What can be done?

[ghancock]

So I really love my Commander but I really hate the engines on it.  I’m not sure what if anything can be done about it but the airplane is such an awesome plane if I didn’t constantly have engine crap to deal with.  So my question:

Is there anyway to put different engines on the plane that don’t run so hard that might allow the cylinders to last longer than 300 hours?  I’ve combed through my logbooks on the plane and it appears even from the early days people have been replacing cylinders starting around 300 hours after engine rebuilds.  I’ve personally had 4 failures, 1 resulting in having to shut down during a flight and another 2 preventing me from coming home.  Add to it the skydrol 3000psi pumps and Simmons fuel injectors and wow...

The problem for me is the Commander is by far the best flying airplane I’ve ever flown and honestly at the moment I have 12 new jugs on the engines so I can get at least 300 hours or so before I have more trouble but I want something more reliable.

Is there anyway the airplane can be converted to experimental so that I could put whatever engine I want on it or is the airplane just doomed to the dust bin? 

I watch the Draco guy doing all sorts of stuff to his production airplane and I’m not sure how he gets away with it.  I guess I should ask him but was wondering if any of you had any thoughts on the matter?

Thanks,

Glenn

[ghancock]

Anyone know if it is possible to still put 720’s on it?

[AC680fan]

Glen,

I have no details, but before Morris passed he’d mentioned the possibility of using a 541 that’s on the Duke and creating a Stc for the 680 series. He believed the weight savings alone would be worth it not to mention converting the hydraulic to 1000psi and replacing the pressurization with turbos. He started to have problems with his shop and health before we could go any further. But if Morris thought it was feasible and practical it might be worth investigating. Good luck, long time follower of your videos and your 680.

[donv]

Wasn't there a Mr. RPM conversion to 720s or something like that? I'm pretty sure there was one for the 680FLP, but maybe not the FP?

If you want to be practical, I would sell the 680 and buy a 500B. That would be a nice complement to your 18, and would still fly very nice.

Let someone who wants to own and operate a museum piece have the 680.

I would think Bruce could help you out, and maybe even take a trade.

[Roy]

There was a Mr. RPM conversion on a 680F that Morris had in his shop that met with demise; I think it was something like hydraulic failure while taxiing and it hit a fence or something. So I'm quite positive there is an STC for the 680F. As for the 680 FP, I'm not sure.

Try tracking down Barry Collman? He pretty much tracked every AC there was, not just pictures.

I'm with Don; a nice 500B (with RayJays) is a nice plane, and the RayJays didn't seem to need near the attention as the geared motors you have. Even a nice straight aspirated -B model is nice as well.

[ghancock]

Yeah, I know there is an STC for the 720's but no one is making any of that stuff anymore.  So it would probably be a pretty big job to do the conversion.  The 541 option is really just a slightly larger 540 as far as I know and to get over 380hp you'd end up having to go to the geared side which is really no different than where I already stand.  I'm not sure of the price on these engines but they also don't run upside down so would need to redo quite a few things to have the exhaust coming out the bottom instead of the top.

As for selling the plane I'd love to get it into someone's hands that will fly it.  The problem is, no one really wants to step into this type of a project.  I mean, to be clear, with new engines I'd probably be having none of these issues, at least for a while, but the market for a pressurized Twin Commander with piston engines probably isn't very large.

As for trading, that might be an option but not sure Bruce would want to get involved in trying to move this type of plane.

I hope to have her back in a hanger in the next couple of months where I can start working on getting annual done as well as the gearbox on the left engine.

Just don't want to see her die. :-(

Glenn

[Roy]

The TIO-541's on Dukes do produce 380HP, but it takes 2900 RPM to do so. Never liked the thought of spinning them up that fast in the ~15-20 hours of Duke time I had, but it was obviously by design.

Roy

[donv]

Could you buy an airplane like the one Roy mentioned (damaged) and take the conversion bits and engines from that?

You'd still need the STC, but I assume that's available in some shape or form?

[Adam Frisch]

Duke engine will cost as much as the ones on now. They were only used on the Duke and there isn't a good infrastructure behind it. It also has cam problems. I would try to make the ones you got on now reliable.

[Big Pistons Forever]

The Duke engine does not have a pretty history. Talk to any shop that has maintained a Duke and you will get the same story. great airframe, terrible engines.

I would talk to a DER and ask what he would need if you found a Mr RPM Commander  (any model) that has big airframe issues so it will be cheap to use as a engine donor. There is no replacement for displacement. I flew with a guy who had a 400 horse Comanche and I was pretty impressed. Butter smooth and this one was sitting at 1600 hours and had all original cylinders.

[ghancock]

Yeah that is what I would like is the 720's.  And btw:  2900rpm?  Is that all?  I'm turning 3400rpm on take off.  I feel like I'm sitting on a monster about to go wild every time I push those throttles forward.  I must have missed the damaged commander with the Mr RPM conversion.  Will have to go back and look for it.

[ghancock]

Oh, you're talking about the one in Morris's shop.  Someone told me that most things in his shop are property of the airport now due to being behind on the bills but not sure how factual that is.  Also not sure if Morris owned the plane or if it was someone else's.

I guess I could look into that and see.  I'm also not sure what would be required to swap something like that nor how I'd get the STC since it is no longer available as far as I understand.  Maybe a field approval would work...

Glenn

[donv]

I like the idea of getting your engines working well, really.

Considering that you have the 18, 300 hours might last you several years.

[Roy]

Yes, the Duke engines have a history. 100% agree there.

The 680F I was talking about Morris had with the Mr. RPM conversion was circa late 1980's-early 1990'. In the end he did end up owning it according to FAA records, a part of the "bad ending" the plane had. However that plane is long-since parted out, verified according to the last picture I saw of it labeled at 2016 in KHWD with lots of stuff missing. As for where the STC went, this is too long ago and I was not privy to that part of his business; I bet someone bought it from him knowing him. So that plane is not an option, I just offered it up that a 680F had Mr. RPM with STC on it.

Re: 2900 RPM, please accept my ignorance if this is the case. A geared engine, yes the props are turning 3400 RPM, but aren't the engines turning much less than that? I forget what the gear box ratio is (if I have this right). Note I'm talking about my limited Commander history circa 1985-1994.

Wish I had more experience, and circa today 

Roy 

[Stephen Matusick]

Roy, the geared engines go the other way- the engine turns at say 3200, but the gearbox(and I'm referencing the GO-300) has a 3:4 ratio- so the prop turns at 2400 rpms. Hope this helps a little!

Steve