Transition Speeds
Thread Starter
Join Date: Jul 2002
Location: waw
Posts: 2
Likes: 0
Received 0 Likes
on
0 Posts
Transition Speeds
Gentlemen,
I was flying recently and heard the following clearance:
"Flt *** descend 7,000, transition speed 290." This was in Canada. What exactly is a transition speed?
Thanks in advance.
I was flying recently and heard the following clearance:
"Flt *** descend 7,000, transition speed 290." This was in Canada. What exactly is a transition speed?
Thanks in advance.
Join Date: Jan 2003
Location: Southampton
Posts: 99
Likes: 0
Received 0 Likes
on
0 Posts
OK so I'm not a pilot so you'll have to forgive any glaring errors but my general interpretation is that....
In the cruise at high levels the a/c fly in Mach no's whilst at lower levels they refer to IAS. The instruction was for the a/c to fly an IAS of 290kts when they make the transition from Mach no to IAS. This varies but is usually in the mid 200 FL's.
(Takes cover before being shot down in flames for gross stupidity...)
In the cruise at high levels the a/c fly in Mach no's whilst at lower levels they refer to IAS. The instruction was for the a/c to fly an IAS of 290kts when they make the transition from Mach no to IAS. This varies but is usually in the mid 200 FL's.
(Takes cover before being shot down in flames for gross stupidity...)
Join Date: Apr 2007
Location: AAVA Heaven
Age: 42
Posts: 26
Likes: 0
Received 0 Likes
on
0 Posts
Well Cartman,
if you get shot down you won't be the only one. They bang it in at the college of knowledge that the transition from mach to IAS starts about FL290/280-ish on modern airliner types.
Starboard, you don't mention if were flying on a mach first so we're all assuming you were and therefore you got the "transition" specification. It seems to be said in lots of different ways (partly the ATCO trying to keep RT down, partly trying to acknowledge that some speeds are unrealistic at various levels). I believe there was a discussion on here once upon a time about the use of the term transition (potential confusion with transition altitudes, etc.)
WW
if you get shot down you won't be the only one. They bang it in at the college of knowledge that the transition from mach to IAS starts about FL290/280-ish on modern airliner types.
Starboard, you don't mention if were flying on a mach first so we're all assuming you were and therefore you got the "transition" specification. It seems to be said in lots of different ways (partly the ATCO trying to keep RT down, partly trying to acknowledge that some speeds are unrealistic at various levels). I believe there was a discussion on here once upon a time about the use of the term transition (potential confusion with transition altitudes, etc.)
WW
Join Date: Mar 2002
Location: Euroland
Posts: 2,814
Likes: 0
Received 0 Likes
on
0 Posts
It could also be said - when your speed reaches 290 maintain it.
When descending at a constant mach number, IAS increases. if descending at m.78, depending on the day, at some stage the IAS will reach 290. At this point, the pilot will maintain 290.
The "transition" in the descent will depend on what the chosen (or imposed) descent indicated airspeed is. i.e. imaging descending at m.xx which was giving you an indicated of 200kt in the cruise. Initially during the descent the pilot maintains M.xx and therefore the IAS increases.
If ATC have said "on transition maintain 210Kt" the changeover will happen early. If on the otherhand they want 320Kt then the transition will happen much later.
There are two limiting speeds for jet aircraft (and a few turboprops) indicated airspeed and Mach Number.
At the lower levels, the indicated airspeed limit is reached before the limiting mach but at some level that limiting indicated airspeed will equal the limiting mach number. Going higher, the limiting mach number will require you to fly at a lower IAS i.e. it is impossible to exceed the limiting IAS without exceding the limiting mach first.
Thus in the climb, the aircraft is climbed at a chosen IAS until the chosen mach number is reached. Depending on how high the climb IAS the chosen mach number may be reached earlier or later.
In the descent it is the opposite.
Please note that IAS = indicated airspeed. TAS (Actual speed through the air and printed on your strips is different).
regards,
DFC
When descending at a constant mach number, IAS increases. if descending at m.78, depending on the day, at some stage the IAS will reach 290. At this point, the pilot will maintain 290.
The "transition" in the descent will depend on what the chosen (or imposed) descent indicated airspeed is. i.e. imaging descending at m.xx which was giving you an indicated of 200kt in the cruise. Initially during the descent the pilot maintains M.xx and therefore the IAS increases.
If ATC have said "on transition maintain 210Kt" the changeover will happen early. If on the otherhand they want 320Kt then the transition will happen much later.
There are two limiting speeds for jet aircraft (and a few turboprops) indicated airspeed and Mach Number.
At the lower levels, the indicated airspeed limit is reached before the limiting mach but at some level that limiting indicated airspeed will equal the limiting mach number. Going higher, the limiting mach number will require you to fly at a lower IAS i.e. it is impossible to exceed the limiting IAS without exceding the limiting mach first.
Thus in the climb, the aircraft is climbed at a chosen IAS until the chosen mach number is reached. Depending on how high the climb IAS the chosen mach number may be reached earlier or later.
In the descent it is the opposite.
Please note that IAS = indicated airspeed. TAS (Actual speed through the air and printed on your strips is different).
regards,
DFC
