Patuxent River Ski Jump Video (No F-35Bs on it)

[geogen]

Would like to see a test-launch of an (USMC) A-29 off a Jump... call it a day.

[spazsinbad]

This old URL has a lot more of the text from a complicated 'Optimise Ski Jump for F-35B' PDF that is no longer at URL mentioned: viewtopic.php?f=22&t=12631&p=178786&hilit=Revill#p178786

This year old 18Mb PDF has a lot of current/historic Ski Jump info and it will be updated once the various related F-35B on the ski jump news items/articles are online. This OneDrive PDF has the PDF cited below: https://onedrive.live.com/?id=CBCD63D63 ... E6&group=0

CVF ski-jump ramp profile optimisation for F-35B
Feb 2009 A. Fry, R. Cook and N. Revill, THE AERONAUTICAL JOURNAL FEBRUARY 2009 VOLUME 113 NO 1140

"...2.2 Principles of the ski jump
The ski jump ramp works by imparting an upward vertical velocity and ballistic profile to the aircraft, providing additional time to accelerate to flying speed whilst ensuring it is on a safe trajectory. This additional time is manifested either in a reduced take-off length for a given weight, or increased weight (i.e. launch performance) for a fixed take-off distance as in a ship based STO.

The additional performance does not come for free, with a significant increase in landing gear loads above those of a standard take off (which are very low compared to a landing). The increase represents the energy transferred to the aircraft as it translates up the ramp; and if the angle and curvature of the ramp are increased to obtain greater performance benefit, so are the loads. This is tolerable up to a point because the gear strength is defined by landing events and thus has the ability to accept the increased take-off loads, but loads act as an upper boundary on permissible ramp size, as illustrated in Fig. 5.

The ideal landing gear vertical load time history for a ski jump ramp STO is sketched in Fig. 6, with a rapid increase to a steady maximum where the area underneath the curve represents the energy imparted by the ramp. However, the actual loads are different, and reflect the complex dynamic response of the gear components as they enter and travel up the curvature of the profile.

References 1, 2 and 3 describe in further detail the principles behind the ski jump and its advantages as part of a STO manoeuvre compared to a flat deck launch and the design of the profile is described later.

It should be noted that non-STOVL aircraft can benefit from a ski jump manoeuvre, as illustrated by the Russian use of ramps with conventional type aircraft from their carriers. STOVL aircraft are unique however because of the flexible and complex manner in which the thrust and control effectors generate combinations of thrust and forward speed in conjunction with the speed dependent wing lift...."

...4.2 Safe launch metric
At the core of a ski jump performance analysis is the assessment of whether a launch case is achievable or not. The minimum safe launch is defined where the ramp exit speed does not result in any rate of descent during the trajectory until the aircraft has transitioned to fully wing-borne flight. This results in the launch profile shown in Fig. 8, with an inflection point at which the criteria for a successful launch are assessed.

There are two safe launch criteria derived from legacy STOVL experience that are used on the JSF program, of which the more stressing is adopted: (a) subtracting a margin from the WOD and requiring zero sink rate (known as Operational WOD); and (b) using the full value of WOD but requiring a defined positive rate of climb. Both also require a threshold forward acceleration...."

Source: http://www.raes.org.uk/pdfs/3324_COLOUR.pdf

[spazsinbad]

An historical aside perhaps but maybe relevant to question 'why test' on land before 'test at sea' (another forum another time)

Costing Complex Products, Operations & Support
19 Oct 2011 Dr. Michael Pryce

“...Operations on the Harrier have led to constant discoveries of undercarriage O&S issues that needed to be addressed. Although the main undercarriage was very robust, being designed to operate off base and to take many unusual loads, such as landing while flying backwards, these discoveries were near impossible to predict and meant that the real-world experience of the undercarriage in use differed from the original design spectrum that they were built to meet.

