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martinlest2

Flaps - could someone kindly explain something

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Hi. I have been reading through the pdf manuals but am still not 100%... Could a 'flap expert' kindly let me know if this is correct:

 

During taxi I set flaps to 22 degs using the 'dial-a-flap'. I set spoilers to armed and I get a green box...After take-off, and when I pass the FR marker, I retract flaps - there only seems to be one increment, from 22 degs to slats (what happened to 15 degs?). Then, passing the SR mark I retract the slats... basically OK?

 

The green indications 'F35', just above 'FR', and then also 'GE' and 'SE'. These have no significance after take off, do they? They are only for descent, no?

 

I also sometimes find that, even though I have set the trim, I end up far too nose high and I cannot gain speed. Could that result from incorrectly entering data from the MD-11 load utility into the FMC? I have learned not to set the trim to the value shown in the FMC TO/APPR page as that always leads to a very nose-high attitude. I set it to a minimum to get a green indication on the System Display.

 

OK, thanks in advance for any advice.

 

Martin

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there only seems to be one increment, from 22 degs to slats (what happened to 15 degs?).

 

You need to manually reset the dial-a-flap seletor to 15.

 

 


Then, passing the SR mark I retract the slats... basically OK?

 

Yes.

 

 

 


hese have no significance after take off, do they? They are only for descent, no?

 

Unless you are returning to the airport after takeoff, those speed bugs are just there to inform you of maximum airspeeds.

 

 

 


I have learned not to set the trim to the value shown in the FMC TO/APPR page as that always leads to a very nose-high attitude.

 

The trim settings in the FMS (barring incorrect numbers by you) are accurate. If you takeoff at low weights, the MD-11 is a very powerful machine and will require a high nose-up attitude to maintain airspeed.

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I also sometimes find that, even though I have set the trim, I end up far too nose high and I cannot gain speed

 

I assume you are still hand flying at this point. You need to establish your pitch attitude to maintain your initial climb speed (V2 +10/20). Sounds like you need to pull back less on the yoke.

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When passing flap retract speed, retract the flaps (callout should be Flaps UP, not RETRACT) when passing slats retract speed, retract the slats. There is no increment to go to!

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Thanks for the comments. I think that this must be something I am doing (sometimes, not always) and I am trying to figure out what.

 

If I set the indicated trim I always get a far worse situation that if I set it just into the green - such a high angle of attack the speed bleeds off fast (you can see from the spot view that it's going towards a stall). If I set trim just into the green, then a lot of the time I am fine.

 

Yes, I hand fly until around 3500' usually but I have to push the nose down quite heavily, even though I had set it only just within the green, or I am at 30 degs nose up before I know it. Once I get a reasonable pitch (to about 1500'/min, to gain speed) I can set the V/S and AP and I am good to go.

 

It may be that I am not being careful enough on occasion noting the loadedit figures into the FMC - I will try a few more flights over the next few days and be precise. As I say, quite often the take offs go just fine. I can't think what else would make the difference on these occasions.

 

Comments about flaps noted and understood - thanks again.

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What are your centre of gravity numbers from the load manager ?

 

Are you setting the fuel system to auto so it will set the tanks correctly ?

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Yes, I hand fly until around 3500' usually but I have to push the nose down quite heavily, even though I had set it only just within the green, or I am at 30 degs nose up before I know it. Once I get a reasonable pitch (to about 1500'/min, to gain speed) I can set the V/S and AP and I am good to go.

Required trim changes with airspeed and as you retract flaps and slats. Even with the correct trim set for takeoff you will still need to retrim as you climb and accelerate.


Are you entering ZFW and ZFWCG correctly during pre-flight? If not that could affect the calculated takeoff trim.

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Hi. I have been managing all systems manually (to get a bit more chance at user input), and that has worked fine on many flights. I will try going back to automatic mode for a few flights, but as things have worked out just fine with manual set for all systems (and no errors showing in the SD), I am not sure that's the issue.

