Flight Test DataDiscuss Elevator trim during Combat in the Technical forums; Originally Posted by timshatz
That is for standard aircraft, for the fighters of WW2, some had full sets of trim ...
That is for standard aircraft, for the fighters of WW2, some had full sets of trim for all flight surfaces (aileron, elevator and rudder) some had only one or two. The 109 was famous for not having rudder trim (until later marks) and pilots just got used to flying with their left (I think it was left) foot on the rudder all the time to keep it straight. Whereas the P51 had a full set that were on little wheels on the underside of the throttle (my understanding of it) that you were constantly manupulating as you manuvered and changed throttle settings.
A few notes:
1, Full set of trim wasn`t quite a standard, for example the Spit (presumably other RAF s-e fighters as well) didn`t have aileron trim. It depended on the design practice of the country of origin, and the operational role of the aircraft (long or short ranged interceptor). Full set of trim was largely useful for long transition flights.
2, Somewhat related to the above, it wasn`t only the 109 that didn`t have rudder trim - the 190 did not have one either, nor did they have aileron trim. The reason for this was the desing practice in Germany - planes under 5 tons TO weight were not required to have rudder trim.
3, Neither the 109 or 190 had received rudder trim (late 109s had Flettner tabs on the rudder to decrease control forces), though some bad-wheater fighters had PKS autopilot fitted which controlled the rudder angle. Both had variable incidence tail units, where the whole tailplane moved, rather than just trim tabs on the control surfaces. On the 109 it was operated by a double handwheel - one controlling the Flosse or variable incidence tail unit, and the other wheel operating the flaps, the idea being you could lower the flaps AND compensate for it with trim at the same time. The 190 had electric flaps and similiar tail unit.
4, OTOH, both the 109 and 190 had FIXED trim tabs on the ailerons and rudder, which could be set on the ground to give neutral trim for specific flight regimes, ie. could be set to be neutral during typical cruise speeds. The 109 (perhaps the 190, too?) also had a profiled vertical tailplane (like a wing), which helped to counteract torque forces.
The variable incidence horizontal stabilizer of the Bf-109 is also the reason behind Bf-109's ability to pull out of high speed dives sooner than P-51's & P-47's.
The variable incidence horizontal stabilizer of the Bf-109 is also the reason behind Bf-109's ability to pull out of high speed dives sooner than P-51's & P-47's.
Just finished reading through Nowarra's book and didn't see reference to variable incidence horizontal stabilizer and all the close ups of the K tails I saw had a sheet metal fairing at the horizontal/vertical stabilizer junction.
All have movable elevators which would make them mighty big trim tabs.
None had the slab tail (except maybe for experimental testing), they had normal elevators, but (like the Me 262) they featured a variable incidence tailplane which was used for trim instead of tabs. (and iirc the metal fairing at the stabilizer junction was the the location of the trimming axis)
And using that would facilitate recovery from high compressibility dives, but obviously not with the same response as slab elevators.
Last edited by kool kitty89; 05-22-2008 at 05:00 PM.
The '109 had a variable incidence tailplane that could be adjusted in flight. You can see it in cutaway drawings, and Eric Brown mentions it in his books:
"The flaps were raised manually by means of the outer of two concentrically mounted wheels to the pilot's left; the inner wheel adjusted tailplane incidence"
I don't have anything as to the degree of movement.
On the Emil it was +3 degrees to -8 degrees, I am not sure of the F-K models, looking at a drawing of the K`s control movements its not entirely clear to me what it means, but it seems to repeat the same values as the G-2 Handbuch, ie. +2 to - 6 degrees. Presumably the F series Flossenstellung limits were similiar.
On the Emil it was +3 degrees to -8 degrees, I am not sure of the F-K models, looking at a drawing of the K`s control movements its not entirely clear to me what it means, but it seems to repeat the same values as the G-2 Handbuch, ie. +2 to - 6 degrees. Presumably the F series Flossenstellung limits were similiar.
Norwarra did mention the change to the F tail design because of structural failures due to resonance but didn't mention installation of a 'slab tail'.
Interesting - how did they do it with the E and the strut? and why would they leave a movable, hinged elevator of that size instead of simply put trim tabs back there?
That would imply huge potential changes to pitch forces, which in a high speed dive would be 'interesting' structurally.
In many cases from one mod to another the elevator incidence was (permanently) changed for a gross weight change or to solve a high speed pitch problem - the 51 made several changes like that going from B to D to H.. but little changes
Kurfurst - what design problem were they trying to solve?
It does Pb - thx for clearing it up for me - the screw thread definitely indicates adjustment.. wonder how is it boosted from cockpit to take into account flight loads - and lock when you don't want it to move under vibration?
Second question - is that the leading edge of the horizontal stabilizer shown in photo. It looks too far aft of the front of the vertical stabilzer leading edge (if that is what it is?) but probably OK.
Is the hole above the leading edge and attach point for a small fairing to cover the top vert stabilizer/horizontal interface? I keep seein what looks like a contoured "L" shaped piece of metal there.
Bill, yes thats the LE of the tail, I have a book with a good drawing right here and the conection point is quite clear in that shape, it just looks weird becouse of the close-up shot.
You can see it if yo look really closely at this one:
And they seemed to have changed it a bit on the later models, at least externaly, apearing much like the Me 262's tailplane at the intercetion with the fin. (with kind of a bordering edge around the tailplane root)
it can somewhat be seen here:
Last edited by kool kitty89; 05-22-2008 at 10:51 PM.
In our tech section we have an "E" parts breakdown - I bet there is a simple bolt at where the strut attaches to the horizontal stabilizer that allows movement.
...in memory of my friend Joe Owsianik, a former right waist gunner from B-17G, 42-97159 from 2ndBG 20th Sqdn, who was forced to bail out on Aug. 29th, 1944 over my country. Joe passed away on Novemer 1, 2010.
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Originally Posted by timshatz
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