Intercoolers on a piston PA46

One of the really cool aspects of my work is the ability to work alongside the super-neat people that own/operate a PA46.  Those that own PA46’s tend to be interesting and successful people with a special business niche in the American marketplace.  Recently I got to train someone that I found particularly interesting…MMOPA past president and current Ombudsman with Piper, Jon Sisk.  He’s been a part of many STC’s, upgrades, and enhancements to the PA46 family of airplanes, and many of us have benefitted from his creativity and leadership.  His airplane has several modifications that I found interesting (AOA indicator, avionics upgrades, LED lighting, etc,.), but the one I found most intriguing was his engine monitor.  He set up his EDM900 to display the induction air temperature just downstream of the turbo charger and just after the intercoolers.  These temps told me much that I was not aware about the Lycoming engine.

All of the included pics in this Article are of the EDM 900 Engine monitor on Jon’s Mirage.  A bit of explanation…
* All temperatures illustrated are Fahrenheit (degrees F), except for the OAT, which is listed in Celsius (C).  I converted Celsius to Fahrenheit in the discussions below.
* CDT = Compressor Discharge Temperature (Temperature of the air leaving the Turbocharger)
* IAT = Induction Air Temperature (Temperature of the air leaving the Intercooler)
* OAT = Outside Air Temperature

Look at the arrow in the picture below to see where CDT, IAT, and OAT are presented:

Look for the RED arrow...

Look for the RED arrow…

In a Mirage, Matrix, or Malibu (Continental-powered), outside air enters into the airbox and then gets diverted to one of two turbochargers.  The turbos suck in the air and increase the velocity, pressure, and temperature of the air, jamming the air into the induction system.  We desire the increase in pressure (as it provides pressure for the turbo-charged engine, cabin pressurization, and a few other items), but the increase in temperature and velocity are generally unwelcome.  The sonic nozzles amply handle the excessive velocity delivered to the cabin pressurization, and the intercoolers (if allowed) do a fair job of decreasing the temperature of the air entering the intake manifold.  How well do the turbochargers intercoolers work?  Most PA46-drivers have no idea, and I did not until my experience with Jon.  But, with his monitoring of those temps, a lot became clear.

Low Power, at idle on the ground

Low Power, at idle on the ground

The picture above shows the engine at idle on the ground.  It was a rather hot day at JSO (25C), and the CHT’s began to heat with the minimal air movement and long ground-run (we were training).  Notice the spread of temperatures: OAT = 25C (79F); CDT = 101F; IAT = 92F.  With the engine loafing at idle, the turbochargers were not turning fast, so the temperature increase from the turbos was only 22F (101F-79F), and the intercoolers (with the limited airflow) decreased the temperature only 9F (101F-92F).  Not much happening….until takeoff and climb…

Climb Power, early in the climb

Climb Power, early in the climb

In the climb, the turbos really ramped up the air temperature.  It was early in the climb when this picture was taken, and the climb speed was just starting to enter the “cruise climb” phase.  Notice the CDT = 156F; the IAT is 119F; and the OAT is still 26C (79F).  The turbos are starting to produce a lot of additional heat (an increase in 77F), and the intercoolers are also starting to do their job by cooling the air 37F total degrees.

Climb at FL180

Climb at FL180

As the climb continued, we approached FL180 and the numbers started to get interesting.  Notice the Compressor Discharge Temperature (CDT) rose to 256F, which is a 224F increase in temperature (CDT 256F – OAT 32F).  I find it super-interesting that the turbochargers are capable of ramping the temperature up 224F so quickly.  I checked several trusted sources, and all told me that the turbos turn upwards of 90,000 RPM at high altitude (That’s a BUNCH!). The intercooler is working better too…it dropped the temperature 123F total degrees (CDT 256F – 133 IAT) in the climb.

Cruise at FL210

Cruise at FL210

In cruise at FL210, the compressor is able to increase the temperature a total of 209F from OAT -7C (19F) to 228F CDT.  And, look at the effect of the cold air (OAT 19F) on the intercooler…it was still able to drop the temperature of the pressurized air a total of 122F.

