DynCorp's Global Eagle upgrade is proving the Huey's ability to carry heavier weights at higher altitudes.
THERE'S A LOT TO BE SAID FOR BRUTE FORCE. NO
inching forward until you hit translational lift. No delicate control touch or PPT (perfect pilot technique). No praying you can get it airborne while ignoring the low-RPM warning horn. Just pure, raw, unadulterated power--which is precisely what is being offered with DynCorp's new Global Eagle, a re-engined UH-1H Huey.
The Global Eagle is already in service with two government organizations. The Georgia Forestry Service took delivery of its first aircraft a year ago and has budgeted the funds to convert another UH-1H into a Global Eagle during Fiscal 2007. The U.S. Border Patrol received its first Global Eagle early this year and has stated a requirement for nine additional aircraft, although it has not worked out the funding details.
Apparently, the aircraft is performing even better than promised. Mike Leverette, chief pilot for the Georgia Forestry Service, said "the package they sold us turned out to be even better than promised." DynCorp had guaranteed a 15-percent savings in fuel, which in fact turned out to be a 20-percent drop, Leverette said. "While a regular Huey will burn about 625 to 650 lb. per hour, the most we've gotten this to burn is 500 lb. per hr. And that is at max gross weight, hovering out of ground effect. As for tail-rotor control in tail winds or cross winds, the increase in tail-rotor authority is so large that I can't even quantify it. It's like it's not even a Huey any more for both power and tail-rotor authority."
DynCorp's Global Eagle has only two non-standard Huey parts. The first is the upgraded engine, going from the Honeywell L-53-L-13B to the Pratt & Whitney Canada PT6C-67D, providing a power increase from about 1,300 to 1,675 shp. DynCorp said it expects to further increase the shaft horsepower to 1,790 shp. with new software.
The second change is a new tail-rotor kit that moves the rotor from the left side to the right, making it a tractor, or puller, style rather than a pusher-style anti-torque system.
A strake, developed by Boundary Layer Research. is also added to the left side of the tailboom to provide additional "lift" to the right. The strake causes the down wash from the rotor blades to break up as it passes over the port side of the tailboom, creating a low-pressure area on the starboard side of the boom. This provides a 40-percent increase in available tail-rotor authority and a 47-percent increase in payload range over the UH-1H. The Global Eagle can carry up to 3,000 lb. almost 300 mi. at maximum gross weight, taking off and hovering out of ground effect at 4,000 ft. and 95F., according to DynCorp figures.
The Global Eagle program started in 2000 when the U.S. Border Patrol came up with a request for a more efficient engine for the UH-1. Jimmie Ellis, vice president, worldwide technical services for DynCorp., said Pratt & Whitney Canada felt the PT6-67 would work on the UH-1. It then hired Arlington, Texas-based Global Helicopters to do the design, tests, engineering and certification of the aircraft. DynCorp was invited to join the team as manufacturer of the transformation kit, as well as to do the installation and provide aftermarket support.
"As we got further into the program, PWC realized that they were getting a little bit out of their league, so they approached us and asked if we would take the lead on the program, letting them fall back and become the engine supplier," Ellis said. In 2003, DynCorp becoming the prime contractor.
If a customer wants a Global Eagle and already has a UH-1H to convert, the price will be less than $1 million, Ellis said. "Without a UH-1H, it would depend on what the customer wants, including avionics. If we zero-timed it, it would be about $1.5 million."
Several options are offered for the cockpit upgrade, with the engine controls set up to adapt to a health and usage monitoring installation if the customer wants it, allowing them to plug into a laptop to download information from the engine, he said.
A Global Eagle Huey delivered to a customer arrives with a five-year, 2,500-hr. engine warranty, "and the FAA gave us a 5,000-hr. TBO on the gearbox," Ellis said.
To promote the Global Eagle, DynCorp took it on a demo tour in August, including a stop at Lake Co. Airport, Leadville, Colo., the highest airport in North America at 9,927-ft. altitude. Rotor & Wing was invited to fly the aircraft there to experience its ability to operate at full max gross weight even under hot and high conditions.
The day of the flight was a perfect, blue-sky day with light puffy clouds and a very comfortable 60F, giving us a density altitude of 11,700 ft.
I was flying with Rod Marchant, director, North American sales and chief pilot for DynCorp, who noted that starting the Global Eagle is just like starting any Huey--with one exception. As with any Huey, on the first start of the day you have to leave it in engine idle until everything has warmed up, then roll in full power. However, the Global Eagle has an electronic engine control (EEC) that allows a modulated start, so for subsequent starts, as long as the reduction gear box gauge registers 20C. or better, you can continue rolling on power to 100 percent. However, even the initial start restriction is being evaluated and may come off, Ellis said.
Once the engine was started, Marchant pointed out the density-altitude compensator gauge that automatically measures density altitude and indicates the compensator is working. As the density altitude increases, the compensator automatically changes tail-rotor pitch to achieve maximum efficiency for that altitude.
Another "automatic" is the EEC, which operates essentially like a full-authority digital engine controller (FADEC). However, if the EEC fails, it does not default to another setting. The fuel control remains exactly where it was at the point of failure. This allows the pilot time to assess the situation. "If you are coming out of a hover hold with a bucket of water and you lose your EEC, you can handle it," Marchant said. "It stays exactly where it was, so that now you are on manual throttle and you just roll it on as you pull it in. Whatever power setting you had, that is where it stays."
After a few minutes of hovering around, we took off and Marchant pointed me toward a mountain knob that stood at just under 11,000 ft. and told me to bring it to a hover out of ground effect. With a full load of fuel, but no payload, we hovered at 250 ft. AGL with over 10,000 ft. pressure altitude and 12,000 ft. density altitude, pulling only 31 lb. of torque. We also did pedal turns, putting the tail into the wind without any appreciable impact on tail-rotor authority. The pedals stayed virtually neutral, or as neutral as a Huey's pedals ever are, during the entire exercise.
Only when lifting off with a full water bucket was there a need to put in any kind of left pedal, and that was minimal. Marchant noted that the density altitude compensator essentially provides the same amount of tail-rotor authority as you climb from 4,000 to 14,000 ft.
Its Greatest Asset
This density-altitude compensation, combined with the more powerful engine, is what gives the Global Eagle its greatest asset--the ability to operate at max gross weight at high altitudes at high temperatures.
For the water bucket demo, we flew over to Turquoise Lake, which sits at 10,000 ft. The Global Eagle has a strain gauge on the console that shows how much weight is on the hook, which indicated around 2,200 lb. as we lifted up from a hover with a full bucket, putting us right at max gross weight of 9,500 lb.
Still, at about 12,000 ft. density altitude, we were able to lift off, achieve translational lift, fly a pattern around the lake, drop the water, then go in for another bucketful and never have a drop in rotor rpm.
Although the PT6C-67D could be converted to other UH-1 models, that would require getting a supplemental type certificate, and with more than 1,000 UH-1Hs still flying, there is no great effort on DynCorp's part to go to the expense of getting those STCs. DynCorp does, however, plan to expand the Global Eagle program into other aircraft. "We are already looking at the 205A1, the civilian version of the Huey in a standard category," Ellis said. "We can provide the standard-category version with the modification. That is important because people who have U.S. Forest Service firefighting contracts like to be able to carry passengers, so the standard category is important to them. So when we finish this program, we will have covered everything from the restricted category to the standard category and there will be an option for everyone."