Bjorn’s Corner: Keeping airliners operational. Part 9.

Bjorn Fehrm

June 16, 2017, ©. Leeham Co: This week we finish our analysis how an operator would keep our tentative airline operational. By now we know the maintenance of the fleet is a critical part of running an airline.

If we miss a beat from our approved operator’s maintenance plan, our airworthiness authority can ground us.

We now finish the series with looking at how some cost-heavy parts are kept fit. We then summarize our costs for keeping our Airbus A320s flying.

Figure 1. The first modern maintenance program was formed around the Boeing 747. Source: Wikipedia.

Maintenance of “Heavy components”

In last week’s Corner, we learned the maintenance of so called “Heavy components” gets special treatment. These are not treated as part of the normal checks. As they have independent maintenance programs, they are treated and calculated separately.

Heavy components are: Thrust reversers, APU, Landing gear and Tires/Wheels/Brakes.

The many systems components that are collectively called Rotables are also treated separately.

The Heavy components wear with the flight cycle as they are used during taxing, take-off and landing. An APU is also used during ramp operations, but the main use is flight cycle dependent.

Landing gear

The landing gear is replaced with a reconditioned unit every 10 years. In our case, this means after 24,500 flight cycles.

As a reconditioning gear will set us back with around $600,000, we shall calculate $25 per flight cycle for this replacement.

Thrust reversers

The thrust reversers, placed in the nacelles, are items which are subject to high stresses. They need a shop visit for overhaul every 12,000 cycles. Ideally this removal can be coordinated with engine maintenance at the same time.

As such maintenance costs ~$480,000, we shall calculate with a cost of $40 per flight cycle for reverser maintenance.


The APU is a small gas turbine. It produces compressed bleed air and electrical + hydraulic power for the A320. It runs on ground during air-conditioning and lighting of the aircraft but also during engines start (the bleed air is used to spin up the engines) and if needed, during takeoff and landing. It then acts to offload the engines and as a backup source of bleed air/power.

The APU has a shop visit for rebuild every 4,500 flight cycles, costing us $270,000. We shall therefore allocate $60 for maintenance of the APU per mission.


The Tires/Wheels/Brakes require the most maintenance on the aircraft. Tires shall be changed as they wear. Tires can be re-threaded four times, after which they get replaced. Wheels need inspection for damage/fatigue and brakes need constant checking/replacement as they wear with daily use.

We shall allocate $20 per cycle for tires, $15 for wheel inspections/replacement and $85 for brakes. In total $120 for the group, per flight.

Rotable support

When the self-test doesn’t pass or when their use limits are reached, system components like pumps, actuators, constant drive generators… need replacement with reconditioned units.

It’s too expensive to stock items for replacement if faulty or keeping extra units for the reconditioning cycle.  Airlines therefore rent access to these components from maintenance providers which offer a Rotable pool service.

For this service, many airlines share the access to pooled units and pay a fee for the access to the pool. In addition, the airlines pay for actual consumption.

We shall calculate $230 per flight hour for Rotables.


If we summarize the total cost for aircraft maintenance for our airline, we shall calculate that each flight hour costs us ~$900. For engines, we shall add ~$450.

3 Comments on “Bjorn’s Corner: Keeping airliners operational. Part 9.

  1. Makes you wonder how Air Berlin can offer ACMI lease rates of 1600-1900€ all in to LH/Eurowings when MRO is that pricey for an A320.

  2. Thanks for the interesting and comprehensive write-up.

    One part was interesting to me regarding the Rotables.

    Surely the largest airlines can afford to keep spare Rotables in stock on an as needed basis?

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