3.4
title: Section 3.4: Picking the Perfect Spot - Site Selection Deep Dive¶
Exam Alert: ⭐⭐⭐⭐⭐ SUPER HIGH - This is THE question. Almost every year they ask "Explain factors for site selection" or "Elaborate on site selection parameters." Easy 13 marks if you know this!
The Core Principle: It's Like Buying a House, But for Planes¶
Look, here's the deal - selecting an airport site is basically like buying a house, except your "guests" are giant metal birds that need LOTS of space, hate obstacles, and make a ton of noise. Nobody gets everything perfect, so you pick the spot that checks the most boxes and costs the least. That's it!
Memory Trick - Primary Importance:
Picture yourself as a pilot coming in to land. What do you NEED?
- Space to land (duh!)
- Easy access from the city (or why bother?)
- Flat-ish ground (bumpy = bad)
- Clear approaches (no mountains in your face)
- Cheap enough to actually build
Everything else just flows from these basics. Now let's break it down:
1. AVAILABILITY OF ADEQUATE AREA¶
The "ah, this is easy" explanation: You need BIG land. Not just for today's tiny airport, but for when it grows into a monster. Think of it like buying pants - buy them bigger now, or regret it later when you can't expand.
Why it matters: Once your airport starts operating, the land around it becomes EXPENSIVE (everyone wants to build hotels, parking, businesses near airports). If you didn't buy enough land initially, you're screwed. You can't just shift an airport like you move a bus stop!
What you actually write in exam:
- "Initial land acquisition (buying property) must account for future expansion"
- "Post-operational land acquisition becomes economically prohibitive (crazy expensive)"
- "Prevents need for airport relocation (moving the whole thing)"
Real example:* Delhi's IGI airport - they grabbed HUGE land initially. Good thing, because now it handles 60+ million passengers. If they'd been stingy, they'd be rebuilding somewhere else by now.
2. ACCESSIBILITY¶
The "ah, this is easy" explanation: Airports have a Goldilocks problem - too close to the city = noise complaints and tall buildings in the way. Too far = nobody wants to fly because the drive kills them. Need it just right.
The paradox you need to understand: * Noise nuisance (loud aircraft sounds) needs distance from residential areas (where people live) * Obstruction-free zone (clear space for takeoff/landing) needs empty land * But - if it takes 3 hours to reach the airport, people will just take a train!
What you actually write in exam: * "Located away from built-up areas (developed city zones) to minimize noise impact" * "Balanced distance - must not negate time-saving advantage of air travel" * "Connected by highway/expressway (fast roads) for ground access"
Real example: Bangalore's Kempegowda Airport is 40km from the city. Far enough? Yes, for noise. Too far? Many locals complain about the 1.5-hour drive! That's the trade-off.
3. TOPOGRAPHY, SOIL CONDITION AND DRAINAGE¶
The "ah, this is easy" explanation: You need: mostly flat land that doesn't turn into a swimming pool when it rains, with soil that won't collapse under heavy planes.
Three sub-factors here:
a) Topography (shape/slope of land):¶
- Slopes over 1% = too much grading (cutting/filling earth) = expensive
- Elevated sites > Valley sites because:
- Better drainage (water flows away naturally)
- Better visibility (you can see approaching planes)
- Valley = less grading needed BUT worse drainage
b) Soil condition:¶
- Need strong soil to support heavy aircraft (A380 weighs 560 tons!)
- Weak soil = do soil stabilization (mixing chemicals/cement to strengthen soil) = extra cost
- Water table (underground water level) position matters - too high = soggy runways
c) Drainage:¶
- Area must be self-draining (naturally slopes so water leaves)
- Must NOT flood from neighboring areas
- Need outlets to send water away
What you actually write in exam: * "Ground slopes exceeding 1% result in excessive earthwork (digging/filling)" * "Elevated sites provide superior drainage and visibility compared to valleys" * "Sub-soil investigation (testing underground) determines pavement design" * "Natural drainage pattern (how water flows) must be assessed"
4. AVAILABILITY OF CONSTRUCTION MATERIAL¶
The "ah, this is easy" explanation: Building an airport needs MASSIVE amounts of rocks, sand, and aggregates (crushed stones). If you have to truck these from 200km away, your budget explodes.
