Monday, May 19, 2008

A beautiful quote

I believe in love at first sight. Because I loved my mother ever since I opened my eyes.

- Anonymous

I just read it in yesterdays Newspaper and thought of sharing it with you all. Beautiful.

Rule 49-O: Vote for NO ONE!! (India)

Rule 49 OI am a member of a Tech-oriented discussion forum, whose members have clear and quite often strong opinion about issues. So naturally when the Supreme Court upheld the Indian Government’s decision to introduce 27% reservation for members of the Other Backward Class (OBC) category in Educational Institutions, with riders, it was natural that a heated discussion would ensue on this issue. During the course of the discussion, quite naturally, members started bemoaning about the absence of a deserving, credible candidates who could be voted to the Parliament and how we were being forced to elect the best among the worst who later go on to mess things up at a National level. If only we had a say in the kind of candidates being nominated to contest the election by their respective parties, things would have been so much better. Well believe it or not, you actually can!

I had first read about the Rule 49(O) some months [years??] back while going through an issue of JAM.

Rule 49O of the THE CONDUCT OF ELECTIONS RULES, 1961 states that,

49-O. Elector deciding not to vote.-If an elector, after his electoral roll number has been duly entered in the register of voters in Form-17A and has put his signature or thumb impression thereon as required under sub-rule (1) of rule 49L, decided not to record his vote, a remark to this effect shall be made against the said entry in Form 17A by the presiding officer and the signature or thumb impression of the elector shall be obtained against such remark.

Rule 49 O has also been mentioned on the Election Commission of India’s website.

This means that you go to your polling station, sign on the relevant documents that state you had visited your polling station for exercising your right to franchise and then vote for no one. This might appear strange - the act of going to the polling station and then voting for no one. One may argue that if you are not planning to vote anyone to power, why waste a perfectly fine holiday (on the day of polling, a public holiday is declared by the government in the region to enable people to caste their votes) to visit the polling station at all.

Haaaah! here lies the beauty of this Rule. Unlike not turning up to cast your vote, where some candidate will invariably win, even if (s)he gets 1 vote, by exercising your right to invoke Rule 49O, you can actually reject all the contesting candidates. For this to happen, the number of voters invoking Rule 49-O must exceed the number of votes cast. Once rejected, they can not be re-nominated by their parties to contest the by-elections (re-election) that would be held in that region. Thus the political parties will have to nominate new candidates to contest election in that region and for the fear of being rejected again, they might decide to give the party ticket to a genuine, credible candidate this time around.

How does one do it?

In the earlier setup, where votes were cast into ballot boxes, it was extremely simple to do it. All one had to do was take the ballot paper issued to you and drop it in the box without putting the stamp on any candidate. This, when counting the ballot papers, would be taken as an indication of Rule 49-O being invoked by the voter.

However, with the introduction of Electronic Voting Machines [EVM] in all forms of Elections [or at least in the Municipal Corporation, Assembly and General elections that I have voted in], one has to approach the presiding officer from the Election Commission and ask for the relevant form and once filled, the voters choice is noted.

Critics, quite rightly, argue that this is in complete violation of one of our rights as an Indian citizen - secrecy of the ballot. The choice exercised by a voter is to remain a secret and no one has the right to know the choices we make. By approaching the officer and requesting for the form we give up this right as everyone would come to know about the choice you make - that of not choosing anybody. A ’None of the above’ button could easily have been added to the E.V.M for voters to exercise this right, but strangely enough the Election Commission has so far refrained from doing so.

However, Proposed Electoral Reforms [PDF, 164 KB] have recommended the addition of such a button in the E.V.M. Till such time this button is added, we will have to approach the presiding officer in person, thereby waiving our right to secrecy of ballot.

This rule, in my opinion, is a serious weapons in our arsenal to bring about improvements in our society and must not hesitate to invoke it whenever required for the greater good.

Strangely and quite pleasantly surprising enough, the first result that Google throws up when you go looking for information about Rule49O is that of a Belgian National’s blog who, from what I gathered from her blogs, is some sort of an Indophile.