For example, as Burton (1996) reports, seemingly minor differences in the build quality of the ski-jump ramps of the UK’s Invincible Class light aircraft carriers seriously affected the life of the undercarriage units, depending on which ship was being operated from. These ship build quality differences were not part of the original design assumptions, or subsequent modeling undertaken for a new ski-jump design fitted to UK aircraft carriers and its effect on the aircraft’s operating limits, and led to unexpected, and unexplained, cracking in the undercarriage units.

Upon investigation, down to individual aircraft and mission levels, it was discovered that the undercarriage damage suffered was not particular to the role or mission profile of the aircraft, or to the type of Harrier, but to the particular ship of a class that they were operating from. The damage was expensive to repair, but absolutely necessary in order to avoid a catastrophic failure mode that could not be predicted. Such a failure would lead to loss of an aircraft and likely serious damage to the ship. However, it was avoidable. The issues of the variability of carrier deck design on the class of ships concerned were known to the aircraft design team at least a decade before, with pitting and so forth causing problems on both deck and in the hangar (Brooklands Museum, 1985). However, in the calculation of undercarriage loads carried out during the design of the Sea Harrier, a smooth deck was assumed, based on design rules created by the UK Ministry of Defence (National Archives, 1978)....

...The fact that one of these ships caused damage to aircraft undercarriage units was not catastrophic in this case but, in large part, this was due to the undercarriage being of robust design, thanks to very different original requirements. If the undercarriage had been designed by the assumed loads for the ski-jump, modeled as part of the design and clearance program, it could well have failed in service use, leading to expensive re-design, remanufacture, and modification work for the entire fleet, or to the aircraft carriers. If the simple, baseline assumptions of the nature of ski-jump ramp design had been widened to look at possible worst case scenarios, the issue may have been accounted for earlier, and its costs would not have come as a surprise....”

Source: http://www.dtic.mil/dtic/tr/fulltext/u2/a555661.pdf (200Kb)

[spazsinbad]

What redesign of Harrier / SHAR gear may have entailed: http://www.flightglobal.com/pdfarchive/ ... 02666.html

[simon257]

The Test Ramp was built in the UK, and shipped across the Pond a few years ago:

http://www.wfel.com/news/wfel-set-to-so ... ican-deal/

[spazsinbad]

Thanks 'simon257' "somebody is wrong about this on the internet" about this has bugged since for a long time and info about the CVF EXACT REPLICA built in May 2009 on the PaxRiver Centrefield (after whatever was there before demolished I guess) is on this forum but SADLY information became scattered when this forum was divided into various sections (rather than being one AND people like me starting new threads - why? - who knows. Anyway searching on ['WEFL' but did not find anything?] should get some stuff with other search words as well as 'EAF' and anyway I'll find the clues eh.

Meanwhile attached is a PDF at maximum file size that has most of the info about Ski Jumpiness that has been collected & MOST of this stuff appears in this F-35 forum somewhere - finding it again & again has become a chore now.

Another version of this UPdated Ski Jump PDF will be online in a few weeks with more up to date info about recent tests.

[UPDATED now 151 page PDF below but it does lack new details likely to be published in a week or so about ski jumpin'.]

[spazsinbad]

OF course I'm interested in ski jumps - maybe less now that 'apparently' the Bs on LHDs are not in the near future for Oz - but never give up the ship gents. Meanwhile I had gone to pPrune to see what they had to say about the SKI JUMP but they were slow to start and then I only got back there today to replicate some good posts from the knowledgeable as seen below: [The posts that interest me the most start on Page 317 and finish on Page 318 - there may be more later - dunno]

