Understanding air space

[rather_fly]

Hi all

 

I'm trying to get my head around air space and how it's depicted on VTC's.

 

If, on the chart, it reads "C FL 8500", then steps down to "C FL 5500", does that mean that I have to fly below or above 8500' to be clear of the air space? This is particularly looking at flying around Albury.

 

Is the class C airspace above or below the levels on the VTC? I'm so confused I've been looking at it for so long!!

 

Thanks so much for your help!

 

 

[rhysmcc]

It should read "C LL 8500" (note the LL rather then FL). That's the highest level you could fly before you enter C airspace, IE you can fly at 8500 in that step. The airspace then drops down to 5500, you would need to be at that level prior to the airspace boundary to remain outside C airspace. (assuming there isn't D airspace under the C step as I don't have a copy of the VTC with me).

 

http://www.recreationalflying.com/tutorials/navigation/airspace.html has a good guide, but I would suggest going over with your instructor.

 

 

[kaz3g]

Be aware that Class E is "controlled" and there are some basic requirements when operating in it.

 

Class E airspace permits greater flexibility for VFR flights. IFR flights are separated from other IFR flights, however VFR flights may operate in Class E airspace without a clearance if the pilot can fulfil the following requirements and recom- mendations:

 

• Operating mode A and C Transponder

 

• Fly hemispherical levels

 

• Operate in VMC

 

• Monitor an appropriate frequency

 

• For safety, activate strobes and landing lights • Keep a vigilant lookout

 

If you want to get to somewhere near Albury such as Bogong Park, you will need to be at or below 2500' and care will be needed to avoid infringing Class D close by in the East where it drops to 2000' .. You will also need to use the location on the river marked on the VTC, not the location incorrectly depicted by Ozrunways next to the highway.

 

Kaz

 

 

[rankamateur]

not the location incorrectly depicted by Ozrunways next to the highway.

Does much of this happen?

 

 

[Nightmare]

"C LL5500" basically means the C Class airspace lowest limit is at 5500AMSL. If there is no other airspace depicted then it is "G" class airspace under it. Be aware there is C and D class CTR airspace, from the surface, labeled SFC, to a certain height in feet AMSL, or a Flight Level (FL).

 

To answer your question simply, you have to fly below it to stay out of the airspace. I live in another part of the country so not familiar with your area of Australia, but it sounds like you have some airspace steps, one starting at 5500ft and one at 8500ft. Stay under these levels to stay clear of the airspace. Look for restricted areas as well, they are outlined in red and dashed on the inside of the zone. The levels are printed in smaller red print somewhere within the zone, not as conspicuous as the A, C, D and E class zones

 

 

[kaz3g]

Does much of this happen?

I have picked up a couple of these previously and Ozrunways have been grateful for the advice.

 

The errors are probably coming from the AOPA Directory database.

 

Kaz

 

 

[Nightmare]

It should read "C LL 8500" (note the LL rather then FL). That's the highest level you could fly before you enter C airspace, IE you can fly at 8500 in that step. The airspace then drops down to 5500, you would need to be at that level prior to the airspace boundary to remain outside C airspace. (assuming there isn't D airspace under the C step as I don't have a copy of the VTC with me).http://www.recreationalflying.com/tutorials/navigation/airspace.html has a good guide, but I would suggest going over with your instructor.

Hey rhysmcc, I'm sure you are not correct when you said that in a C LL 8500 zone you can fly at 8500 and still stay out of the C class airspace. My understanding is that C LL means C class Lowest Limit, ie, the C class starts at 8500, so if you want to stay clear of the C class you would need to be below this level. Please correct me if I'm wrong, besides common sense dictates to stay well clear of it otherwise you will wander into it very easily.

