"Teacherjh" wrote in message
...

152 should have been the 150N


I wish they'd use new numbers more often rather than letters. We already
have
the 172 R, the 172 G, the 172 RG, the 172 N, and so forth, with the
letters
seemingly arbitrary (or at least overlapping in meaning)


Most airplane designate variants of the basic type by using a letter. Thus
Cessna introduced the 172, then the 172A, the B, etc. Planes that had two
letter designations, such as the RG and the XP, were special types of their
own. Thus the RG had retractable gear. It was not in production long enough
for there to be a 172RGA.

The 150 and 152 each had their own type certificate, whereas almost all the
172s have the same type certificate, the 172RG and 172XP being notable
exceptions -- they share the type certificate with the 175.

It is a lot less expensive to certify an airplane as a variant of an
existing type than it is to certify it as a whole new type. In fact,
certifying a new type has become so expensive that it has threatened to
bankrupt every manufacturer that has tried it. Cirrus managed to survive
(barely), but almost all the other manufacturers of new types have either
had at least one bankruptcy or they had to seek financing on terms that
amounted to selling and giving up control of the company at a steep
discount.