Block Number
In 1941 block numbers were added to designations to show minor equipment variations between production blocks. The block number appears in the designation between the model suffix and manufacturers code (for example F-100D-85-NH). Initially they incremented in numerical order -1, -2, -3 but this was changed to -1, -5, -10, -15 in increments of five. The gaps in the block numbers could be used for post-delivery modifications, for example a F-100D-85-NH could be modified in the field to F-100D-86-NH. Not all types have used block numbers.
Read more about this topic: 1962 United States Tri-Service Aircraft Designation System
Famous quotes containing the words block and/or number:
“The chess pieces are the block alphabet which shapes thoughts; and these thoughts, although making a visual design on the chess-board, express their beauty abstractly, like a poem.... I have come to the personal conclusion that while all artists are not chess players, all chess players are artists.”
—Marcel Duchamp (1887–1968)
“Mining today is an affair of mathematics, of finance, of the latest in engineering skill. Cautious men behind polished desks in San Francisco figure out in advance the amount of metal to a cubic yard, the number of yards washed a day, the cost of each operation. They have no need of grubstakes.”
—Merle Colby, U.S. public relief program (1935-1943)