Civil Engineering · Airport Engineering
Airport Engineering — Assignment I, Fully Solved
Seventeen worked questions covering airport planning, aircraft anatomy, ICAO & FAA structure, runway orientation, and wind-rose analysis — with labelled diagrams and worked calculations.
Question 1
Defining Airport Engineering
Define Airport Engineering. Explain the major areas covered under Airport Engineering, including planning, design, construction, operation, maintenance, and management.
Airport Engineering is that branch of civil engineering which deals with the planning, design, construction, operation, maintenance, and management of airports and associated air-side and land-side facilities so that aircraft can land, take off, taxi, park, and be serviced safely, efficiently, and economically. It draws upon principles of transportation engineering, geotechnical engineering, structural engineering, hydrology, and traffic engineering, and applies them specifically to the unique requirements of aircraft operations.
Major Areas Covered under Airport Engineering
- Planning: Includes air-traffic forecasting, site selection, feasibility studies, and preparation of the Airport Master Plan that guides phased development of the airport over its design life (commonly 20 years).
- Design: Covers geometric design of runways, taxiways, and aprons (length, width, gradient, sight distance), pavement design (flexible and rigid pavements for the loads imposed by aircraft), and design of drainage, lighting, and navigational-aid systems.
- Construction: Involves earthwork, sub-grade preparation, pavement laying, drainage works, fencing, and installation of lighting, signage, and navigational aids in accordance with ICAO/FAA standards.
- Operation: Deals with air traffic control, ground handling, apron management, and coordination between the airport authority, airlines, and regulatory bodies to ensure safe day-to-day functioning.
- Maintenance: Covers upkeep of pavements (crack sealing, resurfacing), runway/taxiway markings, lighting systems, drainage channels, and safety areas to keep the facility serviceable.
- Management: Encompasses safety management systems (SMS), environmental management, capacity management, financial management, and long-term asset management of the airport.
Question 2
Air Transport vs. Other Modes
Explain the advantages and disadvantages of air transportation compared with other modes of transportation. Discuss why air transportation is particularly important for a mountainous country like Nepal.
Advantages of Air Transportation
- Highest speed among all modes of transport, drastically reducing travel time over long distances.
- No need for a continuous physical track or right-of-way as in roads or railways; only terminal (airport) infrastructure is required, so it can connect places separated by difficult terrain, rivers, or international boundaries.
- Best suited for carrying high-value, low-bulk, and perishable cargo, as well as for emergency and disaster-relief operations.
- Provides access to remote and otherwise inaccessible regions where road or rail construction is technically difficult or uneconomical.
Disadvantages of Air Transportation
- Very high initial investment and operating cost compared with road, rail, or water transport.
- Strongly affected by adverse weather (fog, storms, high winds), which can cause delays or cancellations.
- Limited carrying capacity per trip, making it uneconomical for bulk, low-value goods.
- Accidents, though rare, tend to be catastrophic; also causes noise and air pollution around airports.
Importance of Air Transportation for Nepal
Nepal's rugged and mountainous topography makes road and rail construction extremely costly, slow, and vulnerable to landslides and floods. In such terrain, air transport — particularly STOL (Short Take-Off and Landing) airports in the hills and mountains — is often the only reliable means of connecting remote districts such as Jumla, Simikot, Mugu, and the Everest region (Lukla) with the rest of the country. Air transport is vital for the tourism and mountaineering industry, which is a major contributor to Nepal's economy, and it plays a critical role in disaster response and delivery of essential supplies, medicine, and personnel to inaccessible areas during earthquakes, floods, and epidemics. It also shortens journeys that would otherwise take several days on foot or by unreliable roads to just a few hours by air.
Question 3
History of Civil Aviation in Nepal
Give a chronological account of the history and development of civil aviation in Nepal. Include important milestones in the development of airports and airlines.
