IAF Group C cheat sheet

Number series: check successive differences first, then ratios; if neither works, test alternating sub-series (odd positions and even positions separately) and squares/cubes plus a constant.

Alphabet positions: A=1 to Z=26; reverse position = 27 minus forward position, so A pairs with Z, B with Y, and so on.

Coding-decoding: write the alphabet with positions above each letter before decoding; most letter-shift codes use a fixed offset or a reversal plus offset.

Blood relations: draw a tree, not prose; use + for male and − for female, horizontal line for siblings, vertical line for parent-child, and double line for marriage.

Direction sense: fix north up and use Pythagoras for shortest distance; left/right turns reverse meaning when the person faces south.

Syllogism: a conclusion is valid only if it holds in every possible Venn diagram of the premises; 'some A are B' does not imply 'some B are not A'.

Seating arrangement: place fixed-position clues first, then relative clues; for circular arrangements facing the centre, left means clockwise.

Analogy and classification: identify the relation type (part-whole, cause-effect, worker-tool, synonym) before choosing the option.

Series of figures: track one element at a time - rotation (usually 90° clockwise), number of sides, shading alternation, and position swap.

Percentage change: successive changes of a% and b% give a net change of a + b + ab/100 percent; a 20% rise then 20% fall leaves a 4% net fall.

Profit and loss: profit% is always on cost price unless stated; selling price = CP × (100 + profit%)/100; discount is always on marked price.

Simple interest = PRT/100; compound interest = P[(1 + R/100)^T − 1]; for two years the CI − SI difference equals P(R/100)².

Time and work: if A alone takes a days and B alone b days, together they take ab/(a + b) days; use LCM of days as total work units.

Speed: distance = speed × time; km/h to m/s multiply by 5/18; for equal distances at speeds x and y, average speed = 2xy/(x + y).

Boats: downstream speed = boat + stream, upstream = boat − stream; boat speed = (down + up)/2, stream speed = (down − up)/2.

Averages: new average after adding a value = (old sum + value)/(n + 1); in an arithmetic progression the average equals the middle term.

Ratio and mixtures: in an alloy of A and B, quantity of A = total × A/(A + B); repeated replacement leaves original × (1 − removed/total)^n.

Mensuration: circle area πr², circumference 2πr; sphere volume 4/3πr³, surface 4πr²; cylinder volume πr²h, curved surface 2πrh; cone volume 1/3πr²h.

Subject-verb agreement: 'one of the + plural noun' takes a singular verb; 'each, every, either, neither' take singular verbs.

Articles: 'a' before consonant sounds, 'an' before vowel sounds (an hour, a university); 'the' with superlatives, unique objects, and rivers.

Prepositions of time: at for clock times, on for days and dates, in for months, years, and long periods.

Tenses: since/for with present perfect or present perfect continuous; 'had + past participle' marks the earlier of two past actions.

Active to passive: object becomes subject, verb becomes be + past participle, and the agent is introduced by 'by'.

Direct to indirect speech: present tense shifts to past, 'this' to 'that', 'today' to 'that day', 'tomorrow' to 'the next day'.

Common confusions: affect (verb) vs effect (noun); lie/lay; its (possessive) vs it's (it is); principal (head) vs principle (rule).

Idioms: 'a bolt from the blue' means a sudden shock; 'to beat about the bush' means to avoid the main point; 'once in a blue moon' means very rarely.

One-word substitutions: 'altruist' is a person who lives for others; 'philanthropist' donates to good causes; 'misanthrope' dislikes mankind.

Indian Constitution: adopted 26 November 1949, came into force 26 January 1950; the Preamble was amended by the 42nd Amendment (1976), which added socialist, secular, and integrity.

Fundamental Rights sit in Part III (Articles 12–35); the Right to Constitutional Remedies (Article 32) was called the heart and soul of the Constitution by Dr B. R. Ambedkar.

Indian Parliament: Lok Sabha maximum strength 552, Rajya Sabha 250; money bills can be introduced only in the Lok Sabha.

Indian geography: the Tropic of Cancer passes through eight states; the Deccan Plateau lies between the Western and Eastern Ghats; the Sundarbans is the world's largest mangrove forest.

