Forum: F-35 milestones

Driving home from work, I have seen and heard the F-35C on three separate occasions. If you are familiar with the area in question, it was on Route 539 South in the McGuire/Fort Dix area, where they put up that new repair depot facility. On all three occasions it was within 1-2 miles of this new facility that is directly visible from Route 539. I can say that the jet is pretty loud; definitely military sounding, which of course it is. The engine seems to produce a more thunderous noise, even at a distance. On one of the occasions, he must have been about 1,500-2,000 feet away from where I was at about 800 feet AGL. He had his gear and flaps down and was turning ~SE to shoot an approach to Lake Hurst Naval Air Station. The interesting note is that on all of the occasions, I was able to hear the aircraft, even with the wind/road/engine noises at up to almost 65 mph. One of the passes over the road was quite loud as he must had a higher throttle setting selected. Talk about being lucky! These incidents occurred as recently as two to three weeks ago from the date of this post and almost exclusively occurred within the 5:45-6:10 PM EDT time range.

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Better Quality Front On View of first F-35C steam catapult along with some talking heads including Lt. Tabert:

NAVAIR Flight Crew: F-35 Joint Strike Fighter Test Pilot

http://www.navair.navy.mil/index.cfm?fu ... E9C213A6B0

We get to see a good view of the layout of the centre steam catapult and on the right of the photo below we see the EMALS catapult

How about an arresting gear test landing? Smile

Probably not untill the redesign is done. Not worth risking an entire airframe on somthing they know wont work.

navy_airframer wrote:

Probably not untill the redesign is done. Not worth risking an entire airframe on somthing they know wont work.

in another thread; http://blogs.star-telegram.com/sky_talk ... inter.html

The tail hook mechanism failed all eight landing attempts in tests and requires significant and, apparently, challenging redesign of the system and perhaps the aircraft structure itself. “If this change is not successful there is risk for significant airframe structures redesign and or impacts to overall” radar signature, the report said.

generally speaking "What Happened?, 8-0 Sad

".

@Neptune, I am not expecting any news on that till January or Febuary.

Just to give you an idea on how difficult it is to design a tail hook system check out this old document. Don't worry about the equations, just check out the pictures in the back, which will give you some idea of how difficult a task this is.

http://naca.central.cranfield.ac.uk/reports/arc/rm/2980.pdf

I'm sure it looked good in the computer design and simulations otherwise they wouldn't have built the thing.. nothing like actual testing in the real world though.

[quote="alloycowboy..Just to give you an idea on how difficult it is to design a tail hook system check out this old document. ...[/quote]

http://www.aviationweek.com/aw/blogs/de ... d=blogDest

..wading thru BS's bs you can stumble upon a piece of info;

...1- hook profile; The arrester hook issue has been reported. In the first round of tests, the hook failed to catch the wire once. The QLR notes that tests of a minimal modification - a reprofiled hook with different damper settings - set for April "represent only the initial stages leading into full carrier suitability demonstrations."

2- hook location; Studies are already underway of changing the hook's location - the basic problem is that the designers put the hook closer behind the main landing gear than that of any current or recent Navy aircraft, ....- but that will have "major, direct primary and secondary structural impacts".

Confused

Last edited by spazsinbad on Dec 13, 2011 - 09:13 PM; edited 1 time in total

Thanks 'neptune'.
The POGO PDF mentioned via AvWeek post immediately above may be downloaded here:
http://www.f-16.net/index.php?name=PNph ... 331#210331

F-35 Joint Strike Fighter | Concurrency Quick Look Review | 29 November 2011

specifically: http://www.f-16.net/f-16_forum_download-id-15184.html (5Mb)

neptune wrote:

navy_airframer wrote:

Probably not untill the redesign is done. Not worth risking an entire airframe on somthing they know wont work.

in another thread; http://blogs.star-telegram.com/sky_talk ... inter.html

The tail hook mechanism failed all eight landing attempts in tests and requires significant and, apparently, challenging redesign of the system and perhaps the aircraft structure itself. “If this change is not successful there is risk for significant airframe structures redesign and or impacts to overall” radar signature, the report said.

generally speaking "What Happened?, 8-0 Sad

".

Wasn't designed as a naval aircraft from the start....

Question, and a serious one at that, we know that the Navy has been the least gung ho service about the F-35. They've maintained F-18 development (Growler) and have continued to express interest at the F-XX (look at Boeing's fairly desperate efforts to push a F-XX for the Navy, Boeing would only do that if it felt that the Navy was going to be more sympathetic).

