ARINC_AGREE Method_Reliability. Apportionment

The ARNIC and AGREE methods are systematic reliability allocation techniques used during the design phase of complex systems. The ARNIC method (Aeronautical Radio Incorporated) is widely applied in the aerospace industry. It allocates system reliability based on factors like complexity, number of parts, and environmental conditions, ensuring each subsystem meets reliability targets under harsh conditions. The AGREE method (Advisory Group on Reliability of Electronic Equipment) is an early and widely used method that distributes overall system reliability among subsystems based on their functional importance, operating time, and stress levels. Both methods guide engineers in setting realistic reliability goals and improving system design.

1. ARNIC and AGREE Method_ Reliability Dr Priya Gajjal

2. ARINC Method of Reliability Apportionment Used in system design & reliability engineering Based on complexity and operational time

3. Purpose of ARINC Method - Ensure overall system meets target reliability - Identify critical subsystems - Assign reliability goals proportionally - Guide designers where to improve reliability

4. Complexity Factor (Ci) - Represents relative design complexity - Assigned based on: • Number of parts • Design novelty • Environmental stress • Required precision/tolerance - More complex → higher Ci value

5. Advantages - Simple and structured - Incorporates time & complexity - Useful in early design stages - Identifies critical components easily

6. Example (Illustration) Subsystem | Ci | Ti ( hrs ) | Ci×Ti | Ai A | 2 | 50 | 100 | 0.20 B | 3 | 100 | 300 | 0.60 C | 1 | 50 | 50 | 0.10 D | 1 | 50 | 50 | 0.10 Then allocate : λi = Ai × λsystem and Ri = e^(- λi × Ti ) Subsystem Ci Ti (hrs) Ci×Ti Ai = ( Ci×Ti )/ ( Ci×Ti ) A 2 50 100 0.20 B 3 100 300 0.60 C 1 50 50 0.10 D 1 50 50 0.10

7. Subsystem Ni Ci Ii S1 50 2 5 S2 30 3 4 S3 20 2 2

8. Then : 𝑤1 = 50×2×5 = 500 ,  𝑤 2 = 30×3×4 = 360 ,  𝑤 3 =20×2×2 = 80 ​𝜆𝑠𝑦𝑠 = − ln⁡(0.90)/ 100 = 0.00105    failures/hr 𝜆1 = ( 500/940 ) × 0.00105 = 0.00056 ​ 𝑅 1= 𝑒 ^ ( −0.00056×100 ) = 0.945 (similarly for 𝑅 2​ and 𝑅 3​ ).