What you need: * Stone for pavement base layers * Sand for concrete and asphalt * Aggregates (crushed stones) for everything
The money reality: Transportation cost often EXCEEDS the material cost! Getting rocks from 5km away vs. 50km away can double your budget.
What you actually write in exam: * "Proximity to stone quarries (rock sources) reduces construction costs" * "Transportation costs may exceed material procurement (buying) costs" * "Natural construction materials availability influences project economics"
5. COST OF DEVELOPMENT¶
The "ah, this is easy" explanation: Money, money, money! How much will this whole thing cost? Three big chunks:
a) Land Acquisition Cost:¶
- Buy ALL the land you'll EVER need RIGHT NOW
- Land prices skyrocket once the airport is announced
- Pro tip for exam: Mention "appreciation of land values post-announcement prevents economical future expansion"
b) Construction Cost:¶
- Runways (long concrete strips)
- Taxiways (plane roads)
- Terminal buildings (where passengers hang out)
- Depends heavily on soil quality and topography
c) Utilities Cost:¶
Electric power, water supply, sewerage (waste disposal): * Near city? Connect to city systems (but size them for FUTURE needs!) * Far from city? Independent systems may be cheaper * Always need backup power - airports can't just "go dark"
What you actually write in exam: * "Phased land acquisition (buying in stages) proves more expensive due to price escalation (increase)" * "Initial infrastructure sizing (planning capacity) must accommodate ultimate development" * "Stand-by power generation essential regardless of grid connectivity (city power connection)"
6. COST OF MAINTENANCE¶
The "ah, this is easy" explanation: Building it is one thing, keeping it running is another. Forever costs!
What needs maintenance: * Pavements (runways/taxiways) - resurfacing (new top layer) every few years * Buildings - repairs, painting, AC systems * Utilities - power, water, sewage treatment plants * Control systems - air traffic control (ATC) equipment, radar (aircraft detection)
What you actually write in exam: * "Annual maintenance costs include pavement rehabilitation, building upkeep, and utility operation" * "Control system maintenance critical for operational safety"
7. TRAFFIC VOLUME AND TYPE OF TRAFFIC¶
The "ah, this is easy" explanation: How many planes? What kind? Big international jets or small domestic props?
For existing airports: Study current traffic and project (predict) growth.
For new airports: Look at neighboring airports for guidance.
Why it matters: * More traffic = longer runways, more taxiways, bigger terminals * International flights = customs, immigration (border control) facilities * Cargo traffic = different infrastructure than passenger traffic
What you actually write in exam: * "Traffic forecast (prediction) determines airport classification and capacity requirements" * "Study of adjacent airport operations (neighboring airports) provides planning insights" * "Passenger vs. cargo composition (mix) influences terminal design"
8. CROSS-WIND COMPONENT¶
The "ah, this is easy" explanation: Planes HATE side winds (wind hitting from the side). The runway direction should align with the PREVAILING WIND (most common wind direction).
The magic: If wind usually blows North-South, build your runway North-South. Then planes always takeoff/land INTO the wind (headwind = lifting wind from front), which: * Needs LESS runway length (shorter takeoff) * Safer landing (natural braking)
The angle rule: Ideally, keep runway within 30° of the most common wind direction.
What you actually write in exam: * "Runway orientation (direction) aligned with prevailing winds reduces required runway length" * "Crosswind component (side wind force) must remain within permissible limits" * "Wind rose analysis (wind direction diagram) guides optimal runway alignment"
9. PROXIMITY TO AIRWAYS¶
The "ah, this is easy" explanation: Don't build airports RIGHT next to each other - they need separation for safety. But also, fill the gaps where NO airports exist.
