Well we need some kind of formal write-up.

Are you still in uni?

I realise that, I began by respectfully pointing out that he was wrong as regards AESA only using one frequency per pulse. If that was the case, it would be damn easy to detect.

ugh.

define a pulse…

Is it the waveform emitted instantaneously? Or over 1 second?

If a radar outputs, say, 5kW, that is, 5 kilojoules per second, Merc is pointing out that it is formed of (say), 100x 50joule pulses which all are at distinct frequencies (for an AESA beating at 100 Hz).

As far as I am aware, no current AESA can use half of its T/R modules at one frequency and the other half at another frequency at the same point in time. The whole lot are used, or a subset of the T/R modules are used, and they are beating over very short time periods to give an aggregate over multiple frequencies.

Sry to insist Amiga500. I know that you are a competent individual but we are dealing here with hot structures with thousands of different parts. Predicting the life expediencies and behavior of such product is nearly impossible without many test being run. Even with multiphysics modeling

Test are usually run and slight mod are made btw.

Yeah sure how would I know… F&DT is just the day job at the minute. :rolleyes:

The tests are run with a particular type of material. These data (along with further historical information) go together to form the material allowables – to which the design is stressed to.

If the material in the engine is not the same as those in the test/design, bringing it into line with what was supposed to be used does not require further testing/design work.

Interesting…

So if its a quality problem like they have claimed, why is there a design change to “fix” the problem?

[Not saying the two are mutually exclusive of course, if a mod helps reduce sensitivity to component quality without somehow sacrificing performance, then its sensible – but its not normal to change two things at once – the first being the component supplier, the second being the component design.]

edit: Ah, it would appear the reason for the ground is a design problem, but there are also separate material quality issues.

Lovely time to be in P&W. Not.

Those who think stealth aircraft designers somehow overlooked low frequency radar are most seriously deluding themselves.

There is a difference between overlooking it and being able to do something about it.

Good question, if uncomfortable for some.

Further clarity on the whole area should be provided as the PAK-DA becomes more defined.

If it is a B-2ski, then the thought-train I have proposed is erroneous. The PAK-FA is what it is because they cannot make the delicate VLO treatments serviceable in the field… so are going for kinematics to compensate for that.

Only picking this up now:

http://www.defense-aerospace.com/article-view/feature/156613/p%26w%2C-others-hid-new-f_35-engine-problems-since-may.html

PARIS — Pratt & Whitney waited three months to publicly admit it had suspended deliveries of the engine that powers the F-35 Joint Strike Fighter, and only went public on Aug. 30, the day after Bloomberg News broke the story.

Pratt also waited until Aug. 29 to file suit against the supplier it accuses of having supplied sub-standard materials, which it says it detected in late May. Pratt’s statement also says it “is conducting a rigorous analysis of the material in question,” so it is not clear on what grounds it states “we are no longer accepting parts made from material provided by this company.”

Whatever the details, it is stunning to think that this delivery freeze has been kept secret for over three months, given this engine’s long history of problems, and the entire F-35 program’s troubled history of under-performance, cost over-runs and long delays.

…..

All of the above paints a pretty dismal picture of the credibility of the F-35 program and of the ease with which it manipulates the media. But the media is not alone is having been misled:

— Witnesses during June-July hearings by four congressional panels on the FY2015 budget also neglected to mention the engine delivery freeze. The cover-up is a slap in the face of these panels, whose reaction this week will be indicative of how seriously they take their oversight role.

— Was the British government, the biggest foreign partner in the F-35 program, informed of this latest setback, and did it join the cover-up? Was this the reason it didn’t sign the 14-aircraft order, as expected?

— Was the Italian government, the second-largest foreign partner, informed, and were the six other foreign partners who have contributed to funding development? Were they kept deliberately in the dark, or did they join the cover-up?

In other words, is this an international conspiracy to protect the F-35 from parliamentary and public scrutiny, or is it simply a domestic cover-up in the US?

The cover-up also raises shareholder information issues for Lockheed Martin and United Technologies, Pratt’s corporate parent. Lockheed, for example, makes no mention of the engine freeze in its July 22 statement on second quarter results, although the F-35 program is so crucial to its future that it is specifically mentioned in its “Forward Looking Statement” regulatory warning.

Depending on the scope of the issue, this could be pretty serious stuff. If the foreign investors were not told – why would they trust the word of those in charge of the program again?