GarKenyon vs. Parker-Hannifin Hydraulics

I get lots of questions about the differences in the two hydraulic systems on the early Continental-powered Malibu’s, so it seems logical for me to leap into the gap and provide my thoughts in writing.  I fly both versions regularly and believe I’ve got a good understanding of the benefits and detriments of both.

The earliest Malibu’s have the GarKenyon (GK) Hydraulic Systems.  All 1984 through 1985 Malibu’s have GK, and the earliest of the 1986’s do too.  Basically, Piper decided to go to the Parker-Hannifin (PH) system in 1986, but they used up the remaining GarKenyon systems they had in stock.  So, some of the earlier 1986 models have Garkenyon.  From 1986 1/2 and beyond, all PA46’s have Parker-Hannifin (until the Frisby System, which is nearly identical to the Parker-Hannifin in design and operation, became the source around year 2000).

Bottom line forward…I’m OK with either system in the PA46 Malibu, although I prefer the Parker Hannifin System.  If I were in the market to consider an early Malibu, would I avoid the GarKenyon aircraft? No! The early GarKenyon Malibu’s can be a great value.  To me, I’d pursue value, mechanical history, engine type, propeller type, aesthetics, and avionics before the hydraulic system would be a differentiator in a purchase decision. But let there be no misunderstanding…the type of hydraulic system in a Malibu is a differentiator to the market in general and the PH-equipped Malibu’s should draw a premium because they are better. Let’s break the two systems down…

What’s the difference? The big difference is that GarKenyon uses a “one-direction” pump and Parker-Hannifin is a “reversible pump”.  Although this may not sound like a big deal, it is.

The GK system uses a pump that only moves in one direction.  The electric motor turns only one direction which turns the hydraulic pump which can only turn one direction.  So, plumbing is provided and a series of valves are used to move the hydraulic fluid to make the various actuators move.  When the pilot raises the landing gear handle, he/she is moving a hydraulic valve, and this requires a good amount of force (we call it the “knuckle-buster”).  The pressure is applied from the pump and the pilot merely moves the pressure to the side of the actuator that does the desired work (moving the gear either up or down).  So, the pilot’s hand is actually on a lever that is actually moving mechanical devices (valves), not simply moving electrons. For GK-installed airplanes, the hydraulic system usually moves the flaps too.

The PH system uses a “reversible pump” that is turned by an electric motor that can turn both clockwise and counter-clockwise.  It turns one direction to move the gear up and another to move the gear down.  The pilot is therefore not moving a hydraulic valve, he/she is moving an electrical switch that commands the direction of the electric motor on the reversible pump.  The force required to move the landing gear handle is “finger-tip pressures”, and MUCH less than the GK system.  It is a much more simple system with fewer moving parts.

Advantage PH: Protection. There’s one other major benefit with the PH system…protection while on the ground. Since the landing gear switch on a PH is simply an electric switch, it is much simpler to route the action of that switch through the Landing Gear Squat Switch (on the Left MLG).  So, inadvertent gear retraction while on the ground is provided in a robust manner. On the GK system, the landing gear handle moves a hydraulic valve, so if the Landing Gear Handle is moved up while on the ground, the gear will collapse since the hydraulic pressure holding the gear locked down is released. To keep inadvertent retraction from occurring on the ground, Piper added a small guard that moves out of the way (to the right) electrically by the Squat Switch (see video below). This small guard is the only protection that exists, and this guard is (IMO) rather weak. I’ve seen MANY early Malibu’s that had faulty guard’s. Just to be clear…moving the GK “knuckle-buster” Landing Gear Handle takes a good amount of force, and this is not going to happen by simply “bumping” the handle…but, if the gear lever is raised on the ground, the airplane will experience a gear collapse.

