Transition Speed

[A21]

Hi , everyone! I would like to know the meaning of "TRANSITION SPEED",

Thanks for your help.

[wadi_racer]

My understanding of Transition speed is when an aircraft changes over from Mach number to IAS, this is generally passing about FL250.
Not really sure of the ICAO definition, or even if there is one.
Generally used in the ACC enviroment for aircraft descending into a CTA/ TMA.
Hope that helps......

[ab33t]

Pretty much what it says transition from one speed to another , my understanding it is the coupling of altitude and transition fro IAS to M or back again

[DTY/LKS]

Generally you will here this when the aircraft is high-level in the FL300+ bracket & is descending, usually IAS kicks in below FL290. Nowadays you SHOULD be hearing "on conversion" or "on speed conversion." This was brought in to avoid any confusion between transition speed & transition level etc, because in America the TL are a lot higher than UK.

[On the beach]

In the en-route descent phase, where tactical flow control is being used, you will quite often be given e.g. "Descend at mach .80 into 300 knots" or "descend at mach .80 transitioning into 300 knots". I'm guessing that transition speed is the speed you are aiming for when you come off mach no.

[middles]

I think that this was brought in so that aircraft on speed control but still flying on a mach number could be transferred to TC East. This was necessary as the standing agreement was generally 'descending to fl250'(LAM arr.) and separation was not ensured if the following aircraft checked-in using a different speed reference.

[320 or greater]

This phrase is used on almost all AC sectors with elements of sequencing involved, not just those feeding TC East. Sometimes used with mach no to try to stop clever (sometimes harp based) operators from converting to 270 knots at FL350 thus negating the nice line we'd got established!

[anotherthing]

If a pilot has enought time to work out the relationship between Mach and IAS at FL350 then good luck to them... I doubt if many could without a high speed Dalton

[9th Dan Vectors]

Less of good luck than quick look anotherthing.

If they are at FL350 then how long would it take them to glance between ASI and Machmeter?

[anotherthing]

ever heard of coffin corner

[anotherthing]

Wouldn't take that long if it was that simple... apart from airframe speed, level, temp,etc.

Do you know the relaitionship between temp, pressure, density, IAS etc?? because I , having flown professionally for 10 years.

And I guarantee most civvy pilots dont have a c;ue

[9th Dan Vectors]

Hi. Yes thanks. Luckily I have a degree in Aerospace Eng - aircraft performance was something NATS didn't do well at. The whole point of a pilot transitioning between the speeds is so that they can fly under critical Mach number for the airframe or max q speed for the airframe depending on altitude (density etc which you mention). Whilst flying at the desired Mach number an eye can be kept on the ASI to stay above stall speed. The intersection of Critical Mach with stall IAS is the coffin corner you refer to. My point was that in the case of the 270 knot crossover at FL350 no special calcs are required. If the conditions mean the Mach number is safe when the ASI indicates 270 knots, then a 270 knot descent would be safe.