Indian economy: RBI was nationalised in 1949 and is headquartered in Mumbai; NABARD is the apex body for rural credit; SEBI regulates securities markets.

Indian defence: the Indian Air Force was established in 1932 and is commanded by the Chief of the Air Staff; the President is the supreme commander of the armed forces.

Space and atomic milestones: Aryabhata was India's first satellite (1975); Chandrayaan-3 landed near the lunar south pole in 2023; Pokhran-II tests were in 1998.

International bodies: the UN was founded in 1945 with headquarters in New York; the WHO is in Geneva; the IAEA is in Vienna; the SAARC secretariat is in Kathmandu.

Aircraft maintenance is grouped into line maintenance (pre-flight, turnaround, daily checks) and base maintenance (heavy C and D checks in a hangar).

Airworthiness: a Certificate of Airworthiness must be supported by continuing airworthiness records, and any defect affecting safety is entered in the technical log before the next flight.

Aircraft hardware: AN and MS bolts are identified by dash numbers giving diameter and length; a cotter pin secures a castellated nut; safety wire is twisted clockwise in a pull direction that tightens the nut.

Aircraft controls: ailerons control roll, elevators control pitch, the rudder controls yaw; the three axes are longitudinal (roll), lateral (pitch), and vertical (yaw).

Jet engine basics: the Brayton cycle describes the gas turbine; compression, combustion, and exhaust stages; bypass ratio distinguishes turbofan from turbojet engines.

Hydraulic systems: Pascal's law means pressure is transmitted equally; typical aircraft hydraulic fluid is MIL-PRF-5606 (red) or Skydrol (phosphate-ester, purple).

Torque and measurement: a torque wrench must be calibrated and set to the value in the maintenance manual; micrometers read to 0.01 mm and vernier callipers to 0.02 mm.

Corrosion control: galvanic corrosion needs two dissimilar metals and an electrolyte; treatment includes cleaning, alodine conversion coating, and primer.

Electrical safety: the aircraft battery is disconnected before electrical work; use a bonding lead to avoid static discharge when refuelling.

Hardware and memory: 1 byte = 8 bits; 1 KB = 1024 bytes; RAM is volatile working memory, ROM is non-volatile firmware storage.

Shortcut keys: Ctrl+C copy, Ctrl+V paste, Ctrl+X cut, Ctrl+Z undo, Ctrl+Y redo, Ctrl+S save, Ctrl+P print, Ctrl+F find, Alt+F4 close window.

MS Word: Ctrl+E centres, Ctrl+J justifies, Ctrl+B bold; page setup controls margins, orientation, and paper size; mail merge links a main document to a data source.

MS Excel: every formula starts with '='; $A$1 is an absolute reference; =SUM(A1:A10) totals a range; VLOOKUP searches the first column of a range.

Computer networks: IP address identifies a device; HTTP/HTTPS handles web pages; SMTP sends email and POP3/IMAP retrieves it; a firewall filters traffic.

File management: extensions identify file type (.docx, .xlsx, .pptx, .pdf); a folder can nest subfolders; the Recycle Bin holds deleted files until purged.

Office procedure: inward mail is diarised and put up through proper channel; draft replies carry file number and date; confidential papers are handled under a separate confidential register.

Record keeping: files are classified as current, semi-current, and non-current; retention schedules decide destruction, and a destruction certificate is preserved.

Clock problems: the minute hand gains 5.5° per minute on the hour hand; hands coincide 11 times in 12 hours and are opposite 11 times in 12 hours.

Calendar: an ordinary year has 1 odd day, a leap year 2; a century year is a leap year only if divisible by 400.

Cube and dice: on a standard die opposite faces sum to 7; for a painted cube cut into n³ small cubes, corner cubes are 8 and edge cubes are 12(n − 2).

Ranking: if a person is r-th from the left in a row of n, the rank from the right is n − r + 1.

Statement and assumption: an assumption is what the speaker must have taken for granted, not what is stated; reject options that restate the statement.

Coding by position: in a word code, letters may be replaced by their reverse alphabet position, so CAT becomes 24-26-7.

