Cordoba RTS-225 Cronus

RTS-225 Cronus
Profile diagram of the RTS-225AM2 Cronus.
Role	Strategic airlifter
National origin	Carthage
Manufacturer	Cordoba Aerospace
Designer	Cordoba Aerospace
First flight	1982
Introduction	1984
Status	In service
Primary user	Carthage Air Forces
Produced	1983-2000
Number built	1,344
Unit cost	NSD$264 million (flyaway cost, (FY2015))

The Cordoba RTS-225 Cronus is a large military transport aircraft developed and manufactured by Cordoba Aerospace for the Carthage Defense Forces. It is the largest aircraft by takeoff weight in the Defense Forces and provides critical intercontinental strategic airlift capability for the largest vehicles and equipment in the Defense Forces inventory.

The RTS-225 began development in 1979 and first flew in 1982, before entering service in 1984 with the Carthage Air Forces. Initially operating solely in military and government service, in 2006 limited sales of mothballed airframes were opened to private airlines and a total of 98 aircraft were sold. Since entering service, the RTS-225 has seen two major modernizations, the second of which occurred after production ended in 2000. A total of 1,344 RTS-225s were produced and 941 remain flying in modernized form, with an additional 392 airframes in storage. Recent Air Forces statements indicate the RTS-225 may continue to serve until at least 2040.

History

Replacement Heavy Airlift System

After the conclusion of the Northern War in 1976, the Carthage Air Forces commissioned a number of analyses and studies on the performance of airlift assets during the conflict. These investigations highlighted a number of shortcomings in airlift capability:

• While developed and heavily-populated Europe featured a relatively high density of airports, the vast majority of airports were too small to safely accommodate large strategic airlifters. Initial expectations were that most airports would be destroyed or damaged by retreating forces and would not be available for use, but a greater than expected number of smaller airports were captured mostly intact. This necessitated either transferring cargoes to other logistics systems (such as tactical airlifters) for delivery to the front or operating strategic airlifters in a potentially unsafe manner at smaller airports.
• The vast geographic commitments of the Carthage Defense Forces exceeded the ability of its logistics apparatus to readily supply. While these shortcomings affected nearly all modes of transportation, long-range airlift capacity in particular suffered from serious limitations.
• Attrition rates to the airlifter fleet had not been accurately assessed and the fleet experienced higher than expected loss rates both to enemy action, accidents, and aircraft fatigue. In particular, the wartime demands placed on the existing TSF-64 Leda resulting in increasing maintenance requirements and decreasing mission availability. Damage inflicted by European strikes on the spare parts logistics chain further exacerbated these issues.

In 1978, the Carthage Air Forces issued a request for proposals for the Replacement Heavy Airlift System (RHAS), a new strategic airlifter to supplement and replace the existing TSF-64. War damage to the production supply chain had limited the replenishment of the fleet and studies clearly indicated a need for an expanded airlift capability beyond what the TSF-64 provided even at peak fleet size. Five bids were received from Cordoba Aerospace, SHAFT ADS, Grierson-Mendelson Aviation, Harvest Air, and Southern Aircraft Corporation, and the Cordoba and SHAFT bids were downselected to a second round of more detailed study. The two proposals had similar fuselage arrangements (in common with the existing TSF-64) but featured very different propulsion arrangements, with the Cordoba proposal using a radical upper surface blowing design while the SHAFT bid relied on a conventional underwing podded arrangement with very large flaps for short takeoff performance.

While the design was considered riskier, the Cordoba bid was also evaluated as providing better performance and Cordoba was evaluated as being more likely to be capable of delivering the aircraft on schedule than SHAFT, and in May 1979 Cordoba Aerospace was selected as the winner. Separately from the formal bidding process, Cordoba conducted flight tests using a pair of modified TSF-68 Hellas medium airlifters as a proof of concept for the proposed design.

