Stepping up

It’s been said that “With great power, comes great responsibility”. And while the quote may be credited to a Marvel comic franchise, it is also a truism as a pilot moves up the performance ladder. Inherently, aircraft systems become more complex and performance and planning provide a greater challenge. Furthermore, the issue of pilot currency becomes even more critical as the more advanced the aeroplane, the more easily a pilot can be “left behind” if individual skills are not maintained.

‘With great power, comes great responsibility.’

Consequently, manufacturers are presented with a challenge to provide the desired enhanced performance envelope while making the progression relatively straightforward for the pilot and including adequate safeguards. This is particularly the case for the M600 and Piper has obviously given the challenge due consideration.

Keeping it Simple

As a six-seat, single-engined, pressurised turboprop, the marketplace for the M600 would seem to stem from the single-engined piston pilot or businessman who is seeking something more. On offer is a slightly wider cabin and the ability to fly around 80 knots faster, 500 nautical miles further and 10,000 feet higher than a comparable piston-engined aircraft. Fundamentally, this achieved by the 600 SHP Pratt and Whitney PT-6A-42 engine up front and a cabin pressurisation system. These two major components will be new to many potential buyers of the M600 and so will the systems associated with them. Intelligently, Piper have designed the aircraft to smooth out the transition and protect the pilot in the process and they have done this in a number of ways.

Firstly, the throttle, propeller and mixture levers of a piston aircraft have been replaced by just two levers – the Power Control Lever and the Condition Lever. Logically, the Power Control Lever is used throughout the flight to set the power by changing the propeller’s blade pitch and on the ground also offers ‘Beta Range’ and ‘Reverse’. As a protection against inadvertent selection in flight, the M600 has a ‘squat switch’ on the nose gear that prevents the pilot from moving the power control lever aft of the ‘Flight Idle’ position in flight.

The Condition Lever controls the run and shut-off function of the fuel control unit and is moved fully forward at engine start and fully aft at shutdown, so unless an emergency calls for its use to ‘feather’ the propeller, it does not require pilot input in flight. Simple.

The cockpit layout is similarly well thought out in terms of switch positions. A natural flow of overhead switches from left to right and then the lower panel in the opposite direction will prepare the M600 for engine start, while reversing the flow after flight will shut the aircraft down.

Most PT-6 engines require a manual selection of the inertial separator, a device that diverts damaging debris and ice from entering the engine. The M600 has incorporated an inertial separator behind its NACA inlet and ducting on the cowl that requires no pilot input in normal operations and expelling material through a bypass outlet beneath the outlet. One less lever for the pilot to forget.

In flight, the M600’s Electronic Stability and Protection System (ESP) is an electronic monitoring and exceedance-correcting technology is integrated into the cockpit and assists in maintaining the aircraft in a safe, flight-stable condition. The ESP is designed in certain situations to prevent the onset of loss-of-control conditions like stalls, spins, or steep spirals. The ESP functions independently of the autopilot, operating automatically whenever you hand-fly the aircraft. The way it works is quite simple —initially, the autopilot servos engage to provide a resistance force whenever pitch, roll, or high-speed deviations exceed recommended limits. If the pilot operates in the ESP envelope for an extended period of time, the autopilot will automatically engage in Level Mode, commanding the aeroplane to ‘wings level’ and with zero vertical speed. Additionally, right in the pilot’s eye-line is an obvious round, blue button, or ‘Level Switch’ which also activates the autopilot Level Mode.

With the M600 possibly being the pilot’s first pressurized aircraft type, there is also a Hypoxia Recognition and Emergency Descent Mode (EDM) installed. This detects pilot incapacitation due to the effects of hypoxia or other physical condition. This is accomplished by monitoring pilot response to various message prompts. If the system determines that pilot is not responding, Emergency Descent Mode is activated, placing the aircraft in a descent to a lower altitude to provide an opportunity for the pilot and passengers to recover from the effects of hypoxia.

The system is operative when the autopilot is engaged, and the aircraft cabin altitude exceeds 14,900 feet pressure altitude. After a period of inactivity (time is dependent on cabin altitude) the pilot is prompted for a response. If no response is detected the aircraft will initially descend to 14,000 feet and then to 12,500 feet MSL.

All of these systems and their controls are logically considered and presented. And while no system the relieves pilot of their command responsibility to both understand and fly their aeroplane proficiently, there is piece of mind in knowing that these systems exist to support them.

‘There is peace of mind in knowing that these systems exist.’

The Elephant in the Room

The most common discussion encountered regarding types such as the M600 stems from the fact that it is a single-engined aeroplane, yet it is often overlooked in flight reviews. Yes, there is no denying that there is only one engine, but it must be considered in context, particularly when considering a single-engined turboprop aircraft as to a piston engine.

At the heart of the issue is the M600’s heart – the venerable Pratt and Whitney PT-6 engine. At last count it has flown more than 400 million, yes – 400 million, flight hours around the world and been in existence for more than half a century. It is the benchmark for turboprop engines. Depending on whose statistics you read, a general figure seems to reflect that there is a PT-6 engine shutdown once for about every half a million flight hours. And that is shutdown – not failure. These numbers include twin-engined aircraft such as the King Air that may shut down an engine down as a precaution. It is such a trusted powerplant that it is used in all manner of single-engined turboprop operations around the world, including Australia’s own Royal Flying Doctor Service in their Pilatus PC-12.

