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Boeing757100
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Why do different cities in India have different transition altitudes?

Mon Nov 21, 2022 5:35 pm

I'm only a casual flight simmer, but I wanted to make the experience a little more realistic, and since I was flying out of India, I looked up if there was a specific transition altitude that applies to the whole country, but instead, I found this.
https://aim-india.aai.aero/eaip/PUB/201 ... cified,2.1.

Apparently, there are transition altitudes assigned to different aerodromes. I didn't really understand why this is. Generally, a transition altitude applies to a wider area, like in the whole US, it's generally FL180. How come it's different in India, and are there any other places in the world that do it like this? I know the EU has transition altitudes as low as 3000ft but I'm unsure if they vary by airport.

Thanks all
 
r6russian
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Re: Why do different cities in India have different transition altitudes?

Mon Nov 21, 2022 6:09 pm

transition altitude/transition level (one is used in climb, other in descend, dont remember which one is which) are for guaranteed terrain clearance. In the US its FL180 because that gets safely over the rockies at 29.92 altimeter, and it was easy to make the whole country FL180.

In europe its lower because the mountains are lower/nonexistent. Netherlands is flat, hence 3000ft

Its easier for the controllers knowing vast majority if their traffic is on the same altimeter and only needing the local altimeter on approach and climbout

But why its different all over india, not sure. They got mountains there, maybe they decided to transition as low as possible while having terrain clearance
 
e38
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Re: Why do different cities in India have different transition altitudes?

Mon Nov 21, 2022 10:01 pm

r6russian wrote:
transition altitude/transition level (one is used in climb, other in descend, dont remember which one is which)


transition altitude is normally used in the climb--altitude where pilot is required to change from local QNH to standard 1013 / 29.92; transition level used during descent-change from standard back to local QNH.

e38
 
r6russian
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Re: Why do different cities in India have different transition altitudes?

Mon Nov 21, 2022 11:19 pm

e38 wrote:
r6russian wrote:
transition altitude/transition level (one is used in climb, other in descend, dont remember which one is which)


transition altitude is normally used in the climb--altitude where pilot is required to change from local QNH to standard 1013 / 29.92; transition level used during descent-change from standard back to local QNH.

e38

Thanks for clarifying that.

Off the top of my head i thought opposite. Figured once youre cleared to climb to a FL, you would climb thru the transition level and set the altimeter to STD, and on the way down, once cleared down to an altitude, youd go thru the transition altitude and set the altimeter to local QNH.

Will have to remember that altitude/level means where you came from, not where youre going, if that makes sense
 
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77west
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Re: Why do different cities in India have different transition altitudes?

Mon Nov 21, 2022 11:21 pm

r6russian wrote:
transition altitude/transition level (one is used in climb, other in descend, dont remember which one is which) are for guaranteed terrain clearance. In the US its FL180 because that gets safely over the rockies at 29.92 altimeter, and it was easy to make the whole country FL180.

In europe its lower because the mountains are lower/nonexistent. Netherlands is flat, hence 3000ft

Its easier for the controllers knowing vast majority if their traffic is on the same altimeter and only needing the local altimeter on approach and climbout

But why its different all over india, not sure. They got mountains there, maybe they decided to transition as low as possible while having terrain clearance


Ummm.. the Alps would like to have a word...
 
ArcticFlyer
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Re: Why do different cities in India have different transition altitudes?

Mon Nov 21, 2022 11:33 pm

While most countries have the same transition altitude throughout their territory (or at least within each FIR if a country has more than one) there is technically no requirement for this. If you use Jeppesen charts (not a paid promotion) each SID/STAR and approach chart will have the applicable transistion altitude/level for that procedure published.

As a side note, there is also no requirement that the transition altitude (climbing through which you set STD/29.92) be the same as the transition level (descending through which you set the local altimeter setting as assigned by ATC or reported by your destination airport). Mexico is a good example of this; at most (if not all) airports in Mexico the transition altitude is 18,500' while the transition level is FL195. This means that 19,000' (reference local altimeter) is a valid altitude assignment for arriving/descending aircraft but not for departing/climbing aircraft.
 
r6russian
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Re: Why do different cities in India have different transition altitudes?

Mon Nov 21, 2022 11:43 pm

77west wrote:
r6russian wrote:
In europe its lower because the mountains are lower/nonexistent. Netherlands is flat, hence 3000ft


Ummm.. the Alps would like to have a word...

Figured someone would chime in, might as well admit not knowing and ask a followup question of my own

I found a random STAR into GVA, looked like a real close airport to Mont Blanc. It shows transition altitude of 7000 feet, but transition level by ATC. And on the one arrival that comes from the south, it shows altitude restrictions in feet, not flight levels. So what would ATC use for a transition level in this case?
 
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Starlionblue
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Re: Why do different cities in India have different transition altitudes?

