Some little addition to the uneven opening of the L.E. slats. I tend to believe that the RAE`s report is referring to the uneven opening of
one slat, and not to the assymetric opening of both on the two wings depending on AoA etc., which should be nothing of news value, being quite natural. And perhaps due to my lack of understanding in aerodynamics, I don`t see why would this lead to aileron snatching...
Thus I believe itthe phenomenon they talking about was actually the uneven opening of one slat in turn, if the pilot was not keeping the ball centered, for example the slat`s inner portition came out first in a turn, and the outer one only later, which of course meant that the lift was chaning unevenly over the wing area AND the ailerons, resulting the ailerons being twisting/snatching slightly under different pressures.
As Dave Southwood described on Bf 109G :
One interesting feature is the leading edge slats. When these deploy at low speeds or in a turn, a 'clunk' can be heard and felt, but there is no disturbance to the aircraft about any axis. I understand that the Bf109E rolled violently as the slats deployed, and I am curious to know the difference to the Gustav that caused this.
I don`t think the Frise ailerons on 109 G (and F, K) would be the major reason for the improvement. Then it would be an improvement, while it is clear that the phenomenon found on the 109E just disappeared. I think the reason for that lays within the fact that the slat`s mechanism was changed on late Fs and all Gs, being operated by 2 rollers/slat (late F/G/K) instead of 2 swing arms/slat as on previous models. If I got it right the latter would allow by their nature the slat open unevenly along the leading edge, while rollers would make it even all the way, as there`s no "play" between the operating of the two, they move in perfect syncron forward and aft, opening and closing the slats neatly. As a result, the slats will always make their appearance felt over the wing or the ailerons on the trailing edge right in their aerodynamic shadow at the same time, hence no disturbance in any flying axis.
BTW, what type of slat operation the Lavochkin series had ? Swingarm or rollers?
As for the British pilot`s skill with the 109s, I find that very doubtful. Perhaps a very few of them were familiar with it, and managed to push it to the edge in turning, but the overwhelming majority of them give the impression they fly a plane with leading edge slats for the first time in their life, hence the almost childish curiosity display towards the operating of the slats. It was just all new, unfamiliar to them. Besides, how much time they did have on those rare flyable models ? Eric Brwon, probably the most skilled pilot of all of them, and certainly the most often qouted, logged in about
a single hour into the Bf 109G-6/U2/R-6 he flew. That`s about
1/30 of the time a German rookie spent in the type as late as 1944...... it speaks for itself, even if we take Brown`s great general flying experience, he hardly had more than a single sightseeing run with the type instead of a proper training under the hands of a skilled instructor. Certainly such an unfamiliarity on the part of British test pilots with the plane`s major asset for horizontal manouveribilty contributed to such surrealistic result such as :
Turning Circle
The Tempest is slightly better, the Bf.109G being embarrassed by its slots opening near the stall.
Well at least they made the reason clear: the pilot`s were being embrasssed by opening of the leading edge slats, which happened a good 20-30 km/h above the stall speed itself. Of course trying to turn about 25 km/h over stall speed, with the maximum lift coefficient of the wings isn`t even realising would hardly improve the turning circle. I remember reading Tobak`s book, a 109s pilot who`s clealry remembered his instructor`s most common advice during the training with Bf 109s:
Ziehen, noch ziehen!. Or pull it, pull it more. In other words, the 109 was a plane that like being pulled hardly on the stick in turns, the slats allowed for high angles of attack at which un-slatted types would stall due to loss of airflow.
