Speed Instructions - Phraseology

[rickypbrown]

I was reading the Spring 2007 CHIRP report and noticed quite a few letters regarding speed control. My friend (who flies for Thomson) and I were discussing the correct phraseology that should be used regarding the transition from Mach number to an IAS. He argued that the choice of many ATCOs was "ABC 123 maintain Mach .77, on transition 300kts", but mentioned he found this at conflict with similar phraseology used for transition altitude.

Just wondered what the consensus is on PPRuNe,

Thanks, Ricky.

[MancBoy]

I have noticed a lot of the current crop from the college are using this for real aswell.. I just say "when on indicated, speed 300kts etc".

[BEXIL160]

On transition seems to be becoming the norm, but I'm not too sure.

We already have a Transition Altitude, and the confusion has already occured.

Perhaps fly MACH .79 on conversion 290 kts?

Whatever, we do need some STANDARD phraseology here.

rgds BEX

[camisa10]

According to ICAO doc.4444 :
4.6.1.5 At levels at or above 7 600 m (FL 250), speed
adjustments should be expressed in multiples of 0.01 Mach; at
levels below 7 600 m (FL 250), speed adjustments should be
expressed in multiples of 20 km/h (10 knots) based on
indicated airspeed (IAS).
So ,if we apply this and use standard ICAO phraseology...it might be something like :
"ABC 123 maintain Mach .77, after passing FL 250 maintain 300 kts"
:confused:

[BEXIL160]

Aha, so the ICAO standard "switch over" from MACH to IAS is FL250.

The trouble is different types and even the same type with different airlines use different levels for the "switch" to IAS.

Having to spell out the level is a bit WORDY also, too many figures, and hence another possiblity of error. I'd rather keep it very simple.

Rgds BEX

[rickypbrown]

Why isn't this phraseology included in CAP 413? Surely, a call as important as this should be accounted for?! 'When on indicated' sounds fool-proof, but surely it should be generic and used by all stations within the UK, as most other calls are?

[5milesbaby]

I tend to use "when able speed ###kts" as have been caught out by some elaborate interpretations of "when on indicated", "on conversion", "on transition" by them deciding that FL210 was a good level to convert and then come back to 250kts.

I do agree it needs to be standardised and published.

[MancBoy]

"been caught out"

5, that's just because you are crap like your football team!

[5milesbaby]

Love you too loser xx

[WildWesterner]

Interesting discussion...

I use "transition to" and have never considered the confusion possibilities with transition altitudes, etc. But then I am an AC controller (is this another example of the ever more discipline specific training we get these days - the poor new trainees don't even get a few weeks experiencing tower problems first hand etc.).

Ultimately, ambiguity is bad IMO, and I'm sure everyone elses. I for one will attempt to say something different now. But what?:confused:

I also thought the transition/conversion was more likely to happen around FL290.


WW

[5milesbaby]

I'm area too, and its not often its abused but the odd far fetched interpretation of what I've said has happenned - you wouldn't be suprised by the two carriers I've had the biggest problem with and am not going to be responsible for a Lo-Co sl@g fest.

[FlightDetent]

I use "transition to" and have never considered the confusion possibilities with transition altitudes, etc.
Agreed. I am guilty of not reading the CHIRPs (=UK thing) yet, but the possibility of confusion with transition level at FL200+ is beyond me.

Whichever ATCO understands the MACH/IAS conversion logic, and uses the knowledge to smooth his/hers workings, gets my vote for the next PM.

FD
(the un-real stickshaker)

[BEXIL160]

Well, lets see.... there are LOTS of different transition altitudes in the UK alone.

What seems like a million years ago I, and many others on certain GAPAN committee, were involved in trying to replace them all with ONE TA, 6000ft. Can't remember why it all stalled now, but it never happened. (Perhaps someone could remind me?)

In the US of course the TA is 18,000ft, so confusion could easily arise using the words "On transition". Don't forget, many commercial pilots over here in EUR have trained or flown extensively over there, in the USA.

So, we have a situation where there appears to be no standard phraseology. Not an ideal situation. I wonder what SRG have in mind?

BEX