Bell/Agusta got it right with the design of the AB139. It is another strong performer from Italy aimed at a well-thought-out market niche.
The decades of cumulative Agusta technology development shows well in the solid design and manufacture of the AB139. It is a winner.
Recently, I had the opportunity to fly Serial No. 006 of the newly FAA-certificated Bell/Agusta AB139 medium twin helicopter.
It was in 1998 when Bell Helicopter and Agusta in Italy decided to form a risk-sharing joint venture, the Bell/Agusta Aerospace Co. The venture’s primary purpose was to share in the continued development of one new major product that each company had under way: the Agusta A139 medium helicopter and the Bell 609 civil tilt-rotor.
Agusta was to be the lead partner in the helicopter, as shown by its redesignation AB139, and Bell was to lead on the tilt-rotor, redesignated BA609. This sharing of production, support, and sales provides an opportunity to broaden the capabilities and offerings of both companies.
The AB139 has received its European JAA certification in June 2003 and its FAA type certificate in December 2004. The company is aiming for certification of the BA609 in 2008.
Bell and Agusta have more than a half-century history of working closely together on helicopters, dating back to Agusta’s production of the Bell 47 and many follow-on models under license from Bell. Agusta has been a subcontractor to Bell on other parts. In the early 1970s, while preflighting for my first flight in a Bell 206A, I was surprised to find a data plate on the inside of the baggage door that read: "Made in Italy by Agusta".
Agusta strategically views the helicopter market on a scale of max gross takeoff weight (MGTOW) measured in tons. Rather than going head-to-head with their own or competitive products in a given tonnage range, finding a vacant gap that needs to be filled presents a far better business opportunity. There are no modern helicopters that are in the 7-ton (14,000 lb.) MGTOW range (+/- one ton, or 12,000-16,000 lb.). The AB139 perfectly fills this niche with an initial MGTOW of 13,227 lb. (expected to go over 14,100 lb. in the very near future).
My perspective is that Agusta got it right with the design of the AB139, which doesn’t surprise me. It is another Agusta strong performer aimed at a well-thought-out market niche.
Proof that buyers recognize the AB139 as a good fit for their operational needs is a Bell/Agusta order book that now has more than 100 orders from a wide variety of customer types, worldwide, with well over 20 orders garnered at HAI’s Heli-Expo 2005 in February at Anaheim, Calif. With AB139s going out the door at about $8 million a copy, the first 100 ships will generates some $800 million in revenue, a strong indicator that the niche needed to be filled. Many more sales yet to come.
Filling an open market niche can also provide opportunities to beat out competitors above and below your product’s tonnage if your acquisition price, direct operating costs, and design make better business sense than owning an aircraft in an adjacent tonnage category. I believe the AB139 will eat into the underside of larger helicopter markets above (like the Sikorsky S-92, and Eurocopter Puma) whose aircraft might not be fully utilized or be more expensive to buy or operate. Likewise, in the smaller helicopter markets below (like the Sikorsky S-76, Bell 412, and the Eurocopter EC155), the AB139 will warrant consideration for users who would like significantly more capability or room for only a nominal increase in costs.
The AB139 is a multi-purpose platform creatively designed to meet a wide range of mission profiles. It employs the latest of practical technologies–not for technology’s sake, but rather to increase performance and speed (167 kt. max cruise), to increase its useful load (presently described as about 5,500+ lb. and expected to increase), to provide creature comforts for passengers and crew and to minimize pilot workloads.
I flew the AB139 with Guiseppe Lo Coco, an experienced Italian flight test pilot for AgustaWestland. I had flown with Guiseppe before, in a pre-certificated version of the Agusta Koala A119 at the Agusta factory in Cascina Costa, Italy in March, 2000 (Rotor & Wing, June 2000, page 40). While Guiseppe is a very likeable guy, I like him most for his professional knowledge and superb pilot skills. He has been flying the AB139 for more than three years.
My trip to Agusta in 2000 drastically altered my opinion of Agusta’s technical competence and manufacturing capability.
I used to view Agusta as basically having only one product–the classy-looking A109 light-twin, and then its 1,002-shp., single-engine derivative, the A119 Koala. I discovered in 2000 that Agusta has greatly benefited from "an outside the box" mentality, in part a result of the experiences gained in working with most other helicopter manufacturers in the Western world.
