|First flight||May 1913|
|Primary user||U.K. (RNAS)|
|Engine||100hp Gnome rotary|
The Avro 503 was an early floatplane originally known as the Type H. Before the war, one was bought by Germany and became the prototype for the Gotha W.D.1. Small numbers were built for the RNAS, and one participated in a bombing attack on Zeebrugge. At least one was configured as a wheeled trainer. 
For more information, see Wikipedia:Avro 501.
- Bruce, p.38.