Practical Meteorology

Practical Meteorology is all about applying all that meteorological theory to actual weather observations and forecasts.  There were a couple things I'd forgotten.   For example, with cloud layers, anything with 5/8 (broken) coverage or greater constitutes a ceiling.  This is not true if the it is a surface based layer, such as fog or snow.  In this case, the coverage must bee 8/8 to be considered a ceiling.  

Also, there are some charts that I don't use on a daily basis, because they cover much larger areas than I need on my regular runs between Montreal and Toronto.  When doing my practice questions, I was getting questions with regards to issuing and validity times wrong, so I knew it was time to consult the AIM.  

Prognosis = Forecast
Analysis = Observation

Reference AIM MET 3.2.1 Aviation Forecasts and Charts

Significant Weather Forecast - PROG Chart

• prepared 4 times daily, based on 00Z and 12Z data
• issued 12 hours prior to validity time (00, 06, 12, 18Z)
• specific flight level range (i.e. 700 - 400 MB = FL100 - FL240; also FL250-630)
• indicate surface positions of lows, highs, and any significant weather (thunderstorms, turbulence, mountain waves, etc)
• a forecast area of turbulence implies a 50% probability of encountering turbulence somewhere within the depicted area
• jet streams are depicted when the core speed is forecast to attain 80 knots or more

Upper Level Forecast - PROG Chart

• issued 4 times daily, 12 hours before the validity times of 00, 06, 12, 18Z
• applicable FL240, FL340, FL390, FL450
• depicts forecast wind and temperatures for the chart level

Reference AIM MET 3.2.3 Weather Charts

Surface Weather Chart

• observed at 00, 06, 12, 18Z
• issued 2-3 hours after observation
• pressure patterns from surface up to 3000 ft
• surface location of fronts, precipitation, obstructions to vision

Upper Level Chart - ANAL

• observed at 00 and 12Z
• issued over 3 hours after observation
• show reported atmospheric conditions at the pressure levels, such as wind speed/direction, temperatures, moisture content
• the contours or altitude gradient can be considered as the slope of the pressure surface

Airborne Weather Radar

It's been said that thunderstorms are among the most deadly hazards faced by pilots.  It's one thing to 'see and avoid' them when you're in VMC.  But what if you're flying in cloud and/or at night?

CAR 704.64 Airborne Thunderstorm Detection and Weather Radar Equipment (Commuter)
Needed if you have passengers in IMC when thunderstorms are expected along route.


CAR 705.70 Weather Radar Equipment (Airline)
Needed if you have passengers in IMC when thunderstorms are expected along route.

Recall: RADAR = RAdio Detection and Ranging (i.e. what's out there, which direction, and how far away?).  Azimuth scan for horizontal; tilt control for vertical.

Things to remember:

• rain provides the greatest radar echo intensity
• drop size determines radar echo intensity to a much greater extent than drop number
• "hooks" and "fingers" identify areas of hail and turbulence
• when thunderstorms contour on radar displays, they should be avoided by at least 20 NM
• when flying in moderate rain, the most important key to a more informative radar display is the use of the tilt control
• tilt the antenna beam to scan the middle/lower area of a CB
• attenuation is a loss of effectiveness due to the presence of large amounts of precipitation between the radar antenna and target storm cells

Notes about lightning detection system:

• displays electrical activity associated with a storm or line of storms
• does not detect the presence or intensity of precipitation
• able to detect electrical activity from cells that are located behind mountainous terrain

The probability of lightning strikes occurring to aircraft flying within a thunderstorm area is greatest when operating at altitudes where temperatures are between -5 and +5 C.

Critical Point

Also known as... should we return to our point of departure or continue to our destination after an engine failure, if there is no suitable alternate nearby?

Info you need:

• total distance (D)
• reduced (OEI) groundspeed home (RH)
• reduced (OEI) groundspeed out (RO)

For calculating groundspeeds, you need:

• track
• true airspeed
• wind direction and speed

And for calculating the time to the CP, you need

• AEO groundspeed out (GO)

**************************************

Formulae:

• Distance to CP = (D x RH) / (RO + RH)
• Time to CP = DCP / GO

**************************************

An increase in the tailwind component:

• decreases RH
• increases RO
• moves distance to CP closer to point of departure
• decreases time to CP

Instrument Landing System (ILS)

Reference AIM COM 3.12

Localizer

• valid and reliable signal coverage 35 degrees on either side of front course centre line up to 10 NM from transmitter
• 10 degrees up to 18 NM from transmitter for front and back courses
• 3-letter identifier
• starts with 'I' if aligned within 3 degrees of runway heading
• starts with 'X' if more than 3 degrees
• CDI needle deflection is 2.5 degrees from centre to full-scale

Glideslope

• beam depth is 1.4 degrees (0.7 above and below)
• standard glidepath is 3 degrees

Backcourse - Localizer only

• beware of reverse sensing!
• with an HSI, the track bar must be selected to the outbound course on localizer back course approaches in order to obtain positive track bar sensing

VHF Omnidirectional Range (VOR)

How does it work?