What did I learn from this new-to-me information concerning the turbochargers and intercoolers?  Here’s a list:

  • The Turbochargers are VERY capable of developing super-high temperatures:  The turbos are an integral part of the engine system and do an admirable job of producing pressure and (consequently) temperature.  Ensuring you have strong turbos is critical.  Be sure to have the turbos checked at every annual and have every “change in behavior” associated with the turbos checked by a quality mechanic.
  • The intercoolers work MUCH better with lots of airflow.  At idle on the ground the intercoolers do very little.  In cruise (with lots of airflow) they do a good of cooling the air before it enters the intake manifold.  Cool air entering the engine translates into a cooler running engine.  But…look at the temperature of the air entering the engine during the climb at high altitude…it was the highest of all.  I’m a big proponent of keeping the IAS in the climb above 135 KIAS for prolonged climbs.  This good air movement helps keep the cylinders cool, but it also allows the intercoolers to do their job better too.
  • Instrumentation is available: The EDM 900 is a VERY capable display, adaptable for some pilot-desired information.  I really DON’T like the from-the-factory instrumentation in most Mirage airframes as they only present CHT and TIT.  I’m a HUGE fan of engine monitors in the PA46 airframes as they provide information to the owner/operator that cannot be found anywhere else.  And…information is critical when operating these big pistons.
  • Engine baffling is super-important.  All of the air that enters the front opening of the cowl should be used for cooling…either the cylinders themselves, the oil cooler, accessory items, or the intercoolers.  If the baffling has gaps or holes or is poorly fitted, air will leak through those openings and NOT go through the intercoolers.  To have poorly fitted baffling would be akin to leaving the door to your house open on a hot day, and then complaining about high energy bill and uncomfortable temperature in your house.  I see a wide variance in engine temperatures in the different PA46’s that come to me for training, and I suspect that baffling is the greatest variable.  Here’s a LINK to baffling that Jon recommends and uses on his Mirage.

I hope this helps your understanding!  I found it fascinating.  Thanks Jon!

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Fuel exhaustion engine failure in a Continental PA46

As most know, I love the Continental-Powered Malibu, but today I had my first true engine failure in a Malibu (the other was in a Lycoming-powered Mirage about a decade ago).  Bottom line (to ease the drama of the unknown)…all is well…the airplane is fine…I’m fine…and no insurance company will be contacted.  It was a good ending to a bad flight, but it still scared the crap out of me.  Here’s the story…

It was a short flight in East Texas, but one that was full of challenges.   There were a bunch of showers and small thunderstorms in the area, and I ended up flying below the bases and avoided the shafts.  The light bumps were incessant and there was an occasional bolt of lightning in the distance.

Takeoff was normal, but the climb out was different.  I noticed the CHT on 3 of the cylinders was climbing fast.  I was climbing through about 4,500MSL when I first noticed the higher CHT’s.  The highest CHT was 413F when I started to get serious about discovering what was wrong (and I REALLY try to keep the CHT’s below 375F!).  I next noticed that the full-throttle (35″MP) fuel flow was only 33gph (it’s normally around 37gph). Quickly I decided to reduce the throttle, stay low (below the cloud bases), and see what would happen with a lesser power setting.

I pulled the throttle back to 30″MP, prop to 2400 RPM, and reduced the mixture to 50 degrees LOP.  All of the numbers looked right (CHT came down FAST, OP/OT were in the green, and cruise speed normal).  I continued flying to the airport, but cautiously…with plenty of showers around to divert my attention.

About 5 miles from the airport, the engine coughed noticeably, and then returned to a steady hum.  It sounded like a “Continental Cough”, much like when the mixture is set too lean.  I enriched the mixture slightly and continued the descent to the runway.  As the runway loomed larger and larger in the windscreen, I set up for a normal approach and landing.  At about 50 feet I reduced the throttle to idle near the landing flare and the engine simply died.  I was over the runway, so it was not dramatic, but it did occur.

