DT-III aboard USS America

Discuss the F-35 Lightning II
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spazsinbad

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Unread post22 Nov 2016, 04:57

F-35B Weapons Load Testing Wraps Up on USS America
21 Nov 2016 SEAPOWER

"PACIFIC OCEAN — The F-35B Lightning II third developmental test phase (DT-III) aboard amphibious assault ship USS America (LHA 6) reached a new milestone as the program completed weapons load testing Nov. 16.

The Patuxent River Integrated Test Force (ITF) assigned to Air Test and Evaluation Squadron 23 embarked America Oct. 28 with an aggressive test plan featuring a broad array of milestones, which included shipboard launch and recovery expansion test points focused on the evaluation of flying qualities at various aircraft weights, in particular in regard to crosswinds, sink rates, and high sea states. Additionally, the DT-III weapons team evaluated ordnance separation tests and live-fire tests.

“We’re here to augment the existing weight center of gravity effects of the aircraft to expand the fleet envelope wind over deck, and different lateral symmetry and asymmetry configurations,” said Gabriella Spehn, a F-35 weapons engineer from the Patuxent River Integrated Test Team (ITF).

The DT-III weapons team conducted the load tests on land prior to embarking on America. The team tested all of the takeoff and landing worst-case scenarios and endpoints.

“The only way to increase the endpoints is to test on board a ship for sink rates and high sea states, which is the next phase of testing after land-based testing is complete,” Spehn said. “There is no way to recreate the conditions that come with being out to sea.”

Although the tests are conducted to assess the limits of the aircraft, Spehn explained all tests are evaluated and conducted safely.

“We don’t just keep testing until something goes catastrophically wrong,” she said. “Each engineering discipline has to look back at the data we’ve collected after the most recent flight and completion of each test point, and then figure out if we feel comfortable proceeding to the next point.”

The F-35B DT-III pilots purposely conducted test flights under various unfavorable environmental conditions to test the aircraft’s limitations and capabilities.

“As we all know, we can’t choose the battle and the location of the battle, so sometimes we have to go into rough seas with heavy swells, heave, roll, pitch, and crosswinds,” said Royal Air Force Squadron Leader Andy Edgell, an F-35 test pilot embedded at the Patuxent River ITF. “The last couple of days we went and purposely found those nasty conditions and put the jets through those places, and the jet handled fantastically well. So now the external weapons testing should be able to give the fleet a clearance to carry weapons with the rough seas and rough conditions. We know the jet can handle it. A fleet clearance will come — then they can go forth and conduct battle in whatever environment.”

In preparation of DT-III load testing, America’s Weapons Department assembled two types of smart bombs. The team assembled 72 laser-guided GBU-12 and 40 satellite-guided GBU-32s for the first time in the ship’s short history....

[THEN DESCRIPTION ABOUT BOMB BUILDING ONBOARD FOR FIRST TIME]

...With the bombs built by America, the test pilots from Marine Operational Test and Evaluation Squadron One from Edwards Air Force Base, Calif., conducted successful live-weapons tests for two consecutive days by dropping six GBU-12s on a live-weapons range in Yuma, Ariz."

Source: http://seapowermagazine.org/stories/20161121-f35b.html
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Unread post22 Nov 2016, 19:00

spazsinbad wrote:


That is a cool video. At 0:40 in, during a STO you can see the F135 nozzle actively changing thrust vector angle. I was under the (obviously incorrect) assumption that the engine nozzle angle was "set" for either vertical, STO, or cruise. I know the engine nozzle swivels to make small corrections during VL operation, but thought incorrectly that it was "fixed" for STO operation. At that 0:40 mark, it appears to be swiveling a LOT more than anything I've seen in VL operations.
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Unread post22 Nov 2016, 19:08

Somewhere on the forum there are descriptions of what the nozzle is doing during an F-35B flat deck - and particularly a ski jump - STO. There are three modes of STO on a flat deck as I recall - I will have to find that info....

