Diversion planning and execution

[Britjet]

I thought I would start a new thread in response to some requests (eg Holger!) to give guidance on how to plan, manage and execute diversions.
This can be a big subject and I'm sure it could run and run - so here goes!
(All - please feel free to contribute..)

I'll start..:-)

I would say that there is no fixed method. A diversion can come with plenty of warning, or none at all. It can come as a  short or long sector, with different priorities for each. It can come due to technical, weather or other issues, and these will affect management of the diversion.

A diversion can be easy, maybe guided by positive ATC, or alternatively require advanced and significant FMC input.


What are always involved, are..

Increased workload
Increased Communication and Resource Management
And, quite often, infrequently experienced motor skills - eg Go-Around etc.

The NG FMC ALTN capability tempts us to go for it as an exercise!
Having used the ALTN pages for real, all I would say is that these new toys can encourage "heads down" and automation slavery - something I have never been a fan of - but..
As a PSX  exercise - an impromptu diversion tests your (possibly new-found!) skills as much as anything and can be quite self-revealing. It's a great leveller. I claim no expertise in this department!

OK guys -go!

Peter.

[Britjet]

And here's my second thought...

KISS!
(Keep It Simple, Stupid)

Peter

[Will]

The most immediate types of diversions are things like fire, or the captain reporting crushing substernal chest pain and then losing consciousness. (I once heard that an AAL jet went from cruise altitude to a landing in something like 6 minutes after a member of the flight crew had a heart attack, and the healthy pilot landed literally ASAP to get him help.)

In my flying career, I never had one of those.

My diversions were almost all due to weather, and the diversion itself ended up as the final decision along a long path of problem-solving. Like for example, being dispatched one night from St. Louis to Joplin, MO, knowing that there were convective SIGMETs and a good chance of thunderstorms in the area. Sure enough. embedded storms were gathering around Joplin by the time we got close, and radar pained them as a solid line between us and our destination. But things looked softer to the east, so we flew parallel to the line until getting over Tulsa, OK. At that point, we were able to turn back west after going south of the line, but by now we were also south of Joplin. More storms kept us cut off from turning north, so this time we skirted the line westbound until Springfield, MO. It was at that point that fuel started to get low, and Joplin was reporting lighting, and neither ATC nor our own radar showed any real hope of making it back in. So we decided to just land at Springfield. It took about an hour of extra flying from the time we initially started to turn away from the weather to finally getting on the ground at Springfield.

My point in telling this story is that the diversion itself was always on our mind as an option (back to St. Louis? Tulsa? Springfield? Oklahoma City? Somewhere else?) but we didn't decide to actually divert until we'd become pretty certain that we weren't going to make it to our destination. The whole event was frustrating for our passengers, who were put on a chartered bus to make it to Joplin by morning, but from the flight deck, there was nothing rushed or tense about the situation. And diverting was just like flying an approach into any other airport, except that we had to park at an unfamiliar gate and we went to a crew hotel we'd never seen before. (And although we had a company station there, it wasn't an airport that my aircraft type flew into, so the ground crew were a little uncertain about how to service us. Where do I plug this thing in? How do I open the baggage door? That kind of thing.) So we saw some new things, but nothing particularly challenging or hurried. And at no point was anything unsafe, as we kept a good eye on our margins (from the weather, and from a fuel standpoint).

More recently, I was flying as a passenger to Beijing and the weather was rough outside. I asked the crew afterwards if weather ever kept them from getting in, and they said that was frequent - not because the weather is particularly bad there, but because Chinese ATC is not equipped to handle high traffic volumes so they keep the aircraft spaced far apart. That slows everything down, and when weather interferes, diversions are common. They said they frequently landed at Shanghai until Beijing was open again.

[localiser]

Time available will affect how many things you can cover.

Communication is a huge part of the team effort. Not only between pilots on the flight deck, but also between pilots and cabin crew, operations, ATC and potentially other agencies as well. In the event of a medical diversion on a passenger flight you will probably be passing info gathered by the crew on a special form over HF (satcom if you're lucky) to nurses and doctors at Medaire who provide remote medical support and can advise on where and if to divert.