I started the engine again on the runway during rollout, and it died almost as soon as it started.  I started it again and this time noticed that the engine ran when I pushed the PRIME switch (bringing the fuel pump to HIGH for short periods).  As I taxied off the runway, the engine would die whenever I was not depressing the PRIME switch.  So, I turned the fuel pump switch to LOW.  The engine would not run on LOW.  I pushed the PRIME switch sporadically on the VERY short taxi to the parking spot on the ramp.

As I pulled into the parking spot, the ground-guideman pointed at my nose and gave facial gestures that convinced me he saw something unusual.  I quickly shut the engine down and jumped out of the airplane.  As I moved to the front of the airplane, there was still fuel spilling out of the front.  There were blue streaks along the landing gear, belly, and nose gear doors.  Clearly, there was a big fuel leak.

I had the Malibu towed to the maintenance hangar and with the cowl removed it took only a few seconds to determine the problem.  The main fuel line that passes through the engine baffling has a threaded fitting (some call it a “B” Fitting).  This fitting had blue stains all over it, and it could be turned with the fingers…it was super-loose.  A quick  turn of the fitting with a wrench and the fitting was tight again.

I called some of my favorite PA46 experts and all confirmed the serious threat that befallen me.  As it turned out, the vacuum pump had been replaced recently and the fuel line needed to be removed to access the fuel pump.  In this case, the fuel lines were installed but not torqued correctly.  It was an easy omission, but a potentially deadly omission. (For anyone that is wondering…I did talk with the maintenance facility that replaced the pump, and that mechanic was super-apologetic and used this experience as a teaching tool to shore up the Quality Control at that shop.  And…I assure you that I will NOT make the name of this shop public-domain…it was a simple mistake from a really good shop that is getting better.)

Looking back, I was SUPER-fortunate.  The fuel-starved engine gave up power at an ideal place in flight…had it been any earlier, I would have had an off-airport landing event.  But…and here’s the lesson to be learned…the engine DID give me a clue that something was not right.  Looking back, the high CHT’s and the low climb fuel-flow should have alarmed me greatly.  The cylinders simply did not have the normal amount of fuel, and in climb the additional fuel is used for cooling.  Case in point…if your engine shows any “abnormal behavior”, treat it like there’s a real problem…because there is a problem.

And…one more thing…when I used the PRIME switch and the LOW Pump, I was pressurizing a fuel leak.  One spark, one drop of fuel on the super-hot turbos, just about anything could have started a fire that I would have been pressurized with fuel.  There’s many times in my aviation career that I’ve felt I survived “but by the grace of God”, and this time was one of those times.  This day could have been so much worse!  Had the failure happened in flight, I’m sure I would have reached for the PRIME switch, and that might have started the engine, but I could have experienced an in-flight fire, which is almost always deadly.

I’ll look back on this day with a strong appreciation for a better preflight, a better reaction to when the airplane “whispers” to me that things are “not quite right”, and a hopeful appreciation to our Lord for providing.

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Go-Around in a PA46…

Of all the aviation maneuvers I see during Refresher Training, the one that is butchered the most is the Go-Around (or Missed Approach).  This is disappointing because the Go-Around is so critical.  Everything changes at the Go-Around…the airplane goes from dirty to clean, low-power to high-power, descent to climb, and (often) flight with the autopilot to hand-flying…all at (potentially) 200ft above the ground. If the pilot flies it poorly, there may not be enough altitude to recover.  It is one of the most dangerous phases of flight, and one that every pilot must be able to handle well.

I think most pilots mess up the Go-Around because they don’t have a plan, don’t prepare,  and don’t practice.  My hope with this article is to help you develop your plan, and then I hope that you prepare on every approach (even VFR approaches) and practice (not just during recurrent training!).  Developing your plan depends upon which autopilot you have installed.  But, before we get to the autopilot discussion, let’s talk about the basics of a Go-Around…

There are three fundamental requirements for any Go-Around in any airplane…non-negotiables that MUST be performed. A pilot MUST:
* Pitch Up
* Power Up
* Clean Up

The first two (pitch up, power up) happen at the exact same time, and the last (clean up) happens literally seconds later. If a pilot doesn’t do all three, the safety of the flight will be seriously compromised.

