Twin Commanders are at their best when flying high and fast. The National Oceanic and Atmospheric Administration (NOAA) has long known that they also do a pretty fair job of flying low and slow.

NOAA has been operating two 500S Shrike Commanders for about 30 years, and in 2005 replaced a 690A with a 695A Model 1000 JetProp. The primary mission for the Twin Commanders is airborne snow surveying, which involves flying low and slow to electronically measure snow water equivalent (the depth of water that would cover the ground if the snow cover was in a liquid state). The data is used to predict stream flow and potential flooding when the snow melts in the spring. NOAA has been doing airborne snow surveys since 1978.

“The high wing is one reason we’ve had Commanders from start,” explains LCDR David Demers, chief of the agency’s airborne snow survey program and one of several NOAA pilots who fly the missions. In addition to great visibility, the Commanders have “really good slow-flight characteristics,” Demers says. “We get up in a lot of valleys, and we never know if we might have to turn around.” The ability to maneuver the Commanders at slow speeds gives pilots the confidence they need to do the job.

noaaFrom November through May each year NOAA conducts airborne snow surveys in 31 states and seven Canadian provinces subject to significant snowfall, including remote mountainous regions where the Commander’s attributes really shine. A typical mission in the Rocky Mountains or Alaska may start out in a high valley anywhere from 8,000 to 12,000 feet MSL and proceed down slope to either the snow line or to a predetermined end point.

LOWER AND SLOWER

The airplane is flown at about 500 feet AGL and from 100 to 130 knots ground speed. (Pilots have to disable the Terrain Awareness and Warning System when flying snow survey missions.) Even lower and slower would be better for the electronic instrumentation that “reads” the snow pack, but safety dictates a more conservative flight profile.

NOAA pilots follow some 2,000 designated “flight lines” on their snow surveys, with each flight line typically 10 miles long and 1,000 feet wide.

Loss of power when operating close to the ground at low indicated airspeeds and often with flaps partially extended is an obvious concern for NOAA pilots, but it is less of a concern in the Commander. “The 695A with Dash 10 engines certainly doesn’t lack for power,” Demers says. “Even on one engine it is no problem. If something were to go wrong, just put the power in and get away from the ground.”

The depth of snow pack can be measured easily enough, but snow can be heavy and wet or light and fluffy so depth is not a good indicator of how much water will be released when the snow melts. Knowing the water equivalent of snow pack is important, especially out west where snowmelt accounts for 80 percent of the water supply. It’s also critical information for anticipating flood areas.

The water equivalent of snow pack is measured using gamma detectors composed of sodium iodide crystals. Five crystals, each weighing 50 pounds, are carried aboard the Commander in detector packs. “Four of the crystals look down and one looks up,” Demers explains. “Natural terrestrial radiation given off by earth comes up and hits the sodium iodide crystals.” The crystals convert the radiation to an electric signal. The result is a Geiger counter-like measurement of radiation.

By comparing the attenuated radiation measurements from snow-covered terrain with benchmark measurements of the terrain with no snow cover (gathered in September and October each year), scientists can determine the extent of the water in the snow pack with accuracy of about one centimeter. That information is used by the National Weather Service to predict stream flow and potential flooding.

The gamma detectors can measure up to about 39 inches of water equivalent in snow pack. “That’s a lot of snow!” Demers says.

NOAA’s snow survey program is based at the National Operational Hydrologic Remote Sensing Center in Chanhassen, Minnesota, near Minneapolis-St. Paul. The 695A and one of the Shrikes is based at Flying Cloud Airport in St. Paul. The second Shrike is based at McDill Air Force Base in Tampa, Florida.

The Tampa-based Shrike had been assigned to photogrammetry work in support of FAA aeronautical charting activities, but today it is used for marine mammal surveys and as a backup for airborne snow survey work.

Eagle Creek Aviation in Indianapolis refurbished the 695A for NOAA when the agency acquired it from the U.S. Drug Enforcement Administration, and Eagle Creek continues to maintain it for NOAA.

Demers cites one more reason why the Commanders are ideally suited to the snow survey mission. “Just try to get 450 pounds of gear up a flight of stairs,” he says. “The Commanders make sense on a lot of levels.”

One feature in particular makes the Twin Commander a superb platform for aerial observation missions—visibility. A high wing and engines and propellers that are positioned well aft of the cockpit and, on all but 695 models, sweeping panoramic windows on each side of the passenger cabin afford unparalleled views below and around the airplane. Visibility is the Twin Commander’s trump card when it comes to observation duty. But if the job calls for the use of belly-mounted cameras and sensors, all airplanes would seem to be created equal. If that’s the case, why does Rob Barnett chose to fly Twin Commanders for data-gathering missions?

Barnett1 “The Commander makes a great airplane for survey work, no doubt about it,” says Barnett, co-owner of Centerline Aerospace. Centerline operates a 690A and a 500 piston twin, and is buying a straight 690. All are dedicated exclusively to collecting data using a variety of electronic sensors and conventional cameras.