• it depends upon a phase difference between two signals transmitted simultaneously from a ground station
• position sensitive, NOT azimuth (i.e. no matter what direction you are facing, your instruments will give you the same VOR information about your position)
• line of sight: reception distance = 1.23 x sqrt(altitude above station)

Components:

• Omni Bearing Selector (OBS) >> select radials "FROM top, TO bottom"
• Course Deviation Indicator (CDI needle) >> centre to full scale is 10 degrees
• TO / FROM indicator >> directional ambiguity when crossing a radial 90 degrees from what is set on OBS

Tolerances:

• airway radials maintained by TC within +/- 3 degrees
• VOR checkpoint +/- 4 degrees
• dual VOR check +/- 4 degrees on ground or in air
• visual check over landmark +/- 6 degrees

To calculate distance (NM) from station:

• (groundspeed x time in minutes) / degrees of bearing change

Flight Time and Duty Time

I was Googling the CARs about Flight Time and Duty Time and came across this gem: a Study and Reference Guide for Chief Pilots of Commuter Operations.  It includes a number of questions (open-ended, not multiple choice) and the related CARs references.  It's perfect for highlighting some important info and a good way to test yourself.  Section 2 is particularly relevant to this post.

CAR 700.14 Monitoring System
(1) Operators need a system to monitor flight time, duty time, and rest period of each crew member.
(2) Flight crew members have the responsibility to notify the air operator if an assignment would result in the maximum times being exceeded.

CAR 700.15 Flight Time Limitations
Again, some things just need to be memorized:

• 1200 hours / 365 days
• 300 hours / 90 days
• 120 hours / 30 days (100 / 30 if on call)
• 60 hours / 7 days (aerial work / air taxi)
• 40 hours / 7 days (commuter / airline)
• 8 hours / 24 hours if single-pilot IFR

Of course there are always exceptions, like if the increase is authorized on the air operator certificate.

CAR 700.16 Flight Duty Time Limitations and Rest Periods

• 14 hours / 24 hours (includes 15 minutes of post-flight duties for commuter / airline)
• If 3 consecutive assignments are more than 12 hours, you need 24 hours off (unless you had 24 hours between each of them)
• If duty period includes a rest period, the duty time can be extended by up to half of the rest period (max. 3 hours), but the following rest period needs to be extended by the same amount. 

CAR 700.17 Unforseen Operational Circumstances

Maximums can be extended if the PIC and other flight crew agree and consider it safe.  This is for events such as unforecast adverse weather, equipment malfunction or ATC delay beyond the control of the air carrier.

CAR 700.18 Delayed Reporting Time

CAR 700.19 Requirements for Time Free from Duty

Whether flying or on call:

• Aerial Work / Air Taxi
• 3 x 24 hours / 30 days
• 13 x 24 hours / 90 days
• Commuter / Airline or On-Call
• 36 consecutive hours / 7 days
• 3 consecutive days / 17 days

CAR 700.20 Flight Crew Positioning
If a flight crew member is required to travel for the purpose of positioning:

• if the time for positioning is required after completion of a flight and is in excess of the flight crew member's maximum duty time then an additional rest period at least equal to half of the time spent travelling is required.

CAR 700.21 Flight Crew Members on Reserve

CAR 700.22 Long Range Flights

CAR 700.23 Controlled Rest on the Flight Deck

Must be authorized on the air operator certificate.

POP QUIZ!
What is the maximum allowable duty time for a flight crew member on reserve, if they are notified to report for duty between 22:00 and 06:00 without advanced notice? 
(Answer here)

What is the difference between a "flight crew member on reserve," a "flight crew member on standby" and a "flight crew member on call"?
(Answer here)

Life Jackets and Life Rafts

CAR 602.62 Life Preservers and Flotation Devices
When do you need them?
(1) taking off / landing on water, or unable to get to shore if you have an engine failure
(2) if you are operating more than 50 NM from shore

CAR 602.63 Life Rafts and Survival Equipment - Flights over Water
How far from shore before you need them?
(1) single engine or multi unable to maintain altitude with failed engine >> 100 NM or 30 min at cruising speed (whichever is less)
(2) multi-engine able to maintain altitude >> 200 NM or 60 minutes at cruising speed
(3) transport category aeroplane >> 400 NM or 120 minutes at cruising speed

High Speed Aerodynamics

Reference Turbine Pilot's Flight Manual Chapter 15

The SPEED OF SOUND in the atmosphere is solely dependent upon air temperature.
Temp (K) = Temp (C) + 273
Speed of sound (kts) = 39 x √ Temp (K)

A MACH METER is an instrument containing an airspeed capsule and an altitude capsule, which calculates the ratio between the aircraft's TAS and the local speed of sound.  The same Mach number can occur at markedly different indicated air speeds.

