UA B789 Mayday Call
 

Sydney Airport triggers 'full emergency response' after United Airlines mayday call

Police activated a "full emergency response" and roads around Sydney Airport were closed after a United Airlines flight from Los Angeles made a mayday call above the Harbour City this morning.

http://www.abc.net.au/news/2018-10-0...-call/10336766

It seems to be an overreaction to a standard fuel emergency. Was it a mistaken full 'm'aidez' call or is there more to the story than we have been told?

Maybe a PAN call was more appropriate with a priority landing.

No, a mayday was entirely appropriate, as mandated by AIP


“EMERGENCY FUEL 12.1 The pilot-in-command shall declare a situation of fuel emergency by broadcasting MAYDAY MAYDAY MAYDAY FUEL, when the calculated usable fuel predicted to be available upon landing at the nearest airport where a safe landing can be made is less than the planned fixed fuel reserve and as a result of this predicted fuel state, the aircraft requires immediate assis-tance”

The other fuel message is the phrase minimum fuel, where no delays can be tolerated but no special assistance is required, and the use of PAN PAN PAN is not an acceptable alternative.

https://www.skybrary.aero/bookshelf/books/2376.pdf

A lot of this phrase use has been recent, and stems from numerous incidents where pilots did not convey to controllers the situation in full, resulting in poor outcomes, such as Avianca 52.

If they had 40 mins fuel and were given 10 mins holding by ATC which I think they had been, then that would’ve taken them to min reserves.
Hence the Mayday. They were correct in their choice to use mayday fuel.

Two options
 

I accept that the two call options were MINIMUM FUEL or MAYDAY MAYDAY MAYDAY FUEL. However, the latter is intended for use when the aircraft requires immediate assistance as a result of the fuel condition. That suggests that the 'no further delay' priority afforded a MINIMUM FUEL aircraft was regarded as insufficient. That's the aspect that I'm curious about. Right now it seems to me that a MINIMUM FUEL call should have been made earlier instead of waiting to the point where the more urgent status was indicated.

If in doubt I agree with going for the safer option and maybe after a long flight across the Pacific into a busy airport at a busy time of day the more serious status was thought necessary to secure the priority required.

The ATSB inquiry will be interesting. Also interesting that there appears to be a significant difference in airport response to a low fuel MAYDAY and the PAN condition we had last year with the REX SAAB that lost a prop. I'd have expected that to have been a MAYDAY call.

This morning, I listened to the LiveATC file for the time when UA839’s situation escalated, and I’m reading between the lines a little, but here’s a couple of thoughts:

* about 10-15 mins before the first (at least as far as LiveATC goes) exchange between UA839 and ATC indicating an issue, a SIGMET was issued for YMML;
* the first I picked up of an issue with UA is that ATC offered them YWLM, which at that point was 135nm at 2 o’clock from the aircraft which, at that point was still at (or had just left) FL410 - UA declined;
* ATC later offered Runway 25 and again UA declined;
* ATC also asked whether UA was able to continue the STAR or needed any kind of track shortening - again, UA declined and continued on the STAR through to final approach; and
* the only accommodation that ended up being made for UA was that QF829 was asked to accept vectoring to give a little more space to UA839 which approached immediately ahead of QF829.

Assuming YMML was nominated as the destination alternate, it could be the SIGMET is what escalated the situation to a mayday call.

There also doesn’t seem to be much behind early claims of something to do with dry ice or strange odours, and the UA spokesperson’s statement about a “mechanical issue” has a distinct ‘standard words’ vibe about it.

Anyway, summing up, my two cents is that mayday was the right call by the crew, the ATSB probably won’t proceed with an investigation, and we will probably never know what all the fuss was about. I do think the SIGMET is, well, significant, though.

Minimum Fuel would have been quite adequate
 

That's why I'm highlighting the "immediate assistance required" element of the conditions that need to exist before calling a MAYDAY.

And they were immediately assisted - they were offered a diversion to YWLM, they were then offered a crosswind runway in the middle of the morning peak, and they were offered track shortening. ATC then kept everything else out of the way so’s not to hold UA up at all. As it turns out, if their reserves were 30 mins, one or two then race tracks would’ve put them below reserves.

To explain further my earlier post, I am suggesting the UA crew went straight to mayday to make ATC aware that, with a SIGMET in play at YMML, their only options (from their failed flightplan) were YSSY or a diversion.

So far so good
 

OK, just so I understand, what would ATC have done differently with a MINIMUM FUEL call on first contact?

The use of the phrase minimum fuel is used to describe a situation when an aircrafts fuel supply has reached a state where having committed to land at a specific aerodrome, the pilot calculates that any change to the existing clearance to that aerodrome may result in landing with less than the designated fixed reserve.

It does not change priority for the aircraft vs other aircraft heading to the same aerodrome.

VASAviation channel on Youtube have a shorted and unedited graphics and ATC recordings.

VASAviation recording 20 mins

VASAviation 5 minute version

Should the crew diverted to Auckland and topped up the tanks ?

A sigmet doesn’t necessarily mean that an aerodrome becomes unavailable as an alternate. Also, I highly doubt that United only have one option for an alternate on the east coast of Australia. There are ‘preferred alternates’, which would include company handling etc., but I imagine they also have suitable alternates which can be nominated for a legal perspective only.

Secondly, even if it did, then they then have the fuel no longer required for that alternate to use for the approach and landing in Sydney.

What was Sydney weather like at the time?

SPECI YSSY 032230Z 20012KT 9999 -RA BKN006 BKN035 16/15 Q1018

Pretty much as per the TAF they had at time of departure.

Thanks Mark.

I still can’t work out why they couldn’t just change their alternate to Canberra or even Brisbane? It’s not like Sydney was below landing minima.

Anyway, I’m sure there was a lot going on in the cockpit at the time and perhaps company restrictions behind availability of alternates.

Mick