References: -

Sunday, May 11, 2008

To a higher Degree : M.S./M.Tech or M.B.A.?

Many of us who are pursuing a degree in Engineering are often faced with the dilemma of choosing an appropriate Postgraduate degree to pursue. This is especially true for those of us who are on the verge of graduating. One may either choose to pursue a M.Tech/M.S. or acquire a M.B.A. degree. I too was in a similar quandary. The following article that I have reproduced here addresses these very issues and could help us make the correct choice.

The article has been written by Dr. Kevin D. Kuznia (Ph.D), who besides being associated with John Deere (Deere & Company) is also the principal of his career consultation firm

The article had originally appeared in the March 2008 edition of the Mechanical Engineering Magazine, a periodical that I read with avid interest. The magazine is brought out by the American Society of Mechanical Engineers (ASME). On reading the article I found it very relevant and informative. Wanting to share the article with my friends and classmates [terms not really mutually exclusive :)], I sought the permission of Dr. Kuznia, who very graciously gave his consent for me to republish his article on my blog. I hope you find this article just as helpful as I have.



To a higher Degree

How do you decide which advanced course of study is the best option for your career?


The phone rings once again. On the other end is an engineer confused about continuing his formal education. He has been in engineering for a few years. He sees his colleagues pursuing either an M.B.A. or an M.S. in engineering.

While both are noble pursuits, each is a distinct path to follow, with different expectations and outcomes. Theoretically the option exists to pursue both paths. However, such an endeavour is rarely practical, partly because of the expense involved and even more so because of the daunting prospect of spending six years or more juggling graduate study and full-time engineering employment. So how does anyone decide which road to take?

which direction to head

In my endeavours as a career consultant, I work with a steady progression of engineering professionals. These individuals, who thrive on data and analysis, seem to become paralyzed when deciding whether or not to pursue advanced education. To add to the confusion, I often hear, "Well, my boss said…" or, "This guy just got his degree and he got promoted."

But is an advanced education the answer? Frankly, not for everyone. But if it is something you choose to undertake, which degree should you pursue?

Yesterday's engineering careers were a little simpler than today's. Then, you went to college for four years, graduated, and took a job as a junior engineer until you earned the title of advanced or senior engineer. Through organizational tenure, you moved up in the engineering world until perhaps one day you became engineering manager. There was less need to consider advancing your formal education, because nearly everything you needed to know was gained through on-the-job experience, and a few hard knocks. And those M.B.A.'s? They were locked in the business office trying to figure out how to take the company to "the next level."

Today's engineering careers have changed. Not only must you keep up with emerging technologies, but you also have to understand the financial and strategic ramifications of your decisions. When designing parts or systems, you may be peppered with questions from marketing, accounting, and other engineering groups. It would appear that gaining an advanced education may put you on equal footing with these individuals. Having that degree can, and does, level the playing field-as long as you choose the right degree and apply your newly gained knowledge in the correct fashion.

So, let's look at each of these degrees to determine the prerequisites, effort for completion, and potential impact on your career.

What Is an M.B.A.?

The M.B.A., or Master of Business Administration degree, has been around since the beginning of the 20th century. It is a very popular degree program, attracting people from a wide range of academic disciplines outside of business.

Prerequisites for M.B.A. programs vary. Some programs have very liberal admission requirements. Some require no previous business courses. However, nearly all applicants to M.B.A. programs are required to take the Graduate Management Admission Test. The GMAT is designed to assess quantitative reasoning and verbal skills. Depending upon the university, work experience, academic transcripts, essays, references or letters of recommendation, and personal interviews may be considered for admission to a program. In addition, competitive schools also may be interested in extracurricular activities, community service, and how the applicant can improve the program's diversity and contribute to the student body as a whole.

Full-time M.B.A. programs are the most common, normally lasting two years. Students may or may not enter the program with real-world work experience. The classes are typically conducted during weekdays, like undergraduate university classes. Most students are in their early 20s with few over 30.

Part-time M.B.A. programs are geared toward older working adults. Universities typically hold classes on weekday evenings, after normal working hours. The students in these programs typically consist of working professionals, who take a lighter course load for a longer period of time. These programs generally last three years or more.


