Product Focus: Pilatus’ Big Switch

Based on its experience of fielding more than 250 aircraft by mid-1999, Swiss-based Pilatus Aircraft decided, in 2000, to redesign the cockpit of its single-engine PC-12 turboprop. The redesign included moving some switches to new panels, but in a number of cases, involved converting rockers to toggles or push-button switches, as well.

Pilatus had learned that the single-pilot, IFR-certified aircraft’s initial cockpit design did not lend itself to dual-pilot operations. Certified in 1994, the turbine-powered PC-12 initially competed against piston twins flown by single pilots, along with the two other turboprop singles on the market, the Socata TBM 700 and the Cessna Caravan. Pilatus was so sure that most of its PC-12s would be flying in single-pilot operations that it offered copilot instruments only as an option.

But as more corporate flight departments began replacing older King Air twin turboprops with the more fuel-efficient and roomier Pilatus, more insurance companies began demanding dual-pilot operations regardless of the PC-12’s certification status. Charter companies picked up the Pilatus, as well, and some of their customers insisted on having two pilots up front.

Focus on Series 10

By the time Pilatus was ready to tackle the dual-pilot-friendly cockpit redesign, the PC-12 already had gone through nine "series" changes. The new series 10 cockpit, introduced in mid-2001, became the hallmark of the PC-12. Switches were a primary focus of the redesign.

"Some of the switches in the series 1-through-9 aircraft could only be reached from the left seat," says Ignaz Gretener, Pilatus Aircraft’s vice president of general aviation. "The reason to move switches to a more central location [in the series 10] was to keep the single-pilot capability but enable a second pilot to reach these switches when needed."

The team moved a whole bank of rocker switches, located on the left-side instrument panel in the series 9, to the overhead panel centered between the two pilot seats in the series 10. A number of these switches–including the starter, ignition, fuel pumps and cooling/heating systems–had been located directly behind and to the left of the captain’s yoke in the series 1-through-9 aircraft, well out of the copilot’s reach. The captain’s right subpanel, which still buried several switches behind the yoke, contained external lighting rocker switches, a half-dozen deicing rocker switches, and the gear position handle and indicator lights. The overhead panel in the series 1-through-9 aircraft had contained only items related to the electrical system, such as generator and battery on/off rocker switches, and the avionics master switch.

Most Changes Overhead

In the series 10 the captain’s left subpanel contains only a new electronic locator transmitter (ELT) on/armed/test/reset toggle switch. The captain’s right subpanel contains a few of the rocker switches from the series 1-through-9 left subpanel that did not get moved to the overhead panel, including the electronic flight instrument system (EFIS), emergency power system (EPS), and attitude and heading reference system (AHRS) two- and three-position rocker selection switches. The gear handle and up/down indicators remained on the extreme right of the captain’s right subpanel, which also received several optional indicator lights.

Pilatus gave the overhead panel the most serious attention. Requiring a complete redesign, the overhead panel now hosts test, external lighting, fuel pump, starter, ignition, deicing and heating/cooling switches, in addition to the electrical switches that already had occupied the panel.

Rocker switches are conspicuously absent from the overhead panel. All of the electrical power management rocker switches from the series 1-through-9 overhead panel changed to toggle switches. According to Gretener, this change allows pilots to more quickly recognize the switches’ current positions.

In addition, all of the rocker switches that moved from the subpanels became push-button switches. Many became double-detent push-button switches, lighting up an arrow to indicate the selection (heavy vs. light, or high vs. low, for example). One press engages the first selection, a second press disengages the first and engages the second, and a third press disengages both selections.

Going ‘All Black’

One of the most profound changes from the series 9 to the series 10 cockpit was the move to an "all-black" cockpit for the central advisory and warning system (CAWS) annunciators. "In the series1-through-9 CAWS, some status indicators stayed on all the time," Gretener says. "We changed to an `all black means everything is OK’ concept. This makes it easier for the pilot [to see when something’s wrong.]"

In addition to blacking out the CAWS annunciators to show normalcy, Pilatus also changed the colors of some of the annunciators when they did need to illuminate. Whereas the series 1-through-9 CAWS indicators ranged from red to orange to green to blue, the series 10 used only three colors, and blue was deleted from the mix. Red is used to indicate serious problems, such as engine fire, low oil quantity, low battery voltage and low cabin pressure. A number of CAWS indicators glow orange when their corresponding fault occurs. Green shows good operation of items that are not normally on, such as the fuel boost pumps, autopilot/autotrim, deice boots and passenger oxygen system.

Some changes requested by owners and pilots couldn’t wait for the 2000 redesign. After producing just over 100 PC-12s, Pilatus converted the rocker engine instrument system (EIS) test, fuel reset and menu switches to push-button switches. These switches also moved from the rocker bank surrounding the captain’s yoke to an area closer to the EIS digital gauges.

Added White Light

Another interesting change before the series 10 redesign, although not a switch change per se, was the addition of three white lights to the trim indicator. The three-part indicator, which incorporates pictorials of aircraft in various positions to indicate aileron, rudder and stabilizer trim, had shown only the position of the trim via white graduated dials and electronically positioned pointers on the basis of input signals supplied by the trim actuators.

The new version of the trim indicator, however, uses a white light on each dial to indicate when the autopilot positions the corresponding surface. While all three dials have white lights installed, some autopilot installations only activate the elevator and rudder trim; on these the aileron autotrim light is nonoperational.

Not everyone who switched from the series 1- throuigh-9 cockpit to the series 10 appreciated the changes. "Some pilots who were used to the old cockpit had some issues with the new design initially," Gretener says. "Pilatus responded to these issues, and we introduced modifications, as requested."

Transition `Not Bad’

One of the issues with the cockpit redesign regarded the change in the workflow. The series 1-through-9 cockpit kept all of the switches in front of the captain, creating a good flow for single-pilot operations. Placing the starter, ignition and other switches on the overhead panel disrupted that workflow and required more coordination for two-pilot crews.

"It definitely affects the workload," comments Randy Schneider, former chief test pilot for Colorado-based Pilatus Business Aircraft. Before leaving the company in mid-March, Schneider had accumulated more than 3,500 hours in various Pilatus aircraft, with 100 percent of that time in two-pilot operations.

He said that transitioning from an earlier series to a series 10 should not be difficult, depending on the experience of the pilot. "Once you get used to [the new workflow], it’s not bad. It’s like using different radios."

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