Here’s a discussion of the “Big Three” in a PA46:
Pitch-up: On any PA46, a 7.5 degrees nose-up attitude is almost always the target. This pitch attitude will provide a good angle of climb while not overtly risking a stall.
Power-up: In a piston PA46, the entire quadrant should be moved full-forward (the prop and mixture should already be forward, but the wise pilot will push everything forward with a full hand). There’s no threat of over-torque by pushing the throttle too far forward, and maximum power is needed because there isn’t much additional power available in a piston. In a turbine, more careful power management is required, but more power is available…so, obtaining maximum power is not critical. A pilot can advance the Power Lever to climb power, but not threaten an “over-torque” by staying well under Red Line.   Usually a turbine pilot will get “reasonably close” (within 200 lbs?) of the Torque Limit (Red Line), which provides plenty of climb power and also a safety margin from an over-torque. The Power Lever can be tweaked for more power once the airplane is in a more settled position in the climb, safely away from the ground.
Clean Up: In a PA46, the Landing Gear always comes up first. It could be argued that the flaps should come up first if 36 degrees of flaps are applied, but 36 degrees of flaps should never be applied in a PA46 until the runway environment is in sight and a landing attempt is nearly-assured…and that requires VMC conditions. We are discussing an “instrument go around”, and I do not teach any pilot to put full flaps down on an instrument approach. So…gear first, then flaps…

With those basics out of the way, let’s develop a plan…and the plan for any PA46 depends upon the autopilot installed. I’m going to group the autopilots into 3 groups:

* “Go Around Switch” Autopilots: Those autopilots that have a “Go Around Switch” (GFC700, STEC 1500, and KFC-225)
* Attitude-Based Autopilots: Those autopilots that DON’T have a Go-Around Switch, but DO have the ability to fly a pitch attitude (KFC-150 and DFC90)
* Rate-Based Autopilot: STEC-55X

If you have a “Go-Around Switch” (mounted on the throttle/PL), you have one of the best autopilots in the industry. On all of these autopilots, pressing the Go-Around Switch will do three things:
1.) Disconnect the Autopilot: The FD will still be present, but the Muscle (trim actuation) will NOT be present…you’ll have to fly the airplane…YOU are the “muscle” after pushing the Go-Around Switch. Never forget this…I cannot tell you how many times (in training) the pilot will push the Go Around Switch, apply power and NOT fly the airplane!
2.) Move the Flight Director (FD) to 7.5 degrees nose up: Again, this is the perfect climb attitude, and the smart pilot will “snuggle” the wings into the FD to provide the proper pitch attitude.
3.) Move the Flight Director to “wings level”: Wings level is what is needed for 99.9% of missed approaches. There are a FEW airports that have mountains (or other threats) that demand a turn at missed approach (Aspen, CO and Hot Springs, AR are examples), and the safe pilot will consider those directives listed in the FLIP-IAP Missed Approach Procedures. But, for MOST missed approaches the INITIAL response should always be a wings level attitude.

Plan for “Go Around Switch” Airplanes: If you’ve got a PA46 with a “Go Around Switch”, my Missed Approach Plan would look like this at Decision Height:

* Push the Go Around Switch while advancing the throttle/PL, and manually fly the airplane to the FD (pitch up/wings level). Notice I presented all of this work in one step, for it should all be done in one fluid movement of both hands on the primary flight controls.
* Raise the Landing Gear
* Incrementally raise the flaps
* Confirm a proper positive Rate of Climb (ROC) and proper airspeed
* Turn on the Autopilot (if desired)
* Select the desired ROLL Mode (HDG, NAV/GPSS) as per the missed approach procedures
* Select (and ARM) the altitude desired to level off
* Contact ATC and advise that you are “Missed Approach”
* “Clean up” any cockpit switches (lights, change A/P pitch mode (if desired), etc.)

Attitude-Based Autopilots (KFC-150 and DFC90):  Don’t let the fact that neither of these autopilots have a Go-Around Switch dissuade you from thinking highly of them…these are two FABULOUS autopilots!  The KFC-150 is in all of the early PA46’s (1984 thru 1998) and it is one of the best reasons to buy an early PA46.  The DFC-90 (100% digital) is starting to show up in many Avidyne PA46’s, and it’s a SERIOUS upgrade to the STEC-55X.  I love both of these autopilots, and I love them because they are ATTITUDE-Based!

