Show or Hide

Watts Radiant | Floor Heating & Snow Melting

Case Studies

Vintage aircraft restoration project

Smart Hydronics helps Carry the Torch for Connies

The once regal Super Constellation Starliner, the legendary luxury aircraft designed by Howard Hughes and built by Lockheed Martin, appears like an oversized model in a cavernous hangar at the Auburn-Lewiston airport in Maine. A team of experts, working like surgeons around a (radiantly-heated) operating table, are bringing it back to life.

The idea of restoring a Constellation entered the radar screen at Lufthansa Airlines around 2003. Ultimately, the German firm bought three of the last remaining airplanes, not a one of them in good condition.

Though hundreds of Constellations were manufactured by Lockheed, only 44 of the magnificent Starliners - considered by some to be the grandfather of luxury air travel - were built.

For the past 18 months, with many more months to go, a team of restoration experts have been at work on the one plane in the middle of it all. The Starliner’s carcass rests on wooden risers in the center of the hangar. Initially stripped bare, down to its metal skeleton, lines of green primer now cover seams and rivet rows between aluminum panels.

Recreating an era

Lufthansa has a penchant for rebuilding old planes. And through the years the Lufthansa Technik division has proven that it can be profitable business. Pilots and aviation enthusiasts around the world are eager to pay large sums of money for new experiences aboard vintage planes, enough so that Lufthansa expects to recover its $30+ million investment, once the plane is airworthy - in just six years.

The Starliner, introduced in 1956, was the last of many Constellation versions Lockheed built over a period of 16 years. The Constellation was the last, great prop-engine passenger plane to carry passengers across the Atlantic Ocean. Its ultimate demise was borne out as faster jet engine aircraft won public interest. Its departure marked the passing of a great era in aviation.

Lufthansa referred to its Starliner as the "Super Star." It flew the longest-duration scheduled flight ever, a 23-hour-19-minute trip from London to San Francisco - a trip that jets cover in less than half the time.

The standard Starliner carried 86 passengers, but the swankier version carried just 30 high-flyers in supreme luxury, complete with partitioned sleepers, a lounge serving draft beer and mixed cocktails, in-flight entertainment and an onboard chef.

For the team: a European comfort solution

When the experts at manufacturer's rep firm, Emerson Swan, and their wholesaler partner F. W. Webb, got wind of the project, they helped design a system that would hydronically heat the airplane hangar's high-mass concrete floor.

"An airplane hangar is perhaps the ultimate use of radiant heat," said Jim Simas, regional sales manager for Emerson Swan. "With giant, open areas, it's no place for forced air heat; in the winter, BTUs would be flushed out fast with the opening of the big bay door."

The construction project began in 2008. According Simas, the big hangar was divided into two main radiant zones and a much smaller one to serve a long, narrow snow-melt zone that extendeds six feet beyond the huge sliding doors of the building’s airplane-sized opening.

With the mechanical room placed in one corner of the building, it made sense to run a 1-1/2-inch extended injection bridge to the manifold on the furthest side (with about 250-foot supply and return feeds), and a 50-foot, two-inch PEX line-set to feed the nearest manifold.

According to the chosen hydronic systems installer, Al Hill, Al Hill Plumbing, based in Sabattus, ME, they used oxygen-barrier RadiantPEX tubing and stainless steel radiant manifolds manufactured by Watts Radiant.

Each of the two large manifolds for the main area supplies warmth to twenty-four 400-foot, 5/8-inch PEX loops spaced on 18-inch centers in the main floor of the hangar. Spacing is snugged closer at nine-inch centers near the exterior walls and the snowmelt apron.

Two gas-fired boilers feed 180°F water out to the manifolds. Return fluid temperatures typically reenter the primary/secondary piping at about 80°F. "With return temperatures like that, each gallon delivers between about 40-50K BTUs," said Simas.

"One design that was initially considered delivered a 20°F Delta T," explained Simas. "But cost was the major obstacle to building the system to accomplish it. Our alternate plan - which brought the price of installation down substantially - won approval and worked marvelously through its first winter, even when ambient temps dipped well below zero."

According to Simas, the initial design called for a greater number of pumps and massive, two-and-a-half inch copper lines suspended overhead to feed remote manifolds with a flow of 37-1/2 gallons a minute each. That, for just half of the building. "The pumps for the initial plan needed to be large enough to move much larger fluid volumes up, and through 1,000 or more feet of large supply and return piping… plus all of the raiant heat tubing," he said.

Ultimately, the cost of installation labor, hangers, lift rental, larger mechanical components, including the high horsepower, three-piece pumps, and giant copper "runway" (at $18/ft.!) pushed the building owner's decision toward Hill's more reasonable approach. That was the genesis of the 100°F Delta T solution.

"The plan we settled on saved a huge amount of money on the cost of the system and in energy consumption as well," said Hill. "The 'extended injection bridge' concept called for the mixing of fluid temperatures at the manifolds and outside the mechanical room."

"Radiant is the only heat that allows such flexibility because the design temps are low and we take advantage of the larger delta’s to mix water," added Simas. "When combined with simple injection style controls, a system like this delivers modulated water temperatures to the radiant manifolds to prevent overheating. At the same time, it protects the boilers from thermal shock and flue gas condensation. It's a plan that worked especially well for Lufthansa and the Connie's project."

In its wake

Who could've guessed that an old plane, brought back from the dead, could make such a big impact internationally, and locally, too. In its wake will remain a fine facility to serve the community of Auburn, Maine. And whoever has the good fortune of working there, the miracle of modern hydronics will keep 'em comfy all winter long.


Auburn, Maine

Radiant Systems Installer

Al Hill Plumbing


RadiantPEX, Stainless Steel Manifolds

Manufacturer's Representative

Emerson Swan

  • Home
  • Solutions
  • Case Studies
Back to top