Here is the deal

[ghancock]

So I've been doing a lot of searching and talking about all things airplane over the last 6 months trying to decide what to do.  It is a total shame how difficult it is to work around issues but here is the deal.

1) The hydraulic pumps used on the 680FP and 680FLP airplanes appears to have ONLY been used on these planes.  There are no other pumps around except the ones currently stationed on working FP planes.

2) These pumps are 3000psi skydrol pumps and are this way for the sole reason to run the pressurization system.

3) I bought my plane because it was capable of flying into short grass strips and because it was pressurized and faster than the other similar models.  It also pretty much carries what you put in it.

4) It has engines that are getting older by the day and appears again to have been used ONLY on these airplanes.  I can find no other airplane ever built that used these same engines.  As a result they are getting hard and harder to find and more expensive to rebuild.

5) A Cessna 421 would be the closest thing to my airplane although the 421 is a lot nicer plane in respect to interior and comfort.  They both cruise about the same speed and burn about the same fuel but the 421 has a LOT better pressurization system on it and in fact is better than most of the Turbine Twin Commanders with over 5psi system.  However, I would not want to fly a 421 off a grass strip and some of the strips I fly into are pretty rough.

6) Other airplanes have similar problems, they are either too slow, cost too much or wouldn't be happy flying into the kinds of strips I visit.

So I'm left with either not flying as much and only sticking to larger airports in a larger airplane, or figuring out some way to keep my airplane going.  I thought I had a plane I could use for parts but apparently someone else is already buying it to get it flying which means I'll be worse off for parts.

The thing I fight with every moment of the day is that my airplane is in extremely good condition other than the obsolete parts.  The airframe couldn't be any better and it is a very clean airplane overall.  So... my pipe dream:

Would would be the most perfect airplane in the world to me would be my plane with some sort of turbine on it, but I'm pretty sure that can't be done.  So what other options are there for keeping my airplane flying and still be able to take advantage of the pressurization?  Am I best to just walk away and let her go but if so, what else would I get?  While I can afford the 5-10k a month payments for a larger plane, I don't think I could get a loan for it and I don't think the plane would do what my plane does.  One nice things about flying my airplane off these strips is it doesn't cost a million dollars and as such it getting bumped around a little isn't as big of a deal.  I don't think I'd fly a 980 off some of these strips, even if it could.

There is also the thought of maybe converting the engines to a new model engine but don't know what it takes to do this.  Can you place a Commander into the experimental category to do things like this and if so for how long?  Is it worth the trouble or should I just go back to my 310Q and get rid of the Commander?

The picture I sent of the airplane sitting in the hanger a few months ago is the same picture of it sitting there now.  I've become depressed over the entire matter and not sure what to do about it.

Glenn

[donv]

Have you figured out what goes bad on those pumps, and can you make that part? I'm guessing seals or gaskets or something? Maybe you could make a run of those?

On the engine front, I believe there is a conversion to 720s, although I don't know how much better that would be.

Were the same engines also used on the 680F and 680FL? That might open up some more parts airplanes.

The problem with running a turboprop on rough strips is that you'll chew up the props pretty quickly, especially if you use reverse at all. However, used Dowty props are pretty cheap, so you could possibly buy a few sets and keep one in reserve. Once they get chewed up past a certain point, I don't think they can be overhauled, and that's where it starts to get expensive.

[ghancock]

Well, the pumps are nothing but a plate and connecting pistons but they basically blow completely apart and eat themselves.  So when they burn up they basically blow up and nothing is left to fix.  I also don't have the drawings or the repair or service manual so have no idea of tolerances or anything else.  The 720's cost more than the current engines and from what I've heard don't perform nearly as well.  While that is an option it might not be a good one.  Morris said something about the Lycoming 350 being a great choice and that they would outperform my engines but not sure how I'd go about putting them on.

So really not sure.

Glenn

[Badger]

Sorry Glenn.  I hate to hear that.  I wish I had an idea for you.  I do hope you can figure something out with your commander.  It is a beauty!
ed

[donv]

Have you spoken with Geoff at Twin Commander about the pump specs and drawings?

Could you make your own parts? I believe you can, under some circumstances, for your own use.

[donv]

If you did Lycoming 350s, you might as well get a Shrike. It will be much lighter as well.

[ghancock]

Except that its not pressurized.  I could use the bleed air for the pressurization and get rid of all that junk in mine, making it lighter as well.

Like I said, it is all a pipe dream as I don't know what it would take to even do something like that.  Hopefully I can figure something out though.