“We’ve looked at others—the Piper Chieftain and Cheyenne, and Beech King Air, for example—but the Commander’s power-to-weight ratio, payload, speed, stability, and efficiency are the best. It’s a fantastic airplane, really. In heavy turbulence the ride is much better than in a low-wing airplane. It doesn’t yaw as much, or oscillate. It’s great for hauling equipment, too—you don’t have to walk around the wing all the time to load and unload, you just go under it. The wing makes for a good umbrella in the rain, too. When you live in an airplane you’re kinda particular which one it is.”

Centerline is contracted by various companies, governments, and agencies around the world, including the National Oceanic and Atmospheric Administration (NOAA) and the U.S. Army Corps of Engineers, for a wide variety of survey missions. They range from mapping the sea floor and adjacent beach grade, and measuring the moisture content of soil, to photographing all of downtown London to identify potential cell phone tower sites.

The specific equipment used for a mission depends on the data being gathered. For example, to map the sea floor and adjacent beach, the 690A carried a blue-green laser that penetrates the surface of the sea, and also a more conventional invisible infrared laser to scan the beach area.

barnett2 The mapping was done at an altitude of 1200 to 1400 feet above the surface, cruising at 155 knots groundspeed. Those low, often-turbulent altitudes are where the Twin Commander really shows its ride and visibility advantages, according to Barnett. “When you are down low and maneuvering a lot, you really need a good view,” he says.

Barnett, who is both a pilot and mechanic, typically operates with an observer, although on occasion a third and even fourth person will be aboard for training or observation. The observer establishes a grid pattern for the pilot to follow. The 690A is flown with the autopilot engaged, although it is not slaved to the GPS grid pattern. As the airplane rolls into a turn, the expensive gyro-stabilized sensors also roll to maintain a level perspective.

The sensors are controlled by a highly sophisticated inertial reference system that is capable of maintaining vertical accuracy of 2 cm, according to Barnett.

The 500 does not have an autopilot, so missions are hand-flown. On data-gathering runs turns are made with minimum roll by skidding. “Once you get used to it you don’t have to skid much because you’re already using a wind-correction angle,” Barnett explains.

The 500 is equipped with a passive microwave radiometer that can “see” 30 feet below the surface to map soil moisture. The device is used to, among other things, look for leaks in pipelines and levies.

The airplane also has a Midas Pictometer system that uses five cameras—one pointing down and the other four pointing out into quadrants. The effect is to reduce the “leaning” look to outlying buildings that results from the use of conventional cameras that only look straight down.

Centerline’s Commanders are flying in excess of 400 hours a year, and that is expected to go to 700 hours or more when the 690 is brought on line. One of the airplanes will be assigned primarily to NOAA and the Corps of Engineers, according to Barnett. Other jobs will take them to Australia, Southeast Asia, France, Spain, and Portugal.

It’s a nomadic existence, but Barnett, who lives in England, flies for two weeks and then has four weeks of ground-based duties and time off. A second pilot flies for four weeks, followed by two weeks off.

Given Centerline’s far-ranging destinations and intensive schedule, maintenance is a key issue. Barnett uses Legacy Aviation west of Oklahoma City for parts and for inspections and maintenance on the 690A. “The mechanics do a good job, and they give us fair deal on parts,” he says. “We can call them day or night for parts and know they’ll be shipped out. There’s a lot of trust there. They get a gold star.”

In business, when you find something that works, you stick with it. Jim Schwertner has stuck with the cattle trading business his father, Eugene Schwertner, founded in 1946, and today the Schwertner, Texas-based company is one of the largest livestock dealers in the nation.

Schwertner also has stuck with one of the tools that has helped him grow his cattle business—a Grand Renaissance Twin Commander.

Ten years ago Schwertner was looking to buy a new airplane. He surveyed the options and came to the conclusion that a Grand Renaissance Twin Commander was faster, more economical, and less expensive than the factory-new competition. “I felt like I was getting a new airplane,” he says.

After 1300 hours of flying it, he’s convinced it’s still the right choice today. “The reason I’ve kept it is because it’s such a good tool for me. A lot of the places I go are in rural areas with 3000- to 4000-foot strips, and no air carrier service within 300 or 400 miles. The Commander is almost as fast as Citations and other light jets, and burns a lot less gas. For what I do it’s perfect.”

“This airplane was built right,” Schwertner says, “and the Dash 10T engines are very reliable.” The airplane is maintained by Legacy Aviation at Clarence E. Page Municipal west of Oklahoma City. “They do an excellent job. They know the airplane. Some of the guys who work there built it. And I appreciate that the factory [Twin Commander Aircraft LLC] is supporting the Commander line.”

Schwertner is sticking with his Grand Renaissance. “I plan on keeping it awhile,” he says. “Every time I look at the alternatives, it still looks like the best.”

