Airline ATC term

Let'sgoflying!

Let'sgoflying!

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Dave Taylor
Here is a phrase I have heard for years but never looked up because it did not apply to me nor have I ever been instructed to do it.
"UA232, 280kts in the transition"
Explanation requested.
 
I need a little more context but maybe it is the transition from cruise speed to 250 knots at 10,000 feet?
 
Whenever I’ve heard it used with our crews is current Mach until 280kts. Not sure if it’s in the pilot-controller glossary, but it seems to be an acceptable phrase.
 
At higher altitudes we use Mach number for speed. "Transition" is just the change from airspeed to Mach in the climb and Mach to airspeed in the descent. This normally occurs somewhere around FL310, +/- a couple thousand feet, depending on the Mach/airspeed specified.

We might climb at 280kts and transition to M0.78 or descend at M0.80 and transition to 300kts, etc. You most commonly hear that phraseology when on an arrival to a busy airport. The speed assignments are used to provide spacing between arrivals.
 
Right.... most airplanes cannot indicate 320kts at flight level 390, and also cannot hold .80 Mach at 15,000 feet.
So, there is a point at which these two meet.. a point where the Mach matches the speed. That’s where you transition to the other.
Sometimes we climb at 310 until .79 Mach. The reverse in descent.
That is transition.
 
Kritchlow said:
Right.... most airplanes cannot indicate 320kts at flight level 390
Click to expand...
320 KIAS at FL390 would be right about M1.00 and 590 KTAS at standard temperature.

BTW, I'm doing these examples using a Jepps CR-3 mechanical flight computer. The CR computers does this stuff easily, unlike most E6B computers. The CR-3 was the one I had to demonstrate to students. I used the smaller CR-5 for my own calculations (back before I was old enough to have developed an appreciation for larger print!) Now all the modern avionics does this for us providing SAT, TAT, KIAS, KTAS, and Mach displays.
 
Larry in TN said:
320 KIAS at FL390 would be right about M1.00 and 590 KTAS at standard temperature.

BTW, I'm doing these examples using a Jepps CR-3 mechanical flight computer. The CR computers does this stuff easily, unlike most E6B computers. The CR-3 was the one I had to demonstrate to students. I used the smaller CR-5 for my own calculations (back before I was old enough to have developed an appreciation for larger print!) Now all the modern avionics does this for us providing SAT, TAT, KIAS, KTAS, and Mach displays.
Click to expand...
Right... Point was to use extreme examples... you need a bit extreme for those of us C750 pilots. :D
 
Kritchlow said:
Right.... most airplanes cannot indicate 320kts at flight level 390, and also cannot hold .80 Mach at 15,000 feet.
So, there is a point at which these two meet.. a point where the Mach matches the speed. That’s where you transition to the other.
Sometimes we climb at 310 until .79 Mach. The reverse in descent.
That is transition.
Click to expand...

Well let me just waddle on in here and bare my ignorance in hopes that I'm not alone. Why? Is it an indication issue or a physics issue?

Edit: While I was typing the question I think you just answered it. It would be an either/or indication and you can't have both.
 
Timbeck2 said:
Well let me just waddle on in here and bare my ignorance in hopes that I'm not alone. Why? Is it an indication issue or a physics issue?
Click to expand...
Larry described it very well above.
.80 Mach close to sea level is too fast for the airframe, even if thevengines could do it.

The reverse holds true at altitude. Holding 310 at altitude is too fast.
 
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