Final Reserve Fuel

Today’s #dispatch #docutainment‘s dedicated to a special guest: Final Reserve Fuel! Established in @icao Annex 6, #aviation authorities worldwide have followed suit in their regulations.
the #icao requirement is actually simple:
– fuel to cover 30 min of holding (for turbine engine planes, 45 for pistons)
– at holding speed & expected #airplane weight
– in 1500ft at ISA conditions
– overhead the alternate #airport (or destination if operating without ALTN).
No complicated formula.
No load of confusing “if”s and “when”s.
No need to discuss which weather, altitude, speed to apply.
Its simplicity outlines its importance (swipe): all #flights get their 30 mins, be it MUC (A), MLA (B) or MEX (C).
no matter the #plane type or flighttime, or if our #flight is a super short haul (MUC-FRA eg) or grown-up longhaul (MEX-FRA).
With calculation conditions this standardized, for same plane, airport and weight, you’ll always get the same amount of “holding fuel” (as it’s also called, D) – irrespective of route.
It’s also independent of weather fluctuations, as we apply ISA for calculation (international standard atmosphere – a model assuming fixed temperature / pressure per altitude, zero wind).
Also, regulation clearly states FINRES is a “protected” fuel: its full amount has to be available even after a diversion (so, “remaining fuel” after landing at your alternate must be at least FINRES, E).
It differs from other reserve fuels in some more ways.
contingency or alternate fuel may be reduced subject to special authorization and favorable conditions — not the case here.
Also, despite being called a “reserve”, it’s practically not supposed to be touched in flight: a #pilot’s even expected to declare a fuel emergency once it’s clear they will be below FINRES in their plane’s tanks after landing – likewise, the definition for a “safe landing” includes a remaining fuel “at or above Final Reserve”.
All of that makes FINRES kinda the “Queen Mum” of fuel reserves – and a true asset for #safetyfirst: you’re not supposed to burn it under normal conditions.
But you could – as a very last 30 min straw.

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