Flaps - could someone kindly explain something

[martinlest2 58]

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

[PHXMD-11 86]

 

 

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.

[pschlute 37]

 

 

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.

[bjratchf 80]

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!

[martinlest2 58]

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.

[pschlute 37]

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 ?

[kevinh 409]

 

 

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.

[martinlest2 58]

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

[martinlest2 58]

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...

[pschlute 37]

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.

[scandinavian13 5,192]

 

 

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?

[martinlest2 58]

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...

[pschlute 37]

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.

[martinlest2 58]

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

[martinlest2 58]

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