Mirror and water images: a mirror reverses left and right while keeping top and bottom; a water image reverses top and bottom.

Data sufficiency: decide whether the data in the statements is enough to answer the question, not what the answer is.

Partnership: profit shares are proportional to capital × time; if capitals are equal, shares are in the ratio of periods.

Permutation and combination: nPr = n!/(n − r)! and nCr = n!/[r!(n − r)!]; arrangements of a word with repeated letters divide by factorials of repeats.

Probability: P(A or B) = P(A) + P(B) − P(A and B); for independent events P(A and B) = P(A) × P(B).

Number system: any number is divisible by 3 or 9 if the sum of digits is; by 4 if the last two digits are; by 11 if the alternating digit sum difference is a multiple of 11.

HCF and LCM: HCF × LCM = product of the two numbers; LCM of fractions = LCM of numerators / HCF of denominators.

Pipes and cisterns: a filling pipe adds 1/t per hour, a draining pipe subtracts; net rate gives total time, and a negative result means the tank never fills.

Simple interest doubling: a sum doubles in T years at R% simple interest when R × T = 100.

Percentage to fraction: 12.5% = 1/8, 16.66% = 1/6, 33.33% = 1/3, 66.66% = 2/3, 6.25% = 1/16; convert to fractions to simplify calculations.

Geometry: sum of interior angles of an n-gon = (n − 2) × 180°; in a triangle the exterior angle equals the sum of the two opposite interior angles.

Cloze test: read the whole passage first, then choose the option that fits both grammar and meaning; eliminate options that repeat a word already nearby.

Error spotting: check for double comparatives ('more better'), double negatives ('didn't do nothing'), and missing articles before singular countable nouns.

Synonyms and antonyms: use the word in a sentence before choosing; 'candid' means frank, its antonym is evasive; 'frugal' means thrifty, its antonym is extravagant.

Sentence improvement: prefer the option that is grammatically correct and concise; avoid changing the meaning of the original.

Active to passive with modals: 'can do' becomes 'can be done'; 'must finish' becomes 'must be finished'.

Conditional sentences: first conditional uses present + will; second conditional uses past + would; third conditional uses had + past participle + would have.

Punctuation: a semicolon joins two independent clauses; a colon introduces a list or explanation; the apostrophe shows possession or contraction.

Antonym pairs: 'obscure' vs 'clear', 'benevolent' vs 'malevolent', 'transient' vs 'permanent', 'augment' vs 'diminish'.

Indian history: the Battle of Plassey was in 1757, the Indian National Congress was founded in 1885, and India gained independence on 15 August 1947.

Indian defence forces: the Indian Army is the largest service, the Navy's flagship aircraft carrier is INS Vikrant (commissioned 2022), and the IAF's Rafale entered service in 2020.

Indian states: Rajasthan is the largest state by area and Uttar Pradesh the most populous; the largest state by area in the northeast is Arunachal Pradesh.

Indian rivers: the Ganga is the longest river wholly within India; the Brahmaputra is called the Tsangpo in Tibet; the Godavari is the longest peninsular river.

Indian economy: the rupee symbol was adopted in 2010; GST was introduced on 1 July 2017; the Reserve Bank of India was established in 1935.

World geography: the longest river is the Nile, the largest ocean the Pacific, the highest peak Mount Everest, and the largest desert the Sahara (hot desert).

Nobel and international awards: the Nobel Prizes were first awarded in 1901; the Bharat Ratna is India's highest civilian award, instituted in 1954.

Science basics: the SI unit of force is the newton, of pressure the pascal, of power the watt; the speed of light is about 3 × 10⁸ m/s.

Aircraft structures: the fuselage carries the payload and transmits loads to the wings; stringers and frames stiffen the skin; a semimonocoque structure uses skin plus longerons.

Landing gear: oleo struts absorb landing loads through compressed air or nitrogen plus hydraulic fluid; shimmy dampers prevent nose-wheel oscillation.

Flight instruments: the altimeter uses static pressure, the airspeed indicator uses pitot and static pressure, and the vertical speed indicator uses static pressure changes.

