Archived

This topic is now archived and is closed to further replies.

Oliver Branaschky

Flaps 1 producing ridiculous amount of drag and lift

Recommended Posts

Hi all,

 

ever since installing a couple of new liveries (American Airlines, Southwest, TUIfly; all from the PMDG website) I'm having this strange issue when taking off with flaps 1 and when selecting flaps 1 on approach, respectively.

 

This flaps setting produces a very huge amount of lift and drag. For instance, on climb out, I'm used to lower the nose just a couple degrees in order to accelerate towards flaps up speed. Lately, with these new liveries installed, I have to lower the nose significantly below the horizon to even start accelerating. This only happens with flaps at the 1 position. Flaps 5 is fine.

 

The same applies on approach: I was approaching Palma de Mallorca LEPA today, and once I selected flaps 1 (speed initially around 240 KIAS) speed began to drop rapidly, while the nose was lowered (still in VNAV with A/P engaged) to around -10 degrees.

 

I've exclusively flown the Air Berlin livery for about 8 months and never had this happen before. It only happens with all the new liveries. (Hm, come to think of it, I haven't tried the Air Berlin one after installing the other ones...) Anyway, I don't think this behavior is normal - or is it? Anyone else ever seen this?

 

Thanks for all hints and tips,

 

Oli

 

 

Oliver Branaschky

Share this post


Link to post
Share on other sites
Help AVSIM continue to serve you!
Please donate today!

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? ?

Share this post


Link to post
Share on other sites

I haven't tried a reinstall yet. It does happen at slower speeds (during take-off, as described above). Besides, I don't think 240 KIAS is excessive, Flaps Limit is 250 KIAS, after all. It may not be the most proper usage, but it's still within limitations.

 

 

Oliver Branaschky

Share this post


Link to post
Share on other sites

Are you noticing a difference between your vanilla NGX installation and after you installed liveries? Haven't had any program or something playing with lift scalars in the .cfg file or anything? How's your payload loading? Not noticing any way-forward CofG's or anything? Are you seeing the strange attitudes only in descent, or also level flight?

 

 

The leading edge devices (flaps+slats) on these things are very effective, and are extended whenever the trailing edge devices are extended (even partially). Flaps "1" may not seem like a appreciable amount. At flaps 1; with the inboard leading edge flap extended fully, and the slats intermediately, you have a pretty appreciable camber change there. At that speed (~240 kias) you got a lot of airflow as well. With a forward CofG and that high speed, that may be your reason for what seems like strange behaivour.

 

Try playing around with different liveries at different speeds/configurations.

Share this post


Link to post
Share on other sites

As far as I am aware the livery itself has nothing to do with the flight characteristics of a given model. However, installing a livery is the same to installing "new airframe in the hangar", different copy if you will. The new copy has its default load distributions and equipment set differently to the other ones well at least until you set the options.

 

Maybe it is the different load setting for the new planes than the ones you're used to? There should not be any difference of the flaps 1 behaviour among the liveries.

Share this post


Link to post
Share on other sites

Flaps 1 should cause no drag to speak of. That's for lift and reducing the stall speed. If you are getting a lot of drag from that, I'd "step outside" the aircraft as you are going from Flaps 0 to Flaps 1 and see if you really are getting 1 degree of flap. You'll know because 1 degree just moves the flaps aft, not down. The slats too should come out. Try observing what's going on from outside. Something somewhere may be screwing up and in fact you are getting about 10 or so degrees of flap instead of 1.

Share this post


Link to post
Share on other sites

Flaps 1 should cause no drag to speak of.

 

Trailing edge flaps themselves will indeed create small to no drag. But those leading edge devices... those are not that small...

Share this post


Link to post
Share on other sites

No they're not, but they generate lift only. If they produced any significant drag, you'd have CofG problems on extension. All they do is increase the camber of the wing, generating greater lift. The drag coefficient from those is negligible.

Share this post


Link to post
Share on other sites

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).

Share this post


Link to post
Share on other sites

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.

Share this post


Link to post
Share on other sites

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.

Share this post


Link to post
Share on other sites

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.

Share this post


Link to post
Share on other sites

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.

Share this post


Link to post
Share on other sites

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

 

That's recommended flap extension speed and flaps command speed.

Share this post


Link to post
Share on other sites

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.

Share this post


Link to post
Share on other sites

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.

Share this post


Link to post
Share on other sites

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.

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites

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.

Share this post


Link to post
Share on other sites