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Seneca Mods

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October 2004 -

When I bought 1176X four years ago, I really did not plan to restore or modify the aircraft in any way, but as I got into the project, I discovered that there are more than 50 Supplemental Type Certificated products or modification for the PA-34-200T.
These STCs can be for things as simple as a better sun visor to as complicated as a vortex generator set that actually changes the way the aircraft flies. After careful consideration, I selected the STCs that I felt yielded the best "bang for the buck."
Maintenance issues compelled me to purchase the Bogart Oil Filter Access Door STC. This modification allows you to perform an oil change, including the filter, without dropping the lower cowl.
Copper starter cables were purchased because the factory-installed aluminum cables drew so much current that the aircraft was difficult to start under any conditions. The copper cables were so effective you could almost taxi the airplane on the starter motor alone.
The one-piece windshield and Rosen sun visors came with the aircraft, though I would have opted for both of them. The same for the JPI engine analyzer. I don't see how you can properly operate a turbocharged piston engine without one.
The Nayak auxiliary nacelle tanks were also installed on the aircraft when I purchased it. This mod brings total fuel capacity to 128 gallons.

 In pursuit of more speed, I invested in the Knots 2 U flap gap seals, wheel fairing kit, aileron and flap hinge cover kits, as well as the LoPresti axial flow cowls. They delivered as advertised and my Seneca beats the book numbers by 10 knots regularly at all altitudes below 10,000 feet, and more as I go higher.
The Boundary Layer Research VG kit was selected to obtain better short and soft field performance—which it delivers, plus the added safety enhancement of a lower Vmc and a practical increase of 166 pounds in zero fuel weight.
I installed the C&D combustion heater because the factory original Janitrol unit that was installed in the plane when it was purchased needed to be rebuilt, and even then it still would have a recurring AD with which I would have to comply. The new unit puts out more heat and is free of recurring inspections.
I installed an inflatable door seal primarily to correct the poor door-to-fuselage fit the Seneca came with, and to reduce cabin wind noise and keep the rain out.
Had I needed to replace the props, (it turned out that I was able to overhaul the existing units) I would have gone to the STC'd Hartzell three-blade propeller.
STCs I didn't go for include the Meryln Magic wastegate and several engine intercooler STCs, all of which promise cooler-running engines. Since I was not having any temperature problems with the engines and I live on the East Coast—thus limiting the amount of high and hot operations I would be engaged in—I felt I could not justify the expense.
I also passed on the Keith Products air conditioning system, mostly because of a single part required from Continental. That part, a pad that allows the air conditioning compressor to share the accessory pad with the alternator is only sold as part of a kit, and the kit cost in excess of eight thousand dollars. That made installing the Keith air conditioning kit economically impractical.
Some things I have yet to do? I'd like to install G&D acrylic window liners, and I am considering replacing the original Century III autopilot with a newer model from S-Tec. I am also considering GAMI injectors, which would yield more uniform EGTs and CHTs on the Continental TIO-360EB engines that power the Seneca II.
My modified 1975 Seneca II now performs as well or better than a brand-new Seneca V, and it does so for about 1/5th the cost.
Michael Leighton is a 3,100 + CFIIMEI/ATP as well as an A&P mechanic and former FAA Accident Prevention Counselor. He operates an air charter company in South Florida. You can reach him via e-mail at .


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