Question

Based on following given information and data, assumed a product’s MTBF=1500 hrs, and which experienced three down activities, please calculate following figures, and state which group people ( Such as passenger, aircraft designer and manufacturer, Airliner etc) who are concerning about them in management.

Time required (hrs)	Down No. 1	Down No. 2	Down No. 3
Corrective repair	28	130	26
Prevent Maintenance	63	118	15
Administration Delay Time	19	28	19
Logistic Delay Time	240	410	340

• Mean Down Time=_______________________________________________
• Inherent Availability=_________________________________________
• Achieved Availability=________________________________________

Answer 1

The Downtime table has been calculated below using the data provided

Time	Down 1	Down 2	Down 3	Total
Corrective Repair	28	130	26	184
Preventive Maintenance	63	118	15	196
Admin Delay Time	19	28	19	66
Logistics Delay Time	240	410	340	990
Total Inherent Downtime	91	248	41	380
Total Actual Downtime	350	686	400	1436

The total inherent downtime is the total of Corrective Repair and Preventive Maintenance. The total actual downtime for each occasion is the total of inherent downtimes and the delays.

Hence Mean downtime = (350 + 686 + 400)/3 = 478 hours

Mean Inherent Downtime = (91 + 248 + 41)/3 = 127 hours. Inherent Availability = 1-127/1500 where 1500 is the mean time between failures or MTBF given. = 91.6%

Achieved Availability = 1 - (Mean Actual Downtime/MTBF) = 1 - 478/1500 = 68%

We see that while the inherent availability is 92% it goes down to 68% in actual terms due to the administration and logistical delays. The operations team would need to prepare better to manage downtimes and turning around after that.