Tenerife accident: phaseology change?

[sabenaboy]

Does anybody know what effect the 1977 Tenerife accident had on ICAO phraseology? Which lines were changed, how was it before?

[Jonty]

Not sure if this is right but: before the crash the phrase "takeoff" could be used at any point ie "Request takeoff clerance" or "after takeoff turn left/right ect...." Now the phrase "Departure" is used instead and "Takeoff" is only used when clearing the aircraft in question for take off, "abc123, cleared of take off runway 18"
Stand to be corrected by any ATCOs out there. (or any one else for that mater!)

[18greens]

I thought one of the other changes was the use of 'Clear'. Clear is only used to clear someone to land or takeoff.

If you are leaving the runway you don't say 'Clear of the runway' you say 'Runway vacated'.

At Tenerife an aircraft was backtracking down the runway while another was lined up waiting for clearance to takeoff. (all in 20m foggy viz) The controller asked the Taxiing aircraft ' are you clear of the runway' and the lined up aircraft heard the word clear and took it as their clearance to take off. Had they used the words 'are you vacated?' perhaps the other 747 would not have moved.

[Farmer 1]

Was this when "affirmative" was given the boot?

Affirm or negative, the word hasn't reached everyone yet.

[TheOddOne]

18 Greens,

Yes, you're quite right.

ICAO took the opportunity to tidy up quite a few RFT phraseology anomalies, not just those that came directly from the Tenerife tragedy.

'Clear' and 'takeoff' as already mentioned above. Also, a number of other words introduced where 'clear' or 'cleared' were used, mainly 'approved' as in 'pushback approved'.

'Affirm' so that it couldn't be confused with 'negative' if the first part of the word goes missing. if you just heard '-ative' prior to this, you'd not have a clue as to whether or not they meant 'yes' or 'no'!

'Go ahead' went to be replaced by 'pass your message', so that the unique safety-critical phrase 'go around' couldn't be confused.

'Say again' instead of 'repeat'. Apparently, in the military, 'repeat' means 'put another round of ordnance where you put the last one'.

There's more. Look in CAP 413.

Unfortunately, there's much more to do, particularly around the holding points and entering the runway. Differences between US and the rest of the World are still causing confusion and runway incursions, the current 'hot topic'.

Cheers,
TheOddOne

[212man]

I was always curious why, having prescribed the words 'affirmative' and 'negative', they then had to shorten the former to avoid confusion when it would have been simpler and less ambiguous to use the words "yes" and "No". Surely no mistaking them???:uhoh:

[nugpot]

One of the biggest changes were that you could only be cleared for 7 actions:

Cleared for take-off
Cleared to land
Cleared for the approach
Cleared for SID
Cleared for STAR
Re-cleared from flightplan route
Re-cleared from flight plan altitude

(the last 2 are because when you ask for clearance before start, you are actually cleared for 3 things: Cleared XXX to YYY FL280 (implies flightplan route and altitude) off RWY xx via the EXAMP 7A departure)

All other ATC directions are "Instructions", not "Clearances".

Clearances have to be read back in full.

[nugpot]

I was always curious why, having prescribed the words 'affirmative' and 'negative', they then had to shorten the former to avoid confusion when it would have been simpler and less ambiguous to use the words "yes" and "No". Surely no mistaking them???:uhoh:


There are various reasons. In the old days, yes and no were too short for voice activated mikes (R/T phraseology used over intercom). They are also pretty useless on poor quality HF.

[sabenaboy]

Thanks for the replies. Very interesting!
I started this thread, because someone else asked the question in an other aviation forum. It didn't get any answers there, because it was not an independent topic.
Someone asked it in a thread about the FAA phraseology "position and hold" instead of "line-up and wait"
I think that's also an interesting topic of discussion, so I'll start the same thread here.
( http://www.pprune.org/forums/showthread.php?p=2432690#post2432690 )
Regards,
Sabenaboy

[chevvron]

Not really au fait with US phraseology, but isn't it 'taxi into position and hold'?

[sabenaboy]

Dear Chevvron,
A quick bit of history:
For as long as I can remember, the correct, by the book phrasology was "taxi into position and hold". Controllers at busy facilities quickly learned that saying the first extra four syllables (sp?) was a waste of time. A local controller at a busy international airport like ORD would say "taxi into position and hold" up to 400 times a day. Thats 1600 syllables a day. So, the unofficial change happened about 10 years ago, and everyone would just say "position and hold". Pilots knew what it meant, it sounded better on the radio, and it saved time in a busy terminal environment. So, back in, oh, 2002 or so (don't quote me on the date, but recently), the FAA changed the 7110.65 to make the standard phrasology "position and hold".
Regards,
Sabenaboy