Powering the Lightning II

All about the Pratt & Whitney F135 and the (cancelled) General Electric/Rolls-Royce F136
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Unread post01 Jul 2014, 21:53

More on the F135 engine variants - quotes only relevant to my interest however there is much more in the PDF with more articles in it available online.
Powering the Lightning II
April 2012 Chris Kjelgaard

"...The LiftFan (one of three major components of the Rolls-Royce LiftSystem, which provides the F-35B’s hover capability) is not engaged while in normal forward flight and does not feature at all in the F-35A CTOL and F-35C CV conventional take-off and landing variants of the Lightning II. However, from the outset the specification for the F-35’s engine called for “tri-variant compatibility”: the engine powering an F-35A is identical to that powering an F-35B or an F-35C. Nevertheless, the engines are designated differently: the F-35A powerplant is the F135-PW-100; the engine for the F-35C is the F135-PW-400; and the F-35B engine is the F135-PW-600.

Since the F-35B powerplant needs an extra LPT stage to provide the power necessary to turn the driveshaft (which, through a clutch and gearbox, drives the LiftFan), F135s built to power other F-35 variants have the second LPT stage as well. “The engine was designed to support that severe STOVL requirement,” says O’Donnell. For engines powering CTOL F-35As and F-35Cs, the additional turbine stage offers a substantial extra power margin, allowing for potential F-35 weight growth. Since the engine isn’t heavily taxed in many CTOL missions, its maintainability is improved too....

...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....

...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.

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....

...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....

...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....

...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 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). This remarkable piece of equipment consists of three articulated sections of nozzle casing, each of which is made from titanium. Each section is joined to the other sections by and driven by its own ring bearing. When the F-35B hovers, the FADEC commands the 3BSM – 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 can swivel fully from horizontal to vertical orientation in 2.5 seconds....

...According to Jones, the roll posts themselves are variable-area nozzles which are situated in the lower part of each inner wing section and act to provide roll control for the F-35B while it is in hover mode. In order to do this, the roll-post ducts direct bypass air from the engine to the roll posts, which drive the air out through the bottom of each wing. 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.

Each roll-post assembly features a pair of flap-type doors in the bottom of the wing, controlled by the FADEC. Jones says these titanium doors are controlled by rotary actuators which allow fully variable opening, providing a degree of thrust variability and directionality so that the pilot can control roll while hovering. He says Lockheed Martin’s original X-35 concept demonstrator featured doors between the engine casing and the roll-post ducts which could be closed when the aircraft was not hovering, but in production aircraft there are no such doors and bypass airflow is constantly sent to the ducts. The only way to control roll-post thrust is via the flap-doors in the bottom of the wing.

The demand for very high power during hover requires that the engine receive a high amount of airflow, so Lockheed Martin designed the F-35B with a pair of auxiliary air inlet (AAI) doors in the upper surface of the fuselage behind the big inlet door for the LiftFan. These AAIs provide additional inlet air for the F135 engine, not the LiftFan...."

Source: http://militaryrussia.ru/forum/download ... p?id=28256 (PDF 14Mb)
Last edited by spazsinbad on 01 Jul 2014, 23:31, edited 4 times in total.
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Unread post01 Jul 2014, 22:03

43,000lb of thrust installed?
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Unread post01 Jul 2014, 22:56

The article is two years old and here is the last LM Fast Facts (which is dodgy anyway but hey everything on the internet is dodgy/counterfeit/whatever). NOW the 6 page ENGYN artickle is attached below.... WITH another Quotable Quot from it:
"...Boley has also suggested the F135 has an uninstalled wet-thrust capability of approximately 51,000lb..."

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Unread post02 Jul 2014, 00:53

and the engine uses no safety wire


Please let the whole plane be that way.
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Unread post02 Jul 2014, 02:53

LM often states that the F-35 has 40,000lbs of thrust in full AB

but other sources peg it at 43,000lbs and Jon Beesley once said it was 41,000lbs

Now I know that installed thrust can swing wildly depending on air density which is mostly dependent on altitude.

But can't they all agree on a fixed published max thrust figure. most planes have a fixed figure no matter where you check.

F-15C = 50,000 lbs
F/A-18E/F = 44,000 lbs
F-22 = >70,000 lbs

F-35..well it depends where you look, anywhere from 39,000lbs to 43,000 lbs
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Unread post02 Jul 2014, 06:58

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Unread post02 Jul 2014, 07:50

JOINT STRIKE FIGHTER Boeing X-32 - Lockheed Martin X-35
Geoffrey Buescher 23 April 2001

"...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.

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 and avionics.

Cold flow from lift fan protects inlet from hot gas ingestion..."

