Test flight

Kevin B · #1 03-14-04, 10:45 AM

My partnes and I test flew a 1976 P337G yesterday. The plane seem to perform well. With some concerns:

1) The auto pilot was inop can it be repaired or do we need to replace $$$? It is a 4000A. It held altitude but not heading.

2) The gauges for the oil pressure on the rear eng was inop unless you pushed on it then it worked, and the fuel gage for the left tank was inop. Can we repair this cluster?

3) The one mag on the front eng needs repair

4) There seems to be a vibration in the rear seats during the climb out but in cruise it does not exsits. It seem like there is a buzzzzzing or vibration on the seat bottom cushion. Is this typical of the rear during high angels of attack?

5) My big concern is that there is oil all over the belly and rear eng cowling. It was wet to the touch. Has any one found a way to prvent this. Is this normal for the Skymaster. There are 2 notes of the rear eng crank case having been welded. Once during the overhaul in 1987 and once in 1995 I think. How do we know if this case is a heavey case or not. it has a total of 540 hrs on it. The rear turbo has never been overhauled but the waste gate and some the the componens have. Anny Idea what an turbo over haul would cost?Both engines devlope full power with no trouble

Any input would be a great help!!!
Kevin B

The balance of the plane is in excelent shape

Mark Hislop · #2 03-14-04, 11:24 AM

Kevin:

The autopilot can be repaired. If it's holding altitude but not heading, it might be the autopilot, or it might be the output of the DG. Try Autopilots Central in Tulsa. They are reputed to be the experts on the 400A. They can help troubleshoot over the phone.

As for the oil on the belly, first check in the engine compartments. Are the engines dry, or is there evidence of oil leaks any place on the engine. If the engines are dry, then the oil probbly is coming out of the breather. This could be because there is too much oil in the crankcase. On my 73 P337, if I put the recommended 8 quarts in, the first two quarts goes out very quickly, and then oil consumption stabilzes. There also could be problems with the air/oil separators.

Check the data plate on the engine. If it is a c6b, then you have the heavy case. If it has been welded twice in the past, chances are you have the original c6 engine, which was the light case.

I had my gage cluster rebuilt a few years ago. I don't remember who did it, but I'll look it up today when I go out to the airport.

Mark

kevin · #3 03-14-04, 11:34 AM

Adding to Mark's reply:

The buzzing in the rear seats does not seem normal to me, or at least it is not normal for a '65 normally aspirated or a '73 P337. I can't think of what it would be.

The only part of what you described that I would be nervous about is the oil. Wet to the touch is not normal. I would follow Mark's suggestion, and identify where the oil is coming from.

Kevin

Jerry De Santis · #4 03-14-04, 02:59 PM

Kevin, Is it a Michigan plane? What is the N number?

The vibration in climb but not in cruise can be cowl flaps. I assume they are open in climb and closed in cruise. I am on my second Skymaster and living with oil leaks is a way of life. Seems only after a few oil free flights after tighten bolts etc, than the leaks start again. I agree with Mark, put 8 quarts of oil in engines and they spit two out quickly. I general keep 6 to 6.5 quarts in all the time.

Regarding the weldments twice on the engine....Beware!!!!

Regards
Jerry

Kevin B · #5 03-14-04, 04:05 PM

Jerry ,
No the plane is down in SC. N325 the same Person you bought your plane from. After more thought I think the rear turbo may be the reason that there is so much oil as it has never been overhauled!! The plane had a engine install in 84 and is not the orignial factory eng That is the reason for the heavy case question.

The rear vibration may also be the reason for the cracking case Do you think that getting a Harmonic prop balance would help?

SkyKing · #6 03-14-04, 05:48 PM

Kevin,

As to the gage cluster, if you're getting intermittant indications when you push on the front, chances are the plug/receptacle on the backside with the wire bundle has wiggled loose\, or the contacts might be corroded. A cleaning and replugging might be all that's needed. Go through the avionics compartment hatch and take a look see... chances are very good that the problem is the slide-on plug and/or the contacts.

As to the turbos, you'll need to remove the cowls and visually inspect the center section where the oil line attaches. Of course there are seals on either end that might be going south. On the front engine, take the air cleaner out and with mirror and light, visually inspect the impeller to see if there's any FOD that may have caused nicks or damage... also you can hand turn it and see if there's any axial play or rubbing. Same thing with the rear unit, although it's a little more involved to check. If you have someone with small hands and arm, they can reach through the rear exhaust pipe and feel for axial play... that is, if the person with the small hand/arms knows what they're feeling-looking for!

Also, I think the heavy-cased rear engine is the "CB6B" and the light case is the "C" model, the latter of which was prone to cracks at the rear position. The rear prop bulkhead should also be checked!