 

Here is some of the load manager data from recent flights (which I scribble down before closing it):

 

ZFW: 407.8; 383.4; 359.5

ZFWCG: 19.6; 23.1; 21.7

TOGW: 576.2; 551.9; 528.0

TOCG: 22.7; 25.3; 24.4

 

all of which I have correctly entered into the FMC (I am 99.99% sure I am doing that bit right!)

 

I need to fly a few more flights to test things out though..

 

Martin

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OK, just started a flight from RCTP with the freighter version (the version I mostly fly) and there were no real problems, even though I have the systems set to 'manual', and adjust them myself. The only thing is that, even though I set the trim, as I have said, to just into the green rather than the much higher figure indicated in the SD, whilst I am hand-flying the plane, I have to push the nose well down with the joystick and keep applying downward trim to keep the pitch below 20 degs up. Is that normal? If not, any ideas what I can change to make the a/c less keen to go nose up? I was very careful to apply all the settings from the load editor to the FMC...

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Your weights and COG numbers look fine. No it is not normal to have to push well down to keep the nose from going too high.

 

What setting is the FMC telling you to use for elevator pitch trim for a 575,000 lb TOGW ?

 

What flap setting and FLEX thrust setting are you using?   I had a quick look at TOPCAT and it suggests between Flap 17-25 and  between 40-46 degrees FLEX thrust to give a +500 foot runway t/o margin at the four runways at RCTP.  .

 

One final point, how are you assigning/calibrating your joystick elevator axis ? The PMDG MD-11 models the LSAS system on the aircraft, and you should not use "direct to FSUIPC" for elevator/aileron assignments with this aircraft.

 

I also suggest you leave the fuel set to auto, unless you are fully conversant with balancing the tanks yourself.

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If not, any ideas what I can change to make the a/c less keen to go nose up?

 

Are you setting the performance data before, during, or after the aircraft is fully fueled?

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Hi. I set the performance data before I load the aircraft (usually when I am at the gate with the default Cessna, which is how I usually start flights these days) and then choose save to file.

 

I am setting FLEX, in the CDU setup, to the temperatures shown in my ActiveSky data - i.e., as it is. The last few flights I have entered (TO/APPR page) about 40 degs F.... and then set the OAT to the same. (Does it matter if I use degs C for the OAT, if it equates? You have to specify with an F or a C anyway, of course). I use dial-a-flap to set 22 degrees usually.

 

I did switch the fuel to auto, but it made no difference this flight, the nose really wants to go up and up, if I let it. It's mostly controllable, but definitely not what should be happening...

 

One final point, how are you assigning/calibrating your joystick elevator axis ? The PMDG MD-11 models the LSAS system on the aircraft, and you should not use "direct to FSUIPC" for elevator/aileron assignments with this aircraft.

 

Er, long time since I set this up! Please remind me what I need to do to check/change this. (I engage YD and LSAS as I line up on the runway)...

 

Thanks again for taking time to reply...

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From what i recall you can only set FLEX in degrees Celsius. The figures i quoted are Celsius. You should just key in 40.

 

Elevator/aileron  can be set either through FS9 controls, or if you are using FSUIPC you need to select "send to FS as normal axis" from the assignment page. It would help if you can tell us how you are assigning and calibrating the elevator at the moment. You may be using both FSUIPC and FS9 controls which may be your problem. I would start by removing the elevator/aileron assignments in FSUIPC and assign them in FS9 controls and try a takeoff again.

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The FLEX is always entered in degs F. The tutorial pdf suggests entering 54 (that wouldn't be degs C). If you enter a higher than ambient temp, thrust is reduced. The OAT can be either but you have to format it with either C or F after the figure.

 

I haven't assigned any controls at all to FSUIPC. I use the X52, which is programmed to use the FS9 keyboard commands, for elevators and pitch control

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Well, I am totally confused. This didn't use to happen, as far as I recall. Still the plane wants to go very nose high as I hand fly it - I can keep it within OK limits with yoke and trim as far down as possible (I ran out of trim this time).

