Where did the term 1/2 A originate?
07-25-2006, 10:08 PM
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Where did the term 1/2 A originate?
What is the history of the term 1/2 A. Sorry for the newb question but I have no clue other than small plane arox .049 size.
07-25-2006, 10:17 PM
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RE: Where did the term 1/2 A originate?
It's all about engine size. One of the others will fill us in on the different classes. Needless to say 1/2a is for engines smaller the the A class.
Later,
Tim
Later,
Tim
07-25-2006, 10:24 PM
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RE: Where did the term 1/2 A originate?
Until the late forties the smallest engines mass produced
were .09 and free flight had three classes,A,B,and C. Then
some smart alecky rule writer discovered .049 engines in
about 1952 . Thereby causing a complete rewrite.
Class 1/2 A - 0 - .05
A - .05 - .20
B - .20 - .30
C - .30- .60
Some of these older timers can fill us in on the class
C and D time lines because my memory blurrs.
Ralph
were .09 and free flight had three classes,A,B,and C. Then
some smart alecky rule writer discovered .049 engines in
about 1952 . Thereby causing a complete rewrite.
Class 1/2 A - 0 - .05
A - .05 - .20
B - .20 - .30
C - .30- .60
Some of these older timers can fill us in on the class
C and D time lines because my memory blurrs.
Ralph
07-25-2006, 10:25 PM
#4
RE: Where did the term 1/2 A originate?
It comes from the old classification system used to divide up competition events based on engine displacement.
.000 to .200 was A; .201 to .300 was B; .301 and up was C
Later when smaller and larger engines became available it was changed to:
.000 to .050 was 1/2A; .051 to .199 was A; .200 to .300 was B; and .301 to .650 was C; and above that was D
Today we have .000 to .025 is 1/4A; .026 to .50 is 1/2A and so on.
I'm editing to add that this is the reason there are so many older engines of the .19 and .29, etc. displacements. The FAI had events that limited engine size to 2.5cc, so there were lots of high performance .15s made in the past as well.
.000 to .200 was A; .201 to .300 was B; .301 and up was C
Later when smaller and larger engines became available it was changed to:
.000 to .050 was 1/2A; .051 to .199 was A; .200 to .300 was B; and .301 to .650 was C; and above that was D
Today we have .000 to .025 is 1/4A; .026 to .50 is 1/2A and so on.
I'm editing to add that this is the reason there are so many older engines of the .19 and .29, etc. displacements. The FAI had events that limited engine size to 2.5cc, so there were lots of high performance .15s made in the past as well.
07-26-2006, 08:39 AM
#5
RE: Where did the term 1/2 A originate?
There are also some other wierd sizes also that only make sense if you flew FF competition.
Some were .051, .201, .31, etc. These were produced so a FF flyer could switch engines in his plane and fly it in multiple classes.
For example someone flying an .049 could switch to a .051 and fly without having to change the trim on his ship. The sizes were so close that the power was similar.
BTW, 1/2 A and A are different between USA and Europe. Most of the other countries use one or the other. Also, 1/4A and 1/8A are not official and are used only for discussion/reference purposes.
George
Some were .051, .201, .31, etc. These were produced so a FF flyer could switch engines in his plane and fly it in multiple classes.
For example someone flying an .049 could switch to a .051 and fly without having to change the trim on his ship. The sizes were so close that the power was similar.
BTW, 1/2 A and A are different between USA and Europe. Most of the other countries use one or the other. Also, 1/4A and 1/8A are not official and are used only for discussion/reference purposes.
George
07-26-2006, 03:46 PM
#6
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RE: Where did the term 1/2 A originate?
If you thumb through the AMA rule book, you will find that the different competition events define the engine classes differently. Even so, what is said above is pretty much correct.