Tue Nov 22, 2022 12:20 am

AFAIK, the reason ATC sets a transition level is due to QNH variations. The TL at any given time would be on the ATIS.

Many places have a "normal" published TL, but also different TLs for very high and very low QNH. HKG is an example with a normal TL of FL110, but if the QNH is 797 or below the TL is FL120. This can also apply to the TA. At PVG the normal TA is 9850ft, if QNH is 1031 or more 10830ft and if QNH is 979 or less 8860ft.
 
GalaxyFlyer
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Re: Why do different cities in India have different transition altitudes?

Tue Nov 22, 2022 1:17 am

Regarding terrain and transition. SCEL has a transition altitude of 10,000’ and a TLv by ATC. Lots of high terrain around Santiago and the MSA is 19,000’.
 
gloom
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Re: Why do different cities in India have different transition altitudes?

Tue Nov 22, 2022 6:21 am

Starlionblue wrote:
AFAIK, the reason ATC sets a transition level is due to QNH variations. The TL at any given time would be on the ATIS.


This is usually where an ATC makes sure TL is higher than TA. For my country TA is 6500, TL is F80, but once the pressure is high enough to offset 1500ft (yeah, I know that's a lot, IIRC more or less 35hPa from ISA), then TL will be anounced as F90. Many countries would have a rule to keep it above 1000ft as well, to keep vertical separation between TL and TA. However, I think it's more the way ATC is taught and to maintain consistency of understanding what TA-TL layer is. After all, there are some countries where it's usual to use altitude/level in that layer for approaching traffic (if you have departures at 6000ft limit, and plenty of space in layer, why not use 7000 with local QNH, giving you extra level for arrivals?).

Plenty to consider there for local ATCs.

Cheers,
Adam
 
ArcticFlyer
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Re: Why do different cities in India have different transition altitudes?

Tue Nov 22, 2022 9:05 am

Starlionblue wrote:
AFAIK, the reason ATC sets a transition level is due to QNH variations. The TL at any given time would be on the ATIS.

Many places have a "normal" published TL, but also different TLs for very high and very low QNH. HKG is an example with a normal TL of FL110, but if the QNH is 797 or below the TL is FL120. This can also apply to the TA. At PVG the normal TA is 9850ft, if QNH is 1031 or more 10830ft and if QNH is 979 or less 8860ft.

This is technically the case in the U.S. as well although it is never explicitly referred to as such and pilots are often unaware of this. There is a section in the FAR/AIM called "Lowest Usable Flight Level" which basically calls for a higher transition level (transition altitude is always 18,000' in the U.S.) when the altimeter setting is below standard. In Alaska where we have a lot of turboprops flying and often lower-than-standard pressure it is somewhat common to hear a pilot ask "Is FL180 available today?" [as a cruising altitude]. If the pressure is below standard the answer is no and FL190 is the lowest (IFR) cruising altitude.
 
CosmicCruiser
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Re: Why do different cities in India have different transition altitudes?

Wed Nov 23, 2022 12:24 am

I was always told from my flight Safety classes many many years a go the the US. uses 18,000' because it's half the atmosphere=500mb. When I went to the airlines I don't remember them saying much except the separate levels in Europe and other places. The oddest was Almaty, KZ where you descended on QNE and transitioned to QFE! And you had just passed 20,000' mountains. If you were IFR it was real sight to see the altimeter jump at the transition!
 
GalaxyFlyer
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Re: Why do different cities in India have different transition altitudes?

Wed Nov 23, 2022 1:05 am

CosmicCruiser wrote:
I was always told from my flight Safety classes many many years a go the the US. uses 18,000' because it's half the atmosphere=500mb. When I went to the airlines I don't remember them saying much except the separate levels in Europe and other places. The oddest was Almaty, KZ where you descended on QNE and transitioned to QFE! And you had just passed 20,000' mountains. If you were IFR it was real sight to see the altimeter jump at the transition!


Remember, it was F240 (PCA days) for a long time at the Rockies and west.
 
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Starlionblue
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Re: Why do different cities in India have different transition altitudes?

Wed Nov 23, 2022 3:31 am

CosmicCruiser wrote:
I was always told from my flight Safety classes many many years a go the the US. uses 18,000' because it's half the atmosphere=500mb. When I went to the airlines I don't remember them saying much except the separate levels in Europe and other places. The oddest was Almaty, KZ where you descended on QNE and transitioned to QFE! And you had just passed 20,000' mountains. If you were IFR it was real sight to see the altimeter jump at the transition!


QFE. Gross... :lol:

The one thing I really wish the entire world would agree on is altimetry. QNH vs mmHg is no big deal, but metric drives me up the wall. Get the clearance in metric. Read back. Convert to feet. Crosscheck with the other guy. Set in feet. Adds a bit to the pucker factor when you're doing an approach in mountainous terrain.