 

Why does the a/c want to pitch up like this - I am gentle with the roll and try to maintain under 20 degs of pitch. (The MD11 flies more nose up than most planes, I think, so it looks a bit worrying from spot view, even when all is OK). With Autoflight on, then everything becomes controllable.

 

Maybe I should try some different values in the CDU entries? What would make a difference. Oh, I am entering a high CI value (just thought of this this moment, as I am typing here!) - 120. That could cause the problem, no? I should try 50 next time ....

 

Martin

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The FLEX is always entered in degs F. The tutorial pdf suggests entering 54 (that wouldn't be degs C). If you enter a higher than ambient temp, thrust is reduced

 

FLEX temperature can only be input in degrees celcius. There is no option to use F instead. The range you can enter is from current ambient to 70 degrees celcius.

 

The tutorial is indeed suggesting 54 degrees celcius.

 

The reduced thrust is the whole point of entering a FLEX temperature.

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Oh, OK! I was sure I had read somewhere that this entry was degs F, but perhaps not.
 

 

The reduced thrust is the whole point of entering a FLEX temperature.

 

 

 

I know (I said that somewhere above), but in practice it makes little difference for the purposes of this discussion, as for the past several flights, (with the nose-up issues), I have been adding the current temperature in FLEX, in degs F, i.e. about 55.

 

Is it the difference between the FLEX entry and the OAT entry that has an bearing on the thrust, or is that difference between FLEX and the ambient temperature in the PMDG model not relevant, thrust being purely based purely on the FLEX value one enters? In other words, I have been using about 55 for FLEX and 10C or so for OAT. If I use the same figure for FLEX but change OAT to, say, 45 degs C, would that impact the TO thrust? I have been assuming yes.. (Always referring to what's modelled in the PMDG, rather than real world).

 

I am going to try changing the CI, as that is one thing I have been doing differently...

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I don't know what bearing the OAT input will have if any. You should always use the correct OAT anyway.

 

If you have been using 55 C for FLEX you will be using a reduced t/o thrust so that is not what is causing your pitch problems.

 

I would suggest you recalibrate your joystick. Make sure you have nothing set up in the saitek software for elevator axis.or delete any if you have. Then without starting FS9 go to your windows "devices and printers" section and calibrate your joystick axes. Then open FS9  and in the assignments section do the same. Then delete and reselect the joystick axis for elevator, setting the null zone and sensitivity as appropriate.

 

Start the sim and load the MD-11 with engines running, don't load the cessna first. In spot view have a look at the elevator movement and see if it looks right.

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Hi again. The problem there is that I have no such issue with any other a/c, including other PMDG planes, only the MD11. The X52 is calibrated fine, I believe, with or without FS9 running, I checked this just yesterday.

 

I probably need to make a Saitek profile specific for the MD-11... if I delete elevator axis globally, that will 'mess up' other a/c (which currently respond just fine to the X52 when I rotate and thereafter: actually the MD-11 rotates fine too, it's afterwards that things go slightly awry).

 

If I also delete elevator control for FS9 assignments, as you suggest, then you mean I need FSUIPC to take over this function for all a/c?

 

The bottom line is that I doubt all the changes to my X52 and flight control setup can really be necessary (the areas you describe I am not at all confident about in any case - I am pretty sure I should just end up with a/c no longer responding to any elevator commands!), because last time I flew the MD11 regularly (a long while back, as I had been living abroad until very recently, without the MD11 on my temporary, 'better-then-nothing' FS9 laptop setup), I know I didn't have this problem. And even last week, I flew it on some days with no such issue either, with my hardware settings just as they are now. I will carry on trying to fix this with settings in the software for now, anyway.

 

Thanks for the advice. Always appreciated.

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If I also delete elevator control for FS9 assignments, as you suggest, then you mean I need FSUIPC to take over this function for all a/c?

 

"Then delete and reselect the joystick axis for elevator, setting the null zone and sensitivity as appropriate."

