F-35C Lands at Lakehurst For Testing

[quicksilver]

You would think the so-called 'SME's from NAVAIR who participated might have done the same. Seems they have had problems with X-47 also.

http://www.janes.com/products/janes/def ... 1065971296

[maus92]

For the record 'hold down damper' is an OK term for the incorrect 'damper' - as mentioned the 'hold down damper' (or a similar OK descriptive term) is not a 'damper'.

There is also another term, "snubber" that seems to be used:

"The hook is hinged from the structure under the rear of the aircraft. A snubber, which meters hydraulic fluid and works in conjunction with nitrogen pressure, is used to hold the hook down to prevent it from bouncing when it strikes the carrier deck..."

http://navyaviation.tpub.com/14018/css/14018_26.htm

[quicksilver]

The system used for testing this year was a modification of the baseline, not a production version of the redesign. One of the goals of the testing was to verify the predictions of the analytical model they used for the redesign. IIRC the modified baseline was 100% on something over 80 roll-ins. What was not stated clearly wrt the fly-ins is that the target touchdown points for the bolters were consistent with the predictions of the model -- iow, the model said that the probability of a bolter at a given touchdown point was X, they targeted that touchdown point, and the system reacted largely as modeled. For this testing (at Lakehurst) there was only one CDP.

[SpudmanWP]

My point was that the F-35 did not bollter "most" of the time, but only 3 out of 8 times (37.5%).

The original quote made it seem that it boltered 5 of 8 which would be "most".

[quicksilver]

You are correct. It was 5 for 8 on fly-in arrestments. The bolters were predicted given the touchdown points.

[spazsinbad]

'quicksilver': Thanks for the clarifications about one CDP etc. However there is only one emergency land arrestor wire on rubber gromments and one would gather engaging that reliably under all nominated conditions is important. We await proper redesigned hook testing results.

Testing a half redesigned hook is one thing - but the bolters are not going to be tolerated when the completely redesigned hook is tested. I have no issue with the bolters with the half redesigned hook acting according to predictions. Now they get on with the complete redesign that minimises all bad outcomes. Yes there will be the odd bolter every now and then especially onboard but should be negligible ashore with the emergency gear. Anyway the pilot can always eject in these circumstances if the emergency gear missed.

My comment about the 'sergeant's "most"' was sarcastic. Should have used the <sarcasm> tag. My bad.

Yes down the years and in different navies the same equipment can have different names. Notice I never call the 'cross deck pendant' that or CDP. It is a bleedin' wire mate. And never in my wildest dreams would I call our esteemed carrier a 'boat'. NEVER. However I would want to open the windows onboard and such like just to pis off the 'fish heads' (regular navy chaps). We were birdies.

[spazsinbad]

'maus92' 'alloycowboy' posted the URL to that excellent PDF on page 3 of this very same thread:

http://www.f-16.net/index.php?name=PNph ... 26462ae091

And still my point is 'anything but "damper"'. It is just WRONG.

[spazsinbad]

'quicksilver' scroll down page 13 of this thread to see the same information about X-47B issues:

http://www.f-16.net/f-16_forum_viewtopi ... t-210.html

[SpudmanWP]

Spaz, when you have a few hours to spare go to the Tailhook 2012 site and watch the videos. They stated that the 5 out of 8 was above average. Also they covered a lot of other issues like cost of ownership, AARGM, etc.

[spazsinbad]

SWP, thanks - yes a great discovery - it will be a great thread to view once I have a computer with sound. Should be soon enough. I'll freely admit that I (and most other civilians) are not privy to the actual test details. However I'll say in another way that yes the tests were successful with the 'hold down damper' being unmodified and these tests confirmed test predictions. Because the pilot did not land in the zone sometimes (where the GOODLY IMPROVED HOLD DOWN DAMPER will take effect soonish) because the current 'hold down damper' is not as effective as the new improved one should be - then there was a hook skip bolter ON A SINGLE WIRE apparently. Still not good enough as explained but I trust now that predictions good then the new hold down damper will be effective to enable a single wire arrest (as might be the case ashore). Of course onboard if a pilot lands with the ball high then the hook will miss the no.3 wire and land perhaps between no.3 and no.4 making only one wire a target in effect. One would hope there is an excellent chance to catch this last wire also.

[SpudmanWP]

Seriously, no sound?

Spend $3 and get a driverless USB sound dongle. It uses standard headphones.

http://www.overstock.com/Electronics/Ba ... cid=123620

[spazsinbad]

Yeah seriously. I don't live where the corner store or shopping centre is close at hand but that is a good suggestion for earlier thanks - I was not aware of such an innovaton. I actually enjoy no sound but sometimes of course it is useful to hear de woids of wisdom. I know I have said this before but a new computer is in the works and will be here by end of month it is hoped.

[johnwill]

'

And still my point is 'anything but "damper"'. It is just WRONG.

I really don't care what the device is called, but the fact remains in an engineering and math sense, it is not just a damper, but a spring/damper. Spring/dampers are among the most common mechanical devices around, with at least four of them on most cars. A common door closer is another spring/damper.

In the tail hook application, the purpose is to keep the hook point on the deck as much as possible until the wire is snagged by the hook. In the discussion so far, it seems most people think the damper function is to hold the hook down, but that is not the case. A damper provides a retarding force or moment in proportion to the velocity of the object to which it is attached (the hook shank in this case). So if the hook stays on the deck, the shank rotational velocity is zero, so the damper does nothing. If the hook bounces up off the deck, it has a velocity, so the damper retards that motion but does not push the hook back to the deck. That is the function of the spring. The spring may me pneumatic, hydraulic, or mechanical. The damper works by forcing a fluid through an orifice. It may be single acting or double acting. In the tail hook application, it is single acting. That is, it retards upward motion of the hook but not downward motion.

So the spring holds the hook down and the damper reduces the amount of bounce displacement and time off the deck.

I don't much care for the term "damper" myself in this application. In all of the arrestment tests I've worked (F-111B, F-16, T-50) we usually called it the "hold down". Seems less pretentious.

[spazsinbad]

Now 40 years old, here is the NATOPS description of the A-4E/F/G arrestor hook with hydraulic diagram. Other old Navy aircraft hook descriptions could be added (RF-4) and newer such as Hornet, Goshawk hook descriptions available online in PDF NATOPS (details on other threads).

[Gums]

Salute!

Great point John-boy!!!

Sounds like "shock absorbers" for auto/truck/jeep. Without them, and with only the "spring" implementation, most autos would be in for a wild ride.

In this case, it seems that most of the dampening should be versus the "upward" movement of the hook arm and not so much for the down force. Am I getting that right?

Gums sends...