The development of civil aviation in Nepal can be traced through the following major milestones:
| Year | Milestone |
|---|---|
| 1949 | First aircraft landing in Kathmandu — a single-engine Beechcraft Bonanza carrying the Indian Ambassador landed at the Gauchar grazing ground, marking the formal beginning of aviation in Nepal. |
| 1950 | First international/charter flight operated by Himalayan Aviation, from Gauchar to Kolkata. |
| 1955 | King Mahendra formally inaugurated Gauchar Airport, renaming it Tribhuwan Airport. |
| 1957 | The grassy runway at Tribhuwan Airport was paved with concrete; the Department of Civil Aviation was founded under the Ministry of Works, Communication and Transport. |
| 1958 | Royal Nepal Airlines Corporation (RNAC) — Nepal's first national carrier — began scheduled domestic and international service. |
| 1960 | Nepal attained membership of the International Civil Aviation Organization (ICAO). |
| 1964 | Tribhuwan Airport was renamed Tribhuvan International Airport (TIA); around the same period, STOL airstrips such as Lukla (Tenzing–Hillary Airport) were developed to open up the mountain regions. |
| 1967 | TIA runway extended and the first jet aircraft (Lufthansa Boeing 707) landed at TIA. |
| 1992–93 | Adoption of the Liberal Civil Aviation Policy, allowing private airlines to operate domestically for the first time. |
| 1996–98 | Civil Aviation Act, 1996 enacted; Civil Aviation Authority of Nepal (CAAN) established (31 December 1998) as an autonomous body responsible for both regulation and service provision (air navigation services and aerodrome operation). |
| 2000s | Expansion of TIA's international terminal, development of additional domestic STOL airports, and entry of several new international carriers. |
| 2013 | Nepal placed on the ICAO Significant Safety Concern list, prompting institutional and regulatory reforms in the sector, including later separation of accident-investigation functions from CAAN. |
| 2020s | Commissioning of new international gateways — Gautam Buddha International Airport, Bhairahawa (2022) and Pokhara International Airport (2023) — to diversify air access to Nepal beyond Kathmandu. |
Question 4
Airport Site Selection Factors
Explain the important factors that should be considered while selecting a suitable site for an airport. Discuss any eight factors with their significance.
- Regional Plan / Land Use: The airport site must conform to the region's master land-use plan and should not conflict with future urban expansion, industrial zones, or other planned infrastructure.
- Accessibility to the City: The site should be well connected to the city it serves by road (and rail, where available) and located at an optimum distance — close enough for convenient access yet far enough to remain clear of built-up areas for noise and safety reasons.
- Availability of Suitable Land: Sufficient flat or gently sloping land must be available not only for the present runway/terminal requirements but also for future expansion of runways, taxiways, and terminal facilities.
- Topography of the Area: The general slope and grading of the site should permit economical earthwork and good surface drainage without excessive cut and fill; in hilly regions like Nepal this is often the governing factor.
- Obstructions: The site should be free from natural obstructions (hills, ridges, tall trees) and man-made obstructions (buildings, transmission towers) within the approach and transitional surfaces, since these limit the usable length of the runway and affect safety.
- Meteorological Conditions: Favourable wind pattern (for orienting the runway to maximise wind coverage), low fog/visibility restrictions, and low frequency of storms and turbulence are essential; wind rose data of the region must be studied in detail.
- Availability of Utilities: Water supply, electric power, telecommunication, and sewage disposal facilities should be readily available or economically extendable to the site.
- Sub-soil and Drainage Conditions: The sub-grade should have adequate bearing capacity for pavement construction, and the site should have natural or provide-able drainage to avoid water-logging of runways and aprons.
- Cost of Land and Development: The overall cost of land acquisition, grading, and construction should be within economically justifiable limits.
- Air-space Conflict: The site should be free from conflict with the airspace of nearby existing airports and military zones.
(Any eight of the above factors, explained with their significance, satisfy the requirement of the question.)
Question 5
Anatomy of a Passenger Aircraft
Draw a neat, well-labelled sketch of a typical passenger aircraft and explain the functions of the following components: Fuselage, Wing, Engine, Cockpit, Horizontal stabilizer, Vertical stabilizer, Landing gear, Wings.
Functions of Components
- Fuselage: The main body of the aircraft that houses the cockpit, passenger cabin, cargo compartments, and provides the structural backbone to which the wings, tail, and landing gear are attached.
- Wing: Generates the lift required to keep the aircraft airborne through the pressure difference created by airflow over its curved (aerofoil) cross-section; it also often houses fuel tanks and engine mounts.
- Engine: Produces the thrust that propels the aircraft forward, overcoming drag; mounted on the wings or fuselage depending on aircraft design.
- Cockpit: The forward compartment from which the pilot(s) operate and monitor all flight controls, instruments, and communication/navigation systems.
