Much has been written locally about the AHRLAC (Advanced High Performance Reconnaissance Light Aircraft), a light reconnaissance and counter-insurgency aircraft developed in South Africa by AHRLAC Holdings. It is a joint venture between the Paramount Group, Africa’s largest privately owned defence and aerospace company and Aerosud Innovation Centre, a South African aeronautical engineering and manufacturing company. The aircraft is designed to perform as an inexpensive, more versatile substitute for unmanned aerial vehicles (UAVs) and modern fighter aircraft.
In July 2014, the AHRLAC conducted its maiden flight and in August 2014 the aircraft performed its first public flight display at Wonderboom Airport, just outside Pretoria.
The AHRLAC (Advanced High Performance Reconnaissance Light Aircraft), a light reconnaissance and counter-insurgency aircraft developed in South Africa by AHRLAC Holdings
The MWARI – the weaponised version of Paramount Group’s AHRLAC aircraft is an intelligence gathering and precision strike aircraft, which carries the same surveillance, targeting, defensive and attack capabilities normally associated with a larger class and vastly more expensive aircraft.
To meet the increasing global demand for real time airborne intelligence capability, Paramount Group and its partners have completed a new state-of-the-art AHRLAC factory construction at the Wonderboom Airport Complex, north of Pretoria in South Africa. This
10 356m² factory will produce the AHRLAC unarmed base aircraft, with MWARI military aircraft and customised mission systems being integrated in a separate facility.
The new factory marks a pivotal point for African aerospace industry as it will be the largest privately owned aircraft factory in Africa able to produce advanced, state-of-the-art aircraft of this sophistication.
The AHRLAC engineers needed a 5-axis milling machine that could machine special alloy aluminium blocks to manufacture the eight different spars that make up the 12 metre stiff wing used on the AHRLAC. The machine chosen was a DMG MORI DMF 360/11, which accommodated the dimensional aspects of the various aluminium blocks that need to be machined
The AHRLAC engineers were looking for a quick connection and disconnection fixture system that must also be robust against forces and movements of bending, vibrational behaviour, frequency, collision and forces during the milling process. The aluminium blocks can weigh up to 280 kilograms
The first thing that stands out about the aircraft is the design; a high wing, ‘pusher’ propeller concept that provides clear all-round visibility for the two crew and aircraft sensors due to the absence of a front mounted engine and propeller. It also provides the short take-off and landing capability (STOL) to operate from almost any airstrip. The AHRLAC is a design integration of fixed wing surveillance and reconnaissance platforms and attack helicopters.
The secrecy behind the manufacture of this aircraft is understandable. However, through the necessity to explore avenues that are not only cost saving for the manufacturing process but will also realise a more efficient machining process, the engineers working on the AHRLAC project have teamed up with engineers from German machine tool builder DMG MORI and have come up with a concept that is a world first. Subsequently DMG MORI recognised the uniqueness and effectiveness of this project and it is said that the company will in future offer the solution that the engineers have decided on as a standard on the larger machines that DMG MORI manufactures.
Testing has subsequently shown that the machine can mill and drill a 280 kilogram aluminium block into a wing spar in a time frame between 14 and 17 hours. Done conventionally this same operation could take up to 80 hours
A wing spar that has been fully machined
The AHRLAC engineers needed a 5-axis milling machine that could machine special alloy aluminium blocks to manufacture the eight different spars that make up the 12 metre stiff wing used on the AHRLAC. Included in the required specifications during the machining process was that residual stresses had to be minimised and that when machining the blocks they did not require special jigs to keep the workpiece rigid.
The manufacturing fixture as a clamping system
Ideally what the AHRLAC engineers were looking for was a quick connection and disconnection fixture system that must also be robust against forces and movements of bending, vibrational behaviour, frequency, collision and forces during the milling process. Additionally, the mechanical properties and the structural integrity of the material had to be taken into account. The machining operations included 5-axis milling and drilling, all to be done in the least amount of setups to minimise time and quality issues.
The machine chosen was a DMG MORI DMF 360/11, which accommodated the dimensional aspects of the various aluminium blocks that need to be machined.
Talks between the AHRLAC engineers and DMG MORI engineers began back in 2014 with concepts decided on in 2015. The concept was a first for both sets of engineers and had not been tested before.
For milling of the wing spar it was decided that a clamping bridge should be built on the DMG MORI DMF 360/11 milling machine where the aluminium block could be positioned and clamped. In order to realise all the milling and drilling operations the engineers suggested and subsequently decided that the traverse be clamped between two dividing units that would allow complete 360° horizontal rotation. The dividing units are direct drive units attached to the table and include adapter plates.
It was also decided that on top of the traverse an additional steel plate be used as a fixation plate to locate the exact position of the holes for clamping and for the zero-point clamping units. For additional accuracy beam technology is included.
The company has also invested in a DMG MORI CTX beta 2000 TC lathe
Included in AHRLAC’s investment programme was the purchase of a Quintus fluid cell press, only the second one to be installed in South Africa. The press is used for sheet hydroforming and similar sheet metal forming applications. This particular press will be processing sheet up to 700 by 1 800mm with a pressure of 800 bar and a press force of 17 000 ton
However, one of the key features of the system is the incorporation of an angular head that is fetched from the tool magazine and allows the 18 000rpm FD spindle to drill holes – coolant driven – in the difficult to get to areas that are normally associated with aerospace component manufacture. This allows for full simultaneous 5-axis machining, in both B/C and A/C-configurations.
Project and system acceptance was signed off in the first half of 2016 and DMG MORI began building the machine shortly thereafter for delivery in 2017.
Testing has subsequently shown that the machine can mill and drill a 280 kilogram aluminium block into a wing spar in a time frame between 14 and 17 hours. Done conventionally this same operation could take up to 80 hours.
The project has also highlighted that the client (Aerosud Innovation Centre/AHRLAC), the South African representative (Retecon Machine Tools), the machine builder (DMG MORI) and the CNC control manufacturer (Heidenhain) can work together and come up with a solution.