Below are comment from Tom Thayer, a fellow volunteer at the Wings Over the Rockies Museum, former owner/pilot '40 Cub J3, degreed aero engineer and is familiar with the airport and near hills.
- Dave Mc
That first item, Daly City, is interesting. As one guy said, the prop is an important clue. The theory that the prop was a pusher is one possibility. The other possibility is that it is a tractor (i.e., a puller) used on a European-built engine. This is possible since European standard for a long time (and maybe still) was for clock-wise rotation as viewed from in front of the plane. (But nosing in and not breaking a prop is unlikely, as they point out.) The Franklin engine suggested by the article is early US product and therefore has a counter-clockwise rotation as viewed from in front of the plane.
I'd have to see the prop first hand to render an opinion on whether it is a pusher or tractor prop. The hub of the prop would tell us which side of the prop was bolted to the crank shaft. From there we could match the prop airfoil cross-section to push or pull, and thence to which way the engine turned. No doubt, from the size of the prop, it is a small engine, possibly a Franklin which was used widely.
I agree that the size and lack of metal leading edges on the prop make it a civilian item. Franklin did make a line of small engines. Various models in their Series 2 engines produced from 45 to 60 hp. The fact that three people were in the crash leads me to wonder about just how small the engine was. Our J-3 Cub had a Continental A-65 which put out 65 hp, and it couldn't have gotten more than two people off the ground with anything left for decent performance. Incidentally, we flew our Cub out of Palo Alto, a field just a ways down the peninsula from Daly City.
As an aside and purely "what if" thinking , there is no mention of what the crash site was like. The assumption that the crash was on a hillside led the analysis to a nose-in crash, doing damage to a prop on a tractor configuration. Suppose the pilot managed an angle that somehow saved the prop? I found a plane that used a Franklin Series 4 engine, a Stinson Model 10A, that conveniently had three seats. It was a 1939 design. Wikipedia says it had a Franklin 4AC-99 engine putting out 90 hp. ( https://en.wikipedia.org/wiki/Stinson_Voyager#Specifications_.28105.29 )
Another question: is it known that the engine was a Franklin?
If those guys keep asking questions and can gain access to the prop, they should be able to noodle it out. The guy who wants wing rib measurements is also onto something. With those measurements the cross-section of the airfoil can be determined, its shape is similar to a Clark Y, a common airfoil of early planes. Size and placement of the rib trusses can be instructive to those who build or repair old planes. The size and placement of the spar or spars can tell them things, too. Wikipedia says the Stinson Model 10A was also powered by a Continental A-75-3. They list the airfoil as NACA 4412, incidentally. That could be useful in verifying the wing rib as a Stinson or not.
These are all guesses on my part, some admittedly in the weeds , but I think they are reasonable guesses.