The AB139 is not just your boss's corporate taxi. It also fills the need for a powerful utility workhorse.
I have followed the AB139's progress with a great deal of interest since Max Wiley of Bell Helicopters first briefed me on the aircraft in 2001. Until then, I had thought of the AB139 as just another pretty corporate bird to fly the boss in. One look at the horsepower rating of 1,620 shp. per side with a hovering out of ground effect (HOGE) of 12,500 ft. standard day conditions at a gross weight of 13,900 lb. convinced me that this helicopter has more potential for utility work then I first imagined.
The static display of the AB139 at Heli-Expo 2003 in search-and-rescue configuration showed an aircraft with great potential for a variety of missions. The ability to access the large baggage area from the main cabin while in flight is also a useful feature, as is the access to the baggage area or refueling ports from either side of the tail boom on the ground. Seating in the main cabin was comfortable, with good headroom even for my 6 ft. 1 in. frame.
Last year, a trip to the American Helicopter Society Convention provided me the opportunity to see the actual aircraft at Bell/Agusta Aerospace temporary test facility in the Phoenix area. The impression I gathered from a good look around the de-cowled aircraft was of simplicity of layout and good access for the maintenance folks. All the components appeared to be well-built and substantial—nothing on the aircraft felt cheap or flimsy.
With this background, I was excited when the offer to fly the AB139 at Heli-Expo 2004 was tendered by Bell/Agusta. When the day came, however, I was informed that I was to be bumped as pilot since a pilot from a company that was close to a decision on buying an AB139 needed to fly the aircraft. I was disappointed, but quickly realized that flying as a passenger might be an advantage to understanding the aircraft better than if I flew it.
Each pilot position has a pair of Primus Epic 9x7-in. EFIS displays. The primary display covers standard flight parameters in a user-friendly format. Also included on this display are fuel flow, an air data computer for outside wind speed and direction, radar altimeter and a power indicator. The power indicator shows exhaust gas temperature, gas producer and torque as separate values and then merges these values to a single gauge that shows the parameter that will be exceeded first for the ambient conditions. The second display covers engine parameters and pull up screens showing pilot level electrical, fuel or hydraulic system diagrams. These displays seemed to be reasonably readable in direct sunlight. A flight management system is included with the standard aircraft. Layout of battery, generator, hydraulic switches, etc. will be familiar to pilots of medium-sized Bell helicopters. Throttles are overhead, but on the bottom of the collective head are two momentary electrical switches that can control the overhead throttles. Immediately above the two throttle switches are the respective emergency governors. This allows the pilot to handle either a tail-rotor failure or governor failure without having to release the collective. Visibility out of the cockpit is tremendous, although long-line external load operations might be difficult—since it is a long way from the pilot seat to the edge of the floor for a direct view of the load. Night-vision lighting will be addressed by Bell/Agusta as development proceeds. The pilot and co-pilot seats are comfortable. The aircraft has two zones of air conditioning standard, one in the back and one for the flight crew. All and all, a nice place to start the day.
The start was easy, one switch to flight idle for each engine. The run up procedure was simple, including the control checks that are accomplished with a hydraulic pump powered by an electric motor for ground use only. The pilot releases the controls, pushes the control check button and the sticks do their pre-programmed moves. The pilot then gets a "good-to-go" light and it's done. Our flight was off of a single spot pad, so evaluation of ground handling was not possible. The main gear can go up or down at VNE. Cycling the gear at 100 kt. was hardly noticeable inside the aircraft. The aircraft had five people on board with 1,760 lb. (780 kg) of fuel and a considerable amount of test gear. The total operating weight was not divulged. Climb out was brisk. Once we attained 4000 ft. MSL at 26 deg. C, an 80-percent torque setting gave a 152-kt. indicated airspeed. The ride of the aircraft at this speed was very good, with interior noise much better than the Bell 412s I am use to. The Honeywell autopilot was run through its functions. Yaw control at a hover was impressive, with trim release switches on the pedals appearing to be well integrated. Roll control with the coolie hat was still being tweaked by the engineers from Honeywell and was not in its final configuration. In demonstrating simulated engine failures at a 4,000-ft. MSL out of ground effect hover, at 24 deg. C., the factory pilot indicated drooping the rotor to 96 percent Nr with a non-emergency limit of 140-percent torque, (160 percent in a real failure) should work well. We flew away at these conditions with perhaps a 5-10-ft. loss of altitude. Shut down included a 1-min. cool down which may be lowered to 30-sec. in the future.
I came away with a very favorable impression of this aircraft. Time will tell on the maintainability of the aircraft. Figures quoted to me last year for flight hour to maintenance labor-hour ratios seemed over optimistic but maybe possible in light of all the improvements in this area over current medium twins. I certainly hope so.
Lee Benson is senior pilot for the Los Angeles County Fire Department, which is considering acquiring the AB139.