The first development prototype was completed in April 1982 and began flight tests in August. Four additional airframes were produced for flight testing and three airframes were produced for static load testing. Several refinements were made during this period to the wing geometry aft of the main engines to maximize lift generation and meet the required design load limits. By the fall of 1983 the design was considered sufficiently ready for service and was approved to enter production.

Into production

Full-rate production began in November 1983 and the first full wing of aircraft were delivered for acceptance in July 1984. Production eventually peaked at 90 aircraft per year delivered in 1991 from two plants located near Madrid and New Washington. A total of 675 of the initial RTS-225 design were produced although incremental improvements were made throughout the production process. The improved RTS-225AM1 entered production in 1991 at both facilities and a total of 669 aircraft were produced.

In 1996, cracks were discovered in the wings of several aircraft inboard of the main engines. After a period of inspections across the fleet, the cause was determined to be out-of-spec components delivered by a subcontractor and affected a total of 60 aircraft produced in the New Washington plant. These aircraft were taken out of service in 1998 for wing replacement and were returned to service by 2001.

The last full aircraft rolled off the assembly line on June 3, 2000. Parts of the supply chain remained in operation for two additional years to produce a stockpile of spares before all unique tooling and production equipment were placed in long-term storage. Some of this equipment was retrieved and reactivated as part of the RTS-225AM2 modernization program although no new airframes were produced.

Design

The nose gear is capable of kneeling to reduce floor height. The twin-post, four-wheel arrangement is intended to reduce ground pressure over more conventional single-post, two-wheel designs.

The folding ramp allows vehicles to be driven directly onto the cargo deck.

The RTS-225 is a large cargo aircraft with a high-mounted swept wing, T-tail, and four engines mounted above the wing. The fuselage arrangement is designed to maximize internal volume and ease of loading for cargo handling operations, while the wing and engine arrangement is designed to minimize takeoff and landing distances through the use of upper surface blowing.

Four TE-240-210U high-bypass turbofans provide thrust for the RTS-225 and are mounted on the upper surface of the wing near the fuselage, a departure from the more common podded engine arrangement. The unusual placement is designed to force air over the flaps and exploit the Coandă effect to direct engine thrust toward the ground when the flaps are extended. The concept was chosen due to the reduced complexity and maintenance requirements over more conventional blown flap designs and the RTS-225 is by far the largest aircraft in Carthage to use this powered lift arrangement. The engines are equipped with convergent nozzles to focus airflow over the flaps in conjunction with an additional convergent segment that is used during takeoff. The engines are also equipped with thrust reversers capable of maneuvering the aircraft on the ground and which can be deployed in flight to increase the maximum descent rate. The RTS-225AM2 uses newer, more powerful TE-264-270U turbofans in place of the original engines.

The fuselage is divided into two levels, with the upper deck housing the cockpit and rest areas for the crew with a large passenger compartment aft of the central wingbox. The passenger compartment is capable of holding up to 90 seated passengers but is not accessible from the cockpit except via the lower cargo deck. The cargo deck encloses a compartment measuring 37.4×6.4×4.5 m (123×21×15 ft), capable of carrying any vehicle in the Defense Forces inventory including armored vehicle-launched bridges and road-mobile ICBMs. Roller panels are used to accommodate palletized cargo and can be flipped to accommodate vehicle cargo. Loading doors are present at both the nose and aft of the aircraft allowing for simultaneous loading and unloading operations. The landing gear is capable of kneeling to reduce the cargo deck floor height to a level similar to that of common cargo trucks, easing loading and unloading operations.

While the RTS-225 is not designed to deploy paratroopers, it is capable of deploying cargo via parachute from the rear ramp. Palletized seating may be installed on the lower deck to increasing the seating capacity to nearly 440 passengers, but this capability is rarely used due to the widespread availability of commercial airliners for the personnel transport role. To further extend its range, the RTS-225 has a receptacle mounted above the cockpit for aerial refueling from boom-equipped tankers. Unlike smaller airlifters such as the RTS-224 Albatross, the RTS-225 is not plumbed for refueling pods and cannot serve as a tanker itself.

