What to look for in a prebuy?

[ljmolina]

Here is what I have so far... Anyone, please feel free to add to list of known skymaster problematic areas or issues.


 FUEL LINE LEAKS
-Look for Obvious Fuel Line Leaks

 OIL LEAKS
-REAR ENGINE notoriously known for oil leaks.

 FULL FUEL CHECK
-If you fill the tanks too fast the inner tanks does not fill as quickly as
the outer tank and can cause you to lose up to 12 gals.

 MAG CHECK REPLACED?
-Mags are good for about 300-400 Hrs
-Are they Pressurized Mags?

 FUEL PUMPS - need clarification
-something about setting fuel pump to LOW and if the engine needs
more fuel pressure, they automatically go HIGH?

 ENGINE MOUNTS
-Check engine mounts (especially the rear)

 ALTERNATOR
-Check Alternator drive couplings for slippage. The wear out before
TBO, and can cause Internal Engine Damage.

 VACCUM PUMPS
-Most of the time they are 300 hrs pumps and need serviced.

 LANDING GEAR DOORS
-Check for gear door droop. If they do, the Gear Accumulator is bad
(located near under the pilot seat)
-Manually Cycle the Gear

 LANDING GEAR POWERPACK
-Top off with Hydraulic Fluid (behind center pedestal)


IN FLIGHT

 POWER ON TAKE-OFF
-Make sure the Power Red Lines on take-off

 JANITROL HEATER
-Verify functioning (Just replaced / refurbished)

 FUEL FLOWS
-Check that Fuel Flows Match

 THROTTLE POSITION
-Verify throttle positions are aligned

 GAUGES
-Make sure all gauges have correct readings.
-FUEL GAUGES ( Right Gauge was just replaced)
-OIL PRESSURE
-ENGINE TEMPERATURE

 ALTERNATOR FUNCTION
-Check each alternator
-Switch Front OFF (Verify the rear alternator picks up the load and
Warning Light) then, back ON
-Switch Rear OFF (Verify the front alternator picks up the load and
Warning Light) then, Back ON

 CABIN PRESSURE CHECK
-Take Plane upto 17,500 ft and ISOLATE each engine and check to see if
the cabin pressure can maintain max differential pressure (3.25psi)

 AUTO PILOT
-Verify Altitude HOLD
-Verify Heading HOLD

 NAVIGATION
-VERIFY VOR / ILS functionality

[mshac]

Originally Posted by ljmolina

 CABIN PRESSURE CHECK
-Take Plane upto 17,500 ft and ISOLATE each engine and check to see if
the cabin pressure can maintain max differential pressure (3.25psi)

You don't need to go to 17.5 to verify the pressurization system. You could do it at 8.5, just be sure the differential gauge on the pressurization control panel is at max.

That said, taking the plane to 17.5 will expose bootstrapping, weak mags, and weak wastegates/turbos. Its well worth it to fly that altitude during the prebuy if at all possible! If one engine can't hold manifold pressure or starts to miss up there, you know you have an issue.

These airplanes were designed to fly high. They are both faster and more efficient the higher they go. I find 17.5 to be a "sweet spot" on a lot of trips. You're VFR, but with flight following at that altitude, you get great service from controllers, almost as if you were an IFR flight. Also, there is very little traffic at that altitude. I'll go hours without ever seeing another aircraft sometimes. My father once complained that it was "boring" flying so high because he couldn't see anything, so I flew him from Nashville to Dallas at 2500 ft - he loved every minute of it! Kept me out of a strong headwind too

[ljmolina]

Thanks for all the info... Im kinda nervous and excited as this will be my first plane I own...the skymaster has always been my childhood dream plane...and now I can afford one...I hope it goes well Monday.

Luis

[mshac]

Best wishes for Monday.

Remember, make the decision with your mind, not your heart. It can be very hard to do in these types of situations, but you will be better off.

If you do buy it, you can always get great support here.

[ljmolina]

I understand...As much it will hurt, I am willing to walk away.

[JeffAxel]

Max pressure differential on the P337 is 3.35psi. Should hold a 10000ft cabin at FL200 with either engine running. Check the flap cables, they make a sharp bend and the damage is hard to see, Cessna put out a SB on this a while back. Use every radio, autopilot and piece of avionics and make sure they all do what they are supposed to do. Make sure the pitot heat works, hard to find replacements.

[mshac]

Let us know how it went today!