The F135 Block Upgrade Plan [SIX PAGE PDF of entire article "Towards Tomorrow's US Fighter Engines" attached below]
Jun 2015 AIRinternational Chris Kjelgaard

"...During its original ground-testing effort for the F135, P&W ran an unimproved engine at thrust levels of up to 51,000lb in uninstalled configuration (ie. without any accessory gearboxes or drives drawing power from the engine). This suggested that, even on an installed basis, the F135 had several thousand pounds of additional thrust available if necessary, if run at high temperatures…."

Source: https://www.scribd.com/doc/269303020/AIR-US-NG

GE Aviation’s future fighter engine TECHNOLOGY XA100 [FOUR PAGE PDF of Article attached below]
April 2019 Chris Kjelgaard

"Completion by GE Aviation of the detailed design process for its adaptive-cycle fan engine signals a switch from technology development to ensuring manufacturing readiness, reports Chris Kjelgaard...

...In completing the detailed design of the XA100, according to Tweedie, the company has moved on to a new phase of development from the primary technology-development effort in which it has been involved for the past 12 years to design and mature a variable-cycle fighter engine based on an adaptive-cycle fan design. Its XA100 design having been approved by the US Air Force, GE has now embarked on the final push to complete Phase 1 of the two-phase AETP programme. This push represents the final maturation of adaptive-cycle fan engine development to the point where an XA100-sized engine can be placed quickly—and with very little technological and design risk—into volume production if required, said Tweedie....

...Along with Pratt & Whitney’s XA101 variable-cycle engine, GE Aviation’s XA100 is one of two adaptive-cycle fan engine designs competing for what may eventually be a decision by the US Air Force to order just one variable-cycle fighter-engine design into production based on the service’s findings from AETP Phase 1. In 2016, the AFLCMC awarded each of the two companies a $1 billion, five-year R&D contract under AETP Phase 1 so the US Air Force could choose a potential winner from the XA100 and XA101 and order it into production during the first half of the 2020s.

As finally became clear publicly in mid-2018, the US Air Force specifically had in mind a potential decision to re-engine the Lockheed F-35 from about 2025 onwards, partly as a result of the known thermal-management challenges the F-35 has today in combination with its existing F135 engine. To that end, the AFLCMC specified that not only must the XA100 and XA101 fit the space within the F-35 that the F135 occupies today, but it also required the competitors’ variable-cycle engines to demonstrate a 10% maximum thrust increase over the F135, along with a 25% fuel-efficiency improvement and the capability to give the F-35 a 20% range increase.

Also specified, but not in a manner relayed publicly, is that the AETP Phase 1 competitors must provide the F-35 with substantially, perhaps very dramatically, improved thermal management capabilities. Of necessity, those thermal-management capability improvements require that both AETP Phase 1 competitors work very closely with F-35 airframe manufacturer Lockheed Martin to integrate the airframe and its systems with the engine and its systems to an extremely high degree....

...Air Force thinking
Although the AETP R&D programme began in 2016 and specified an adaptive-cycle fan engine which was of the same dimensions as the F135 powering the F-35, the US Air Force and its two AETP contractors said at that time the specification merely served as a convenient reference point for GE Aviation and P&W to assist them in developing their respective AETP Phase 1 engines.

Indeed, each of the two contractors was allowed to inform the AFLCMC of its preference regarding the AETP engine’s physical size and reportedly each asked to be able to develop an F-35-compatible engine. Not until two years later did GE Aviation, in the person of then-GM advanced combat engines Dan McCormick, first confirm publicly—with the US Air Force’s permission—that the AFLCMC had deliberately specified the AETP Phase 1 engine so that it could potentially serve as an F135 replacement.

Asked by AIR International why the US Air Force took this course, Tweedie said it had not wanted at the time to focus public attention specifically on a potential re-engining of the F-35 because the service had believed strongly for years—and had said publicly—that it believed variable-cycle engines would be fundamentally important for all of its future fighter aircraft. When the AETD programme began in 2012, the US Congress had asked about the purpose of the programme and even then the US Air Force indicated it thought adaptive-cycle engines represented the future for all of its fighter types, according to Tweedie.

Before the AETP programme began in 2016, the service had indicated the 10% thrust-increase requirement and the 25% fuel-efficiency improvement “would be foundational for the Air Force to have superiority against adversaries,” Tweedie said. “Neither in words nor actions has the Air Force done or shown anything other than what it said then — this is the future for all our products.”...