Executive M.B.A. (or E.M.B.A.) programs were developed to meet the educational needs of managers and executives, allowing students to earn a degree in two years or less while working full-time. E.M.B.A. students generally have a higher level of work experience, often 10 years or more, than other M.B.A. students. Classes are typically a mix of weekend courses combined with electronic correspondence.

Upon starting an M.B.A. program, a student can expect to take classes in a variety of areas. Core subjects typically include economics, organizational behavior, marketing, accounting, finance, strategy, operations management, and information technology management. Some students may then seek to specialize in an area such as international business, supply chain management, or project management.

An engineer who pursued a management degree is someone I'll call Steve. He was a very successful mechanical engineer for a Fortune 500 manufacturing company and had always had ambitions to become an engineering manager like his college intern mentor. He asked his former mentor what skills would be necessary to move into a management position. He learned that, although technical skills were necessary, business skills also play a big part in management, and so he decided to pursue a master's degree in business administration.

Through his M.B.A. program, Steve learned how to effectively manage people, how various aspects of corporate finance worked, and how the contributions of his department supported the overall strategy of the company. According to Steve, these were all important aspects to a successful engineering management career. Steve is now the vice president of engineering for his company, and suggests that the keys to his success were a solid technical background in engineering combined with business acumen gained from earning his M.B.A.

Upon completing an M.B.A. program, you should be well versed in the language of business. You should have a clearer appreciation of how your actions affect the business bottom line. You should also have acquired a skill set that is applicable to many different types of organizations. In addition, you'll have developed a broad-based network of professionals employed in a variety of industries.

On the negative side, many individuals are pursuing an M.B.A. Differentiation among M.B.A.'s in organizations is becoming increasingly difficult. It will be up to you to apply your newly gained knowledge to stand out among the ever-increasing M.B.A. crowd.

The Other Path

By contrast, then, what is an M.S. in Engineering? A Master of Science in Engineering takes your undergraduate engineering education to a more advanced level. In the undergraduate program, you became well versed in the foundation of knowledge necessary to be an engineer. You gained the vocabulary, the analytical reasoning, concepts, and principles that engineers must have to be successful in the field.

Students completing the master's degree in engineering typically acquire a greater depth and breadth of engineering analysis skills, enabling them to better understand and predict the performance of engineered systems and components. They should be able to more effectively understand and utilize research on engineered systems and on phenomena integral to their performance. As a result, graduates should be in a position to better contribute to the body of knowledge available to business and industry, and to more effectively solve complex engineering problems affecting their respective organization.

To apply to a master's program in engineering, applicants typically must have a bachelor's degree from an accredited university with a suitable engineering background for the selected area of study, and a minimum 3.0 grade point average in their undergraduate program. Some universities may grant latitude in the requirements if the applicant can demonstrate extenuating circumstances.

In terms of course structure, master's degree in engineering programs usually follow a pattern similar to bachelor's degrees with lectures, laboratory work, course work, and exams. Many universities require the completion of a substantial project in the final year.

Upon completing a master's degree in engineering, you should possess a much deeper knowledge of a specific engineering discipline. You should also have gained new perspectives on emerging trends in engineering, and have developed network contacts who share your passion for engineering.

Consider, for example, someone I'll call Chad. He truly enjoyed his job as an engineer for a large automotive manufacturer. As engineers often are, he was inquisitive, and would often be found reading about the latest advancements in his field of expertise. With encouragement from one of his peers, Chad enrolled in a Master of Science in Engineering program offered by a local university.

Although it took Chad three years to complete the program, he said that it was time well spent. He met several individuals who shared his passion for engineering, and co-authored a technical paper with one of his professors. Chad said that through the pursuit of the master's degree, he is now even more confident in his abilities as an engineer, and finds himself more marketable to other companies.