Airflow can be classified as SUBSONIC, TRANSONIC, or SUPERSONIC, dependent on how it's speed compares to the speed of sound.  Transonic flight usually ranges from 0.75 to 1.20 M.  Within this regime there is both subsonic and supersonic airflow.

CRITICAL MACH NUMBER is the highest flight speed possible without supersonic airflow over any part of the aircraft.

Air is compressible.  When an aircraft flies at slow airspeeds, the surrounding air molecules have time to 'get out of the way'.  As the vehicle's speed increases, air molecules begin to 'pile up' ahead of the aircraft, increasing air pressure, density, and temperature in that region... a powerful compression wave, or SHOCK WAVE, forms at the boundary between the disturbed and undisturbed air. 

I found this helpful diagram on the Wikipedia page about Compressible Flow.

As airflow passes through a shock wave:

• pressure increases
• temperature increases
• velocity decreases

LIMITING MACH NUMBER is the maximum operating speed of an aircraft in relation to the speed of sound.

Formation of a shock wave on the upper surface of a wing results in the center of pressure moving backward causing a pitch down.  This can lead to an unstable condition called MACH TUCK at speeds higher than Mmo.

In high speed aircraft, SWEEPBACK design is utilized to reduce drag and increase the Critical Mach Number.  An undesirable effect of sweepback design in a jet aircraft is "Dutch Roll," which is the tendency of an aircraft to roll whenever it yaws.  Key characteristics of a swept wing design:

• high speed operations
• poor slow speed handling
• long range performance
• increased lateral stability

Hypoxia / Hyperventilation

HYPOXIA

Definition: a deficiency in the amount of oxygen reaching bodily tissues

Symptoms: 

• apprehension
• air hunger
• cyanosis (blue discolouring of fingernails)
• headache
• euphoria
• loss of colour vision (the retina of the eye is very sensitive to hypoxia)
• tingling extremities

Time of Useful Consciousness:

• 25 000 ft: 3 to 6 minutes
• 30 000 ft: 45 to 75 seconds
• 40 000 ft: 13 to 30 seconds

Treatment: descend to lower altitude and/or breathe 100% oxygen

HYPERVENTILATION

Definition: an abnormal increase in the rate and depth of breathing, resulting from abnormally low level of carbon dioxide in the blood

Could be triggered by emotional tension / anxiety

Symptoms:

• dizziness
• tingling extremities
• hot / cold sensations
• nausea
• sleepiness

Treatment: consciously slow breathing rate.  Try breathing into a paper bag (i.e. re-breathe expelled CO2)

HYPOXIA / HYPERVENTILATION

There are very few distinguishable differences between the signs and symptoms of hypoxia and hyperventilation.  If unable to ascertain which one a passenger is suffering from, treat for hypoxia first. 

More info in Transport Canada's Handbook for Civil Aviation Medical Examiners.

How High Are We, REALLY?

True Altitude was something that always seemed to trip us up in ground school, but it's not actually that difficult.  In fact, if you read the instructions on your E6B, you're already more than half-way there!

True Altitude is particularly important when there are abnormally cold temperatures.  Usually the scenarios presented involve leveling off at a MEA, flying over a ridge, and realizing that you don't have nearly the amount of altitude clearance as you might have expected because it's -40. 

4 simple steps:

1. set air temperature over pressure altitude (make sure you're using the correct side!)
2. read true altitude over calibrated altitude scale (calibrated = planned - height of altimeter source)
3. add result of (2.) to height of altimeter source
4. subtract height of ridge to get ridge clearance

I'm tagging this both SAMRA and SARON because it fits in both Meteorology and Flight Operations.  So it could come up anywhere!

Turbine Engines

Suck, squeeze, bang, blow... intake, compression, power, exhaust.  The basic sequence of events on a gas turbine is the same as on the 4-cycle reciprocating engines we learned about in Private Pilot ground school.  But the components are different and turbine engines are much more efficient due to continuous flow conditions.  

INTAKE

COMPRESSION

Two types of compressors:

• axial-flow (more efficient)
• rotor blades: air deflected in direction of rotation
• stator vanes: direct and compress the flow of air
• centrifugal-flow (more durable)
• impeller: air directed towards center, then slung outward to diffuser
• diffuser: converts high velocity airflow into high pressure airflow for delivery to combustion section

POWER

Combustion is continuous and self-sustaining

EXHAUST

Turbines are turned by escaping gases, and in turn, drive the compressors through shafts.