...variable-cycle engine technology, which employs at least three airstreams to enhance performance and efficiency throughout the flight envelope, represents the future for military high performance engines, the US Air Force believes. “This is the foundation of a whole new family [of engines] that will mature over the coming decades,” until eventually it too matures to the point where further rapid performance improvement becomes extremely difficult, said Tweedie. “That thinking is what has driven a lot of this [variable-cycle engine R&D] and a lot of the [US] Air Force’s investment in this technology.”"

Source: AIR International APRIL 2019 Vol.96 No.4

Powering the Lightning II
26 Apr 2012 Chris Kjelgaard

"...Maintainability
From the outset the F135 has been designed for maintainability, building on the experience Pratt & Whitney gained with the F100 for the F-15 and F-16 and then with the F119 for the F-22. (When designing the F119, the company brought in US Air Force mechanics to help design its engine-mounted controls and accessories for maintainability). In the F135, all controls affixed to the casing are ‘single-deep’ – no control units are mounted on top of each other – and the nuts and bolts which attach them to the engine casing are encapsulated in the control assemblies themselves, so nuts and bolts stay with the control units when these are removed. This greatly minimizes the risks of nuts and bolts being lost and causing foreign-object debris (FOD) damage.

Similarly, all engine clamps and blocks stay on the engine casing when an F135 is removed for maintenance and the engine uses no safety wire, eliminating another potential source of FOD damage. All controls and accessories are mounted on the bottom of the engine, making it easier for mechanics to get to them; and these assemblies are modular so that, say, a mechanic could easily remove the electronics or valves or relays for an F135 fuel control unit as entire modules.

O’Donnell says the US Air Force has found the F119 to be “significantly more maintainable” than the earlier F100 – the F119 offers “major orders” of improvement of mean time between failures in terms of maintenance man-hours required – and says P&W expects operators to find the F135 even more easily maintainable and reliable than the F119. Another plus, he says, is that P&W can apply the design-for-maintainability improvements it has developed for the F135 to new F119 production batches as well....

...So seriously did P&W take the job of making the F135 highly maintainable that it tried to design the engine to require only a single hand tool, clamped to the engine when not in use, for all line maintenance jobs. P&W couldn’t quite achieve that ideal but did succeed to the point where only six hand tools are required....
&
...Another key feature of the F135 is its augmentor, or afterburner system. While available details of the augmentor are sketchy, the F135 is known to employ multi-zone (probably three-zone) fuel injection aft of the afterburner’s pilot light. These zones inject fuel independently, so that the afterburner does not act in an all-or-nothing way but instead provides a variable range of additional, smoothly transitioning wet thrust at the pilot’s command. Also, like the F119 augmentor, the F135 augmentor is stealthy: The design of the two engines’ augmentors places multi-zone fuel injection into curved vanes which eliminate conventional spray bars and flame holders and block the line of sight to the turbine when looking into the engine from behind....

Source: http://militaryrussia.ru/forum/download ... p?id=28256 [PDF 12.8Mb] also in forum somewhere

12 Jul 2006 'snypa777' said: "...Another interesting area is the engine thrust increase on the "B" model. The auxiliary inlets were re-shaped giving an extra 600lbs of oommph! Shutting off the roll posts during a rolling take off added another couple of thousand lbs of thrust out back [Brit Engineer Idea]...."

"...The Rolls-Royce LiftSystem
One of the most remarkable features of the F-35 programme is that when the STOVL F-35B is hovering, its propulsion system produces very nearly as much thrust without afterburner as the engine does in forward flight with its afterburner fully lit. The F-35B’s engine has to produce 39,400lb (176kN) of vertical thrust without afterburner in hover mode, while in conventional flight it produces 28,000lb (124.55kN) of dry thrust and 43,000lb (191.27kN) with full afterburner.

The F135-powered F-35B relies on two systems to achieve the high level of vertical thrust. First is its full authority digital engine control (FADEC) unit – computers made by BAE Systems and attached to the engine, but running on Pratt & Whitney proprietary FADEC software. In hovering flight, the FADEC computers make the engine work harder, allowing it to increase dry thrust from 28,000lb to 39,400lb without using afterburner….
&
...When the F-35B is hovering, the driveshaft delivers 28,000 shaft horsepower to the LiftFan’s clutch-and-bevel-gear system so that the LiftFan provides 20,000lb (124.55kN) of downward thrust as a column of cool air. (In the F-35B’s hover mode the coupled F135 - driveshaft arrangement acts exactly like a turboprop engine, except that most of its power
output is used to drive air vertically rather than horizontally, so the F135 is actually the world’s most powerful turboprop engine when installed in the F-35B.) In hover mode another 15,700lb (69.84kN) of thrust exits the engine exhaust as hot gas and is directed downwards at the rear of the aircraft by the aircraft’s three bearing swivel module (3BSM)….
&
...In the F-35B, 3,700lb (16.46kN) of thrust in the form of bypass air is directed out to the two roll posts while hovering...."