Unlike the latitude offered M.B.A. students, you will not find the same variety of programs in engineering. There are very few accelerated master level engineering programs, but you typically will have the advantage of not having to take prerequisites in order to start the program. However, unlike an M.B.A., which may require engineers to take prerequisite business classes before they start the actual degree program, in a master's program in engineering you'll typically be allowed to take master's level classes immediately.

Which Way to Go?

Neither degree is inherently better than the other. That would be like comparing business to engineering. Each discipline supports the organization in its own way. Each has distinct advantages and disadvantages, and it is up to you to decide which one supports your career objectives more appropriately.

The M.S.E. is marketable, but in a different way from an M.B.A. However, many individuals outside the engineering discipline will have scant knowledge of just how your degree contributes to the organization. The M.B.A., on the other hand, is a widely recognized degree, and many people within and outside of engineering understand how an M.B.A. contributes to an organization's success. Both degrees can contribute to career advancement. It is important to let others know how your advanced education contributes to the goals of the organization.

Deciding to obtain an advanced degree, whether it is in engineering or business, requires a commitment of time, effort, and expense. But more important, the right degree can make a huge difference in career opportunities. I often counsel individuals by saying that investments in yourself pay the highest dividends. It's up to you to decide where the biggest payoff is.

what about distance learning?

Whether you are considering an M.B.A. or M.S. in Engineering, distance learning has recently received increased attention in education as more universities are holding classes off-campus.

Distance learning programs are available in a number of formats: offline or online computer courses, correspondence courses that utilize e-mail, prerecorded video, and live teleconferences.

Many traditional schools offer these programs, but so do diploma mills. If you're considering this option, be sure to check the school's accreditation before undertaking distance learning coursework.

Kevin Kuznia obtained his doctorate in business administration from St. Ambrose University in Davenport, Iowa, and is the principal of, a career consultation firm that provides career insights and support to engineering professionals. He is the diagnostic supervisor at Deere & Co. in Waterloo, Iowa, where he also counsels colleagues on career choices. He can be reached at KuzniaKevinD[at]JohnDeere[dot]com.

The original article can be read here

Friday, May 09, 2008

F-35 Joint Strike Fighter program: An overview 04

Read the previous parts: Part 1, Part 2, Part 3

A comparison between the F-35B and Harrier w.r.t. STOVL





true multi-role capability

specialised role










Pilot workload




single seat only

single seat

(twin seat trainer)


single F135/136

(40000lb thrust class)

single Pegasus

(23000lb thrust class)

Weapons carriage

internal and external carriage

external carriage only


all weather precision capability

weather restricts operations

Ability to fly intensive operations

yes, for a sustained period

yes, for short periods


more reliable and ability to predict failures

no ability to predict failures


The F-35 Joint Strike Fighter will be:

  • Four times more effective than legacy fighters in air-to-air engagements

  • Eight times more effective than legacy fighters in prosecuting missions against fixed and mobile targets

  • Three times more effective than legacy fighters in non-traditional Intelligence Surveillance Reconnaissance (ISR) and Suppression of Enemy Air Defenses and Destruction of Enemy Air Defenses (SEAD/DEAD) missions

  • About the same in procurement cost as legacy fighters, but requires significantly less tanker/transport and less infrastructure with a smaller basing footprint


In spite of being far more technically superior than any legacy fighter aircraft, the production cost of the F-35 JSF would be about the same as that of legacy fighter aircraft, making it highly affordable aircraft and offering great value for money to the purchaser. It is able to achieve this by introducing an unprecedented level of commonality between the three variant of aircrafts. The JSF concept is building these three highly common variants on the same production line using flexible manufacturing technology. Cost benefits result from using a flexible manufacturing approach and common subsystems to gain economies of scale. Cost commonality is projected in the range of 70-90 percent; parts commonality will be lower, but emphasis is on commonality in the higher-priced parts. Early interaction between the end-user and developer ensures cost / performance trades are made early, when they can most influence weapon system cost. By adhering to their objective of “Get it right the first time”, they are able to avoid a lot of wasteful expenditure and thus save a lot of resources.