Source: http://www.dept.aoe.vt.edu/~mason/Mason ... escher.pdf (0.7Mb)
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Unread post05 Jul 2014, 15:53

The latest estimate on thrust figures. It seems the A/C variant engines are rated at 43,000lb but the B is rated a little lower probably due to the drive mechanism from the 2nd LPT to the lift fan.

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Unread post05 Jul 2014, 16:11

Some slight difference in BPR too.

It seems what was once defined as BPR has been changed. 0.57 used to mean that 0.57kg of air bypasses for every 1kg that goes through the core. In this case, see scan above, 57% of the air bypasses. I make that a 1.33 BPR (0.57/0.43)???

http://www.pratt-whitney.com/Content/F1 ... sChart.pdf


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....

So are aircraft engines usually quoted on installed thrust or uninstalled thrust?
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Unread post05 Jul 2014, 20:37

'uclass' thanks for the info. It would be very useful to know the publication / date please. I see there are other pages on your PhotoBucket site. I do not have easy access to print publications at local newsagent but may buy online if available. Meanwhile here is the latest LIGHTNING special from AIR International/Key Pubs July 2014.

ADDITION: OK now I see in the 'AVIONICS' section that the other pages have been posted and 'sferrin' has given a clue as to the publication which is the same in the first graphic below from KeyPubsAIRintentional.... GOOD TO KNOW! :mrgreen:
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Unread post09 Jul 2014, 21:01

At some point I'll compare the numbers from the 2012 edition in the first post of this thread to the 2014 edition below. Shoulda waited for this edition eh.
RAW POWER
July 2014 Chris Kjelgaard, AIR International F-35 Special Edition

"...F135 Propulsion System
The F135 and F119 are both axial-flow engines (air goes through the core of the engine in a straight line) and they share a “highly common core”, Ed O’Donnell, Business Development Director for Pratt & Whitney’s F135 and F119 programmes, told AIR International. From front to back, these two-spool engines are “largely common through the compression system”, said O’Donnell, who noted that the commonality is however mainly in the form of shared engine architecture rather than common part numbers.

Part numbers for the F135 have been designated differently from those for similar components in the F119 because the US armed services want to be able to allocate specific part numbers to particular programmes for inventory management reasons.

Despite their similarities, there are however some crucial differences between the F135 and the F119. One is that the F135 needs to be able to generate up to 43,000lb (191.27kN) of thrust ‘wet’ (with afterburner) for the single-engine F-35, whereas the F119 provides 35,000lb (155.7kN) with full afterburner. So the F135 has a larger inlet diameter (43 inches/1,090mm), larger fan diameter (46 inches/1,170mm) and a larger overall engine diameter (51 inches/1,295mm) than the F119 to achieve a higher airflow.

According to Pratt & Whitney, the maximum thrust of the F-35B STOVL variant is a little lower than that for the F-35A CTOL and F-35C CV variants, at approximately 41,000lb (182.4kN) at full reheat. The F-35B’s intermediate thrust level (that is, dry thrust with no reheat applied) is approximately 27,000lb (120.1kN). The maximum thrust available for a short take-off is 40,740lb ( 181.2kN), while the maximum downward thrust available for hovering and vertical landings is 40,650lb (180.8kN)....

...Aft of the third fan stage the accelerated airflow is split, 57% of it going through the fan duct as bypass air and the remaining 43% entering the core to be compressed, mixed with fuel, ignited and then exhausted as hot gas to turn the turbine stages and produce up to 28,000lb (124.55kN) of dry thrust before afterburner....

...from the outset, the specification for the F-35’s engine called for ‘tri-variant compatibility’ – the engine powering an F-35A is identical to that powering an F-35B or an F-35C. Nevertheless, they are designated differently: the F-35A powerplant is the F135-PW-100; the engine for the F-35C is the F135-PW-400; and the F-35B’s is the F135-PW-600....

...Nor will P&W confirm the dry weight of the F135, but in 2011 an aviation blog cited Warren Boley, former president of Pratt & Whitney Military Engines, as saying the F135 weighs 1,500lb (680kg) more than the F119. This would put its 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), so the 5,400lb figure might be too high.

Boley also suggested in 2011 that the F135 had 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, reducing the overall dry-thrust capability by a fraction – it should provide a comfortable operating margin over the 43,000lb (119.27kN) of wet thrust required by the spec....

The Rolls-Royce LiftSystem
...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 40,650lb (180.8kN) of vertical thrust without afterburner in hover mode, while in conventional flight it produces 27,000lb (120.1kN) of dry thrust and about 41,000lb (182.4kN) 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 run on Pratt & Whitney proprietary FADEC software. In hovering flight, the FADEC computers make the engine work harder, increasing dry thrust from 28,000lb to 39,400lb without using afterburner.