Definitions

• bypass ratio: relationship between the mass flow of cold air through the fan to the mass flow of the hot air through the turbine
• engine pressure ratio (EPR): the ratio of turbine discharge total pressure to the total pressure at the compressor inlet (OUT / IN)
• free turbine: there are two separate shafts - one to drive the compressor section and the other to transmit power to the reduction gearbox and thus turn the propeller
• waste gate: controls the amount of exhaust gas which enters the turbine section of a turbo-charger
• flex temperature: the assumed temperature used in calculating the reduced thrust settings for take-off

Lots of systems material to cover... more to come!

Room to Breathe

Mark Twain wrote, “The air up there in the clouds is very pure and fine, bracing and delicious. And why shouldn't it be?--it is the same the angels breathe.”

For all its beauty and truth, we also know that at FL250, our time of useful consciousness is a mere 3 to 6 minutes. Hence, there are regulations about oxygen... requirements for quantity, duration, training, etc.

GENERAL

CAR 605.31 Oxygen Equipment and Supply

• non-pressurized aircraft 
• if more than 30 minutes between 10 000 and 13 000 >> all crew and 10% of passengers (at least 1 passenger) 
• above 13 000 >> all persons (for at least 1 hour if air transport) 
• pressurized aircraft following emergency descent 
• similar, but a bit more complicated, see table in regulations 

CAR 605.32 Use of Oxygen

1. Where an aircraft is operated at cabin-pressure-altitudes above 10,000 feet ASL but not exceeding 13,000 feet ASL, each crew member shall wear an oxygen mask and use supplemental oxygen for any part of the flight at those altitudes that is more than 30 minutes in duration. 
2. Where an aircraft is operated at cabin-pressure-altitudes above 13,000 feet ASL, each person on board the aircraft shall wear an oxygen mask and use supplemental oxygen for the duration of the flight at those altitudes. 
3. The pilot at the flight controls of an aircraft shall use an oxygen mask if

• the aircraft is not equipped with quick-donning oxygen masks and is operated at or above FL250; or
• the aircraft is equipped with quick-donning oxygen masks and is operated above FL410.

FIRST AID OXYGEN

CAR 704.67 (Commuter): if flying above FL250 >> supply one passenger for one hour

CAR 705.72 (Airline): 2% of occupants (at least 1 person) for one hour


PORTABLE OXYGEN

CAR 705.94 (Airline): above FL250 >> 15 min supply for each FA

Do you know what might happen if you don't use oxygen when your body requires it?Everyone reacts to hypoxia differently.  I went to the FAA Civil Aero Medical Institute in Oklahoma City for some invaluable High Altitude Training.  

Section 24 of Standard 724.115 and Section 29 of Standard 725.124 both specify that 'High Altitude Training is required for all flight crew members operating aeroplanes above 13 000 ASL before first assignment on a pressurized aeroplane and every three years thereafter.'

Medical Certificate

A pilot's medical certificate goes hand-in-hand with her license.  So it really makes sense that they are both in the aviation document booklet.  Now if only they could have a sticker for radio licenses as well...

CAR 404.03 Requirement to Hold a Medical Certificate
Essentially, to exercise the privileges of your license, you need to hold a valid medical certificate appropriate to that license.  So, according to CAR 404.10, if I want to use my ATPL, I need a valid Category 1 Medical.

CAR 404.04 Issuance, Renewal and Validity Period of Medical Certificates

This is a long one.  The keys in this context are paragraphs 6.1, 6.2 and 6.3, and I must remind myself that there have been some changes within the last year with regards to age restrictions:

• if I want to exercise the privileges of my ATPL, my Category 1 medical is valid for 12 months since I am under 40
• once I turn 40, if I want to operate single-pilot with passengers, the validity is reduced to 6 months
• once I turn 60, the validity is reduced to 6 months for all operations

CAR 404.06 Prohibitions Regarding Exercise of Privileges

Of course there are various things that can make my medical invalid, such as:

a) impairment (due to injury, drug, medical treatment)

b) involvement in an aircraft accident which resulted from impairment

c) pregnancy over 30 weeks

d) giving birth within the previous 6 weeks.  

That being said, there is always room for exemption (written authorization from Minister), which can be issued for a) and d) if it does not affect safety.  For example, I heard of a woman flying within days of giving birth to her third child.

CAR 404.18 Permission to Continue to Exercise the Privileges of a License or Rating

When you go to renew your medical, your CAME will deem you fit (with a stamp in your aviation document booklet, signed and dated) or unfit (you get your booklet back with nothing).  Also, CAR 404.04 states that if you go to renew your medical within 90 days of the end of the validity period, the next validity period is determined as if you renewed on the last day of the current validity period. 

