CARDOEN-BELL 206 L-III / The Chilean attack helicopter

Chilean_Thunder · July 28, 2023, 3:32am

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CARDOEN-BELL 206 L-III

History:

First idea for an attack helicopter

In 1984 Carlos Cardoen, a Chilean engineer and businessman, commissioned an engineering report to the Aeronautical Engineer René M González within three months, in which the feasibility of modifying a civilian helicopter for military use would be studied. On that occasion it was the German device MBB BO-105. The Construction of the first Mock-Up begins between 1985-1986. A Mock-Up is the construction of a model of what the helicopter will be on a real and three-dimensional scale of what is on the drawing board, in addition to which they can be presented for commercial purposes at exhibitions and fairs to gain interest in the project.

FIDA 1986, March; El Bosque Air Base; Santiago, Chile.

During the “International Air Fair” (FIDA) the mock-up of the attack helicopter based on the BO-105 was presented, which was very well received by people since it was an excellent option for developing countries.

The modification left the helicopter with a remarkably different profile, converting it into a single-seater and adding an arms-carrying wing that in certain flight attitudes improved aerodynamic performance. The pilot’s protection increased significantly as vulnerability to attack from the ground also decreased. The rear part of the fuselage was also intervened. It also included a Lucas turret. However, and due, in large part, to the political situation in Chile at the time, representatives at FIDA '86 of the German company MBB that manufactured the BO-105 strongly opposed authorizing the modification after seeing it exhibited. So unfortunately this first intention did not prosper beyond the Mock-Up stage.

Publications after FIDA '86.

New Alternative: Cardoen-Bell 206 L-III.

After MBB’s refusal, the BO-105 was discarded as a platform and a new aircraft to be redesigned was chosen: the Well-known Bell Long Ranger 206 L-III. In October 1986 Cardoen Industries contacted the company Bell Helicopter Textron Inc. (BHTI) to carry out a joint project, initiative that was well received by the North American company. After efforts by the INCAR presidency, in February 1987 René González traveled to Dallas to participate in the HAI (Helicopter Association International) exhibition. At this fair, technical meetings were held with a commission of Bell engineers to consider the technical aspects of the modification. Initially maintaining the intention of building an attack helicopter (anti-tank), work began in 1987 in conjunction with Bell Helicopter Textron, holding meetings in the USA and Canada and arriving at the drafting of a preliminary design report in which they presented proposal monographs. As in the case of the BO-105, a structural modification was considered that made the helicopter single-seater. One of the first configurations considered by the INCAR team was an attack helicopter with a tandem cockpit, however such a configuration was discarded for reasons of stability and control, as the location of the center of gravity would be very different from that of the original model.

Discarded modification of the Bell 206 with tandem cockpit and weapons wing presented by INCAR

After the talks in February 1987, in April of the same year an INCAR-BHTI meeting was held at the Fort Worth plant. At that meeting, BHT delivered a report with a modification proposal in a single-seat configuration, which included a 3-view diagram, weapon possibilities, avionics equipment, design and development costs, work plan, etc. However, BHTI required INCAR to invest a large sum of money derived from the engineering and development work that would be provided mainly by BHTI, so it was finally decided that all this work would fall into the hands of cardoen industries (INCAR) keeping Bell as an associated company, INCAR was thus able to save a lot of money so INCAR had the entire project in its hands along with the construction of the prototype.

Official Bell Helicopter Textron Proposal Design, Considers Firepower

Structural Mock Up Construction

Unlike the mock up based on the Bolkow BO 105 (which was built in wood), the mock up of the Bell 206 was built in aluminum to be used later in different tests, for this Industrias Cardoen (INCAR) imported a fuselage Bell Long Ranger who had been in an accident; The main beam was repaired by technicians specialized in aircraft structures Guido Véliz and José Véliz, then the front third of the fuselage that would be intervened was removed.

Fuselage Bell Long Ranger who had been in an accident

Bell 206 with cabin structure removed

At first, the cabin was too small for the helicopter pilot, luckily the first test beams were made of wood, so this was corrected by raising the roof of the original cabin by means of a “vertical extension” of the main beam. This modification would respond successfully in the structural tests, reinforcing the entire structure and serving as a canopy tower.

New aluminum cab with raised roof

Lateral view of the structural mock up. The areas intervened by the modification are clearly appreciated.

Test of performance

In 1987 with the finished structural mockup, a wind tunnel was simultaneously built to carry out other tests in the future, meanwhile the mock up structure was subjected to different weight tests, using lead ingots in different positions to see if there was a deformation in the structure that were recorded by means of strain gages. The new cab supported loads 3.5 times higher than the original, 16,000lbs of frontal load without showing permanent deformation. which was a success since with this new structural resistance the helicopter could be used for civil and military missions.

Bell seemed very satisfied with the modifications made to the mock up, so she sent a letter demonstrating her support for the project and mentioning the construction of the helicopters in Spain since it was not possible to export fuselages to Chile due to the Kennedy amendment.

Letter from bell to cardoen industries expressing support and excitement for the project

However, Bell would surprisingly get out of the project arguing that they considered it unlikely that the US government would grant the necessary permits for the production of the aircraft. Therefore, Industrias Cardoen would continue the project on its own.

Wind Tunnel Tests

Since the front part of the original Bell helicopter had been modified, different aerodynamic tests had to be done to make sure that everything would work well in the future. The modeling team built several models at different scales of the original and the modified helicopter. . The tests, carried out on various occasions and in different temperature conditions, did not show significant differences between the two models in either flow or pressure readings at key points. so the modification was fit to fly in the future.