- Horizontal Stabilizer: A small horizontal aerofoil at the tail that provides longitudinal (pitch) stability and carries the elevator, which controls the aircraft's nose-up/nose-down attitude.
- Vertical Stabilizer (Fin): A vertical aerofoil at the tail that provides directional stability and carries the rudder, which controls yawing motion about the vertical axis.
- Landing Gear: The wheel assembly (with shock-absorbing struts) that supports the aircraft on the ground during taxiing, take-off, and landing, and retracts into the fuselage/wing during flight to reduce drag.
- Wings (control surfaces – ailerons): Movable surfaces on the trailing edge of the wings that control the rolling motion of the aircraft about its longitudinal axis.
Question 6
Roll, Pitch and Yaw
Explain the rolling, pitching, and yawing movements of an aircraft and describe how these movements are controlled by the aileron, elevator, and rudder, respectively. Draw a neat, well-labelled sketch showing the location and direction of movement of these control surfaces.
An aircraft in flight is free to rotate about three mutually perpendicular axes that intersect at its centre of gravity: the longitudinal axis (running nose to tail), the lateral axis (running wingtip to wingtip), and the vertical axis (running top to bottom). The rotation about each of these axes is controlled by a dedicated primary control surface.
Rolling — Longitudinal Axis — Ailerons
Rolling is the tilting motion of the wings about the longitudinal axis (nose–tail line), used to bank the aircraft for turning. It is produced by the ailerons, a pair of hinged control surfaces on the outer trailing edge of each wing that move in opposite directions — when the aileron on one wing deflects up (reducing lift on that side), the aileron on the other wing deflects down (increasing lift), creating a rolling couple.
Pitching — Lateral Axis — Elevator
Pitching is the up-and-down movement of the nose about the lateral (wingtip-to-wingtip) axis, which raises or lowers the aircraft's angle of attack for climbing, descending, or maintaining level flight. It is controlled by the elevator, a hinged surface on the trailing edge of the horizontal stabilizer; deflecting the elevator up pitches the nose up, and deflecting it down pitches the nose down.
Yawing — Vertical Axis — Rudder
Yawing is the side-to-side swinging motion of the nose about the vertical axis, used mainly to counteract adverse yaw during a turn and to control the aircraft's heading, particularly during crosswind take-off and landing. It is controlled by the rudder, a hinged surface on the trailing edge of the vertical stabilizer (fin); deflecting it to one side pushes the tail the other way, swinging the nose in the desired direction.
Question 7
Organizational Structure of ICAO
Explain the organizational structure of ICAO. Describe the roles of the Assembly, Council, and Secretariat and list the divisions of the Secretariat.
Assembly
The Assembly is the sovereign governing body of ICAO, composed of representatives from all Member States. It meets at least once every three years to review the work of the Organization in detail, set policy for the coming years, vote a triennial budget, and elect the Member States that will serve on the Council.
Council
The Council is a permanent body elected by the Assembly (36 Contracting States) that continues the work of ICAO between Assembly sessions. It is the executive governing body responsible for adopting international Standards and Recommended Practices (SARPs) as Annexes to the Chicago Convention, administering the finances of the Organization, and directing the Air Navigation Commission and various committees.
Secretariat
The Secretariat is the administrative and technical arm of ICAO, headed by the Secretary General, and is responsible for implementing the decisions of the Assembly and Council and for carrying out ICAO's day-to-day technical and administrative work.
Divisions (Bureaus) of the Secretariat
- Air Navigation Bureau (ANB)
- Air Transport Bureau (ATB)
- Technical Co-operation Bureau (TCB)
- Legal Affairs and External Relations Bureau (LEB)
- Administration and Services Bureau (ADB)
Question 8
Aims and Objectives of ICAO
Discuss the aims and objectives of ICAO and explain how ICAO promotes international cooperation in civil aviation.
ICAO was established under the Convention on International Civil Aviation (Chicago Convention), 1944, with the fundamental aim of developing the principles and techniques of international air navigation and fostering the planning and development of international air transport so as to ensure its safe and orderly growth throughout the world.
Aims and Objectives
- Ensure the safe and orderly growth of international civil aviation throughout the world.
- Encourage the art of aircraft design and operation for peaceful purposes.
- Encourage the development of airways, airports, and air-navigation facilities for international civil aviation.
- Meet the needs of the people of the world for safe, regular, efficient, and economical air transport.
