Vectored Thrust-Ducted Propeller (VTDP) compound helicopter technology is discussed in the July 2004 PROCEEDINGS magazine.
Anyone know much about this? Thx Rick
An excerpt from the second article also paraphrased in the above article:
"A production version of an H-60 compound helicopter, for example, could have an unrefueled 762-naut.-mi. combat radius when flying a rolling takeoff, or an unrefueled 520-naut.-mi. radius when making a vertical takeoff, officials said. This is more than triple the 237-naut.-mi. combat radius the HH-60H has today, but it is highly compatible with the F/A-18E/F Super Hornet's 665-naut.-mi. combat radius."
I found these two articles:
Testing Dispute Clouds New Helo
By Stanley W. Kandebo/Aviation Week & Space Technology
July 31, 2002
ESSINGTON, PA. -- Piasecki Aircraft Corp. is aiming to demonstrate that modern compound helicopter technology can significantly boost speed, range and handling characteristics of existing rotary-wing aircraft, but differences over flight-clearance requirements are threatening to sideline the program.
Under a $26.1-million advanced technology demonstration contract awarded in October 2000 by the Naval Air Systems Command, the company plans to add a lifting wing with flaperons and a vectored-thrust ducted propeller (VTDP), or "ring tail," to a Navy YSH-60F and demonstrate, in flight, some of the performance benefits the technologies could give existing helicopters.
HOWEVER, DIFFERING VIEWS regarding flight-clearance rules provided by the Navy in April are threatening to make the project more expensive than originally estimated, which could bring down the curtain before the program reaches flight test.
As a result, Piasecki (or PiAC) is discussing a plan with the Navy to conduct flight testing under rules applicable to FAA contractor demonstrations. Taking the FAA route would allow PiAC to execute the project in a rapid prototyping environment, as opposed to the more formal, engineering and manufacturing development flight-clearance process now required by the Navy. The FAA approach, initially raised by the office of the assistant secretary of the Navy for research, development and acquisition, would streamline the effort and make it less expensive, company officials said.
THE BASIC COMPOUND helicopter technology to be added to the SH-60 was first proven in trials of the Piasecki 16H-1 and 16H-1A when the aircraft were flown in the early 1960s at speeds up to 225 mph. Updated versions of that technology are planned for the upcoming tests.
PiAC officials say transforming legacy helicopters already in the fleet into compound helicopters could substantially enhance their performance. First and foremost among the improvements is speed.
Since the wing of a compound helicopter unloads the main rotor, retreating blade stall, which limits most conventional helicopters to forward flight speeds of about 150 kt., does not become an issue in compounds until about 240 kt. Compound speed also is enhanced by Piasecki's thrust-generating ring tail. The original ring tail flown in the 1960s consisted of an aft-facing propeller spinning in the vertical plane to generate thrust, and a system of vertical and horizontal louvers to direct the thrust generated by the propeller. For the upcoming demonstration, PiAC has simplified this technology. The aft-facing variable pitch propeller is still used, but yaw control is provided by a set of nested shells that form a hemisphere around the aft end of the tail when deployed, as well as by a cruciform rudder and horizontal stabilizer mounted within the confines of the tail's duct.
WITH THE RUDDER DEFLECTED to the left (when viewed from behind) and the spherical shells deployed, thrust is deflected to the aircraft's left. When thrust is needed in the opposite direction, the spherical shells are stowed against the wall of the ring tail's duct, and the rudder deflected right. The shells also are retracted during forward flight, with yaw control coming primarily from the rudder. Finite control with the compound helicopter during hover is provided primarily by the pitch of the aft propeller.
PiAC officials say the nested spherical shells have significantly decreased the amount of power needed to generate control torque during hover. "It's about 46% less when compared to the first-generation ring tail," John Piasecki said. He is PiAC's vice president of contracts.
As a measure of the speed enhancement provided by the ring tail, PiAC officials note that current H-60 aircraft are limited to about 150 kt. in forward flight. But when modified with compound helicopter technology, speeds could increase to 213 kt. for a naval version and to 225 kt. for one configured for Air Force search and rescue.
To gauge the benefits of increased helicopter speeds and agility, Army and Marine Corps pilots "flew" ring tail-configured Apache and Cobra gunships, respectively, in mock combat during the mid-1990s at Boeing's flight simulation laboratory near Philadelphia. Pilots found that the modified aircraft demonstrated substantial performance, survivability and handling-quality improvements. In fact, the aircraft were able to fly 25% faster and 17% lower than unmodified, baseline helicopters in nap-of-the-earth operations, and were able to engage elevated targets without unmasking.
