A new Skymaster Owner enters the forums

mshac · #1 08-09-20, 06:39 PM

Greetings to the membership! I've only recently become a 337 convert, coming from a long history of owning Barons, 310's, Bonanzas and the like.

I bought a 1978 P337H that was owned by a doctor for 32 years. The maintenance looks good - maybe I won't complain as much when I pay my doctor bill next time.

The Pressurized Skymaster II has boots (in good condition) and a hot prop on the front, but no hot prop on the rear. I guess the exhaust naturally keeps the ice off the rear prop? It has a provision for a hot plate, but none was included with the sale. Anybody have one lying around?

First trip home was 540nm on a 132 heading flown at 17.5K. Flight averaged 205 knots and 28 GPH. Plane could of performed even better, but I ran it well rich of peak as I'm told I should with turbos. Even some slight leaning would have saved 2-3 GPH as my TITs were low at about 1350 vs. a 1650 max. As I get to know the plane, I'll try different leaning strategies.

Aircraft was purchased with a known fault of the rear alternator not charging. Once I was home, I pulled the front cowl and checked the voltage regulator (VR). It showed good DC voltage on the red bus line ("D" line) and the blue field line about a volt less, as it should be. Every thing points to a bad rear alternator. Although...

Rear alternator was changed at the last annual and looks brand-spanking new, which makes me suspect a bad connection between the blue field wire coming from the VR and the alternator. I need access to the alternator, but can't just from removing the cowls.

The service manual refers to removing interior panels to gain access to the rear firewall service port, but doesn't give any directions on how to do it. I'm sure I could start taking things apart, but I'd much rather have photos or a guide so things would hopefully go more smoothly. Any advice in this regard would be much appreciated!

EDIT: Gaining access to the rear engine was a cinch. The problem is trying to work in 109 degree Texas heat (hanger is full again!). It was easy:

Three interior panels on the rear wall come off in seconds (they were velcroed in my plane), then the engine access cover has 8 3/8" bolts. Took maybe three minutes to gain full access. Photos in a later thread!

JeffAxel · #2 08-10-20, 01:19 AM

pictures, or it didn't happen! As to getting to the rear alternator, take the interior coverings off the rear wall of the cabin and there is an inspection plate you can remove to get access to the rear alternator and magnetos. What tail number did you buy?

mshac · #3 08-10-20, 12:07 PM

Can't for the life of me understand how to post photos here. None of the photo options I'm used to seeing in other forums! And most of my pics exceed the 1MB limit.

mshac · #4 08-10-20, 12:11 PM

Here is a pic of the CNX80 showing 210kts. I also attached the speed/altitude printout from the flight.

JeffAxel · #5 08-10-20, 08:21 PM

Nice, saw the advertisement. Do I remember that both engines were very high time? I was tempted to call our local engine shop (Premier Aircraft, Troutdale OR) to see what overhauls would cost for that plane but the ad was gone before i got a chance to call. Have fun with it, and I would suggest getting a Parts Manual and a Service Manual, very helpful items to have.

rrolland · #6 08-10-20, 08:50 PM

Congratulations! Enjoy flying the airplane. Looks pretty good.

mshac · #7 08-10-20, 09:26 PM

Quote:

Originally Posted by JeffAxel

Nice, saw the advertisement. Do I remember that both engines were very high time? I was tempted to call our local engine shop (Premier Aircraft, Troutdale OR) to see what overhauls would cost for that plane but the ad was gone before i got a chance to call. Have fun with it, and I would suggest getting a Parts Manual and a Service Manual, very helpful items to have.

Yep, that's the one. I was "johnny on the spot with cash" or I would've never been able to buy it. Seller had almost 100 phone calls within a few hours.

Greatest news is that engines times were being kept off Hobbs, but I found a log entry a few years back that says the engine times are much lower. The tach time is much less, closer to 1000. Either way the engines look like they're only a year or two old. Soft hoses, shiny clean surfaces, etc. I'm gonna replace a few cylinders on the back, but the front is all solid.

May do GAMI's, they are just up the road a bit from me. Not sure what the fuel flow mafia has to say about LOP operations on a turbo.

Red Air Rambo · #8 08-11-20, 12:07 AM

Welcome and Congrats!

