Bell 429 flight tests gather momentum

By: Thierry Dubois

Aviation International News >> June 2007
Rotorcraft Aircraft

Bell is planning to add the second 429 prototype to its flight-test effort next month. The first example of the new light-twin helicopter has already convinced design engineers that they can stay with a four-blade tail rotor.

As of late April, the second aircraft was undergoing preparation to enter the flight-test phase. The Fort Worth, Texas-based manufacturer will use five helicopters–two prototypes and three production aircraft–in the flight-test program in Montreal, Bell 429 program director Bill Stromberg told AIN.

Also by late April, the first prototype had flown approximately 60 hours and performed ground resonance and stability tests with the stability control augmentation system (SCAS) on and off. “The SCAS is used in the autopilot. It senses changes in load and direction and restores the parameters the aircraft was being controlled to,” Stromberg explained. The dual-redundant system is supplied by French-based equipment company Safran.

The first test helicopter has explored safety of flight and envelope expansion, Stromberg said, including trials at mid center of gravity (c.g.) gross weight, aft c.g. light and aft c.g. heavy. “We have flown as fast as 172 knots and to an altitude of 20,000 feet,” he said.

Bell officials expect the 429 test fleet to log 1,500 hours aloft by the time the helicopter receives certification. Transport Canada and FAA certifications are now pegged for next April. “This is an internal schedule, as our commitment to our customers is in September 2008,” Stromberg said.

He acknowledged that Bell had encountered some design issues with the flight control actuation system, which was developed by sister company HR Textron. Stromberg said those issues were corrected before the components were delivered to Bell. “The system installed in the current flying aircraft is functioning as intended,” he said.

Stromberg said the Pratt & Whitney Canada PW207D1 turboshaft is performing “very well, as expected.” It is fitted with a single-channel fadec. The PW207 also powers the Bell 427 and the MD 900 Explorer.

The maximum altitude for hover out of ground effect is now 9,300 feet, but Stromberg expects that number will probably increase to 11,000 feet.

Rotor Blades Chosen
Earlier in the program, engineers had indicated they had another tail-rotor design in case the four-blade version was not sturdy enough. The 429 is Bell’s first application of a four-blade tail rotor on such a small helicopter, and engineers were concerned about stability. According to Bell, however, the tail rotor is performing as expected and the flight loads are as predicted.

Separately, the new helicopter is now flying with its production main rotor blades. They replace the prototype blades that supported the first flight on February 27.

The aircraft is currently at 7,000 pounds max takeoff weight. “We are meeting all the weight guarantees we have made to customers,” Stromberg said. Nevertheless, the company has a weight optimization program planned that could shed some pounds from the helicopter’s empty weight. According to Stromberg, “This program will begin after we complete the envelope expansion and identify any potential required design changes from flight test,” he said.

At 7,000 pounds, the Bell 429 is at the upper limit for Part 27 certification. An increased gross weight variant would fall under the more stringent Part 29 rules. However, most of Part 29 is additional category-A IFR requirements, and the 429 already meets most of these. Part 29 certification would also require additional tests, such as windshield bird strikes.

The Bell 429–including the single-pilot IFR package–is priced at $4.865 million. Bell has received firm orders for 189 and commitments for another 40. The cockpit features a single-pilot IFR suite, with two-pilot IFR equipment available as an option. The navcom system is a Garmin GNS 430 with WAAS capability. The Garmin GNS 530 is an option. There is a mode-S transponder. A three-axis autopilot is standard; a four-axis version is optional.

Bell 429 by the Numbers

Max takeoff weight: 7,000 pounds

Empty weight: 4,300 pounds (including single-pilot IFR)

Standard fuel capacity: 215 gallons (U.S.)

Maximum level speed:  142/147 knots with skid/wheel gear

Hover in ground effect ceiling (ISA): 12,000 feet

Hover out of ground effect ceiling: 9,300 feet

Range (long-range cruise): 350 nm

Endurance: 2.25 hours

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