F-35C Lands at Lakehurst For Testing

[spazsinbad]

'zerion' posted a link to the WHOLE story here recently whilst I'll post the pic and text relevant to the F-35C hook testin' here if that is OK?

Looks like F-35C HOOK testing is underway. Yay! Break De Fence Y'all.

Breaking Defence 29 May 2014

"The F-35C passed landing at max sink speed of 21.4 feet per second [1,284 feet per minute] to test landing gear, airframe arrestment system"

Source: https://twitter.com/BreakingDefense/sta ... 89/photo/1

F-35 Achieves Three Major Flight Test Milestones On Same Day 29 May 2014

“...The F-35C, designed for aircraft carrier operations, completed a landing at its maximum sink speed to test the aircraft’s landing gear, airframe and arrestment system at Naval Air Station Patuxent River, Maryland. “Five sorties were conducted, building up the maximum sink rate test condition of 21.4 feet per second, which represents the maximum sink speed planned for this test,” McFarlan said. During the tests, the F-35C did three arrestments, several touch and goes and one bolter. The landings were to demonstrate structural readiness for arrested landings on an aircraft carrier at sea.

Fleet-wide, the F-35 has, to date, amassed more than 17,000 flight hours, with all three variant aircraft at the F-35 Integrated Training Center at Eglin AFB, Florida, surpassing the 5,000 sorties milestone this week....”

Source: http://www.lockheedmartin.com/us/news/p ... e-day.html

STRIKE TEST NEWS Air Test and Evaluation Squadron 23 Newsletter 2011 Issue

"...“Shake, Rattle and Roll” testing... Arrested landings include high sink rates up to 20 feet per second (which translates to 1,200 feet per minute or about a 5° flight path angle)...”

Source: http://www.navair.navy.mil/nawcad/index ... oad&id=769

[spazsinbad]

Not a whisper about any arrest hook issues (perhaps it is all being covered up according to 'lookylookylooky'?).

Navy Joint Strike Fighter Set for October Tests at Sea
03 Jun 2014 Dave Majumdar

The Lockheed Martin F-35C carrier-based version of the Joint Strike Fighter is making steady progress towards sea-trials onboard USS Nimitz (CVN-68) in October according to a company official.

“We are working very hard to get the airplane ready for sea trials, DT-1 sea trials, starting in mid-October,” Eric Van Camp, Lockheed’s domestic F-35 business development director, told USNI News on May 30. “The at-sea period I believe extends from roughly the 12th of October to the third of November.”

However, there are still many tasks that the F-35 integrated test force must complete before the C-model jet can make its first carrier launches and arrested recoveries onboard Nimitz.

One of the biggest remaining hurdles is a structural survey of the jet’s landing gear and airframe. “When we say structural survey it sounds like what we’re doing is parking it some place and doing some inspections, but actually what we are doing is we doing a specific set of flight test points that are designed to understand how the airplane reacts both aerodynamically and structurally when we put it in off-nominal conditions,” Van Camp said.

[...]

Source: http://news.usni.org/2014/06/03/navy-jo ... -tests-sea

[lookieloo]

Not a whisper about any arrest hook issues (perhaps it is all being covered up according to 'lookylookylooky'?).

October then... good enough for me.

[spazsinbad]

I thot that would wake youse up!

The full kids refrain is "Looky Looky Looky - Here Comes Chooky" (Hen/Rooster/Chicken)

AND SOMEONE KEEPS MESSING WITH THE FORMATTING. HOW ABOUT POSTING GUIDELINES ON HOW TO DO IT AND LEAVE IT AT THAT STANDARD RATHER THAN CHANGING STANDARDS WILLY NILLY BECAUSE I HAVE HAD ENOUGH!

[spazsinbad]

For some perspective on how often USN carrier aircraft are tested these days - here is the chart.

F/A-18E/F Catapult Minimum End Airspeed Testing
Briefing presented December 1996.

Frequency Trend of Sea Trial Testing
Source: Tribino, Michael. “F/A-18E/F Initial Sea Trials Briefing.” Patuxent River, Maryland:

Source: http://trace.tennessee.edu/cgi/viewcont ... k_gradthes (PDF 3.6Mb)

[spazsinbad]

Lockheed Outlines Small Surface Combatant Option
10 Jun 2014 OTTO KREISHER, Special Correspondent

"...At Lockheed’s annual media day,...

...Starting the briefings for defense reporters at Lockheed’s Crystal City offices, chairman [LM] Marillyn A. Hewson ...

...She said the F-35C carrier variant being built for the Navy successfully completed shore-based testing for arrested landings and catapult launches and will be tested on a carrier in October.

