PA32R(T) Overhaul Considerations – Part 2

 June 2002

Part 1 of the article concerning these aircraft focused on firewall forward and some does and don’ts during an engine overhaul. Part II discusses some systems to focus on in addition to the approved checklist during an annual inspection.

 Most of the T-tail Turbo Lances and early Turbo Saratogas left the factory with a built-in oxygen system. The typical system consists of a 3HT series lightweight aluminum oxygen bottle. A SkyOx altitude-compensating regulator meters oxygen from the bottle to six outlets located in the headliner. A pressure gauge and filler valve are located on the aft cabin bulkhead just below the hat shelf.

The SkyOx regulator is obsolete now and it is difficult to find anyone to refurbish it. If your regulator still works and does not leak O2 with the valve on, then consider yourself fortunate. Simply closing the oxygen bottle valve after flying will extend the regulator’s life. If this regulator needs replacement, a Scott or Aerox may be installed but they are expensive. The bottle is due a hydrostatic test every three years and has a twenty-three year life limit. These are DOT requirements, not FAA. If your airplane was built in 1978 then it probably has a 1977 bottle in it. A quick computation reveals that the factory installed bottle was due replacement two years ago. A new 76 cubic ft. 3HT bottle will set you back over $1,000 and this does not includes the regulator. If both regulator and bottle must be replaced it may be cost effective to purchase a complete installation kit.

The electric/hydraulic landing gear system requires close inspection and proper testing. The motor-pump has a useful life of about 2500 hrs. If you fly long cross-countries the pump will last longer than with short hops with more gear cycles. The gear is held in the up position by hydraulic pressure provided initially by the motor-pump. A hydraulic valve traps pressure when the pump stops. As the pump wears out gear retraction takes longer and longer. During retraction, the motor-pump will operate if any gear limit switch is not open or if the 1800 psi switch is not open (they are all wired in parallel). If the system does not reach 1800 psi due to excessive internal leakage, pump deterioration or low motor voltage, the pump will run continuously. A leaking hydraulic valve in the pump or the auto gear extension system will bleed off pressure and below 1800 psi the motor-pump will start. In flight the pilot cannot hear the gear motor running. Abnormally frequent cycling or continuously high ammeter readings are an indication that something is wrong. Further investigation is recommended.

Historically, the auto gear extension system has had several problems. Some gear up landings and more frequently, early retractions have occurred from the pilot relying on the system to operate the gear. As a result, in 1987 Piper issued Service Bulletin 866 requiring removal of the system. The next year, SB 866A allowed continued operation if you maintained and operated it properly (any humor intended here is accidental). Of course, we all know that service bulletins are optional for Part 91 operators.

Ice blocking the hole on the landing gear pitot mast (on the left side of the fuselage) would simulate a low airspeed and cause the landing gear to free-fall in cruise flight or not retract after takeoff. Both improper pilot procedures and the system failures due to improper operational checks during annual inspections have caused incidents. When the pilot pulls and locks out the auto extension system he operates a hydraulic valve that is normally activated by air pressure from the pitot mast inflating a bellows located under the left center passenger seat. This action also activates a micro-switch that allows the landing gear motor-pump to raise the gear if the gear selector handle is in the up position and the right main landing gear is extended activating the squat switch. Constant engagement and disengagement of the override system can cause the o-ring in the hydraulic valve to wear out prematurely. As designed, this system does provide a gear down backup.

The PA32R landing gear is a loose tolerance system compared to Beechcraft or Mooney. Because hydraulic pressure and springs pull the gear to the over-center position and hooks with pins lock the over-centers, loose clearances are necessary. However, tolerances for the retract pivot clevis bolts and bushings on the main gear are critical. The parts must be kept greased and snug; not so tight so they can’t rotate but not so loose that they move from side to side when a side load is placed on the landing gear. These units unbolt from the main spar and have a castle nut and roll pin that secure the clevis bolt in the housing. Piper sells a special washer available in different thicknesses that is installed under the castle nut to tighten the clevis bolt as it and the bushing wear out. Most of the bushings in the main gear retraction mechanism are a press fit and should not fall out of their housing when disassembled.

The nose gear hook and pin (on the engine mount) must engage completely. Over the years, Piper has had problems with nose gear retract cylinders breaking off at the fuselage fitting. The PA32R was the subject of an expensive airworthiness directive that required modification of this fitting. Check this area carefully. Insure that the aft retraction pivot points are not so loose that the bushings or the bolts are wearing out. Verify that the rubber stop limiting the nose gear travel is still intact and set at the correct adjustment. When the landing gear is retracted the brake lines must not catch on the airframe and all gear doors must close completely. Verify that the nose gear tire seal is intact.

Another common problem on aircraft with the Piper electric trim system installed is that the trim cables become frayed where they go through the tensioning pulleys. To inspect this area you must pull the trim cables all the way through their travel and inspect both cables and their routing through the pulley system.

Both front seat shoulder harnesses are recoil type belts. It is not uncommon to extend the belt to the stop and find it frayed. Always check the seatbelts for serviceable condition.

 Properly maintained and operated, the Lances and Saratogas have been pretty good airplanes. This article does not encompass a complete annual inspection but should supplement your approved annual inspection checklist.

As always, if you have any questions about this article, please e-mail me or phone my aircraft repair shop at 307-789-6866. Until the next article enjoy flying your Piper.