Alternates & decision point

033 Flight PlanningChapter 3

Alternates and special fuel procedures extend range by reducing mandatory reserves where regulations allow — but only when specific weather and aerodrome criteria are met.

Adequate vs suitable aerodrome

Definition — Adequate aerodrome

Considered satisfactory for the aircraft type, including ancillary services (handling, fuel, etc.).

Definition — Suitable alternate

An adequate aerodrome where weather reports indicate it will be safe to land at the expected time of use.

When is a destination alternate required?

Key fact

Minimum one alternate for IFR flights, unless:

• Flying to an isolated aerodrome (PDP procedure applies), or
• Remaining flight time under 6 hours and two runways available at destination, with ceiling above 2000 ft (or circling minima + 500 ft) and visibility above 5 km within ±1 hour of ETA

Exam trap

The 6-hour and two-runway exception requires both conditions together with the weather minima. Do not apply it to isolated aerodromes — they use PDP, not the standard no-alternate rule.

Decision point procedure (DP)

Definition — Decision Point Procedure

Also called RCF (Reduced Contingency Fuel) procedure. Reduces contingency fuel to extend range or increase traffic load. Contingency is calculated only from the decision point to destination (or alternate path), not for the whole trip.

Key fact

Use when an alternate lies beyond destination — you fly toward destination via a decision point, then either continue to destination or divert to the alternate. Increases maximum range by reducing mandatory reserves.

RCF-1 — continue to destination via DP

Component	Coverage
Taxi fuel	Full
Trip fuel	Departure → destination via DP
Contingency	DP → destination only
Alternate fuel	As required
Final reserve	Full
Additional fuel	If required
Extra fuel	PIC discretion

RCF-2 — divert to alternate via DP

Component	Coverage
Taxi fuel	Full
Trip fuel	Departure → alternate via DP
Contingency	DP → alternate only
Alternate fuel	As required
Final reserve	Full
Additional fuel	If required
Extra fuel	PIC discretion

Formula — Decision point fuel — choose greater sum

RCF-1: Trip (dep → dest via DP) + Contingency (DP → dest at 5%)

RCF-2: Trip (dep → alternate via DP) + Contingency (DP → alternate at 5%)

Plan using the greater of RCF-1 or RCF-2.

Formula — DP trip and contingency

Trip fuel = Distance ÷ GS × fuel consumption

Contingency = (Distance DP to segment end ÷ GS × fuel consumption) × 5%

Exam trap

Under DP, trip fuel to destination is calculated via the decision point, not direct. Contingency is at least from DP to destination — never the full-route 5% unless that is higher than the DP segment rule allows.

Pre-determined point procedure (PDP)

Definition — Pre-Determined Point (PDP)

Formerly Last Point of Diversion. Used when it is impossible to carry enough fuel to fly from destination to alternate — typical for isolated aerodromes. A point is chosen where the decision to divert or continue is made.

Key fact

The last possible point of diversion to an ERA is used as the PDP. Required: contingency from PDP to destination and additional fuel per isolated-aerodrome regulations.

PDP-1 — continue to isolated destination via PDP

Component	Notes
Trip fuel	Departure → destination via PDP
Contingency	A → B (PDP to destination)
Additional fuel	Pistons: greater of 2 h cruise, or 45 min + 15% flight time — whichever is less
	Turbines: 2 hours flight time (includes final reserve concept)

PDP-2 — divert to ERA/refuel via PDP

Component	Notes
Trip fuel	Departure → alternate/refuel via PDP
Contingency	A → C (PDP to alternate path)
Additional fuel	Pistons: 45 minutes
	Turbines: 30 minutes holding speed

Formula — PDP fuel planning

Choose the greater of PDP-1 or PDP-2. Planned final reserve may be subtracted from calculated additional fuel (final reserve is included within additional fuel for isolated procedures).

Additional fuel for isolated aerodromes (standalone questions)

When questions ask only for additional fuel (ignore DP/PDP trip builds):

Engine	Destination (isolated)	Destination alternate
Turbine	2 hours cruise consumption	30 minutes hold
Piston	Lesser of: 45 min + 15% cruise time (TOC–TOD), or 2 h cruise	45 minutes only

Exam trap

PDP = isolated aerodrome / cannot reach alternate after destination. DP (decision point) = reduce contingency to increase payload on normal routes with a distant alternate. Do not confuse the acronyms or fuel builds.

ERA and contingency reduction

Key fact

With ERA available, contingency may be reduced to 3% of planned trip fuel instead of 5%. ERAs support en-route diversion and interact with contingency minima — always check whether ERA availability is stated in the question.

Weather impact on alternate planning

Key fact

Snow showers causing runway contamination are most likely to force alternate planning in fuel log questions — compared with rain, fog, or mist alone.