Aircraft
by Nation
United States
Army/Air Force 1924-1962
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History
1926: The name of the Air Service is changed to
the U.S. Army Air Corps.
1942: The U.S. Army Air Corps is re-organized as
the U.S. Army Air Forces.
1947: A new U.S. Air Force is formed as a
separate service from the U.S. Army.
Designations
Basic Classification: In 1924, the U.S. Army Air
Service (as it was then known) introduced a new classification
system. Each aircraft that the USAAS contracted for was given a
letter type that denoted the aircraft's mission and a number denoting the
model number within that mission type. For example, the B-17 was the
17th bomber that the U.S. Army contracted for. A few mission types
used a two letter mission type--for example AT for Advanced Trainer.
Minor modifications to an aircraft type would generate a sub-type denoted
by a letter. For example, the B-17E had a larger vertical stabilizer
than the B-17D.
Problems: With each mission having its own letter
designation and model sequence, things could get a little confusing when
an aircraft designed for one mission was modified for another. The
B-17, in addition to its bombing role, was also used in photo
reconnaissance and as a "drone bomb". In these roles, this
aircraft went by the designations F-9 and BQ-7. A change in engine
also generated a new model number. An experimental B-17 with Allison
V-1710 engines was designated the B-38. Four designations for
basically the same aircraft.
The Solution-Prefixes: Initially, the use of
prefixes was fairly limited. The letter X denoted experimental,
typically the prototype--for example the XB-17. If the prototype was
successful, the Army would procure a limited number of service test
aircraft to see how the aircraft held up in the field. The letter Y
denoted a service test aircraft--for example the YB-17.
In 1947, with the creation of an independent Air Force,
the classification scheme was simplified by expanding the use of
prefixes. The original aircraft designation would remain and a
prefix would be added to denote a special mission. For example, the
B-29 was re-designed the KB-29 when it as redesigned as a tanker and the
RB-29 when used in the reconnaissance role.