The JSF team would employ advanced assembly methods and highly accurate manufacturing machines to help the F-35 achieve its goals of affordability, quality and assembly speed. The concept of Lean Manufacturing is a key feature in the whole JSF manufacturing program. In fact their objective is to achieve what they term as Leaner-than-Lean Manufacturing.

The F-35 is the first aircraft to be designed entirely using a Solid Modelling Package – CATIA. Three-dimensional solid models provide an exact representation of each part, thus forming the foundation of any subsequent operations. Everybody involved would use the same digitally generated product data to perform their tasks like assembly, supply, CAM programming, and laser-tracking. This paperless method of functioning is expected to save millions of dollars. The product data obtained from the digital model would be used in simulation, tooling, fabrication, assembly and mating. New milling machines accurate to less than the width of a human hair ensure that the F-35’s outer shape is exact and meets its low-observability (stealth) requirements. Assembly time for an F-35 is planned to be less than half that of current-generation fighters. The F-35 JSF production line would be the state-of-the-art model for high-quality, affordable combat aircraft in the 21st century.

The assembly line of the F-35 would make use of industrial Laser Trackers to obtain proper mating of the different modules. The Laser Tracker is a state-of-the-art precision instrument to precisely align the mate components to an extremely close tolerance. The laser tracking technology is used to set up, measure and inspect assembly-tooling details based on CAD models. The 3-D laser interferometer and angular encoders deliver a high-speed measuring rate of 1,000 points per second, and a measurement volume of 70m diameter.

Advanced production processes, including integration of the digital, paperless factory, are being implemented into F-35 production plans. Lean manufacturing principles, incorporation of shortened flow spans, use of a single, flexible production line for all three variants, use of best-value sourcing within a commercial framework — all these steps would yield measurable results in the production phase.


Commonality is the key to affordability – on the assembly line; in common systems that enhance maintenance, field support and service interoperability; and in almost 100 percent commonality of the avionics suite. Component commonality across all three variants reduces unique spares requirements and the logistics footprint. In addition to reduced flyaway costs, the F-35 is designed to affordably integrate new technology during its entire life cycle. While each of the three models looks very similar externally, subtle differences accommodate a relatively wide range of operational needs. All of the three variants fly at supersonic speeds and shoot air-to-air missiles and drop bombs on a target. But they all have vastly different operational suitability requirements. Simply put, the F-35A variant must be affordable, stealthy and match or better the performance characteristics of an F-16. F-35B adds to these characteristics a short-takeoff/vertical landing capability. The F-35C variant must be suitable for carrier operations and must complement the F/A-18E/F.

All models of the Lockheed Martin design look essentially alike, with common outer mold lines across the fuselage and wingbox. They have common structural geometries, share identical wing sweeps and similar tail shapes, and carry weapons in two parallel bays located in front of the main landing gear. Major portions of the fuselage contain common or closely related parts, referred to as cousin parts. The canopy, radar, ejection system, subsystems and most of the avionics are currently common.

The Lockheed Martin design also uses unitized structures to simplify manufacturing and reduce cost. Unitized structures are portions of the aircraft that can be produced as single parts instead of being assembled by hand from a multitude of pieces and hundreds of fasteners. The canopy frame, for example, is fabricated from a single aluminum casting with no fasteners. By comparison, the F-16 canopy frame has 48 parts, 70 shims, and about 500 fasteners.

The JSF's inlet duct is another example. It consists of only three parts fabricated from composite fibers. Each piece of the duct, itself a complex shape, is created by a computer-controlled machine that accurately places composite fibers on a mandrel that then goes into an autoclave for curing. The process, called fiber placement, reduces the time and material associated with laying up complex composite shapes by hand. The company will apply other composite experience gained through its work on the F-22 program and the Japan FS-X program.

The fighter's forward fuselage is another assembly that uses unitized structures. It consists of a unitized aluminium canopy sill, a one-piece cast titanium nose landing gear bay, two resin transfer-molded cockpit side panels, and several large fiberplaced skins and panels. This design approach reduces parts by more than 30 percent and fasteners by about a quarter compared with the F-16 forward fuselage.