Avionics: a pitot-static leak causes airspeed errors; the attitude indicator is a gyroscopic instrument and must be erected before flight.

Fuel systems: AVGAS 100LL is used in piston engines; Jet A-1 is standard for turbine engines; water in fuel is removed by sump drains during pre-flight.

Fire safety: a fire needs fuel, oxygen, and heat; a halon or dry powder extinguisher is used for electrical and fuel fires, never water.

Maintenance documentation: the Aircraft Maintenance Manual gives procedures, the Illustrated Parts Catalogue gives part numbers, and the Service Bulletin gives mandatory or recommended changes.

Human factors: the 'dirty dozen' includes fatigue, complacency, and pressure; the SHEL model covers software, hardware, environment, and liveware.

Unit conversions: 1 inch = 25.4 mm, 1 lb = 0.4536 kg, 1 nautical mile = 1.852 km, 1 psi ≈ 6.895 kPa.

MS PowerPoint: F5 starts the slide show, Shift+F5 starts from the current slide; slide master controls the overall design of all slides.

MS Excel functions: =AVERAGE(range), =COUNT(range), =MAX(range), =MIN(range), =IF(condition, true, false), =CONCATENATE or =TEXTJOIN for text joining.

Email etiquette: use the To field for action takers, Cc for information, Bcc for hidden recipients; avoid opening unknown attachments.

Computer generations: first generation used vacuum tubes, second transistors, third integrated circuits, fourth microprocessors, fifth artificial intelligence.

Operating system tasks: file allocation, memory management, process scheduling, and device drivers; Windows, Linux, and macOS are common desktop systems.

Office procedure: a receipt is acknowledged with a docket number; a reminder is sent after the due date; a 'U.O. note' (unofficial note) is used for quick inter-departmental reference.

Security: a strong password mixes upper and lower case, digits, and symbols; two-factor authentication adds a second verification step; antivirus software must be updated regularly.

Printing and storage: a laser printer uses toner and a drum, an inkjet uses liquid ink; SSD has no moving parts and is faster than HDD.

Word arrangement: to arrange words in dictionary order, compare letter by letter from the left and pick the earliest differing letter.

Matrix reasoning: read rows and columns independently; a missing cell usually follows the same arithmetic pattern along both its row and its column.

Inequality: 'A > B ≥ C' means A > C; combining 'P ≤ Q < R' gives P < R; a conclusion is false if it contradicts the chain.

Input-output: track the change step by step; typical operations are sorting words alphabetically and numbers ascending, one element fixed per step.

Puzzle with ages: convert statements into equations ('A is twice B' means A = 2B) and solve; check that the answer satisfies every condition.

Venn diagram counting: n(A ∪ B) = n(A) + n(B) − n(A ∩ B); for three sets subtract pairwise intersections and add the triple intersection back.

Odd one out in numbers: test divisibility, prime/composite status, perfect squares, and digit sums before choosing.

Series with two operations: alternate +n and ×m; write the differences and ratios in two rows to spot the pattern.

Trains: time to cross a pole = train length / speed; time to cross a platform = (train length + platform length) / speed; for opposite directions add speeds.

Simple and compound interest relation: for 2 years, CI = SI + SI × R/200; the difference grows with the square of the rate.

Allegation rule: when two quantities with values a and b are mixed to give mean m, the ratio is (m − b) : (a − m).

Area of a triangle: ½ × base × height; Heron's formula uses s = (a + b + c)/2 and area = √[s(s − a)(s − b)(s − c)].

Work and wages: wages are shared in the ratio of work done, which equals the ratio of 1/time for each worker.

Percentage of percentage: x% of y equals y% of x; to increase a number by p% multiply by (100 + p)/100.

Clocks and calendars in arithmetic: angle between hands = |30H − 5.5M| degrees, where H is the hour and M the minute.

Data interpretation: compute the required ratio or percentage directly from the table; avoid calculating totals you do not need.

Phrasal verbs: 'put off' postpones, 'put up with' tolerates, 'call off' cancels, 'look into' investigates, 'give in' surrenders.