They will be able to advise you on medical facilities but won't necessarily be aware of other operational conditions. They might suggest a diversion to St Johns CYYT, but the weather may be below minimums and so on.

You may not always be faced with an ILS. You might need to do a cold temperature altimeter correction. An overweight landing performance calculation, or a fuel jettison. Get the weather. What are your minimums? Once you've landed, can you take off again in the same weather? Do they have fuel? Do they have a tow bar? MSA?

Of course much of this will be taken care of by handling agent contracts, but sometimes they can still be caught short. Your communications would normally also involve operations, cross checking with them where they want the aircraft, hotels availability if you're going in with a tech issue or risk going out of hours... lots and lots of stuff.

And then there's the small issue of telling 400+ people that the plan has changed!

Plenty of stuff to think about as you're sailing overhead with time on your hands to play "what if?"  Once you've visualised situations it reduces your workload too, because mentally you've been there before.

Programming the FMC I'd say depends.  If it can give you good information that will aid your decision or at least getting a sensible descent profile will take a load off. I think in the event of a weather diversion if your're expecting not to get in to your destination its not a bad idea to have something in RTE 2 that you can just activate and execute, which you can talk about in the approach briefing that's also a way you can reduce workload. Probably this has been flagged in the preflight briefing and ops have a plan going before you're even taken off.

Over to everyone else.... Looking forward to getting some interesting new thoughts and ideas!

[Britjet]

Excellent thoughts all. I think "localiser" has covered loads of stuff there that most of us have sat there at 3am dreading having to do - but thinking about nonetheless.
From a single-pilot point of view, it is important to keep the structure of the sector intact. By that I mean - treat it like a whole new sector - even if it is just a go-around and repositioning for a further approach. After the go-around - do the after take-off checks - then the rest of the checks in the normal order. This will prevent you from, for instance, flying the diversion accidentally with the gear down!

If you are multi-crew - one pilot must have the sole task of flying the aircraft, and probably handling ATC calls as well. It doesn't sound like much - but once you go heads-down your situation-awareness "bubble" contracts.

The bottom line is that the aircraft must be safe at all times, and not going anywhere that is unrecoverable. It doesn't have to be pretty - or something that would pass a line-check, but if you get the basic monitoring skills and workload management right the rest will tend to follow.

Peter

[Holger Wende]

Hi Peter and all,

Thanks for picking up the topic so quickly and for sharing your insights 

Some of my questions about diversions are:

For the preferred/planned alternates would you typically get a route uplink to the alternate airport or do you have them on board already for easy access?

For rather short-term or last-minute diversion decisions (no emergency) does ATC normally give you the new route as clearance as in this video: https://www.youtube.com/watch?v=qRZunXY_7dA at time 4:45 ?

I guess in cases of emergency you would try to go as direct as possible?

Would you use ROUTE 2 to enter a diversion route or just "append" it to ROUTE 1 with a disconenct and up-select the first diversion route fix once you are "happy" with the diversion route? I did not play with the NG FMC ALTN feature yet, so the answer might be in the NG FMC manual.

And what is the procedure on the classic non-NG FMCs?

Thanks, Holger

[emerydc8]

For rather short-term or last-minute diversion decisions (no emergency) does ATC normally give you the new route as clearance as in this video: https://www.youtube.com/watch?v=qRZunXY_7dA at time 4:45 ?

Yes. When the vector heading was issued at 5:05, that's when I would have gone to the RTE page and installed the diversion airport (PHL). At less-busy times, you are more likely to get a more direct routing than the one issued in the video. At least get the new destination airport in so you can select an approach.

Great subject, Peter. There are so many issues that could be raised about diversions that this string could go on for 20+ pages.. One pilot raising one issue could cause another pilot to raise five more points about that same issue and so-on. I suspect and hope additional points will be made about the points I'm raising here.

Watching that video again, two things came to mind regarding the diversion routing: (1) It's almost never the same as the route on the flight plan, and (2) You almost never get to climb to the lofty altitude the computer flight plan lists. The flight plan is almost always more optimistic about burns and altitudes to alternates, so they can minimize the fuel required for dispatch. For instance, in the video, IAD was the first alternate and I would bet that the flight plan had them climbing to a jet route and/or more direct route versus the circuitous victor airway clearance that was issued to get to PHL. It probably would have been even worse going to IAD.