The landing gear is composed of two nosewheel bogies and four six-wheel main landing gear bogies for a total of 28 wheels. The main landing gear bogies can caster to reduce turning radius on the ground and to enable more efficient stowage, rotating 90° after takeoff before retraction. The high-flotation landing gear is designed to enable higher sink rate landings and operations at less developed airfields that may not be designed to support such large and heavy aircraft. The RTS-225AM2 modernization introduced improved oleo struts to handle the increased maximum weight and a new anti-skid braking system to reduce landing distances.

STOL capability

As originally conceived, the RTS-225 was expected to be capable of operating from smaller general aviation airports rather than being limited to major regional and international airports. As a result, the RTS-225 is designed to be capable of operating from runways as short as 1,000 meters (3,300 ft) with a 75% load and 500 nautical miles (930 km) of fuel and 800 meters (2,600 ft) with a 50% load. The landing gear was also designed to enable limited operations in improved fields, although no true rough field capability was specified. While the finalized design met these specifications, the RTS-225 has rarely used its full STOL capability as lingering safety concerns and increased airframe fatigue from rougher landings has discouraged the use of these capabilities in peacetime.

Nonetheless, upgrade programs over subsequent decades have maintained and improved these features. The RTS-225AM2 program significantly improved the aircraft's STOL capabilities to offset the planned weight increase, adding a new heads up display in the cockpit along with improved precision landing capability, a computerized anti-skid braking system, carbon brake pads, and improved thrust reversers. The cumulative effect of these improvements is a net reduction in landing and takeoff distance in spite of the increased maximum takeoff and landing weights.

Variants

RTS-225

RTS-225 cockpit.

The RTS-225 is the initial production design, with a total of 675 aircraft produced from 1983 to 1991. This variant entered service with the TE-240-210U turbofan engines and a cockpit crew of four (including two flight engineers). Incremental design changes including a new APU, improved communications, ergonomic modifications to the crew rest areas, an additional centerline fuel tank, and a redesigned loading ramp were installed throughout the course of production. No RTS-225s were upgraded into the RTS-225AM1 configuration, although 178 aircraft were upgraded to the RTS-225AM2 configuration along with all remaining RTS-225AM1s. An additional 392 RTS-225s remain in storage after some of the fleet was sold into civilian service or cannibalized for spares.

RTS-225AM1

The RTS-225AM1 variant was introduced in 1991 and incorporates all of the incremental changes made to the earlier baseline design along with updated avionics and a new glass cockpit designed for a standard two-man crew. The uprated TF-240-244U turbofans were also introduced in this variant, increasing thrust by 15% and reducing takeoff distance by 20%. 669 aircraft were produced in this configuration before RTS-225 production ended in 2000 after 17 years, and all RTS-225AM1s have been converted to the RTS-225AM2 standard.

RTS-225AM1S

Six RTS-225AM1 aircraft were produced in the special RTS-225AM1S configuration for use by the Carthage Space Research Agency. These aircraft are equipped with civilian market avionics and two of the six aircraft were modified to carry even larger payloads such as rocket components and satellites. The remaining aircraft are used to support other CSRA activities including testing new flight configurations and components. Two of these aircraft were used to test the upgrades later implemented in the RTS-225AM2 program.

A system of electric motors coupled with additional cameras around the aircraft was tested in order to improve ground handling performance in the RTS-225AM2, but was dropped due to weight and cost issues although several of the cameras were retained.

RTS-225AM2

The modernized cockpit of the RTS-225AM2, featuring modernized electronics. The additional eyebrow windows were tested in the RTS-225AM1S but not implemented in the final RTS-225AM2 specification in favor of a digital camera system.

The RTS-225AM2 uses new TE-264-270U engines with greater thrust and better fuel efficiency.

The Cronus Advanced Capability Improvement (CACI) program began in 2003 as effort to modernize all remaining RTS-225s in service to a new standard, driven in large part by the increasing weight of the Army's armored fighting vehicle fleet and an increased demand for overseas deployment. CACI is the most ambitious RTS-225 upgrade program thus far, including new engines, a new cockpit with further improved avionics, modernized communications, better compatibility with the Common Modular Intermodal Container system, structural upgrades to handle heavier loads, uprated landing gear, additional fuel tanks in the tail and sponsons, and a new pressurization system.

