Flight Test: Piper M600
Would the M600 prove too similar to the M500? Not a bit of it! With improvements including 100 more horses, masses more fuel, a new wing, greater load, and fabulous avionics, this is definitely a step up
Wih more horses, way more fuel and excellent avionics, the M600 is a very different beast to the M500
Imust admit that I approached this flight test with some trepidation. Having been the first journalist to fly the M500, I was a little worried that the 600 might be a bit too similar to justify a full flight test report. It is still a PA-46 after all, and shares the same Type Certificate as the Matrix, Meridian and Mirage. However, when I express my concern to Piper’s Thomas Nielsen as we walk out on a late spring day at OxfordLondon airport, he soon puts my mind at ease. “I don’t think you need to worry about that,” he grins “this is a very different machine!” As we draw closer, I can see several differences already. For example, even though the 2017 brochure clearly shows a four-blade propeller, this aircraft has a five-blade Hartzell ‘Scimitar’ unit. “That’s correct,” confirms Thomas, “Piper is constantly refining and improving the design−the Hartzell five-blade composite prop was certified in March. It just gets better and better.” The engine is the same as the M500’s, a Pratt & Whitney Canada PT6A-42A, but it’s now flat-rated to 600shp (100shp more than the M500).
This is still 250shp less than it is capable of at sea level, ensuring it can produce its full rated power right up to around 23,000 feet.
A neat touch is the sight tube for checking the oil quantity. The PT-6 is renowned for consuming very little oil, and Thomas jokes that most of the oil used is that wiped off the dipstick.
A clever feature of both the 500 and 600 is an intriguing door behind the NACA ducts in the lower half of the cowl, which Thomas explains functions as an inertial separator. On some PT-6 installations the inertial separator is manually selected from the cockpit but this is a much simpler installation. The two wing tanks have a combined capacity of 984 litres, which is a huge (more than 50%) increase on the 644 carried by the M500. Although from a distance the 600 does look a lot like the 500, I start to realise it is a very different− and much more capable−machine.
The wing has changed significantly. In fact, it’s a clean-sheet design, with more area than the M500’s, new single-slotted flaps and redesigned ailerons. It’s also considerably stronger, allowing an increase in the Vmo from 188 to 250kt, and can carry an extra 454kg. Thomas is extremely knowledgeable about the M600, and explains that the inboard spars are machined while the inboard skins are ‘chem-milled’. More obvious improvements are that the Garmin GWX weather radar is faired into the starboard wing’s leading edge (on the 500 it’s carried in a pod beneath the wing), and that the wingtips are stylishly upswept. As you’d expect, increasing the maximum weight by twenty per cent obviously required the wide-track but relatively short wheelbase undercarriage to be tweaked, and the main legs have been moved slightly aft. The nosewheel strut retracts aft and carries a large LED landing light (from S/N36 onwards there will be a landing light on each of the main legs, which retract
inwards). Powerful LED navigation lights are mounted just inboard of each wingtip.
The FIKI (Flight Into Known Icing) package consists of pneumatic rubber boots on the leading edges of the wings, fin and tailplane; de-ice for the prop and a heated pilot’s windscreen. Down at the tail I am intrigued by what appears to be a tiny stub wing protruding from the fuselage just in front of the tailplane. Apparently, this directs a flow of air onto the rudder to aid in spin recovery. Thomas encourages me to move the elevator, which is incredibly heavy (more on that subject later).
By now I’m eager to hop into the pilot’s seat and start the engine, but Thomas insists that I take a good look at the cabin first. Access to it is via a clamshell door on the port side aft of the wing (the lower half also functions as an airstair) and I see straightaway that a lot of thought has gone into styling and passenger comfort. The test aircraft’s interior features Piper’s EXP (Expression package), which can be customised in myriad ways. There are
plenty of USB ports for passengers to charge their devices, and they can make phone calls or send and receive texts and emails through the G3000 via the Iridium GSR 56 system. The black leather seats with red stitching nicely complement the carbon fibre table and side panels. It’s all extremely smart. One feature I greatly appreciate−as I become both older and fatter−is that the front seatbacks fold flat so access to the pilot’s seat is better than on some larger aircraft I’ve flown.
