|Quoting LMP737 (Reply 11):|
And why is that? It's rather simple, the F-35 program is a grossly mismanaged program that is years behind schedule and billions over budget. If the opposite were true most of those planes you speak of would have already been replaced.
1. Aircraft development times extending into decades isn't new. Look how long it took to develop Eurofighter, Rafale, Gripen, and the F-22. If your aircraft development time is fairly short, it means you are reusing a lot of existing technology and components.
2. The USN
when they developed the F/A-18 treated the design as a sort of a throw-away fighter back during the Cold War. Once the aircraft hit the original design life expectancy of 6,000 hours, the airframe was to be disposed of, and the USN
would simply buy a new aircraft. Once the Cold War ended, the USN
had to retain the F/A-18's in service, and service life extension was implemented to extend service life to 8,000 hours. That's being extended again.
Furthermore, the USN
has a different fatigue standard for aircraft than the USAF
. The USN
uses fatigue to determine the structural safety of their airplanes. Basically, that means if a structural crack is spotted, the airplane is deemed unsafe and is immediately grounded pending a decision to repair or retire. When the USN
designs their aircraft, in the design and development phase, fatigue analysis and ground test is conducted to 4 times the expected airframe life expectancy based upon expected usage. This means for an 8,000 hour airplane, it must pass 32,000 hours without cracking. Due to the extreme variability of fatigue analysis and test and variability in actual usage compared to design usage, the USN
allows only 1/4 of ground test lifetime as the rated design life of the airframe.
When any crack appears, a failure is declared, and corrective action is taken on the design, usually beefing up or redesigning the structure(s) involved.
uses a different and more modern fatigue standard; it's called Fracture Mechanics. Under this standard, crack growth is analyzed, tested, and tracked during service usage. Due to the much higher knowledge base of fracture mechanics, cracks are permitted in flying airframes until they reach a critical length, upon which the airframe is either repaired or replaced. Analysis and ground tests during the design and development phase are conducted to two airplane lifetimes, compared to four in Fatigue criteria.
The point to take home is that USAF
airplanes are allowed to fly with safe cracks and the USN
airplanes are not. The USN
method does add costs because it forces the USN
to either retire or conduct service life extensions at a much more frequent rate than the USAF
would for a similar design.
It's interesting to note that all variants of the F-35 are being tested to the USN
fatigue standards, not the USAF
's standards. That's why when you hear about cracks appearing in the F-35, it provokes an immediate redesign and beefing up of structure in the design.
3. The extended design phase of the F-35 is caused primarily by the US government and DoD, not the manufacturer. As I mentioned in other threads:
60 Minutes On F-35 JSF (by ThePointblank Feb 16 2014 in Military Aviation & Space Flight)
[Edited 2015-06-30 00:31:10]
|Quoting ThePointblank (Reply 8):|
The problem is that delay was due to issues with government oversight and customer requested design changes. There’s been ~5-6 years IOC delay as a result of this.
One year was from taking 3 instead of 2 to fully staff the program. I blame Lockheed Martin for thinking they could do it in 2 years when it’s always taken 3 years for a program this size and they knew it wouldn’t be done any differently than before, and I also blame the Program Office for believing it. The blame goes both ways here.
Then there was ~2 years for what is commonly referred to as the ‘weight reduction’ redesign which in reality was a recovery from an ill-conceived design requirements change between the technology demonstrator program and the award of the contract to Lockheed Martin.
Basically, very early on after the contract award, someone modified and approved the specs that specified that all three variants of the F-35 share the same weapons bay size, meaning that all three variants would have been capable of handling 2000lb class weapons internally. Originally, it was only the F-35C that was required to be able to handle a 2000lb class weapon while F-35A and F-35B only required 1000lb class weapons. It was few years later well into design and prototyping did everyone realized that as a result of the design change, F-35B was going to be overweight, so they changed the specs back to requiring internal carriage for a 1000lb class weapon in each weapons bay. But as a result of this late change, some components had to be extensively redesigned to accommodate the change and to save weight.
I presume this was a Customer idea, because if it had been a Contractor one, the Contractor would have been thrown under the bus by the Customer (e.g. A-12 Avenger II) by now. That's why I believe that no one was playing the blame game between the DoD and Lockheed Martin because if they did, the DoD probably knows full well they were the ones that caused the problem in the first place.
Now add about 2-3 years (so far) as a result of Congress and DoD choosing to stretch the program for dubious reasons (cough, *Concurrency!*, cough), and there’s your ‘dogging delays’, ‘cost’, and ‘redesign’s all rolled up in three events. Just about everything else that has happened on this program has been a mere side show in comparison.
[Edited 2015-06-30 00:31:37]