These other manufacturers have long recognized Agusta’s technical prowess, with many entering joint production agreements with it. Thus, Agusta has amassed vast experience in a wide range of products, designs, and ideas. No other helicopter manufacturer has the cumulative crossbred helicopter experience of Agusta. It has manufactured, usually through license agreements, the following makes and types of helicopters: Bell 47, 204, 205, 206, 212, 412; Sikorsky H-3 (S-61); Boeing CH-47; Hughes (now Schweizer) 269; MD500, and 520N; the European Union consortium multi-role NH90 helicopter (with Eurocopter and Fokker); and the large tri-engine Westland EH101. The EH101 is now the AgustaWestland EH101, since Agusta bought Westland in 2004. In January, it was selected to be the new U.S. presidential helicopter, designated for obvious reasons in the United States as the US101. In all, Agusta has produced about 5,000 helicopters that are now operating in more than 80 countries.
In addition to civil products, Agusta has broad experience in military aircraft for multiple roles, including anti-submarine warfare, search and rescue, coastal patrol, troop transport, and gunships. No doubt the new AB139 can fill the many different paramilitary missions relating to homeland security needs.
Bell/Agusta’s is moving its headquarters from Alliance Airport just north of Fort Worth, Texas to Reston, Va. to better serve the many potential customers around the governmental flag poles.
Agusta makes a good case study, as some businesses, even in the helicopter industry, seem to develop a myopic focus on their own products, wrongly believing that their products are the only good ideas in the world marketplace, thus ignoring or dismissing what their competitors are doing. This "inside the box" mindset ultimately leads to an unpleasant, behind-the-power curve "wake-up call" when their market share dwindles and revenues drop.
Agusta’s broad history of crossbreeding rather than inbreeding helicopter ideas has positioned it well for developing new, meaningful military and civil products for the future like the AB139 in meeting the demands of an ever-changing helicopter world market.
Because of the AB139 market potential in the United States, Canada, and Mexico, a plan is under development for Bell to perform final assembly of AB139s at its Amarillo, Texas plant.
While I’d seen the AB139 on display, usually on crowded convention floors, I had not seen it sitting majestically alone on the flight line. Most agree Italians are known for their appreciation of beauty and style, be it in their art, countryside, architecture, fast cars, apparel, women, and, yes, even helicopters. The AB139 is strikingly good-looking–a tough trick for a big helicopter.
As Guiseppe guided me through a preflight walkaround of the AB139, several well-thought-out design items were obvious.
As we first approached the tail section, I noticed that the horizontal stabilizer has gracefully curved winglets on each end, as seen on the wings of many newer business jets and modern airliners. While they are uniquely stylish on a helicopter, I knew the earlier, pre-certificated versions did not have these winglets (as you can see in many early AB139 pictures). I also know that the engineering design of a helicopter’s tail section is more of an art than a science. There are no meaningful computer simulation programs or wind-tunnel tests to help predict what will be happening dynamically to the tail as rotor wash, slipstream, and winds are ever changing. As a result, trial-and-error flight tests are the method to fine-tune or fix tail rotor and horizontal fin design. Usually, the vertical fin is easier, since it is there to stabilize the more predictable yaw movements of forward flight. But on most helicopter prototypes there can be seen a number of changes in the horizontal fin’s size, angle, and location–usually to improve pitch stability, often in takeoff regimes. The AB139’s winglets help control airflow over the stabilizer airfoils, plus they look great. A nice touch.
The canted, four-bladed, articulated tail rotor has ground clearance of 7 ft. 8 in.–an obvious safety feature. On the tail boom’s mid-left side, there is a large horizontal strake–a perpendicular fin used to break up or spoil airflow. The strake is aimed at reducing the low-pressure area created by the advancing blade’s downwash on the tail boom’s left side.
The Airfoil Back There
Most pilots don’t view the tail boom as an airfoil, but it does behave like one. As power is increased, pressure on the boom’s left-side lowers even more, making the nose yaw to the right and requiring the pilot to input more left pedal–not for anti-torque, but to compensate for the low pressure. Reducing that low-pressure area with a strake is like giving the pilot more available left pedal to use to maintain heading. That’s nice to have in most hover, takeoff and landing regimes, but even nicer in hot and high conditions. There are no moving parts or scheduled maintenance in a strake, and no known downsides to having them.