The 2B software program that is the minimum needed for the Marines to declare initial operational capability (IOC) of the short-takeoff, vertical-landing F-35B version in 2015 is “tracking to be complete by year end,” she said.

The 3i software that the Air Force needs for IOC of its F-35A model started flight test two weeks ago, Hewson said...."

Source: http://www.seapowermagazine.org/stories ... 10-LM.html

[spazsinbad]

This post was started here earlier today also: viewtopic.php?f=61&t=25636&p=273276#p273276

Navy Prepares F-35C for Carrier Landing
13 Jun 2014 Kris Osborn

"...shore landings, taking place at Naval Air Station Patuxent River, Md., are designed to replicate the range of conditions which the F-35C is likely to encounter at sea – to the extent that is possible.

Test pilots are working on what they call a structural survey, an effort to assess the F-35C’s ability to land in a wide range of scenarios such as nose down, tail down or max engaging speed, said Lt. Cmdr. Michael Burks, or “Sniff,” a Navy test pilot.

Max engaging speed involves landing the aircraft heavy and fast to determine if it is the aircraft or the arresting gear that gets damaged, Burks explained.

“The whole purpose is to make sure the landing gear and the aircraft structure are all suitable to take the stresses that the pilot could see while trying to land aboard the deck of an aircraft carrier,” Burks explained.

While recognizing that the mix of conditions at sea on board a carrier cannot be replicated on land, Burks said the test landings seek to simulate what he called unusual attitudes such as instances where the aircraft is rolling with one side up or descending faster than normal with what’s called a “high sink” rate.

“We’ve done about 90 carrier-style landings,” said F-35 Test Pilot Lt. Cmdr. Tony Wilson, or “Brick.”

High sink rate is reached when an aircraft is descending 21-feet per second, much faster than the typical 10-feet per second descend rate, Burks explained....

...“On an aircraft carrier, the landing area is off about 10-degrees. The boat’s motion itself is moving away from you — so you can’t just aim at the boat,” Burks said....

...The aircraft also needs to be able to withstand what’s called a “free flight,” [I would call it an 'inflight engagement'] a situation where the pilot receives a late wave off to keep flying after the hook on the airplane has already connected with the wire, he explained.

“We need to be sure that the engine and the aircraft itself can handle the stress of essentially being ripped out of the air by the interaction between the cable and the hook,” Burks added...."

Source: http://www.dodbuzz.com/2014/06/13/navy- ... r-landing/

Then there is the actual (likely) inflight arrest which damaged the MiG-29K described below. (In flights are not common in USN these days I'll guess and likely the aircraft can take the stress albeit they will need to be thoroughly checked afterwards for any damage.)

Safety scare on Gorshkov
05 Jun 2014 SUJAN DUTTA

"New Delhi, June 4: A new fighter jet of the Indian Navy was partly damaged after a “hard landing” on the deck of the INS Vikramaditya today,...

...…Navy sources described today’s incident as a “hard landing” to distinguish it from a crash. The nose wheel of the jet, a MiG29K — also procured from Russia like the Vikramaditya — is said to have been partly damaged. The MiG29K has tandem cockpits. Both pilots are safe, navy sources said....

...Apparently, the shock of the trap and the landing was so much that the nose of the aircraft pointed skywards before the plane dropped down on its nose wheel. [probably a description of an inflight arrest] The impact damaged the nose wheel....

Source: http://www.telegraphindia.com/1140605/j ... 5E_P5B-8kI

[spazsinbad]

Just gathering some quotes here for 'johnwill' or anyone knowledgeable to comment upon. Particularly please explain the difference between maximum design value of 26.4 feet per second and the 20-21 feet per second sink rate that the Navy Test pilots use ashore (I'll get their term). I gather no aircraft when flying is tested to the 'max. design value'?

[addition] There are some quotes at the top of this page of this thread about sink rates and such with one replicated: "...maximum sink rate test condition of 21.4 feet per second, which represents the maximum sink speed planned for this test..."

The Joint Strike Fighter: A plane for all reasons
07 Mar 2002 Stephen Mraz | Machine Design

"...FLY NAVY:
Carrier operations account for most of the differences between the Navy and other JSF variants. Carrier landings, for example, are so severe, they're often referred to as "controlled crashes." The JSF, in a low speed approach to a carrier landing, will descend at about 11 fps, and will withstand sink rates up to almost 18 fps. By comparison, the typical sink rate for an Air Force JSF will be about two ft/sec.