• for example: my medical is valid until September 1, 2015
• if I renew on June 15, 2015, my next one will be valid until September 1, 2016
• if I renew on May 15, 2015 (too early), my next one will be valid until June 1, 2016

We've talked alot about regulations, but must also touch on the standards.  

Standard 424 Physical and Mental Requirements is a huge chart.  I've noticed in my practice questions that the frequency for getting ECGs gets some attention, so it would be good to review those:

For Category 1 Medicals, "routine electro-cardiography shall form part of the heart examination of an applicant:

• for the first issue of a medical certificate
• within the 2 years preceding the examination between ages 30 and 40
• within the 12 months preceding the examination after age 40

POP QUIZ!

An ATPL holder notes that his medical certificate has run out of time for Category 1 medical examination requirements.  Which license privileges may he now exercise and for how long?

Privileges

CAR 401.03 Requirements to Hold a Flight Crew Permit, License or Rating

In a nutshell, to exercise license (or permit, or rating, etc.) privileges, you must:

• have a valid license
• have the appropriate medical certificate
• carry these with you when exercising the privileges

CAR 401.04 Flight Crew Members of Aircraft Registered in Contracting States Other than Canada

Basically, if you want to fly a non-Canadian registered aircraft in Canada, you need either a Canadian license, or a license or foreign license validation issued by the contracting state.

But what can you actually do with an ATPL??

CAR 401.34 ATPL Privileges - Aeroplane

• exercise the privileges of a PPL and CPL (aeroplane)
• with a Group 1 instrument rating and appropriate type rating, while engaged in a commercial air service on an airplane that requires a minimum of two pilots, act as PIC (this is the exciting part!) or co-pilot

While we're at it...

CAR 401.47 Instrument Rating Privileges

• operate in IFR as appropriate for the group endorsed on the license
• exercise privileges of VFR OTT rating

CAR 401.48 Instrument Rating Period of Validity

• valid up to 24 months
• no recency required in first 12 months
• second 12 months require 6 IFR hours and 6 IFR approaches every 6 months (6-6-6 rule)

Things I'd Forgotten

Over the past week, I went through 171 'General Meteorology' practice questions... I got 150 (87.7%) of them right.  So there are obviously a few things that I'd forgotten since studying for my IATRA a couple years ago.  A few examples:

Terminology

• Overrunning: condition existing when an air mass is in motion aloft above another air mass of greater density at the surface.  This process that results in expansional cooling, subsequent condensation and formation of cloud. Example: warm air ascending the surface of a warm front. 
• Altimeter Setting: station level pressure reduced to MSL assuming ISA conditions
• Land breeze: blow from land to water during the night
• Stationary front: a frontal zone separating two different air masses, neither of which is strong enough to replace the other
• Riming: the growth of a descending ice particle as it collides with nearby water droplets which then freeze onto the particle

Location of Supercooled Water Droplets:

• in unstable air: lower levels of cloud where temperatures are only a few degrees below freezing
• in stable air: amount of supercooled water increases with height when temperatures are not far below freezing

Microbusts:

• The shaft of a microburst is normally about 2.2 nm wide or less at the surface.
• Downdrafts associated with a microbust could be as strong as 6000 ft / min

Mountain Waves:

• Rotor clouds are normally centred beneath the standing lenticular cloud (i.e. below each wave crest)
• The most powerful rotor is located under the first wave crest

Upper-Air Contour Charts:

• The wind blows along the contours in the same way that the 2000 ft wind blows along the surface isobars (parallel to the height contours, with lower heights on the left)
• the closer the contours, the stronger the wind; and if the height contours are curved, then centrifugal force acts on the wind

And other random facts:

• Snow grains: imply that freezing drizzle is present aloft.
• The vertical extent of CAT associated with a jet stream will be greatest on the low pressure, cold air mass side of the jet stream core.

I'll plan to cover some of these topics in more detail soon!  It's a good thing I like Meteorology... hopefully I'll still be this enthusiastic when I come back to Radio Nav :)

Air Masses

It is bitterly cold tonight, and one of the top news stories this week has been the weather across the entire country.  

Reference ACWM Chapter 6

Definitions:

• Air mass: a body of air whose temperature and humidity characteristics are uniform in the horizontal.
• Source region: a large area of land or ocean of relatively uniform characteristics and above which an air mass can form.
• Front: a transition zone between two air masses

Classification of Air Masses:

• Continental Arctic (cA)
• Maritime Arctic (mA)
• Continental Polar (cP)
• Maritime Polar (mP)
• Continental Tropical (cT)
• Maritime Tropical (mT)

Canadian Air Masses: cA, mA, mP, mT

Air masses may be modified as they migrate from their source regions.