http://www.pprune.org/military-aviation ... t-317.html

'John Farley' 23 Jun 2015: http://www.pprune.org/military-aviation ... ost9021527
"Re ski-jumps, it does not take much thought to realise that the ramp delivers any aircraft into free air in a nose up attitude and climbing. This saves the pilot having to arrange all of this when departing from the flat. Indeed back in 1977 when the boffins thought I was exaggerating how easy a jump was compared to a flat takeoff, I gave them the next record with a straight line on the tailplane and aileron traces for 35 secs after crossing the end. At the debrief they showed me the traces and apologised for the instrumentation drop out on the tailplane and aileron channels. I said “It was not a drop out I was not touching the stick - can you have a lower workload than doing nothing?” ....
&
Incidentally, if you look at any video of a B flat deck takeoff and watch the tailplane activity crossing the end and compare that with the tailplane activity off the ski-jump you will notice that even modern flight control systems find life easier from a ramp."
&
'ENGINES' 23 Jun 2015: http://www.pprune.org/military-aviation ... ost9021824
"Perhaps I can help out a bit here. What I can't do is improve on JF's succinct and 'spot on' comments about ski jump takeoffs. They are, by some distance, the lowest workload way of getting a combat jet into the air. The flat STO presented many more challenges to the F-35B team, and the lack of aft control surface movement shows how straightforward the evolution is.

However, it's a lot more than 'straightforward'. It's a little surprising, given that this is a pilots' forum, how few people mention the significant advantages it delivers. Firstly, operational: the ski jump will allow the F-35B to launch on task with at least another ton and a half of fuel and/or weapons. That's a ton (or two) of pure military goodness. Secondly, safety. As JF points out, the aircraft leaves the jump nose up and climbing without the pilot having to do anything. If anything does go wrong, the pilot has many more precious seconds to dump stores/jump out. At night, or in bad weather, or from a pitching deck, that's also a lot of goodness.

I do understand why some posters think this looks like a 'pucker' heavy evolution, but it's really, honestly, not. Every Harrier pilot I worked with said that it was a complete non-event. What's really amazing is that these gains come without penalty to the aircraft, which is fairly rare. The Harrier needed no mods to do ski jumps, save extra servicing checks on the nose leg. The F-35B has needed none. The flat deck STO drove the design, the ski jump came basically free.

Oh, and don't forget that it's another brilliantly simple and effective naval aviation idea from the UK's Fleet Air Arm. Respect.

JTO: Yes, the aft nozzle is definitely moving. I am not familiar these days with the F-35B control laws. but I would guess that what is happening here is that the aft nozzle is being left as far 'up' as possible to get to ramp exit speed in the shortest time (and distance), then programmed 'down' after ramp exit to support the 'fly away' profile. The Harrier did this manually, with the pilot selecting nozzles down to an adjustable 'STO stop' as it neared the ramp exit. F-35B does this for him/her.

For those that might not be familiar with the way a ski jump STO works, the key thing to 'get' is that the aircraft leaves the ramp BELOW flying speed. So the rate of climb starts to decay after ramp exit, depending on how much wing lift and jet lift is being provided. However, the aircraft is still climbing. As it accelerates, wing lift increases and jet lift can be reduced by altering the angle of the propulsion system's nozzles. At some point after ramp exit, the aircraft reaches an 'inflexion point', and the rate of climb starts to increase again. That distance between the end of the ramp and the 'inflexion point' is essentially a 'free runway in the sky' - around 1 to 1.5 km, depending on launch weight, temperature and other factors. That 'free runway' delivers the payload improvement.

The UK legacy performance limit for Harrier ski jump STOs was a minimum ROC of 400 feet per minute at the 'inflexion point'. Other nations have different limits.

A powered lift aircraft can 'schedule' (adjust) wing and jet lift so as to maximise the payload that can be delivered from the ramp. It can also be controlled well below wing borne flying speeds. Unfortunately, conventional aircraft can't do either of these. They have to launch at a speed at which they can fly controllably on wing lift alone. Their only option (with all thrust already applied) to arrest ROC decay is to apply more pitch, which increases drag, which slows the aircraft, which.....you probably get the picture. That's why the STOBAR option, being used by the Chinese and others, is, in my view, always going to be severely limited in effective payload...."

PITCH RATE QUESTION IS ANSWERED on next page 318: http://www.pprune.org/military-aviation ... t-318.html

[spazsinbad]

NITKA had me baffled for a long time - where was it on a map? NITKA is an acronym but long story short RuskieNewbies get to JumpSKI for the first time eh - in that Ukraine - is that Russia now?

