Aviation meteorology, session 2

ENM – Sep 2008

Franck PITHOIS ENM/PAM

I- User Environment

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1. International Context2. Aircraft3. User Organization4. Measurement Units5. Altimetry Basics

I- User Environment

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International Civil Aviation Organization

• Dec. 7, 1944: Chicago Conference (52 states)• Wrote a convention covering international civil

aviation• Founded ICAO (190 member states in 2008)

1. International Context

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- Setting out the principles and techniques of international air navigation

- Promoting and planning the development of safe, reliable, efficient and cost effective air transport.

ICAO's purposes

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Wing tip

Leading edge

Trailing edge

Engine cowling

Wing

FlapsAileron

Elevator

Trim tab

2. Aircraft

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Aerodynamic forces

Relative airflow

DragThrust

Weight

Lift

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Lower surface: overpressure

Upper surface: underpressure

Leading edge

Trailing edge

VR

Relative airflow: VR

Link: http://www.av8n.com/how/htm/airfoils.html, for further explanations

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Lift:

Drag:

: Density of air

S : Reference surface

Vr : Aircraft/Air speed

Cx : Coefficient of drag

Cz : Coefficient of lift

P = Weight

T = Thrust (engine)

Fz

Fx

R : Aerodynamic resultant

T

P

Vr

Dynamic study of the forces in presence

xx

zz

CSVF

CSVF

2

2

2

12

1

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http://www.preciflight.com/FR/images/ROBIN_120.jpg

http://www.mpa80.be/mpa/mpaXpress_fichiers/pigeon.jpg

Various aircraft

http://www.chateau-chassignol.com/montgolfiere/5.jpg

http://www.altibulle.com/portail/images/ulm.gif

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a. Airspace structure (introduction)b. Different categories of usersc. Two types of flight rules: IFR/VFRd. Flight safety

3. User Organization

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In France:

1 UIR

5 FIR

In-flight information

a- Airspace structure: UIR/FIR

http://www.ecacnav.com/images/RVSM%20October%202007%20copy.jpg

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FIR

UIR

There are two categories of controlled airspace:

Control area: CTR

– CTR

Control region: CTA

– TMA, AWY, LTA & UTA

CTR

UTA

TMA

LTALTAFL195

FL115

FL660

Sol

Infinity

AWY

UIR

FIR

Vertical structure

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- Controlled airspace (classes A, B, C, D & E)

- Uncontrolled airspace (class F & G)

- Regulated airspace (marked as R)

- Dangerous airspace (marked as D)

- Prohibited airspace (marked as P)

Airspace classifications

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Examples

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What flies (in France)

• General aviation traffic

• Military aviation traffic

Operational military aviation traffic

Flight tests and aircraft acceptance

Airport operations (in France)

• Airport services: Air navigation…

• Airport operators: Chambers of Commerce & Industry, companies…

b. Different categories of users

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General Aviation Traffic

i. Commercial aviation

ii. Government and military aviation

iii. Business and recreational aviation

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i. Commercial aviation

Flights operated by international, domestic and regional airlines carrying passengers and cargo.

Performance by type of propulsion:

Jets (major airlines):

Operational ceiling: 8,000 to 12,000 m Speed: mach 0.9 to mach 2.2Range: 1,000 to 15,000 km

Turboprops (regional airlines):

Operational ceiling: 3,000 to 6,000 m Speed: 200 to 300 knots Range: 500 to 3/5,000 km

Piston engines (small operators):

Operational ceiling: 4 to 5,000 m Speed: 100 to 250 knots Range: 500 to 5,000 km

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ii. Government and military aviation

•Presidential or ministerial flights

•Customs service

•Civil protection

•SFACT (Aeronautical training and technical inspection service)

•Carrying passengers and cargo

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iii. Business and recreational aviation

Private flights: public transport other than scheduled flights and express cargo

Recreational aviation: motorized (airplanes + helicopters), gliders, free flight, ULM, skydiving and ballooning.

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Defined in line with IMC/VMC weather conditions

IFR: Instrument Flight Rules

VFR: Visual Flight Rules

c. Two types of flight rules: IFR/VFR

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IFR

- Suitably equipped aircraft

- Qualified crew (professional)

- Aircraft guidance using radio navigation equipment

- Procedures to follow (air traffic control)

- Radio communication equipment fitted

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Commercial aviation type flights, implying:

• Safety and reliability

• Different weather conditions during different phases of the flight: take off, cruising, landing

IFR

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VFR

• Less sophisticated aircraft equipment

• Generally a relatively less qualified crew (amateur)

• More restrictive visibility and ceiling conditions

• Subject to weather conditions

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Different types of VFR

• "Regular" VFR

• Special VFR: excluding VMC conditions, low altitude

• Night VFR: specific qualifications

• VFR on TOP: flight above the clouds

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Since 1999, the ICAO only keeps records on accidents involving aircraft with a certified maximum take off weight in excess of 2,250 kg