Thus far I hadn’t been able to fault any aspect of the aircraft, so I was both disappointed (and slightly relieved) when I finally found something to complain about! The pilot’s restraint system is only a three-point inertia reel arrangement, and when you’re zipping along at 300mph and suddenly run into unexpected turbulence it simply isn’t adequate. There’s a good reason why Boeing and Airbus put four-point harnesses into the pilots’ seats of their aircraft.
Staying with airliners, if it weren’t for the five-blade prop outside the windshield you’d swear you were in a 400-seat jetliner. The avionics package is Garmin’s incredible G3000, and the instrument panel is filled with two twelve-inch PFDS, a centrally located twelve-inch MFD and an Aspen Avionics EFD-1000 ‘Evolution’ standby instrument to the left of the pilot’s PFD.
The alphanumeric keypad fitted to the 500 has been deleted, and everything is now done via the dual GTC 570 digital touchscreens below the MFD. The interface is very intuitive (the screens actually resemble smartphone screens), and when I remark to Thomas that I’d once had difficulty operating a touchscreen in turbulence, he points to the small bar beneath the GTC 570s, which you can use to hook your thumb around. Beneath the GTC 570s there’s a small pedestal with the undercarriage selector to its left and the flap switch on the right.
The pedestal carries the big silver T-handled power control and red-topped fuel condition lever (which strongly resembles a mixture control), elevator trim wheel, rocker switch for rudder trim, friction lock and emergency fuel control. There is no prop lever as the prop is automatically governed at 2,000rpm, while lifting the power control up and back over a gate selects ‘Beta’ (which flattens the prop pitch, producing less thrust so you don’t have to ride the brakes) and then ‘reverse’. Most of the electrical switches are in a neat overhead panel, which make an already uncluttered instrument panel even clearer.
I turn on the battery and Thomas introduces me to the G3000. I’ve always thought the G1000 to be a fantastic piece of kit but the G3000 has taken the science of avionics to another level entirely. It has all the features we’ve become used to over the years, but accessing them has become even easier due to the shallow menu structure. As with all things digital, you do
need to sit down with the book to get the best out of it, but it is quite intuitive. It’s also extraordinarily powerful.
Two features I really like are that the screens of the PFD and MFD can be split 60/40, meaning (for example) that you can bring up an approach plate while retaining your essential flight information; and that, as well as displaying the frequency selected on the COM, it also shows the name of the station. This must be a tremendous asset, particularly when dealing with controllers whose accents can be somewhat difficult to interpret (or if you’ve simply forgotten whether the last person you spoke to was Approach or Tower!) I also like the ‘Enhanced Map HSI’, which allows additional information (such as terrain, airspace or weather radar) to be overlaid on the HSI display. By enabling even more information to be displayed within the pilot’s primary instrument scan, situational awareness is taken to a new level.
And speaking of level, the 600 retains the same protections provided by the GFC 700 autopilot’s enhanced automatic flight control system (see ‘ESP and USP’ below) and also incorporates a hypoxia recognition system with integrated automatic descent mode. A full explanation of this very clever system is beyond the scope of this article but, basically, if the autopilot is engaged above 14,900ft, and there’s a loss of cabin pressure and no interaction detected from the pilot within a specific time frame, the system issues multiple prompts. If these prompts are ignored the system assumes the pilot has become incapacitated and the aircraft automatically descends to below 12,500ft. The G3000 really is a fully integrated digital avionics suite that incorporates every aspect of operating a single engine turboprop. Even the pressurisation system is fully automatic.
Easy to operate
Starting the engine confirmed that Piper’s engineers have done a great job of making the 600 very easy to operate. There are no fuel valves in the cockpit−both tanks are permanently on and feed simultaneously; the big red handle at the base of the pedestal is the emergency shut-off. To start, simply press and hold the start button for one second, and when the Ng stabilises at around 15% move the fuel condition lever to run and then monitor the inter-turbine temperature (ITT) gauge; the temperature stabilises well below the red limit. After just a couple more post-start checks we’re ready to roll.
