Every pilot wants more useful load, and Piper provides 242 more pounds of it in its new Piper Meridian single-engine turboprop, thanks to an increase in maximum takeoff weight. And the company also switched to the new Meggitt Magic 1500 autopilot that offers the performance and features a pilot expects in a turbine airplane.
When Piper introduced the Meridian in 2001 it had a 4,850 pound maximum takeoff weight, which was capped at that level by the FAA requirement that single-engine airplanes stall at 61 knots or less at maximum certified weight. With more than 1,000 shaft horsepower available from the Pratt & Whitney PT6A-42A engine, power to lift more weight was never a question. The Meridian wing and other primary structure also had the heft to carry extra weight. But the stall speed rule was limiting what the Meridian could carry.
Piper had a couple of choices available to increase the takeoff weight of the Meridian. One was to demonstrate improved crashworthiness to get a couple extra knots added to the maximum stalling speed. Socata had achieved this with its TBM 700, and Pilatus had done the same with its PC-12. The other option available was to reduce the stalling speed so the airplane could carry more weight up to the 61-knot maximum.
Piper engineers decided to focus on reduced stalling speed to achieve the increased weight goal. The primary driver in their decision was to control empty weight. Increasing the max takeoff weight adds to the useful load only if the empty weight of the airplane doesn’t increase in the process.
One way to reduce stalling speed is to improve the efficiency of the wing flaps. The 61-knot maximum applies to the landing configuration, so any improvement in flap effectiveness would do the trick. But the Meridian flap is already very long in span, consuming most of the trailing edge of the long, slender wing. And the design of the flap itself, and its extension angle, is pretty well optimized, so very little, if any, improvement was available by modifying the wing flaps.
The other available option to reduce stalling speed is to micromanage airflow over the wings and tail. Airflow can be tailored by some sort of a small device on the airframe that generates a high-energy wake when the wing is flying at certain angles of attack. These devices go by many names, but the term vortex generator (VG) covers the category because it best describes what the devices do-generate a vortex.
The energy in the vortex that streams aft from a VG is used to direct air to flow the way the aerodynamicists want it to over the wings or tail. It would seem logical that air wants to flow straight aft over an airfoil, a straight line being the shortest distance, and all of that. But when a wing or tail is operating at a high angle of attack, many forces interact to cause the air to try to flow in all sorts of directions, including spanwise, or even forward. The energy in the vortex created by a VG acts as a fence to keep air flowing in the desired direction, which is aft. Years ago many jets had physical fences in the form of a chordwise blade that directed airflow near the stall, but the physical stall fences have virtually all been replaced by some form of VG.
Piper experimented with various VG configurations and came up with a series of 92 on the wing and 80 on the underside of the horizontal stabilizer that reduced stall speed. The tiny VGs are bonded to the surface and weigh only a few ounces. The VGs resemble little I-beams with beveled leading and trailing edges and are a fraction of an inch high. They add an immeasurably small amount of drag at cruise angle of attack, but as the airplane approaches a stall, they help keep the airflow attached to the surface and smoothly flowing aft to a lower airspeed. Thus, the Meridian can weigh 5,092 pounds and stall at 61 knots, compared to 4,850 without the VGs. In addition to being extremely light, the VGs require no maintenance, and you can dispatch with as many as five missing.
The only other change to accommodate the higher takeoff weight is some strengthening in the landing gear area. Though the VGs could easily be added to any existing Meridian, the changes to the landing gear make a retrofit to the higher takeoff weight impractical at this point.
A current production, typically equipped Meridian weighs in at around 3,390 pounds. With a max ramp weight of 5,134 pounds, that leaves a useful load of just under 1,750 pounds. Fill the 170-gallon tanks with jet fuel and you have just over 600 pounds of payload available for people and baggage. And that’s fueled for a four-hour trip with IFR reserves. Leave out an hour’s worth of fuel and you can fill the seats and still fly 500 nm and longer trips.
The other big improvement new to the Meridian this year is the Meggitt Magic 1500 autopilot in place of the original S-Tec 550 system. The 1500 autopilot is the first from Meggitt/S-Tec that uses attitude information, as well as rates of change in rate of turn and air pressure, to fly the airplane. Using attitude information to fly the airplane is the way most other autopilots function and the way all other turbine airplane autopilots operate, and it works well, and so does the new Magic 1500.
