Should flaps cause more nose down pitching moment when deployed?

[Pilum]

There seems to be something strange with the trim change when flaps are deployed in the Me109K4: Trailing edge flaps should give a nose down pitching moment when deployed while in DCS there is a nose up pitching moment.

 

The nose down pitching moment is due to the fact that the extra lift generated by the flap acts aft of the center of gravity which causes a nose down moment. This effect is to some extent offset by the increased downwash on the tail which however is not large enough to cancel out the nose down moment which consequently needs to be trimmed out. At least this is the case in most aircraft I believe.

 

In fact IIRC then this was why the trim and flap wheels were placed so close together on the Me109’s: When deploying the flap the pilot would grab both wheels and move them togther which would deploy the flaps while at the same time moving the tail plane incidence to cancel out the trim change caused by the flaps. So IRL the pilot would spin both wheels counter clockwize when deploying flaps.

 

However, in the DCS Me109K4 it is the other way around: The flap wheel is spun counter clockwize to deploy flaps while the trim wheel needs to be spun in the other direction to trim out the nose up moment caused by the flap deployment.

 

This indicates to me that there is a fundamental issue here with the DCS Me109K4: How come we get a nose up moment and not a nose down moment when flaps are deployed?

Edited December 6, 2014 by Pilum

[Anatoli-Kagari9]

Thx Pilum,

 

actually even the DCS K4 manual mentions, on Page 110 - "FLIGHT CHARACTERISTICS" section:

 

 "When you lower the flaps, the airplane becomes nose heavy. "

 

They'll certainly fix it on the next patch ;-)

[Crumpp]

If that is what the POH says, then that is what the airplane does....

 

However, TE flaps do not always cause a nose down moment.

 

In isolation they will but since we don't fly 2D airfoil sections but 3D airplanes, the downwash across the tail greatly influences the pitching moment.

 

In other words, in a real airplane the nose might pitch up and it might pitch down.

[Pilum]

Thx Pilum,

 

actually even the DCS K4 manual mentions, on Page 110 - "FLIGHT CHARACTERISTICS" section:

 

 "When you lower the flaps, the airplane becomes nose heavy. "

 

They'll certainly fix it on the next patch ;-)

 

Yes let's hope they do fix it. It looks at bit strange when you deploy flaps and trim and the outer wheel spins counter clockwize and the inner trim wheel clockwize. Doing that while flying IRL would require a great deal of finger dexterity. :music_whistling:

 

Actually the British RAE conceded that the flap/trim arrangement with the control wheels placed together was one of the good points on the Me109 because you trimmed at the same time you deployed or raised the flaps by spinning both wheels in the same direction. Otherwize they were rather sparing in their praise of the Me109E as I recall it :smilewink:

Edited December 8, 2014 by Pilum

[NineLine]

The FM is in Beta (as is everything else).

[Chappie]

Flaps don't pitch the nose down conventional aircraft. Flaps increase the mean chord line angle relative to the wind so application will result, initially an increase in pitch which is why one should pull power in a descent and drop flaps.

 

Also, when flying with flaps extended even at four to six seconds of application, the nose had to be pushed down because, again, the chord line of the wing has changed and increases wing lift and drag.

 

As for the animated direction of the wheels for flap and trim application, only matters what your flight controls have been set up with. Just remember to increase forward trim with flap applications.

[Pilum]

The FM is in Beta (as is everything else).

 

So does this mean you have had some indications that this will be corrected then?

 

Here is some more information further supporting that there should be a nose down trim change when deploying flaps:

 

British Royal Aircraft Establishment report RM2361 Me109E handling and performance evaluation, by M B Morgan, September 1940:

 

”The juxtaposition of the tailplane-adjusting wheel and the flap-control wheel was also considered an excellent feature, as the wheels may be operated together with one hand and the change of trim due to flaps thereby automatically corrected.”

 

The same report say’s that a total of 5,75 revolutions of the trim wheel were needed to move the tailplane from the max incidence of +3.4 degrees to –8.4 degrees. So it seems the Emil at least could increase the tailplane incidence as far as to 3.4 degrees positive.

 

From article ”Four of the finest” in Royal Air Force Yearbook 1975: English test pilot Captain Eric Brown on the captured Me109G6 he flew in 1944:

 

”The flaps were raised manually by means of the outer of two concentrically-mounted wheels to the pilot’s left, the inner wheel adjusting the tailplane incidence. Thus the wheels could be moved together to counteract the change in trim as the flaps came up.”

