Talk:Junkers D.I

Specs
Looks as if the values of span and length may have got swapped, as Turner & Nowarra'a book has the near identical numbers: length 23 ft 9 in, span 29 ft 6in. Has someone got Holmes' book to check entry?

The other serious discrepancy is over max speed which T&N give as 149 mph (and repeat in their text, "almost 150 mph") whereas we have 115 mph. Any thoughts? I'm expecting the Putnam Junkers book shortly, which will provide some sort of third opinion.TSRL (talk) 16:15, 4 January 2009 (UTC)


 * Grey and Thetford has a span of 9.0 m (26 ft 6⅜in) and a length of 7.25 m (23 ft 9⅜in), with a speed of 185 km/h (118.75 mph)Nigel Ish (talk) 16:26, 4 January 2009 (UTC)


 * My calculator say 9.0 m = 29 ft 6.33 in, so if we believe the metric (which is how Junkers would have measured it) rather than the Imperial, then the article just needs a span/length switch. Even the well regarded Jane's (at least the 1938 version) makes errors in conversions too often, and I tend to ask, what units would they have come in?  I've no easy answer to the speed though; however, I'd be surprised (not for the first time!) if the J 7 was faster than the J 9, the latter shorter span, cleaned up and with a bigger engine, and T&N has J 7 max at 128 mph.  Do you agree on the span / length swap for now, or do we need more info?TSRL (talk) 16:45, 4 January 2009 (UTC)


 * Yes the span/length swap seems reasonable - the same metric values of span and length (i.e. span longer) are given in Agelucci's "World Encyclopedia of Military aircraft(but with different conversions again). The trouble with speed is that there may be more than one right answer depending on height, weight, example tested etc -"149 mph" does seem very high however for a WWI fighterNigel Ish (talk) 17:21, 4 January 2009 (UTC)
 * Further to that, the "Complete Book of Fighters" gives a max speed of 140 mph (225 km/h).Span and Length remain 9.00 m and 7.25 m respectively.Nigel Ish (talk) 17:28, 4 January 2009 (UTC)


 * Right, done the swap (with a careful conversion, I hope!). Given the cleaness of the aircraft, I'd expect a high speed, even if it took a while to get there.  At the moment I can't think of a comparable design apart from the J 7 and the bigger, heavier two seat J 10, which T&N put at 118 mph (though they don't say which engine).  Do you have another source for the J 7 max speed, to see if there is any sort of agreement with T&N above?  J 9 must be significantly faster.TSRL (talk) 17:54, 4 January 2009 (UTC)


 * The Air Enthusiast article used as a reference gives a level speed during testing of 200 km/h for the J 7, with it being dived to 250 km/h. It doesn't give any speeds for the J 9/DI, but does note that it was tested at the Second fighter trial with a 160 hp high compression Mercedes D IIIaü engine and at the 3rd Fighter Trial with a 185 hp BMW IIIa engine.Nigel Ish (talk) 20:20, 4 January 2009 (UTC)


 * So this article and T&N essentially agree on the J 7 (124/128 mph): that's reassuring. My understanding is that the high compression engines were introduced to reduce the fall in power at altitude.TSRL (talk) 09:36, 5 January 2009 (UTC)


 * Not comparably clean, but the Sopwith Dolphin (Jan 1918, biplane of course, more drag you'd think) with an inline engine of 200 hp (bit more than the J 9) could do 131 mph (at some unspecified altitude).TSRL (talk) 18:20, 4 January 2009 (UTC)
 * There's also the SE 5a, which we have as 138 mph, presumably near the ground on 200 hp water-cooled. This is a bit earlier than the Dolphin of course.  Still can't think of any clean monoplane of the time for comparison.TSRL (talk) 19:54, 4 January 2009 (UTC)


 * Kay's Putnam book agrees at 140 mph with the Complete book of fighters and is close to T&Ns 144 mmp. I'm inclined to alter 115 to 140, with a ref, indeed will do that.TSRL (talk) 21:08, 8 January 2009 (UTC)