To help handle better at low speeds, the aircraft will have larger wing and tail-control surfaces. The increased wingspan also boosts the strike-fighter's range and weapon or fuel load. Even without external fuel tanks, the JSF has almost twice the range of the F/A-18C. Larger leading-edge flaps and wingtips provide the extra wing area, while the wingtips fold so the aircraft takes up less space on the carrier's crowded flight and hangar decks. The Navy's JSF will also have two extra control surfaces — ailerons outboard of the flaperons on the wings — for additional lowspeed control and flying precise glide slopes. The Navy JSF currently flies landing approaches at about 130 to 135 knots, about 25 knots slower than the Air Force version...."

Source: http://machinedesign.com/article/the-jo ... asons-0307

“…The tests were successfully carried out between March and April [2010], and included dropping CG-01 95 inches at 20 feet per second, with an 8.8 deg pitch [near Optimum AoA 12.3], two degree roll, and 133 knot wheel speed, simulating a carrier-deck landing.…”

Source: http://www.key.aero/view_feature.asp?ID ... n=military [does not work at moment]

LM F-35 Navy Jet Confirms Carrier-Landing Strength Predictions
23 June 2010

“2010, June 23 -- A Lockheed Martin F-35C Lightning II carrier variant successfully completed testing in which it was dropped from heights of more than 11 feet during a series of simulated aircraft-carrier landings. The tests validated predictions and will help confirm the F-35C's structural integrity for carrier operations.

The jet, a ground-test article known as CG-1, underwent drop testing at Vought Aircraft Industries in Grand Prairie, Texas. No load exceedances or structural issues were found at any of the drop conditions, and all drops were conducted at the maximum carrier landing weight. The drop conditions included sink rates, or rates of descent, up to the maximum design value of 26.4 feet per second, as well as various angles and weight distributions. The tests were used to mimic the wide range of landing conditions expected in the fleet. "The completion of the drop tests is an important step in clearing the way for field carrier landing testing and shipboard testing at high sink rates – a necessary feature for a carrier-suitable strike fighter," said Larry Lawson, Lockheed Martin executive vice president and F-35 program general manager. "This testing also validates the design tools & analysis used in building a structurally sound, carrier-suitable fighter."....”

Source: http://www.prnewswire.com/news-releases ... 83089.html

[johnwill]

Spazsinbad, I'll be glad to comment on your sink rate topic. I just finished commenting on the same topic on dodbuzz.

(http://www.dodbuzz.com/2014/06/13/navy- ... r-landing/)

This statement from prnewswire 23 June, 2010 "The drop conditions included sink rates, or rates of descent, up to the maximum design value of 26.4 feet per second" is incorrect. The maximum design sink rate is 21.4 fps.

Airplane structural certification almost always involves a lab test, followed by flight test. The lab test conditions usually apply 150% of the largest loads expected in service usage. Flight test requires demonstration at 100% of the largest loads expected in service usage. In the case of carrier airplanes, flight test is conducted on land first, followed by carrier landings, up to 100% limit conditions.

The 26.4fps sink rate test was a lab drop test, designed to provide assurance the airplane could withstand 150% of design load for high sink rate conditions. The sink rate limit of 21.4fps will result in 100% of design load on service airplanes.

Why was 26.4 fps chosen for the lab test? Because gear loads at high sink rate landings are roughly proportional to sink rate squared. (26.4 /21.4) ^2 = 1.52 very close to the ratio of 150% to 100% gear load.

[spazsinbad]

Many thanks 'johnwill' I'll have to go and look at your other post now. TAH.

I luv it!

'John': "You are completely in error. The Navy supplied an incorrect dynamic model of the arrestment wire for LM to design the F-35C hook installation. Using the correct wire model, LM has redesigned the hook point and damping force, and guess what? The hook works fine now, even at only 7 feet behind the gear. You may apologize at any time."

Source: http://www.dodbuzz.com/2014/06/13/navy- ... r-landing/

[Addition] I see the 'talkwench' does not want to give up with the comments/theory etc. - maybe the wingnuts need tightening - and the skyhook re-arranged?

[smsgtmac]

Spazsinbad, I'll be glad to comment on your sink rate topic. I just finished commenting on the same topic on dodbuzz.

(http://www.dodbuzz.com/2014/06/13/navy- ... r-landing/)

This statement from prnewswire 23 June, 2010 "The drop conditions included sink rates, or rates of descent, up to the maximum design value of 26.4 feet per second" is incorrect. The maximum design sink rate is 21.4 fps.

Airplane structural certification almost always involves a lab test, followed by flight test. The lab test conditions usually apply 150% of the largest loads expected in service usage. Flight test requires demonstration at 100% of the largest loads expected in service usage. In the case of carrier airplanes, flight test is conducted on land first, followed by carrier landings, up to 100% limit conditions.