As to oil on the belly and/or tail feathers, NO this is not normal. But as others have indicated, if the oil has been topped off to the full 8, it's going to throw out the first 1.5 to 2 quarts... and it WILL be on the belly. Every P337 owner I know runs with 6 to 6.5 quarts on the dipstick.

I presume you have an independent shop and/or mechanic who is or will be doing a "pre-buy" inspection for you, and if you're not.... buyer beware! A "Test Flight" is not conclusive that you're not buying a Pig-In-A-Poke.

Interesting that you're giving us the heads-up on this bird, as a friend of mine has been curiously looking at this ship. Seems the interior was 'dolled-up' to make it more saleable... ah, that nice 'Corinthian' leather!

SkyKing

Mark Hislop · #7 03-14-04, 07:47 PM

I checked my logs. I had my gage cluster overhauled by "Aero-Mach" in Wichita, KS. The overhaul included rescreening the faces of the fuel gages.

Mark

SkyKing · #8 03-14-04, 08:05 PM

Mark,

Curious what was included in the 'overhaul'... was it just a matter of rescreening, or was there something actually wrong with the gages or the printed circuitry on the backside? Do you recall what they charged?

Wonder if "Aero-Mach" is still in business... do you have an address or phone, or website for them?

Thanks.

SkyKing

Kevin B · #9 03-14-04, 08:06 PM

Thanks every one for the info we are going to try and bring the plane here to Michigan for the pre buy. The gauge cluster is cracked in the back,
Please if you can think of any other relavant information keep the tips coming.
This is a great forum of information and a great group of informed owners.
Hope to see you all in Ok. in April

Dale Campbell · #10 03-17-04, 09:57 AM

I purchased a 337H 4 years ago and love it. I spent a great deal of money getting all the bugs out. The oil on belly was solved by replacing most all the valve lifter tub seals & putting M-20 air/oil seperators on both engines. My auto-pilot also did not work. After pulling all components and sending it back to Auto Pilot Central 6 times over a period of a year. I ended up spending over $6500 to get it to work. If I knew that going in, I would have put in a S-tec. Auto-Pilot. The viberation is something out of balance that is turning. I agree with the other postings. It could be prop or turbo causing vibration. Higher RPM would amplify problem.
I would have a good A/P that works on 337's check it out before purchase. Just my opinion.

bede1@msn.com · #11 03-18-04, 08:10 PM

I would look into the oil on the belly problem. I have approz 450 hrs on the frt engine and 650 on the rear and never see anything but the black exhaust marks on the belly. I keep the oil at 8 qts. It stays there at that point for 12 to 15 hrs before I have to add any, usually 1 qt by that time. As long as you keep up on the oil leaks the belly should not see any oil. This is what I have seen on my bird over the last 2 years. Compared to my Beech B80 this this aircraft is like a desert (no moisture). Can't even compare this bird to any other, it's been a dream.

hharney · #12 03-20-04, 10:39 PM

WHAT TYPE OF OIL DO YOU USE?

bede1@msn.com · #13 03-20-04, 11:26 PM

I have been using Aeroshell 100. Its' been very good as far as keeping the engines together. (Knock on wood.)

MikeZ · #14 03-21-04, 08:45 PM

I've had my 79 P337H now for 14 years. Bought it from Jack Riley, almost a full conversion "squawk free". Took me about 5 years of one hour in the shop for two hours of flying (if I was lucky). Eventually, everything was replaced or overhauled, and one day, it just kept flying and flying. Of course now I still do progressive maintenance with my own top notch IA who runs my shop, and the plane is still generically harder to work on than some others only in terms of access, but it is truly a pleasure to fly both mechanically and aesthetically.

It sounds to me like the plane you are looking at has been badly neglected. With that many obvious squawks, chances are a qualifed shop will find many many more. There will probably be dozens more that will just turn up after you own it. Budget many many thousands of dollars to get it reliable and make it what you want. If you do and you do not scrimp, and you are buying the plane for a long term hold, then you will love it and get your money's worth. If you are buying a neglected plane and only plan to keep it a few years, you'll never recoup.

As Dale said, don't put money into the 400. Get an S-tec and write the check once and be done with it.

Best of luck.
mike

Paul Sharp · #15 03-23-04, 05:39 PM

My '67 has always leaked some oil. Many others also do. The question is where does it come from? In my case there are some small leaks in the rear engine around the casing at the output end. The engine will get a new O/H before a lot of time goes by, so what is it worth to stop the leaks? If you were to check under a lot of conventional (engines on the wings) twins I be you'd find a good number who have oil under their cowlings, and "wet" if the airplane is flown regularly. A few small leaks that from known sources that aren't serious are not really that uncommon on many models - not just the Skymaster. It's more obvious in the Skymaster, though.

I know the leaks CAN be tracked down and fixed but depending on what the cause is and the amount involved, is it worth it? In my case I'm just going to wait for the overhaul since I know where the minor leaking occurs and it's not a safety problem.