Even with the power lever on the idle stop the 600 wants to taxi faster than I do, so to avoid constantly riding the brakes I pull the power lever back into Beta. With everything checked−there really isn’t that much to do−and trims and flaps set, I line up, stand on the brakes and bring the power up to 1,500ft-lb on the torque gauge. (Personally, I’d prefer the power was presented as a percentage. During the two weeks prior to flying the M600 I’d flown singles and twins, pistons and turbines, nosewheels and taildraggers, gliders and motorgliders−so I need everything as simple as possible! But, to be fair, if you only flew 600s I’m sure you’d soon learn the numbers, and Thomas later explained that using torque in foot-pounds allows the power to be set more accurately at sea level.)
As mentioned earlier, although the 600 is 454kg heavier than the 500, it does have 100 more horses. Today, with only
Thomas and me on board, and around half fuel, we’re possibly lighter than a fully laden 500 but still have the extra ponies at our disposal! Ambient conditions are close to ISA (airport elevation is only 270ft, with an OAT of 17°C) and there’s a slight crosswind from starboard. The engine almost groans as the big prop bites into the air, and the 85kt Vr doesn’t take long to attain. In fact, the takeoff conversation is basically very short: “airspeed alive, Vr, positive rate−gear up, flaps up”. The POH claims barely 800 metres is needed to clear a 50ft obstacle at MTOW and I can well believe it.
The Oxford controller initially keeps us at 2,000ft, and I’m pretty busy with power and trim until we’re cleared to climb up to our operating altitude of 10,000ft. Of course, in the real world of complicated airspace, lots of traffic and inclement weather I’d simply have engaged the autopilot at 500ft, but where’s the fun in that?
Having been cleared to climb I ease the power lever forward, then remember the electric rudder trim. With 600shp rotating five big blades at 2,000rpm there’s no shortage of P-factor, precession and torque, and whenever either the airspeed or power changes the rudder trim needs a couple of clicks to keep the pedal forces neutral and the slip indicator centred (although I do feel the Garmin’s slip indicator is overly sensitive). As we climb I try a few turns and sense almost immediately that the handling seems slightly heavier than the 500 (although with some airflow over the elevator now it was much lighter), and that it also seems considerably more stable. Both of those traits are definite improvements (it is after all, a travelling aeroplane) while the overall control harmony and relationship between control and stability are exactly how they should be for an aircraft of this class. Piper has built a lot of aeroplanes over the last eighty years, and it shows. Slowing down for a look at the stall is interesting. Of course there are both
The extra horses have greatly improved both the rate of climb and cruise speed
audible and visual stall warnings, but you may recall that I found the elevator to be very heavy on the ground? Well, as the IAS dips below about 65kt it gets really heavy. You can’t trim the forces out−it is an excellent natural warning that you’re simply flying too slowly. Due to time constraints I don’t get a chance to examine the cruise performance at the optimum operating altitudes (typically around FL250 to FL280). Although it has a service ceiling of 30,000ft it is NON-RVSM, and therefore certified up to FL280.
Thomas had flown it over from Florida, and assured me that the extra horses have greatly improved both the rate of climb and maximum cruise speed, while the new wing has enhanced performance at altitude. During the trip from Vero Beach he’d typically cruised at 28,000ft and 182kt IAS, for a TAS of 270 while consuming around 153 lit/hr of fuel. One of the major differences between the 500 and 600 is that the fuel tanks are approximately fifty per cent bigger. Of course, if you fill the tanks you can’t fill the seats, (operating any turbine-powered aircraft requires a compromise) but if you do fill the tanks the range is almost 1,500nm, including IFR reserves. Usually I’d make an observation here about the endurance (over seven hours) being buttock and bladder-busting, but the seats are very comfortable− although a headrest for the pilot wouldn’t go amiss−and a ‘unisex’ relief tube is provided!