The coordination: In India, the Director General of Civil Aviation (DGCA - the boss of all flying things) coordinates this. They make sure: * New airports serve UNSERVED areas * Or replace overloaded airports * Not too close to existing ones (traffic conflict)
Sometimes: Better to EXPAND an existing nearby airport than build a new one!
What you actually write in exam: * "Airports positioned to serve regions lacking air connectivity (flying access)" * "Director General Civil Aviation coordinates national airport network" * "Evaluation of existing airport capacity (handling ability) before new construction"
10. ATTITUDE OF PROPERTY OWNERS¶
The "ah, this is easy" explanation: If the local landowners HATE the idea and fight you in court for 10 years, maybe pick another spot!
The social reality: * Land acquisition (government taking private land) can be MESSY * Owners may demand huge compensation (payment) * Legal battles delay projects by years * Better to pick a site where people are cooperative (or at least not hostile)
What you actually write in exam: * "Community acceptance (local people's approval) facilitates smooth land acquisition" * "Opposition may result in legal impediments (court problems) and project delays" * "Initial stakeholder consultation (talking to affected people) recommended"
11. SAFETY FACTORS¶
The "ah, this is easy" explanation: Can planes see? Can they land safely? Are there mountains in the approach path (the route planes fly coming in)?
Three elements:
a) Visibility:¶
- No fog/smog issues?
- Clear sightlines for pilots?
b) Wind characteristics:¶
- Direction and intensity (strength) studied
- Turbulence (bumpy air) issues?
c) Freedom from obstructions:¶
- Approach zone (the area planes descend through) must be CLEAR
- No tall buildings, towers, mountains
- This is NON-NEGOTIABLE - safety first!
What you actually write in exam: * "Meteorological conditions (weather patterns) including visibility and wind assessed" * "Approach zones (landing paths) must remain obstruction-free" * "Safety considerations supersede (are more important than) economic factors"
12. AVAILABILITY OF NATURAL RESOURCES AND FACILITIES¶
The "ah, this is easy" explanation: Do you have rocks, water, and sewage pipes nearby? If yes, you save TONS of money.
Natural resources: * Stone (90% of airport construction is concrete/asphalt - which needs stone!) * Sand * Water (for construction, firefighting, toilets)
Existing facilities: * Sewer lines (waste pipes) for sewage disposal * Water mains (water pipes) for water supply * Being near these = plug and play!
What you actually write in exam: * "Stone and sand constitute 90% of airport construction material" * "Proximity to water sources and sewerage infrastructure reduces capital costs" * "Transportation costs often exceed material costs - proximity crucial"
13. REVENUE¶
The "ah, this is easy" explanation: How will this airport make money? Two buckets:
Aviation Activities (plane stuff):¶
- Landing fees (pay per landing)
- Hangar rents (plane parking/storage buildings)
- Airline accommodation (office space rental)
- Plane repair services
- Fuel sales (gas and oil)
Non-Aviation Activities (everything else):¶
- Telegraph/Telephone services
- Restaurants and bars (captive customers!)
- Automobile parking (major revenue!)
- Taxes from shops/businesses (duty-free stores make BANK)
The reality: Modern airports make MORE money from shopping and parking than from planes! Delhi airport's retail revenue exceeds aeronautical revenue.
What you actually write in exam: * "Revenue streams divided into aviation (flying-related) and non-aviation activities" * "Landing fees and hangar rentals constitute primary aviation revenue" * "Commercial establishments (shops) and parking generate significant non-aviation income"
THE SURVEYS - Now You Know WHAT, Here's HOW You Check¶
Once you've picked potential sites, you need to VERIFY everything. Six surveys:
Survey 1: TOPOGRAPHICAL¶
What it is: Making a detailed map with contour lines (lines showing elevation/height).
Why: To design runway alignment (direction), calculate earthwork (how much digging/filling), and plan drainage (water flow).
Output: Contoured map showing every bump and dip.
Survey 2: SOIL¶
What it is: Digging holes and testing dirt at different depths.