The highest praise I can bestow on the Magic 1500 system is that I felt no need to study the operating manual before using the autopilot. Its modes of operation and its annunciations are what any pilot with experience in turbine airplanes would expect to find. Mode selection buttons, altitude assignment and all annunciation are included in the autopilot control panel mounted in the center of the instrument panel where it is easy to see and use.
To take a look at how the Magic 1500 flies the Meridian, we launched into a relatively low IFR day at Westchester County Airport in New York headed for Bradley Field in Connecticut. The 1500 system is part of the full glass panel Magic electronic flight instrument system that has been standard in the Meridian from the beginning. The dual electronic displays are backed up by independent attitude, airspeed and altimeter instruments mounted in the center of the panel.
I selected go-around mode, and the flight director command bars on the primary flight display (PFD) provided target pitch angle for rotation. Go-around mode was missing on the original autopilot. Climbing through 800 feet on the Westchester One departure I engaged heading mode and cranked the heading bug around to 320 degrees, a big turn from the 160-degree runway heading. The 1500 is an aggressive autopilot, rolling smartly into a 30-degree bank and holding that angle all the way through the turn. That’s steeper than the 20 degrees or so most autopilots would bank at Meridian airspeeds, but the bank angle control was precise, and you sure can’t argue with the rate of turn it delivers.
Like the best turbine autopilots, the Magic 1500 altitude alerter is automated into the system. When you dial a new altitude into the alerter, the 1500 is automatically armed and ready to capture that new altitude without any other button pushing or knob twisting to arm a capture mode. I can’t remember which autopilot introduced this feature, but it’s great. Why would you ever want to climb or descend through the assigned altitude you have dialed into the alerter? You don’t. So why force pilots to arm altitude capture? The Magic 1500 does not, and it’s great. You’ll never fly through a target altitude without the autopilot capturing it, or the flight director commanding a level off if you are hand flying.
The Magic 1500 has a built-in aural alert system that uses a female voice to announce events such as approaching an assigned altitude and so on. The voice callouts are helpful under most circumstances, but they can be intrusive in very busy airspace where the controllers talk nonstop. In that case, it’s easy to silence the callouts.
The Meridian is a strong climber with its full-rated 500 shp available to about 25,000 feet, and the Magic 1500 has the smarts to anticipate the level off and altitude capture smoothly without any abrupt attitude or vertical speed changes. The autopilot’s control of the airplane is precise at all airspeeds and it smoothly handled some turbulence we encountered descending through a cloud layer.
The controllers at Westchester gave the Magic 1500 a real challenge by vectoring us through the localizer and then back to intercept about two miles outside the outer marker. I had told the controller I didn’t mind a close turn on to the ILS and he needed to get us spaced behind an American Airlines Fokker 100 ahead.
The Magic 1500 showed its stuff on the intercept, and its 30-degree bank capability came in particularly handy to nail the localizer without any S-turning after the needle centered. I let the autopilot fly the Meridian below decision height, and its tracking of the ILS was smooth and precise all the way.
Most of the time the Magic 1500 uses roll steering outputs from the standard Garmin GNS 530 navigation systems to smoothly track the desired course. The roll steering is smoother than tracking needle deflection as previous autopilots have done, and it allows for smooth turns at leg changes as the Garmin navigator calculates and commands a leading turn to stay centered on course during leg change.
The takeoff weight increase will cost a knot or two of maximum cruise speed until fuel burns down, and then performance will match that of the original Meridian. Expect 260 knots, or a little more, at optimum cruise, and if you fly at FL 290 you can stay up for four hours with an acceptable IFR reserve. The new takeoff weight limit doesn’t change range, but it does change the range versus payload profile. In other words, in the new Meridian you can carry more people and stuff farther than you could before.
In early summer the Piper people told me that they experienced a sudden and strong increase in demand for the Meridian. A small inventory of Meridians was on hand in the dealer network, but that quickly shrank as pilots started serious shopping for high-performance personal airplanes. No doubt the new accelerated tax depreciation law had something to do with it, but the important changes Piper has made in the Meridian’s max takeoff weight and autopilot system are also important. Every new airplane needs to grow and improve, and it’s gratifying to see that Piper is adding more capability to this exciting personal airplane.
|2003 Piper Meridian|
|The airplane flown for this report was equipped with the Meggitt Magic avionics system that includes dual flat-panel EFIS on both sides of the cockpit, plus the new Magic 1500 autopilot as standard equipment. Garmin GNS 530s are also standard, as is the Bendix/King RDR-2000 vertical profile weather radar. All data here is from the Pilot’s Operating Handbook and reflects standard day conditions at sea level.|