Frequently asked questions

STANAG 4569 (officially NATO AEP-55: Procedures for Evaluating the Protection Levels of Logistic and Light Armored Vehicles) is the NATO standard that defines the protection levels, and the test methods, for the threats that personnel in logistic and light armoured military vehicles may face on the battlefield.

In vehicle design, the standard sets out, from an engineering point of view, which threat level armour configurations, underbody structures and glazing and material components must withstand.

Main threat categories

• Kinetic energy threats: infantry rifles, machine guns, heavy machine guns and armour-piercing automatic cannon ammunition.
• Artillery fragment threats: fragments from high-explosive artillery shells detonating at defined distances.
• Mine and improvised explosive device (IED) threats: pressure-activated mine and blast effects from beneath the vehicle or at wheel or track level.

Protection levels

The standard defines six protection levels, from basic protection up to the heaviest armoured combat vehicles. As the level rises, the severity of the kinetic, fragment and blast threats countered increases. The detailed test conditions and distances for each level are defined in the standard itself.

The values are a summary; refer to the current edition of the standard for the binding definitions.

Armoured vehicle design generally consists of six main stages, from defining the requirements to series production and lifecycle support:

1. Needs analysis and definition of system requirements (Requirements Engineering)

   Before the design begins, the operational concept of the vehicle (CONOPS) is clarified.

   • Mission profile: personnel carrier, command and control, reconnaissance and surveillance, weapon carrier or ambulance roles.
   • Protection level: determining the required ballistic, fragment and mine/IED protection levels according to STANAG 4569.
   • Mobility and environmental conditions: power-to-weight ratio, maximum speed, steep gradient climbing, trench crossing, fording depth and climatic conditions (operating requirements from -32°C to +49°C).
   • Logistic constraints: transportability by C-130 or similar transport aircraft, compatibility with the railway loading gauge.
2. Concept development and preliminary design (Conceptual & Preliminary Design - PDR)

   At this stage the basic design decisions are made, the concept is created and the first digital prototypes are produced.

   • Hull architecture: choosing between a structural body mounted on a chassis and a monocoque (V-hull) hull. (The V-hull underbody structure is critical for deflecting the shock wave in underbody blasts.)
   • Powertrain matching: selecting the engine, transmission, transfer case, axles and suspension system (independent or leaf-spring) according to the gross vehicle weight (GVW) calculations.
   • Ergonomics and interior layout: positioning of the crew, commander and gunner, placement of special blast-mitigating seats, and design of footrest areas that prevent spinal injuries during a mine blast.
   • CAE and preliminary simulations: first finite element analysis (FEA) and computational fluid dynamics (CFD) on models built in a CAD environment (e.g. CATIA), covering centre-of-gravity determination, engine cooling flow analysis and rough strength checks.
3. Detailed design and engineering (Detailed Design & Critical Design Review - CDR)

   This is the phase in which engineering is balanced and the production data is prepared.

   • Armour structure methodology and material selection: detailed modelling of structural steels (Armox, Hardox, etc.), ceramic plates, composite layers and inner shell linings (spall liners).
   • System integration: layout of the electrical wiring, hydraulic lines, HVAC (climate control) systems, NBC (nuclear, biological, chemical) filtration systems and automatic fire suppression systems (FSS).
   • GD&T and manufacturing drawings: tolerance analysis of all parts, preparation of technical drawings and creation of the bill of materials (BOM) structure.
4. Prototype manufacturing and production preparation (Prototyping & Pilot Production)

   This is the stage in which the design becomes reality and the first verifications are carried out.

   • Sheet cutting and welding: laser/plasma cutting of armour steels and robotic or certified welded fabrication using special welding procedures (WPS/PQR) that will not reduce ballistic resistance.
   • Rapid prototyping and fixturing: 3D printing (e.g. with engineering polymers) and prototype tooling production for assembly lines, special brackets and interior fittings.
   • Vehicle assembly: joining the chassis, running gear, engine and armoured cabin.
5. Verification, qualification and testing (Verification & Testing)

   This is the most costly and most critical stage of armoured vehicle projects.

   • Functional and road tests: brake, steering, suspension, climbing, maximum speed and mileage-life tests on durability tracks.
   • Ballistic and mine tests (live-fire testing):
     • Testing armour plates and hull joints by firing standard ammunition at them on firing ranges.
     • Wheel-level and underbody mine/IED detonation tests with real or simulated explosives (TNT charges), reading chassis deformations and the data from acceleration sensors in the seats and from personnel simulators.
   • Environmental tests: hot/cold tests in climatic chambers and electromagnetic compatibility (EMC/EMI) tests.
6. Series production and lifecycle support (Series Production & ILS)
   • APQP / PPAP processes: assuring series production quality and supplier qualifications.
   • Integrated logistics support (ILS): maintenance manuals, interactive catalogues, spare parts management and delivery of user training.

We design for the following vehicle classes:

• Armoured personnel carrier
• Mine-resistant personnel carrier
• Weapon carrier vehicle
• Riot control vehicles
• Wheeled and tracked unmanned ground vehicles

The difference lies in the scope of the project and in the customer's core business.

Complete vehicle design

It covers the end-to-end design of a new vehicle that is not in your product family, based on the technical requirements defined for its intended use. It suits customers who want to add new products to their product family or make their system mobile.

Vehicle subsystem design

We contribute our experience and engineering workforce to the design of the subsystems of a vehicle in your existing product family or in a project you are working on. It suits customers whose core business is vehicle design and who need additional workforce support.

System integration into the vehicle

For customers whose core business is not land vehicle design, we integrate their systems into the vehicles they choose, or that we help them choose.

Do you also work on a single subsystem?

Yes, we can also work on the system or subsystem(s) you need, the scope of which you define.

Inputs we need for integration

• The system manufacturer's technical requirements and the integration document of the system components
• The vehicle manufacturer's 3D model and the vehicle electrical system diagrams

Deliverables we provide

• Technical drawings of the system components
• System electrical and hydraulic diagrams
• Vehicle 3D model (if the vehicle manufacturer's 3D model is not available, a vehicle model created through reverse engineering)
• 3D system model

Implementation

For the integration, the work on the system components and the revisions on the vehicle can be carried out at our production facility in Ankara.

YDD stands for “Your Design Department”.