SKI JUMPY: viewtopic.php?f=22&t=20138&p=347365&hilit=Rusnok#p347365

BEST Flat Deck Descripto: viewtopic.php?f=57&t=24438&p=274982&hilit=automated#p274982

SEARCH F-35 forum using this text string: International + Special + Edition + July

2 page PDF description of Flat Deck & Ski Jump STO attached now. + now COMPLETE article of 7 pages attached below also JUMPING JACK FLASH [is a gas]

from PDF mentioned here STO flat deck description:
Jumping Jack Flash
July 2014 unknown author AIR International F-35 Special Edition

"...There are three ways to conduct a short take off (STO) in the F-35B: stick STO, button STO – and auto STO. “That’s a completely automated way to STO the aircraft off the flight deck. You punch in a distance and the aircraft will auto rotate to its optimal fly-out condition. It’s all based on distance: we know where the aircraft is spotted [before it starts its take-off run] and where it should start its actual rotation,” explained Rusnok. “Unlike a Harrier, which launches off the end of the ship flat, the F-35 rotates at about 225 feet from the bow, sits on two wheels until it gets to the end of the ship and actually takes off, a much different process to a Harrier. From a pilot perspective, you lose some sight of the front of the ship; in a Harrier you can see all the deck. But that’s all part of optimising a 35,000lb aeroplane to get off the ship compared to the Harrier, which is only 16,000 to 25,000lb.”

With stick STO the pilot controls the take-off by pulling back on the stick, holding it there and then rotating to the optimal pitch angle to fly off. In button STO, the pilot uses a trim switch which rotates the aircraft when pushed in, activating it when the aircraft passes the yellow STO rotation line positioned 225 feet from the bow of the ship.

“That was a temporary marking applied on the flight deck for this trial and is now being permanently installed on the ship with lighting,” explained Rusnok. “It’s based on optimising the performance of the aircraft and its flying qualities, so we can get the aeroplane off with the maximum amount of nozzle clearance and performance. The STO line is our visual cue to either pull the stick aft or hit the button; or if you’re on automated STO you should start seeing the aeroplane’s flight controls moving by the line, otherwise the pilot can intervene and pull back on the stick. We’ve never had to intervene.” [joker]

The pilot also has command of the throttle. Two power setting options are available for take-off: Mil STO and Max STO [have not read about this before], as Maj Rusnok explained: “When you taxi to the tram line you stay in mode one, the conventional flight mode. You convert the aircraft into mode four, the STOVL flight mode, and it takes about 15 seconds or so for the doors to open up and the lift fan to engage.

“Then you push the throttle about halfway up the throttle slide into a detent position at about 34% engine thrust request. It sits there and you check the engine gauges: if the readings are okay you slam the throttle to either Mil or Max position and then release the brakes simultaneously. Pushing through to max is like an afterburner detent. But it’s not an afterburner – you can’t go to afterburner in mode four.

“It’s a very fast acceleration. The closest we would spot from the bow is 400 feet, so about 175 feet before we would actually start rotating the aeroplane [at the STO rotation line]; so very, very quick.”

One of the big test points for DT I was to ensure adequate nozzle clearance in all the different test conditions. The engine nozzle swings down and back up during the take-off in accordance with inputs from the aircraft control laws.

“It’s all automated,” said Rusnok. “The pilot is not in the loop whatsoever – either they’re pushing the button and letting the aeroplane do its own thing or pulling back on the stick to help it. Monitoring systems cue when something is wrong, so you have to rely on them to keep you safe because the flight controls are being moved unbelievably quickly.”

Maj Rusnok said the take-off was very much like that ashore, with very little sink off the end of the deck. “The aeroplane is ridiculously powerful in STOVL mode. Just raw, unadulterated power.”..."

Source: AIR International F-35 Special Edition July 2014
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F-35B flat deck STO Rusnok Method pp2 + Ski Jump.pdf
(1.4 MiB) Downloaded 305 times
JumpingJackFlashAirInternationalJuly2014pp7.pdf
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Last edited by spazsinbad on 22 Nov 2016, 19:55, edited 5 times in total.
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Unread post22 Nov 2016, 19:22

I noticed that rather noticable movement on the nozzle.... and as a systems consultant I have to say: Modern technology is cool!