A more representative ‘mission profile’ is that it can easily carry about 500kg (four adults and lots of luggage) over 800nm. However, the great strength of operating such a well-equipped turboprop is the ease with which you can make the best use of the upper winds. The G3000 can even manage the descent−a useful asset when you’re flying single pilot at 28,000ft with a groundspeed of 300kt and approaching a busy TMA. The cabin pressurisation runs at 5.6psi, which equates to a cabin altitude of approximately 10,000ft when the aircraft is at its certified operating ceiling of FL280. You don’t even have to worry about your passengers’ ears should you have to expedite your descent−the digital pressurisation system controls the cabin pressure so smoothly they won’t even notice, as I found out when Thomas told me to try an emergency descent from
10,000ft to 4,000ft. I pulled the power back to flight idle (which essentially turns the prop into a giant disc airbrake) and pushed the yoke forward. This produces a very high descent rate, while the much higher Vmo ensures I don’t overspeed the airframe. High or low, fast or slow−this really is a very flexible flying machine.
Once level at 4,000ft the controller gives us radar vectors back (incidentally, whoever renamed Kidlington ‘Oxford-London’ either has a fine sense of humour or a poor sense of direction, but I digress). The sky isn’t that busy, but if it were the optional GTS 855 TCAS with ADS-B in and out would be much appreciated. The big screen of the G3000’s PFD makes the approach very easy to fly, and if I wasn’t quite sure where the runway was I could clearly see it, as the synthetic vision is overlaid on the PFD. Thomas recommends setting 400ft-lb of torque at the top of the glideslope and, with the undercarriage down and the first stage of flap, it really does feel as if we’re on rails as we start the long slide down the invisible slope to the waiting runway at 120kt.
As we draw nearer the long cowling slightly impedes my view of the runway but full flap pitches the nose down a bit, improving the view and reducing the speed to 95. Easing the power lever back as we cross the fence the speed starts to wash off, but we still float in ground effect before the mains settle gently onto the runway with the typical ‘chirp-chirp’ of rubber accelerating from zero to 80kt in a instant. Lower the nosewheel, then pull the power lever into reverse−the engine roars, the airspeed collapses and within seconds I cancel reverse to avoid eroding the prop. An excellent feature is that, had I made a complete mess of the approach in hard IMC, all I would need do is hit the TOGA button on the power lever, as the enhanced AFCS can fly coupled go-arounds. Basically, the autopilot levels the wings and pitches the nose up nine degrees, and if the published missed approach procedure is loaded and active all the pilot has to do is push the NAV button on the autopilot controller and it will fly the entire missed approach. It really is quite incredible just how capable the automatics are.
A hugely impressive machine
I was hugely impressed by the M600. Piper has really thought about how it can ease the passage of a PPL/IR transitioning from an Arrow or Comanche onto their first turbine. It has range, power and speed, coupled to some of the most advanced avionics in civil aviation, and yet is not actually that difficult to fly. If only I were rich...
Five-blader increases ground clearance, wide-track undercarriage makes for stable handling on the deck
Seats fold for easier access, but it’s still something of a scamble to get into or out of the cockpit
Above: overhead panel and trio of G3000 screens make for a 21st century airliner-style cockpit, yet the degree of automation — including pressurisation control — reduces the pilot workload to an astonishing degree
Above: a perfect view, even in the murk — G3000 synthetic vision display; dual GTC 750 interface
Test aircraft’s muted cabin hues perhaps reflect European tastes — other colour and trim options are available
Right: production models will carry LED landing lights on main legs. Nosewheel (far right) retracts aft
Clamshell door welcomes you aboard but is the sole access to cabin and cockpit Inset right: vane at root of tailplane directs air flow over rudder to aid spin recovery. Weather radar pod (far right) is now set in wing leading edge
Five-blade propeller makes the best of the extra power, clever intake design gives automatic inertial separation
Above: turbine oil sight gauge replaces the dipstick
Brochure shot: as our flight test makes clear, the M600 has great inner beauty underpinning its good looks