Different engines possible?

[Morne]

Just wondering if anyone has a 337 with a different engine (horsepower-wise) front and back?

Unlike a conventional twin, where such a thing would always generate yaw when you maxed the throttles at take-off, the 337 has no such problems.

I suppose I'm thinking long term, here. When one engine gets totally run out, you could replace it with something that has more oomph. Heck, maybe even a 3-blade on one end while the other fan only turns a 2-blade!

If you wanted to get really froggy, and didn't mind tinkering with the fuel system, you could even have one running on diesel (once the DeltaHawk thing gets STC'ed) and one on AvGas! Just make sure the line guy doesn't screw THAT fuelling up.

So...anyone got a 337 with different horsey engines? How well does it work?

[hharney]

http://www.337skymaster.com/messages...ght=Skymonster
Pair of 550

http://www.aviationclassifieds.com/a...337A+Skymaster
550 on one end
360 on the other
3 blade
2 blade
One of a kind

[Roger]

That's a great idea ! I am going to put bigger tires on the rear of my 4 wheel drive SUV and see if I can go faster (or cheaper

[Morne]

Originally Posted by hharney

http://www.aviationclassifieds.com/a...337A+Skymaster
550 on one end
360 on the other
3 blade
2 blade
One of a kind

THAT is what I am talking about!

Kind of a "best of both worlds" there. All the oomph you'd ever want, plus the ability to fly fairly economically at altitude.

Heck, even the paint job on that thing is cute!

[Roger]

I've always had a bit of a problem with various "rocket scientists" scabbing "better ideas" onto Skymasters. Inevitably the scabbed on projects either fail to live up to the hype, or end up literally crashing and burning into yet another pile of metal. Then organizations like the FAA look at the model accident history, and lump the scabbed together "Spendiculous Skymasters" which have crashed or bent, into the data set with regular Skymasters. We "regular Skymaster" drivers are then left holding the bag with potential decreased value of our aircraft and increased inspection expense, due to errant cause and effect accident determinations, and subsequent buyer misconceptions.

I'm all for people trying new and exciting things to make a "better wheel" but the FAA should change the designation of all aircraft that have been modified to something like :LIYOH (Life In Your Own Hands) and then drop all of those aircraft accidents from the regular aircraft database.

Put a turbine on a Cub, but don't call it a Cub in the accident database when the wings fly off.

[Ernie Martin]

For a different reason, I couldn't agree more with Roger.

I have an MS in engineering from Caltech, spent 30 years in the aerospace industry and have consulted for both GE and the FAA. And one thing missing from any discussion in this Message Board -- not just this thread but the whole Message Board -- is "Systems Engineering". The aircraft as a whole is a "system". Everything is interelated. It was designed as a system. Change one item and it affects everything else. Often adversely. Change the engine and it affects the loads on the airframe, on the prop, on the prop governor -- maybe even the harness.

None of us has the money or resources to make sure that a change in one area will not adversely affect another area. So it doesn't get checked. Or it gets checked poorly.

I read this thread when it started and I wanted to jump in and say "are you crazy?" I didn't because I'm one of the site administrators and did not want to discourage full discourse. But now that Roger voiced his views I wanted to say "save not only the money but also the grief".

Before I went into engineering I spent five years in a business that souped up cars for racing. The typical client had limited resources. So he changed the carb from a 2-barrel to a 4-barrel. Never was the desired performance achieved. The compression ratio, cam timing, valve size and exhaust system -- which were designed for the 2-barrel -- remained, so there was now lots of fuel but the combustion efficiency sucked. Even clients who modified the whole engine ended up unhappy. Yes, the engine was a rocket but the drivetrain (transmission, rear axle, etc.) was designed for the wimpy engine, so elements of it kept failing.

Your safest aircraft is a well maintained certified aircraft. Limit your changes to the avionics suite.

Ernie

[Morne]

Originally Posted by Ernie Martin

Your safest aircraft is a well maintained certified aircraft.

Ernie, I appreciate your point of view, but hasn't the 550 been STC'ed for the Skymaster? Thus, isn't a Skymaster with a 550, be it one or both engines, still certified?

As to other ideas, like diesel, again I'm talking about once it has been STC'ed. I have no desire to be a test pilot. The diesel thing, addressed more thoroughly in its own thread, is a longterm option for dealing with the 100LL problem.

I don't have a MS in Mechanical, but I am a degreed engineer. I worked as a Metallurgist for a fortune 500 aerospace OEM for most of my career. Seeing the differences between the various revisions of "same model" commercial and military aircraft makes your point for you - just because the F-18C/D and F-18E/F look alike DOES NOT mean they are the same from an engineering standpoint! Ditto all the various tweaks of the 747, you can't pull a landing gear from a -100 and use it on a -400.

So I fully understand and respect your point about playing around with a time proven airframe. Further, I have great respect for the "nostalgia factor" associated with a "complete correct" specimen of an older vehicle, be it a classic car or a classic plane. But what I remain uncertain of is whether or not you are attacking the entire STC process in general?

Certainly there are STC modifications that are better than others. For instance, I never liked the "tip tanks" and wouldn't buy a Skymaster with them. But there are also a WHOLE BUNCH of STCs that are just fine.

Just curious where you're drawing the line, here.

[tropical]

Originally Posted by hharney

http://www.aviationclassifieds.com/a...337A+Skymaster
550 on one end
360 on the other
3 blade
2 blade
One of a kind

That's an Owen Bell airplane. I wouldn't touch it.

[Ernie Martin]

Morne, I draw the line on changes that I or a competent A&P/IA can easily determine to not adversely affect other elements of the aircraft, either because of its simplicity or because numerous such changes have already been effected without problems.

A different engine with significantly greater horsepower or one with radically different characteristics (read: diesel powered and water cooled) would be acceptable to me only if there have been dozens of such installations spanning several years and they have been without trouble.

Two other thoughts.

First, it's possible that I'm more conservative than most, because a) I fly mostly my family and principally over water, and b) I spent 19 years on communications satellites, where the designs had to be perfect since you can't fix a satellite once in orbit.

Second, my opinion is based not just on good engineering principles, but on hands-on observations. For instance, I recently assisted in the replacement of the rubber/metal motor mounts of the rear engine, a process that showed how cramped and well designed are all of the elements associated with the engine. The engineering effort that went into the design of all mounts, control cables, hoses, etc., must have cost millions in 1960s dollars, and I just cannot believed that kind of robust design can come from an STC. Just think of the consequences if a throttle control cable fails on take-off or landing, because the STC design gave short thrift to that element. And you, being an early user, are the guinea pig.

Not for me. I'm not a test pilot.

Ernie Martin