Nomadd wrote:benbeny wrote:TUGMASTER wrote:
I don’t suppose they ever will....
I think they may not fly that much, but military planes usually stay longer in service than airlines ones. Besides P-8 sometimes fly low flying mission and stay in the air for 8 hours. I wonder will they show premature crack in this area too.
It's cycles they worry about. P-8s don't take off and land six times a day.
Military use is typically more complex than civilian use. More time spent at low altitudes, more maneuvering and higher load maneuvers in normal operations, less avoidance of turbulence, and a lot more training.
The result is different aging patterns in military aircraft than civilian counterparts.
I started looking at this a little bit with regards to the P-3 Orion versus the L-188 Electra it was based on.
Electras served in commercial use for 30,000+ cycles. The P-3 was rated by Lockheed for 7500 flight hours. That right there is potentially telling - that in one use case, the focus is on cycles, and in the other, the focus is on flight hours. The P-3 later underwent several rounds of service life extensions, but also required a fair amount of structural maintenance to do so.
It sounds like for the Navy, the wings were the primary area where fatigue reared its head, not the fuselage.
That experience makes me suspect the pickle forks will indeed need to be addressed for the P-8. However, the P-8 is over a decade newer than the 737NG, and the Navy's ASW flight rate is less than 1000 hours per year, where as commercial airliners operate 3000+ hours per year. I anticipate Boeing will have already developed a long term fix for this by the time the Navy might encounter problems.