Time to bring back this engine?
 

With the current fuel costs rising and set to continue, what was the outcome of the test engine that McDonnell Douglas mounted on their MD-81?

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Did help fuel consuption? Is it likely that it might come back, or are todays engines more economical?

The propfan (or UDF - Unducted Fan) used about half the fuel of a CFM-56 which it was targetted to compete/replace. It would have less of an advantage over newer engines, and the big problem is the noise of a UDF. Not stage III (I believe) and certainly not stage IV, and one more thing - there is no rear-engined airframe in production today on which you could hang them. (I think the 717 is finished ?)

I was remembering something about vibration transmitted to the airframe, but my recollection is pretty fuzzy.

If they needed to find a way to mount these engines on the wings, they would do it. With fuel prices where they are, I would look for a return to the turboprop-type powerplant. This would be a good choice for the 500-mile and under stage length. This would cover a great deal of the airline business.

I wonder how the Dornier turboprop and 328 jet models compare. Anyone out there have any experience with these aircraft and would it be a good comparison of prop vs jet fuel specifics on like airframes?

Best,

Westhawk

vibration
 

Big vibration problem. Also on these types there is a loss of energy imparted to the rotating slipstream, curable to some degree by contra rotation which complicates hub and gearbox adding further to weight. All turboprops and turbofans have an issue that the vector sum of aircraft speed and tip speed will be near sonic or else low rotational velocities and large areas have to be resorted to. What a drag. Added to which Richard Shevell has passed on and William G Practice (Mr propeller part-time consultant "whizzkid") is 87. And even Bill is not a Fan of Fans.

Another impediment to the UDF concept which I don't think ever got addressed properly - but would be a major certification hurdle for any aircraft mounting one - is whether one considers the 'propfan' to be a 'fan' or a 'prop'.

If the former, how on earth you're going to meet blade containment rules is beyond me. Yet with many more blades than a prop, it's hard to see how you'd claim that the risk of blade detachment and impact with the fuselage or critical systems was low enough.

Underwing would just make this worse.