Warbird Information Exchange

I'm doing a magazine article on the full restoration of the number-one Cessna 172, which won the Vintage Contemporary category as Oshkosh last summer.

Which got me wondering: How did Cessna come up with the designations 120, 140, 170, 172 and others of the 100-series single-engine aircraft? (No need to get into the 200s, 300s, 400s...) The only semi-logical explanation I've ever heard is that 172 is the square footage of the wing area, but in fact the wing area is 174 square feet, and they never called the Skyhawk a 174.

Did Cessna just pull these numbers out of...thin air? When car manufacturers come up with numeric and alphanumeric designators, there is always some relationship to displacement, number of cylinders or doors, or something of the sort, but I can't imagine what Cessna's rationale was. Certainly they're not engineering-model designators, like what Porsche uses.

Any ideas?

After perusing the Cessna 100 series models on Aerofiles, I find the only model block missing is 130. They did jump around a bit, 190 to 170 and the infamous 162 LSA most recently. I would go with the thin air theory.
http://www.aerofiles.com/_cessna.html

Including renaming the 175 as the P172D "Powermatic" to try to get out from the 175's (undeserved) reputation

Always wondered that myself. Maybe try asking on the 120/140 forum:

https://www.cessna120-140.org/forum/index.php