Test flight of the new Piper M600

The following article is an unredacted version of a flight review conducted on behalf of AOPA Australia:

It’s been a little while since Piper brought out a completely new product. There may be good reason for this – those keeping up to date on rumours may have heard about piper working on a Piper Jet program: The PA-47 Altair. Work had indeed been done on such a new aircraft; in fact a single prototype actually flew - but the program was ultimately shelved. Instead, following industry demand studies, the Piper team elected to re-allocate their resources on a follow on aircraft for the Piper M series. A new aircraft would be needed which would keep the M series alive, but still stay ahead of the market in terms of increased usefull loads, cruise speeds, and climb performance. The Piper M600 was born out of the ashes of the Altair project, and I'm glad it did. Jacqueline Carlon, sales director for Piper aircraft: „The Altair project wasn't wasted. A lot of what we learned and a lot of the aircraft systems went into the M600.“

The Piper team knew that the wing on the previous M series aircraft, from the piston M350 to the Turbine M500, had been stretched to it's limits over the course of the family’s design iterations. An entirely new wing would be needed to allow the aircraft to perform the duties required. The final wing would turn out to be larger and use an entirely different profile... Although the dimensions of the fuselage would be identical to previous PA-46 series aircraft, much would change under the skin. New stringers would have to be added in between the main ribs to allow for the higher loads expected and the landing gear would move forward. The single outflow valves controlling cabin differential pressure would no longer be barometrically sensed and mechanically operated, but replaced with two independent digitally controlled, monitored and operated outflow valves. This would allow a whole new level in pressurization automation.

The powerplant chosen for the M600 was the PT6A-42A flat rated at 600 shp, which would give a fully loaded 6000 Lbs aircraft a climb rate in excess of 1600ft per minute. The performance increase over the original M500 is hence in the order of 20% for both MTOW and available power. Time to cruise height of Flight Level 280 would be max 16 minutes at MTOW. An Empty Weight of 3,650 lbs gives a significant Usefull Load of 2400 lbs. As my demo pilot would explain to me later; „you almost always cruise at max FL in this aircraft. Time to height is so short that it simply doesn’t make any sense to not do so on any flight exceeding 40 minutes…“

There is always a slight sense of apprehension leading up to a flight assessment of a brand new aircraft with a team you haven’t worked with. Sure, anyone can sit in an aircraft and follow along for a normal flight, but a certain level of chemistry is required between a demo pilot and the assessment pilot: Although you have never have flown together, the intent of the operation is still that you work as a team to explore some of the edges of the aircraft flight envelope. Only when this functions properly will a reader and perhaps future customer be able to gain a better understanding of how this particular machine behaves.

My demo pilot Martin Rychtalik greeted me for a pre-brief at their demo stand at Aero Expo. He shook my hand, revealing a braced up pinky on his right hand bent out at an awkward angle. I asked him about it.

„I broke it riding motorbikes a few days back“ he answered matter of factly.

So I knew we were going to get along just fine…

We discussed the flight, the flight plan to file, the images we wanted to get, and the aircraft limits we wanted to explore. Considering the Australian market with potential short rough runway operations, I mentioned that I'd like to see a performance takeoff: Brakes held, spin up to full power, and release.

„Unfortunately we can't do that. The engine will drag the aircraft with the wheels locked…“

Martin is based with the OK Aviation; a European Piper dealer just South of Prague. They currently hold the only EASA type training certification for the M600 on the continent. Martin was also the pilot who flew this particular aircraft from the US to Europe. It's the first M600 to leave the US, and given the significantly higher cruise range of the aircraft relative to previous M generations, the team made the notable decision to avoid landing fees across Greenland and Iceland and instead cross the Atlantic direct, coming over the Azores. You can't install ferry tanks in pressurized aircraft - it came across stock standard as is.

There are some significant differences in how regulators see the M600. Under FAA, the M600 is just another M class aircraft, which means that pilots upgrading from an M350 or M500 will (legally) only require differences training. Potential purchasers under EASA registrations however should be aware that all turbines, hence including the M600, are considered a separate type. As such, to be flown with a European registration the aircraft would require the full minimum 10 hrs training as legally mandated for any turbine typerating. It's not yet clear how the M600 will be categorized under Australian CASA regulations, but Jacqueline imagines it will be closer to FAA requirements than EASA.

„We can do quite a bit of the training in the certified simulator we have, but in all honesty, you really do want to spend some time doing landings in the airplane, as does feel much heavier than previous models and takes some getting used to.“

In any case it may not be all that relevant in the end anyway: Each purchase includes a week long aircraft specific pilot training program, conducted on the purchasers airplane if so required.

The next morning I met Martin at the airplane on the other side of the airfield. Taking a seat in the cockpit, I noted the Hobbs meter: 25 hrs. During the course of the assessment we would add around ten percent to the aircraft’s total time. AOPA Australia was given first flight subsequent to the cross Atlantic delivery. It was clear that Piper sees value for the M600 on the Australian market.