 

He was saying that you should remove the axis and re-select it. To me, that's akin to the (usually useless) uninstall/reinstall technique to solve problems, but at least it's not as time consuming.

 

 

 


because last time I flew the MD11 regularly [...], I know I didn't have this problem.

 

This would imply that the problem lies elsewhere, then.

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OK, yes, you're right. I'll keep testing this with different entries in the FMC though first, as I say.

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Martin,

 

You say that you set the weight "manually'.  Does this mean that you are not using the MD-11 "Load Manager"?

 

Unless you are using a program such as Topcat, I highly recommend that you use the PMDG "Load Manager" once the aircraft is setting at the gate.  Load the MD-11 into your program from the startup screen.  I use "PMDG MD-11F Short Ground Turn".   Using the "Load Manager" load your weight using "2/3 Cargo" and your Fuel using the "Fuel Selector".  The "Load Manger" will give you the correct ZFWCG/TOCG readings.  Load these reading into the FMC and set your trim accordingly per the FMC.  Use 20 degrees flaps.  Don't use "Flex".

 

On Heavy jets fly the Flight Director, that is how it is done in the real world.  On retracting the Flaps, follow the green trend line.  What I mean by this is do not raise the flaps until the green trend line touches the "Pink" dot.  

 

Try the above and let me know how it flies.  The PMDG MD-11 flies very well and PMDG did an excellent job with it.   :smile:

 

blaustern 

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Hi, and thanks...

 

I don't think I said I set the weight manually (not even sure what that means) - I can't find any comment like that. I did say that I managed the systems on the overhead panel manually... Yes, I use the MD-11 Load Manager. However I am using it slightly differently from the way you describe: I set everything there before I load up the MD-11. Since there is the button to save the info to the aircraft.cfg file (is that optional or - I assume - essential?), nothing saved to that file after loading the MD-11 would be read (would it?). I presume the PMDG programme uses the data saved there at some stage. (Or not??).

 

I tried CI at 50 just now and I also switched the systems to automatic on the O/H panel, to see what happened. But no change, still I really have to push the nose down after take-off. I only read your reply a little later, so I am not sure what the FD was doing - I'll pay more attention next time, but my feeling is that if I follow the FD I'll be going up vertical, like a Saturn 5 rocket (not for long though!). But I'll check. Maybe not. It looks catastrophic though from outside - I never see an a/c at that attitude (except on 'Air Crash Investigation'!)..

 

The pitch problem, I repeat, is only apparent jsut after TO. The rotation is quite normal, there no question of tail scrape or whatever. And once I have pushed the nose down to under 20 degs and tamed the trim way down, the aircraft flies just great by hand, and also after, on AP. Yes, PMDG's detailed work on this is VERY impressive, a work of art really, I agree.

 

What is "PMDG MD-11F Short Ground Turn", BTW?

 

Oh, one more thing. When I enter the values from the load utility into the CDU on INIT p2 (the ZFWCG value into 'ZFWCG' and the ZFW value into 'BLST IN ZFW', the TOGW value that shows is always different from the one I noted down in the load edit utility. Do I over-write the value in the CDU with the one that I copied down from the load edit window?

 

:wink:

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I set everything before I load up the MD-11. Since there is the option to save the aircraft.cfg file

 

Running the load manager as an admin?

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I don't know - I don't actually right click on the shortcut and choose that option. I need to be doing that then? If so, I'd forgotten that point...

 

I usually choose Random Freight or load relatively lightly (as I think I said, I rarely fly the PAX version, as none are in service now and I'm a bit OCD about flying a/c that no longer fly in the real-world!!) with 1/3 fuel or less (usually rather more than I need for my flight, which are short or medium haul on the whole). I could try loading up more cargo, (maybe putting it in forward holds - though the programme would doubtless compensate for that of course). I wonder if the a/c would be so keen to climb so fast if it were quite a bit heavier... Shouldn't really make any difference in practice with this plane though, surely?

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