VFR Obstacle Clearance Requirements

Once again, there are various exceptions when it comes to minimum altitudes and distances, based on the operating context.  Let's see if we can make some sense of it all.

Except for the purpose of take-off or landing....

CAR 704.23 (Commuter)

• Day: must be at least 500 AGL and 500 feet horizontal from any obstacle
• Night: must be at least 1000 feet above any obstacle within 3 miles of route

CAR 705.32:  (Airline)

• Day: must be at least 1000 AGL and 1000 feet horizontal from any obstacle
• Night: must be at least 1000 feet above any obstacle within 5 miles of route (2000 feet in mountainous regions)

Air Law Potpourri

I went through some practice questions about Air Law this morning and it emphasized my need to study even more!  Here are some things I'd forgotten:

TRAINING

• Instrument Training
• CAR 425.21: with a CPL or ATPL, you may give a licensed pilot instrument training towards an IFR rating provided you have and instrument rating and:
• instructor rating OR
• 500 hours PIC of which 100 must be on the same group of aircraft used for training (and for Group 1, at least 10 hours on the type used for training)

AIRSPACE

• Class F Restricted
• CAR 601.04: A pilot may fly through an active area:
• if authorized by appropriate person
• if it doesn't pose hazard to aircraft
• if it doesn't jeopardize national security

• CAR 602.145: VFR Flight in ADIZ
• VFR flight within or into the ADIZ requires a Defense Flight Plan or Defense Flight Itinerary to be filed.
• Must revise time/point of entry if more than +/- 5 minutes or 20 NM.

AIRPORTS

• Take-off Alternates (i.e. weather is above take-off minima but below landing minima for that aerodrome):
• CAR 704.26 Commuter: if authorized on air operator certificate
• CAR 705.34 Airline: within 60 minutes with OEI (twin) or 120 minutes with OEI (three or four engines or ETOPS)

• Dispatch Limitations:
• CAR 704.49 and CAR 705.60: must be able to land at destination and alternate within
• Turbo-jets: 60% of landing distance available (LDA)
• Turbo-props: 70% of LDA
• must be suitable runway for aircraft and conditions, and can't take credit for more than 50% of anticipated headwind or less than 150% of tailwind
• CAR 704.50 and CAR 705.61: for turbo-jets, if wet runway expected, the calculated runway requirement must be increased by an additional 15%. (Can be less if AFM includes info, but not shorter than what is required by 704.49 / 705.60).

SYSTEMS

• Altitude Alerting System or Device
• CAR 605.36: required for turbo-jets, with these exceptions:
• MEL, or if no MEL, being ferried to location with device
• flight tests, PPCs, training
• if failure after TO, until it reaches location where it can be repaired

• GPWS
• CAR 605.37: required for 704 and 705 turbo-jets with MCTOW of more than 15000 kg (33069 lbs) and authorized to carry more than 10 passengers (exception - MEL). 

• Standby Attitude Indicator
• CAR 605.41: required for Part VII turbo-jets (some exceptions).  Required for Part VII turbo-props configured for 10 or more passengers.
• CAR 625.41: must be installed on turbojet aircraft, and operate for 30 minutes in the event of a complete electrical system malfunction

Bumping along

Reference AIM MET 3.7 Turbulence Reporting Criteria

Intensity:

• light
• turbulence: momentary, slight changes in altitude/attitude
• chop: slight, rapid, rhythmic bumpiness without appreciable changes in altitude/attitude
• moderate
• turbulence: greater than light, aircraft remains in positive control, variations in IAS
• chop: greater than light, rapid bumps/jolts without appreciable changes in aircraft altitude/attitude
• severe
• large, abrupt changes in altitude/attitude
• large variations in IAS
• momentary loss of control

Frequency:

• occasional (<1/3 of the time)
• intermittent
• continuous (>2/3 of the time)

Report:

• location
• time
• intensity
• in or near cloud
• altitude
• type of aircraft
• duration (if applicable)

High level turbulence not associated with cumuliform clouds should be reported as CAT.