[kaz3g]

"C LL5500" basically means the C Class airspace lowest limit is at 5500AMSL. If there is no other airspace depicted then it is "G" class airspace. Be aware there is C and D class CTR airspace, from the surface, labeled SFC, to a certain height in feet AMSL, or a Flight Level (FL)....Look for restricted areas as well, they are outlined in red and dashed on the inside of the zone. The levels are printed in smaller red print somewhere within the zone, not as conspicuous as the A, C, D and E class zones

Looking at the Albury VTC you will see that there is a Class D control zone around Albury from ground to 4500 and Class C above it. Reverting to the Melbourne and Deniliquin VNCs, you will see two small red circles, one just north of Benalla and one NNW of Yarrawonga. There is also one inside the Albury zone. These are Restricted areas and it's not only likely to get you a stiff reprimand if you transgress them, it could also be very uncomfortable if some one down there lights a match at the wrong time. The same goes for the much larger PRD down near Puckapunyal and Nagambie. Your charts are your friends and Ozrunways makes them easy to interpret.

 

I hope you enjoy your flying to the max and wish you many hours of enjoyment doing so.

 

Kaz

 

 

[kaz3g]

Hey rhysmcc, I'm sure you are not correct when you said that in a C LL 8500 zone you can fly at 8500 and still stay out of the C class airspace. My understanding is that C LL means C class Lowest Limit, ie, the C class starts at 8500, so if you want to stay clear of the C class you would need to be below this level. Please correct me if I'm wrong, besides common sense dictates to stay well clear of it otherwise you will wander into it very easily.

You can fly at the LL without transgressing but you need to know that your altimeter and transponder are accurate (TSO and 2 year check), and fly the altitude accurately or suffer an incursion report if the space above is controlled C or above.

 

In the example given, you can fly VFR up to 10,000 if you have a transponder and radio because the 8500LL is the lower limit for E in that location, not C.

 

Kaz

 

 

[Nightmare]

Is there something around that specifies that C LL 8500 is G or E class? Because I read it as C class lowest Limit is 8500, ie the C starts at 8500. You got me going back to my text books. From how I read it, I would have thought 8499 is the highest for the G or E class. Maybe the people at CASA give a little lee way to those skimming right on the level. I would still be 50-100ft lower, just for that error margin.

 

 

[rhysmcc]

The lower level is actually class G airspace (unless another airspace level is stated), Class C airspace is above that level. So in this example C LL 8500, At 8500ft you are in class G, at 8501 you are in class C. ATC will usually only issue you a clearance at least 500ft above the LL, to keep you clear of aircraft flying at the boundary.

 

If for example your airspace has 2 levels

 

C LL 8500

 

E LL 4500

 

Then at 4500ft you are in class G, between 4501ft and 8500ft you are in E and above 8500ft you are in C.

 

 

[rhysmcc]

Is there something around that specifies that C LL 8500 is G or E class? Because I read it as C class lowest Limit is 8500, ie the C starts at 8500. You got me going back to my text books. From how I read it, I would have thought 8499 is the highest for the G or E class. Maybe the people at CASA give a little lee way to those skimming right on the level. I would still be 50-100ft lower, just for that error margin.

The airspace only begins above the stated lower level, sorry I don't have a reference.

 

 

[Pearo]

rhyscc is correct. I regularly fly at the LL and I am clear of CTA. IF this is not parroted in the Australian legislation you will find it in the Chicago Convention (ICAO). I cant remember the exact definition, but I have read it, and I am pretty sure it is in the ICAO stuff which is adopted by Australia.

 

Worth noting that Class E is uncontrolled if you are flying VFR.

 

 

[Yenn]

Bear in mind that if you fly at the LL on the chart you will have to also be at the correct quadrantal level.

 

 

[Nightmare]

That's why I like this forum, so educational! Mind you I still don't think I'd be flying at the LL with only a margin of 1ft to penetrate controlled airspace, I'd be cruising about 50 to 100ft below it. Mind you, I can see occasions when you would be virtually on the LL, especially when there are mountains, and low airspace.

 

 

[ian00798]

As per what Rhys said, and the reference is attached to this message, para 1.1.7. Nightmare, ATC won't start getting annoyed until we see you more than 200ft above the lowest level, so I wouldn't worry too much about been 50-100 feet below. Aircraft inside the controlled airspace have to remain at least 500ft above the lowest level to receive the protection of controlled airspace.

