Tuesday, March 1, 2005
Adam A700: First Of The Microjets?
The race to bring the first of the very light jets to certification is turning final, And the upstart from Denver is looking like it may be the new leader to the finish line
I flew the prototype Adam A500 last year from Adam Aircraft’s home field south of Denver, and despite my reservations about the huff-and-puff concept in general, questionably executed on the Cessna 337 Skymaster, I was impressed with Adam’s first product. (See “Adam A500,” Pilot Journal, November/December 2003.) Rick Adam recently invited me back to the company’s R&D facility at Denver’s Centennial Airport to fly the A700 jet. With only about 150 hours on the Hobbs, the airplane still was in an early stage of development, so there was no chance to explore the full performance envelope, but I did get to sample flight, takeoff and landing characteristics.
From the outset, Adam’s plan was to build the A700 as structurally similar to the A500 as possible, the better to reduce certification and production costs. Reportedly, about 80% of parts are interchangeable between the two models. To that end, the all-composite A500 was deliberately overbuilt so the jet version could fly heavier and faster, and accordingly, both models share essentially the same fuselage, wing and tail, the latter components fitted with TKS anti-ice systems. The A700 features an A500 cabin stretched 21⁄2 feet to accommodate a fourth row of seats. Installation of the optional aft lav reduces the total seats to seven.
As you might imagine, the jet’s need to fly taller (the A700’s ceiling is planned for about 41,000 feet) dictates a higher pressurization differential—8.33 psi compared to the A500’s 5.0 psi. This will allow an 8,000-foot cabin at max altitude and max differential. The Adam A700 also sports upturned winglets at the tips. Landing gear is identical to the A500’s, featuring wide-spaced, tough, trailing link members.
The A700 will be the largest of the proposed microjets, nearly as big as a Cessna Citation CJ1. Wingspan is a wide 44 feet, although the twin-boom tail stands only 10 feet tall. Operating weights hadn’t been defined at press time, but Adam hopes to hold empty weight to 3,700 pounds against a gross of 7,000 pounds. If he can realize those numbers, he’ll be able to offer a full fuel payload near 1,100 pounds, six folks plus baggage, with some of the latter stored in a long nose baggage compartment. At reduced fuel load, the A700 will accept two pilots up front plus six passengers in back.
The most obvious difference be-tween the A500 and A700 is piston versus jet power. The piston A500 flies with a couple of turbocharged, Continental TSIO-550 engines rated for 350 hp each. The A700 utilizes twin Williams International FJ33-4A-15 turbofans mounted on the aft fuselage, DC-9 style. Sam Williams made his fortune building small, cruise-missile jet engines in the 1980s and ’90s, and he’s now applying the same “less is more” technology to all powerplants for the corporate jet set.
The Williams FJ33 engine was certified last fall and is a scaled-down version of the company’s FJ44 that currently powers the CJ1, Raytheon Premier and the upcoming Swearingen SJ-30-2. The FJ33 is about 80% the size of the derivative FJ44 and delivers two-thirds the rated thrust, specifically 1,200 pounds (1,568 pounds is maximum power), but it utilizes the larger engine’s stronger, full-size gearbox.
Adam worked with Williams conceiving the FJ33, and one result is that the engine is unihanded, with airframe connections, mounts and oil dipsticks on both sides. This means engines may be mounted on either side of the airplane, minimizing downtime and allowing operators to avoid stocking handed engines.
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