Airport Engineering MCQ Quiz - Objective Question with Answer for Airport Engineering - Download Free PDF

Explanation:

Maximum Longitudinal and Effective Gradients for 'A' Type Airport Runways

The International Civil Aviation Organization (ICAO) has set guidelines for the design and construction of airport runways. One of the important aspects to consider in runway design is the gradient, which affects the performance and safety of aircraft during landing and takeoff. The maximum allowable gradients help ensure that the aircraft can safely maneuver on the runway without excessive effort or risk.

The ICAO recommends that the maximum longitudinal gradient for 'A' type airport runways should be 1.50%. This ensures that the runway slope is not too steep for safe aircraft operations.

The maximum effective gradient, which considers the overall slope of the runway, should be 1.00%. This helps in maintaining a consistent and manageable slope for aircraft movement

Concept:

According to Horonjeff, the radius of a taxiway for a supersonic transport aircraft is given by:

\( R = \frac{0.388 \cdot W^2}{\left( \frac{T}{2} - S \right)} \)

Where:

W = Wheel base of aircraft = 30 m

T = Width of taxiway pavement = 22.5 m

S = Distance from midpoint of gear to pavement edge = \( 6 + \frac{\text{wheel tread}}{2} = 6 + \frac{6}{2} = 9 \, \text{m} \)

Step-by-step Calculation:

\( \frac{T}{2} = \frac{22.5}{2} = 11.25 \, \text{m} \)

\( \left( \frac{T}{2} - S \right) = 11.25 - 9 = 2.25 \, \text{m} \)

Now, \( R = \frac{0.388 \cdot 30^2}{2.25} = \frac{0.388 \cdot 900}{2.25} = \frac{349.2}{2.25} = 155.2 \, \text{m} \)

Concept:

According to ICAO, the basic runway length should be increased by 7% for every 300 m rise in elevation above mean sea level.

\(Correction = \frac{7}{100} \times \text{Runway Length} \times \frac{\text{Airport Elevation}}{300}\)

Given:

Runway length = 1840 m

Airport elevation = 250 m

Calculation:

\(Correction = \frac{7}{100} \times 1840 \times \frac{250}{300}\)

\(= 0.07 \times 1840 \times 0.8333 = 107.52 \, \text{m}\)

The apron is the area where aircraft are parked, loaded or unloaded, refueled, and maintained. It is typically located in front of the terminal building and is the designated space for ground handling operations like boarding, disembarking, and baggage handling

The turning radius is influenced by the speed of the aircraft (V) and the friction factor (f) between the aircraft tires and the taxiway surface. The formula provided (V²/125f) suggests a relationship where the turning radius increases with the square of the aircraft's velocity and decreases with higher friction. Understanding this relationship helps in designing taxiways that accommodate various aircraft speeds while ensuring safety during turns.

Concept:

Airport reference temp. (T_r) \(= {T_a} + \frac{1}{3}\left( {{T_m} - {T_a}} \right)\)

T_a = Avg. temp of the hottest month

T_m = Monthly mean of maximum daily temp. of same month.

Calculation:

T_A = 25°C

T_m = 40°C

\({T_\pi } = {T_a} + \frac{1}{3}\left( {{T_m} - {T_a}} \right)\)

\(= 25 + \frac{1}{3}\left( {40 - 25} \right)\)

= 25 + 5 = 30°C

Basic Runway length	It is the length of the runway under the following assumed conditions at the airport- Airport at sea level Standard temp at airport is 15℃ No wind is blowing Runway is levelled in longitudinal direction Aircraft is loaded at its full loading capacity The basic runway length is determined in three cases- Normal landing case – aircraft should stop within 60% of landing distance or runway length Normal take off case – minimum clearway width should be 150m and it is also kept free from obstructions. Engine failure case – In this case, basic runway length may consider either clearway or stopway or both.
Runway capacity	The ability of a runway system to accommodate aircraft landing and take off. It is usually expressed in operation per hour or operation per year.
Runway geometric design	The following items are to be considered in geometric design of runway- Runway length Runway width Width and length of safety area Transverse gradient Longitudinal and effective gradient Rate of change of longitudinal gradient Sight distance
Hanger	It is the covered area for repair and servicing the aircraft Hanger depends upon the size of aircraft and turning radius Number of hangers depends upon peak hour per volume of aircraft

Explanation:

Effective length of runway:  

For takeoff, effective length of the runway means the distance from the end of the runway at which the takeoff is started to a point at which the obstruction clearance plane associated with the other end of the runway intersects the runway centerline. 

