Wednesday, May 26, 2010

The History of the Immelmann Turn

One of the most popular maneuvers in the repertoire of every competent aviatrix is the Immelmann turn. But what is the Immelmann turn? It may surprise my gentle readers to learn that there are, in fact, two such maneuvers in existence. One of these was invented by Max Immelmann, the handsome Teutonic flying ace. The other was developed later, and the man's name was attached to it posthumously.

In the modern field of aviation, it is believed that the Immelmann turn is an altitude-gaining reversal. The pilot first of all pulls his aeroplane through a half-loop, and then, at the top of the loop, rolls the aeroplane until it is facing the right way up. Thus, the aeroplane continues to fly in the opposite direction, at a higher altitude than it started. The following sketch might prove useful for an understanding of the maneuver's appearance.

On first blush, it might seem that the mystery of the Immelmann turn has been solved, but if one delves deeper, one discovers that the Immelmann turn illustrated above would have been quite impossible in a Fokker Eindecker, Immelmann's aeroplane of choice during the great Fokker Scourge. Most aeroplanes of the period did not possess the ability to perform this maneuver. To demonstrate, I have performed the maneuver in a Royal Aircraft Factory SE5a, a much more advanced scout than Immelmann's Fokker Eindecker. The maneuver was captured by the new kinetograph, recently made available to the general public. It can be found here, on YouKinetoscope:

The knowledgeable observer will note that the aeroplane begins to precipitously lose airspeed at the top of the loop, resulting in a degradation of aileron authority. As speed decreases in an aeroplane, the ailerons generally become less effective, and thereby the aeroplane's ability to roll is compromised. Even in a powerful new fighting scout like the SE5a, this correspondent found the maneuver exceedingly difficult, requiring a high degree of speed on the entry, and a great deal of delicate manipulation of the rudder bar in order to prevent a stall.

The more observant of you may have noticed that, as the maneuver was completed, your humble correspondent found herself face to face with a Fokker biplane, but I assure you I dealt with the Teutonic scoundrel quite forcefully, with a liberal application of lead courtesy of Messrs. Vickers and Lewis. Proof of the feat may be found in my second series of kinetograph images, wherein the hapless Hun is seen plunging to the ground, trailing a plume of black smoke.

But back to the point of the thing, the evidence is quite clear that Herr Immelmann could by no means have performed such a maneuver in his Fokker monoplane, as it was equipped with primitive wing-warping technology, which has a tendency to be even less reliable than the modern aileron. So, what then did the Immelmann turn actually look like?

As many aviators from the war will attest, the real Immelmann turn consisted of a steep reversal, using the vertical, and the application of rudder rather than aileron control. As the Fokker Eindecker used a Morane-style rudder and elevator assembly, its response in those axes of control was quite good. This stands in stark contrast to its aileron control, which was quite poor. Consequently, it seems logical that the maneuver performed by Immelmann would have utilized the best qualities of his scout - namely the rudder and elevator controls.

The following sketch is rather in the way of being a secret. It was drawn for my by Flight-Lieutenant E.L. Ford of His Majesty's Royal Naval Air Service. As such, it is absolutely imperative that this information not be leaked to the Hun. I shall trust my readers to remember that loose lips sink ships, and also shoot down aeroplanes and do loads of other awful things. However, for the general edification of the public, my integrity as a journalist requires that I display the sketch.

To further demonstrate the technique, I performed it myself, in the same Royal Aircraft Factory SE5a. Note the airspeed indicator on the right-hand side of the cockpit control panel. One can see quite clearly that this Immelmann maneuver retains more speed than the other, and is completed much more smoothly. Both of these factors are crucially important in aerial warfare.

Now that the history of the Immelmann turn has been made clear, it is this correspondent's fondest hope that her readership will utilize this information to give Harry Hun the sound thrashing that he deserves.

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