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Aviation History
1942
1942 - 0034.PDF
FLIGHT JANUARY IST, 1942 Nineteenth of the Second Series FRIEND or FOE ? Twin-tailed D.H. Hertfordshire and Dornier Do 215 • • USED principally on communica tions, the De Havilland Hert fordshire is the R.A.F. version of the Flamingo and is a particularly shapely aircraft, and although its tail assembly bears a general resemblance to that of the Dornier Do 215 bomber there should rarely be any risk of these two machines being confused with each other, even from a rear underneath The former has a smoothly curving j underside from nose to tail, whereas the j latter's fuselage has a deeper forward section which houses a rearward-firing j gun position. The wings of the British ; aircraft, also, are nicely tapered, while j those of the Dornier have a more i stumpy, blunt appearance. Both, of j course, are of the shoulder-wing type. The similarity between their respec- \ tive tail units lies in the general layout. I Both have quite normal aspect-ratio j cantilever tailplanes which taper to wards the tips; both have twin fins and j rudders outrigged on the tailplane tips ; j both have pointed fuselage tails termin- ; ating approximately level with the trail ing -edge of the elevators, and both have j the outer tips of the elevators cut away i , on a straight edge to permit the requisite j degree of rudder movement. In fact, about the only really obvious • structural difference is that the tail wheel of the Hertfordshire is non-retractable whereas that of the Dornier retracts completely when in flight. This high degree of similarity in the main characteristics of the two tail designs gives all the greater importance, from the spotter's point of view, to such differences as do exist in various details. The first to strike the eye, on looking at the accompany ing drawings, will be the actual shapes of the respective fins and rudders; those of the Hertfordshire, if will be noticed, are approximately egg-shaped, but with more radius towards the lower portion of the leading-edge than on the trailing-edge. The small, rounded tip may be said to represent the narrower end of the egg. HERTFORDSHIRE DO 215 HERTFORDSHIRE : Egg- shaped outrigged twin fins and rudders. Tailplane tapers on leading-edge only. Non-retractable tail wheel. Now look at the Dormer's fin and rudder. This also tapers inwards to wards the top, mainly on its leading- edge, but both edges are straight instead of curved ; the apex and base-line, how ever, are wide-radius curves, and there is a small '' step '' near the top of the leading-edge formed by the abbreviated horn-balance of the rudder. There is far less difference between the horizontal surfaces tnan between the fins and rudders of these two aircraft. The Hertfordshire tailplane is of some what greater aspect-ratio than that of the German machine, but this alone would not be a very quick or reliable means of identification. What can be far more readily spotted, however, is the fact that the trailing- edge of the elevators on the Hertford shire forms a straight line (broken only at the centre where the extremity of the fuselage projects very slightly) whereas that of the Do 2T5 tapers from the centre to the tips. True, the degree of taper is not very pronounced, but it will be a helpful indication when considered in conjunction with the other features already mentioned. Both tailplanes have about the same degree of back- sweep to their straight leading-edges. Next week: Miles Master II and Fiat G.50. Do 215. Straight-edged taper to fins and rudders. Tailplane tapers on both edges. Fully retracting tail wheel.
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