The new TE-264-270U engines produce 11% more thrust with 8% lower fuel consumption, further reducing takeoff distance by 12% and increasing range by 30% in conjunction with the new fuel tanks. Landing gear improvements allowed maximum takeoff weight to rise to 465,000 kilograms (1,025,000 lb) and maximum landing weight to 371,000 kilograms (818,000 lb) on an improved surface, improving takeoff and landing performance 10% over the original RTs-225 at the same payload fraction.

All 665 remaining RTS-225AM1s and 124 RTS-225s were converted to the RTS-225AM2 standard beginning in 2005. In 2013, an additional 54 RTS-225s were refurbished to the RTS-225AM2 standard to meet the growing demand for airlift capability as the rest of the legacy fleet was mothballed. A total of 843 aircraft are currently operating and in service.

CR-175

The CR-175 was the proposed civilian variant of the RTS-225. The type was expected to be marketed at industrial customers moving large outsize freight including factory tooling, mining equipment, and other machinery. The proposed aircraft would have used civilian avionics in place of military equipment and eliminated the air refueling capability to save weight and complexity. In 1987 the project was cancelled due to lack of sales. Instead, in 2006 the government opened the mothballed fleet of RTS-225s up for limited sale to civilian operators, resulting in the eventual sale of over 90 aircraft to the civil aircraft fleet. These aircraft received refurbishment to remove sensitive military equipment and install modern avionics and traffic control systems.

Operators

A detail of the RTS-225 nose in the raised position.

Military

Carthage

• Carthage Air Forces - 843 active aircraft, 392 in reserve storage

Civil

Carthage

• National Air Cargo - 28 aircraft
• New Republic Airlines - 8 aircraft
• Paradisio Air Cargo - 22 aircraft
• Phoenician Cargo Airlines - 6 aircraft
• Saharan Cargo Airlines - 12 aircraft
• Trans-Atlantic Airlines - 16 aircraft
• Versemia Freight Airlines - 6 aircraft

Specifications (RTS-225AM2)

The RTS-225 is designed to carry outsized cargo including deep-submergence rescue vehicles.

General Characteristics

• Crew: 5 (Pilot/Commander, copilot, 3 loadmasters)
• Capacity:
  • 90 passengers in rear upper deck compartment
  • 360 passengers with lower deck palletized seating
  • 37.4×6.4×4.5 m (123×21×15 ft) cargo compartment
  • 36 Type 105 standard pallets
• Payload: 160,000 kg (350,000 lb)
• Length: 76.2 m (250 ft)
• Wingspan: 74.5 m (244 ft)
• Height: 19.9 m (65 ft)
• Wing area: 654 m² (7,040 sq ft)
• Empty Weight: 176,000 kg (388,000 lb)
• Loaded Weight: 448,000 kg (988,000 lb)
• Max Takeoff Weight: 465,000 kg (1,025,000 lb)
• Powerplant: 4 x Elissa-Arishat TE-264-270U high-bypass turbofans, 270 kN (61,000 lb_f) each
• Fuel Capacity: 240,000 liters (63,000 U.S. gal)

Performance

• Maximum Speed: Mach 0.84 (481 kn, 553 mph, 890 km/h)
• Cruise Speed: Mach 0.82 (469 kn, 539 mph, 868 km/h)
• Range: 3,800 nmi (7,000 km) with a 160,000 kg (350,000 lb) payload
• Service Ceiling: 12,000 m (39,000 ft)
• Takeoff Roll at maximum takeoff weight: 1,200 m (3,900 ft)
• Landing Roll at maximum landing weight: 900 m (3,000 ft)

See also

Aircraft of comparable role, type, and era

• Antonov An-124 Ruslan
• Boeing 747
• Lockheed C-5 Galaxy