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View Full Version : 109 sideslip and lack of rudder trim in 4.01



Chadburn
06-17-2005, 08:26 AM
It appears that the 109 has no rudder trim at all. At several speeds, even well above cruise speed, the ball will not center without right rudder input.

Oleg, what speed is the rudder trim set for in the 109's? It doesn't appear to work at any speed that I can find through trial and error, so some input would help.

Thanks

AviationArtist
06-17-2005, 08:36 AM
~S~ Chadburn,

I don't think the Bf109 had rudder trim in real life, and the pilot had to keep a contant rudder input to keep straight.

I'm sure someone will jump in and correct me if I've got this detail mixed with another aircraft type!

F19_Ob
06-17-2005, 08:51 AM
AvionArtist is right.
109 didn't have pilotadjustable rudder or ailerontrim, only elevatortrim.

It however have fixed trimtabs for both rudder and aileron and they are adjusted by the groundcrew for speeds around and over 400km (I think mainly for cruise speed) wich means that they flew pretty much straight in those speeds. (works in the sim aswell).
The torque is therefore more noticeable in slower speeds where u have to use rudder to counter it.
Many allied ww2 planes had need of lots of rudder input at slow speeds aswell.
According to mark Hanna the p51D needed similar ammount of rudder in slower speeds as the 109.

http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

Kurfurst__
06-17-2005, 08:56 AM
Originally posted by AviationArtist:
~S~ Chadburn,

I don't think the Bf109 had rudder trim in real life, and the pilot had to keep a contant rudder input to keep straight.

I'm sure someone will jump in and correct me if I've got this detail mixed with another aircraft type!


You are half-right.

The Bf 109/FW 190 had no in flight-adjustable rudder or aileron trim. It was not specified for planes under 5 tons in Germany.

However, they had fixed trim tabs which could be set like 'normal' rudder trim on the ground by the groundcrew to give neutral trim at cruise speeds, so that the pilot could fly hands off and only having to apply rudder if his speed was different from the cruise speed.

Though I think it has more to do with the throttle position, rahter than airspeed.

The trim tabs (one above and under the Fletter tab in the center of the rudder) are visible here :
http://109lair.hobbyvista.com/techref/structures/tails/770269.jpg



Now what we would need is either:

a, Oleg would set the neutral trim of the rudder to around 80% power at which the ball would be centered.
b, More preferable would be to let the player pre-select his fixed trim settings

Of course neither would be adjustable in flight, but it would be much better than the current out-of-trim expect for around the useless 30% throttle power...

Jetbuff
06-17-2005, 09:03 AM
I actually got your meaning Chadburn if you are referring to the settings for the ground-set trim tabs. Try flying at 420kph or so and 2100rpm... it flies straight then, right on the numbers too!

p1ngu666
06-17-2005, 09:13 AM
trim would probably be effected by the airspeed of air over the tab. because its in the thrust of the prop its effected by speed and power settings, and height too. but 250-300mph range it should fly reasonably straignt

Lixma
06-17-2005, 09:14 AM
Yeah....about 400 is the sweet spot. No longer sweet enough that you can go for a piss and leave the plane to it's own devices, though.

WWMaxGunz
06-17-2005, 09:18 AM
I thought it was left leg that got the main exercise but perhaps this is from travelling
below trimmed speed? There is from Galland the joke about 109 pilots walking circles
and also one or more British captured 109 test notes telling that right turns were easier
than left so jinking from 109 to the left was better.

Do I have that backward?

Zyzbot
06-17-2005, 09:32 AM
Originally posted by Jetbuff:
I actually got your meaning Chadburn if you are referring to the settings for the ground-set trim tabs. Try flying at 420kph or so and 2100rpm... it flies straight then, right on the numbers too!

Agreed. just tried it with the 109G-2. From 400-450 it was nice and straight.

Chadburn
06-17-2005, 11:22 AM
Thanks for the replies, gentlemen.

I looked up a pdf copy of Finnish G6 manual. It lists cruise speed as around 420kph, other sources say around 400kph. To achieve that, the manual recommends, 2000-2100rpm, prop pitch 9.45 to 9.50.

In G6, using autoprop at 2200 rpm, prop pitch at 9.45, I can maintain a cruise speed of 390 to 400kph IAS at sea level in Crimea map, no turbulence, no wind. But the slip ball still isn't centred. It still requires some right pedal to get it there. Jetbuff, are you fyling manual prop or auto?

(And Lixma, never mind going for a slash...I spend a few seconds scanning the sky and I'm all out of alignment...lol)

p1ngu666
06-17-2005, 11:28 AM
trim was always abit off even with p51,p47 etc with full axis trim nicely trimmed out.

still it reduces your workload, and u can go pee but u will likely be off track by a large amount when u get back

gates123
06-17-2005, 12:32 PM
Get up to altitude and work the throttle between 33-45% Somewhere in there it will trim out depending on airspeed, but its all relative to engine rpm. Yes it would be nice to adjust the rudder trim on the ground for higher rpms.

Chadburn
06-17-2005, 01:01 PM
Originally posted by gates123:
Get up to altitude and work the throttle between 33-45% Somewhere in there it will trim out depending on airspeed, but its all relative to engine rpm. Yes it would be nice to adjust the rudder trim on the ground for higher rpms. Well, maybe I'm taking Mark Hanna too literally when he says at cruise speed the "the tail is right in the middle and no rudder input is necessary."

Jetbuff
06-17-2005, 01:06 PM
Originally posted by Chadburn:
In G6, using autoprop at 2200 rpm, prop pitch at 9.45, I can maintain a cruise speed of 390 to 400kph IAS at sea level in Crimea map, no turbulence, no wind. But the slip ball still isn't centred. It still requires some right pedal to get it there. Jetbuff, are you fyling manual prop or auto?
Auto pitch and it's 2100 rpm iirc not 2200.

Neal, yes you do have it reversed. Right rudder was required below 400kph but it was not a whole lot of pressure to maintain. A lot of left rudder was needed above cruise speeds. This right yaw was so hard to correct apparently, due to the high speeds increasing the force required to add right rudder I'm guessing. Particularly in an unpowered dive, the 109 pilot had to almost stand on the left rudder to keep the plane going straight. This is where all the stuff about 109 pilots walking in circles comes from. Unfortunately, I doubt it can be modelled since you can't feel the reistance of an unresponsive rudder pedal.

WWMaxGunz
06-17-2005, 01:39 PM
That would be Hartmann then with the strong left leg, he was very big on speed in approach
and attack pass. I had a feeling that IRL tactics would be concerned with comparative
characteristics at high speed anyway instead of typical DF cluster-F circles with flaps
down and then whining about "why doesn't it do what the quotes say?".

If people want to see what Joe Ace saw then they have to fly it the way Joe Ace flew it
and not just pull everything but this and that to the maximum and call that good. IE,
they have to experiment and understand this is a sim that despite how much better than
before there's still room for things that can't be done at this time.

I wonder if RPM dependant effects have to do with modelling of propwash?