De-icing and Anti-icing

Types of Fluids

• Type I
• minimum 80% glycol
• relatively low viscosity
• very limited anti-icing protection against re-freezing but does not protect against further accumulation
• Type II
• minimum 50% glycol
• high viscosity
• effective anti-icing
• for aircraft with Vr > 100 kts; shears off on take-off
• potential to lose effectiveness if improperly applied
• Type III
• properties between Type I and Type II
• for aircraft with Vr < 100 kts
• Type IV
• same fluid specifications as Type II, but longer holdover times
• dyed green to aid consistent application

Holdover Time

• the estimated time that the application of de-icing/anti-icing fluid will prevent the formation of frost, ice, or the accumulation of snow on treated surfaces of an aircraft
• begins when the final application of de-icing/anti-icing fluid commences, and expires when the fluid loses its effectiveness

Frozen Contaminants

Reference AIM AIR 2.12 Flight Operations in Winter

Factors affecting contamination and hold-over time:

• ambient temperature
• aircraft surface temperature
• de-icing / anti-icing fluid type, temperature and concentration
• relative humidity
• wind speed and direction

Cold-Soaking Phenomenon

• fuel temperature affects wing surface temperature
• cold-soaking at altitude means fuel in tanks may be much colder than ambient temperature after landing
• clear ice or frost may form on some aircraft on wing areas above fuel tanks, especially in conditions of high relative humidity

Volcanic Ash

You may recall the eruption of the Icelandic volcano Eyjafjallajokull in April 2010 caused massive disruptions to air travel in Europe.

Reference AIM AIR 2.6 and AIM MET 2.5

There are numerous hazards associated with volcanic ash:

• damage to surfaces, windshields, powerplants
• read about KLM 867 which had a quadruple engine failure near Anchorage Alaska in 1989
• contamination of heating, ventilation, hydraulic and electronic systems
• adverse effects on weight and balance

Ash can rapidly reach heights in excess of FL600, and weather radar is not effective in detecting it.

The best preventative measure is avoidance, although this could be difficult in IMC or at night.  "St. Elmo's fire is usually a telltale sign of a night encounter, although rapid onset of engine problems may be the first indication."  Refer to PIREPs, SIGMETS and NOTAMs and advice ATC if an eruption or ash is observed to help warn others. 

Clean Aircraft Concept

Reference AIM AIR 2.12 Flight Operations in Winter

Wing contamination is serious business.  Ice with the thickness and texture of sandpaper on the surfaces of an aircraft could decrease lift by 30% and increase drag by 40%.  As ice accumulates on a wing, the stalling speed increases and the angle at which the wing will stall decreases.

Clean Aircraft Concept:

• refers to take-off being prohibited when frost, snow or ice is adhering to any critical surface of the aircraft

Critical Surfaces refers to:

• wings
• control surfaces
• propellers
• horizontal stabilizers
• vertical stabilizers
• upper surface of fuselage in the case of aircraft with rear-mounted engines

CAR 602.11 Aircraft Icing

• no person shall attempt to conduct a take-off in an aircraft that has frost, ice, or snow adhering to any of its critical surfaces
• exception: frost on underside of wing caused by cold-soaked fuel (refer to manufacturer's instructions)
• take-off in icing conditions
• Part 705: PIC (or person designated by operator) must inspect immediately prior to take-off (or operator has established aircraft inspection program)
• Part VII other than subpart 5: operator has established aircraft inspection program  
• report observed ice to PIC (or designated person) so they can inspect
• PIC must inform other crew members of intention to de-ice/anti-ice

V Speeds

I knew the definitions of V1 and V2, but what about V3? Turns out we just call it something different on the Dash 8 - it's Vfri (flap retraction speed).  There are a ton of V Speeds, but I'll pick out some key ones. 

V1: engine failure recognition speed

• abort the take-off and bring the aircraft to a stop on the runway plus stopway OR
• continue and be at V2 at 35 feet above the departure end of the runway
• increases with weight

V2: take-off safety speed

• a referenced airspeed obtained after the aircraft lifts off and at which the required OEI climb performance can be achieved

Vmca: aim minimum control speed

• lowest calibrated airspeed at which control of an aircraft can be maintained following the failure of the critical engine with the remaining engine(s) operating at take-off power
• determined at gross weight with the C of G at the aft limit, flaps in take-off position, landing gear retracted, and the propeller windmilling if no autofeathering system is installed

Va: maneuvering speed

• maximum speed at which full deflection of the primary flight controls will not cause overstressing of the aircraft

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!

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?