One Marine pilot said the compound version of the AH-1 was tough to beat, in both offensive and defensive air-to-air combat, because of its "significant speed advantage, increased platform stability and the ability to pitch point." According to his written report, the AH-1 can pitch point momentarily, but can't maintain this attitude without losing or gaining airspeed or altitude. The modified, simulated aircraft was able to do so, while hovering, with the nose as much as 21 deg. up or 10 deg. down.
Army pilots also liked the pitch-point capability in the AH-64, reporting that "this ability to hover and point is very desirable for hover fire accuracy and pilot workload reduction. It could influence future tactics and weapon delivery techniques."
Besides air combat performance, a speed increase also would be a critical improvement to medical evacuation helicopters and to rotary-wing aircraft used for pilot search and rescue. Air Force rescue data indicate that the odds of a successful rescue are about 45% if a pilot is reached about an hour after being shot down. This decreases dramatically as time passes.
Another attribute of the compound helicopter is the lift generated by the wing. The lifting wing can offload the main rotor by 50%, which can greatly increase its life in modified legacy aircraft when operating at current takeoff gross weights.
Alternatively, the payloads of modified legacy aircraft could be boosted by several thousand pounds if current main rotor loads are maintained and the compound aircraft is allowed to make rolling takeoffs. This additional payload could take the form of troops, supplies or aircraft fuel, which could be used to boost range, Piasecki said.
A production version of an H-60 compound helicopter, for example, could have an unrefueled 762-naut.-mi. combat radius when flying a rolling takeoff, or an unrefueled 520-naut.-mi. radius when making a vertical takeoff, officials said. This is more than triple the 237-naut.-mi. combat radius the HH-60H has today, but it is highly compatible with the F/A-18E/F Super Hornet's 665-naut.-mi. combat radius.
PiAC engineers also estimate that H-60 vibration and fatigue loads could be cut, perhaps as much as 50%, using compound technology, and that these improvements would translate directly into increased safety, as well as maintenance and life-cycle savings.
Besides lift and maintenance advantages, the addition of a wing to legacy helicopters also could help boost aircraft survivability. Should a compound helicopter's rotary-wing flight controls be damaged, aircraft controls could be used as redundant systems to "get an aircraft home," Piasecki said.
Drawbacks to the compound helicopter, however, are weight and hover power requirements. The addition of the ring tail and wing to a legacy H-60 will increase the aircraft empty weight and the hover power required relative to the baseline aircraft. PiAC argues that this could be addressed by replacing the aircraft's auxiliary power unit with a supplementary power unit and channeling some of the power generated by the SPU into an upgraded main drive train on an "as-needed" basis in high-demand situations.
The company tested a second-generation, 5.5-ft.-dia. ring tail in Boeing's suburban Philadelphia wind tunnel in 1992 at speeds up to 195 kt. "These tests helped us develop our control laws," Piasecki said. In addition, the company also constructed and tested an 8-ft.-dia., second-generation ring tail in late 2000. Tests of that tail were focused on control and performance and were used by the Navy to determine whether the service wanted to go forward with a flight demonstration.
PiAC has already completed construction of the 8-ft.-dia. flight demonstration ring tail and has integrated the unit's five-blade, variable-pitch propeller. Loads tests of the finished assembly are scheduled to begin here later this year.
Development of a static test vehicle (without the ring tail) also is underway at PiAC, and Kaman Corp. has signed on to test the aircraft at its Connecticut facilities. These evaluations are expected to get underway within the next year.
Contractor pilots are expected to fly the test program, which now is limited to the current operating envelope of the SH-60F. Reaching the higher speeds a compound helicopter can achieve will require more power, and this is now an "unpriced option" in the current contract, Piasecki said.
Updates to the YSH-60F flight demonstrator will include adding the lifting wing, which will come from an Aerostar business jet, adding the ring tail and modifying the drive train to accommodate the VTDP. PiAC plans integrated tests of the modified drive train at the Navy's helicopter transmission test facility.
Cockpit controls needed to operate the compound helicopter's systems will be integrated into the aircraft's existing mechanical controls to reduce pilot workload. The only noticeable difference in the cockpit will be the addition of a manual prop pitch override on the collective for the ring tail, Piasecki said.
