C421 Excalibur Project

[VIP B737 Pilot]

Does anyone know what happened to the C421 Excalibur project headed by Jack Pelton?

 

[Ted]

I think it got shelved. The idea ultimately has no market. It's trying to take a 421 and turn it into a 425, but it will never be as good of a 425 as the original factory 425 was. The only successful piston to turbine conversions I've seen are the P210 Silver Eagle and the Malibu JetProp. Those were successful for a few reasons. The piston performance was abysmal, the piston reliability wasn't much better, and there was a single engine so the cost was much lower to convert. Also, there wasn't anything in the way of a turbine single that compared to the end result of those conversions.

The Cessna 340 Silver Eagle conversion was a good idea, but not economically viable. $1M (roughly) for the conversion cost on top of a few hundred grand for a good airframe, and at the end of the day you still have a plane with a 4.2 psi cabin differential that has an optimal altitude in the mid 20s.

 

[N747JB]

For the money you can get a much better 425 that is designed (sort of) as a turbine, with the fuel capacity and useful load etc. That's why I didn't see the value in the Duke turbine conversion, small cabin, short range and same price as a 441 with dash 10's that will fly 1800 miles at 300 knots!

 

[midwestpa24]

For the money you can get a much better 425 that is designed (sort of) as a turbine, with the fuel capacity and useful load etc. That's why I didn't see the value in the Duke turbine conversion, small cabin, short range and same price as a 441 with dash 10's that will fly 1800 miles at 300 knots!

The turbines made the Duke a real airplane, but yeah for the cost you could find a decent 90 King Air.

 

[Zeldman]

The turbines made the Duke a real airplane, but yeah for the cost you could find a decent 90 King Air.

No such thing as a decent King Air 90....

 

[Ted]

The turbines made the Duke a real airplane, but yeah for the cost you could find a decent 90 King Air.

One of the big problems with the Duke in my opinion was that it had Baron landing gear. This is why it was so short. Even with the turbines you have much smaller props than would be ideal for this reason, and it was part of what killed the engine performance.

Engine ratings are a funny thing. We look at the number that the engine is rated at, but sometimes that's a +3/-2% rating, sometimes it's a +5/0%. And within those, the designs tend to fall in one direction or another, so some engines will consistently be at [rating]+5%, some will consistently be at [rating]-1%. Duke engines were typically on the lower side, and then you have some other engines that tended to be on the higher side. Add in some of the various drag aspects... the Duke engines had a lot of drag with the top mount induction and just a very tall design. Look at the cowlings on a Duke vs. other piston aircraft, you see that a large percentage of the propeller arc is consumed by engine nacelle.

If the Duke had taller gear and Chieftain engines on it (which tended to be on the higher side of their rating) with better props and nacelles... it might not have been such a pig.

 

[ARFlyer]

The turbines made the Duke a real airplane, but yeah for the cost you could find a decent 90 King Air.

Every Duke I've ever run across has had engine issues or bad corrosion from the magnesium alloy skin. My airfield has a shade hanger queen that's a Duke. I don't even think its airworthy due to the corrosion.

 

[Ted]

Every Duke I've ever run across has had engine issues or bad corrosion from the magnesium alloy skin. My airfield has a shade hanger queen that's a Duke. I don't even think its airworthy due to the corrosion.

It's scary to find a Duke outside of its natural environment (the maintenance shop).