If the diversion was due to weather at destination and you are heading to your alternate, does your alternate have similar weather? As Peter said above:  treat the diversion like a new sector. It's a good idea to start thinking about a back door to your alternate as well, in case the weather goes down or braking action closes that airport. In a hub/spoke system, there may be several dozen company flights heading to the same airport as dispatchers like to use common alternates so they don't have to check the weather and NOTAMSs at too many airports. Holding at the alternate may not have been anticipated when you first set out to your alternate but will that change if a dozen company flights are also heading to the same diversion airport in front of you? If this is winter, how many usable (plowed) runways are there at your diversion airport?

If there is an extra crewmember, when within range of your diversion airport have that crewmember listen to the tower frequency and see if flights are getting in and what the conditions are like. A bit too far away and can't hear the tower? Press and hold the radio tuning switch (VHF R) to remove the automatic squelch. That's going to be a preview of what the new ATIS will be as you get closer and gives you the information in real time, more current than the official report and certainly fresher than your dispatch will provide you. Maybe you don't want to commit to that alternate after all, but perhaps another airport along the way. Remember, once you've committed to your diversion airport, your options to go elsewhere are significantly reduced as you burn fuel, unless the second diversion airport is along the way. If you are overflying another suitable airport on your way to you diversion airport, listen to the tower as you overfly to get an idea of what's going on down there.

Remember, there's reserve fuel on the CFP and there's usually a personal minimum fuel that most pilots like to land with regardless. Most pilots won't argue with dispatch prior to a flight that has you landing at your alternate with less than your personal minimums, but in practice that figure should factor into the decision on how long to hold at destination. Don't let the flight plan talk you into landing at your alternate with 10,000 pounds if you like to land a 744 with an absolute minimum of 12,000 pounds of fuel, (I'd start getting pretty concerned below 12,000). Don't stick around and hold at your destination if it's going to put you any lower. It looks like the LH crew decided to bug out before the 30 minutes they initially stated as well.  As I mentioned above, the flight plan is almost always more optimistic than reality, so you may not know the true fuel burn until you get the route and altitude and plug it into the box. This can't really be done until you've already made the decision to divert and get a clearance and altitude to your diversion airport. How would you like to have planned on a 6,000 pound burn to your diversion airport and landing with 12,000 pounds of fuel only to discover the burn is going to be more like 9,000? That definitely raises the pucker factor.

Jon

[Jeroen Hoppenbrouwers]

Press and hold the radio tuning switch (VHF R) to remove the automatic squelch.

a. New to me!
b. Would there be ANY reason to have something like this (i.e., no squelch) in PSX? Would it truly add range to the radio that would be meaningful?


Hoppie

[Martin Baker]

A big day of go-arounds and diversions in the UK. One BA 777 had 2 attempts at LHR then went to Frankfurt. Presumably they'd been extra cautious in the quantity of fuel upload. And at least one plane diverted and declared a fuel emergency. (An EZ which eventually landed at Manchester I gather.)

M

[emerydc8]

a. New to me!
b. Would there be ANY reason to have something like this (i.e., no squelch) in PSX? Would it truly add range to the radio that would be meaningful?

I don't know if it would even be possible for Hardy to model in PSX. It definitely adds range in that you can hear transmissions further away when you otherwise would not without holding the button down.

[Britjet]

In terms of fuel burn - a nice round number to use is 10,000kgs (22,000lbs) an hour.
If I may talk just in kg...

The minimum fuel required on landing (usually called reserve fuel) is in most countries equivalent to 30 minutes (EASA) holding at 1500ft at alternate, or destination if an alternate is not being used. This is usually a little less than 5000kg - so let's call it that.

You can quite easily work out how much holding fuel you have available before diverting by using 10,000 kgs per hour and just converting to minutes. For example, if I require 8,000 for the diversion sector, and I need 5,000 as a reserve, then my latest time to divert would be when I have 13,000kgs.
If I am entering my planned destination locality with 15,500kgs, then I have an "excess" of 2,500kgs - which equates to 15 minutes extra.
No need to spend much valuable time adding up all the single digits on the fuel plan - as Jon says - have extra for mother, and round up big time!

