Mission Profile for Avionics

Question

Dear All;
  I have a question about "Mission Profile" for Avionics. As you know especially in avionics projects are using EPRD/NPRD catalogs. 
  Step 1: I have a any BOM and I imported in System/Function Model. After that I entered values of Failure Rate and calculate total Failure Rate of System.  (I selected component failure rates from Medini 217F.)
  Example BOM:
  1.-X System
  1.1. A Component
  1.2. B Component
  -----------------------------
  Step2: I created RBD and I calculated values of Relability/MTBF/MTTF  by Medini.
  Step 3: I created a Mission Profile and entered values of Tau(Duty Cycle) ..etc. I assigned to X System a mission profile. I am waiting change values of Relability/MTBF/MTTF but did not change. 
  To change of MTBF...etc  I guess needs to change Failure Rate. 
  In summary;
  I want to calculate the mission profile in the aviation system where the mechanical and hydraulic parts are located. Dou you have any example or have any directions?

medini_1023909254 · Answer

Hello Ilhan,     the MIL HDBK 217F is a very old standard, and has only a simplified scheme to adjust failure rates to different application environments .... basically an factor pi_E is selected which is part of the formula, the standard mission profiles in medini do not apply (no dependency to the tau values etc in a more advanced mission profile as it is used for 62380 or SN29500).  In medini you would select an appropriate Use Environment category.     This category is a value between 1 and 14 and and corresponds to the 14 different categories as given in 217F Table 3-2.  BTW, as you mentioned also EPRD/NPRD - these data bases do provide you with data only (no formulas), thus also for them no mission profile can be applied. However, when searching for entries in the data base you can apply appropriate filter settings for the quality level/domain and application environments.  The categories are defined in the PRD/NPRD Documentation:     Best regards,  Eckhardt