I first saw this blurb March 1st at InsideDefense.com:
The Pentagon last month relaxed the performance requirements for the Joint Strike Fighter, allowing the Air Force F-35A variant to exceed its previous combat radius -- a benchmark it previously missed -- and granting the Marine Corps F-35B nearly 10 percent additional runway length for short take-offs, according to Defense Department sources.My first thought was "well, the F-35A bulls***'combat radius' concern is still floating around I see".
My second thought was "10%? How does that translate into REAL numbers?"
My third though was "I wonder who's gonna 'break' this story as some kind of disaster?"
I see that the Joint Requirements Oversight Council (JROC) elected to change the flight profile to get back the minimum range. Which means they left the fudge factor put in as a tripwire for action. Regular readers would know that the first time this 'news' was delivered to the masses the actual minimum range estimate KPP was not breached, only the safety margin put in place by the program was breached (Which I covered at length here), and then only by a slight percentage.
What does that 'nearly 10%' Short Takeoff distance' increase mean? 50 Feet. The KPP now reads 600 feet instead of 550 feet as a requirement, because apparently the testing and models to-date show the F-35B can 'only' take off in 568 feet under the specified conditions (weight, pressure altitude, winds...)
The short-take-off-and-landing KPP before the JROC review last month was 550 feet. In April 2011, the Pentagon estimated that the STOVL variant could execute a short take-off in 544 feet while carrying two Joint Direct Attack Munitions and two AIM-120 missiles internally, as well as enough fuel to fly 450 nautical miles. By last month, that take-off distance estimate grew to 568 feet, according to DOD sources.So what is the impact of this change? Not much. LHA and LHD flight decks are 844 feet long, and the F-35A/B are ~50.5' long. The difference between a 550' and 568' takeoff run is probably less than a half a degree of temperature or a couple of more knots of wind. As it is, even if the F-35B needs all of the 560' afforded, there's still plenty of room left. For more 'visual learners' the following LHD graphic is provided for perspective.
The comments at Wired are a decent mix. You get about a third of the rabid JSF/Defense-in-general-haters that seem to be the norm over at Military.com these days, about a third of casual observer 'drive-bys' and about a third are having absolutely none of what Axe is selling. the ratio will probably change once the hater bandwagon rolls in. My favorite comment (because it actually cites a credible reference) comes from a 'Tabitha McClane':
Changes to KPPs may also come as a result of cost, schedule, or quantity. Looking at the current JCIDS Manual (CJCSI 3170.01H, A-11) in a discussion of the JROC/JCO tripwire, we find: "The lead FCB will work with the sponsor to assess whether an adjustment to validated KPPs is appropriate to mitigate the changes to cost,schedule, or quantity, while still providing meaningful capability for the warfighter. More detail on JROC/JCB Tripwire procedures are in reference c."This is a good start to a discussion on how KPPs 'work' that maybe I'll have time for tomorrow.
Such changes may be necessary as we learn which capabilities are achievable and which aren't within the cost and schedule targets of a program. There may be other areas to be critical of, but I don't think this qualifies as cheating.
I used to like Axe's stuff - it was naive but honest. Maybe he's just hanging out with the wrong crowd at 'Wired' these days.
Update 7 Mar 12 2000hrs Central: Since I unfortunately don't have time to really get my teeth into the use and meaning of KPPs, I offer instead a great (from a technical POV) source document on KPPs for the truly interested.Read Appendix A of this document (pdf). I was a little beaked with AF Chief of Staff Schwartz over-simplifying the issue before Congress yesterday:
Gen. Norton Schwartz, the Air Force chief of staff, told members of the House Appropriations defense subcommittee Tuesday that reducing the combat radius of the F-35A by five miles is more cost-effective than modifying the fighter to meet performance goals set a decade ago.But then after reviewing the document I just referenced, the old adage about 'explaining', 'enemies', and 'friends' came to mind. Key concept to take away: managing KPPs is all about trade offs and trade space.
I believe at the very heart of most criticism of the F-35 is a conflict that really drives many complaints against modern weapon systems in general. That conflict is between those who believe that weapon systems should be fielded in evolutionary increments and those who recognize the benefit of fielding disruptive technologies. The problem is manifold. The 'incrementers' criticize when a goal is not met according to a schedule developed as a best guess concerning a major technological step before the fact, they do not understand (or pretend they do not) that 'breakthroughs' are not achieved on a precise schedule, and they fail to recognize the full spectrum of costs incurred from fielding alternative 'simple' systems (if they think about them at all). Most importantly they do not look into the future and recognize the fact that if we are not shaping the future to be what we want, the 'other guy' will do it for us.