Glenn

[donv]

I would think that in the end, it would be easier for you to work with Twin Commander to make the parts for the hydraulic pumps, as opposed to re-engineering the entire airplane.

[SKYFLYER]

"Pipe dream" or not.. it is now all about time and taking a positive direction towards getting the correct aircraft for the mission and one that is supported so parts failure will not be an issue.

Without a good parts plane to support yours.. it will be an ever increasing hassle to secure usable spares as you are already painfully aware of.

The "Experimental" category will not work as it will have both time and use restraints. And as Don has pointed out re-engineering the aircraft simply would be far too costly and take years.

Seems your needs require pressurization, rough field capability, reasonable speed, carrying a good load and not being a million dollars.

WOW... you just described YOUR Commander.

So... short of finding a horde of "green" tagged pumps sitting on a shelf in some far off land... the ONE AND ONLY serviceable pump will be the one you get back from the overhaul shop. Making your Commander come back onto the flying category.

Now... do you resume your flying missions (400hrs a year I think you said) until the next parts failure puts you in the AOG category or sell to someone that will get a few more years of enjoyment out of it.

Finding a suitable parts plane is the ONLY real solution to keeping YOUR Commander and meeting the mission requirements that you have... in this lifetime.

Short of this... a PC-12NG would be a perfect choice .. well... all except for the million part.

Just my one and a half cents worth 

[donv]

Actually, a 690A would be the perfect, and logical choice.

Really, you have three paths:

1) Continue to maintain your airplane, by purchasing parts whenever you find them (whether you need them or not), and by making parts-- I'd suggest working with Twin Commander closely. Your airplane is more like an antique car, and that's how the antique car guys do it.

2) Downgrade to a 500-series Commander.

3) Upgrade to a 690A, and buy a spare set of props to keep in your hangar.

In part, it comes down to your priorities. If you really want to use the airplane as practical transportation and do the kind of missions you've described in the past in safety and comfort, the 690A is the only logical choice.

If you enjoy working on your airplane, hunting down rare parts, having a rare piece of machinery where you are the expert on it (and which you can rightly boast can do things no other airplane can do!), then keep your airplane going.

If you just want an airplane which can more or less do your missions cheaply, buy a 500.

[drwho67]

Hello Glenn,

I posted this a while back, I'm not a pilot unfortunately and I know nothing about the ins and outs like the other guys but these 2 planes look interesting.

If this was previously listed I appolagize.

1974 Rockwell Commander

690A serial 11210  N70MD
$295,000 US

AIRFRAME AND ENGINE STATUS:
Total Time Airframe: 7854.9
Total Time Left Engine (S/N P38251) SOH/SHS: 5400/1800
Total Time Right Engine (S/N P38282) SOH/SHS: 5400/1800
Total Time Left Propeller SOH: May 2016
Total Time Right Propeller SOH: May 2016
150 Hour Inspection Due: August 2016/111 hrs.
Landing Gear Overhaul Due: May 2016
Wing Spar Inspection Due: May 2016

AVIONICS:
Garmin 530W
Garmin 430
Garmin GTN 600
XM Weather
Encoding Altimeter
Collins AP 106 Autopilot
Altitude Preselect   
Collins ALT-50 Radio Altimeter

ADDITIONAL EQUIPMENT:
Winglets
Nose Landing Lights
Strobes
Cleveland Wheels and Brakes

INTERIOR:
Configuration A
Seven passenger gray interior
Pilot seats done in sheepskin

EXTERIOR:
(2006) White w Gold and Black Trim

Specifications subject to verification upon inspection
Contact: Norman Ralston at Aero Air, LLC 503 640 3711, nralston@aeroair.com

http://www.aeroair.com/aircraft_sales/Aircraft_For_Sale/1974_Twin_Commander_690A/

2nd Plane

https://www.controller.com/listings/aircraft/for-sale/17876961/1975-commander-690a

Brian

[drwho67]

Here is another one, the price is not listed but age wise it's the oldest.

https://www.controller.com/listings/aircraft/for-sale/1425661/1972-commander-690a

Brian

[Huck-Mag]

Glenn,

The ISGO-540 was also used on Queen Airs. Don't know if any Queen Airs were pressurized or about the hydraulic pumps but you might check that out.

Brent

[donv]

I know that early King Airs (straight 90 and maybe A90) also used hydraulic pressurization, but I don't know much about the system or which pumps were used.

[Adam Frisch]

Just get mine, Glenn. Avionics shop is finished with her now, now she gets pressurization leaks plugged and interior put in. She'll be ready by the fly-in. I'll call you when I'm back in LA and talk. I'll make a deal we can both live with.