I predict incidentally that compressed air servo systems will
replace hydraulics in many aircraft. Safety, economy and ease
of service will promote that.

Just for your information, the YAK-52s being imported into this
country are pneumatically operated, the brakes, flaps, landing
gear, and even the engine starter. The starter is most unusual
in that the compressed air is injected into the top of the cylinder
heads just past TDC via an air distributor similiar to the spark
system.

Bob Moore