The RTA engine’s immediate predecessor in the Sulzer low speed
programme was the loop-scavenged RL series, of which examples remain
in service and merit attention here.
The RLA56, a small bore two-stroke engine introduced in 1977,
incorporated the basic design concept of the successful RND and
RNDM series but extended the power range at the lower end. This
engine, of comparatively long stroke design, was the first model in the
RLA series. It retained many of the design features of the then most
recent economical loop-scavenged RLB type (Figures 12. 36 and 12.37),
both engines using many features of the earlier RND-M series