Here's the kicker: does this report, particularly the rather serious section on the tail-hook, make the USN go for a different airplane? Its happened before, look at the F-111 which morphed into the F-14. And, remember that the F-35 isn't as well suited to the Pacific theater as it could have been.

Does this report make the Navy want to strike out on its own, build a dedicated carrier fighter with the F-35 tech but not the structural problems? There are obviously pros and cons to this question, but given the severity of this report, I wonder what people think now.

Text about the F-35C HOOK is from the report cited above (cites some of the diagrams/photos seen above).

FOUO//US ONLY
Arresting Hook System (CV variant): There are significant issues with respect to how the CV variant’s AHS interoperates with aircraft carrier based MK -7 arresting gear. Roll-in arrestment testing at NAWC-AD, Lakehurst, resulted in no successful MK-7 engagements (0 successes in 8 attempts). Root cause analysis identified three key AHS design issues: (1) the aircraft geometry has a relatively short distance between the aircraft’s main landing gear tires and tailhook point (when lowered), (2) tailhook point design was overemphasized for cable shredding features versus ability to scoop low positioned cables, and (3) tailhook hold-down damper performance is ineffective to support damping of small bounces relative to runway/deck surface profiles.

As shown in Appendix Figure 8, page A-9, the F-35C’s main landing gear to tailhook point distance is 7.1 feet. Accordingly, when the aircraft’s main landing gear rolls over the arresting cable, the responsive dynamics are such that the cable lies nearly flat on the deck. Comparing similar geometries with other, currently operating carrier based aircraft which range from 30.2 feet (C-2) to 14.6 feet (T-45), the F-35C is an outlier. The current F-35C tailhook point design (Appendix Figure 9, page A-10) was based on the F/A-18E/F design which has a blunt face to better provide cable shredding protection versus scooping. However, the F/A-18E/F’s geometry places the distance of its main landing gear to tailhook point at 18.2 feet; a much longer distance than the F-35C. Since there is more distance in the geometry, the trampled cable has enough time to respond and flex back toward its original setting position by the time the tailhook point intercepts for arrestment. The hold-down damper contributes to overall aircraft arresting gear poor performance by allowing the tailhook to bounce excessively.

To address these issues, the program is designing modifications to the tailhook point and hold down damper components. The proposed hook point redesign in Appendix Figure 10, page A-11, both reduces the blunt face geometry with a more pointed front end and lowers its apex point by 0.5 inches (68%) such that it is now below the arresting gear cable centerline to better enable scooping performance. The proposed hold down damper redesign will consist of modifications to the AHS actuator damper such that a lesser number of orifices will temper tailhook bounce dynamics (Appendix Figure 11, page A-12). The AHS redesigned components will undergo Monte Carlo probability of engagement analysis as a leading effort for design review which is scheduled in December 2011. Following successful design review, the plan is to manufacture the redesigned components and then conduct rolling engagements at NAWC-AD, Lakehurst in April 2012.

With corrective action still in development, the AHS is considered an area of major conscquence. If the proposed redesigned components do not prove to be compatible with MK-7 arresting gear, then significant redesign impacts will ensue. Accordingly, the program is conducting a formal trade study to assess options beyond AHS redesign. One option includes adjustments of AHS airframe location. However, since arrestment loads are significant and the aircraft has certain constraints with respect to engine location and survivability considerations, any readjustment of AHS location will have major, direct primary and secondary structure impacts.

Since rolling engagements in April 2012 represents only the initial stages leading into full carrier suitability demonstrations of the F-35C, complete knowledge of how truly compatiblc AHS redesigned components perform under nominal and off-nominal approach to engagement conditions will not be realized until well into the program’s developmental test timeline. This issue represents a major concurrency risk which would have a significant retrofit impact to LRlP aircraft already delivered a large re-adjustment to the current F-35C production process build-up flow and, in many aspects, invalidate previously obtained developmental test and evaluation data.

Conclusion: Major Concurrency Risk – Significant redesign risk and options are unknown at this time.”

Be sure to look at section I. There is a very important statement in there. Also, don't forget what happend to the C-17 around this time in it's testing.

Sufa Viper

sufaviper, thanks for getting us to read all the very important statements in section 1. Which one is it?

spazsinbad wrote:

...... If the proposed redesigned components do not prove to be compatible with MK-7 arresting gear, then significant redesign impacts will ensue. ......”

It looks like the hook was well designed to "NOT" engage the cable; 8-0 (rather effective!).

Whether the MK-7 or the AAG is used, the cdp lays on the deck, in all worse cases. Looks like we will have to wait to April to see if the sky is falling! Laughing

Forum: F-35 milestones

F-35C Lands at Lakehurst For Testing