As engine fires occurred with the B-36 's radial engines , some crews humorously changed the aircraft 's slogan from " six turning , four burning " into " two turning , two burning , two smoking , two choking , and two more unaccounted for . " This problem was exacerbated by the propellers ' pusher configuration , which increased carburetor icing . The design of the R-4360 engine tacitly assumed that it would be mounted in the conventional tractor configuration — propeller/air intake/28 cylinders/carburetor — with air flowing in that order . In this configuration , the carburetor is bathed in warmed air flowing past the engine , so is unlikely to ice up . However , the R-4360 engines in the B-36 were mounted backwards , in the pusher configuration — air intake/carburetor/28 cylinders/propeller . The carburetor was now in front of the engine , so could not benefit from engine heat , and also made more traditional short-term carburetor heat systems unsuitable . Hence , when intake air was cold and humid , ice gradually obstructed the carburetor air intake , which in turn gradually increased the richness of the air/fuel mixture until the unburned fuel in the exhaust caught fire . Three engine fires of this nature led to the first loss of an American nuclear weapon when a B-36 crashed in February 1950
crashed
1950 British Columbia B-36 crash
Convair B-36 Peacemaker