The target market for the M600 is the owner-operator, although a recent change in legislation allowing single engine IFR turbine commercial operations is expected to cause some level of change to this. Currently over 95% of previous generation aircraft are flying as owner operators and it’s expected that the aircraft will be the first turbine upgrade for many purchasers entering this performance class. With this target reader in mind I decided that I would conduct the test-flight from the point of view of a pilot who had never flown a turbine aircraft nor ever had to deal with a pressurization system before. It turned out that this would work quite well since when last I checked my logbook, I had never flown a turbine aircraft or had to deal with a pressurization system before…

It would not be an issue, and we would not lose valuable instructional time on it during the flight. The engine start process is automatically initiated by a single button push. All the pilot has to do is add fuel with the condition lever once the RPM comes up and monitor the inter turbine temperature. If by black magic a hot start does happen to occur, the pilot cuts the fuel and can try again in 30 seconds.

The pressurization system is just as simple. You close the main door, set outflow valves to „normal“, and the pressurization selector to „normal“. The computer does the rest. The cabin pressure differential will gradually climb untill reaching a maximum differential pressure of 5.6 psi. This corresponds roughly to a cabin altitude of just under 10,000ft at the maximum allowable Flight Level of FL300. As aircraft in this category are not RVSM, airspace clearances will generally keep you at FL280 anyway. On descent the reverse occurs, and the computer will „land“ the cabin and automatically equalize pressure before the aircraft touches down. Should by some error the cabin still be pressurized, a dump would be activated on ground contact equalizing pressure. – Considering the maximum cabin altitude of 10,000 ft (which is very unlikely), this would not do more than pop your ears.

Let’s get back to our flight assessment…

Even at idle power the taxiing aircraft will continue to accelerate unacceptably. To slow the aircraft we don't touch brakes, but instead lift the single power lever up over a detent into the Beta (reverse thrust) range. A squat switch prevents activation of Beta when in flight. Already on the ground I can feel how heavy the nosewheel steering is. It simply is a heavier aircraft in controls, even compared to the twin engine and slightly larger Piper Navajo which I've flown in skydive ops. Differential braking is not needed. Visibility over the nose and in all directions is excellent, even though most operators will fly IFR. The new Garmin G3000 triple PFD/MFD integration plus dual touch screen input pads is astonishing and beautifull, and would deserve an entire article in itself. Martin explains it requires some schooling, but no task is more than two button presses deep. Everything is interchangeable and customizeable. Even while we taxi he seamlessly brings up various pages, approach plates, overlays, TCAS targets, and weather radar. I see panels going left, right, up, down, and everywhere he feels like placing them at any point. He shows me a „Safe Taxi“ feature, which positions the aircraft exactly on an airport map, allowing the pilot to orient himself even in poor visibility. (It is not meant as a sole means of on ground navigation).

Martin quickly notes with annoyance that during the previous few days on static display, cockpit visitors had moved around his preferred custom screen set ups. He grumbles and starts sliding away at the touch pads. Screens with runway, instrument departure, and aircraft information start flying around everywhere across the three displays… Even for a Gen Y kid like me used to smartphones and tablets it seemed a little overwhelming at first - but I quickly note Martin only needed a limited number of inputs to gain all the customization he required.

The taxiway is clogged with GA aircraft leaving the Aero Expo, with post startup departure delay approaching 30 minutes. As an IFR departure however we're conveniently routed around the mess for a priority lineup on the undershoot at Alpha. There would have been a lot of annoyed pilots looking at bravo… Martin says it makes little sense to fly this aircraft VFR. Although entirely capable, pilots upgrading on to the M600 will already be IFR and properly schooled in order to take full advantage of the cruise performance of the airplane at height. It's the same reason he snickers at the bright blue „Facebook“ button built into the dash. Labeled „Autopilot Level mode“ it's an emergency safety gimmick Piper likes to market with. Martin only needs it when he's busy uploading selfies to Facebook.

There are three flap settings. „Up“, „Takeoff“, and „Landing“. Three guesses as to what we had set…

After clearance I advance the single power lever to the stop. Prop pitch control is automatic and integrated. True to Martin’s predictions the aircraft skips on the brakes before the turbine fully spins up; we have to release. Acceleration is immediate and smooth. The lack of vibration is quite novel to a piston pilot. Alternate airspeeds are cross-checked at 60, rotation at 85kts. Initial Vx climb out at 95 seemed impressive at first – but subsequent acceleration to Vy even more so… We're loaded somewhere under 5000 Lbs, but once gear and flaps are up and we've stabilized the airplane at 122 kts best rate, I get a chance to look at the VSI tape. We’re exceeding 2700 fpm climb... We would maintain that rate until we re-settle for a cruise climb speed around 160kts from 10,000ft. We continue at a measly 2300 fpm. ATC doesn't play along, and it takes us several level steps to get to cruise height at FL280. It doesn't matter - Martin said 12 minutes to height when light, 16 when MTOW. I saw the numbers. I believe him...

