B-26

[skylane]

Hello!

I´m currently flying Talon´s PNG missions and got to the first one for the B-26.

All the Marauders made by Bismarck13 and Tango Romeo fly in a very nose-high attitude. I remember a discussion about the vw Lockheed Hudson some time ago, which had a similar issue. For this airplane the problem was solved with a modified airfile.
I have aired, but I don´t know what to change in the file to make th airplane fly in a "flatter" attitude. Could someone point out how it is done?

Thanks,

skylane

[Nole]

...your elevator trim control. :kilroy:

Many people simply ignore this very basic control which requires attention for takeoff, level flight at various throttle settings and landing. :salute:

[skylane]

Hi Nole!Thanks for the suggestion, but that's not the problem. What I tried to say is, I' m flying along in cruise flight, about 70% power, which gives about 190 to 200 mph, maintaining a constant altitude, and the airplane has about 10 deg nose up attitude, which seems quite unnatural to me. I tried a few other models of the B-26 in cfs2, and they fly in a much flatter, more natural attitude. There must be a way to set this up in the airfile, and that is the information I am looking for.skylane

[sc7500]

If you're feeling daring [and you don't have a copy of ACM 2,5 installed to try this visually], you can manually tweak the Center of Gravity [CG] setting in your [Aircraft.CFG] with a TXT editor:

[weight_and_balance]
max_gross_weight = 4466.6
empty_weight = 2922
reference_datum_position = 0, 0, 0
empty_weight_CG_position = 0, 0, 0 <<<

As always, a POSITIVE number in the RED location is Forward [Nose Down], a NEGATIVE number moves it aft [Nose Up].

TINY INCREMENTS ARE BEST - 0.25 at a time, Mate !

Make a copy of your [Aircraft.CFG] before you experiment - it will save you a major headache if things go awry !

Good Luck ! :salute:
SC
:kilroy:

[Captain Kurt]

It flies nose up because of three possible things in the flight model.

1. the wing incidence (angle of the wing cord relative to the centerline of the aircraft) is set at a negative angle. In cruise the wing will try to fly at a 0 degree angle. This is not likely to be set that way though it's possible. You would need Airwrench to see and fix that.

2. The flight model is such that the specified cruise speed is the speed which the plane is supposed to fly straight and level. If you are flying at a much faster speed it will likely want to start climbing hence the nose up attitude. This is why trimming is important and it was necessary in a real aircraft as well.

3. The most likely cause is the CG weight position is set too far aft. If the plane is tail heavy aft of the center of gravity it will fly tail down and therefore nose high. You can try tweaking the aircraft.cfg file to fix this. Look for this line in the aircraft.cfg file:

empty_weight_CG_position = 0.000, 0.000, 0.000

If it is not there, paste it in. Start adding to the first set of zeros like this:

empty_weight_CG_position = 0.230, 0.000, 0.000

Then test the aircraft at your cruise speed to see how it affected the attitude. Keep adding or subtracting the value until she flies level. Or at least relatively level as it seems other factors in the game cause small variation in the level flight - altitude, speed, and even the temperature you have set in your test mission can cause it to climb or descend slightly. I have found absolute perfection is not possible to achieve, but you can get a big improvement regardless.

It should be noted that for certain parameters - but evidently not all - the player aircraft flies by what is in the aircraft.cfg file and the AI aircraft flies by what is in the airfile. Fixing the aircraft.cfg miight not affect the AI plane's attitude in flight. You'll have to try it and see what happens.

[Captain Kurt]

Shoot SC7500, you type faster than I do. :icon_lol:

[peperez]

It flies nose up because of three possible things in the flight model.

1. the wing incidence (angle of the wing cord relative to the centerline of the aircraft) is set at a negative angle. In cruise the wing will try to fly at a 0 degree angle. This is not likely to be set that way though it's possible. You would need Airwrench to see and fix that.

2. The flight model is such that the specified cruise speed is the speed which the plane is supposed to fly straight and level. If you are flying at a much faster speed it will likely want to start climbing hence the nose up attitude. This is why trimming is important and it was necessary in a real aircraft as well.

3. The most likely cause is the CG weight position is set too far aft. If the plane is tail heavy aft of the center of gravity it will fly tail down and therefore nose high. You can try tweaking the aircraft.cfg file to fix this. Look for this line in the aircraft.cfg file:

empty_weight_CG_position = 0.000, 0.000, 0.000

If it is not there, paste it in. Start adding to the first set of zeros like this:

empty_weight_CG_position = 0.230, 0.000, 0.000

Then test the aircraft at your cruise speed to see how it affected the attitude. Keep adding or subtracting the value until she flies level. Or at least relatively level as it seems other factors in the game cause small variation in the level flight - altitude, speed, and even the temperature you have set in your test mission can cause it to climb or descend slightly. I have found absolute perfection is not possible to achieve, but you can get a big improvement regardless.