Bulkheads provide a good example of manufacturing commonality. Slight variations in thickness or shape, possibly a different material, might be needed to handle different load conditions for each service variant. These variations can be accommodated through common locating points and surfaces, tooling accessories and spacers, and visual work instructions. Moreover, numerically controlled machining can efficiently incorporate these slight variations with very little additional machine programming.


Once the Transfer of Technology [TOT] issues are sorted out, the JSF program would be the finest example of large scale International collaboration undertaken to achieve a common objective.

The F-35 Lightning II, that is being developed as part of the Joint Strike Fighter [JSF] program ushers in a new era in the field of Aircraft design and development and will completely change the face of any future conflict.


Saturday, May 03, 2008

F-35 Joint Strike fighter Program: An Overview 03

Read the earlier parts: Part 1, Part 2

Weapons Integration:

The F-35 is being designed to be able to carry a wide array of weapon to accomplish various types of missions. These weapons can be carried either internally or externally. The internal weapon bays significantly reduce the Aircraft’s radar signature.

F-35 Joint Strike Fighter [J.S.F]

When stealth features are not needed, the F-35 is also provided with external hard-points to be able to carry ordnance externally, significantly increasing its payload capacity. The F-35’s weapon bay can accommodate a wide array of ordnance that can be easily loaded by the ground crew. The F-35 can carry up to 6 Tons of payload during each sortie.


Autonomic Logistics (AL):

Autonomic Logistics (AL) is a seamless, embedded solution that integrates current performance, operational parameters, current configuration, scheduled upgrades and maintenance, component history, predictive diagnostics (prognostics) and health management, and service support for the F-35. Essentially, AL does invaluable and efficient behind-the-scenes monitoring, maintenance and prognostics to support the aircraft and ensure its continued good health.

The autonomic logistics system, as the F-35 system is called, will monitor the health of the aircraft systems in flight; downlink that information to the ground; and trigger personnel, equipment, and parts to be pre-positioned for quick turnaround of the aircraft. Ultimately, this automated approach will result in higher sortie-generation rates. Through a system called prognostics and health management, computers use accumulated data to keep track of when a part is predicted to fail. With this aid, maintainers can fix or replace a part before it fails and keep the aircraft ready to fly. Like the rest of the program, the autonomic logistics system is on a fast track. It has to be available to support the air vehicle during operational test and evaluation.

Propulsion System:

The propulsion systems to be used on the F-35 are the most powerful turbofans to be used in a fighter aircraft. Two different, but interchangeable systems are being developed – the F135, by Pratt & Whitney [P&W] and the F136, by a team formed by General Electric and Rolls-Royce. Both the F135 and F136 will use common exhaust and Lift systems. Two major variants of the engine are being developed by both the design teams – one variant would power the CTOL [F-35A] and CV [F-35C], whereas the other variant would be equipping the STOVL [F-35B].

The F135 engine consists of a 3-stage fan, a 6-stage compressor, an annular combustor, a single stage high-pressure turbine, and a 2 stage low-pressure turbine. P&W is using cutting-edge technology to provide the F-35 with higher performance than conventional fighter aircraft.

The F136 engine consists of a 3-stage fan, 5-stage compressor, a 3-stage low-pressure turbine section and a single stage high-pressure turbine.

Engine Characteristics

Conventional Take Off and Landing /Carrier Variant

CTOL /CV Engine Design

Maximum Thrust


Intermediate Thrust



5.59 meters

Inlet diameter

1.17 meters

Maximum Diameter

1.30 meters

Bypass ratio


Overall pressure ratio


Short Take Off and Vertical Landing

STOVL Propulsion System Design

Maximum Thrust


Short Takeoff Thrust


Hover Thrust


Main Engine


Lift Fan


Roll Post



9.37 meters

Inlet Diameter

Main Engine

1.17 meters

Lift Fan

1.27 meters

Maximum diameter

1.3 meters

Bypass Ratio



Powered Lift


Overall Pressure Ratio



Powered Lift


Short Takeoff and Vertical Landing [STOVL]

The propulsion system of the F-35B variant of the aircraft is truly ground-breaking as it is going to be equipped with STOVL capabilities, making it the first operational STOVL-capable aircraft in the world that is also supersonic in cruise. The other existing STOVL-capable aircraft, the Harrier can only fly at sub-sonic cruise speeds, making it extremely vulnerable to attacks from enemy fire.