The total of death is quite egal despite a bigger trafic every year

d. Flight safety: International statistics

Year Flight kind Fatal accidentspassengers

killedTotal of death

1995 scheduled 26 376Non scheduled 26 376

1996 scheduled 24 1242 1806Non scheduled 26 564

1997 scheduled 26 1022 1319Non scheduled 21 297

1998 scheduled 20 1008 1237Non scheduled 19 229

1999 scheduled 21 581 718Non scheduled 16 137

2000 scheduled 18 811 1181Non scheduled 22 370

2001 scheduled 13 615 832Non scheduled 23 217

2002 scheduled 14 865 1108Non scheduled 19 243

2003 scheduled 7 466 683Non scheduled 25 217

2004 scheduled 9 203 410Non scheduled 18 207

2005 scheduled 17 712 961Non scheduled 18 249

2006 scheduled 13 755 836Non scheduled 13 81

2007 scheduled 11 587 673Non scheduled 14 86

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Passenger fatalities on scheduled flights

Excluding accidents due to illicit intervention

Years 1997 1998 1999 2000 2001 2002 2003 2004

Passenger fatalities per 100 million Pax/km

0.04 0.035 0.02 0.025 0.02 0.025 0.015 0.005

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Aircraft categories involved in accidents

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Source : DGAC

Occurrences

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4. Measurement Units

Horizontal distances: Nautical Mile(NM = 1852 m)

Horizontal speeds: Knots (KT)

Vertical distances: Feet (FT=0.3048 m)

Standard Flight Levels: 850 (FL050), 700 (FL100), 500 (FL180), 300 (FL300), 250 (FL340), 200 (FL390).

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a. Principle

b. A Reminder on Altitudes

c. ICAO standard atmosphere

d. Altimeter

e. Altimeter settings

5. Altimetry basics

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-Defining the altitude-pressure relationship in the vertical distance or elevation sense

- Resolving problems relating to determining vertical distances from pressure measurements.

a. Principle

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Height: The vertical distance between any point or level taken in relation to a reference point.

b. Reminder: Altitudes

height

runway

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Altitude: The vertical distance between any point or level Above Mean Sea Level (AMSL)

altitude

sea

runway

b. Reminder: Altitudes

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A fictitious atmosphere defined up to an altitude of 32 km:

- Air is a perfect gas with an invariable chemical composition

- Air is dry (Tv= T)

- Gravity acceleration is constant: g= 9.80665m/s²

c. ICAO standard atmosphere (1/4)

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- A vertical temperature gradient that is constant for each of the following intervals:

0 to 11 km: gradient of T = -0.65°C/100 m or 2°C /1000 ft

11 to 20 km: gradient of T= 0° (T = - 56.5°C)

20 to 32 km: gradient of T = 1°C/1000 m

c. ICAO standard atmosphere (2/4)

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- Pressure at sea level is 1013.25 hPa

- Temperature at sea level is 15°C or 288°k

c. ICAO standard atmosphere (3/4)

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Graphic representations

Z= f(P)

Z= f(T)

c. ICAO standard atmosphere (4/4)

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The instrument itself comprises aneroid capsules that are sensitive to pressure variations.

The measured pressure level is directly translated into a vertical distance in line with the standard atmospheric rule.

d. Altimeter: Operation

Graduated in feet, 1 ft = 0.3048 m

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d. Altimeter: Description

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1 Runway tour Height

Altitude2 Local flight

3 Moving Reference altitude

e. Altimeter settings: Why they were created

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e. Altimeter settings

• QFE

• QNH

• 1013

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Equivalent atmospheric pressure at the aerodrome's official altitude.

For a pilot this is the setting pressure that corresponds to a ZERO indication on their altimeter when their wheels touch down.

The setting reference is the runway.

QFE

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The pressure measured by the barometer brought back to the official runway altitude thanks to an altitude correction.

QFE = P(Station reference altitude) + dP

Calculating QFE

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During takeoff or landing phases for aerodromes located above 600 meters.

The altimeter provides the height in relation to the runway.

It is used less and less.

Advantage: when the plane touches the runway, the altimeter indicates ZERO.

Using QFE

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Station pressure returned to sea level by applying a standard correction.

For pilots, this setting gives them the flight or runway altitude in relation to sea level.In a standard atmosphere, the setting reference for QNH is the sea.

QNH

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QNH= P(station reference altitude)+dP’

Correction calculated just like QFEin standard atmosphere

Calculating QNH

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More and more often used for it offers many advantages:

Routes through mountain ranges. Takeoff and landing from aerodromes. Precise position at the auto-information stage. A good approximation of the plane's true altitude. Used under the transition altitude.

Using QNH

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Used to separate aircraft at their cruising altitude.

Fl 65Fl 60

Fl 50Fl 55

1013

0 ft

Isobar surfaces

Setting 1013

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Setting to use: Uncontroled airspace

3000 ft AMSL

3000 ft AGL

FL 30

QNH (or QFE) settings

FL 50FL 60

FL 35

FL 40

FL 45

FL 70

1013 settings, flight level indications

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Setting to use: Controlled airspace

FL 80

Transition zoneFL 50FL 60

FL 90

QNH settings, ‘Z’ indications

FL 701013 settings, flight level indications

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What is the lowest flight level that can be chosen to overfly an obstacle at an elevation of 3800 ft?

When QNH is:

- 1033 hPa

- 993 hPa

- 1013 hPa

Remember to add a safety margin of 500 ft!

1 hPa = 28 ft

Exercise