Avro 504N - European Users

Th Avro 504N was an improved version of the Avro 504K, with a new engine and some other aerodynamical changes which consisted on a new undercarriage, new wings, a new engine and the removal of the skid. Some internal improvements were also made like the inclusion a direct gravity feed for gas.

It was used by many European countries as it became their standard trainer airplane and it was license built in Belgium by SABCA during the late 1920s until mid-1930s, and in Greece by the Kratiko Ergostasio Aeroplanon (State Aircraft Factory) from 1934 until 1935.

It was powered by either a 150hp or 180hp Armstrong Siddeley Lynx IV engine.

• Belgium: It was the backbone of their trainer squadrons during the 1930s decade. Some of them were still in service when Germany invaded Belgium in May 1940.
• Denmark: The 504N was also the main trainer of the Royal Danish Air Corps during the late 1920s until the mid 1930s. It's worth to mention that these airplanes were equipped with a cowling in the back seat in order for the student to learn how to "blind pilotage".
• Greece: The Greeks ordered some 504N in 1925. 
• Sweden: In December 1925 the Swedish Army Aviation Company ordered five 504N which were delivered in April 1926. They served under the denomination of Sk-3 and Sk-3A in the Flying School at Ljungbyhed. Surprinsingly, they served only until 1928 as they couldn't cope wheel with the harsh cold Swedish weather.
• United Kingdom: The 504N replaced the 504K as the main RAF trainer during the 1920s.

Sources:

1. https://en.wikipedia.org/wiki/Avro_504

2. http://www.natureandtech.com/?cat=109

3. http://forum.valka.cz/topic/view/108754

4. http://greek-war-equipment.blogspot.com.es/2010/10/1920-1936-avro-504.html

5. http://www.avrosys.nu/aircraft/Skol/403sk3/403Sk3.htm

6. http://aviadejavu.ru/Site/Crafts/Craft33477.htm (translated)

Avro 504N - African & Asian users

On this second part of the 504N, we're covering both African and Asian users of it.

The South African Air Force employed some of them in order to replace the previous 504K versions. Unlickly, further details about the duration of their service period, and so on are unknown, so the drawing too, should be taken as speculative.

The Royal Thai Air Force, bought some 504N to equip their trainer squadrons. The served alongside the bomber Martin B-10 and the fighter Boeing P-12, so they served, most probably during the mid-to-early 1930s and were replaced by the De Havilland Tiger Moth.

Sources:
1. https://www.aviationmegastore.com/martin-b10-dh82a-tiger-moth-avro-504n---boeing-p12e-royal-thai-air-force-ssn72040-siam-scale-decals-ssn72040-aircraft-scale-modelling-decals/product/?action=prodinfo&art=84134 
2. http://forum.valka.cz/topic/view/108754
3. Salamander Books - The Complete Book of Fighters

Avro 504N - American Users

The Avro 504N was an upgraded version of the previous 504K and it was used by the next American users:

• Argentina: Apparently the Argentinean Army Air Service bought at least one of them to test it. Further details are unfortunately, unknown.
• Brazil: The Brazilian Navy's Air Service had some of them under service, most probably replacing the old 504Ks. However as we couldn't find further information, the drawing is speculative.
• Canada: The Royal Canadian Air Force had some 504N in service. Further details are unknown.
• Chile: Apparently it was also used by the Chilean Army Air Service, however any further detail is unknown, so it should be considered as speculative.

Sources:

1. http://forum.valka.cz/topic/view/108754

2. Salamander Books - The Complete Book of Fighters