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Adequate Aerodrome
Is an aerodrome that the operator considers as satisfactory to use taking into account various characteristics (availability, runway length, services, ...).
For aeroplanes without ETOPS approval, certain rules exist regarding the maximum allowed distance from an adequate (or alternate) aerodrome.
Class A (20 or more Seats) = max 60min from alternate
Class A (19 or less Seats) = max 120min from alternate
Class B & C = 120min or 300NM (whichever is less) from alternate
! These are at one engine inoperative cruising speed
Twin-engine aeroplanes that exceed these values require an ETOPS approval which grants the operator a larger maximum distance.
Alternate Aerodromes
- Take off alternate
Required as soon as a landing is required directly after take off and a landing on the departure runway is no longer possible
Twin-engine aeroplanes = Located within 1 hour with one engine inoperative
Multi-engine aeroplanes (or Twin-engine with ETOPS) = Located within 2 hours with one engine inoperative
A take off alternate can only be selected when weather reports/forecasts indicate that during a period, one hour before and one hour after expected time of arrival the weather conditions will be at or above the operating minima
- Destination alternate
Operator must select at least 1 destination alternate for each IFR flight, unless;
- Flight lasts 6 hours or less, or
- Destination has 2 separate runways available and;
weather reports/forecasts indicate that during a period, one hour before and one hour after expected time of arrival;
- Cloud ceiling is at least 2000ft (or circling height + 500ft)
- And visibility at least 5km
The planning minima (1 hour before and after expected time of arrival) for choosing an destination alternate;
- If CAT II a CAT III available = CAT I (RVR) minima
- If CAT I available = Non-precision landing (RVR + lower cloud base at/above MDH) minima
- Non-precision landing available = Non-precision landing + 200ft minima
- Circle-to-land available = Circling approach minima
Minimum Time Routes
They provide minimum time tracks between 2 points regarding flight time. Calculations take account of prevailing wind and weather conditions, and any restrictions imposed by ATC.
Polar Flights - Errors
The directional gyro retains the course reference for long periods of time and must therefore at intervals be re-adjusted using the compass. However, as the compass in the polar regions is not working correctly, there can be no reliable re-adjustment to the directional gyro.
1. Earth Rate (Astronomical Precession)
As we move or remain stationary on the surface, the earth is turning around its axis. While this is happening the gyro in our aircraft keeps its initial position relative to space, which will create deviations.
Earth Rate = 15 x Sin (mean latitude)
The answer will be degrees per hour that the gyro indicator deviates
The earth rate is corrected for by a "latitude nut" (adjustment screw on the gyro) which will generate a counter-error and so compensates for earth rate. However, this only works for a fixed latitude!
2. Transport Wander (Precession)
While moving in an easterly or westerly direction. All gyros are initially aligned with true north, if now the aeroplane travels east - west (except on equator), it will lose its alignment because it is stable in space.
Transport Wander = Change of Longitude x Sin (Mean latitude)
3. Random or Real Wander
Because the gyro is still a mechanical device, it can give faulty readings due to friction for example. When Questions state a "perfect Gyro" we can ignore random/real wander.
So the Total Variation of a Gyro = Earth rate + Latitude nut + Transport Wander + Real Wander
The Signs (NORTHERN HEMISPHERE);
Earth rate = -
Latitude nut = + (opposes earth rate)
Transport wander East = -
Transport wander West = +
Is an aerodrome that the operator considers as satisfactory to use taking into account various characteristics (availability, runway length, services, ...).
For aeroplanes without ETOPS approval, certain rules exist regarding the maximum allowed distance from an adequate (or alternate) aerodrome.
Class A (20 or more Seats) = max 60min from alternate
Class A (19 or less Seats) = max 120min from alternate
Class B & C = 120min or 300NM (whichever is less) from alternate
! These are at one engine inoperative cruising speed
Twin-engine aeroplanes that exceed these values require an ETOPS approval which grants the operator a larger maximum distance.
Alternate Aerodromes
- Take off alternate
Required as soon as a landing is required directly after take off and a landing on the departure runway is no longer possible
Twin-engine aeroplanes = Located within 1 hour with one engine inoperative
Multi-engine aeroplanes (or Twin-engine with ETOPS) = Located within 2 hours with one engine inoperative
A take off alternate can only be selected when weather reports/forecasts indicate that during a period, one hour before and one hour after expected time of arrival the weather conditions will be at or above the operating minima
- Destination alternate
Operator must select at least 1 destination alternate for each IFR flight, unless;
- Flight lasts 6 hours or less, or
- Destination has 2 separate runways available and;
weather reports/forecasts indicate that during a period, one hour before and one hour after expected time of arrival;
- Cloud ceiling is at least 2000ft (or circling height + 500ft)
- And visibility at least 5km
The planning minima (1 hour before and after expected time of arrival) for choosing an destination alternate;
- If CAT II a CAT III available = CAT I (RVR) minima
- If CAT I available = Non-precision landing (RVR + lower cloud base at/above MDH) minima
- Non-precision landing available = Non-precision landing + 200ft minima
- Circle-to-land available = Circling approach minima
Minimum Time Routes
They provide minimum time tracks between 2 points regarding flight time. Calculations take account of prevailing wind and weather conditions, and any restrictions imposed by ATC.
Polar Flights - Errors
The directional gyro retains the course reference for long periods of time and must therefore at intervals be re-adjusted using the compass. However, as the compass in the polar regions is not working correctly, there can be no reliable re-adjustment to the directional gyro.
1. Earth Rate (Astronomical Precession)
As we move or remain stationary on the surface, the earth is turning around its axis. While this is happening the gyro in our aircraft keeps its initial position relative to space, which will create deviations.
Earth Rate = 15 x Sin (mean latitude)
The answer will be degrees per hour that the gyro indicator deviates
The earth rate is corrected for by a "latitude nut" (adjustment screw on the gyro) which will generate a counter-error and so compensates for earth rate. However, this only works for a fixed latitude!
2. Transport Wander (Precession)
While moving in an easterly or westerly direction. All gyros are initially aligned with true north, if now the aeroplane travels east - west (except on equator), it will lose its alignment because it is stable in space.
Transport Wander = Change of Longitude x Sin (Mean latitude)
3. Random or Real Wander
Because the gyro is still a mechanical device, it can give faulty readings due to friction for example. When Questions state a "perfect Gyro" we can ignore random/real wander.
So the Total Variation of a Gyro = Earth rate + Latitude nut + Transport Wander + Real Wander
The Signs (NORTHERN HEMISPHERE);
Earth rate = -
Latitude nut = + (opposes earth rate)
Transport wander East = -
Transport wander West = +