Should the statistics somehow let the pilot down in an M600, the aircraft has the ability to feather the propeller and significantly reduce the drag generated. This has a tremendous effect on the gliding range and a conservative ‘ball park’ figure is that the aircraft will glide 25 nautical miles for every 10,000 feet above ground level and given that the M600 normally cruises at around 25,000 feet, that does offer around 35 minutes and 60 nautical miles of options.

Another consideration is the age-old debate of single-engined versus multi-engined aircraft, particularly for the pilot who may not be a frequent flier. An engine failure after take-off in any aircraft is a critical situation. The loss of an engine after take-off in a ‘twin’ comes with a loss of performance greater than the 50 per cent most people assume and introduces an additional skill set to maintain control in an asymmetric situation. Unfortunately, this control issue has led to the demise of a number of pilots in the past as it is a skill that requires constant vigilance, training and practise.
Ultimately, the decision rests with the purchaser and pilot when they weigh up the pros and cons of the single-engined versus multi-engined debate, but it is a conversation that must always be had in light of the best supporting evidence at the time.

Flying the M600

To a backdrop of classic aircraft from the past such as the Lockheed Super Constellation and the Caribou, the Piper M600 stands on the ramp at Wollongong Airport under blazing blue skies. Its smooth, sleek lines are eye-catching and the sound of the PT-6 engine spooling up and lighting-off has heads turning as Piper’s Thomas Nielsen taxies off to show a prospective customer the M600’s performance.

It is to be a short local flight, although the turboprop Piper has a maximum range of around 1,500 nautical miles at long-range cruise, with reserves, or a maximum cruise speed of 274 knots in the flight levels. As with most aircraft in the six-seat category, fuel and payload are elements that often traded at each other’s expense. This is a common equation that any potential buyer must assess based on their own requirements.

With full fuel, the number of people on board is reduced to three 90 kg individuals plus some baggage. However, full fuel will take you a long way in this aircraft and its always worth considering what will be the most common sector length to be flown and whether one’s passengers would prefer a pit stop every two to three hours. Operating between Sydney and Adelaide is around 600 nautical miles and three hours flight time for the M600 and it can comfortably lift a full complement of 90 kg passengers on such a sector. In fact, it can fly 900 nautical miles with that load and reserves if needed.
After Thomas has shut down once again, we inform him that it will be six on board for our flight in the M600 and based on the interest that the aircraft generated on the tarmac we could have taken a whole lot more. As the gathered spectators look on from a distance, we commence a walk-around of the aircraft and consider its features in more detail.

Commencing with the ‘sharp end’, the PT-6A drives a five-bladed Hartzell composite ‘Scimitar’ propeller that has an improved ground clearance over its predecessor. The cowling has an overall sleek appearance as the NACA ducting as opposed to a substantial intake is far more streamlined. Under the cowling, the PT-6A engine is a very compact unit, with a visual oil indicator to complement the dipstick. That being said, the old saying is that the most oil a PT-6 uses is what you wipe off the dipstick.

Thomas describes the wing of the M600 as the ‘crowning jewel’. Spanning more than 13 metres, it is a completely new design and a key reason behind the enhanced performance compared to the M500 and a significant Vmo increase from 188 knots to 251 knots. The wing has symmetrical stall strips on the leading edge of both wings and are designed to initiate the stall on the inboard section and away from the ailerons and tips.

Subtle winglets also contribute to the wing’s performance as well as looking sleek. On the trailing edge, the flaps carry through the philosophy of simplicity with just two settings – take-off and approach – and no ‘degrees’ quoted intentionally. The first stage of flap can be extended at 147 knots, although Thomas informs me that the standard sequence for configuring to lad is gear – flap – flap. At the bottom end of the speed regime, the stall in landing configuration is at 62 knots, which is comparable to piston-powered contemporaries.

Beneath the wing, the undercarriage has larger tyres and a broader span than the earlier model. Combined with the improved propeller clearance, piper anticipate operations from other than paved runways to be passed by the FAA in October.

The aircraft is approved for flight into known icing (FIKI) and has its wings, tailplane and windscreens protected accordingly. A discreet fairing on the fuselage near the tail has the effect of directing airflow to the rudder to enhance authority and is the result of spin testing that involved more than 900 spins and recoveries.

Entrance to the aircraft is via a two-piece air-stair and on boarding there is no tendency for the aircraft to sit aft as some larger singles do. Access to the cockpit is through the four cabin seats which are arranged in a club-seating format and boast a high class corporate-style finish.

Once seated, it easy to feel right at home and find a suitable eye-line that offers an external perspective and a clear view of the impressive Garmin G3000 avionics suite. As I was to find during the flight, the G3000 is an impressive unit. Its three large 14-inch screens can be configured through myriad selections of instrumentation, engine indications, charts, maps and the like and in turn spilt into an arrangement of sharing the screens 60/40 in proportion of the information. For someone that first gained an instrument rating three decades ago, with ‘DME Homing’ and ‘Back Beam Approaches’, the modern avionics packages never cease to amaze. Still, the system is very intuitive and inputs via two GTC input pads make everything from selecting a radio frequency to loading a route relatively simple. You can even uplink satellite weather or text your ETA to a loved one.

