Found on a fellow Cessna retiree's Facebook page.

Cancelled due to the general market downturn plus performance not up to predictions.

Is that just a 441 with PT6’s?

Essentially. Used -116's which were a version of the 135/135A. Used nacelles, which included nacelle baggage, from the 406. Standard exhaust stubs shown, we experimented with streamline stubs. Probably needed 40 series PT6's, but that would have taken a lot more redesign.
Edit: We had problems with oil cooling on the ground. In spite of a higher capacity oil cooler, caused by management direction to use NACA scoops instead of external like 425/406 (I wanted to use a P-51 style scoop on bottom of nacelle), use of high idle for ACM, and test pilot insistence of pulling power lever partly into beta. Never did resolve.

The Reims-Cessna F406 Caravan II was, and still is, quite a remarkable aircraft. Non-pressurized, based on the Titan with PT6A-112.
A multirole workhorse, with endurance and range.
https://www.aerospace-technology.com/projects/reims-406/

I worked on the F406 design also. Some interesting coordination issues with Rheims. My boss and the project engineer went to France for the first engine runs, but I never did. At one time, Rheims wanted to change all the sheet metal to metric sizes, but going to the next size smaller would require structural recertification, while going to the next size larger would have added weight. Also, a ton of paperwork. Might note that while the fuselage was 404 based, the wings were 441, built in Wichita, with modifications for different nacelles, etc.

With regard to the 406, apparently Rheims went out of business sometime about 2014.

There was some information about this time that Continental Motors bought the rights to the 406 (don't know what this included in terms of tooling, parts, etc.), but I can't tell if it fell through or anything ever happened.

Also might add that certification (French DGAC followed by FAA reciprocal including SFAR 41) was real confusing me, and I worked on it.

Was this the airframe that they tried long exhaust and fairings down the nacelle sides from the PT6 to increase speed?

Yes, they called them "beagle ears".

The 435 was a dog at high altitude. From Thompson's "Cessna Wings for the World III":

"C-435 performance was good except at high altitude. With a full load (or even with fuel burn-off) it could not reach 31,000 feet. During a night flight to Colorado Springs, Denver, Goodland, KS, and return with only three people aboard at 31,000 feet it took the skill of a test pilot to maintain that assigned altitude. Both he (Dan) and a crew chief (Larry) tried and failed to hold that altitude. Also, there was only a 5 knot spread between stall speed and maximum speed at full power."

The 441, equipped with TPE331 engines and able to operate at FL350, ran circles around the 435, which is likely why the project didn't progress.

Later King Airs did make it into the 30s for altitude, but using MUCH larger PT6 engines, the PT6-6x big block versions. The small block PT6 just isn't built for high altitude.

Mike C.

Yes. Was informally called "Beagle Ears." Collapsed and gave an engine compartment overheat warning on first and only flight. I was thankful I was not involved.

Edit: I didn't see Mike's response before I wrote mine. His photo sort of tells the story.

Another edit: The photo also shows the oil cooler NACA scoop that didn't work very well.

Thanks, It is interesting they rejected the installation due to performance loss over the Garretts but it was probably faster and went higher than the BE90 of that era.

Interesting the oil cooler scoop did not work but the T303 has almost an identical scoop for engine intake air. The T303 scoop has a small fence each side to trip the boundary layer into the scoop I believe. Compare to the scoop on the side of the 425 Nacelle

Some Frakes stacks might have made the difference.

I think we tried them at one time.

One of the problems with the oil cooling was that we were getting feedback from Flight Test that it worked fine, but when it turned warm and they did the semi-official cert test, it didn't. As mentioned, there was some difficulty and disagreement on test criteria. Our section wanted to restrict high idle in this situation, but the flight test pilot disagreed. We were going with a reduced OAT limit (110 deg F) for the time being while we figured out what to do, then the program was cancelled. The main problem with the performance prediction was that it was done by a Flight Test Engineer (who sadly subsequently passed away from cancer) who based it on 441 data and accounted for the engine performance difference, but did not properly account for increased drag due to exhaust, bigger nacelles, oil cooling, etc. I don't know why he didn't use 406 data. The problem somewhat compounds itself because reduced speed results in somewhat reduced power due to less ram recovery, which is lower on a PT6 installation to begin with.

Here is another fairly minor example of things that happen:

The 441 fuel plumbing in feed bay internal to the integral tank was sort of a kluge that included a number of fittings, including a heavy steel swivel nut tee. This carried over to the 406.

When the 435 came around, I took the opportunity to redesign the kluge using an investment cast manifold to reduce the part count and weight (probably less than a pound per side, but every little bit helps; it was hard to get straight answers on the value of a pound.)

It was to be common to the 441, 406, and 435.

Look how that worked out.

...looks more like basset hound ears to me!