JeffAxel · #9 08-11-20, 01:01 AM

I had GAMIs on my P337 and the engines ran fine with them. Ran them at 65% power, 23-24gph total in cruise which got me a TAS of 185 in the high teens with cool temperatures even in the summer with the cowl flaps closed. My P337 had intercoolers, air conditioning and VGs so was slower than some, you might do better TAS wise. The best part was the cylinders looked clean as a whistle when we borescoped them. Never had to clean spark plugs.

mshac · #10 08-11-20, 09:41 AM

Quote:

Originally Posted by JeffAxel

I had GAMIs on my P337 and the engines ran fine with them. Ran them at 65% power, 23-24gph total in cruise which got me a TAS of 185 in the high teens with cool temperatures even in the summer with the cowl flaps closed. My P337 had intercoolers, air conditioning and VGs so was slower than some, you might do better TAS wise. The best part was the cylinders looked clean as a whistle when we borescoped them. Never had to clean spark plugs.

Air conditioning is the ONE THING this plane doesn't have that I REALLY wanted. Intercoolers, winglets, STOL kits, and VG's are all cool (no pun intended), but when you walk outside into a North Texas August day - 100 degrees, 60% humidity - its AIR CONDITIONING your body and mind are wishing you had!

First flight, I took off south of Denver from about 6700' on a 90 degree day. Wouldn't want to do that in a non-turbo! Heat wasn't really an issue leaving Denver climbing to 17.5K, but cabin temps were beginning to get a bit uncomfortable during the last minutes of the flight as we descended down into the Texas heat to my home airport at about 700' elevation.

Whatever airspeed and useful load you may give up is WORTH IT to have AC!!!

Regarding GAMIs, do you lean to peak TIT, or wait for the last cylinder to peak as you lean for LOP operations? I got about 28 GPH, but I was feeding it fuel like a drunken sailor on shore leave. TIT never went above 1400. I actually ran the rear engine a bit richer to keep its temps in line with the front. Probably should've just opened the rear cowl, or just accepted the temp diff. CHT's were all well under 400, so it wasn't a huge deal, just 10-20 degrees higher in the rear.

mshac · #11 08-11-20, 09:59 AM

Ok, its not much of a mod, but I repaired the broken courtesy light circuit in the overhead clamshell door, and installed a 24 volt LED bulb that really lights up the cabin entry area, and runs cooler and uses fewer amps. You need a special two-contact type bulb - Here's a link to the bulb I used: https://www.amazon.com/dp/B00BZWLK6U..._hxPmFbJ27V21B I'll post up some night pics this evening.

Jerry De Santis · #12 08-11-20, 10:07 AM

I have 1975 P337G with Boots, Riley A.C. Riley inter coolers, spoilers etc. been flying this plane for 22 years. I found operating rich of peak has given me best performance and longer component life. I operate at 27 to 28 GPH. As for air cond. I suggest you check out an electric drive unit. There are several on the market. The alternators in the Skymaster are heavy duty and can carry the load. Also, if your plane is not equipped with spoilers and you intent to fly in the teens all the time, with spoilers you don't have to change engine setting when descending. Thus, don't have to be concerned with engine shock cooling. I almost always fly with engine settings of 2450 RPM and 31 inches.
Good luck and enjoy your new plane.

mshac · #13 08-11-20, 10:26 AM

Hello Jerry. What a nice 337 you must have!

At 17.5k, I ran 2450 but was getting more like 29". This was a very hot day, even at that altitude air was still in the upper 40's. Should I see higher MP on a colder day, all else being equal?

Another question for an experienced owner - what does "bootstrapping" mean in reference to the twin-turbo pressurization system? This is a new term for me.

Learjetter · #14 08-11-20, 10:41 AM

Quote:

Originally Posted by mshac

Ok, its not much of a mod, but I repaired the broken courtesy light circuit in the overhead clamshell door, and installed a 24 volt LED bulb that really lights up the cabin entry area, and runs cooler and uses fewer amps. You need a special two-contact type bulb - Here's a link to the bulb I used: https://www.amazon.com/dp/B00BZWLK6U..._hxPmFbJ27V21B I'll post up some night pics this evening.

Nice! Welcome to the boards. Wealth of info here, a fantastic resource.

My courtesy light in the overhead clamshell door is also inop (someone cut the wires where the door meets the fuselage). I'll try your bulb suggestion, if I can figure out how to get voltage to the wiring harness.

mshac · #15 08-11-20, 10:45 AM

Quote:

Originally Posted by Learjetter

My courtesy light in the overhead clamshell door is also inop (someone cut the wires where the door meets the fuselage). I'll try your bulb suggestion, if I can figure out how to get voltage to the wiring harness.

Don't forget, there is a 1A glass fuse under the front cowl on the pilot's side that feeds the courtesy light circuit. Mine was blown, I bet yours is too.