Peter.

[cavaricooper]

Peter- that's interesting.  I had many converstations with Mel (Ott) about just this stuff, and he always used a 12T figure for gross error checking/planning.  In truth, prior to FOC and PFPX I planned PS1 flights with pen and pencil using that amount.

Are you suggesting 10T as an in-flight calculation amount (eliminating T/O and climb segments and leaving only cruise, descent and GA) or as an overall gross fuel check figure?

Evolution is certain and this is very valuable information when it ALL hits the fan

Ta- C

[Britjet]

Carl - I think 10T is a reasonable amount for low-weight arrival and diversion. You would no doubt need more for general long-sector planning I guess..

Peter

[cavaricooper]

Peter- This simulator is my escape from the Salt Mines. and I do treasure it so.  Thanks for your input- every nugget is treasured.

C

[localiser]

Hi Carl,

10,000 kgs/hour is a rule of thumb really which you could say estimates the whole div sector, or indeed your entire trip fuel. In the cruise all engines operating, each engine is burning roughly 2,500 kgs/hour so it's a nice round number that's kind of good enough for a gross error check.

If you wanted to get a bit more precise (reduced contingency fuel flight plans leap to mind) you could take your Final Reserve fuel from the flight plan and divide that by 30 minutes. As it's based on a hold at 1,500' in theory it should be a fairly conservative value.

I see 3,900kgs frequently in this column!

4,000kgs / 30 minutes = 130kgs per minute ... then exactly as Peter said, you can work out what your extra fuel is and decide how much of that you want to use as holding fuel at destination, and how much you want to split it in order to dedicate it to any potential holding when you arrive at your alternate.

So that's in theory, but as Jon and Peter said, it's a good idea to view the plan with a bit of scepticism and be a pessimist when thinking about delays, weird scenic routings and so on.

Fuel is an interesting subject...... 

Strictly speaking, you won't get any priority from ATC if you tell them you're getting a bit low on gas. As everyone has their own personal minimums it's rather subjective and so it's a little bit your own problem - off you go to the hold.

However there is a definition of "minimum fuel" which you can advise ATC of once you're in that area. They still wouldn't be under any obligation to give you priority although I'm sure they'd do their best to help. It really would depend on their workload. There are a number of factors such as weather, traffic delays, number of runways, which you would take into account before essentially committing to the airport. Committing is not taken lightly. Once you estimate that any change to those conditions or clearance (like an expected approach time or miles to touchdown) would mean you would land with less than Final Reserve fuel pilots need to declare "minimum fuel". Note that in this case you're still estimating landing with that nominal 3,900kgs in tanks.

When the actual prediction is that you'll land with less than Final Reserve, this requires the call "mayday mayday mayday fuel" with the priority you'd expect.

[edit]
BTW - you mentioned Mel Ott. Do you remember in the late 90s and early 2000s he used to have a column on a website writing under the name of Cap'n Tarmack? (Not the ALPA articles, but flight sim articles). I can't remember the website but perhaps you do? I'd love to read some of those articles again but can't look it up on the waybackmachine as I don't remember where he was writing! Could've been microwings or simwings something like that. He used to sim using Project Magenta in those days.

If not then perhaps someone else remembers or still has them filed somewhere and would like to share?

[Ton van Bochove]

https://youtu.be/ZZrMNd8uikE

[Will]

That is a classic video! Things to observe:

+ The astounding resolution and image stabilization of the 4K GoPro Hero 8
+ The heavy clack, clack, clack of the 747's stick shaker as the aircraft approaches a stall in the landing configuration
+ Lessons in the proper way to salute a new beer
+ Dead-reckoning navigation equipment on the yellow bamboo shelves (globe and clock), probably removed intact from a Boeing 314 Clipper flying boat
+ The advanced land speeder technology, inspired by Star Wars

[United744]

I plan using 20000 lbs/hr of fuel, plus 10000 lbs for climb. If I'm light or flying short-range I reduce the figure to 15000 lbs/hr. I aim to have 20000-25000 lbs of fuel on-board at destination. I'll modify accordingly depending on how far away the furthest diversionary field is.