- Prevent economic waste caused by unreasonable competition among airlines.
- Ensure that the rights of Contracting States are fully respected and that every State has a fair opportunity to operate international airlines.
- Avoid discrimination between Contracting States and promote overall safety of flight in international air navigation.
- Promote generally the development of all aspects of international civil aeronautics.
How ICAO Promotes International Cooperation
ICAO promotes cooperation by adopting uniform international Standards and Recommended Practices (SARPs) — published as 19 Annexes to the Chicago Convention — covering areas such as licensing of personnel, rules of the air, aerodrome design, and accident investigation, which all Member States are encouraged to adopt into their national regulations. It provides a common forum where States negotiate air-service agreements, coordinate air-traffic management across borders, share safety and security information, and receive technical assistance and training through its regional offices, thereby harmonising civil-aviation practice worldwide.
Question 9
The Five Strategic Objectives of ICAO
Describe the five strategic objectives of ICAO. Explain how these objectives help accommodate the future growth of international air transport while maintaining safety, efficiency, and environmental performance.
| Strategic Objective | Explanation |
|---|---|
| Safety | Enhance global civil-aviation safety by developing SARPs, promoting Safety Management Systems (SMS), and monitoring State safety-oversight capability through the Universal Safety Oversight Audit Programme (USOAP). |
| Air Navigation Capacity and Efficiency | Increase the capacity and improve the efficiency of the global air-navigation system through modernisation initiatives (e.g., performance-based navigation, seamless ATM) so that growing traffic can be handled without compromising safety. |
| Security and Facilitation | Safeguard civil aviation against acts of unlawful interference (security) while facilitating the efficient, orderly movement of passengers and cargo across borders. |
| Economic Development of Air Transport | Foster the development of a sound and economically viable civil-aviation system through liberalisation of air-service agreements, economic regulation guidance, and support to developing States. |
| Environmental Protection | Minimise the adverse environmental effects of aviation activities — aircraft noise, and emissions of CO2 and other pollutants — through technology standards, operational improvements, and market-based measures (e.g., CORSIA). |
Together, these five objectives provide a balanced framework: safety and security ensure the system remains trustworthy; capacity and efficiency ensure the infrastructure can physically accommodate rising passenger and cargo volumes; economic development ensures air transport remains commercially sustainable and accessible; and environmental protection ensures that this growth does not come at an unacceptable cost to the climate and communities around airports. By pursuing all five simultaneously, ICAO enables long-term, sustainable growth of international air transport rather than growth in any single dimension at the expense of the others.
Question 10
Role of the FAA
Explain the establishment, role, and major functions of the Federal Aviation Administration (FAA) in the aviation sector.
The Federal Aviation Administration (FAA) is the national aviation authority of the United States, established in 1958 under the Federal Aviation Act as an independent body (later placed under the U.S. Department of Transportation) to provide a single, unified authority for regulating and overseeing all aspects of civil aviation in the country.
Role
The FAA's central role is to ensure the safety and efficiency of civil aviation within U.S. airspace by regulating aircraft, airmen, airlines, and airports, and by operating the National Airspace System (NAS).
Major Functions
- Regulating civil aviation to promote safety, including certification of aircraft, airmen (pilots, mechanics), and air-traffic controllers.
- Operating and maintaining the Air Traffic Control (ATC) system, including radar, communication, and navigation facilities across the country.
- Developing and enforcing safety standards for aircraft design, manufacture, and maintenance (airworthiness certification).
- Certifying and regulating airports, including their design, construction, and operational standards.
- Conducting research and development on new aviation technologies, including efforts to modernise the airspace system (e.g., NextGen).
- Regulating and encouraging the U.S. commercial space transportation industry.
- Developing and enforcing regulations on aviation noise and environmental impact.
Question 11
Role of CAAN
Explain the role of the Civil Aviation Authority of Nepal (CAAN) in regulating and developing civil aviation and airport infrastructure in Nepal.
The Civil Aviation Authority of Nepal (CAAN) is Nepal's autonomous civil-aviation body, established on 31 December 1998 under the Civil Aviation Act, 1996, taking over the functions earlier performed by the Department of Civil Aviation. CAAN performs a dual role in Nepal — acting simultaneously as the regulator of civil aviation and as the service provider for air navigation services (ANS) and aerodrome operations.