Back at sea level, we start the PT-6 with ease. Check the electrical load, start the sequence, move the condition lever to introduce fuel above 13 per cent gas generator speed (NG), watch that the light off does not exceed 1000 degrees and then check that all other parameters are stable. With the engine running, the air conditioning is selected, offering a pleasant environment in the cabin as the sun bore down outside. As previously mentioned, the switching of systems before and after start are very straightforward.

Taxiing the M600 is easy and there is minimal need for brakes as moving the power lever into Beta range more than adequately slows the aircraft and controls its speed. With the preflight sequences complete and the flaps selected for take-off, it is time to take flight.

There is no FADEC on the PT-6, so care must be taken as the power lever is advanced not to over-torque the engine, although the fact that engine is derated down from 850 SHP to 600 SHP offers some protection.

At 85 knots the aircraft wants to fly, and rotation is easy, although soon after pitch forces come into play that call for a trim input. Cleaning up the landing gear and flap, we depart overhead, accelerating to a 145 knots cruise and achieving an impressive 1,600 fpm on a rather warm Sunday afternoon. The best rate of climb is quoted as 122 knots, but the nose attitude associated with that speed would severely limit the forward visibility.
The aircraft is an absolute joy to fly, even when the hot day offered up its bubbles and bumps of rising air. Its characteristics in turns are quite harmonized and the noise levels are very reasonable considering there are 600 horses out in front. It was a point that the passengers noted also. Judicious use of friction and trim make the aircraft far more stable when setting power and attitude and I personally found using the manual trim advantageous as it gave immediate feedback relative to the input. Although I am sure with more experience on type, the electric trim would become second nature.

‘The aircraft is an absolute joy to fly.’

A series of steep turns were flown, initially to see the EPS system take effect and then to assess the aeroplane’s handling. Between the inherent stability of the trimmed aircraft and the flightpath vector on the Garmin display, steep turns could be flown accurately and with ease. The M600 at times felt a little light in pitch with changes in power and attitude, but this also serves to remind the pilot that this is a high-performance aircraft.
After an extended period, and with some reluctance, I engaged the autopilot and was impressed with its simplicity and functionality. The autopilot mode control panel sits along the glareshield, allowing the eyes to stay ‘outside’ as the selections are made. At this time Thomas called up the latest weather for Adelaide and showed me a wide range of other functions the system had to offer.

All too soon we commenced descent and headed back to Wollongong, whistling along well above 200 knots and the torque set at 1500 until the looming escarpment suggested that there maybe turbulence ahead. Retarding the power control lever, the propeller became a high drag disc and the speed effortlessly bled back to 145 knots to penetrate the rough air ahead. Certain high-performance piston singles are fitted with speedbrakes, but the M600 has no need for these.

With the airport looming ahead, the speed continued to bleed back to enter the circuit at 120 knots. Trimmed out at 1,000 feet, the aircraft felt wonderfully stable and continued to feel that way as landing gear, then take-off flap and finally landing flap were extended and checks completed. The Garmin display offered up a wonderful representation of the terrain and runway outside, but my eyes were firmly outside on such a wonderful day, only hunting inside to verify the speed and power setting.

Kept in trim, there is virtually no need to adjust the power through the entire approach, with the extension of landing gear and flap bringing the speed back towards 90 knots on approach. Moving the power lever slightly, it is noticeable how much the propeller can ‘bite’ the air compared to a piston-prop aircraft and there is a need to ‘milk the mouse’ with small and subtle changes only. Also, as the propeller can become a flat plate of drag at idle, pilots converting onto the M600 should be very wary of cutting the power abruptly as they cross the fence. I cheated and kept a dribble of power on right into the flare, but I’m sure that with experience on the type it wouldn’t be necessary.

The book quotes that the M600 can take off and land in around 800 metres, using reverse for the arrival. For the final circuit in our flight, the aircraft was brought to a full stop using only beta range and the deceleration was both smooth and quiet. Clear of the runway, we taxied to the bowser so that Thomas could refuel for another sortie. Parking the brakes, I simply reversed the flow of switching and shut the M600 down, while the 5-blade Hartzell propeller slowed and then stopped.

Stepping Up

The Piper M600 sits in a niche that not many aircraft currently fill. For all of its wonderful features, possibly its greatest offering to potential owners is its underpinning design philosophy.

For the pilot or businessman looking to take that step up in performance, it is a significant step. However, through its relative simplicity of operation and available safeguards, the Piper M600 makes the progression achievable in conjunction with a sound foundation of training and ongoing commitment to the standard needed to operate any high-performance aircraft.

‘The Piper M600 makes the progression achievable.’

At first the question was asked, “Have you ever wanted the luxury of a personal touring aircraft with the performance of a turboprop up front?” If so, the Piper M600 might just be for you.