I'm a hardcore metric fanboi on almost anything, but I can't deny that altitudes and flight levels in feet are much easier to grasp instinctively than metres, because most of the increments are thousands instead of 300s(ish).
 
CosmicCruiser
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Re: Why do different cities in India have different transition altitudes?

Wed Nov 23, 2022 2:12 pm

I was told my a PP buddy in UK that they do QFE if they stay local
 
GalaxyFlyer
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Re: Why do different cities in India have different transition altitudes?

Wed Nov 23, 2022 2:22 pm

Starlionblue wrote:
CosmicCruiser wrote:
I was always told from my flight Safety classes many many years a go the the US. uses 18,000' because it's half the atmosphere=500mb. When I went to the airlines I don't remember them saying much except the separate levels in Europe and other places. The oddest was Almaty, KZ where you descended on QNE and transitioned to QFE! And you had just passed 20,000' mountains. If you were IFR it was real sight to see the altimeter jump at the transition!


QFE. Gross... :lol:

The one thing I really wish the entire world would agree on is altimetry. QNH vs mmHg is no big deal, but metric drives me up the wall. Get the clearance in metric. Read back. Convert to feet. Crosscheck with the other guy. Set in feet. Adds a bit to the pucker factor when you're doing an approach in mountainous terrain.

I'm a hardcore metric fanboi on almost anything, but I can't deny that altitudes and flight levels in feet are much easier to grasp instinctively than metres, because most of the increments are thousands instead of 300s(ish).


Or select Metric on PFDs, read and set metric. Except in China, where it’s a mess. QFE is nearly gone now. We used it at EAL, as did AA until 1995.
 
CosmicCruiser
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Re: Why do different cities in India have different transition altitudes?

Wed Nov 23, 2022 6:08 pm

GalaxyFlyer wrote:
Starlionblue wrote:
CosmicCruiser wrote:
I was always told from my flight Safety classes many many years a go the the US. uses 18,000' because it's half the atmosphere=500mb. When I went to the airlines I don't remember them saying much except the separate levels in Europe and other places. The oddest was Almaty, KZ where you descended on QNE and transitioned to QFE! And you had just passed 20,000' mountains. If you were IFR it was real sight to see the altimeter jump at the transition!


QFE. Gross... :lol:

The one thing I really wish the entire world would agree on is altimetry. QNH vs mmHg is no big deal, but metric drives me up the wall. Get the clearance in metric. Read back. Convert to feet. Crosscheck with the other guy. Set in feet. Adds a bit to the pucker factor when you're doing an approach in mountainous terrain.

I'm a hardcore metric fanboi on almost anything, but I can't deny that altitudes and flight levels in feet are much easier to grasp instinctively than metres, because most of the increments are thousands instead of 300s(ish).


Or select Metric on PFDs, read and set metric. Except in China, where it’s a mess. QFE is nearly gone now. We used it at EAL, as did AA until 1995.

We had a plastic card showing the metric alt and comparable feet as a cross check. I head years ago that AA would set one alt. to QFE and the other on QNH for I
LS apps. Is that true?
 
GalaxyFlyer
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Re: Why do different cities in India have different transition altitudes?

Wed Nov 23, 2022 7:57 pm

CosmicCruiser wrote:
GalaxyFlyer wrote:
Starlionblue wrote:

QFE. Gross... :lol:

The one thing I really wish the entire world would agree on is altimetry. QNH vs mmHg is no big deal, but metric drives me up the wall. Get the clearance in metric. Read back. Convert to feet. Crosscheck with the other guy. Set in feet. Adds a bit to the pucker factor when you're doing an approach in mountainous terrain.

I'm a hardcore metric fanboi on almost anything, but I can't deny that altitudes and flight levels in feet are much easier to grasp instinctively than metres, because most of the increments are thousands instead of 300s(ish).


Or select Metric on PFDs, read and set metric. Except in China, where it’s a mess. QFE is nearly gone now. We used it at EAL, as did AA until 1995.

We had a plastic card showing the metric alt and comparable feet as a cross check. I head years ago that AA would set one alt. to QFE and the other on QNH for I
LS apps. Is that true?


Can’t say how AA did it, but at EAL we had a third altimeter which was set to local QNH and the two pilots’ altimeters were set to QFE on the approach checklist and cross checked with the company. After the altimeters were set to QFE, the engineer or FO read back station pressure off an altimeter. Memory fades on that one. Goes back to Rickenbacher’s ATL crash in 1943. AA came to near grief at KBDL where a rapidly falling barometer wasn’t caught by the crew or station giving out the QFE. The one way any altimetry reading can be a hazard.

On the Global, we set the QFE given by ATC. I’d set the local QNH by ATC in the Standby display and confirm the difference was equal to field or touchdown zone elevation. That way, we flew ATC heights as was their custom and didn’t have to refer to tables.

