When Piper announced its new PiperJet at the National Business Aviation Association's 59th Annual Meeting and Convention last October, it promised to create a whole new category of personal or business airplane. With an expected top cruise speed of 360 knots, IFR range of 1,300 nm, an operating ceiling of 35,000 feet, and all of that performance coming from a single turbofan jet engine,the PiperJet is unique. Piper says you can have all of this for $2.199 million in 2010.
It appears that the PiperJet, assuming it meets its objectives, would create a fourth category of light jet. The first category of the new light jets includes the Cessna Mustang, which is a totally conventional twin-engine jet that meets all of the traditional jet standards, including engine-out takeoff safety standards. The Mustang differs from larger business jets such as the Cessna CJ family only in size and cost, but not in terms of certification standards or levels of redundancy.
The second category includes the Eclipse 500, which is a twin, but does not meet conventional jet standards. Eclipse has certified the 500 to light airplane requirements meaning, for example, that like a piston twin, it will be able to continue after an engine failure in most circumstances. However, unlike all other jets previously certified, it is not required to demonstrate that it can continue after an engine failure at the worst possible time.
A third category of new light jets would be the Diamond D-Jet and what little we know about the single-engine jet that Cirrus is taking orders for. These are truly personal jets with performance and flying qualities more akin to a turboprop than jet. These personal jets, as some call them, are modest in performance but their uncomplicated systems and flying qualities make them ideal for less experienced pilots who want to move up.
But the PiperJet would be in a different category of light jet. With its proposed top cruise speed of 360 knots it is as fast, or faster, than the light jet twins. The announced 1,300 nm IFR range is amazingly long, longer than other light jets and better than many, much larger, traditional jets. And its 35,000-foot ceiling is smack in the middle of the high jet flight levels, and not far from the 41,000-foot maximum of the multi-engine light jets. With its expected performance the PiperJet transcends the personal jets, but because it has only a single engine, it will be much more accessible to pilots without considerable multi-engine experience. Insurance companies have been quite comfortable with lower time pilots moving into the single-engine turboprops such as the Piper Meridian, TBM-700 and now 850, and the Pilatus PC-12. It seems likely that the attitudes will be similar for the PiperJet, particularly when you consider that the TBM-850 is already close in terms of cruise speed and altitude. In fact, much of the expected PiperJet performance can be credited to having only a single engine because that one and only engine requires a lot less fuel than two. That's good news at the fuel truck, but in terms of performance, it's all about weight. With one engine you save the weight and drag of a second engine, but more importantly, you don't need to carry the fuel to feed it. With less fuel the airplane weighs less and is thus more efficient, whether you take that efficiency in terms of speed, or slow down and reap the benefit in range.
But where on the airplane to put that single engine? Instead of burying the turbofan in the fuselage where it could be mounted further forward, Piper has elected to mount the engine on the vertical fin, much like the DC-10's center engine. This engine location simplifies feeding air to the engine because there is no need for ducts in the wing roots or fuselage. But the tail-mounted engine does move the center of gravity far aft, and with the thrust line above the center line of the airplane, power changes can affect the pitch attitude.