Hi Adrian,
Your contact has information that the Bulgarians had a Nieuport with the engine number 2936 and the gist of his query appears to be was this fitted to the Nieuport 12 8913 or the Nieuport 11 3984. The only information I can provide on this specific point is that the Nieuport 12 had a 110 hp Clerget engine whereas the Nieuport 11 had an 80 hp Le Rhone 9C (per C&C’s monograph on Nieuports in RNAS, RFC and RNAS service). I am not aware of any surviving RNAS record which would give a tie-up between engine and airframe serial numbers, although the RNAS experts out there may be able to help. Alternatively, anyone knowledgeable about French engines may be your best bet.
The information given about a Nieuport being armed with a synchronised gun by Dimitar Angelov is shown also in the book ‘Bulgarian Fighters Part 1’ by Dimitar Nedialkov (your contact is doubtless aware of this source). The same book says that with the gun fitted the aircraft was tested on 9 June 1917. This 1917 date is why I was bemused by the reference to RNAS Nieuports. However, this Nieuport could have been either the Nieuport 12 or the Nieuport 11 referred to above.
French and Bulgarian sources largely agree on the 3 French Nieuports, as follows:
Nieuports Type 24 N5346 and N5348 landed near Xanthi in December 1917. (3/12 per French; 27/12 per Bulgarian source). These had 120 hp Le Rhone engines.
Nieuport 24bis N4487 of Escadrille 503 force landed or brought down on 5 July 1918 (French) or 17 August 1918 (Bulgarian source). This should theoretically also have had a 120 hp Le Rhone but the Bulgarian book referred to above said it had a “90 h.p.” Le Rhone and that it was declared unfit for service. Certainly it was an old aircraft, having served previously with Escadrille 506 and possibly Escadrille 501 as well.
I’ll let you know in the next few days if I can come up with anything else of relevance.
Regards,
Mike.