The Collins equipped bizjets all had a metric selection for the PFD displays, instant metric displays. Used it Russia and several former USSR airports.
 
chimborazo
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Re: Why do different cities in India have different transition altitudes?

Wed Nov 23, 2022 9:35 pm

CosmicCruiser wrote:
I was told my a PP buddy in UK that they do QFE if they stay local


Yup, certainly in GA we do. Many airfields will give you QNH and QFE on initial contact when approaching or on the ground on first call. I set one on each altimeter.

Never noticeably heard QFE given at a larger aerodrome with airline traffic though.

When requesting a MATZ penetration they often give you the aerodrome height - so QFE too, I assume to ensure you are at the required distance above their airfield.
 
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Starlionblue
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Re: Why do different cities in India have different transition altitudes?

Thu Nov 24, 2022 2:28 am

GalaxyFlyer wrote:
Starlionblue wrote:
CosmicCruiser wrote:
I was always told from my flight Safety classes many many years a go the the US. uses 18,000' because it's half the atmosphere=500mb. When I went to the airlines I don't remember them saying much except the separate levels in Europe and other places. The oddest was Almaty, KZ where you descended on QNE and transitioned to QFE! And you had just passed 20,000' mountains. If you were IFR it was real sight to see the altimeter jump at the transition!


QFE. Gross... :lol:

The one thing I really wish the entire world would agree on is altimetry. QNH vs mmHg is no big deal, but metric drives me up the wall. Get the clearance in metric. Read back. Convert to feet. Crosscheck with the other guy. Set in feet. Adds a bit to the pucker factor when you're doing an approach in mountainous terrain.

I'm a hardcore metric fanboi on almost anything, but I can't deny that altitudes and flight levels in feet are much easier to grasp instinctively than metres, because most of the increments are thousands instead of 300s(ish).


Or select Metric on PFDs, read and set metric. Except in China, where it’s a mess. QFE is nearly gone now. We used it at EAL, as did AA until 1995.


Of course, we set metric on the PFD and read it. But we are also required to cross-check the laminated metric conversion chart. Because of reasons. ;)

To be fair, the PFD metric altitude is seldom exactly the same as the clearance. Since it is derived from an altitude in hundreds on feet, you'll get numbers like "8820 metres".
 
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AirKevin
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Re: Why do different cities in India have different transition altitudes?

Thu Nov 24, 2022 4:19 am

GalaxyFlyer wrote:
Starlionblue wrote:
CosmicCruiser wrote:
I was always told from my flight Safety classes many many years a go the the US. uses 18,000' because it's half the atmosphere=500mb. When I went to the airlines I don't remember them saying much except the separate levels in Europe and other places. The oddest was Almaty, KZ where you descended on QNE and transitioned to QFE! And you had just passed 20,000' mountains. If you were IFR it was real sight to see the altimeter jump at the transition!


QFE. Gross... :lol:

The one thing I really wish the entire world would agree on is altimetry. QNH vs mmHg is no big deal, but metric drives me up the wall. Get the clearance in metric. Read back. Convert to feet. Crosscheck with the other guy. Set in feet. Adds a bit to the pucker factor when you're doing an approach in mountainous terrain.

I'm a hardcore metric fanboi on almost anything, but I can't deny that altitudes and flight levels in feet are much easier to grasp instinctively than metres, because most of the increments are thousands instead of 300s(ish).


Or select Metric on PFDs, read and set metric. Except in China, where it’s a mess. QFE is nearly gone now. We used it at EAL, as did AA until 1995.

You can read the altitude in metric on the PFD, but how would you set the altitude in metric on the MCP.
 
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Starlionblue
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Re: Why do different cities in India have different transition altitudes?

Thu Nov 24, 2022 5:39 am

AirKevin wrote:
GalaxyFlyer wrote:
Starlionblue wrote:

QFE. Gross... :lol:

The one thing I really wish the entire world would agree on is altimetry. QNH vs mmHg is no big deal, but metric drives me up the wall. Get the clearance in metric. Read back. Convert to feet. Crosscheck with the other guy. Set in feet. Adds a bit to the pucker factor when you're doing an approach in mountainous terrain.

I'm a hardcore metric fanboi on almost anything, but I can't deny that altitudes and flight levels in feet are much easier to grasp instinctively than metres, because most of the increments are thousands instead of 300s(ish).


Or select Metric on PFDs, read and set metric. Except in China, where it’s a mess. QFE is nearly gone now. We used it at EAL, as did AA until 1995.

You can read the altitude in metric on the PFD, but how would you set the altitude in metric on the MCP.


True, but you shouldn't really set it using the MCP number anyway. As a rule, try to set any parameter by looking at the PFD number. As the saying goes, the MCP is "rumour", the PFD is fact.

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