

 

 

Oliver Branaschky

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Hi all,

 

I know it's been a while but I've finally found some time to try out Ryan's advice of deleting the FSUIPC4.ini. Guess what? It did the trick! All liveries are back to normal, finally.

 

I've sent both files - old and new - to Ryan for further analysis.

 

Thanks all, and see you around soon.

 

So long,

 

 

 

Oliver Branaschky

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