New problems disclosed on 2 models of F-35

New problems disclosed on 2 models of F-35

By Dave Majumdar@Navy Times - Staff writer
Posted : Tuesday Jan 18, 2011 17:22:53 EST

The F-35 Lightning II strike fighter has previously undisclosed problems with its handling, avionics, afterburner and helmet-mounted display, according to a report by the Pentagon’s Director of Operational Test and Evaluation.

Both the Air Force F-35A variant and Marine Corps’ F-35B model experienced “transonic wing roll-off, [and] greater than expected sideslip during medium angle-of-attack testing,” the report said.

The report also says that various components are not as reliable as expected.

Additionally, the Pratt and Whitney F-135 engine has encountered an afterburner “screech,” in which airflow disruptions cause severe vibrations, preventing the engine from reaching maximum power. That problem has delayed some required testing.

According to the report, the program has already begun efforts to fix the problem. Pratt and Whitney officials were not immediately available for comment.



Further, the report indicates problems with the aircraft’s helmet-mounted display. Unlike many previous aircraft, the F-35 does not have a cockpit-mounted head-up display; the pilot instead views critical data projected on the helmet visor.

The report does not elaborate on the nature of the problems, but says they must be solved before the Block 2 mission systems software can be tested. Currently, the program is testing preliminary Block 0.5 and Block 1 mission systems software. Block 2 would incrementally increase the aircraft’s capabilities and would be followed by the fully mission-capable Block 3 software.

A Lockheed Martin official could not immediately describe the technical problems with the display.

“The F-35 air system advances Helmet Mounted Display technology to capabilities not flying today on any other tactical platform. With this advancement in technology come challenges that the program is actively managing. The challenges are being worked with the supplier,” said Lockheed Martin spokesman John Kent.

“While there are no current plans to change suppliers, options are being considered in parallel that mitigate the most stressing issues. Flight testing is proceeding with the HMD installed and used with no safety of flight concerns.”

The report also calls for the Block 3 mission system software to be tested on a simulated battlefield because existing test ranges are not adequate to test the F-35’s sensor arrays.

“Open-air testing is constrained by range limitations that are incapable of providing realistic testing of many key capabilities provided by Block 3 aircraft,” the report says.



The report also calls for the aircraft’s On-Board Inert Gas Generations System, which generates inert gases to prevent oxygen building up inside the fuel tanks, to be redesigned.

“The OBIGGS system fails to inert the fuel tank ullage spaces throughout the combat flight envelopes evaluated,” the report says.

The report recommends program officials redesign the OBIGGS system “to ensure that the fuel tank ullage volume oxygen concentrations are maintained below levels that sustain fire and/or explosion throughout the combat flight envelopes.”


These issues are in addition to the known difficulties with the B-model aircraft’s insufficiently strong structural bulkhead and problems with auxiliary air inlet doors on the aircraft’s top surface.


http://www.navytimes.com/news/2011/01/m ... um=twitter

A number of these issues have already been fixed or a fix has been identified.
Maybe we should have a running list of problems and their corresponding fix so that they don't keep getting resurrected?
Some of these had fixes implemented while others are still being addressed.
Anyone can feel free to add to the list.


B Variant bulkhead crack
B Variant Hinge doors
Afterburner Screech
A & B variants transonic wing roll-off/sideslip during medium AOA testing
HMD issue

[Oops I see 'popcorn' has answered - I'll look for the PDF link] I guess no one reads anything ELP posts but here it is again:

[via: http://www.f-16.net/f-16_forum_viewtopi ... rt-15.html]

"New design change raises pressure on future of F-35B variant"

DOD Test Report: http://www.f-16.net/f-16_forum_download-id-13920.html

Don't forget the last on on the list (the OBIGGS ).

How about the OMYGOSH!?

More info on the screech problem, and it's fix.

According to Pratt spokeswoman Stephanie Duvall, a fix has in fact been found. And she provided a fairly detailed description of the problem:

“During development testing of the F135 in the May 2009 time frame, P&W found that at low altitude and high speed, certain pressure pulsations occurred when operating in full afterburner. This phenomenon, known broadly in the industry as screech, has been addressed with design modifications that have been validated to eliminate the issue. The modifications include minor hardware changes to the fuel system, reduced aerodynamic leakages, and upgraded software. The design of these modifications benefited greatly from the tools and processes developed in the design of the F119 engine that powers the F-22. The F119 and the F135 are the only two production engines that have provided augmented, stealth capability. With the modifications identified and implemented, the F135 now provides full max augmented thrust throughout the flight envelope. For the SDD program, a kit has been developed that brings these modifications to the engines that are powering the flight test program. Two engines have been modified to date with the design showing excellent results. The production configuration is being validated this year in both the CTOL/CV and STOVL variants of the F135. Confident that the F135 was providing the full required thrust throughout the flight envelope was just one of many reasons the government certified the CTOL/CV engine for Initial Service Release (ISR) in March 2010 and the STOVL engine achieved ISR in December 2010.”

Read more: http://www.dodbuzz.com/2011/01/19/f135- ... z1BWorciOE

Good to know.

... and nobody believed me when I said PW had it under control and it was a non-issue?...

TEG

That_Engine_Guy wrote:... and nobody believed me when I said PW had it under control and it was a non-issue?...

TEG

HMD issue, Ah no not yet... We still aren't happy. But it's getting better

Any idea what the HMD issue is?

nothing that can't be fixed !

Well I knew that

I was just wondering if you knew what the problem was.

let's call it stability, HTU SW should fix, got a TD box in HMD and they're loving it

That_Engine_Guy wrote:... and nobody believed me when I said PW had it under control and it was a non-issue?...

TEG

You'd say that about a PW product if it wasn't.