The KFC-150 and the DFC-90 are “attitude based” autopilots because they utilize the attitude indication from the attitude indicator (KI256, KI300, G500, Aspen, or Avidyne display) and have the ability to hold a pitch attitude.  I’m going to bet right now that 90% of PA46 pilots (even the ones that have flown these autopilots for years) do not know that they will hold a pitch attitude!  In fact, they will DEFAULT to pitch attitude when no other command is given.  For instance, if you simply push the FD button, the FD will pop up on the attitude indicator.  What pitch mode is it displaying?  You got it…the pitch attitude of the airplane when the FD button is depressed.  Guess what happens if you push only the HDG button?  Right again…the FD will provide a roll indication to hold a heading, but it will default to ATTITUDE Mode until some other mode is pressed (ALT, VS, GS…or IAS for the DFC90). And…here’s the good news for anyone wanting to do a missed approach…if the pilot pushes the CWS (Control Wheel Steering) button (on the yoke) with the Autopilot either OFF or in APR Mode, the FD will command the pilot to Wings-Level for ROLL and ATTITUDE Hold for pitch.  The FD will command whatever pitch attitude the airplane is at when the CWS is RELEASED.  So, the pilot can fly the missed approach (Pitch Up, Power Up, Clean Up), press and hold the CWS until 7.5 degrees pitch up is reached, release the CWS, and then turn on the Autopilot.

Go Around Plan for Attitude-Based Autopilots:  If you’ve got a KFC-150 or a DFC90, I think your Missed Approach Plan should look like this:

* Advance the throttle/PL to climb power and Push the CWS Button while manually flying the airplane (and FD) to 7.5 degrees nose up, then release the CWS.  Notice I presented all of this work in one step, for it should all be done in one fluid movement of both hands on the primary flight controls.
* Raise the Landing Gear
* Incrementally raise the flaps
* Confirm a proper positive Rate of Climb (ROC) and proper airspeed
* Turn on the Autopilot (if desired)
* Select the desired ROLL Mode (HDG, NAV/GPSS) as per the missed approach procedures
* Select (and ARM) the altitude desired to level off
* Contact ATC and advise that you are “Missed Approach”
* “Clean up” any cockpit switches (lights, change A/P pitch mode (if desired), etc.)

STEC-55X: If you have an STEC-55X Autopilot, then you have (arguably) the least of the prominent PA46 autopilots, but it is still an acceptable autopilot.  It is a Rate-Based autopilot…and this means that it uses the turn coordinator for ROLL inputs and uses only the Vertical Speed, Altitude, or Glide Slope for PITCH inputs.  So, it will not hold a 7.5 degrees nose up attitude (or any attitude), but it will only hold a Rate of Climb during a Missed Approach.  When the CWS Button is pushed, it reverts to V/S Mode for Pitch.  At Decision Height, a pilot can push the CWS, fly the airplane to 7.5 degrees nose-up, and then check the V/S indication on the autopilot display to ensure the desired V/S is being commanded/flown.

There’s another issue with the STEC-55X…there’s a panel-mounted 3-position switch that has these positions:

UP = Autopilot ON
Middle = FD only ON
Down = Autopilot and FD OFF.

So, if the autopilot is ON (switch in the UP position) on an approach (and A/P is flying the airplane), the pilot must either push the RED Button on the yoke (which turns OFF the FD and A/P) or push the panel-mounted button to the MIDDLE (FD only) or DOWN position (A/P and FD OFF) in order to land the airplane.

And…there’s yet another issue with the STEC-55X…when the CWS is pushed, in the roll axis the A/P automatically reverts to “Bank Mode”.  In this mode, the autopilot will hold whatever bank angle the airplane had when the CWS Button is RELEASED.  So, if the pilot pushes the CWS Button and flies the airplane poorly (maybe with a bank close to the ground), when the CWS is released the A/P will fly that bank…and a bank at low-altitude can be deadly.