Northern Fleet Su-33’s Redeployed to Crimea for Training
13 Jul 2015 SPUTNIK

“Three Su-25UTG aircraft and three Su-33 carrier-based fighters were redeployed from the Severomorsk-3 airfield of the Northern Fleet to the Saki airfield. The training sessions will take several weeks and include 10 flying shifts.

Crews of the shipborne fighter regiment of the Russian Northern Fleet aviation began on Monday practical training at the NITKA range in Crimea, the press-office of the fleet reported.

"Three Su-25UTG military training aircraft and three Su-33 carrier-based fighters were redeployed from the Severomorsk-3 airfield of the Northern Fleet to the Saki airfield. The aircraft will be involved in training flights. In addition, 70 servicemen of the flying and technical personnel of the shipborne fighter regiment of the Northern Fleet arrived in Crimea. Among them are five young pilots who have no experience in carrier take-off and landing," the report read.

The training sessions will take several weeks and include 10 flying shifts.

After the practice is completed the pilots will return to their deployment site. They will begin preparation for flights to the Admiral Kuznetsov aircraft carrier.

The NITKA range is a special aviation training facility which imitates the deck of an aircraft carrier. It is used for practicing carrier take-off and landing.”

Source: http://sputniknews.com/military/2015071 ... 56601.html

Nazyemniy Ispitateiniy Treynirovochniy Kompleks Aviatsii

"Novofedorivka
...It is located about 3 kilometres (1.9 mi) south of the regional centre of Saky, and about 70 kilometres (43 mi) north of Sevastopol. Formerly a base of Soviet Naval Aviation as "Saky-4", it came under the Ukrainian Navy control with the breakup of the Soviet Union. It was captured by Russian forces without resistance on March 22, 2014...."
https://en.wikipedia.org/wiki/Novofedorivka

[spazsinbad]

[Corsair1963]

https://youtu.be/dB73FdERNBA

[Corsair1963]

https://youtu.be/ZMcqV_Pjorc

[XanderCrews]

Would like to see a test-launch of an (USMC) A-29 off a Jump... call it a day.

No thanks, we're fine

[spazsinbad]

Some SkiJUMPy pics here (a bit late) : https://www.flickr.com/photos/lockheedmartin/

[spazsinbad]

Salty Dogs & Funky Jets
October 2015 Mark Ayton

"...Ski Jump Trials
Her Majesty’s Ship Queen Elizabeth (R08) is fitted with a ski jump like no other: a new design tailored to be used by very expensive new aircraft. Launching a 60,000lb F-35B off a ski jump requires some serious maths, engineering and testing.

The F-35B ski jump test campaign should have started in March of this year, but was delayed due to brutal sub-zero temperatures and snow that blighted Patuxent River at the time. Aircraft BF-01 was originally assigned to conduct the ski jump events but was unable to remain at Pax while the weather improved. It was already scheduled to deploy to Edwards Air Force Base, California to conduct wet runway and crosswind testing.

The test programme comprises two phases, the first of which eventually began on June 19 when BAE Systems test pilot Peter Wilson conducted the first take-off using the ski jump at Pax with F-35B BF-04. Sqn Ldr Edgell told AIR International: “Phase 1 is a risk-reduction phase designed to highlight any significant hardware or software updates that may be required prior to commencing the bulk of testing. It comprises 29 ski-jump launches.

“Phase 1 will ensure our models and predictions are correct. If anything needs addressing we can do so in a timely fashion and then go into the 140-sortie Phase 2.”

The ski jump used on HMS Queen Elizabeth has a curved leading edge designed to simultaneously launch an F-35B upward and forward with a greater take-off weight and less end-speed than required for an unassisted horizontal launch aboard an LHD-class amphibious assault ship, such as USS Wasp (LHD 1).