(Edit: Or, in this case.... HOT!)
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Unread post22 Nov 2016, 20:04

spazsinbad wrote:
Jumping Jack Flash
July 2014 unknown author AIR International F-35 Special Edition
<snip>

The pilot also has command of the throttle. Two power setting options are available for take-off: Mil STO and Max STO
...

“Then you push the throttle about halfway up the throttle slide into a detent position at about 34% engine thrust request. It sits there and you check the engine gauges: if the readings are okay you slam the throttle to either Mil or Max position and then release the brakes simultaneously. Pushing through to max is like an afterburner detent. But it’s not an afterburner – you can’t go to afterburner in mode four.

<snip>

Source: AIR International F-35 Special Edition July 2014


I read an article in a PDF (found somewhere here on F-16.net) recently where a P&W Product Development Engineer remarked or explained that they run the turbine temperature up while in the dual-cycle STOVL mode. I would not be surprised if Mil STO power is just a max thrust option for the engine, but going to Max STO mode may trigger some engine control doofer to boost the turbine temp(s) to get that little bit of extra thrust. This also makes sense because in the same article (or another one I read at about the same time), P&W engineer or manager remarked that the F135 has been run out to 51,000 lbs of thrust while still meeting all engine requirements, but that they are running at 43,000 lbs to improve durability / engine life cycle costs. So it sounds like they have plenty of margin to temporarily boost power for a STO takeoff without adversely affecting durability / life of engine.

Here is the bit about the F-135 being capable of 51,000lbs in full reheat:
Powering the Lightning II
Chris Kjelgaard, date unknown
(p. 12)

P&W also won’t confirm the dry weight of the F135, but a source commenting on an aviation blog cites Warren Boley, president of Pratt & Whitney Military Engines, as saying the F135 weighs 1,500lb (680kg) more than the F119. This would put the F135’s dry weight at around 5,400lb (2,450kg). However, the F135 may have a higher thrust-to-weight ratio than
the F119 (the F119’s overall pressure ratio is 26:1 compared with the F135’s 28:1) and so the 5,400lb figure might be high. Boley has also suggested the F135 has an uninstalled wet thrust capability of approximately 51,000lb (226.86kN). If this reads across to an installed basis – in which bleed air and shaft horsepower would be extracted to power aircraft systems – it should provide a comfortable operating margin over the 43,000lb (119.27kN) of wet thrust required by the spec.

Source:http://militaryrussia.ru/forum/download/file.php?id=28256
Last edited by steve2267 on 22 Nov 2016, 20:32, edited 2 times in total.
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Unread post22 Nov 2016, 20:07

krorvik wrote:I noticed that rather noticable movement on the nozzle.... and as a systems consultant I have to say: Modern technology is cool!

(Edit: Or, in this case.... HOT!)


....having become rather "numb" to the many technological advances in this program an occasional "Slap in the Face" is still rather startling! The dynamics of that control system on the nozzle is "Shocking", pushing to get the airspeed for flight and then pushing and lifting to maintain the climb rate vs. load is indicating at least a half dozen control algorithms working together to "point" the nozzle for it's many requirements. That hydraulic system has a "huge amount" of work to perform in that short duration, way beyond the more static roles that I had failed to watch (OMG)! Once again I am over whelmed from where my cables and pulleys with electro-hydraulic assist (no computers) from the "olden dayz!" has now evolved.

Thanks for the video and the notice, better late than never! :oops:
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Unread post22 Nov 2016, 21:00

For the technically inclined, an excellent description of the turbine cycle is described by Dr. Paul Bevilaqua, father of the F-35 LiftSystem:
The power produced by the turbine section of a turbojet engine is given by the equation

turbine power = (Mdot) (Cp) (T04) [ 1 - (P5/P4)^((g-1)/g) ] (1)

where Mdot is the mass flow through the turbine, Cp is the specific heat at constant pressure per unit mass of air, g is the gas constant, T04 is the stagnation temperature of the gas entering the turbine section, and P5/P4 is the pressure ratio across the turbine section. The usual method of increasing turbine power is by increasing the fuel flow, which increases T04. The additional power of the turbine accelerates the engine until the power absorbed by the compressor matches the power produced by the turbine and the engine speed stabilizes. Because the rotational speed of the engine has increased, the engine pumps more air and produces more thrust.

