Due to the failure of the supply of the type of Letov Š-328F with factory Air tried the new aircraft to sell to the czechoslovakian air force. Built even one aircraft W-328F with the only difference consisting in the construction of the new ordinal of the motor unit Avia Vr-36. Due to the installation of this motor unit, the aircraft was fitted with a new bow. This was built on the basis of the motor bulkhead located at the level of the leading edge of the lower wing. On the counter was suspended by the modified forged engine mount taken from the aeroplane W-16. Engine cowling has been on the forefront topped with a water condenser.
The first takeoff of the aircraft Š-328 was carried out 8. September 1933 and both aircraft (W-326F and W-326M) were then passed to the VTLÚ where they have been long-term tested until 1934 when they were returned back to the factory Air. On the basis of the tests carried out also defined a NUMBER of new requirements on the W-328, which had now fulfill not only the role of reconnaissance,observation and bomber aircraft but also the role of a heavy fighter. These requirements were subsequently incorporated into the type of W-328FM..
The first takeoff of the aircraft Š-328 was carried out 8. September 1933 and both aircraft (W-326F and W-326M) were then passed to the VTLÚ where they have been long-term tested until 1934 when they were returned back to the factory Air. On the basis of the tests carried out also defined a NUMBER of new requirements on the W-328, which had now fulfill not only the role of reconnaissance,observation and bomber aircraft but also the role of a heavy fighter. These requirements were subsequently incorporated into the type of W-328FM..