The reader may be surprised to learn that the ski ramp built at Pax River is based on the type used on the Invincible-class aircraft carriers which is a little bit shorter (50ft) and slightly shallower (0.5º) than the ramp on Queen Elizabeth-class carriers. Sqn Ldr Edgell explained: “The Pax River ramp design process dates back to 2005 but, at the time, the Queen Elizabeth ramp profile was not known. Analysis conducted in 2005 showed we simply needed to use a ramp with a profile that allows us to stay just under the predicted F-35B ultimate loads and the Invincible-class ramp achieved this.”

Pax River’s ramp allows the test team to make adjustments for different profiles and encompass everything below the ultimate loads of the aircraft. “Though the verification of our models during phases 1 and 2 we can tweak the control laws to work off other types of ramp, none of which are the same,” said Sqn Ldr Edgell. When the aircraft comes off the end it is ballistic and accelerates to the fly away air speed, typically 10-20kts higher than launch speed, and therefore reduces ground roll.

“There’s a fine line between ensuring we have suitable gear loads and fly away speed,” explained Sqn Ldr Edgell.

“We want lots of margin on both of those. To achieve margin for gear loads we need to be slow, i.e. start right at the bottom of the ramp. To achieve margin on minimum fly away speed we need to start towards the back of the run-up. We blend the two aspects together and meet in the middle to gain the safest launch spot. For the very first sortie, our spotting distance will be conservative and will launch the jet off the end of the ramp straight into a previously flown flight condition.”

Such regimes have been flown several times during short take-offs at the field and STOVL departures.

Sqn Ldr Edgell explained an interesting fact about the take-off : “You can be lined up three, four, five hundred feet back from the start of the ramp and as you slam the throttle forwards, the jet doesn’t know it’s about to go up the ski jump. It waits for certain triggers to alert it to the fact it’s going off the ski jump, at which point its flight control system moves the horizontal tails and the nozzles into the optimum position. It needs to hit 45 knots going up the ramp.

“The throttle needs to be above 65% ETR, with 6 degrees of attitude and a pitch rate of 6 degrees per second. At that point it moves all of the effectors into the right place. Bear in mind the ski jump at Pax is only 150 feet long, so the aircraft hits all of those parameters with less than 100 feet remaining. By the time it goes off the edge of the ramp all the surfaces and the nozzles are at the optimum position, the aircraft rotates up to the optimum pitch attitude to fly away. It’s pretty clever stuff.”

Sqn Ldr Edgell described the launch process: “You slam the throttle and guard the stick. There is no input on the stick required. As the aircraft moves down the tramline of the deck you track the centre line with your feet, just like any other carrier deck take-off, but there’s no pitch input required. The jet flies away. It’s effortless.” In the event of any kind of malfunction, the pilot takes control and manually flies off the edge of the ramp, which is why he must guard the stick during the roll.

There is no significant part for the pilot to play in the take-off – the result of a design philosophy to minimise the pilot’s workload. A good example is tracking the centreline on a rolling pitching deck at night. That’s a challenge in a Harrier but in the F-35B it’s his only task so he should do a much better job. The administrative burden on the pilot has been significantly reduced: in this situation to an effortless level.

Phase 2 will introduce crosswinds, external stores, asymmetry, minimum performance (minimum deck) launches from the bottom of the ramp, and simulated performance degradation all to increase the aircraft’s flight envelope in Block 3F configuration. That’s imperative work for the UK which will undertake first-in-class flight trials on HMS Queen Elizabeth in the final quarter of 2018...."

Source: Air International Magazine OCTOBER 2015 Vol.89 No.4

[spazsinbad]

A Message from Lorraine Martin
22 Oct 2015 LM

"...Ski Jump testing at Pax River is ongoing, and the team is really doing some amazing work. They completed nine successful takeoffs from the ski jump platform. Throughout the testing they found some challenges to overcome and work, but the team has done a great job of working through those challenges. They have to complete eight more tests to finish up phase one testing. It’s exciting to see images of the F-35B taking off from the ski jump, and I know the U.K. and Italy are also excited about this testing and the capabilities it brings to their countries...."

Source: https://www.f35.com/assets/uploads/docu ... _22_15.pdf (0.3Mb)