• cold air (i.e. cA) moving south over the Lake Ontario in the winter becomes unstable since it is warmed from below, contributing to snow showers in Buffalo / south shores.
• warm air (i.e. mT) moving north over the Great Lakes in the spring becomes more stable since it is being cooled from below, contributing to stratus cloud, drizzle and fog over the north shores

POP QUIZ!

A south-westerly flow of Maritime Tropical air moving over the Labrador Current would produce what kind of fog?

Where are we?

General Navigation Terms

• air position: calculated position assuming no wind effect
• dead reckoning (DR) position: calculated position with due allowance for possible wind effect

• great circle: a circle on the surface of a sphere whose centre coincides with the centre of the sphere; the shortest distance between two points
• rhumb line: cuts all meridians at the same angle

Fun fact: the equator is both a great circle and a rhumb line.

Now, who has actually used an astro compass? Not  me. But they're still out there.

• Greenwich Hour Angle (GHA): the angular distance between the Greenwich meridian and the meridian of a celestial body, measured westward through 360 degrees
• Local Hour Angle (LHA):  the angular distance between an aircraft's meridian and the meridian over which a celestial body is located, measured westward; LHA = GHA + E (or - W) longitude

Since the earth is (approximately) spherical and maps are flat, projections of the earth's surface onto paper have some distortion.

Projections

• Mercator
• straight line represents a rhumb line
• distortion increases with distance from the equator
• Transverse Mercator
• used on VTA charts
• straight line approximates great circle track
• Lambert Conformal Conic
• used on VNC and WAC charts
• straight line approximates great circle track
• Polar Stereographic

You need to know: 

• 1 degree of latitude is 60 NM
• 1 timezone is 15 degrees of longitude

Enroute Charts

• information for radio navigation (no cities / towns / topography)
• scales are not constant - they vary to suit the requirements of each individual chart
• Lambert Conformal Conic projection
• Low Altitude (LO): for use up to, but not including 18 000 ft
• High Altitude (HE): for use at 18 000 ft and above
• Terminal Area: for use up to, 18 000 ft larger scale for congested areas

Distance Measuring Equipment (DME)

Operating Principle: the measurement of the time between the transmission of an aircraft interrogating signal and the receipt of a matched pulse reply signal from a ground station (the 2 signals having different frequencies).

DME operates in the UHF range, but can be collocated with a VOR or ILS, or occasionally NDB. Distance information can also be obtained from TACAN stations by selecting the paired VOR frequency.

DME measures slant range, not distance along the ground. Therefore, the greatest error occurs when flying high and close to the station.

Tolerance at a VOR checkpoint: +/- 0.5 NM

Radio Theory

Radio... what FGU calls the 'modern magic genie' :)

Some basic definitions:

• wavelength: linear measurement of a wave in meters
• cycle: peak to peak vibration period measured in seconds
• frequency: number of cycles per second measured in hertz

Wavelength remains constant, but the amplitude (strength) decreases with distance from the transmitting station.

Frequency Bands:

• Low and Medium Frequency (LF / MF): NDBs
• High Frequency (HF): long range communication
• Very High Frequency (VHF): communication, VOR, ILS
• Ultra High Frequency (UHF): DME, glideslope of ILS

Characteristics:

• LF/MF/HF
• ground waves: follow the surface of the earth; can bend and be attenuated (higher frequencies = more attenuation = less reception distance)
• sky waves: travel up into the atmosphere and are reflected back to earth from the ionosphere
• skip distance: the distance between the transmitting antenna and the point where the skywave first returns to the surface of the earth
• skip zone: the space between the end of ground wave coverage and the point at which the first sky wave is returned to earth
• VHF
• line of sight

Comm and nav systems will get their own separate posts soon - stay tuned!

Thunderstorms Part I

No chit-chat this time, let's get started.

Reference ACWM Chapter 15

Requirements for development of a thunderstorm:

• high relative humidity
• steep lapse rate
• lifting force / triggering action

Life cycle of a thunderstorm (1 - 3 hours):

• cumulus stage: only updrafts are present in the cloud
• mature stage: starts at onset of precipitation at the surface; updrafts and downdrafts
• dissipating stage: presence of downdrafts throughout nearly the whole cell

Classification of thunderstorms:

• airmass: form within a warm, moist air mass; isolated
• frontal: warm front (embedded in stratiform layer; least severe), cold front (form in continuous line; quite severe), trowal (rapid lifting of warm, moist air; moderate severity)
• squall line: most severe, may include heavy hail, destructive winds, tornados; often form 100-200 miles ahead of fast-moving cold fronts
• convective: formed by heating from below or by convergence of wind flow
• orographic: wind forces moist, unstable air up mountain slopes
• nocturnal: unusually warm air aloft, frequently occurs at night or early morning in Midwest / Central Plains

POP QUIZ!

