Cons For the M14-P Consideration?

[triumphantduke]

We all know it'd be cool, and it's fairly easy to find pros for the decision to get an M14-P engine (with updated pistons/FI/aerodynamic cowling/etc.). I found something that mentioned the Russians were operating generating sets in Siberian oil fields powered by M14Ps, which were expected to run for 20,000 hours before overhaul. Yes, that isn't under the stress of flying, but it seems noteworthy when considering the engine. If I may tap in to the knowledge base here... what are some cons of the engine for those familiar? Besides the risks of hydraulic lock when appropriate caution isn't taken. Since the model 5 could be considered "apples to apples" with the Murphy Moose. I think it would be a valid to explore this option. Since as far as I know there are essentially 3 Major contenders within aviation that have a lengthy service histories: Lycomings, Continentals, and the M14-P (the PF looks like its just adding stress).

Any sources for engine failure data for aviation piston engines would be useful. I found one for Australia...which had a good bit of info on the Lycoming and Continental but no hits for engine failures for the m14.

And if you think its a flat out dumb idea, give some details, I don't mind.

[AZBearhawk272]

Mounting an M14-P to the noisy end of a Model 5 will require substantial changes. The thrust lines will have to be altered by lowering the M14-P to get close to plans. That will result in almost being able to have a windshield in front of the pilot. Then the landing gear will have to be lengthened so the prop will have ground clearance in a level tail up attitude. Then you will have to locate the start air bottle most likely in the baggage compartment………..
It will look cool……
but then there is the fuel consumption and drag holding the Model B wing back from the sweet spot……
About 20 years ago there was a project named “Desert Hawk” What is old is new again?

Not Dumb, it can be nicely done for a round engine
vintage look. You will end up with looks only and a lot of retro engineering, Think flying “Rat Rod”

Kevin D
272
KCHD

[jaredyates]

Sometimes it is hard to value answers on a forum, but this answer is coming from what I would think of as the most qualified human available on this topic. Certainly in the top three or so.

[rodsmith]

Kevin, can you explain "drag holding the Model B wing back from the sweet spot"?

[triumphantduke]

Thank you AZBearhawk272, hmm I definitely don't want to "rat rod". It'd only be worth having doing if it was useful to.. the geometry of the thrust line impacting prop clearance and the need for lengthened landing gear would be concerning. However I've found some info that with a few updates like the electric start, you wouldn't need the air bottle? (its a question because I don't know what I don't know). And other updates that make the engine seem to have comparable fuel burns to a 540/580. Adverse effects on weight, structural strength, and geometry are definitely show stoppers for me - I was crossing my fingers since the max gross of the murphy moose is now "only" 500 lbs more than the model 5

[rodsmith]

Several years ago I seriously thought about doing that. That was way before the Model 5 and I would have been on my own designing a larger fuselage and changing the lines to accommodate the M14-P. Back then the M14-P could be acquired very reasonably. I figured I would put the savings from a cheaper engine into a 4-bladed propeller so the landing gear wouldn't need to be much taller. The engine is somewhat heavier than the IO-580 but probably could be installed with a somewhat shorter engine mount. If done right, I think it could be a great airplane.

[triumphantduke]

yes that's one of the big questions for me - if it'd work with the model 5 without a need for having a unique airframe, I don't want to be lonely in that department!

[Sir Newton]

I think it would be awesome to see someone package a M-14 on a BH5. However it will not be me accepting this challenge. I have 16.4 hrs air time behind an M-14 both the P & the PF with the taller super charger drive gears. Mounted on SR 3500 Murphy Moose. There is alot that can be said on the subject. Setting aside the operational considerations of a round engines. The 1st snag is the fuel burn. At take off power is just shy of 40 gallons per hour. Cruise power is 25-30 depending on your experience with the engine. 2nd snag is wet weight. Coupled with fuel consumption & considering BH5 is already running counter weights in single pilot operations? Imho it could get interesting to say the least. I really like the M-14 it is very reliable power plant. Crazy amount of power, looks cool as well.

[triumphantduke]

if only we could get the original army contract price of $4,000 for the allison 250 lol

[zkelley2]

I looked really hard at the Allison 250. The length of the engine mount needed was ridiculous. That engine is crazy light. On floats it probably would have been ok, but on wheels it didn't take much nose down to put the prop in the dirt.
Also the fuel burn was crazy. I would have needed to get the fuel capacity up to ~130gal to maintain the usefulness of the aircraft. At which point the actual useful load was gone.

[Sir Newton]

Yes it is. But what fun it would be to build ;-)

[AZBearhawk272]

Rod,
Drag, my choice of word was a bit sloppy, let me clear that up.
It is an aerodynamic thing.
The Model 5 airfoil is well optimized for the Model 5. It is efficient at carrying a varying load at a wide CG range within normal cruising and does not "Feel " much different at different speeds.
( I did not fly the 5 at heavy weights) All airfoils are a compromised solution for a lot of variables, which is why there are at least a bunch of airfoils out there.
There is an optimal speed and condition for which the airfoil is "Happy" at the sweet spot.
The air moving past most of the wing is moving through the air at "Aircraft Airspeed". The air starts moving out of the way of the plane before the plane gets there.
A big mass of air has go around a big old radial cowl and be accelerated by the prop and propelled aft to drag the plane through the air. This mass of air is moving faster than the plane, the wing in the area of this high velocity zone has a relative velocity to the air that is faster than the clean air design point of the airfoil......... Drag Goes way up for a big area of the wing behind a big fat radial cowl. Just a guess, I would think the dirty plume behind a blunt radial engine would be out to about the wing struts or half the wing span. So now the inboard / high velocity section is really inefficient and the outboard section has to carry more of the weight so it moves off its sweet spot......... evil cycle.

A horizontally opposed engine has a drag disturbance profile generally less than the cross section of the fuselage that it hangs on, not so of a big radial.
Jets are nicer, sailplanes eloquent. No torpedo or submarine has the prop in the front and they are not dragging a set of wings around.

I do like a big old radial. : )

Kevin D
#272

KCHD

[Brian Mason]

Wouldn't it be cool if Duke engines were perfected!? They have/had one on a Piper test bed. Round small and powerful. They still have a website, but development seems to have stalled.