As GT3 says, it does not update the EOBT if a slot gets allocated.

We can ignore slots if there are MDIs in force and a/c call in time to make their CTOT. Flow were happy about this, but asked us to update the EOBT to aid their planning. Of course, having updated the EOBTs, new slots got allocated another few hours hence, and then flow told us we had to depart on the slots, as the MDIs were due to end before the latest slots.

maybe an idea for EFPS is that when the a/c signs in and is ready but has a big slot delay, the GMP can activate the squawk in NAS, even though it will not be airborne for some time?

or if CCDS is running out of squawks, then it could delay the issue of one until the a/c is within 15 mins of its slot time, or the controller requests a squawk with a DQ message or some equivalent, whichever is the sooner.

(I want recognition if either of these ideas are taken on!)

Its probably a case of "computer says no", which in my language translates into "we didnt write the software so we dont know if its possible":=

When it's busy at LL 'within 15 minutes of its slot time' it might well be at the holding point queue, and if it's that busy I certainly don't want to be worrying about giving out new squawks over the R/T.

Ok then, why cant we have transponders that have an 8 and 9 on them?

Going off on a tangent now, surely the US would have an issue with a shortage of squawks. How do they get around this problem? (0 points for anyone who says Squawk 7000!)

Why can't transponders have 8 or 9 on them?

Because they can't, its part of the scientific and mathematical formula which is an integral part of the transmission and recieve process of that particular piece of kit.

I've never understood it myself and never will, just accept it as one of those things.:ugh:;)

Each selected number on the transponder is sent in binary form - 3 'bits' which can either be 0 or 1. The first digit represents 4 units, the second 2 and the third 1. ie. 100 represents 4, 001 represents 1, 110 represents 6. This is why you can't have 8 or 9. As to the mechanics of why it can't be done using 4 binary 'bits' representing units of 4,3,2 and 1 which would produce numbers 0-9 I ahve no idea!!:ok:

In the olden days many computers Octals (3 bits) which to a human are the numbers 0-7. Later we used Bytes (8 bits) and nibbles (4 bits) which give the numbers 0-F in hexadecimal (as you see on your computer). The transponder code is you setting 4 Octals of data which is why there are only the numbers 0-7.

Re - Why does Europe have a code shortage and the US not. I believe the US dynamically allocates codes across the whole airspace system using flight plan info to minimize the potential for a duplicate code - which is why very occasionally you do have a code change enroute in the US. As far as I am aware they don't have lots of special conspicuity codes or allocations of codes to individual controlling areas - hence much greater flexibility. They also have ‘everyone’ except VFR on a discrete code as compared to the use of here of say a 'Farnborough Code' used simultaneously by several aircraft receiving a service.