Gene Good has been flying Twin Commanders for two decades in support of Golden Giant, his Kenton, Ohio-based metal-building manufacturing and erecting company. He has logged more than 4,000 hours in the two he has owned. “The aircraft is a major tool in my business,” he says. “They have helped build the business, no question about it.”

In 2000 he traded his Dash 10T-powered 690B for an Eagle Creek Aviation Services-built Grand Renaissance 1000. Five years later he had Eagle Creek install Meggitt EFIS and electronic engine instrumentation displays along with a Meggitt 2100 Digital Flight Control System, and certify the Grand Renaissance for RVSM operations above FL290.

“I probably average on the north side of two-hour legs on my flights, although some go three-and-a-half hours or more,” Good explains. “I regularly see 300 knots true airspeed and 76 gallons per hour block-to-block fuel consumption.”

His business flights often range to the Atlantic and Gulf coasts, where he sells and erects dry-rack boat-storage buildings. He also owns a home in Ft. Myers, Florida, that he and his wife travel to often. There was a time when Good felt a need for more speed on those longer flights. He thought seriously about buying a Cessna Citation, and worked the numbers. He calculated that the 1,000-nautical-mile flight to Ft. Myers would take 30 minutes less time to fly in a jet compared to his Twin Commander, but at more than twice the total fuel consumption. These days, that could be $3,000 to $4,000 more round-trip. Good concluded that the economic pain of flying a jet—more fuel, higher insurance premiums, and training for a type rating—would far outweigh the relatively modest gain in speed. “It makes no sense to consider another type of airplane just to gain a half-hour in time for that kind of increase in operating costs,” Good reasons.

After eight years of flying the Grand Renaissance, Good says his opinion of it hasn’t changed since the day he bought it. “I’m real satisfied with the airplane,” he says. There have been no major maintenance issues, and Good says he has never had any engine problems whatsoever. “Being a business owner, the aircraft is used 95 percent for business, and it is money well spent,” he says.

Brett Fuller flies a Dash 10T-powered 690B Twin Commander for Monte Cluck, whom Fuller calls “a savvy owner.” Why? Cluck grew up around airplanes—it was his father’s hobby, and Cluck learned to fly as well. When Cluck, a fifth-generation Texas cattle rancher and feed yard owner and operator, went looking for an airplane for the business, he put a sharp pencil to the decision and chose one that best fit the mission.

“I looked at price, speed, versatility, and safety,” Cluck says. “Nothing came back to us like the Commander did.” Cluck got some support in his decision-making from friend and fellow cattle rancher Jim Schwertner, who has been operating a Grand Renaissance Twin Commander for a decade. “He had nothing but praise for the Twin Commander,” Cluck says.

“We fly from the Texas hill country to the Texas panhandle, where the feed yard and farms are located,” Fuller explains. “The Twin Commander is perfect for that mission. It has the speed and the fuel burn you can’t beat.”

It also has the view, according to Cluck. “When we’re flying and I’m sitting back there and looking out those windows, I can almost see three days ahead of time, especially over flat west Texas,” he says. “Those big windows are fabulous!”

Fuller says the Commander is “by far the most fuel-efficient” turbine-powered airplane he has flown. “Those two Dash 10Ts burn 600 pounds total the first hour, and 500 pounds every hour after. And that’s at 290 to 300 knots true airspeed. Compare that to a King Air C90 or 200, which are slower and use more fuel.”

The airplane recently went to Legacy Aviation Services in Yukon, Oklahoma, for hot-section inspections and new Hartzell wide-chord props. “Before the hot sections and blades I was averaging 285 knots true airspeed at FL250, burning 78 gph,” Fuller says. “I would pencil in 80 gph, but it was really 78. Since the work we’ve gained about 5 to 7 knots at the same altitude and the same fuel burn. Those wide-chord blades deliver much better performance on takeoff and climb.

“Any Dash 10 conversion should go hand in hand with wide chords,” he adds. “It’s the bite those props get. The takeoff roll gets up to speed a lot quicker, liftoff comes quicker, and our climb rate has almost doubled up to 10,000 feet. Our first trip with the new blades was to Colorado Springs. It was a hot and high takeoff, but the wide-chords didn’t even think about it. We got off the ground clean and climbed well.”

Legacy also refurbished Cluck’s Twin Commander with new paint and interior, and upgraded the panel with a Garmin GNS430 with WAAS capability. The airplane is based in Kerrville, which has a published WAAS LPV approach, and “there were a handful of times I needed it,” Fuller says.

“Legacy has been outstanding,” Cluck says. “They care about what they do, the people are dedicated, and when you call you get a response. They have been wonderful for us.

“We’re really really proud of our Twin Commander,” he adds. “For the money, the speed, and the cost of operation, of the four airplanes we considered—the King Air, Cheyenne, Conquest, and Commander, the Commander is the one to own. Of those four airplanes, we have the best one. It’s the fastest airplane we’ve ever operated, and we think it has been a good investment.”