You've inadvertently just flown into a thunderstorm cell.  What do you do?

Discussion of tornados, hurricanes and hazards to follow.

The Foggiest Idea

Fog is a weather hazard which can create all sorts of problems and delays.  Different meteorological scenarios produce different types of fog, and understanding these can help us anticipate when it may form.

Reference ACWM Chapter 10 on Visibility

The requirement for the formation of all types of fog is high relative humidity.  Typically this happens as the air temperature is lowered to the dew point (but not always - with steam fog, the dewpoint is raised to the air temperature).  It also involves condensation nuclei and some physical process which causes condensation to occur. 

Types:

• advection fog: cooling of warm air as it moves over a colder surface (land or water)
• radiation fog: cooling of the earth's surface at night (land)
• upslope fog: adiabatic/expansion cooling 
• steam fog: water vapor is added to very cold air
• ice fog: addition of water vapour to air through fuel combustion which then sublimates into ice crystals
• frontal fog: evaporation of rain that falls from the warm air into the cold air preceding a warm front

POP QUIZ!

What is the difference between fog and mist? (TC AIM MET 3.15, WMO Code, Table 4678)

The Earth's Atmosphere

Being a complete aviation nerd, I have no shame in admitting that Meteorology was one of my favourite subjects in flight school. And whereas I'd like to jump into things like lapse rate and stability, I'll save those for later and start with the basics.  Our trusty Study and Reference Guide starts with these topics about the Earth's Atmosphere:

Properties - from ACWM Chapter 2

• mobility
• capacity for expansion
• capacity for compression

Vertical Structure - in ascending order

• troposhere
• contains all the elements of the weather
• temperature decreases with altitude
• tropopause
• height varies from about 8 km over the poles up to 17 km over the equator
• there is an abrupt change in height over each frontal surface
• higher in the summer than in the winter
• In ISA conditions its height is 36 090 ft and temperature is -56.5 C
• stratosphere
• temperature remains steady and then increases with altitude
• stratopause
• temperature starts to decrease with altitude
• mesosphere
• temperature decreases with altitude to about 275 000 ft
• mesopause
• lowest temperature
• thermosphere
• where aurora are seen
• temperature increases dramatically with altitude

ICAO Standard Atmosphere (ISA)

• At sea level: 15 C and 1013.2 hPa / 29.92"Hg
• Average lapse rate is 1.98 C / 1 000 ft

Some things you just have to memorize:

Pressure Level (mb)	Altitude (ft)
700	10000
500	18000
400	24000
250	34000
200	39000
150	45000

And now... time for a POP QUIZ!

(1) What are lines drawn on weather charts joining places having the same temperature called?

(2) Does TAS increase or decrease with temperature?

(3) If the temperature at FL300 is -50, how would this be expressed in terms of an ISA deviation?

Flight Attendants

I'm not sure the general public has a real appreciation for the role of flight attendants as essential crew members.  They are our eyes and ears in the cabin, and they are integral to the safe operation of the aircraft, especially in emergency situations. 

CAR 705.104 Flight Attendant Requirements

(1) the basics:

(a) 1 - 40 pax ... 1 attendant

(b) 41 - 80 pax ... 2 attendants

(c) 81+ pax... 1 attendant for every unit of 40 pax or portion thereof

Of course, there are exceptions

(2) you may need more if required to cover all duties in the event of an emergency, or if required by the company operations manual

(3) you may use less if authorized on the air operator certificate

(4) if there is more than 1 deck (i.e. B747 or A380), (1) and (2) apply to each deck

This is your First Officer speaking...

These are the days now that passengers rarely see their pilots on airline flights, because we are usually behind a closed flight compartment door.  So I suppose it shouldn't surprise me how often I get asked, "Do you get to make the announcements over the PA?" because this is their main point of contact, albeit one-way.  But in my case, it is usually the captain who makes announcements, and the most I typically say is "Flight Attendants, please prepare the cabin for arrival."

CAR 705.74 Public Address System

No person shall operate an aircraft with passengers on board unless the aircraft is equipped with a public address system that can be operated independently of the interphone system required by section 705.73, except for handsets, headsets, microphones, selector switches and signalling devices.

And while we're at it,

CAR 705.73 Interphone System

This regulation complements the PA one (i.e. needs to be operated independently as well) but the difference is it is regardless of whether or not you have passengers on board.

Don't get a speeding ticket!

I remember back when I first started flying the Toronto - Montreal route, we were on the descent into Montreal and ATC was asking us to keep the speed up.  And while we could give them about 280 kts for a while, it was also our responsibility to "not get a speeding ticket," as Captain K reminded me. 