F-35 Joint Strike Fighter (J.S.F)

The path that Lockheed Martin has taken to achieve the STOVL capabilities is also quite revolutionary. Unlike the vectored-thrust approach taken by the Harrier, the F-35B would be fitted with a vertically-orientated Lift Fan system developed and patented by Lockheed Martin. The Lift Fan would be powered by a 2-stage low pressure turbine on the engine. The Lift Fan would generate a column of cool air that would generate thrust of nearly 89kN using variable inlet guide vanes to modulate the air flow and therefore the thrust. During STOVL operations, the Lift Fan engages the Engine by means of a shaft and clutch arrangement and a "D"-shaped nozzle provides the thrust deflection. The D nozzle consists of four sections with the final part containing fixed vanes. The Lift Fan is capable of supporting nearly half the weight of the Aircraft. A unique feature of the Engine design is the Auxiliary inlet for the engine provided above the fuselage behind the Lift Fan that provides the extra air required for inducing hover conditions.

A three-bearing swivel nozzle [3BSN] can deflect the thrust from the engine exhaust from the conventional horizontal direction to just forward of vertical, thus providing additional downward thrust to support the Aircraft during its vertical movement. Two Roll nozzles provided by the sides of the engine perform the task of Roll control. Yaw control is achieved by swivel nozzle yaw. Pitch control is affected via Lift Fan/engine thrust split.

F-35 Joint Strike Fighter (J.S.F)

While operating in short take-off mode, the Lift Fan inlet and the exhaust doors open and inlet guide vanes close down to minimise air flow and the clutch is engaged. As clutch plates synchronise, the Lift Fan gear drive accelerates and is brought to input speed. The inlet guide vanes are then opened to bring the Lift Fan up to speed and the D nozzle is rotated down to vector the Lift Fan thrust aft; with the main engine thrust, this helps accelerate the aircraft forward and upward. After transitioning to wing-borne flight, the inlet guide vanes are again closed down to reduce the air flow through the Lift Fan, the clutch is disengaged, the nozzle is retracted, and the inlet and exhaust doors are closed.

While operating in vertical landing mode, the aircraft decelerates and the Lift Fan inlet and exhaust doors open. The Lift fan is brought up to speed as described above, but the D nozzle is left retracted to its fully vertical position. The clutch is designed to engage in 3-7 seconds. A mechanical lock-up device then ensures that the clutch does not slip once the Lift Fan is fully engaged. The clutch plate absorbs energy during engagement and dissipates it using cooling air before its next engagement.

Simple configuration changes enable the conversion of the F136 from a CTOL/CV to a STOVL engine. Engine controls and software will differ among the various configurations. For the STOVL variant, the fan duct incorporates a bypass offtake system for aircraft roll control. A shaft is attached to the engine's low-pressure rotor. The axisymmetric nozzle is replaced with the 3BSN.

The Lift Fan approach to STOVL has four distinct advantages: -

  • The Lift Fan thrust can be de-coupled from the aircraft engine during horizontal cruise, thereby enabling the availability of full power of the engine to the cruise.

  • The amount of thrust produced by the Lift Fan system greatly exceeded the additional weight of the system.

  • The Lift Fan produced a downward thrust of cool air that mixed with the hot exhaust gases directed by the 3BSN, thereby significantly lowering exhaust temperature and hence creating more benign ground environment during hover.

  • The oxygen-depleted hot exhaust from the Harrier’s exhaust nozzles often entered the main inlet of the aircraft, thereby cutting oxygen supply to the engine and causing great operational difficulties. The downward-acting cool air column created by the Lift Fan greatly mitigates this problem.

When not carrying any onboard ordnance, the downward thrusts produced by the aircraft’s propulsion system is enough to lift off the ground and then switch to cruise mode [horizontal travel].

Read the remaining part: Part 4