Regulatory Functions
- Issuing and renewing licences for pilots, air-traffic controllers, engineers, and other aviation personnel.
- Certifying the airworthiness of aircraft and issuing operating permits/Air Operator Certificates to airlines.
- Formulating and enforcing civil-aviation safety and security regulations in line with ICAO SARPs.
- Conducting safety oversight, audits, and inspections of airlines and airport operators.
Developmental / Operational Functions
- Planning, constructing, and maintaining airport infrastructure — runways, taxiways, aprons, terminal buildings — at both international gateways (e.g., Tribhuvan International Airport, Gautam Buddha International Airport, Pokhara International Airport) and numerous domestic STOL airports across Nepal's hills and mountains.
- Providing air-traffic control, communication, navigation, and surveillance (CNS) services throughout Nepalese airspace.
- Undertaking master planning and phased expansion of airports to meet growing passenger and cargo demand.
- Coordinating with ICAO and international agencies for technical assistance, training, and compliance with international safety standards.
It may be noted that because CAAN historically combined both regulatory and service-provider functions, this dual role was identified by ICAO as a potential conflict of interest and contributed to Nepal being placed on the ICAO Significant Safety Concern list in 2013; subsequent reforms have moved toward separating some functions (such as accident investigation) into independent bodies to strengthen safety oversight.
Question 12
VFR vs. IFR Runway Capacity
Explain why runway capacities under VFR are higher than that under IFR.
Runway/airport capacity refers to the number of aircraft operations (landings and take-offs) that can be safely accommodated per unit time. This capacity differs sharply between Visual Flight Rules (VFR) and Instrument Flight Rules (IFR) conditions for the following reasons:
- Self-separation by pilots under VFR: In VFR conditions (good visibility, clear of clouds), pilots can visually see other aircraft and maintain their own safe separation, allowing aircraft to be sequenced much closer together in space and time.
- ATC-imposed separation under IFR: In IFR conditions (poor visibility, cloud, fog), pilots cannot see other traffic, so Air Traffic Control must enforce standard radar or procedural separation minima between successive aircraft, which are considerably larger than the spacing pilots would use visually.
- Approach and landing intervals: Under IFR, aircraft must follow a single, controlled approach path and cannot begin the approach until the preceding aircraft has vacated the runway or reached a safe separation distance, lengthening the time interval between successive operations.
- Use of multiple runways: Under VFR, closely-spaced parallel or intersecting runways can often be operated simultaneously and independently (visual separation compensating for the close spacing); under IFR, the same runways may have to be operated as a single dependent system because instrument separation rules do not allow simultaneous independent use at close spacing.
For these reasons, the same runway/airport system can handle significantly more operations per hour under VFR than under IFR, and airport capacity planning must design for the more restrictive IFR case whenever poor-weather operations are expected.
Question 13
Runway Orientation, Configuration and Location
Explain the factors on which the orientation, configuration, and location of a runway depend.
Runway Orientation
- Prevailing wind direction and its variability — the runway is normally aligned so that the wind-coverage (percentage of time crosswind component stays within the allowable limit) is maximised, as determined from wind-rose analysis.
- Presence of natural or man-made obstructions in the approach/take-off path.
- Local topography — hills, ridges, and valleys, especially significant in mountainous terrain like Nepal.
- Noise-abatement considerations — avoiding alignment directly over densely populated areas.
- Conflict with the airspace/approach paths of nearby airports.
Runway Configuration
- Wind variability — a single runway suffices where wind is strongly unidirectional; where cross-winds are frequent, intersecting or open-V configurations may be required.
- Required capacity (traffic volume) — parallel runways (close, intermediate, or far-spaced) are adopted to increase capacity as demand grows.
- Availability and shape of land at the site.
- Cost of construction and future expansion potential.
Runway Location
- Size and distribution of the passenger/cargo catchment area to be served.
- Accessibility — distance and connectivity to the city/highway network for ground transport.
- Obstruction-free approach and transitional surfaces around the proposed site.
- Suitability of sub-soil and drainage conditions for pavement construction.
- Environmental factors — noise impact, land use, and ecological sensitivity of the surrounding area.
Question 14
Airport Master Plan
What is an Airport Master Plan? Explain the major objectives of preparing an Airport Master Plan.