From Supersonic to Hover: How the F-35 Flies
21 Dec 2007 Chris Kjelgaard

“...Extra thrust for hovering
But, for hovering, the F-35B can rely on 40,000 pounds of thrust without having to use reheat. The F135's full-authority digital engine control (FADEC) software runs the engine at a higher temperature for hover flight than it does during conventional flight, producing more “dry” thrust than the engine normally develops without activating its afterburner.

“We de-rate for CTOL (conventional take-off and landing)” operations, explained Dan Tennant, Pratt & Whitney's F135 system demonstration and development program manager...."

Source: https://www.space.com/4778-supersonic-h ... flies.html

Navy F135 Engine Tweaks Could Help USAF
27 May 2014 John A. Tirpak

“Hartford, Conn.—A fuel efficiency push on Navy versions of the Joint Strike Fight-er’s F135 engine could benefit USAF’s version as well, Pratt & Whitney next-generation fighter engine chief James Kenyon said. At a company press conference, Kenyon told Air Force Magazine that the Navy’s Fuel Burn Reduction Program, now underway, is a major effort to improve the engine by allowing it to run hotter while using five percent less fuel. Testing in 2016 is expected to certify the technology mature enough to cut it into production thereafter...."

Source: http://www.airforcemag.com/DRArchive/Pa ... -USAF.aspx

"...The Rolls-Royce LiftSystem
One of the most remarkable features of the F-35 programme is that when the STOVL F-35B is hovering, its propulsion system produces very nearly as much thrust without afterburner as the engine does in forward flight with its afterburner fully lit. The F-35B’s engine has to produce 39,400lb (176kN) of vertical thrust without afterburner in hover mode, while in conventional flight it produces 28,000lb (124.55kN) of dry thrust and 43,000lb (191.27kN) with full afterburner.

The F135-powered F-35B relies on two systems to achieve the high level of vertical thrust. First is its full authority digital engine control (FADEC) unit – computers made by BAE Systems and attached to the engine, but running on Pratt & Whitney proprietary FADEC software. In hovering flight, the FADEC computers make the engine work harder, allowing it to increase dry thrust from 28,000lb to 39,400lb without using afterburner….
&
...When the F-35B is hovering, the driveshaft delivers 28,000 shaft horsepower to the LiftFan’s clutch-and-bevel-gear system so that the LiftFan provides 20,000lb (124.55kN) of downward thrust as a column of cool air. (In the F-35B’s hover mode the coupled F135 - driveshaft arrangement acts exactly like a turboprop engine, except that most of its power
output is used to drive air vertically rather than horizontally, so the F135 is actually the world’s most powerful turboprop engine when installed in the F-35B.) In hover mode another 15,700lb (69.84kN) of thrust exits the engine exhaust as hot gas and is directed downwards at the rear of the aircraft by the aircraft’s three bearing swivel module (3BSM)….
&
...In the F-35B, 3,700lb (16.46kN) of thrust in the form of bypass air is directed out to the two roll posts while hovering...."

weasel1962 wrote:Growth 1A for F-35B. 5% increase in hover thrust besides the 10% increase in overall thrust.

https://www.ainonline.com/aviation-news ... e-upgrades

P&W Outlines New Plan for F-35 Engine Upgrades
13 Jun 2018 Chris Kjelgaard

"Pratt & Whitney has changed its proposed upgrade path for the F135 engine powering the F-35 Lightning II stealth fighter. It is now offering two stages of improvements over a four-year period, compared with the three-stage, 10-year plan ending with a completely new engine that it revealed a year ago. The stages are labeled Growth Option 1.0 and 2.0 and include greater thrust, lower fuel burn, and better thermal management.

Matthew Bromberg, president of P&W Military Engines, said this week that since last year, P&W has combined the informally labeled “Growth 1A” thrust-increase option for the F-35B STOVL version, within the overall Growth Option 1.0 package. This package offers 10 percent more thrust than the F135’s current nominal 40,000 pounds, and 5 percent better fuel burn. But for the F-35B, P&W is working with Rolls-Royce to also provide a 5 percent increase in vertical thrust during the hover.

P&W previously described Growth Option 2.0 as an all-new production engine that would result from its adaptive-cycle research and development under the U.S. Air Force Research Laboratory Advanced Engine Transition Program (AETP). Both General Electric and P&W are working on engineering, manufacturing, and development (EMD) contracts from the Pentagon for the AETP, which could power a sixth-generation fighter aircraft.