Advantage PH: Strength. The PH actuators are physically bigger (larger diameter) than the GK actuators. With this additional beefiness comes added strength. The actual landing gear itself is identical across the PA46 fleet, but the PH actuators are larger than GK actuators. This translates into more strength with side loads on the main gear and with fore/aft movements on the nose gear. To be fair, I’ve not seen a greater propensity of side load problems (improper crosswind landing, improper ground operating technique, etc) in the field on the main gear actuators, but the weaker nose gear actuator does translate into more problems. For instance, if the parking brake were left ON (and NO pilot should leave any PA46 with the parking brake ON…ever!) and the Malibu were towed by a nose-mounted device, a gear collapse could occur more easily with the GK system because the GK actuator is simply smaller than the PH actuator.  I know of one GK Malibu that had a nose gear collapse while being towed, and another had a nose gear collapse after landing on a grass runway that had not been mowed recently (idiot pilot…I know…but still the GK failed when the PH might have withstood the trial).  Bottom line…both the PH and the GK systems are plenty strong enough for use, but neither will allow for abuse.

Another drawback to the GK: Hydraulic Flaps. Except for a minority of 1986 Malibu’s, all GK Malibu’s also have hydraulic flaps. In 1986 Piper moved to electric flaps and there are a few 1986 models that have GK gear and electric flaps. And…the hydraulic flaps need an experienced technician to perform maintenance. The rigging of the flaps is critical and a novice can spend a BUNCH of your dollars trying get it right. If you’ve got GK flaps, be sure to let one of the premium PA46 shops (Malibu Aerospace and Midwest Malibu are the two premium shops, IMO) do that work. GK hydraulic flaps don’t break often (they are very reliable), but when they do require adjustment, take it to a shop that knows exactly what to do. You don’t want to fund the education of your mechanic while he fumbles the job.

Mucho Dinero: Expense. The GK systems is (now) fully supported and the PH System, while fully supported, is getting more and more expensive to support. GK had a bad problem a few years back when replacement nose gear actuators were virtually non-existent. That problem has been rectified by Arizona Aircraft Accessories (a really good company that rebuilds hydraulic parts) obtaining authority to repair the nose GK actuator. A GK-equipped airplane at my airport sat for about a year awaiting the FAA to grant authority to repair the GK nose actuator, and that owner (along with about 6-8 other owners around the country) was not happy. But…that situation has been rectified and the GK system is now fully supported and parts are available. On the flip side, there are LOTS of PH PA46’s out there, and they enjoyed a long history of support. But, PH replacement parts can be a bit pricey.  One trusted mechanic stated, “If you need a PH actuator, and there’s not a good rebuilt one available on the market, you’ll have to go to Piper…and going to Piper for anything will set you back financially.”

Talking with mechanics that are “in the know”, I get the impression that they like the sturdiness of the PH system, and like the fact that the GK system requires more (billable) maintenance.  One mechanic stated that the GK system will, “nickel and dime you to death” (smaller nagging problems), but the PH system will, “work well for many years and then slam you for a high maintenance bill when something goes wrong”.  All mechanics I spoke with felt that the actuators on either the PH or the GK should be overhauled every 2,000 hours, regardless of their apparent functionality.

Parker-Hannifin Benefits:
* Much easier to move the gear switch up and down
* More protection from an inadvertent gear collapse
* More desirable in the marketplace
* Stronger actuators

Gar-Kenyon Benefits:
* Cheaper replacement parts
* Possible “deal” can be made on a 1984-1985 Malibu. They are less desirable in the marketplace, but they are still quite functional and quite safe.

With all of this information, you can see that the 1986.5 to 1988 model PA46’s (equipped with PH hydraulics) are truly special airplanes. There’s not a lot of them available on the market at any one time and they should demand a premium. To me, they are the creme-de-la-creme of the PA46 piston fleet for a sub-$400k value buyer because of the electric flaps and PH gear. But…don’t snub the early Malibu’s with GK gear! If you find a nice example configured as you like with great avionics, great logbooks, and nice P/I…buy it. GK-equipped airplanes are still robust and strong and serve their owners well. Both are good, but the PH is best.

About Joe Casey

ATP, CFI, CFII, MEI, CFI-G Commercial Pilot - SE, ME, Rotorcraft, Glider US Army AH-64 Pilot and UH-60 Instructor Pilot and Instrument Flight Examiner
This entry was posted in PA-46 Airframe systems and tagged , , , , , , , . Bookmark the permalink.