airomerix
PDF THINK TANK: ANALYST
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Why would be it difficult to hide that 40 percent of 1 particular jet fighter is grounded in 2 airbases through out the country?
No one outside the base and many inside would not even know this .
I have been following defence news from around the world for more than 1.5 decades...yet I did not know ..that fighter aircrafts like ships use strakes for strengthening the airframe or the fact lower fairing skin of an aircraft is most susceptible to g- loads.(both of these mentioned in the OP). I am sure none of you did either.
This kind of innate knowledge about aircraft structural components is not possible for an average journalist to know.
Which lead me to believe this information was either gathered from some PAF internal report to Pakistani government ..or from someone who had direct access such a report.(eg a government clerk, who was paid off by this journalist)
I dont blame you for not knowing about aircraft structures. The fact is, similarly to this funny report, you are ill-informed, and hence, the three words (read: lower fairing skin) have lead you to this conclusion that the report is legit and indeed JF-17 has structural challenges. Also. These couple of posts has exposed your ignorance or your propaganda. You'll have to choose one.
Now allow me to educate you.
Lower fairing skin is a very broad term. It's like someone is saying that the vehicle was undrivable due to a fracture in the lower chassis. Does it sound like a 'leaked report' to you? Besides, had it been anything other than some routine propaganda by Godi media, the report would have outlined the exact type of defect such as compression, torsion, bending or tension induced marks in lets say lower longerons at xyz point in the 'wing to body fairing' and so on. Focus on the specifics for a change.
So what you're quoting as 'innate' knowledge reflects your own lack of understanding of the subject or the esteem you hold PAF investigation reports at.
Well if the news is true ..then it's worrisome news for PAF in regards to quality of materials used by Chinese for JF 17 construction.
A f 16 airframe has a structural life 8000 hours for 9g manouvers ..which can be increased to 12000 hours.
A Mirage 2000 airframe has a structural life 7500 hours.
A Tejas airframe has a structural life of 9000 hours due to large use of composite materials( 40 % of the aircraft is made of metal - silicon carbide matrix ..which makes it much lighter than Aluminum and and much stronger than it) and use of HUMS to measure airframe fatigue.
A Jf 17 airframe already has a low life span 4000 flying hours..due to all metal airframe.
Where as most JF 17 have not even completed 1000 hours of flying time and the airframes are already developing stress related cracks.. clearly some corners were cut in metallurgy to keep the costs low and production fast.
Structural failure is never an easy fix.. especially due to lack of Hull mounted sensors to measure airframe fatigue on Jf 17. Hence it will require a lot of close up inspections ..a long time being laid up..won't be cheap either...but most of all ..it does not bode well for the life span of the aircraft.
I will not debate with you on the xyz number of flight hours and the structural life of the airframes due to the simple fact that you have your facts wrong. Now lets get educated on the basics.
First of all, this so called lower fairing skin (if i'm imagining this broad term correctly) is made of semi-monocoque structure (google if you dont know about it, i'm not your full time professor). However, the wings and rudders of both JF-17 Block 1 and 2 have composites with Block 2, Bravo featuring increased composites usage in other areas (classified) to reduce weight.
On the contrary to what you have said about structural failures, The ease of aluminum sheet metal repair has remained unchanged since the past 60 years or so. The machine tooling and associated processes have remained the same. On top of it, the technical expertise required to fix/repair an aluminum (as opposed to composites) is also minimal and less complex.
Let's say, in an event of a bird strike on the aluminum part, the technician will examine the dent and assess if it is on the stringer or rib, and will consult with that 60 year old manual. If the dent remains within tolerance, it will be left untreated as it poses no danger. If it remains outside tolerance, it is simply patched with another alumnimum sheet. Even damage on top of supporting structures are relatively inexpensively inspected by non-destructive inspection or testing (NDI/NDT) by the use of ultrasonic testing.
Final comment;
Some of your general comments about JF-17s cost-effectiveness vis a vis service life are correct. The reason is, JF-17 was made from the ground up with a modular concept. Like F-16, it has practically no such thing as service life. At the end of 4000 hrs, a simple upgrade (such as FALCON STAR for F-16) will increase its life to 8000 hrs, and so on.
Why do you think B-52s are still flying? Did they not reach their service life decades ago? The catch is, when an aircraft approaches its service life, the Air Force has to do a cost-benefit analysis of whether to discard it, or rebuild it. This is exactly where PAF wins. JF-17 is our home grown fighter. We have the option to discard its airframe at little or no significant costs and chew out a newer frame in less than 15 days if needed.
Lastly, some of the figures you have quoted about 'service life' actually belong to the type of aircraft engines and not aircraft structure per say. I will leave you the embarrassment of its correction. Go figure.