EATs and Delay not determined

[Neptune262]

In the UK this is used and also has specific requirements for the pilots should an RTF failure occur, but I cannot find any ICAO reference to this. Can anybody help as to where the UK's requirements come from?

Do all pilots know what to do when they hear "Delay not determined"?

Quote Mats Part 1, Chapter 4, Section 4.8
If ‘Delay not determined’ has been given, pilots should not attempt to land at the destination aerodrome, but instead divert to the alternate destination specified in the current flight plan or another suitable airfield.

However........

ICAO Doc4444 Chapter 15.3.5
commence descent from the navigation aid or fix
specified in 4) at, or as close as possible to, the
expected approach time last received and acknowledged;
or, if no expected approach time has been
received and acknowledged, at, or as close as
possible to, the estimated time of arrival resulting
from the current flight plan;

[mr.777]

The ICAO bit sounds a lot like RT fail procedures as published in the AIP,so is a bit irrelevant in this context...although I stand to be corrected!!

[Gary Lager]

Do all pilots know what to do when they hear "Delay not determined"?

Probably:
Hold until either
a) delay becomes determined, or
b) fuel runs down to minimums & diversion is necessary

:ok:

In the event of RTF failure,
a) how would the pilots know whether the delay was determined or not?
So following standard RT fail procedures and hence receiving a red flare/light on final if landing really not possible, then diversion is probably the most sensible option.
b) if they did know (ie RT fail occurs after information passed) then diversion would be prudent.

The 7 minutes, after squawking 7600, before changing level (3 minutes before resuming flt planned route if on vectors) is so
a) you folks can get everything else (with working radios) out of the way, and
b) we have time to dig out the relevant Flight Information Supplement and look up the what the hell we're supposed to do next (see above)

Is there a particular scenario not covered here that you're concerned about, Neptune, or has something happened recently that we should (ie would like to) know about?

GL

[HEATHROW DIRECTOR]

<< but I cannot find any ICAO reference to this. Can anybody help as to where the UK's requirements come from?>>

Interesting - I was trained to use precisely that phraseology (and did, many times) when working abroad with an ICAO Licence back in the 60s. If there is no reference now, presumably things have changed.

"Delay nor determined" was always used when, for example, there was bad weather and the usual system of calculating EATs could not be used - much as happens nowadays in the UK.

[Spitoon]

It doesn't come from ICAO.

Here's the story. EUROCONTROL developed a single radio communications failure procedure for the European region and talked ICAO into adopting in on 24 January 2002. It was published in Doc 7030 Regional Supplement and so modifies the procedure in Doc 4444.

The revised procedure was pretty much based on the assumption that radio failures only occur in a radar environment and, maybe because EUROCONTROL is a bit light on aerodrome operations (although I've been castigated when making the suggestion in the past so make up you own mind on the reasons), didn't deal well with all of the possible situations that can occur. Now, although 'delay not determined' is not a common instruction, it would be nice to know what should be done if an aircraft goes radio fail in these rare circumstances so the UK added added the paragraph that Neptune quotes. The reality is that in the circumstances that would require an EAT of 'delay not determined' it is safer for an aircraft to divert somewhere else than to try and land on a runway that was, for some reason, not available when the aircraft approached the fix.

It's important not to take this paragraph out of context. If the rest of the comm failure procedure is followed, ATC will watch closely what the aircraft does and will try to clear everything else out of the way. And the procedures describe a couple of alternative comm channels that might be usable.

Hope this helps. Doc 7030 ref is EUR/RAC 5.0.

[Neptune262]

My reason for asking is that it seems that a UK pilot would hopefully comply with the UK rule, but what would international pilots do?

What can we as ATCOs really expect an aircraft to know about what we tell them if the rules are not internationally based! When asking internationally trained pilots they had not heard of the UK rule!

[Spamcan defender]

What can we as ATCOs really expect an aircraft to know about what we tell them if the rules are not internationally based!
We can expect the pilots to do absolutely ANYTHING :eek: . Lets be honest, we've all experienced RT fail a/c whether it be in the Ops room or in the sim and there is really no obvious course of action to be taken from an ATCO perspective other than to monitor what the a/c does and keep everything else out of its way. I feel that the proc's are all fine and dandy and for the en-route phase probably work fine as the pilot (if he elects to continue to destination) will do just that. It becomes a bit more sketchy when the a/c's in the terminal phase when holding or wx are a problem. At that stage it's anyones guess really.


Spamcan

[Neptune262]

Agree with you completely Spamcan. Always expect the unexpected!

I was just trying to highlight the potential differences that pilots are trained by and that some have never seen the UK side of things!

[DFC]

There is a reference in ICAO but I think it is only in the R/T section.

However, from a pilot's point of view this is very simply how the situation works;

1. Aircraft A arrives at the holding fix and requires to hold awaiting weather improvement. ICAO simply says move that aircraft to another hold or to the top of the stack so that other aircraft who can make an approach are not delayed. Thus there should not be a case where aircraft who can make an approach (and be given an EAT if necessary) are above aircraft who can not.

2. If the weather is such that all the aircraft in the stack are holding awaiting an improvement then everyone gets "delay not determined"

If the weather is below minima you can not start an approach (legal requirement). If you have a radio failure before hearing that the weather has improved sufficiently to make an approach there is nothing else to do other than divert.

The same goes if say the runway is blocked........you arrive at the top of the stack and get delay not determined due runway blocked. If you then get an R/T failure why would you waste fuel making an approach to (according to the latest info you have) a U/S runway?

Let me see.......with 3 VHF comms, HF, ACARS, Satcom and a trusty mobile.......if we have a total communication failure we are really in the pooooooooo..............probably for reasons other than communication!

Regards,

DFC

[Spitoon]

Let me see.......with 3 VHF comms, HF, ACARS, Satcom and a trusty mobile.......if we have a total communication failure we are really in the pooooooooo..............probably for reasons other than communication!Had the same argument from a u/t not too long ago and spent some time encouraging him to learn the procedures and to understand the variations that could be expected (much to his chagrin). I could not help feeling smug when within a couple of weeks we had a comm failure! And with a 4-engined jet aircraft (albeit a small one).
In reality though, DFC is quite correct on this one - it's going to be a rare occurrence that an aircraft goes radio fail after having been given an EAT of delay not determined. And yes, as Spamcan points out, we controllers don't expect pilots to do anything after a com failure and the revised procedures recognise this fact because they are largely designed around ATC watching an aircraft on radar after it squawks R/T fail and getting everything else out of the way. But rather than complaining that the UK, yet again, is different from the rest of the world, maybe you should be asking why EUROCONTROL developed a set of procedures that completely ignored an ICAO standard procedure (however unlikely it might be). Perhaps the answer is that, like so many things that EUROCONTROL does, if it doesn't affect EUROCONTROL then it is considered not to matter!

[PPRuNe Radar]

1. Aircraft A arrives at the holding fix and requires to hold awaiting weather improvement. ICAO simply says move that aircraft to another hold or to the top of the stack so that other aircraft who can make an approach are not delayed.

Got a reference for this instruction ? .. thanks :ok:

[DFC]

Radar,

It is in DOC4444

Can't remember if it is in the holding section or the approach sequence bit but it is there.

If you can't find it, let me know and I will look up the exact reference.

Regards,

DFC