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-   -   Quick way to determine holding time for fuel? (https://www.airlinepilotforums.com/technical/124418-quick-way-determine-holding-time-fuel.html)

AirbusPTC 06-10-2021 02:13 PM


Originally Posted by rickair7777 (Post 3248024)
There's been debate over the years due to the language (slightly vague IMO) in this section. Also debate or "IFR" vs. "IMC".

But I think it's safe to say that you're good with your dispatch planning up until you become aware that you're going to come up short on reserves, and then you should divert somewhere else or stop and get more gas before continuing.

In many cases, by the time you realistically know you're short on gas, the destination or alternate are going to be the nearest/quickest diversion points anyway.

Interestingly enough, the FAA defines IFR and IMC but not specifically IFR conditions, which is what they use in the regulation I quoted (91.167). IFR conditions must be deduced from the combination of the definitions.
FAA definitions:

Instrument flight rules (IFR) means rules governing the procedures for conducting flight under instrument meteorological conditions (IMC) instrument flight.

Instrument meteorological conditions (IMC) means weather conditions below the minimums prescribed for flight under Visual Flight Rules (VFR).

At any rate, the intent of the regulation is that we plan to have at least 45 minutes of fuel in the tanks when we land at the Alternate. When do we plan this? Sure during preflight, but also during the flight, usually while flying the hold. We must leave the hold when the fuel equals the amount to fly from the Hold to the Destination and then on to the farthest filed Alternate. Then be able to fly 45 minutes after that at normal cruising speed.

rickair7777 06-10-2021 02:19 PM


Originally Posted by AirbusPTC (Post 3248224)
Interestingly enough, the FAA defines IFR and IMC but not specifically IFR conditions, which is what they use in the regulation I quoted (91.167). IFR conditions must be deduced from the combination of the definitions.

Yeah that's part of the problem with this reg... if you wanted to split hairs. Better to just stay conservative.

Duffman 07-14-2021 07:52 PM


Originally Posted by rickair7777 (Post 3248229)
Yeah that's part of the problem with this reg... if you wanted to split hairs. Better to just stay conservative.

Maybe it was an assumption, but I always figured if an alternate was required (123 rule), then the reg applies. Same applies to a second alternate (enough gas to reach the furthest alternate, not both). How could the reg possibly legally require an alternate, but not require having enough gas to reach it? But I get that the FAA is driven by strict, bureaucratic interpretation of the law that'd defy any common sense bias.

dckozak 09-12-2021 11:51 AM

Looking back at the OP's question, quick and easy inflight planning, using an FMS for a tactical problem is something that could be better taught, depending on where and who has provided your training and guidance for your current jet. To the point of most posters responding to the OP, the FAR's provide a pretty clear plan for dispatch, re: fuel required, but leave a lot to the interpatation of how en route to decide how much is acceptable for a divert. The FMS that most of us use, I believe, has several functions which will compute something but none can tell you how much fuel you should have when you finally touch terra firma. The old adage, "Sh!t in, Sh!t out" regarding computations, absolutely applies here. Aviation is full of variables that the Administrator, weather office and company flight standards can't all provide guidance for. Sometimes you just have to point the jet in the right direction and use your gut as to how long you can loiter before landing somewhere you, your passangers, or your employer would rather you didn't. Thats why they pay us the big bucks.


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