The baggage compartment has easy access from either side of the aircraft through large doors and through the cabin’s aft bulkhead–which EMS and SAR users will really like for litters, baskets, or equipment stowage. The spacious, 120-cu.-ft. compartment seems larger than some hotel rooms I’ve stayed in.
The AB139 has a retractable tricycle landing gear, with the aft two wheel wells located outside the fuselage under unobtrusive sponsons. The sponsons not only serve as a place to retract the landing gear; they cleverly serve as a convenient maintenance step or–on the four-bag, pop-out-float-equipped ships–they become the secure external location for the two 17-person deployable life rafts. Keeping the landing gear outside the fuselage provides more room and flexibility in the aft lower fuselage for fuel tanks, flat floors, and cabin or baggage space. Having made five ocean crossings with my life raft inside the helicopter (where it is difficult to get out even when parked on the ramp), the AB139’s design of external deployable rafts makes really good sense, especially for the offshore market. The forward edges of the sponsons also house the primary landing lights on each side of the aircraft. A secondary landing light is under the forward belly.
On either side aft of the cabin are two, large, folding maintenance steps. These let you access the engine and aft upper deck area easily.
Once you are up on these steps, large hinged doors provide access to the two powerful (1,679 shp. each) Pratt & Whitney Canada PT6C-67C turboshaft engines in separate, fireproof compartments. Starting a helicopter design with ample engine power seems to elude most manufacturers, which is why you usually see a long series of ascending model suffixes (A, B, C… or 2, 3, 4…or even suffix combinations like B-2, B-3) on many helicopters as they mature. I believe Agusta made an excellent choice by starting with these big Pratts, which will carry the AB139 for many years. The PT6 family, with more than 280 million operating hours, is renown for reliability and has a strong history in many different airplane and helicopter makes and models. The AB139’s engines are equipped with full-authority digital engine controls (FADECs) to help minimize pilot workload, control start parameters, and log important health, usage, and maintenance information. The engine installation is clean and removal is reported to be very easy, with ample work room on the top deck.
The five-bladed, 45-ft.-dia. main rotor system attaches to a fully articulated, titanium main rotor hub that has been engineered for a compact profile. The idea here is to minimize rotor hub parasite drag, a vicious villain against speed–proportionally more so even than airframe parasite drag items. The spinning main rotor has a ground clearance of more than 9 ft.–another safety feature.
The large aft cabin (8.86 ft. long, 6.56 ft. wide and 4.66 ft. high) of the AB139 that we flew was configured for 12 passenger seats (three rows of four) in a low-density configuration that might be used to transport offshore workers to oil platforms. A 17-occupant, high-density configuration is certified with 15 rear seats (three rows of five) plus the two forward crew seats. Since the AB139 meets JAR/FAR Part 29 newer and more rigorous design criteria, all the seats, landing gear, and airframe must meet the energy-absorbing requirements typically not found on older helicopters.
Aft cabin flexibility is enhanced by having a completely flat floor that accommodates the full range of other interior configurations, including executive/VIP, EMS (with up to six litters and four medics), SAR, bulky cargo, and the wide variety of paramilitary or homeland security mission equipment needs. Entry and departure from the aft cabin is easy through the large (5.5-ft.-wide) sliding doors on each side. A 10-seat design for police or military insertion teams is two back-to-back, fore-to-aft rows of five seats with a straight-out exit through the large doorways.
Attractive and functional entry steps are on the lower fusleage below all the doors for the cabin and cockpit. Entry is easy into the aircraft. For executive and corporate users, imagination will be the limit on a wide range of very comfortable and plush interiors in the roomy aft cabin.
The AB139’s standard fuel tank capacity is 414 gal. (2,820 lb.) of usable fuel, with an optional auxiliary tank that adds another 129 gal. (882 lb.). Certification efforts are under way for a wide variety of internal and external options such as rescue hoists, cargo hook (6,000 lb.), forward-looking infrared and camera balls, EMS and medical interiors, search and weather radar, wire-strike protection, search lights, ice detection and protection, and special seating arrangements for specific missions. A valuable option for missions like SAR and paramilitary is the auto-hover capability of the four-axis autopilot option.