However, Bromberg said that Growth Option 2.0 for the F135 could now provide the F-35 with “a significant increase in power and thermal management capability” within four years, rather than being a completely new engine design, which might not be available until a decade hence.... [then a bunch of stuff about Growth Option 2.0]

Source: https://www.ainonline.com/aviation-news ... e-upgrades

Powering the Lightning II
April 2012 Chris Kjelgaard

"...Also, like the F119 augmentor, the F135 augmentor is stealthy: The design of the two engines’ augmentors places multi-zone fuel injection into curved vanes which eliminate conventional spray bars and flame holders and block the line of sight to the turbine when looking into the engine from behind...."

Source: http://militaryrussia.ru/forum/download ... p?id=28256 (PDF 12.5Mb)

spazsinbad wrote:AIR International Magazine JUNE 2015 Vol.88 No.6 "Towards Tomorrow’s United States Fighter Engine" Chris Kjelgaard

optimist wrote:one thing for certain is that it isn't an AB spray bar, the F-35 doesn't have one.

spazsinbad wrote:

Powering the Lightning II
April 2012 Chris Kjelgaard

"Also, like the F119 augmentor, the F135 augmentor is stealthy: The design of the two engines’ augmentors places multi-zone fuel injection into curved vanes which eliminate conventional spray bars and flame holders and block the line of sight to the turbine when looking into the engine from behind...."

Source: http://militaryrussia.ru/forum/download ... p?id=28256 (PDF 14Mb)
Engine F135 & LiftFan STOVL F-35LightningII pp6ed.pdf
download/file.php?id=19133 (PDF 1.5Mb)

Powering the Lightning II
April 2012 Chris Kjelgaard

"...Another key feature of the F135 is its augmentor, or afterburner system. While available details of the augmentor are sketchy, the F135 is known to employ multi-zone (probably three-zone) fuel injection aft of the afterburner’s pilot light. These zones inject fuel independently, so that the afterburner does not act in an all-or-nothing way but instead provides a variable range of additional, smoothly transitioning wet thrust at the pilot’s command. Also, like the F119 augmentor, the F135 augmentor is stealthy: The design of the two engines’ augmentors places multi-zone fuel injection into curved vanes which eliminate conventional spray bars and flame holders and block the line of sight to the turbine when looking into the engine from behind...."

Source: http://militaryrussia.ru/forum/download ... p?id=28256 (PDF 14Mb)

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

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

"...Can the liftfan thrust be vectored via louvres or some similar mechanism? I seem to recall reading about "louvres" somewhere with respect to the liftfan, but I thought that was more with respect to adjusting volume flow rate for purposes of increasing / decreasing thrust."

Powering the Lightning II
April 2012 Chris Kjelgaard

"...…Below the LiftFan, the variable area vane box (VAVB) provides an exit path for the cool air driven downwards vertically by the LiftFan. Rolls-Royce produces the VAVB, which is made of aluminium and contains louvred vane doors. These can be angled all the way from 45° back, through fully vertical to 5° forward to provide variable directionality for the downward cool-air flow from the LiftFan, as commanded by the pilot through the aircraft’s FADEC units.

...When the F-35B hovers, the FADEC commands the 3BSM [3BSN] – which can direct air through a 95-degree range from 5° forward to horizontally back – to swivel downwards to direct hot engine exhaust air in the same direction as the direction of the cool air produced by the LiftFan near the front of the aircraft. The 3BSM [3BSN] can swivel fully from horizontal to vertical orientation in 2.5 seconds…."

Source: http://militaryrussia.ru/forum/download ... p?id=28256 (large PDF)

Powering the Lightning II
April 2012 Chris Kjelgaard

"......Another key feature of the F135 is its augmentor, or afterburner system. While available details of the augmentor are sketchy, the F135 is known to employ multi-zone (probably three-zone) fuel injection aft of the afterburner’s pilot light. These zones inject fuel independently, so that the afterburner does not act in an all-or-nothing way but instead provides a variable range of additional, smoothly transitioning wet thrust at the pilot’s command. Also, like the F119 augmentor, the F135 augmentor is stealthy: The design of the two engines’ augmentors places multi-zone fuel injection into curved vanes which eliminate conventional spray bars and flame holders and block the line of sight to the turbine when looking into the engine from behind...."

6 page PDF ARTICLE available HERE: Engine F135 & LiftFan STOVL F-35LightningII pp6ed.pdf

download/file.php?id=19133 (1.5Mb PDF)

Source: http://militaryrussia.ru/forum/download ... p?id=28256 (PDF 14Mb)