Gripen vs USAF/USN MTBF. Those numbers that circulate on the net suffer from lack of qualification. By having a general idea of the composition and condition of the US jet inventory it is noted that:
As opposed to the Gripens, the US numbers are fleetwide or frontline, the higher average age means more maintenance. The Gripen is quite new. This has to be taken into account.
The US inventory includes twin-engined jets, which require much more maintenance. Engines account for a large part of the maintenance of a jet. The Gripen is single engined. This has to be taken into account.
The US fighter fleet is worked much harder, accumulating flight hours to the airframe faster than any other air force. Gripens generally fly less (30% less?) than the average NATO jet, and the US fly their jets more than NATO does. The 186 Gripens that have been built only reached 100,000 flight hours this year. This has to be taken into account.
As no group of jets in the US inventory can be filtered out from these one-dimensional figures, in order to meet appropriate conditions for comparison, they're of little use (the numbers).
Further, the Gripen has also been compared to the F-18E/F; this is also in circulation on the net, usually together with the MTBF comparison:
* The man hours of maintenance for each flight-hour: 12 man-hours initially, than reduced to 10 man-hours (F/A-18 E/F: 15 man hours of maintenance for each flight-hour).
Somewhat more reasonable: both are 4th gens and are of similar age. However, the SH is twin-engined. If say, maintenance on the engines make up for half the manhours per flight hour of a jet on a
single-engined jet, then they're on par, design-wise. Include the corrosion from sea spray, the heavy handed treatment the SH is subject to from catapulted launches and arrested landings and the more intense use - it suddenly becomes clear that the design and technology of the SH is superior to the Gripen as far as maintenance goes (if one accepts the premise of this metric
).
Also, the GAO report speaks of MTBM (action); a different concept than MTBF. If one wishes to get a metric of maintenance cost on Western jets, maintenance man-hours per flight hour (MMH:FH) would seem a more appropriate metric. A maintenance action can be many things small and big. And I suspect (but do not know) that the bad MTBM for the F-22A is associated with many
small actions wrt to the VLO properties.
Add to that that the diagnostics and logistics system of the F-22A (and F-35) will require the operator to replace items that have
not failed and
outside of scheduled maintenance, in order to maximise mission effectiveness (to minimize critical failures that cause mission abort), which means more realized combat missions per jet or lower cost per combat mission, i.e. optimised for a nation that expects to use the jet in combat and wants cost-effectiveness in this regard (which also means better C-E overall, if the operator actually uses them in combat) and not peace time beancounter numbers.
Lastly, GAO only criticise. IIRC, they don't mention MTBM or MMH:FH - so they must meet their targets... either that or GAO just don't have access to those numbers.