H145 man-hour planning: the light-twin cycles trap

When a planner tells me "the H145 is a light twin, so it must be cheaper to crew than the AW139," I ask one question: how many cycles per flight hour? On HEMS and utility work the answer is usually three, four, sometimes five. That single number is why a fleet that looks cheap on a flat man-hours-per-flight-hour rate quietly runs out of engineers by March. The fix is not a bigger fudge factor — it is splitting demand into the three drivers that actually consume man-hours.

01Why the flat rate lies

A single MH/FH figure assumes maintenance demand scales with airborne time. On a medium twin flying long offshore legs, that assumption is roughly tolerable. On an H145 doing 12-minute HEMS sectors, three different clocks are running at once:

• Flight-hour tasks — scheduled inspections and component lives counted in airborne hours.
• Cycle-driven tasks — engine starts, landings, rotor brake applications and fatigue-counted events that accumulate per sector, not per hour.
• Calendar tasks — weekly, monthly and annual items that arrive whether the aircraft flies or sits.

Short sectors inflate the second driver while the first stays small. That is the trap: the fleet flies modest hours, so the flat-rate plan looks lean — while cycle and calendar workload walks in through the side door.

02The worked example

Six H145s on HEMS contracts. Each flies 50 FH and logs 220 cycles per month. Use your own MPD and task-card history for the factors; for this illustration, line and light-scheduled demand splits like this:

Now compare the flat-rate plan. A "reasonable" 1.0 MH/FH across the fleet gives 6 × 50 × 1.0 = 300 MH/month. The split-driver reality is 431 MH/month — a 131 MH shortfall, 44% more workload than the flat plan budgets. At roughly 110 productive hours per engineer per month after leave, training and sickness, that gap is 1.2 engineers before a single unscheduled finding. Add a modest 15% rectification factor and the real demand is ~496 MH against a 300 MH plan: 1.8 engineers missing, every month, from a fleet that was supposedly the cheap one.

03Where the factors come from

You do not need OEM figures to start — you need your own history. Pull the last 12 months of task cards and split logged man-hours into the same three buckets. Most helicopter MROs discover the cycle bucket is bigger than anyone admitted, because the work arrives disguised as daily inspections, 25h items and component changes that "just came up." Two disciplines make the numbers defensible:

• Log cycles as carefully as hours. If the tech log feeds your CAMO forecast, the cycle forecast deserves the same review meeting as the FH forecast — the same interface discipline described in the man-hour calculation guide.
• Split by B1/B2 as well as by driver. Avionics calendar items on a glass-cockpit light twin land almost entirely on B2 certifying staff; a healthy total headcount can still hide an empty B2 column.

04What changes in the plan

Once the H145 fleet is modelled on three drivers, two conversations change. First, the quarterly review stops asking "did we fly more hours?" and starts asking "did cycles drift from forecast?" — a 10% cycle drift on this fleet is 16 MH/month, invisible in any flight-hour report. Second, new contract bids get priced on sector length. A HEMS contract at 0.2-hour sectors and a utility contract at 0.8-hour legs are different staffing products even at identical annual hours. The man-hour plan that prices them the same is the one that breaches its deviation threshold by summer.

Run the split for your own fleet: hours, cycles, calendar, then findings. If the flat-rate answer and the split-driver answer differ by more than about 10%, the split is the one to defend in front of the auditor — because it is the one the hangar will actually consume.