Weight added to the flight demonstration aircraft will be about 1,600 lb., "but that's because we're using as many off-the-shelf components as possible for the flight test," Piasecki said. Production systems, optimized for their specific application, would weigh "several hundred" pounds less, he explained.
http://www.aviationnow.com/avnow/news/c ... 072964.xml
The compound helicopter is based on a modified Sikorsky H-60 Hawk family airframe. Sponsored by the Office of Naval Research, the primary objective of this flight demonstration is to show the potential improvements in speed, range, survivability and reduced life cycle costs attainable with Piasecki's VTDP technology.
Computer Aided Design Simulation
www.continuum-dynamics.com/research/top ... _research/
Ducted Fan position for forward flight
Ducted Fan for hovering flight
The VTDP compound helicopter achieves these goals by adding fixed wings and a tail-mounted ducted propeller. Piasecki Aircraft, founded by Frank Piasecki in 1956, has long proposed this technology as a way to enhance performance and reduce costs of rotorcraft. Today, the company has 50 employees, 20 of them engineers. Starting with Frank's groundbreaking R&D in the early 1960s, the company pioneered the development of compound helicopters. Frank celebrated his 81st birthday in October and still shows up at work, six days a week.
John Piasecki, Frank's son and company vice president, says that the VTDP compound helicopter is capable of faster cruise speeds, longer range, superior maneuverability and reduced costs. The VTDP design augments the aircraft's lift, combating retreating blade stall by unloading the main rotor system as the burden of lift is transferred to the wing. In addition to the stability conferred by the fixed wing, the aircraft reaches greater speeds because of auxiliary propulsion provided by the tail-mounted VTDP, commonly referred to as the "ringtail." The combination of the VTDP and a lifting wing provides for increased speed over 200 knots in production configurations, as well as greater maneuverability and reduced vibration and fatigue loads.
The compound helicopter confers several advantages to the armed forces. One of the most important, in the post-Cold War era of limited military budgets, is lower operating costs. By lowering fatigue loads and vibration levels, the technology can reduce costs and extend the life of parts. The technology also enables a rotary wing aircraft to fly at up to 220 knots; an attack helicopter fitted with the VTDP system would make for a formidable warship.
John Piasecki says the idea of compound helicopters is coming back into vogue with military planners because of the convergence of limited resources and expanded performance requirements. "This contract traces its origins to early Cold War competitions, but the compound technology is still very relevant, as armed helos proliferate in Third World countries," he says. "Armed helos are versatile and cost-effective aerial weapons platforms. Navy and Marines Corps aerial assault forces are projected over the sea at greater and greater distances. Emerging military requirements are driving the compound helicopter concept, not the old Fulda Gap scenarios."
The U.S. Marines are committed to the V-22 tiltrotor as an aerial assault platform, but they still rely on conventional helicopters, such as the Cobra and Huey. That's where compound technology can make a difference. "Compound helicopter technology could extend the performance and life of these legacy aircraft, to reduce their performance shortfall as compared to the V-22," he says.
Piasecki Aircraft's VTDP was competitively selected by the Navy under the FY00 Advanced Technology Demonstration program, which funds development and testing of high risk/high payoff technologies to address the Navy's future warfighting needs. The contract was awarded after Piasecki successfully completed ground testing of a full-scale flight-worthy VTDP unit under a $16.1 million concept exploration and development contract. John Piasecki says the VTDP Ground Test results were better than predicted, meeting all of the technical criteria necessary to proceed into the flight demonstration phase of the program. The flight test program will be conducted by a Joint Piasecki and Naval Rotary Wing Test Squadron Team, starting in 2003.
The VTDP compound helicopter concept is being investigated as an affordable means of addressing the Defense Department's need to upgrade the capabilities and extend the service life of existing single-rotor helicopters. Based on the services' current aviation modernization plans, the Defense Department is projected to spend over $41 billion to extend the capability and service life of the H-60, H-1, and AH-64 fleets until Joint Replacement Aircraft are fielded sometime after 2025. The Air Force selected the H-60/VTDP compound helicopter concept as one of several alternatives under consideration as an upgrade or replacement for its aging HH-60G combat rescue helicopter fleet. The replacement is slated to be fielded as early as FY07
http://www.geocities.com/tacticalstudie ... kivtdp.htm
Edited by - rickusn on Jul 04 2004 2:32 PM
Edited by - rickusn on Jul 04 2004 2:38 PM
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