If the pilot elects to use the RED button while descending on the glide slope, the A/P and FD will turn OFF, but the second the pilot pushes (and releases) the CWS Button, the A/P will come back ON.  Again, it is absolutely critical that the pilot fly the airplane PERFECTLY on the Missed Approach!

For this reason, I teach pilots to turn the panel-mounted switch to the MIDDLE position (FD-only ON) while still descending on the glideslope (and hand-fly the airplane).  When it is time for the Go Around, the pilot must hand-fly the initial stages of the Go-Around, cross-check the instruments, and then re-engage the autopilot.  Confusing?  Exactly…that’s one reason why the STEC-55X is NOT my favorite autopilot.

Go Around Plan for the STEC-55X Autopilot:  If you’ve got an STEC-55X, I think your Missed Approach Plan should look like this:

* Switch OFF the Autopilot while descending on the glideslope to the MIDDLE position (FD still ON) and hand-fly the airplane; then…at the Missed Approach point…
* Advance the throttle/PL to climb power and Push the CWS Button while manually flying the airplane (and FD) to 7.5 degrees nose up, then release the CWS. Notice I presented all of this work in one step, for it should all be done in one fluid movement of both hands on the primary flight controls.
* Raise the Landing Gear
* Incrementally raise the flaps
* Confirm a proper positive Rate of Climb (ROC) and proper airspeed; adjust the V/S with either the CWS or by adjusting the V/S on the autopilot face
* Select the desired ROLL Mode (HDG, NAV/GPSS) as per the missed approach procedures
* Turn on the Autopilot by moving the Panel-mounted switch to the UP position
* Select (and ARM) the altitude desired to level off
* Contact ATC and advise that you are “Missed Approach”
* “Clean up” any cockpit switches (lights, etc.)

After originally posting this Article, I received an email from a client that felt I was unjustifiably harsh on the STEC-55X Autopilot, and offered this simpler STEC-55X Missed Approach Plan:

* Press disconnect at DH
* Power / Attitude / Positive rate / Gear up on RWY heading
* Press HDG then VS…Autopilot is now engaged and vertical speed captured on last actual vertical speed
* Clean up flaps
* Fly the missed approach with the HDG Mode or change to NAV Mode

While I have a couple of “minor dislikes” with this plan, it is reasonably solid and shows a good understanding of the idiosyncrasies of the STEC-55X.  I present this plan to highlight the fact that not all plans are identical.  There are many ways to safely pilot the airplane through a missed approach.

As you can see, each PA46 pilot needs a plan based upon the autopilot.  The “Plans” I present in this Article describe what I would use for a normal ILS or WAAS approach, but they are not the only plan that would work.  A pilot must know the modes of the autopilot installed and formulate a plan that works for the approach being flown based on the installed equipment.  There is no “standardized” way of doing the missed approach, but each pilot should develop a plan that “works” and practice that plan.

A wise pilot will “plan for the missed approach”, but hope to land the airplane normally. Unfortunately, most pilots “plan for a landing” and are unprepared for the missed approach if it is required to be flown.  Developing a plan, preparing the cockpit for that plan, and practicing the plan are the keys to success for any missed approach.

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PA46 Buyer Questionnaire

This QuestionnairCaseyAviationD15aR02bP01ZL-Tyler2be (either Buyer Questionaire-Turbine PA46 or Buyer Questionaire-Piston PA46) is what I use when a client collaborates with Casey Aviation for “Buyer Agent Services”. It helps me narrow down the specific needs of the client, but it also helps the client  firm in his/her mind which airplane is right.  I believe an informed buyer will make the best buy decision, so I work to educate the buyer so he/she can make the right buy decision (I don’t ever make the buy decision…I merely educate and nudge in the right direction).  If you are thinking of buying a PA46, or upgrading within the PA46 family, this questionnaire might help.

Obviously, some of the questions appear unrelated or weird, but I assure you that the question has a real connection to the PA46 and the answer helps me direct a client to a better decision.

Respond to the questionnaire and send it in to me…I bet it’ll help you make a better purchase decision!

 

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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.

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