An Airport Master Plan is a comprehensive, long-range plan (typically covering a 15–20 year planning horizon) that presents the planner's conception of the ultimate development of a specific airport. It sets out the sequence and timing of development of airside facilities (runways, taxiways, aprons), landside facilities (terminal buildings, cargo complexes, access roads, parking), and supporting infrastructure, based on forecasts of future aviation demand.
Major Objectives of an Airport Master Plan
- To forecast future aviation demand (passenger, cargo, and aircraft-movement growth) and translate it into facility requirements.
- To provide an orderly, phased framework for the physical development of the airport that can accommodate this demand efficiently.
- To establish a realistic schedule of capital improvement projects and estimate their costs, aiding financial planning.
- To determine the ultimate airport layout, including land required for future expansion, so that land can be reserved/acquired in advance.
- To identify and mitigate environmental, noise, and land-use impacts of airport development on surrounding communities.
- To provide a technically sound and financially feasible basis on which airport authorities, government agencies, and funding institutions can plan and justify investment.
- To serve as a framework for consistent decision-making regarding all future airport improvements, ensuring compatibility between individual projects.
Question 15
Wind Rose and Runway Orientation (Direction Only)
Given the following wind data for a proposed airport site, draw the wind rose diagram and determine the most suitable runway orientation. Also calculate the wind coverage for the selected runway orientation.
Given Data
The percentage duration of wind from each of the 16 principal directions is given. The sum of the tabulated percentages is 86.5%, so the remaining 13.5% represents calm periods (winds too light/variable to have a defined direction).
| Direction | Duration (%) | Direction | Duration (%) |
|---|---|---|---|
| N | 10.3 | S | 14.3 |
| NNE | 8.1 | SSW | 10.0 |
| NE | 3.9 | SW | 5.7 |
| ENE | 1.8 | WSW | 1.6 |
| E | 1.0 | W | 0.5 |
| ESE | 0.4 | WNW | 0.3 |
| SE | 7.1 | NW | 7.2 |
| SSE | 8.7 | NNW | 5.6 |
Step 1: Plot the Wind Rose
Each of the 16 directions is drawn as a radial spoke at 22.5° intervals from a common centre, with the length of each spoke made proportional to the percentage duration of wind from that direction. The resulting diagram (below) is the wind rose for the site.
Step 2: Determine the Best Runway Orientation
Since a runway serves aircraft landing/taking-off from either end, the orientation is chosen along the axis (pair of opposite directions) that captures the maximum combined percentage duration of wind. The percentage duration is summed for each of the eight possible axes:
| Axis | Sum of Duration (%) |
|---|---|
| N – S | 10.3 + 14.3 = 24.6 |
| NNE – SSW | 8.1 + 10.0 = 18.1 |
| NE – SW | 3.9 + 5.7 = 9.6 |
| ENE – WSW | 1.8 + 1.6 = 3.4 |
| E – W | 1.0 + 0.5 = 1.5 |
| ESE – WNW | 0.4 + 0.3 = 0.7 |
| SE – NW | 7.1 + 7.2 = 14.3 |
| SSE – NNW | 8.7 + 5.6 = 14.3 |
Result
The N–S axis gives the maximum combined duration (24.6%), and is therefore the most suitable runway orientation, i.e., a runway numbered 18/36 (true bearing 000°/180°). The next-best axes are SE–NW and SSE–NNW (14.3% each), which could be considered for a secondary/crosswind runway if the primary runway alone does not provide the required wind coverage (usually 95% per ICAO/FAA guidance). It should be noted that this direction-only dataset does not include wind-speed classes, so a full crosswind-component check (as carried out in Q17) cannot be performed here; the orientation above is based purely on maximising the frequency of head-on wind.
Question 16
Type II Wind Rose Diagram
The following table gives the wind data for a proposed airport site. Draw a suitable Type II Wind Rose Diagram using the given data. Show the direction and percentage duration of wind for each wind-speed range.