Not strictly real-world, but for oceanic, I plan for double engine failure, sub-optimal cruise out of the airway, and direct to the furthest diversionary field. If the fuel required is less than the fuel reqto the planned destination, I don't carry extra.

My father had a very interesting emergency one night.

They had just taken off on the last sector of the day (isn't it always?!) and was climbing through 2000 ft when the LITERAL impossible happened: half the overhead warning lights illuminated for no apparent reason.

That wasn't all... the EICAS went nuts and displayed multiple failure messages.

The failures couldn't possibly happen that way (i.e. they weren't real beyond the messages/alerts), and the aircraft continued to fly normally.

That was all the troubleshooting they did - they called mayday and returned to the field, with the shortest downwind they'd ever flown.

The fault? Condensation in the avionics. Cause unknown.

The diversion plan? Return to the departure field on the departure runway if able. That was all. They were ready with the charts, but no time to actually fly the procedure due to the failures they had.

[cavaricooper]

Hi Carl,

BTW - you mentioned Mel Ott. Do you remember in the late 90s and early 2000s he used to have a column on a website writing under the name of Cap'n Tarmack? (Not the ALPA articles, but flight sim articles). I can't remember the website but perhaps you do? I'd love to read some of those articles again but can't look it up on the waybackmachine as I don't remember where he was writing! Could've been microwings or simwings something like that. He used to sim using Project Magenta in those days.

If not then perhaps someone else remembers or still has them filed somewhere and would like to share?

First, thank-you for the details in your post!

No, I do not have them saved, but I too wish I did. Should you find them (I will search as well) please post them here for all to enjoy. Should you, I will send Shirley (his wife) a link. She and their son (Brian?) would be thrilled to read about Mel still being discussed and remembered (fondly) after all these years.

Ta- C

PS- Here are a couple of well thumbed Manuals from Mel's days at NW-









Hoppie limited the display width of the images

[Britjet]

It goes without saying that a diversion should always consider the availability of chicken wings, beer on tap and possibly a lap-dancing bar - but another factor would be the strength of the runways, taxiways and apron at the alternate.

Regarding strengths - we now delve into the mysterious world of PCNs and ACNs. These are Pavement Classification Numbers and Aircraft Classification Numbers.
Every airport of any significance will have PCNs calculated somewhere for their respective areas. These are quite often hard to find, although Jeppesen is better than most, or more usually the actual airport's government directory.
Every aircraft over a certain weight (I think, about exec jet size) will have its own ACN table.

I would stress that this stuff is way beyond the pay-grade of your average airline pilot - as if he or she even had the time to work it out - so as a result a list of "acceptable" alternates is available for a crew. If your chosen airport isn't on the list - you go there at your peril!

A PCN number will look something like this (here is a sample from LOWI - Innsbruck)
Taxiways: PCN 45/F/A/W/T
Runway : PCN 75/F/A/W/T

Now,"F" means "Flexible" - typically Asphalt, and "R" means "Rigid" - typically Concrete.
The "W" and the "T" refer to tyre pressures and how the measurements were made - best not to go there - they tend to be standard..

Now you can find online the ACN for 747 variants - the passenger version is:
F - A-53 B-59 C-73 D-94.   R - A-53 B-62 C-74 D-85

So at Innsbruck's runway, where it's an "F" and an "A", the PCN is 75.
If you are at max weight on your 747, the equivalent number from the ACN is 53. So you are OK on the runway, but not on the taxiway, which is only 45!

If you are still with me - you can see that all this is far too much to work out while barrelling along at 500kts, so the "approved" list is what you use. Phew.
It does throw up the obvious point that 90% of the airports that you at choose to play with in PSX are not strong enough for a 747!.

If you had the misfortune to end up at one of these under-strength airports then all is not lost. You don't have to donate your beautiful 747 to the local museum - you simply reduce its weight to a minimum (even taking seats out if necessary) and then fly it out under the PCN. It's been done many times..

Next week - Fire categories (unless someone beats me to it - feel free!)
Peter