In-flight replanning

[disininer]

hi there.
Please I need some help here.

So yesterday we were flying this ultra long flight ( +12h) and 4 hrs from destination we realize we are quite tight on fuel and destination TAF is horrendous in terms of visibility. As we prepare a plan B we notice the favourite alternate ( less distance ) has less than ideal conditions, as well visibility forecasted to be marginal. So different strategies are discussed and one of them is,...what if we proceed to this alternate , again, not very promising TEMPO wx conditions although METAR is still acceptable. My question here is, if we decide to fly to this planned alternate ( from dispatch) directly, at some point, without trying the original destination, is this considered inflight replannig therefore, all considerations for new alternates and planning minima apply? I think the answer is yes, but... it was the spark of a very vivid discuasion we had in the cockpit me and 2 other colleagues.

Thanks in advance

[eckhard]

I would say that you consider planning minima prior to dispatch. Once airborne, normal minima apply.

[disininer]

I would say that you consider planning minima prior to dispatch. Once airborne, normal minima apply.
I mean yeah, your destination alternate mínima are the charts mínima once in flight no discussion about that. This is not what I'm posing here though. In other words what difference does it make to plan to go to a completely new enroute destination or go to your destination alternate in terms of replanning. I think none.

[BleedingOn]

I would say in that situation you are still diverting from your flight planned destination, you’re not re-filing for a new destination. So no need to have alternates from your diversion airfield selected (otherwise one of them might be your original destination, which would be a little odd). It would always be sensible to have a plan B in the conditions you specify though, of course.

[disininer]

Well, you're voluntarily changing your destination which is precisely the definition of ICAO for in-flight replanning. Whereas when you go to your alternate after having been unsuccessful you're forced to go to your alternate. Imagine there is literally no way you can land at your destination and you know this well in advance. So you decide to go to your alternate. Distance to your second alternate ( if needed when you initially planned) renders it impossible to make it there, which is precisely what we were discussing airborne the other day. Now, by choosing this "declared" alternate, are you commiting to land?

[rudestuff]

You always have to commit to something in the end! You don't need to go all the way to minima at your destination before committing to the alternate.

[FullWings]

“In-Flight Replanning” referred to a scenario where you couldn’t legally dispatch as you would arrive at destination with less than the required amount of fuel, because for whatever reason(s) you couldn’t get any more on. To get round this, you could file to somewhere closer that was legal, in the expectation that direct routings, optimum levels and the relaxing of in-flight fuel criteria as you got closer in time and distance to where you actually wanted to go would allow you to carry on, but if that wasn’t possible you would tech stop somewhere convenient near the end of the flight.

This is different from the original scenario because your filed and intended destination are the same in that case, whereas with this method you are changing your destination in-flight if/when it becomes possible.

We don’t do this any more so I don’t have any up-to-date info but I presume some carriers might still utilise this in extremis.

[disininer]

You always have to commit to something in the end! You don't need to go all the way to minima at your destination before committing to the alternate.
So your answer would be you don't need any other considerations when proceeding to your alternate. Being above minima would be enough although the decision is been made long before TOD. What if the decision to proceed to the alternate was other but not the impossibility to reach your original destination?

[AerocatS2A]

So your answer would be you don't need any other considerations when proceeding to your alternate. Being above minima would be enough although the decision is been made long before TOD. What if the decision to proceed to the alternate was other but not the impossibility to reach your original destination?

Once you're airborne, the overriding requirement is to be able to land somewhere with fixed reserves in the tanks. If you've planned to fly to B, the passengers want to get to B, the company want you to go to B, the next flight for you and the aircraft commences from B, it's not inflight replanning if you decide to divert to C without first proceeding to B. It would be inflight replanning if you planned to B but the passengers want to get to C, you want to get to C, the company wants you to get to C, the next leg commences from C, and on your way to B you replan to C. In that latter case you would need to have additional reserves at C over and above the basic fixed. As FullWings says, this is done in cases where you can't plan A to C because you can't take enough fuel, so you plan A to B then when you get to your inflight decision point you recalculate the fuel to continue to C holding D as an alternate (if required). The idea being that you won't have burnt your contingency fuel, you may have saved some fuel with direct tracking and maybe you have some left over taxi fuel, also from that point you don't need as much contingency fuel.

[revida]

Hello there! Your instincts were correct in considering in-flight replanning to be in effect as soon as you decided to direct yourself directly towards one of the planned alternate destinations rather than trying your original target destination first. All considerations regarding new alternates and planning minima would come into play here, thus prompting lively debate amongst your colleagues - this should always provide greater insights. It's always valuable having multiple perspectives present to ensure a thorough grasp of a situation.

[disininer]

I understand. To be honest I don't think this inflight replanning expecting less consumption or more favourable winds, being able to use contingency and so on, is something we have ever planned on to get somewhere. Our planning strikes me as quite accurate if not vaguely optimistic and rarely we end up in the plus side. Sounds interesting though. And the going to the alternate with your final reserve plus whatever is left extra I guess it's a matter of picking the right alternate then. Seemingly, if we had changed the destination alternate, that would be an inflight replanning though.

Anyway, thanks to you all for the responses. It's always a pleasure to learn something or relearn something I must say