It should be noted that for certain parameters - but evidently not all - the player aircraft flies by what is in the aircraft.cfg file and the AI aircraft flies by what is in the airfile. Fixing the aircraft.cfg miight not affect the AI plane's attitude in flight. You'll have to try it and see what happens.

It's the wing incidence and is historically right. Remember, early B-26 versions has a lot of problems and, to gave a solution, the wing incidence changed.

Cheers

Pepe

[skylane]

Thanks for your ideas, guys! thinking about it, it is most probably the angle of incidence of the wing. At a given speed, the wing needs a certain angle of attack (angle between the wing's chord line and the relative wind) to create the necessary lift to carry the airplane's weight. If the angle of incidence ( angle between the chord line and the centerline of the airplane) is low, then the airplane will fly in a nose- high attitude.The center of gravity has an influence on the longitudinal stability of the airplane. The farther aft the CG, the more sensitive the airplane is to inputs from the elevator. Regardless of the position of the CG, the required AOA at a given speed and weight remains (almost) the same, so it has (almost) no influence on the attitude of the airplane in flight.Pepe, you say that they changed the AOI in the later models of the B-26. so I presume it was rather too low in the early aircraft, and the way the -A model flies is correct?

[bearcat241]

....so I presume it was rather too low in the early aircraft, and the way the -A model flies is correct?

Sylane, IMHO i think we're all a little too young and collectively inexperienced here in real Marauders to answer that question with any plausible certainty. But if you want to bypass Airwrench and "flatten" this manually with hand editing, open the air file in Aired and go to record 1204 Main Wing. There you'll find the AOI...set it to 1.000.

While you're in there, you might want to take a look at the horizontal stabilizer's incidence in 1205.

Hope this helps...

[sc7500]

...Shoot SC7500, you type faster than I do...

Ha ! And I have to do all my "typing" while competing for space with a trio of Jack Russels vying for chair time.... :icon_lol:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Just want to reiterate - I didn't mention the Wing AoA setting because I ALWAYS set it to 1.00 in AirWrench when setting up or tweaking a plane's flight characteristics.

That's become such an ingrained habit [most planes fly well right out of the box] that I filed it in the "Given" column and forgot about it !

SkyLane, how is that B-26 flying now ?
SC
:kilroy:

[Nole]

...fly level. And yes, that is a function of the wing's angle of attack. The angle of attack being the wings angle with respect to the fuselage. For example the B-52 has a +4 degree angle of attack on the wing relative to the fuseslage...the result is that the B-52 flies level with a 4-degree nose down attitude. I believe the angle of attack on the B-26 model to be correct, and therefore the angle of the fuselage in flight is accurate. :kilroy:

I also think you may be overestimating the angle on the B-26...as it is no where near 10 degrees....4 or 5 at most. :wavey:
.

[Pen32Win]

What does the panel.cfg have in it? Does it have a Forward View Angle entry in it? If so what is it set to?

[kelticheart]

Hi Skylane,

if you wish a simpler approach to correct the B-26 flight attitude open the aircraft.cfg and change

[flight_tuning]
cruise_lift_scalar=1.0

to

[flight_tuning]
cruise_lift_scalar=2.0

That's how I corrected my Dickens', and later Tango_Romeo's, B-26 Marauder series. You may want to experiment incrementing the standard 1.0 figure by 0.1 decimals at a time. I found 2.0 to be the best for me.

Tampering with the airfile might lead to uncharted territories which,in turn, may yield bad surprises, if one doesn't know exactly what he's doing.

Cheers!
KH :ernae:

[skylane]

Hi guys!
Sorry for the long silence, I was away again with no internet..
Thans to every one of you for your ideas and suggestions! I am very reluctant to tamper with airfiles, because I don´t know enough about them.
Therefore I decided to give Kelti´s solution a try. It does exactly what I wanted! Here are two screenies of the B-26 before:

4475344754

I´m flying at 3000 ft with about 70% power. I got the estimate of about 10° nose high mentioned in an earlier post from the picture if the artificial horizon (circled in red). Now here are the screenies with Kelti´s modification:

4475544756

Same altitude, same power, and now the attitude is much more natural for cruise flight!

Thanks again!


skylane