[NineLine]

So does this mean you have had some indications that this will be corrected then?

 

I have indication that the FM is in beta, thats all that means. Yo-Yo would be the one to ask if it will be fixed or needs fixed, etc... I'll see if I can sway him to comment here, or to give me some info.

[Yo-Yo]

So does this mean you have had some indications that this will be corrected then?

 

Here is some more information further supporting that there should be a nose down trim change when deploying flaps:

 

British Royal Aircraft Establishment report RM2361 Me109E handling and performance evaluation, by M B Morgan, September 1940:

 

”The juxtaposition of the tailplane-adjusting wheel and the flap-control wheel was also considered an excellent feature, as the wheels may be operated together with one hand and the change of trim due to flaps thereby automatically corrected.”

 

The same report say’s that a total of 5,75 revolutions of the trim wheel were needed to move the tailplane from the max incidence of +3.4 degrees to –8.4 degrees. So it seems the Emil at least could increase the tailplane incidence as far as to 3.4 degrees positive.

 

From article ”Four of the finest” in Royal Air Force Yearbook 1975: English test pilot Captain Eric Brown on the captured Me109G6 he flew in 1944:

 

”The flaps were raised manually by means of the outer of two concentrically-mounted wheels to the pilot’s left, the inner wheel adjusting the tailplane incidence. Thus the wheels could be moved together to counteract the change in trim as the flaps came up.”

 

How can you comment that G and K had +1.16...1.83 to -6 degrees range, and it sufficient to the plane having even wider range of speeds? And, regarding to Mr. Brunotte, there was no use to retrim the plane (G) - once trimmed to cruise it was perfectly controllable within all balance and speed conditions.

[Pilum]

How can you comment that G and K had +1.16...1.83 to -6 degrees range, and it sufficient to the plane having even wider range of speeds? And, regarding to Mr. Brunotte, there was no use to retrim the plane (G) - once trimmed to cruise it was perfectly controllable within all balance and speed conditions.

 

I'm not sure but I think the reduced upward throw from 3.4 to 1.17 deg could be due to the later me109's being more nose heavy due to the heavier engine installations. IIRC then there was ballast in the tail in the K4?

 

Regarding Mr. Brunotte statement, I think the DCS K4 is also controllable in a wide speed range so I see no problem there.

 

In addition: My main concern is not the trim range (although it would of course be nice to be able to completely trim out at high speed if this is historically correct ;)) but the trim change due to flap deployment and that was why I posted in the first place.

[Yo-Yo]

I'm not sure but I think the reduced upward throw from 3.4 to 1.17 deg could be due to the later me109's being more nose heavy due to the heavier engine installations. IIRC then there was ballast in the tail in the K4?

 

Regarding Mr. Brunotte statement, I think the DCS K4 is also controllable in a wide speed range so I see no problem there.

 

In addition: My main concern is not the trim range (although it would of course be nice to be able to completely trim out at high speed if this is historically correct ;)) but the trim change due to flap deployment and that was why I posted in the first place.

 

Will be exactly as it was measured... though I do not like the way they process the raw in the Soviet test center. :) But I processed it further. :) So, I have it convenient to deal with.

[gavagai]

I'm not sure but I think the reduced upward throw from 3.4 to 1.17 deg could be due to the later me109's being more nose heavy due to the heavier engine installations. IIRC then there was ballast in the tail in the K4?

 

Sure, that was normal for installing a heavier, more powerful engine. Spitfires had ballast, too.

[Pilum]

Sure, that was normal for installing a heavier, more powerful engine. Spitfires had ballast, too.

 

Yes, but it would be interesting to know how much ballast they but in there and where the c.g ended up. So what we need is a so-called "Ladeplan" for the K4 showing weights and balance.

[Pilum]

Will be exactly as it was measured... though I do not like the way they process the raw in the Soviet test center. :) But I processed it further. :) So, I have it convenient to deal with.

 

OK, I'm not sure how I should interpret this? Does it mean you are looking into the trim and flap moment issue? :)

 

Is the measured Me109G data you are referring to above from the attached report?

 

Also, in the current DCS Me109K4 where is the center of gravity located when fully armed and full internal fuel load?