BF109 Ruder trim?

[Marcel]

Last week when I was at the RAF museum in Hendon, I saw a BF109G. Looking at the tailplane I wondered, where's the ruddertrim? See the picture below.
Usually you can see those little ruders in the vertical rudder but not on this one. Did I miss it somewhere? Was it normal on a Bf109 to not have a ruder trim? If so, had they other means of directional trim?

 

[FLYBOYJ]

Was that a G-2? I've seen several photos of G-2s without rudder trim.

 

[Marcel]

yep a G-2

 

[Wurger]

It is true.The F and G ( especially early Gs) didn't have a rudder trimtabs.It depended on the kind of fin and rudder which was mounted to the fuselage.

 

[pbfoot]

heres the E4 and it has a piece of flexible metal which is the red piece

 

[Wurger]

It is a common way for Bf 109 to balance the rudder.

 

[Downwind.Maddl-Land]

Unlikely as it seems, the Bf-109 didn't have any adjustable rudder trim. As Capt Eric "Winkle" Brown records of the '109G in his series 'Viewed from the Cockpit':

"A shortcoming was the lack of any rudder trimming device. This meant that is was necessary to apply moderate right rudder during the climb and considerable left rudder during a dive. Thus, although the Bf-109G pilots tended to bunt into a steep dive as an escape manoeuvre in dogfights, they had some very heavy rudder and elevator control forces to contend with as speed built up and pull-outs at low level had to be made with considerable circumspection."​

The red trim tab on PB's photo of the '109E looks like a fixed tab that would have been set, after much trial and error and numerous test flights, by the ground crew as the best compromise over the aircraft's performance range.

 

[Marcel]

So the flexible metal is used as trim then? Could it be operated from the cockpit?

 

[Marcel]

ha clashed posts. So you think this piece of metal was only used to couter the plane's natural directional instability?

 

[Downwind.Maddl-Land]

Yep, that's about it. Use it to take out the individual airframe manufacture error and presumably set it for most comfortable cruise position......

However, following on from Wurger's comment above, I have just found a cutaway drawing of a G-14 with the bigger wooden fin and rudder that shows a 'Geared Rudder Tab' so it looks as though the issue was addressed later in the conflict

 

[pbfoot]

So the flexible metal is used as trim then? Could it be operated from the cockpit?

not a chance I'm assuming its flexible but am not going to pull on it to try. i would guess one or two flights would set it up. Maybe some one can translate the word after Nicht

 

[Marcel]

Nicht anfassen= don't touch.

 

[Wurger]

Exactly.

 

[Marcel]

Yep, that's about it. Use it to take out the individual airframe manufacture error and presumably set it for most comfortable cruise position......

However, following on from Wurger's comment above, I have just found a cutaway drawing of a G-14 with the bigger wooden fin and rudder that shows a 'Geared Rudder Tab' so it looks as though the issue was addressed later in the conflict

That's quite late, isn't it? I mean, most planes at that time had these trim surfaces. Why on earth didn't they put one on the Bf109 in the first place. I mean must have been quite a starin on the pilot with the big engines at all.

 

[Downwind.Maddl-Land]

I mean must have been quite a strain on the pilot with the big engines at all.

Check out the accident rate of 109G's and you'll see how right you are! Bit of a bu**er on landing I understand.........

 

[Wurger]

As memory serves,the rudders of Bf109s were balanced in a factories.Therefore there wasn't any possibilities to do it later.

 

[Marcel]

Check out the accident rate of 109G's and you'll see how right you are! Bit of a bu**er on landing I understand.........

I alway thought that was because of the narrow undercarriage.So additional of tis problem they had a trim problem as wel eh?

 

[FLYBOYJ]

Gentlemen - the rudder trim on take off or landing doesn't mean a whole lot - its in cruise flight or applying power in the climb where the rudder trim will relieve a lot of pressure on the legs.

During take off and landing you are "dancing" on the rudders, making little adjustments for P factor and any cross winds affecting the aircraft on roll out. With 1600+ HP you better be pretty light on your feet to keep things straight....

And Wurger, you are correct - the rudder is initially balanced at the factory. The only time its re-balanced if it is recovered in the field.

 

[pbfoot]

Check out the accident rate of 109G's and you'll see how right you are! Bit of a bu**er on landing I understand.........

don't blame the undercart it's 6" or 12cm wider then the Spits

 

[FLYBOYJ]

To add more to this discussion - rudder trim would be an advantage on approach with a steady crosswind - again more of a luxury but still taking a bit of a load off the pilot.

In the past several months I have had a chance to fly quite a bit at work doing engine break-ins. Now that I have some experience under my belt in the Super Cub, I believe I've come up with some reasoning for the alleged high accent rate on the Bf 109...

1. Too fast on the flair - trying to get the plane down fast and not being quick enough on the rudder.

2. Not bringing the stick all the way back in the flare - on a nose heavy tail dragger you've got to get that sick in your belly and keep it there.

3. Allowing the aircraft to "bounce" and inducing pilot induced oscillation - See item 2. There is a tendency in a bounce to come forward with the stick - the tail will come up and the aircraft will continue to fly.

4. Dirt or grass strips - not the smoothest surface to land on. Combining 1 - 3, a good crosswind plus a low time pilot, you have an accident waiting to happen.

5. Not adjusting the controls for winds when on the ground during taxi. In a head wind the stick needs to be back, in a tail wind it needs to be down - ailerons also have to be adjusted for quartering winds as well. I'm sure there were hundreds of nose overs all all sides because of this.

I believe these are the big hitters for this situation and for some reasons the Bf 109 had this reputation. I'm sure there were many a pilot low on fuel trying to get that plane down quick with too high an airspeed in a cross wind and rolling on a rutty grass or dirt field.