The performance map of the turbine section in a typical modern fighter engine is shown in Fig. 5. The locus of steady-state matching conditions defines the engine operating line, which is the diagonal running from the bottom left to the top right in the figure. The engine and compressor are designed so that the turbine power and compressor power match near the point of maximum efficiency at every speed. However, at maximum thrust, the turbine inlet temperature T04 is already at the material limit of the turbine section. As a result, the gas temperature cannot be increased to provide the power to drive the lift fan. Instead, during VTOL operation, the additional power to drive the lift fan is obtained by increasing the pressure drop across the turbine section, P4–P5. The additional power is shown by the two points in Fig. 5.

The lower point is on the conventional operating line, and the upper point is obtained when the pressure drop across the turbine is increased. In this case, nearly 30,000 hp can be extracted before the turbine section reaches its stall limit. There is enough residual power in the exhaust flow to generate significant thrust from the cruise nozzle during hover. Engaging the clutch while increasing the nozzle area transfers the additional power to the lift fan, so that the speed of the engine does not increase.

p.1828 of
Bevilaqua, Paul M. "Genesis of the F-35 Joint Strike Fighter." AIAA Journal of Aicraft, Vol. 46, No.6, November-December 2009. pp. 1825-1836.

Source:
https://www.scribd.com/document/284662003/PaulB-F35
or
http://pdf.aiaa.org/getfile.cfm?urlX=-% ... 0%20%20%0A

Bevilaqua_Figure_5.JPG


If I am understanding what the P&W Engineering Manager stated (whose quote I cannot quite yet find), it sounds like P&W boosts turbine temperature (T04 in above equation), probably by increasing fuel flow, during STOVL operation to get that extra power for the Max STO throttle setting.

Also, I strongly suspect that the reason the exhaust temperature of the F-135 is only 4-500°F, rather than the misquoted 1700°F, in STOVL mode, is that when the LiftFan extracts that 30,000 SHP from the low pressure turbine, the extraction of all that energy reduces the F-135 exhaust temperature to the 4-500°F level. I say "suspect" because my thermodynamics sucks. I would love to hear a propulsion or thermo guy pipe in here and confirm my suspicion.
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Unread post23 Nov 2016, 00:28

Sadly the F-35B has been bashed with that 1,700 degree undefined 'wotisit' quote since 2010. I suspect but cannot prove it is the afterburner exhaust temperature for the A/C variants but why they would do this near ordinary concrete (which quotes that number) instead of for an engine run pad is beyond me. When I took the video lecture up with BillyBobBoySweetiePie on pPrune he said that Bevilaqua was using old figures in the video. AS IF! Here is the designer giving a lecture to his peers and 'fooling' them with 'old' figures. PULL THE OTHER ONE! Anyway it is obvious from countless VL videos now onboard that the deck crew remain about the same distance from the B model as the Hairier.

And yes there is a quote that the LiftFan sucking energy makes the exhaust cooler by about 300 degrees. Would anyone be surprised this stuff is scattered all over the F-35 forum and a lot of it is in the PDFs attached in this thread & elsewhere.
JOINT STRIKE FIGHTER Boeing X-32 - Lockheed Martin X-35
23 April 2001 Geoffrey Buescher

“...Lockheed Martin STOVL Lift Fan System
...Lift fan has two stages, pressure ratio of 2. Uses 27,000 – 28,000 hp from 70,000 – 80,000 produced by turbine.

• Using lift fan instead of hot flow reduces flow velocity by 30%, lowers [hot exhaust] temperature by 250 deg F; lift fan produces about 18,000 lb thrust. [approx. 600 - 250 = 350 deg F exhaust LiftFan as has been quoted about 300]

• Lift fan adds 4,000 lb to airframe, but lifting capacity of STOVL is increased by much more — claims of 60% above direct thrust approach. For CTOL and CV versions, extra space otherwise used for lift fan is used for fuel & avionics.

• Cold [350 deg F approx.] flow from lift fan protects inlet from hot gas ingestion...”

