Quick way to determine holding time for fuel?
 

Maybe i'm thinking too hard but what's a sure fire way to figure out the longest time you can be holding for? In terms of jets with an FMS


I've never gotten into a situation where I've told atc "we have XXX minutes to hold or else".

My thought is take the fuel left at destination, plugging it into the box and seeing how close that brings me to minimum fuel at destination and take the difference and use math by the fuel flow.

Most FMSs will calculate it for you by changing the EFC time. If not...

Add:
- fuel required to get from the hold to destination
-fuel required to get from destination to alternate
-at least :45 minutes after the alternate.
-10% for error

Subtract that from FOB.

So-
You’re holding and have 10000 lbs on board. It’ll take you 2000lbs to get to your destination and another 2000 to get to the alternate. Min fuel is 4500lbs.

2000+2000+4500= 8500lbs + 10% = 9350lbs.

You have 650lbs you can hold with which in my jet is about 6 minutes, or not very long.

In our FMS you can input the fuel you want to land with at destination or the alternate. The FMS then displays the bingo time based upon the routing winds etc imputed into the FMS . I always back it up with mental math using average burn rate snd time to go to either decision

You can use the QRH

First, nobody will argue if that is the calculation that you choose to make. However you make it sound like that is the minimum REQUIRED by the FAA.

The 8500 would be a dispatch requirement, the 10% is your own chosen idea, although it would be required for some Class II routes internationally.

The 45 minute reserve is strictly a dispatch requirement. If you find that you need to burn it enroute, the FAA has no problem with this. I have had to burn substantially into the 45 minute reserve (no alternate) during a no notice FAA enroute check, and the check airman did not say anything, although he knew exactly how short we were.

Joe

Pen and calculator answer: this.

FMS answer, without knowing your particular one and its special tricks: keep putting in fake EFC's until your arrival fuel at the alternate is what you want.

Other thoughs: yeah the 45 minutes is not required once you've launched, but it's a good starting point and personally I wouldn't go below it without a seriously good set of circumstances lining up, like a few good alternates in the same direction, etc. Conversely you may decide to bump it up if there's only 1 alternate, its weather is getting worse, other diversions are already saturating its arrival rate, etc. Our you wanna give yourself fuel for a missed and second attempt at landing at the destination.

Yeah, whenever I was holding I figured the 45 min reserve plus 10% in case I messed something up. Then had the FO back me up.
I once was holding for DTW during a snow storm, DTW closed down CLE my alt. Looked around, FNT was closer so I changed the alt to FNT. Sweet. Now I had tons of time. ATC comes over and announces FNT closed. Crap. Back to CLE. As soon as I tell my dispatcher CLE closes down. Crap. Now what? I talk to dispatcher- PIT. Son. Of. A. Biscuit. I have to go now. Just after I tel ATC I have to bug out he says DTW is open and I’m number 1. Got cleared direct to the final course and made it in. Took over 9000’ to get the airplane stopped. Aircraft after me landed and also called braking poor-nil so they closed it again.

nice reply to a 2019 post

Hmmm. But what about: 14CFR 91.167a) No person may operate a civil aircraft in IFR conditions unless it carries enough fuel (considering weather reports and forecasts and weather conditions) to -

(1) Complete the flight to the first airport of intended landing;

(2) Except as provided in paragraph (b) of this section, fly from that airport to the alternate airport; and

(3) Fly after that for 45 minutes at normal cruising speed.

That's not only a "dispatch" requirement right? That's a requirement to OPERATE in IMC period.

There's been debate over the years due to the language (slightly vague IMO) in this section. Also debate on "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.