Additional Information

Basic Runway Length:

• It refers to the length of an airport runway under the following assumptions:​
  • ​No wind is blowing on runway;
  • Runway is levelled (No effective gradient);
  • Airport is at sea level and Standard Temperature at the airport is 15°C;
  • Aircraft is loaded to its capacity;
  • No wind is blowing on the way to destination Standard temperature prevails along the way.

Concept:

The standard temperature at the airport site can be determined by reducing the standard mean sea level temperature of 15°C at the rate of 6.5°C per thousand meter rises in elevation.

Standard temperature = 15 - 0.0065 × elevation

Rise in temperature = (Reference Temp. - Standard Temp.)

Calculation:

Standard temperature =15 - 0.0065 × 2000 = 2°C.

Rise in temperature = 12 - 2 = 10°C

Explanation:

Effective gradient: As per ICAO Maximum effective gradient 

(i) For A, B and C type = Max 1%

(ii) For D and E type = Max 2%

Transverse gradient: Provided for drainge purpose. As per ICAO

(i) For A, B type = Max. value 1.5% and Min value 0.5%

(ii) For C, D and E type = Max. value 2% and min value 0.5%

Rate of change longitudinal gradient: AS per ICAO

(i) For A, B and C type = Max. 0.10% per 30 m for vertical curve

(ii) For E and D type = 0.4% per 30 m for vertical curve. 

Concepts:

Airport elevation is the reduced level above the Mean Sea Level of the highest point of the landing area.

Important PointsMean Sea Level

1. Mean Sea Level (MSL) is the datum for measurement of elevation and altitude.
2. Mean Sea Level is the equipotential surface of the Earth.
3. Mean Sea Level (MSL) adopted by a survey of India for reference is located at Mumbai High.
4. India's mean elevation is 160 m and is taken from Mumbai High.

Basic runway length is based on some assumptions:-

a) Derived at Mean Sea level

b) Derived for a standard temperature of 15°C

c) The gradient must be zero.

The actual runway need not follow all these guidelines and hence we must apply some corrections.

The sequential correction is applied in the basic runway length.

The first correction is altitude correction, the second correction is temperature correction and the last correction is gradient correction.

Altitude Correction:

Basic runway length is increased by 7% for every 300 m rise above mean sea level.

This is done due to the decrease in drag force on the aircraft owing to the decrease in density of air as the altitude increases.

Given:

Height above MSL = 1100 m, and Basic Runway length = 1500 m

After applying elevation correction,

\({\rm{Correction}} = 1500 \times \frac{7}{{100}} \times \frac{{1100}}{{300}} = 385{\rm{\;m}}\)

Corrected Runway Length = 1500 + 385 = 1885 m

Tips and Tricks:-

Temperature correction and gradient corrections are applied on the subsequently corrected runway length.

Factors affecting basic runway length
Aircraft characteristics	Power and propulsion system Type of an aircraft
Safety requirements	Normal landing Normal take-off case Engine failure case while take-off
Airport environment	Atmosphere Temperature wind Location and condition of the runway Altitude Runway gradient

Important point:

Basic runway length is calculated with the following assumptions:

i) It is calculated at Mean sea level (MSL)

ii) It is calculated for standard temp 15°C at MSL.

iii) The gradient is assumed to be zero.

Due to the variance of these assumptions, some corrections are applied.

i) Elevation Correction: 7% increase in basic runway length for every 300 m rise above MSL

ii) Temperature correction: 1% increase for every 1°C rise in airport reference temperature with respect to standard temperature at elevation.

Where,

Standard temperature at elevation = Temperature at MSL – 0.0065 × Elevation

This increase is made on the already corrected runway length for elevation.

iii) Gradient correction: 20% increase for 1% of effective gradient.

Explanation:

The height of the pilot's eye above the runway surface is assumed as 3 meters.

The height of the driver’s eye above the road surface is assumed as 1.2 meters.

Eye’s level of the driver/pilot is very essential factor in deciding the various geometric design factor for highway and runway respectively.

Explanation:

Taxiway:

• Taxiways as defined by ICAO are a defined path on a land aerodrome established for the taxiing of aircraft and intended to provide a link between one part of the aerodrome and another in an expeditious manner.

Design criteria for taxiway:

1) Longitudinal gradient as per ICAO

Type or Class of airport	Permissible gradient
A/B	1.5 %
C/D/E	3 %

2) Transverse gradient as per ICAO

Type/Class of airport	Permissible gradient
A/B/C	1.5 %
D/E	2 %

3) Rate of change of longitudinal gradient as per ICAO

Rate of change	Class of airport
1% / 30 m of vertical curve	A/B/C
1.2% / 30 m of vertical curve	D/E