Destination alternate UK - interesting scenario

[Wilton Shagpile]

OK, say you're planning to depart to an airfield with a single, short runway, which for performance PLANNING (factored) purposes is long enough when dry but not when wet. However, your raw (un-factored) performance allows you to land under either condition.


Your destination is WET and the forecast indicates rain for your +/- 1 hour arrival so will still be wet when you get there.


Can you still depart provided you have two alternates, then when you get to your destination, land anyway using your un-factored performance?


I always thought this was the case but can't find a reference document for it. Usual obvious caveats apply about this being a good idea or not but it's just the rules I'm interested in.


Thanks.

[B737900er]

From a planning point of view you have to take inconsideration of all factors/margins that could affect you landing there. The planning minima is more stringent.

If you cannot meet those requirements then 2 alternates is required that both meet the required planning minima.

If your landing on a wet runway I suggest using Good braking action figures as this builds a 15% margin.

If you can't land with that, I would consider building in some margin.

[Johnny F@rt Pants]

Simple answer, change your destination to one close by that you can fit into at the planning stage. Once en route you are then permitted to change destination to your original and use the performance in-flight (un-factored) calculations to get you in.

[B737900er]

Johnny - Would that require an inflight re-clearance?

[Phileas Fogg]

Johnny - Would that require an inflight re-clearance?

I think it's called a "diversion".

I think what Johnny means is that you re-flight plan with one of your alternates as your destination, with your original destination being an alternate, and then divert to your original destination.

Back in the 80's I worked for an operator where, of a summer weekend, we would have a fleet of some 20 aircraft destination JER/GCI from all parts of UK, Flow Management had recently introduced flow control from all UK airports except south coast airfields, SOU being one of our bases.

After some 3 hours or longer of waiting on a telephone for a regulator to answer we re-flight planned the entire fleet destination SOU with JER/GCI as alternates and as they neared SOU the entire fleet diverted to JER/GCI.

The Civil Supervisor called us up and accused us of cheating, we explained that we couldn't get slots, he told us to phone the regulator, we told him the regulator won't answer the phone, he explained that was because the regulator was busy, we explained "so are we" :)

[B737900er]

Phileas - A very interesting story you told there, I like hearing stories from the veterans.

Problem with diverting as you suggested, is that if it was an international/intercontinental flight your passengers and bags won't be able to get off unless the flight is unable to continue. It would also be interesting to hear the conversation with ATC into why you decided to randomly divert from your FPL. Hence why I asked if a re-cleareance would be needed or advisable.

I think us pilots look for a reason not to fly, I think the posters question is an excuse to say "I'm not flying because we can't get in".

[McBruce]

I believe this used to happen more frequently in days gone by with older equipment, less range. If your planned to tech-stop due to planning performance reasons with your destination as an ALTN, and you determine you can fly to your original destination inflight then it made commercial sense, I believe ATC where highly familiar with the process and could probably sniff out the suspects easily.

[Rwy in Sight]

Not a pro but I think the AF477 had filled as destination Bordeaux and Paris as the real destination...

[Phileas Fogg]

I believe ATC where highly familiar with the process and could probably sniff out the suspects easily.

They certainly sniffed out those declaring fuel emergencies to, perhaps, queue jump ... These days they need to declare, is it, a PAN or MAYDAY!