The wind tunnel was designed and built by cardoen industries

AH Version Mockup (Attack helicopter)

In November 1988, a demonstrative mock-up of the final version was built as an anti-tank helicopter from the Bell that had crashed and was imported to Chile, so this mock-up is made from the original material and is considered a real Bell 206, it just didn’t fly as the final prototype. Were considered: side arms to carry weapons, periscopic sight of the Norinco HJ-8 “Red Arrow” missile system, place for the gunner behind the cockpit, proper configuration of the instrument panel and side panels (of course different from the distribution of instruments in the utility version eventually used in the prototype), reflex sight for 2.75 in (70 mm) rockets.

Tests with Missile “Red Arrow HJ8” (NORINCO Industries, China)

Tests were also carried out in November of 1988 to see the feasibility of equipping the combat version (AH) with the “Red Arrow” anti-tank missile manufactured by NORINCO. The tests used missiles with only a third of the propellant charge and without a warhead. The original structure of the Bell Long Ranger, although it had hard points to fix medium weapons, was not designed to withstand explosive forces of this type. Therefore, after the tests, a deformation was noticed in the rear part of the fuselage, a part that had not yet been modified by Cardoen industries, so if you wanted to carry weapons of that caliber, several hours of engineering work had to be invested. However, modifying the original fuselage would alter the original center of gravity of the helicopter which was not allowed.

Publication in Jane’s JAWA in 1987 reporting on the progress of the project

Construction of the Prototype

Once all the previous tests were passed, they were ready for the construction of a prototype and all the advances that were made were kept strict and detailed records in plans according to the FAA (Federal Aviation Administration) standard, since it was always the intention of the project to obtain certification STC (Supplemental Type Certificate) of this American agency for the commercialization of the civil version of the helicopter. Unlike the previous mock ups, now the prototype had to be built to the millimeter, everything had to be perfect, for this the Mechanical Civil Engineer Jaime Ortúzar, responsible for quality control within the team, designed a JIG, which is a rigid metal frame where the structure that would be modified to obtain a final quality prototype remains fixed. For the construction of the prototype, Industrias Cardoen imported a Bell 206 Long Ranger US registration N38958.

Bell 206 with the new cardoen frontal modification

GHTI Telex recognizing the capabilities of the Cardoen Industries engineering team

Delivery of the prototype, 1989

First flight of the prototype December 8, 1989, Los Cerrillos Airport. Santiago, Chile.

Chilean newspaper talking about the first flight

Prototype in Fort Worth, Texas for testing and FAA certification flights

It is decided to send it to the US to start the certification process and obtain the Supplemental Type Certificate (STC) through the representation of Global Helicopter Technology Inc. In January 1990, via Lufthansa, the prototype arrived at the GHT facility in Hurst, Texas to undergo the FAA testing program.

An STC, in simple words, is the recognition and quality certification of any modification made to an existing aircraft. It is granted by the most prestigious aeronautical agency in the world: the Federal Aviation Administration, FAA. Throughout the development of the prototype, work was done in conjunction with two FAA technical delegates, who monitored the entire project and periodically approved the different stages of it in Santiago de Chile.

Structural Mock Up at FIDAE 1990

Simultaneously while the prototype was in the United States, the structural mock up of the attack version that had been used for the launch of the Chinese Norinco missile was presented at the aviation fair in Chile where different people could appreciate what the version would become. At the end of the attack that was so expected, General Matthei of the Chilean air force was present at that fair, together with other senior officials from the FACH and Carlos Cardoen himself, which generated great interest and support from all those present.

The end of all plans

When the certification process was quite advanced and the different FAA tests had been passed, requiring minimal modifications, surprisingly the extension of the STC was suspended and on March 27, 1991 the prototype was confiscated by the North American customs authorities arguing that it had the characteristics of an attack helicopter as it was outfitted with five “hardened” points suitable for attaching gun units, rocket pods and other weaponry and that INCAR intended to export it as such to Iraq. Under this slander, the prototype was seized and never returned to its rightful owner: INCAR. This would mean the total suspension of the project and the frustration of the possibility of building these helicopters in Chile.

As the prototype without weapons was requisitioned and the project stopped there, in Chile it was never possible to build the flying attack prototype that was wanted from the beginning, but at least the attack mock-up was built, which was made from a real Bell 206 that had an accident and was imported to chile, for which reason it had authentic materials; You could see the weapons that it could carry since it had 5 anchorages to carry weapons such as rockets, machine guns and cardoen bombs, and there are also photos where you can see the cockpit in which you can clearly see the instrument panel for the version of attack and we know that the caliber of the rockets was 2.75 inches (70 mm), in addition to having the official proposal of the Bell company in the form of a “layout” which also considers the weapons they intended to carry, you can see an autocannon on the underside of the helicopter and rocket carriers on the sides.It was basically intended to use the same weapons configuration as the initial BO 105, which had rocket carriers and a Lucas turret with a .50; It was also intended to load the helicopter with cluster bombs made by cardoen and traditional bombs, since the new cabin supported loads 3.5 times higher than the original, 16,000 pounds of load, without showing permanent deformation, as demonstrated in weight tests.

Newspaper clipping explaining the weaponry the helicopter would carry

Specifications:

Armament: Five hardened points where it can be installed:
- Machine gun: x1 Lucas Turret carrying 0.50 calibre (12.7 mm) machine-gun
- Rockets: x2 LAU32 of 7 tubes 70mm rockets
- Bombs: MK-81 (250 pounds), MK-82 (500 pounds), MK-83 (1000 pounds), MK-84 (2000 pounds), CB 500-K (1000 pounds), CB 250-K (500 pounds), CFB 27-300 High Fragmentation Bomb (300 kg), Penetration Bomb.