The 26.4fps sink rate test was a lab drop test, designed to provide assurance the airplane could withstand 150% of design load for high sink rate conditions. The sink rate limit of 21.4fps will result in 100% of design load on service airplanes.

Why was 26.4 fps chosen for the lab test? Because gear loads at high sink rate landings are roughly proportional to sink rate squared. (26.4 /21.4) ^2 = 1.52 very close to the ratio of 150% to 100% gear load.

I gave you 'up' votes before I even knew it was you -- for all the good it will do in that crowd. If they don't make the connection that it's 'you', you might escape ELP's 'minions' responding to a call to arms. I'm probably minus 30-40 points by now on an A-10 post earlier in the week. Good Luck!

[count_to_10]

I wonder: does the short distance between the F-35 main gear and hook relative to older aircraft (particularly the F-14) have anything to do with stability? The older designs were aerodynamically stable, so the center of gravity (and thus the main gear) would be relatively farther forward.

[johnwill]

I wonder: does the short distance between the F-35 main gear and hook relative to older aircraft (particularly the F-14) have anything to do with stability? The older designs were aerodynamically stable, so the center of gravity (and thus the main gear) would be relatively farther forward.

You might think stability would be enhanced with the hook farther aft, but that is not always the case. It is true that the airplane will tend to go straight ahead, but only if the hook is straight behind the airplane. However, if the hook is displaced laterally, the side load component will tend to turn the airplane sideways. If the hook is far aft, it will have a longer moment arm to the CG, thus turning the airplane. How does the hook get displaced laterally? An off-center engagement will pull the hook sideways and apply a side load to the aft fuselage hook attachment.

Turning the airplane sideways is a bad deal for all concerned, as it may turn over or depart the landing area.

[spazsinbad]

The carrier pilot must approach within acceptable limits for the aircraft and arrestor gear when known (I guess we do not know the absolute limits for the F-35C from this LSO / Operational viewpoint). This is what is becoming known via the testing at PaxRiver. The 'aircraft recovery bulletin' will be published and refined after further ship testing. The LSO will wave off an aircraft that is not within prescribed limits by the time it gets to the wave off window some distance from the ship.

Aircraft approach (or did in my day with perhaps less stringent limits from what I have read in the Hornet/Super era) on the angle deck centreline without any yaw at all. Because, as mentioned probably a few times in this thread and in the long recent article above, the angle deck is moving from left to right during the approach (when the aircraft is on centreline lined up with the angle deck). The carrier is moving straight ahead making the natural wind, from the WOD Wind Over Deck, down the angle deck centreline as best it can (depending on other factors - often there is a slight crosswind because of operational reasons or other issues). The LSO will inform the pilot of the WOD and such during the approach. Anyway the pilot will have to nip the right wing down and back up several times to recover/maintain the angle deck centreline.

I have read how with the HUD a pilot may 'crab' / yaw a little to maintain centreline (whilst it is moving from left to right) but must cease that method by the time he gets to the wave off window or before so as to be within the prescribed limits for yaw (nose off the angle deck centreline when crossing the ramp to catch a wire) and also within the off center touchdown limits. As 'johnwill' described above bad things will happen when the off centre engagement it out of limits. The PaxRiver testing will probably go beyond any ship limits because for one thing the runway is not moving. The ship/carrier moves sometime predictably (for the LSO) whilst the pilot will not grok this much (unless the carrier deck is moving a lot) because he is concentrating on the three things: Meatball Line Up and airspeed (Optimum Angle of Attack).

Over the years there are many photos of offcentre arrests with the aircraft going over the side, often hanging there still connected to the wire whilst the pilot gets out as best he can. Sometimes the aircraft is recovered or just dropped overboard depending on operational factors.

The A-4 was notorious for rolling onto the left wing tip/drop tank during an off centre arrest - often exacerbated by the rolling ship deck and any cross wind. Remember even winds at sea may not necessarily blow in the exact same direction all the time and so on. A wallowing ship is not a pretty sight for a deck lander. The A-4 had a particularly high/long oleo landing gear which exacerbated the roll tendency on touch down. The A4G pilot landing aboard HMAS Melbourne was lucky enough to have only a 5.5 degree angle deck rather than the 9 or 10 degrees angle of recent times in the USN. MELBOURNE had not a lot of 'burble' whilst CVNs have quite a bit which may upset the approach parameters just before reaching the ramp (the wave off window is before this yardstick).

The WALLOW is horrendous during this approach with the A4G going from right to left over the ramp as seen in this video:

[quicksilver]

I'm probably minus 30-40 points by now on an A-10 post earlier in the week...

And you actually care about such a thing?