Forum: General F-35 Forum

@Johnwill, I still wish you would do an interview with Air and Space Magazine about your experiences testing aircraft as you have to much knowledge not to share.

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johnwill wrote:

A valuable statement, thanks. But none of which helps to explain why there may be unverified loads used in F-35A static test or why the pace of flight loads test seems so slow.

It's human nature for each generation to think they invented the wheel, so to speak, and that previous generations had it so easy. None of that messy integration stuff. Since you have no idea how airplanes were developed thirty, forty, or fifty years ago (I doubt you were even around then), let me be the first to break the news to you - considering the primitive tools available, the engineers of those days were giants who developed the methods and tools you use today. And the generation before them developing WWII airplanes with slide rules only. Try doing F-16 load analysis on a HP-9820 desk top calculator, try writing down thousands of items of test data on paper spread sheets during structural lab tests. You think "legacy" systems had comfortable margins? If the F-111 SWIP program (already mentioned) had not been successful, that Plant 4 you work in would have been used for grain storage for the past forty years, with no F-16 or F-35 program.

You are right about the current generation being risk averse now. Sometimes I think it is more CYA than anything else. You might be shocked at some of the risks taken in the F-16 flight test program, yet no pilots or airplanes were lost in development.

Integration? You mean like when we did a tape to add a smart weapon to the inventory, finished the testing, and then discovered that the vendor building the interface box was on a different update cycle?

One of my favorite tasks was decoding the hex values into status bits on the weapon's bus during SMS OFP testing, by hand.

Bottom line, the advantage we had in the old days was just "git 'er done". Smile

fisk

alloy...

Thanks, but that's what I'm trying to do here.

fisk,

That does sound like integration.
About "Git 'er done", right you are. Even the customer in those days was much more willing to let us get the job done, rather than micro-manage us to death.

LMAggy,

Sorry you were offended, not intentional.

F-35 airframe completes the journey of a lifetime ASDNews: Sep 19, 2012

http://www.asdnews.com/news-45047/F-35_ ... fetime.htm

" • Eight thousand hours, or one complete lifetime of durability testing is now complete on the F-35 conventional takeoff and landing (CTOL) variant.

Durability testing of the CTOL airframe to 8,000 hours was completed ahead of schedule, proving the airframe is able to handle a variety of flying conditions it will experience when in service. Work continues on schedule for proving the aircraft for up to two lifetimes or 16,000 hours.

The 350 tonne structural test rig at our Brough facility was purposely built to ‘fly’ the F-35 through a series of flight scenarios. Over 20 miles of wiring, 2,500 strain gauges and 160 loading actuators subject the aircraft to a range of loads that it would typically encounter in actual flight.

We are also contracted for the static and fatigue testing for horizontal tails and fatigue testing on vertical tail.

Fifteen per cent of F-35 Lightning II work is carried out in the UK and over 130 British companies contribute to the supply chain. It is worth over £1Bn to UK industry each year and will support around 25,000 British jobs over the next 25 years.

Source : BAE Systems PLC (LSE: BAES.L)"

http://www.asdnews.com/data_news/ID45047_600.jpg

Paging John Will, a little play by play commentary if you please sir....

alloycowboy wrote:

Paging John Will, a little play by play commentary if you please sir....

Just time for a brief comment. I'm on vacation in Half Moon Bay, CA and have to catch a plane for DFW tomorrow morning. My wife is waiting for me in the hotel room so we can go eat dinner.

Durability testing is somewhat more forgiving of un-validated loads since there are so many more conditions tested (thousands compared to less than a hundred in static test). So there is a good chance some are higher and some are lower than the true load condition. Also, everyone in durability engineering understands that the durability test is a baseline condition and no specific airplane will fly that exact load spectrum (load magnitude and number of occurrences). So crack growth rates and the resulting lifetime from DT are adjusted for the real load spectrum of EVERY F-35A to ever fly. If a particular airplane has a less severe actual load spectrum than DT, it can have longer structural inspection intervals, thus saving support cost and downtime. If a particular airplane has a more severe load spectrum than DT, then its inspection intervals must be shorter.

Note in the press release, it says the airplane will be tested to two lifetimes DT. That is the standard for inspection intervals. If some part of the airplane cannot pass the two lifetime standard (16000 hrs), inspection intervals are adjusted to one half of the total hours passed. Sometimes it is cheaper to replace parts at say, 2000 hr intervals rather than completely redesign and re-validate it. F-16 LEF power hinges a case in point.

The point is DT is a baseline and not intended to replicate the real usage of the airplane. Every airplane will have a different usage. On the other hand, static test is designed to build a limiting box around all load conditions, so that no airplane will exceed the 100% static test loads - ever. That condition cannot be met if ther ST load conditions are not verified by flight test.

If there is more discussion, I will offer more comments after I return home.

[quote="fiskerwad"]

johnwill wrote:

A valuable statement, thanks. But none of which helps to explain why there may be unverified loads used in F-35A static test or why the pace of flight loads test seems so slow.

It's human nature for each generation to think they invented the wheel, so to speak, and that previous generations had it so easy. None of that messy integration stuff. Since you have no idea how airplanes were developed thirty, forty, or fifty years ago (I doubt you were even around then), let me be the first to break the news to you - considering the primitive tools available, the engineers of those days were giants who developed the methods and tools you use today. And the generation before them developing WWII airplanes with slide rules only. Try doing F-16 load analysis on a HP-9820 desk top calculator, try writing down thousands of items of test data on paper spread sheets during structural lab tests. You think "legacy" systems had comfortable margins? If the F-111 SWIP program (already mentioned) had not been successful, that Plant 4 you work in would have been used for grain storage for the past forty years, with no F-16 or F-35 program

You are right about the current generation being risk averse now. Sometimes I think it is more CYA than anything else. You might be shocked at some of the risks taken in the F-16 flight test program, yet no pilots or airplanes were lost in development.

Yeah, and the older generation always thinks there is no more new knowledge. Wink

However, the price of progress is risk, and risk aversion is now codified as curriculum in all of our institutions of higher learning -- it's called 'systems engineering.' All good things can be taken to bad extremes and Systems Engineering is but one curtain that bureaucratic wizards use to cover their bottoms.

JW, you're not the only one who walked thru 17 miles of blowing snow in bare feet -- alone -- to get to kindergarten...and lived to brag about it on F-16.net. Cool

quicksilver says:

static testing to 150 DLL did not really complete static testing, it merely verified the accuracy of the analytical load predictions prior to the beginning of loads flight testing

Yeah, and the older generation always thinks there is no more new knowledge.

JW, you're not the only one who walked thru 17 miles of blowing snow in bare feet -- alone -- to get to kindergarten...and lived to brag about it on F-16.net.

And I nominate you as the originator of the most inane statements ever on F-16.net Shrug

Forum: General F-35 Forum

F-35 testing turned full circle UK StructuralWise