A Type II wind rose additionally shows how the wind duration in each direction is distributed among different speed ranges, giving a fuller picture than the simple direction-only rose of Q15 (in fact, summing the three speed columns for each direction below exactly reproduces the Q15 totals, confirming the two datasets describe the same wind climate).
| Direction | 6–25 km/h (%) | 25–40 km/h (%) | 40–65 km/h (%) | Row Total (%) |
|---|---|---|---|---|
| N | 7.4 | 2.7 | 0.2 | 10.3 |
| NNE | 5.7 | 2.1 | 0.3 | 8.1 |
| NE | 2.4 | 0.9 | 0.6 | 3.9 |
| ENE | 1.2 | 0.4 | 0.2 | 1.8 |
| E | 0.8 | 0.2 | 0.0 | 1.0 |
| ESE | 0.3 | 0.1 | 0.0 | 0.4 |
| SE | 4.3 | 2.8 | 0.0 | 7.1 |
| SSE | 5.5 | 3.2 | 0.0 | 8.7 |
| S | 9.7 | 4.6 | 0.0 | 14.3 |
| SSW | 6.3 | 3.2 | 0.5 | 10.0 |
| SW | 3.6 | 1.8 | 0.3 | 5.7 |
| WSW | 1.0 | 0.5 | 0.1 | 1.6 |
| W | 0.4 | 0.1 | 0.0 | 0.5 |
| WNW | 0.2 | 0.1 | 0.0 | 0.3 |
| NW | 5.3 | 1.9 | 0.0 | 7.2 |
| NNW | 4.0 | 1.3 | 0.3 | 5.6 |
| Total | 58.1 | 25.9 | 2.5 | 86.5 |
To construct the Type II wind rose, concentric circles are drawn at a suitable radial scale, and for each of the 16 directions three concentric segments are plotted end-to-end along that spoke — the innermost segment representing the 6–25 km/h duration, the middle segment the 25–40 km/h duration, and the outermost (thin, since values are small) segment the 40–65 km/h duration. The completed diagram is shown below.
From the table and diagram, most of the wind (58.1% of all readings) falls in the moderate 6–25 km/h range, with the S, SSW, and N directions being both the most frequent and containing the highest proportion of stronger winds (25–65 km/h) — this is consistent with the N–S axis being identified in Q15 as the dominant wind axis.
Question 17
Wind Coverage & Crosswind Analysis
Wind data for all visibility conditions collected at a possible airport site is given below. Draw a wind rose diagram and determine the maximum wind coverage and the best orientation of the runway. The permissible cross wind component is 8.1 knots.
Given Data
Wind duration (%) is tabulated for 16 directions across five speed classes (0–4, 4–12, 12–20, 20–28, and 28–32 mi/h), summing to 100% (all visibility conditions, so no calm-wind deduction is needed). The permissible crosswind component is given as 8.1 knots, which is converted to 8.1 × 1.1508 ≈ 9.32 mi/h for consistency with the tabulated wind-speed units.
Method
For any trial runway orientation, and for a wind blowing from a direction making angle θ with the runway centreline, the crosswind component is calculated as:
Crosswind Component = V × sin θ
where V is taken as the mid-point velocity of each speed class (2, 8, 16, 24, and 30 mi/h respectively). For a trial orientation, the percentage duration of every direction/speed-class combination for which the computed crosswind component remains within the permissible limit (≤ 9.32 mi/h) is summed; this sum is the wind coverage for that orientation. The trial orientation is then rotated (in this case through all 16 principal directions, and finer 1° increments for refinement) until the orientation giving the maximum coverage is found — this constitutes the classical wind-rose overlay/template method used in airport site planning, performed here numerically instead of graphically.
Coverage for Trial Orientations along the 16 Principal Axes
| Runway Axis | Wind Coverage (%) |
|---|---|
| SSE – NNW | 85.9 |
| SE – NW | 85.7 |
| N – S | 83.8 |
| ESE – WNW | 82.7 |
| NNE – SSW | 80.9 |
| NE – SW | 77.8 |
| E – W | 77.7 |
| ENE – WSW | 75.3 |
Refinement and Result
A finer search at 1° increments between the SE and SSE axes (since these give the two highest coverages among the principal directions) shows that the coverage keeps improving until a true bearing of approximately 145°/325°, where the wind coverage reaches its maximum value of about 88.4%. The best runway orientation is therefore Runway 15/33 (true bearing ≈ 145°/325°), giving a maximum wind coverage of approximately 88.4%.
Since ICAO/FAA guidelines normally require a minimum wind coverage of 95% for a single runway, the computed coverage of 88.4% falls short of this requirement. This indicates that a single runway aligned along 145°/325° would still leave about 11.6% of the time with an unacceptable crosswind component, and in practice a second, crosswind runway (aligned, for example, closer to the N–S or NNE–SSW axis) would need to be provided to bring the combined wind coverage of the runway system up to the required 95%.