Source: http://www.dept.aoe.vt.edu/~mason/Mason ... escher.pdf (0.7Mb)

Shipshape Amphibious ship upgrades vital to JSF and MV-22 deployments
13 OCT 2014 Michael Fahey; AVIATION WEEK & SPACE TECHNOLOGY; DEFENSE TECHNOLOGY INTERNATIONAL

"...The F-35B creates 10-20 sec. of thermal input - 400-500F exhaust - during landings, Navy documents show..."

Source: OCTOBER 13, 2014 AVIATION WEEK & SPACE TECHNOLOGY







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Unread post23 Nov 2016, 01:06

spazsinbad wrote:Sadly the F-35B has been bashed with that 1,700 degree undefined 'wotisit' quote since 2010. I suspect but cannot prove it is the afterburner exhaust temperature for the A/C variants.


Unless that's °C I'd be surprised if it was that low. The F110-129 is around 2000°F with the F100-229 being 3200°F. Seems unlikely that the F135 would have cooler exhaust than the -229. (See attached doc. pages 49 & 51).
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Unread post23 Nov 2016, 01:28

As I said I'm only guessing - perhaps that 1,700 is for full power no afterburner? I really don't care because I'm only concerned with the STOVL functions and there are quotes about temperatures as noted above.
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Unread post23 Nov 2016, 02:11

sferrin wrote:
spazsinbad wrote:Sadly the F-35B has been bashed with that 1,700 degree undefined 'wotisit' quote since 2010. I suspect but cannot prove it is the afterburner exhaust temperature for the A/C variants.


Unless that's °C I'd be surprised if it was that low. The F110-129 is around 2000°F with the F100-229 being 3200°F. Seems unlikely that the F135 would have cooler exhaust than the -229. (See attached doc. pages 49 & 51).

Not that I have any info on this, but those temperatures seem more appropriate for the combustion chamber. 3200 F in particular is enough to melt steel and nickle.
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Unread post23 Nov 2016, 05:47

count_to_10 wrote:
sferrin wrote:
spazsinbad wrote:Sadly the F-35B has been bashed with that 1,700 degree undefined 'wotisit' quote since 2010. I suspect but cannot prove it is the afterburner exhaust temperature for the A/C variants.


Unless that's °C I'd be surprised if it was that low. The F110-129 is around 2000°F with the F100-229 being 3200°F. Seems unlikely that the F135 would have cooler exhaust than the -229. (See attached doc. pages 49 & 51).

Not that I have any info on this, but those temperatures seem more appropriate for the combustion chamber. 3200 F in particular is enough to melt steel and nickle.


Go read the attachment. (Just for reference, the Shuttle SSME exhaust temp is over 6,000 degrees. That should give you enough of a hint.)
Last edited by sferrin on 23 Nov 2016, 11:55, edited 1 time in total.
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Unread post23 Nov 2016, 07:20

sferrin wrote:Go read the attachment.

So I skimmed through the attachment, not quite sure for what I was looking... when on the 27th page I found depicted temperatures in the jet plume behind an F-15. Of particular interest is that at full military power the temperature of the jet exhaust (F-100-PW-229 ?) is 800°F.

Since we know that the F-135 is NOT in reheat in STOVL mode, and several references note a 250-350°F reduction in temperature from the extraction of power by the low pressure turbine to run the liftfan, and if we assume the exhaust temperature of the F-135 is on the order of the F-15's F-100 engine, then

800° - 300° = 500°F.

And 500°F +/- is exactly what is depicted in the first video to which spaz linked above:



To me, this first order analysis confirms that the exhaust temperature of the F-135 during STOVL operations is on the order of 500-600°F and not anywhere near 1700°F.
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Unread post23 Nov 2016, 11:54

steve2267 wrote:
sferrin wrote:Go read the attachment.

So I skimmed through the attachment, not quite sure for what I was looking...


Well in the case I was commenting on you'd be looking for exhaust temps. on the pages I mentioned. They'd show the figures I gave. And since it was in response to a comment regarding full afterburner temps were talking apples and oranges.
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Unread post23 Nov 2016, 12:19

Becuz we do not have an F-35B/C NATOPS weez will have to made do with an A4G tiedown graphic from NATOPS instead.
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