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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)

Hawker445 09-30-2019 09:38 PM

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.

usmc-sgt 10-01-2019 01:54 AM

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-
Youíre holding and have 10000 lbs on board. Itíll 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.

HIFLYR 10-01-2019 04:43 PM

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

Bmaggiori 10-02-2019 08:22 AM

You can use the QRH

joepilot 10-02-2019 06:10 PM


Originally Posted by usmc-sgt (Post 2896259)
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-
Youíre holding and have 10000 lbs on board. Itíll 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.

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

vessbot 10-11-2019 10:02 AM


Originally Posted by usmc-sgt (Post 2896259)
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-
Youíre holding and have 10000 lbs on board. Itíll 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.

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.

Blackhawk 10-17-2019 11:14 PM


Originally Posted by vessbot (Post 2902096)
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 Iím number 1. Got cleared direct to the final course and made it in. Took over 9000í to get the airplane stopped. Aircraft after me landed and also called braking poor-nil so they closed it again.

senecacaptain 04-05-2020 06:23 AM


Originally Posted by DOERING (Post 3024031)
Wow! 9000í of RWY before stopping! Must have seemed like forever to stop.

nice reply to a 2019 post

AirbusPTC 06-10-2021 06:46 AM


Originally Posted by joepilot (Post 2897344)
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 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

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.

rickair7777 06-10-2021 07:19 AM


Originally Posted by AirbusPTC (Post 3248001)
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.

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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