Engine Shop Visit Reserve per Flight Hour Calculator
A maintenance reserve is the shop visit bill spread across the hours or cycles you expect to fly before the next one. This calculator takes the workscope cost buckets from an engine quote and gives you the reserve per engine flight hour, per cycle and per month.
Your numbers
Teardown, module work, assembly and test labor from the workscope quote.
Non life-limited piece parts, repairs, vendor repairs and consumables.
Only the LLPs actually scheduled for replacement at this visit.
Freight, test cell fees, QEC build-up, teardown evaluation, logistics.
Allowance for workscope growth found at teardown.
Expected on-wing hours for this removal driver.
Average sector length for the fleet in question.
Average monthly flight hours per engine.
Your results
Planning estimate only. Contract reserve rates are set by the lessor or engine maintenance program and normally include escalation and condition adjustments not modelled here.
Reserve per EFH vs hours between visits
Sweeps Engine flight hours between visits from 2000 to 20000, holding your other inputs fixed.
Reserve forecast from your own ERP history
Optional: we can review how your shop visit and removal data could feed this calculation automatically.
Optional. The tool and every export work without this. No spam.
How to use the calculator
Enter the four cost buckets from the shop visit estimate, then set the contingency for workscope growth that normally appears at teardown. Next set the expected on-wing hours between visits, the average hours per cycle and monthly utilization. The primary outputs are the reserve per engine flight hour and the monthly amount to set aside per engine. The chart shows how sensitive the reserve is to the interval, which is the biggest lever you have on the number.
The formula behind it
Reserve per EFH equals the total visit cost (including contingency) divided by the hours between visits. Per cycle it is the same cost divided by hours divided by hours per cycle. Because LLPs are replaced on cycle limits while the rest of the visit follows condition and hours, the true cost is often split into an hour driven part and a cycle driven part in lessor contracts.
- Total visit = (labor + parts + LLP + other) x (1 + contingency)
- Reserve per EFH = total visit / hours between visits
- Reserve per cycle = total visit / (hours between / hours per cycle)
- Monthly reserve = reserve per EFH x monthly utilization
Reading the result
With the defaults, a visit of about 3.3 million dollars before contingency over 6,000 hours gives roughly 600 dollars per EFH. Stretch the interval to 9,000 hours and the same visit drops to about 400. If the LLP share is above half, check whether the limiting part is cycle driven: a short sector fleet burns cycles faster than hours and will reach the LLP limit well before the hours interval.
Common mistakes
Mixing an LLP replacement cost that belongs to a later visit with this visit, using calendar optimism for on-wing hours, and leaving out escalation of parts prices are the usual errors. Also remember that the reserve is a funding tool and not a prediction of final invoice. Compare it with actual shop visit invoices in your ERP and recalibrate each year.
Frequently Asked Questions
Is reserve per flight hour the same as cost per flight hour?
No. Reserve is the money set aside per hour to fund a future event. Cost per flight hour is what you actually spent over a period, which also includes line maintenance and unscheduled work. Use reserve for funding and actual cost for performance review.
Should LLPs be included in the same reserve?
Many lessor contracts split them into a separate LLP reserve per cycle. This tool lets you see the LLP share so you can either keep it in or split it out and divide it by cycles instead.
What contingency is reasonable?
It depends on the engine type and age. Mature engines with unknown condition often see workscope growth, while fresh restored engines see little. Use your own history of estimate versus final invoice rather than a generic number.
Can I use it for APUs or propellers?
Yes, the arithmetic is the same. Replace engine flight hours with APU hours or propeller hours and enter the relevant shop visit cost buckets and interval.
If your shop visit invoices and removal history sit in an ERP, Netray can build a read-only agent that calculates actual cost per EFH by engine serial number without exporting spreadsheets.
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