A new aviation abbreviation with an F in it has entered the scene. Okay, it's probably not new to aircraft structural engineers, but I only recently noticed WFD for the first time, in a new FAA rule that requires manufacturers to declare and operators to comply with life limits on airframes. The lifespan of an airframe may be given in hours or cycles, but there is a possibility of having an individual aircraft approved for an extension. The term limit of validity (LOV) refers to the engineering data specified about the airplane. Its an addition to the published limits that certification requires an aircraft to be operated within. The rule applies to existing designs with a takeoff weight of at least 75,000 pounds, and to all transport designs seeking certification in the future.
I think in most North American operations, large aircraft become uneconomical to maintain before they reach their LOV. The rule itself states that there will be only one current airplane affected, at a cost to its operator of $3.8 million dollars, but that the new rule will save the industry $4.8 million. I believe that the savings are from changes in inspection programs, but I'm not certain. I've been sitting on this for a while, intending to do more research, but I've been learning Khmer and getting my taxes in order instead. The link to the rule given in the ASN article is broken, but I found it here.
Usually when an aviation abbreviation contains an F, it doesn't stand for fatigue. A while ago I used some netspeak in an e-mail conversation with another pilot who hasn't spent as great a proportion of his life online as I have, and he wrote back to ask me to clarify ROTFL. He said he could have asked his daughter, "but it had an F in it, so I thought I'd play it safe." In this case, it's "rolling on the floor, laughing," but his caution was well-placed.