Below FL230 it was possible to maintain full power on the engine, but as we cross this level power output to the engine had to be steadily reduced to keep turbine temperatures off the red line. Another interesting thing happens around FL240 – as the density of the air reduces this is approximately the flight level at which the maximum allowable airspeed becomes limited not by KIAS but by Mach. A whopping 0.55. This is nothing to worry about, but for the pilot a little caution is required above this point: The powerfull PT6 up front will now be able to pull the aircraft into its redlines for both airspeed and turbine temperatures.

Indicated cruise TAS is as advertised: I'm seeing level speeds between 275 and 280 kts. At this power setting the book range is listed as 1,085 nm with reserves. A reduction in cruise speeds will allow a range increase up to 1,484 nm – unmatched in its class. The Piper team was quite helpfull, but not nice enough to let me test the claimed endurance limits. We'll just have to believe them when they say they crossed the Atlantic.

At altitude I get a chance to play with the options on the weather radar. It can be overlaid on the HSI, including traffic from ADSB if needed for a full overview. It's a very cool feature… Furthermore, a downward tilting of the radar sweep allows for an overview of terrain – clearly showing the Alpine peaks surrounding us way below North of Lake Konstanz.

Any aircraft designed to operate above FL250 requires quick-donning crew oxygen masks, and the M600 is no exception. Oxygen masks are stowed within immediate reach and operable with a single hand. Time of Usefull consciousness at FL300 in the event of a depressurization is commonly accepted as being between 1-3 minutes. In the event of a slow depressurization, the aircraft pressurization system will issue warnings as the cabin altitude climbs. Should the cabin altitude exceed 10,000 ft, a caution will sound and display on the Garmin G3000 PFD. If the cabin altitude continues to climb above 12,000 ft, a warning will activate. Additionally, on flights above FL150, the flight computer will sense activity from the pilot. If the pilot has not made inputs for a certain period of time, missing several timed prompts based on altitude will engage autopilot hypoxia protection and automatically fly the aircraft down to a safe Flight Level allowing the pilot to recover.

Since I'm not too fussed about normal operation of the aircraft (I believe a cruise descent is possible), I requested Martin to show me an emergency Depress event. Some negotiating with ATC was required in busy European airspace, but we received a clearance for unrestricted descent. Perhaps counter-intuitively, the first thing Martin does on noting an emergency is keep the nose up after reducing power. I remember this part from Skydive operations in the Navajo though – Martin is reducing airspeed down to the Gear Extension speed. It's not a big restriction: As soon as we hit 170 kts indicated the gear comes down and the nose is lowered. In the Navajo we used to set one stage of flaps as well, but Martin explains the flap operating arc is too far out of reach at 147 KIAS. At just under 170 kts with gear down the descent rate stabilizes at just under 5000 fpm. It would take about four minutes to get below 10,000 ft, or three below the critical 14,000. The descent is stable and unconcerning in any manner. At just over 10,000 ft Martin dumps the cabin pressure for demonstration purposes. The result is unspectacular – it gets cold, our ears pop, and the cabin altitude warning system functions as designed when it reaches 10,000 ft. Re-pressurizing the cabin happens at the flick of a switch.

The airplane has an independent envelope protection system which functions independently but couples through the autopilot servos to counter roll beyond a nominal angle of bank. The countering force is increased beyond a second threshold. Overspeed and underspeed (stall) protections are linked to the pitch axis. The power setting is not incorporated. The envelope protection can be over-powered by the pilot or switched off if specifically required. This will allow stalling the aircraft or exceeding protection limits as required for demonstration purposes, or perhaps when flying specific approaches into airfields requiring solid maneuvering. The stall behaviour of the aircraft is unspectacular and typical Piper friendly, with a slight lowering of the nose allowing reattachment of airflow.

In flight it's noteworthy again how heavy the airplane feels during control inputs. Not uncomfortably so, mind you – it's more of a luxurious feel slowing everything down and befitting of the airplane's internal atmosphere. It seems the aircraft's spirit is larger than the airframe which contains it. The ailerons are relatively small, with the majority of the trailing edge of the wing being taken up by the large flap sections. They will allow an airspeed reduction down to 62 KIAS in the landing configuration at MTOW, with a clean stall speed of of 73 KIAS.