Collective nouns: a fleet of ships, a flock of sheep, a herd of cattle, a swarm of bees, a bunch of keys, a bouquet of flowers.

Degrees of comparison: use 'than' with comparatives and 'the' with superlatives; 'senior, junior, superior, inferior' take 'to', not 'than'.

Reported questions: 'He asked me where I lived' - no question mark, and word order becomes statement order.

Common idioms: 'to turn a deaf ear' means to ignore; 'to make both ends meet' means to live within one's means; 'a white elephant' means a costly, useless possession.

Spelling rules: drop the final 'e' before a vowel suffix (make → making); change 'y' to 'i' after a consonant (carry → carried).

Sentence connectors: 'although' contrasts, 'therefore' shows result, 'moreover' adds, 'nevertheless' concedes.

Antonyms: 'hostile' vs 'friendly', 'rigid' vs 'flexible', 'scarce' vs 'abundant', 'concise' vs 'verbose'.

Indian polity: the President is elected by an electoral college; the Vice-President is the ex-officio Chairman of the Rajya Sabha; the Prime Minister heads the Council of Ministers.

Judiciary: the Supreme Court was established on 26 January 1950; High Court judges are appointed by the President; the writ of habeas corpus protects personal liberty.

Indian geography: the Western Ghats are older than the Himalayas; the Thar Desert lies in Rajasthan; Kanchenjunga is the highest peak in India.

Indian culture: the Ajanta caves are Buddhist, Ellora has Hindu, Buddhist, and Jain caves; Kathakali is from Kerala and Bharatanatyam from Tamil Nadu.

World organisations: NATO headquarters in Brussels, OPEC in Vienna, the World Bank in Washington DC, UNESCO in Paris.

Indian economy: the Green Revolution is associated with M. S. Swaminathan; the White Revolution with Verghese Kurien; the Blue Revolution with fish production.

Sports: the Ranji Trophy is for cricket, the Santosh Trophy for football, the Duleep Trophy for cricket, and the Thomas Cup for badminton.

Science: photosynthesis converts carbon dioxide and water into glucose and oxygen using chlorophyll; the pH of pure water is 7.

Aircraft materials: aluminium alloys (2024, 7075) are common for structure; titanium is used in hot engine sections; composites use carbon fibre in an epoxy matrix.

Rivets: the universal head rivet is the most common; rivet pitch should be about 3 times the diameter; a bucked rivet must fill the hole and have a proper shop head.

Engine checks: a compressor wash removes salt and dirt; an oil analysis detects wear metals; borescope inspection checks turbine blades without disassembly.

Navigation: VOR gives bearing, DME gives distance, ILS gives lateral and vertical guidance for landing, and GPS gives position in three dimensions.

Weather for aviation: a cumulonimbus cloud signals turbulence and icing risk; fog reduces visibility below minima and is reported in METAR as 'FG'.

Quality control: the '5S' method covers sort, set in order, shine, standardise, and sustain; a 'red tag' area holds unserviceable items.

Safety equipment: a CO₂ extinguisher is for electrical fires, a dry powder extinguisher for fuel fires, and a fire blanket for clothing fires.

Basic electricity: Ohm's law V = IR; power P = VI = I²R; a series circuit has one current path, a parallel circuit shares the voltage.

Input and output devices: keyboard, mouse, and scanner are input; monitor, printer, and speaker are output; a touchscreen is both.

MS Word features: track changes records edits, comments annotate without changing text, and 'Compare' shows differences between two documents.

MS Excel: Ctrl+; inserts today's date; =TODAY() returns the current date; freeze panes keeps headings visible while scrolling.

Computer security terms: malware is malicious software, phishing tricks users into revealing credentials, ransomware encrypts files for payment.

Internet basics: a URL has protocol, domain, and path; a browser caches pages for speed; cookies store session data.

Office filing: the 'first letter' or alphabetical method is simplest; the 'subject' method groups by topic; a movement register tracks file issue and return.

Drafting notes: a 'note for approval' states the proposal, justification, and financial implication; the 'fair copy' is the final typed version for signature.

Backup practice: the 3-2-1 rule means three copies, on two media, with one off-site; verify restore, not just backup.