Alternates

Question 1

What is the mnemonic?

Answer 1

1-2-3 / 1500 + 2 / 2000 + 3 / MMOISTRS / 20144

Question 2

1-2-3

Answer 2

You ALWAYS need an alternate, UNLESS…

The basic 1-2-3 rule: 1 hour before to 1 hour after ETA, ceilings 2,000 feet or more, vis 3 SM or more.

Question 3

1500 + 2 / 2000 + 3

Answer 3

For flag operations:

Use the standard ETA +/- 1 hour, but use the following ceiling and visibility values:

• vis: 3 miles (or 2 miles more than lowest approach mins, whichever is greater)
• ceiling: 2,000 feet (or 1,500 feet above lowest approach mins, whichever is greater)

If these requirements can be met, no alternate required.

Question 4

M (1st)

Answer 4

Marginal:

• Generally, the weather is considered “marginal” if it is within 100 OR ½ of the applicable minimums for that airport.
• So if the weather is marginal based on Cat 1 mins at destination
• AND marginal based on DERIVED mins at 1st alternate
• then 2nd alternate required.

Question 5

M (2nd)

Answer 5

Method 2 Engine failure at cruise, clear all obstacles by 2,000 feet, 5 SM either side of route — but if failure occurs before reaching cruising alt, we need to be able to return to departure airport, or divert to a takeoff alternate using Method 1 calculations.

Question 6

O

Answer 6

Offline charters

Question 7

I

Answer 7

International

When flight time exceeds 6 hours

Question 8

S (1st)

Answer 8

Severe icing

Question 9

T

Answer 9

Thunderstorms

Question 10

R

Answer 10

RNAV only

Question 11

S (2nd)

Answer 11

Supplemental

Question 12

20144

Answer 12

20144

• destination = not less than ½ the vis for the expected approach
• 1st alternate = not less than ½ the DERIVED ceiling AND vis
• 2nd alternate = at or above DERIVED mins
• Provides relief only from CONDITIONAL statements such as TEMPO, PROB, or BECMG. Main body must still indicate that weather will be at or above applicable mins when the flight arrives.
• Only applicable to domestic operations. Not available for Flag or Supplemental operations.

Question 13

What are derived alternate weather minimums?

Answer 13

• Use the 1 Navaid / 2 Navaid rule
• If the airport has 1 navaid, add 400’ to DA / MDA, and 1 SM to to the visibility mins.
• If the airport has 2 navaids, add 200’ to DA / MDA, and 1/2 SM to the visibility mins.
• “Highest of the lowest.”
  
  • Pick the two suitable approaches with the lowest mins. Add the 200’ to the highest of those two DA/MDAs. Add the 1/2 SM to the highest of the two visibility mins. They will not necessarily be the same approach — could be the ceiling from one approach, and the vis from the other.
  • For the 1 navaid rule, there needs to be at least one straight-in non-precision approach procedure, or one Cat 1 precision approach, or a circling maneuver from an IAP.
  • For the 2 navaid rule, there must be at least two operational navaids, each providing a straight-in approach procedure, to different suitable runways.

Question 14

Method 1 vs Method 2

Answer 14

Method 1:
If an engine ​failure occurs anywhere from​ V1 to the destination, the aircraft’s net altitude capability will clear all obstructions 5 ​SM on either​ side of the intended route​ by 1,000 feet until reaching the destination.

Method 2 (AKA driftdown):​
If an engine failure​ occurs at cruise altitude, the aircraft​ will be able​ to​ divert​ ​to at least one suitable airport (driftdown alternate) from flight planned cruise altitude and by the aircraft’s net ​driftdown altitude​ will clear all obstacles 5 SM​ on either side of the route​ of flight​ by 2,000​ feet until reaching the ​diversion airport. If the engine failure occurs before reaching cruise altitude, the aircraft must be able to return to the departure airport or a suitable diversionary airport using Method 1 calculations.