We went for circuit excercises at another local airfield – Friedrichshafen was still bustling with exit traffic and would restrict us too much. The heaviness of the pitch control would catch me off guard during my first landing flare. Jackie had said it would... Subsequent to that everything normalized. A target speed of 95 knots on final worked well, and the following landings were just fine, both with full flaps and flapless. A slight amount of power is kept in during the flare; both to soften the landing and to reduce spool up time in case of a go-around. Even under a simulated engine failure the aircraft behaves well, comfortably gliding at 115 kts and reaching the runway from downwind with room to spare. The dual-setting flap switch means that the difference between the „Take off“ flap setting and the „Landing“ flap setting is quite significant: from 15 to 75 degrees. The last stage of flap brings in a lot of drag and pitches the nose down. A re-trimming of the aircraft and slight addition of power is needed on for a normal approach. Martin clarifies that he prefers to set the aircraft up early on long final. There is no need to throwing switches and changing configuration coming over the threshold. For roll-yaw coordination a rudder-aileron linkage assists the pilot; this is a friendly airplane anyone can learn to fly. The Garmin display is also very helpfull in maintaining orientation, especially at a new airfield. Remember circuits are at 1500ft AGL now and wider – you're not flying among the pistons anymore…

The handbook shows a Sea Level ISA 4000 Lbs takeoff ground roll at just under 400m. At MTOW this increases to 585m. The numbers for an ISA +20 day (think Australia at 35 deg C) are 450m empty and 662 MTOW. Thou shalt add another 480m and 810m on top of that respectively to get over a 50ft obstacle.

An emergency gear extension caps off the excercises. The gravity drop is a familiar and reliable extension method to anyone who's flown retractable Pipers, and here as well it works without hickups. The gear locks down instantly without requiring so much as a wiggle on the rudder. Unlike some other aircraft, re-engagement of the hydraulic system is unproblematic and can be done from inside the cockpit in flight. It's time to head home…

The M600 received it's FAA certification in June last year.

„I mean, are you kidding?“ Jackie rolls her eyes.

„We had to wait for winter and then go looking for ice up in Canada“

The M600 is fully equipped for Flight Into Known Icing (FIKI). De-icing boots, prop, pitot, and windshield heating come standard, but certification for this is expected in the weeks of writing this article. (Most likely before publication).

Another point of concern I had for the Australian pilot was the handbook limitation on operation from paved runways only. This will also be lifted, I'm assured. Piper first focuses on getting the airplane in the air, then as with previous M class aircraft the unpaved runway capability is just a certification check which is tagged on later. By the time the aircraft reaches Australia, it should be completed. Previous operators of PT6 engined aircraft will be aware that the engine uses a centripetal particle separator to prevent solids ingested in the intake from entering the turbine. Unlike other PT6 engine installations though, the M600 doesn't have a particle separator door. The particle separator still exists, but the intake has simply been made so large as to accommodate sufficient throughput to feed both the particle separator and the intake simultaneously with minimal loss of power. It's simply left permanently active, with one less thing for the pilot to worry about.

For gravel strips I had some concerns about the tip clearances on the five blade Hartzell prop upgrade, but these questions are also alleviated by my demo pilot. The difference in tip clearance between the four- and the five blade is negligible, and Piper fully expects the uptake on the five bladed prop to reach 100%. The main improvement seems to be in external noise, although certain performance measures improve by as much as 5%. Plus, it just looks better...

Piper knows where they stand amongst their competition and talks about it freely.

Jackie:

„If you're looking at the M600 then you're looking at TBM and the PC-12 and the Mustang“

Really? I was skeptical... The PC-12 or the Mustang for an initial turbine?

Well yes... And well... No... If you look at the acquisition costs, then looking at the price range of the TBM 930 at just over USD 4 Mio, the PC-12NG simply gives you much more payload for a relatively small jump in price at under USD 5 Mio – at somewhat higher operating costs. If you need to get places fast, a used Citation Mustang will set you back around USD 3 Mio – but for that you'll need a multi engine jet rating and be willing to deal with the twin turbine costs and runway limitations.

Piper knows that TBM cruises faster than the M600. They also know that TBM uses a higher power output version of the PT6 engine burning almost 40% more fuel.

„We beat them all on value“

She's right. I checked.

The factory base price for the M600 is USD 2.89 Mio. An EXP "Expression" package allows for custom paintjob, customized interior, and logos or nameplates placarded inside the airplane, raising the price to around 3.08. In terms of operating costs, independent statistics from Conklin and deDecker show that the M600 is the best value initial turbine in this comparison; both in acquisition and in operation, with operating costs roughly two-thirds that of the nearest competitor. Also noteworthy is that as part of the introduction of the M600, Piper lowered the base price for the original M500 with an MTOW of 5,092 Lbs from USD 2.2 Mio down to 1.9 Mio. But after reading this article, I don't think you want the M500. You want the M600.

With a naughty smile Jackie couldn't resist just one last jab:

„It seems there's a standard door height for personal hangars. We found out our tail is two inches below it. It turned out TBM is two inches too tall...“