Agusta looked ahead and is developing an option to make the AB139 cockpit night-vision goggle compatible. By anticipating the need for NVGs, the manufacturer eliminates the high costs of aircraft downtime and expensive modification and certification for an operator. Non-NVG cockpits drastically reduce the function of the goggles due to non-compatible light glare, so any user that desires to use goggles can order the option for the NVG-compatible cockpit.
Single-pilot IFR certification will allow users flexibility in crew staffing and Category A performance (allowing continued takeoff if an engine were to fail on takeoff at MGTOW) will provide increased safety of operations from ground level or elevated heliports up to 7,000 ft.
Bell/Agusta is projecting an hourly direct operating cost of just over $800/flight hour. A wide variety of power-by-the-hour plans have been devised for the airframe, engines, and Honeywell Primus Epic avionics to help user predict and contain scheduled and unscheduled maintenance expenditures.
Flying the AB139 makes you forget it is heavier than a school bus or a Citation 2 biz-jet. The AB139 is agile and smooth, and the colored electronic engine tape indicators assure you at a glance that reserve power is readily available from the big Pratt engines. Starting is simple with the FADEC. Once some pre-start checks are made, it is just a matter of rotating a switch and the FADEC optimizes the start time by perfectly controlling fuel flow. There is no noticeable vibration during the start, as is sometimes evident on large helicopters. After a pre-takeoff check the helicopter wants to fly, acceleration from the hover is very quick to an economical cruise speed of 150 kt. As you approach the max cruise (and Vne speed) of 167 kt., the airspeed tape on the electronic display changes color to red to provide early warning that you’re approaching the certified limit. The ride is remarkably smooth, and would be pleasing to passengers and crew throughout all speed and regimes of flight. At 150 kt., Guiseppe demonstrated what would happen if you were to loose an engine: nothing. No changes in speed, pitch or yaw, and no noticeable noise changes. It was a non-event. The operating engine with its 1,679 shp. easily and automatically picked up the load under the control of the FADEC.
Another pleasant surprise is the excellent visibility from the cockpit seats. The instrument panel is low and the windows are large.
Certainly, a key to the smaller instrument panel is the Primus Epic modular, integrated glass cockpit. Gone are the arrays of boiler gauges and the space- and weight-consuming flight and engine instruments. Four portrait-oriented, 8X10-in. glass panels allow the crew to pick and choose configuration of the displayed information, which can be switched or combined showing varying amounts and types of flight or system information. There is still an ample gadget growth area for mission specific hardware in the blank center of the instrument panel. An easy-to-reach-and-see center console between the pilots houses the fuel cutoff, start, and FADEC switches, the flight management systems, and selectors for the dual automatic flight control systems in a well-laid-out pattern. The landing-gear control and indicators are on the right side of the console and operated by the required pilot in the right seat.
Docile and Predictable
Getting to know the switchology and systems will be accomplished with initial training in a CAE SimuFlite Level D simulator at Sesto Calende, Italy, with other training facilities planned elsewhere to meet demand. Effective training will be essential, since the MGTOW weight is above 12,500 lb., which in the United States will require a type rating for the pilot in command. FAR regulations have provisions for a type rating to be issued through an approved curriculums using a Level D simulators. Even though I was totally unfamiliar with the Primus Epic system, mastering and manipulating it seemed intuitive. The active matrix displays were full of meaningful information and easy to read at a glance, even in bright sunlight (though there is an understandable flight manual limitation against pilots wearing polarized-lens sunglasses).
The AB139 flight characteristics were docile and quite predictable, and will be pleasing to any pilot. All pilots seem to have a penchant for performance and excess power.
The AB139 should be a broad market pleaser, providing users with fast, smooth rides that would make any passenger, patient, soldier, or roughneck feel comfortable.
Ron Bower is a dual-ATP rated pilot and has been flying for 43 years, logging over 8,500 accident and incident free flying hours. He flew UH-1B Huey gunships in Vietnam, and has set two around-the-world speed records in helicopters. If you have any questions or comments about this article, feel free to contact him at firstname.lastname@example.org