Single-pilot IFR with a computer for a copilot
For most pilots flying in the soup, the most satisfying moment comes when the clouds whisk away to reveal the runway. This is one of flying's little pleasures that the majority of civilian helicopter pilots rarely experience. Since the real usefulness of a helicopter is in landing at places other than airports, and given the high cost of IFR certification, instrument helicopter flying is often considered impractical. Times may be changing, however. Helicopters are more reliable than ever; also, with the advent of GPS, hospitals and corporations can inexpensively acquire instrument approaches to their heliports.
Manufacturers are anticipating the demand by offering IFR packages with autopilots. Although an autopilot is required for helicopters to receive single-pilot IFR certification, designing one to handle the complexity and responsiveness of a helicopter effectively is a considerable challenge — especially for some of today's sophisticated helicopter designs.
For example, the McDonnell Douglas twin-engine Explorer, powered by Pratt & Whitney PW206A engines of 640 shaft horsepower each, takes advantage of several new and innovative technologies, including a highly responsive five-blade composite rotor system, NOTAR (no tail rotor) anti-torque system, and the newest full authority digital engine control (FADEC) system. Football fans will remember this helicopter as the one that flew singer Diana Ross out of the stadium during Super Bowl XXX.
McDonnell Douglas teamed up with AlliedSignal Aerospace (which started building autopilots for Bell Helicopters in 1988) to design and produce the Explorer's single-pilot IFR package. In a switch from tradition, AlliedSignal is also doing all the certification work, including the flying. This arrangement has worked well because Lloyd Bingham, AlliedSignal's chief test pilot, was able to contribute practical input to the design. For one thing, he had the GPS receiver moved to a higher position on the panel for better viewing by the pilot.
The Explorer's installation is built around the Bendix/King KFC 900 flight control system. This package has a complete stability augmentation system (SAS), autopilot, and an optional flight director. The KFC 900 uses solid-state digital design and complete integration with the flight control system to produce smooth and accurate control movements.
Arranged on a T-style panel is a four-tube electronic flight instrument system (EFIS). The pilot and copilot each have two 4-inch-square display tubes with the electronic attitude director indicator (EADI) positioned directly above the electronic horizontal situation indicator (EHSI). The panel also includes a KLN 90B approach-certified GPS navigation system, communications and navigation radios, and a transponder. Available as an option are a color weather radar and a VHF/UHF radio.
The price of the panel is $525,000 (no, that doesn't include the helicopter — it goes for about $3.2 million), and it takes 235 pounds from the Explorer's useful load of 2,565 pounds. To save weight and cost, the copilot's EFIS system can be downgraded to a standard attitude and heading gyro package ($435,000 and 205 pounds) or eliminated altogether ($420,000 and 190 pounds). The company estimates another $60,000 for installation.
AlliedSignal modified the Explorer's dual-generator electrical system to meet the redundancy requirements for IFR certification. The system is designed such that if one generator fails, the other one will automatically power the entire system and the pilot need only monitor the load. Should both generators fail, the pilot can switch to battery power that will not only provide the required 30 minutes' power for the standby attitude indicator, but the full EFIS system, as well (an idea that came from Bingham).
Since I had never flown the Explorer, Bingham gave me a quick introduction to the helicopter. McDonnell Douglas has done a good job of simplifying and automating many of the Explorer's flight procedures, including engine starting with the FADEC. I turned the number one engine control knob to Idle and monitored the fully automated start on a graphical display screen. After starting engine number two and turning all the systems on, I moved the engine control knobs to Fly and was ready to lift off.
In flight, the Explorer has a responsive, yet comfortable feel. The cyclic grip has a different look; it's connected to the control tube at the top of the grip. One nice feature is the pitch sync switch located on the collective control (another feature that Bingham wanted); when pressed, it moves the horizon line to reflect level flight regardless of the helicopter's pitch attitude, up to plus or minus 9 degrees. This is useful because in cruise flight the Explorer flies 7 degrees nose low. The FAA has allowed pitch sync switches in airplanes but has been reluctant to certify them in helicopters.
When it came time to demonstrate an ILS approach, Bingham instructed me to trim the flight controls and switch on the autopilot. Next I engaged the flight director, set the altitude at 3,000 feet, and spun the heading bug around to 85 degrees. We were now heading to the ILS Runway 35 approach at New Century Airfield in Olathe, Kansas, with a 38-knot tailwind and a 95-degree intercept angle. The system is limited to a maximum intercept angle of 105 degrees on front course approaches and 74 degrees on a back course.
About 15 miles south of the airport we approached the localizer and the Explorer began turning to intercept the beam. The system defaults to a 20-degree bank angle, although the pilot can change it to 10, 15, or 25 degrees. As expected, the tailwind and high intercept angle caused the helicopter to fly through the localizer. With undaunted precision it reestablished itself on a 10-degree intercept angle and captured the localizer about 12 miles south of the airfield, holding a 15-degree wind correction angle.
At DUSTT intersection, the autopilot captured the glideslope and began lowering the helicopter's nose to increase the descent rate. At this point, I lowered the collective control to regulate the airspeed. Bingham explained that helicopter autopilots do not manipulate the collective control because there isn't enough customer demand for automatic collective control to justify the added cost.
At 100 feet agl, the flight director switched from glideslope tracking to the radar altimeter and tracked the localizer down the runway centerline at 50 feet agl. However, the flight manual states that this is intended for flight in VFR conditions only.
Although the system performed quite well, should it fail during actual IMC, a single pilot would need to focus on flying the helicopter. The workload in flying a helicopter on instruments is so high that pulling out maps and flipping through approach plates is essentially impossible. With this in mind, many operators and pilots still prefer two-pilot crews but like having the option of going single-pilot if necessary.
AlliedSignal's autopilot is highly sophisticated. It has numerous display options, including 360-degree and 85-degree compass roses and a moving map. It will take some time to learn the system well; yet, for the helicopter pilot who masters it, a world of simple pleasures awaits.
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