CAR 602.32 Airspeed Limitations
(a) max 250 KIAS below 10 000 ft
(b) max 200 KIAS below 3 000 ft within 10 NM of a controlled aerodrome (unless otherwise authorized by ATC)

Of course, there are exceptions: if you have a special flight operations certificate (i.e. for an airshow); or if your minimum safe airspeed for that flight configuration is greater, the aircraft shall be operated at the minimum safe airspeed.

CAR 602.33 Supersonic Flight
Put simply, it's not allowed. 

While we're here, we should cover en-route speeds as well. 

AIM RAC 8.3 Mach Number / True Airspeed - Clearances and Reports
(1) Assigned Mach numbers shall be adhered to within 0.01 Mach.  If unable, ATC is to be informed when the clearance is issued (this is also stated in AIM RAC 12.1)
(2) If TAS is intended to change by more than 5%, advise ATC as soon as practicable.

How about holds?

AIM RAC 10.7 Holding Procedures - Speed Limitations
(a) propeller: 175 KIAS (climbing: normal speed subject to 602.32)
(b) civil turbojet: 230 KIAS up to 14 000; 265 KIAS above 14 000 (climbing: 310 KIAS subject to 602.32)

Shuttle Climbs/Descents

AIM RAC 10.9 Shuttle Procedure
Shuttles are not the same as climbs/descents in a hold, even though the patterns are similar.  There may be a limit published on the instrument procedure chart, otherwise use the normal climb/descent speed for the aircraft type and airspace classification, subject to 602.32.

And one final note...

AIM RAC 9.7.3 Speed Adjustment - Radar Controlled Aircraft
Pilots complying with a speed adjustment are expected to maintain a speed within 10 KIAS of the specified speed.  The issuance of an approach clearance normally cancels a speed adjustment.  Once again, all aircraft are still subject to CAR 602.32.  

Hand-Held Fire Extinguishers

I'm going to jump between subjects to keep things interesting, but I'll tag each post so they are searchable.  However, in keeping with the tradition of one of my best ground school instructors, we're going to start with Air Law.  Though it is arguably one of the less exciting subjects, there is no denying that knowledge of Air Law is essential.   So without further ado...

Remember: 704 is for Commuter Operations; 705 is for Airlines, and the requirements are different.  

CAR 704.83 says that you need at least one hand-held fire extinguisher readily accessible in the passenger compartment if you are flying with passengers.

CAR 705.93 is about 7 paragraphs long, and details quantity, location, type, and demarcation requirements.  Key take-away: in addition to one hand-held fire extinguisher in the flight compartment, there needs to be 2 or more in the cabin, based on the number of passenger seats (regardless if there are passengers in them or not):
(a) 60 or fewer passenger seats, two extinguishers;
(b) 61 to 200 passenger seats, three extinguishers;
(c) 201 or more passenger seats, one extra extinguisher for each additional unit of 100 passenger seats.
You also need one in each of the Class E cargo compartments and isolated galleys, if so equipped. 

So on a Dash-8 Q400 with seating for 72 passengers, a total of 4 hand-held fire extinguishers would be required (1 in the flight compartment and 3 in the cabin).

2015: The Year of the ATPL

I'm not particularly one for making New Year's resolutions.  But this wintry weather in Montreal coincides with the beginning of the year and a few days off before starting work again, so it's a perfect time to start studying for my ATPL exams (which I plan to write by the end of March).  

Transport Canada has provided a lovely 46-page Study and Reference Guide for my reading pleasure... and who wouldn't want to spend their quiet evenings with a cup of hot chocolate, pouring through textbooks and notes in order to prepare for 7 hours worth of exams? (SARON, SAMRA, 80 questions/3.5 hours each, minimum pass mark 70%, but aiming for perfection!).  My plan is to provide highlights here, which will hopefully benefit others in the future.  

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A quick note about the name of this blog, 'Checklist'. That's essentially what the Study and Reference Guide is... a checklist to refer to, so we can verify we've covered everything.  And according to the CARs:

CAR 704.19 Checklist
(a) have a checklist and make it available
(b) use it

CAR 602.60 (2) further explains checklist requirements: basically it shall enable the aircraft to be operated in normal, abnormal and emergency conditions.

Sounds like a no-brainer right?  Yet, somehow, we still hear stories about pilots skipping steps because they think they can do them by memory.  Or worse: making up their own procedures.  

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The other portion of course is the 1500 TT requirement.  I'm roughly on track to achieve that by the end of the year.  And so it is my hope and goal that 2015 goes down in my book as the Year of the ATPL.  

Thanks for joining me... now sit back, relax, and enjoy the flight :)