COMPARISONS are always interesting and may be extremely valuable. Elsewhere in this issue Mr. Warner has discussed European operating and maintenance practices in contrast with those on U. S. airlines, and thanks to an interesting document compiled by Mr. Kurt K. Lammertz of Ernst Heinkel Flugzeugwerke of Warnemuende, Germany, we are able to make some interesting comparisons between one of the latest foreign developments in high-speed transport practice, and our own.

ACTIVE development of twin - row radial engines by Pratt & Whitney Aircraft Company dates from the early part of 1929, when an intensive study was made of various cylinder arrangements with an eye toward increasing the horsepower of power-plant units over and above that afforded by singlerow radial engines.