Second, the F-35B relies on the Rolls-Royce LiftSystem. This consists of several major components. First is the LiftFan, a horizontally-mounted fan unit located behind the F-35’s cockpit. The 53-inch (1,346mm) diameter, 50-inch (1,270mm) deep LiftFan draws in cold air through a 51-inch (1,295mm) diameter inlet on the top of the fuselage and accelerates it to produce vertical lift [temperature?].

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 18,680lb (83.1kN) of downward thrust as a column of cool air. (In hover mode the F-35B’s 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 18,680lb (83.1kN) 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).... When the F-35B hovers, the FADEC commands the 3BSM – which can direct air through a 95-degree range from 5 degrees 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 can swivel fully from horizontal to vertical orientation in 2.5 seconds, completely redirecting its entire 18,680lb of thrust in that time. Together with the 18,680lb of downward thrust produced by the LiftFan and the 3,290lb (14.6kN) of bypass-air thrust directed vertically downwards by the F-35B’s two wing-positioned Roll-Posts (see below) to enable the F-35B to hover, this means the F-35B can turn 18,680lb of horizontally directed thrust into 40,650lb (180.8kN) of thrust directed vertically downward in less than 3 seconds.

This astonishing capability to redirect – in the twinkling of an eye – more thrust than powers two BAE Systems Hawks and, at the same time, more than double its thrust output to turn it into more thrust than powers a Panavia Tornado at full reheat (and nearly as much as powers a fully-reheated Eurofighter Typhoon) is made possible by the F-35B’s enormously sophisticated FADEC software, which was developed by Pratt & Whitney specifically for the F-35B’s propulsion system.

F135 CTOL/CV Engine Design
Maximum thrust 43,000lb (191.3kN)
Intermediate thrust 28,000lb (128.1kN)
Length 220 inches (5.59m)
Inlet diameter 43 inches (1,090mm)
Maximum diameter 46 inches (1,170mm)
Bypass ratio 0.57
Overall pressure ratio 28

F135 STOVL Propulsion System Design
Maximum thrust class 41,000lb (182.4kN)
Intermediate thrust class 27,000lb (120.1kN)
Short take-off thrust class 40,740lb (181.2kN)
Hover thrust 40,650lb (180.8kN)
Main engine 18,680lb (83.1kN)
LiftFan 18,680lb (83.1kN)
Roll-Post 3,290lb (14.6kN)
Length 369 inches (9.37m)
Main engine inlet diameter 43 inches (1,090mm)
Main engine maximum diameter 46 inches (1,170mm)
LiftFan inlet diameter 51 inches (1,300mm)
LiftFan maximum diameter 53 inches (1,340mm)
Conventional bypass ratio 0.56
Powered Lift bypass ratio 0.51
Conventional overall pressure ratio 28
Powered Lift overall pressure ratio 29"

Source: AIR International F-35 Special Edition July 2014
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Unread post11 Jul 2014, 06:46

Some incomprehensible to me engineering stuff in the attached PDF.
JOINT STRIKE FIGHTER Boeing X-32 - Lockheed Martin X-35
Geoffrey Buescher 23 April 2001

"...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.

• 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 and avionics.

Cold flow from lift fan protects inlet from hot gas ingestion..."

Source: http://www.dept.aoe.vt.edu/~mason/Mason ... escher.pdf
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Unread post11 Jul 2014, 11:58

spazsinbad wrote:Some incomprehensible to me engineering stuff in the attached PDF.
JOINT STRIKE FIGHTER Boeing X-32 - Lockheed Martin X-35
Geoffrey Buescher 23 April 2001

"...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.

• 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 and avionics.

Cold flow from lift fan protects inlet from hot gas ingestion..."

Source: http://www.dept.aoe.vt.edu/~mason/Mason ... escher.pdf

Fairly logical. Turbine extracts work from the hot, high pressure gas after the combuster at a rate of about about 70,000-80,000hp (52.22-59.68kW). 27,000-28,000hp (20.142-20.888kW) of that is used to drive lift fan, which has a pressure ration across it of 2, i.e. exit gas is twice pressure of ambient air. Lift Fan Thrust = (Pout - Pin) x Exhaust Area = 18,000lbf = ~80kN Pout = 2*Pin, so Lift Fan Exhaust Area = 80,000N/101,325Pa = 0.79m^2. Lift Fan Exhaust diameter = 1m.

Using cooler lift fan flow for thrust means that the main inlets aren't taking in hot exhaust gas from some kind of Yak-141 setup, which would degrade main engine efficiency, since it's easier to do work on a cold gas.
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Unread post11 Jul 2014, 16:39

Anyone have any idea what the coooool exhaust gast temperature from the LiftFan will be please? Any guesses will do. Thanks.
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Unread post11 Jul 2014, 17:05

Slightly above ambient air temp due to compression and friction.
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