Methods (just name-drop these in exam): * Auger Borings (hand-drilled holes) * Wash Borings (water-assisted drilling) * Core Drilling (getting cylindrical samples) * Percussion Drilling (hammer-based) * Soundings (dropping weights to test resistance) * Test Pits (just dig a hole and look!)
Why: To know if the ground can support 560-ton aircraft! Also find water table (underground water level) position.
What if soil sucks? Do soil stabilization (strengthen it with cement/chemicals).
Survey 3: DRAINAGE¶
What it is: Study the contoured map to see: * Where water comes FROM (external drainage from surrounding areas) * Where water goes TO (outlets for discharge) * Risk of flooding
Why: Soggy runways = closed airport = angry passengers = lost money.
Design: Internal drainage (within airport) AND external drainage (preventing outside water from entering).
Survey 4: METEOROLOGICAL¶
What it is: Collect YEARS of weather data:
Data collected: 1. Wind: Direction, velocity (speed), duration 2. Rainfall: Amount and intensity (rate) 3. Atmospheric pressure: Affects aircraft performance 4. Fog/Frost/Snow: Visibility killers 5. Temperature: For runway length calculations
The star of the show: WIND ROSE DIAGRAM
This is a flower-shaped diagram showing: * Which direction wind blows FROM * How often (percentage of time) * How strong
Memory trick: The LONGEST petal on the wind rose = best runway direction!
Example: If wind blows North-South 60% of the time, build runway North-South. Simple!
What you write: * "Multi-year meteorological data compilation for wind rose preparation" * "Wind rose diagram determines optimal runway orientation" * "Atmospheric pressure data influences runway length calculations"
Survey 5: NATURAL RESOURCES¶
What it is: Find your rocks and water!
Scout for: * Stone quarries (rock sources) - location, quantity, quality, distance * Sand deposits * Water sources (rivers, lakes for construction water)
Why: Remember - transportation cost > material cost. A quarry 5km away vs. 50km away = HUGE money difference.
Survey 6: APPROACH ZONE¶
What it is: Extended topographical survey (map-making) in the direction of approaches (landing paths).
Purpose: Find and measure EVERY obstruction:
- Trees
- Buildings
- Towers
- Hills
- Power lines
Why: Planes descending at 3° angle need CLEAR path. A 50m tree 2km from runway might still be in the approach zone!
What you check: Height above ground of EVERY object in the approach cone (funnel-shaped area planes fly through).
EXAM STRATEGY - How to Score 13/13¶
When they ask: "Elaborate on factors for site selection"
Structure (5 minutes to write):
Introduction (1 line):
"Airport site selection involves evaluating multiple technical, economic, and operational parameters to identify the most suitable location."
Main body - List all 13 factors with 2-3 lines each:
- Adequate area (mention future expansion)
- Accessibility (noise vs. travel time trade-off)
- Topography/soil/drainage (mention 1% slope limit)
- Construction materials (transport cost point)
- Development cost (3 sub-costs)
- Maintenance cost (ongoing expenses)
- Traffic volume (existing/projected)
- Cross-wind (mention wind rose)
- Airways proximity (DGCA coordination)
- Property owners (social acceptance)
- Safety (visibility, obstructions)
- Natural resources (stone/water)
- Revenue (aviation + non-aviation)
When they ask about SURVEYS:
Just list all 6:
1. Topographical - contour maps for grading
2. Soil - bearing capacity via borings
3. Drainage - water management planning
4. Meteorological - wind rose for runway orientation
5. Natural resources - construction material sourcing
6. Approach zone - obstruction clearance verification
Bonus marks: Draw a simple wind rose diagram if time permits!
The ONE Sentence to Remember Everything¶
"AAAC-DMTT-PASS-RN" (weird, but works!)
But really, just remember: Space, Access, Ground, Money, Safety - everything else is just details under these 5 umbrellas!
You're ready! This section WILL appear in your exam. Master the 13 factors + 6 surveys = guaranteed 13 marks! 🎯