Testing Tuesday: IFR Fuel Requirements

The correct answer is b: fly to the alternate, and fly thereafter for 45 minutes at normal cruising speed.

14 CFR Part 91.167 & 91.169 lay out requirements for IFR pilots relating to alternate airports and flight plan filing. Specifically in the case of this question you need to remember the 1-2-3 rule:

An alternate airport is required to be filed unless the airport of intended arrival has a published instrument approach procedure and during the time from 1-hour before to 1-hour after the planned ETA (“1” from the 1-2-3 rule), the weather forecast at the airport of intended arrival has a ceiling of at least 2,000 feet AGL (“2” from the 1-2-3 rule) and visibility of at least 3 statute miles (“3” from the 1-2-3 rule).

If the airport of intended arrival does not meet all of the items in the 1-2-3 rule, then an alternate airport must be filed.

Additionally, under IFR, the minimum fuel requirement is to plan for landing with 45 minutes minimum fuel remaining in the tanks (based on fuel burn at cruise speed).

So to answer this question, we first check the weather: at the estimated time of arrival (within 1-hour before to 1-hour after), the ceiling is forecast to be 1,500 feet (less than 2,000 feet), and the visibility is forecast to be 3 miles (the minimum from the 1-2-3 rule). Because the ceiling is forecast to be lower than the 1-2-3 rule dictates, an alternate is required.

Since an alternate is required, the minimum fuel requirements are to calculate enough fuel to fly to the airport of intended landing, then to the alternate, then for an additional 45-minutes at normal cruise speed. Which brings us to answer b, above.

Now lets talk about realiuty instead of the FAA minimums. In reality, you will most likely not go to your alternate unless you cannot get into your planned airport. So you;ve spent your fuel to get to the planned airport, but you will go missed and possibly enter a hold before you are cleared to either try again at your original airport, or to go to the planned alternate. Either way, you have burned into your 45-minute reserve before you ever even get a chance to start on your way to the alternate. Many pilots choose to carry much more than the required minimums – at least 60 minutes reserve or even 90 minutes.

Fuel reserves are a great example of “legal” vs. “safe.” Hard IFR is the last place you want to be concerned about whether you really have that whole reserve you planned on (did you have more headwind – or less tailwind – than you thought you would?). Set yourself a higher personal minimum (I’d suggest double what the FAA requires – so 60 minutes for day VFR and 90 minutes for IFR or night VFR), don’t let yourself eat into it! Plan on landing – every time – with that extra fuel all still on board. Think ahead and be a pilot, not just another person who holds a certificate.