A Su-27 Academy 1/48 accuracy reassessment question

[Feisty Midget]

Howdo all,

 

Disclaimer: By asking this question I could be missing something obvious thus making a complete fool of myself. If so, please feel free to mock me, and apologies for the extreme nerdiness and seriousness (I'm usually not at all serious) 

 

My first post so a quick intro. After many years I've come back to aircraft modelling where I scratchbuild in metal (not plastic) in quarter scale. To help with construction I pick up the most accurate kits I can find and use those as a base reference but then use billions of photo's and confirmed measurements to get to the end result.

 

I've been looking at my Academy Su-27 1/48 I bought about 20(?!) years ago. I had heard about the inaccuracy issues, in particular the length where it is said that the model's length included the pitot tube, when it shouldn't have, hence it appears short, i.e. 1/50 rather than 1/48, plus other issues. Here's my question...

 

I have been trying to find the primary source for the length and width of the Su-27, especially with or without the pitot tube. The earliest, and only reference I've found to the 'length without air pressure receiver' is Andrei Fomin's early Polygon (1992) publication where he states "Длина без ПВД - 21.935(m)". All other 'main' publications I've managed to consult, mostly Russian, and including Fomin's later Airfleet book, have just given the length (21.935) although Moroz et al (2004) gives 21.835m which may be a typo'. There is no mention of 'length without pitot tube'. Width is given as 14.7m (without missiles attached) although Gordon gives the seemingly more accurate figure of 14.689m. None give a primary reference for this info'. Is there irrefutable proof that the length (21.935m) of the Su-27 excludes the pitot tube?

 

The reason I ask is I checked photographs of Su-27 (and Su-30 - same length and width) in planform. My theory was that length divided by width will give me a ratio that can be used to determine if the length given includes the pitot tube or not. The ratio of published measurements is 1:1.492 (21.935m/14.698m, assuming these measurements are correct). The photo's I found were far and few on the interweb thingy but I did manage to find a few Su-27's and Su-30's to check (please note I don't have the links as I wasn't expecting to find anything but these can be refound if required). This was done in Photoshop using the 'ruler' to measure from the outermost part of the wing (without missiles) and from the tip of the tail boom to the tip of the cone and again to the pitot tube. I only chose photo's that were as close to planform as possible, of sufficient resolution, and were apparently free of distortion. The margin of error is difficult to determine but needs to be borne in mind.

 

I found 6 images and the results were...

 

Width to Length (tail boom to nose cone tip): 1) 1.437  2) 1.449  3) 1.455  4) 1.442  5) 1.432  6) 1.472

Width to Length (tail boom to pitot tube tip): 1) 1.493  2) 1.496  3) 1.506  4) 1.487  5) 1.489  6) 1.525

 

The difference between these ratios in length is about 70cm (the length of a pitot tube?) on the real aircraft so quite significant. What is interesting is the consistency of images 1 to 5 and how close the W/L ratio is to that of W/L ratio of published measurements, 1.492. Number 6 is a little bit off either way it seems but not sure why. Obviously more images need to be checked to see if this was a pure fluke or not and ideally someone with a tape measure on the real thing. Maybe others here who have their own Su-27 images in planform can check?

 

Before taking this further (it has ramifications on the Academy kit build in ways not considered before), am I talking rubbish or is there some merit to the above? That's if that irrefutable proof isn't presented of course.

 

PS. I didn't add this to the above at first but might be worth it, so...

 

I did check the multi-authored Истребитель Су-27. 'Начало истории' and 'Рождение легенды' (which appear to be the best books on the Su-27) and there is a scaled factory drawing of a preliminary Su-27K on page 446. Careful measuring puts the aircraft at 21.5m (give or take) but obviously take this with a pinch of salt, being a copy of a factory drawing of a preliminary design which may or may not be drawn accurately to scale in the first place, hence my original reluctance to mention it (but it's the closest I've come to an original document). Unfortunately I couldn't find anything on the dimensions in these tomes unless it's buried deep in the text somewhere (me not fluent in Russian). I'm sure someone has original info' out there.

 

Cheers,

Feisty

Edited August 28, 2018 by Feisty Midget
PS added