B1/B2 certifying staff coverage: the split your man-hour plan probably misses

Ask a maintenance manager how many engineers are available next month and you will get a number: fourteen, maybe sixteen. It sounds useful, but it is the wrong unit. A Part-145 input is not gated by total engineers. It is gated by authorised certifying hours in the correct category, on the days the task cards actually reach their certification points.

01Headcount is not coverage

B1 and B2 staff are not interchangeable capacity. A strong B1 roster cannot absorb an avionics-heavy check, and a B2 cannot release the airframe because the hangar is busy. Type authorisation narrows the pool again: an engineer may be B1-licensed, current and experienced, yet still unable to certify the AW139 in front of him.

This is why an annual man-hour plan can look healthy while a specific input fails. The plan says the organisation has enough hours across the year. The hangar needs enough B1 and B2 certifying hours between day one and day twelve, after leave, training, line duties and management tasks are removed.

02Split the package before counting people

Use the last three similar check packages to build the split. Do not start with a blank assumption:

• Export or sample the task cards and tag each one B1, B2 or support.
• Measure certification and supervision time separately. Twelve per cent of B1 task hours and eighteen per cent of B2 task hours are reasonable starting factors if your records are thin — replace them with your own measured values.
• Subtract committed work from each certifier before calculating availability: line callouts, audits, training, leave and management duties all count.

03A worked AW139 example

Take a 1,500 man-hour AW139 check planned over twelve working days. Historical cards give 900 B1 hours, 300 B2 hours and 300 support hours. Your measured certification factors are 12% for B1 and 18% for B2.

Each certifier is assumed to produce six usable hours per day for twelve days: seventy-two hours each. Two B1s therefore provide 144 hours against 108 hours of demand. The single B2 also appears to provide exactly the required 54 hours — until you remember that he already has line commitments.

If that B2 loses only ninety minutes per day to line certification, he loses eighteen hours across the input. His usable capacity falls to 36 hours against 54 hours of check demand: an 18-hour coverage gap, despite the headcount sheet showing one B2 “assigned”. One sick day makes it worse. The B1s cannot legally absorb the shortfall.

04Test the roster, not the average

The next step is to place the demand on a calendar. Avionics certification often peaks after access, during troubleshooting and again at functional test. If those events sit on days eight to ten, a B2 who is available on days one to five does not solve the bottleneck. Plot required B1/B2 certifying hours by day and compare them with named, authorised people.

For resilience, I want the calculated demand to fit below 80% of usable category capacity. At 100%, the plan has no room for findings, rectification, a late part or one absent certifier. In the example above, B1 passes at 75% loading; B2 fails at 100% before any disruption.

05Make the fix before accepting the slot

When B2 is critical, you have four honest options: move the input, reduce concurrent line commitments, bring in an appropriately authorised contract B2, or add redundancy through training and authorisation. What does not work is approving the slot because “three certifying staff are on shift” when two of them hold the wrong category.

Build this split into your quarterly review rather than treating it as a one-off rescue. The AMC1 145.A.30(d) man-hour planning guide shows the wider workload method; the category split is what turns that workload into a roster you can actually certify with.