 

 

 

[Nightmare]

Yeah, I can understand that, it is my understanding that ATC would usually issue altitudes at whole thousands

 

 

[rhysmcc]

No we can issue any altitudes, VFR will often get levels in the 500s (i.e. 2500), it all comes down to what the pilot requests and what ATC can separate.

 

 

[ian00798]

ATC generally try to comply with the table of cruising levels for both IFR and VFR aircraft, it generally needs to be a good reason for us to use non standard levels.

 

 

[dutchroll]

Hey rhysmcc, I'm sure you are not correct when you said that in a C LL 8500 zone you can fly at 8500 and still stay out of the C class airspace. My understanding is that C LL means C class Lowest Limit, ie, the C class starts at 8500, so if you want to stay clear of the C class you would need to be below this level. Please correct me if I'm wrong, besides common sense dictates to stay well clear of it otherwise you will wander into it very easily.

You can fly at 8500 ft and be outside controlled airspace. Controlled airspace starts above what is depicted as the "LL".

This is why, when we fly commercial and want to guarantee clearance from VFR aircraft outside controlled airspace, we only ever descend to 500' above what is depicted as the "LL". So if it says the LL is 8500', we will limit our descent to 9000' until past the next airspace step, to ensure we don't conflict with any VFR aircraft which might be cruising right on the limit.

 

 

[ian00798]

By the book, once you have a clearance, you are actually obliged to remain in controlled airspace, unless you have received the clearance "clear to leave and reenter on climb/descent". Therefore, whether commercial or private, you really should maintain the 500ft clearance above the steps, and if you can't you need to let ATC know so they can give you the appropriate clearance. As a general rule, we know which aircraft on profile will need this and we automatically give the appropriate clearance.

 

 

[dutchroll]

Therefore, whether commercial or private, you really should maintain the 500ft clearance above the steps, and if you can't you need to let ATC know so they can give you the appropriate clearance.

I guess technically you could be descending through 8,700 ft (with an 8,500 LL) and you are still "inside controlled airspace" but then if there's someone cruising VFR at 8,500 ft, you don't have vertical separation.

Typically in my experience ATC do monitor our descent and will not clear us to a lower level until past the step on radar or until they are certain we won't go OCTA, However in practice we have found this to not always be the case, With the wonderful nuances of Maestro occasionally wreaking havoc on our standard descent profiles by issuing "interesting" time requirements at STAR fixes, it's something we have to keep an eye on. Our rate of descent can change quite dramatically with a couple of minutes to make up or lose and this has certainly caught some people out with lower limits of CTA.

 

 

[Geoff13]

You can fly at 8500 ft and be outside controlled airspace. Controlled airspace starts above what is depicted as the "LL".This is why, when we fly commercial and want to guarantee clearance from VFR aircraft outside controlled airspace, we only ever descend to 500' above what is depicted as the "LL". So if it says the LL is 8500', we will limit our descent to 9000' until past the next airspace step, to ensure we don't conflict with any VFR aircraft which might be cruising right on the limit.

That is how I was taught and have always understood it to be. It happens every day between Bribie and Moreton Islands. C LL is 3500'. Everyone that I know climbs to 3500' to make the crossing to have the best possible chance of gliding to safety in the case of an engine failure. In fact almost everyone I know will not cross if they cannot get the 3500'.

 

 

[aplund]

Just a quick observation from a complete novice, these boundaries do seem to have some fuzz about them. If your map says C LL 8500, and you fly 8501' AMSL then your are technically within controlled air space. But given that QNH is quoted to the nearest whole hPa, there is no way you can believe that you have a precision better than about 30' on your altimeter.

 

Listening to LiveATC on YBAF the other day, I did hear an airspace infringement, but from what I could make out on the radio, the aircraft was definitely in class C airspace. The altitude was way too high and the position was too far north of YBAF. But it did raise a question in my mind. Is there a hard cut-off for infringing airspace? (Not that you'd ever want to push that limit). Presumably the 500' rule from the boundary is due to this fuzz. Your altimeter would have to be off by more than 15 hPa to cause a conflict in vertical separation.

 

 

[ian00798]

We will submit an incident report if your mode c readout is in CTA by more than 200 feet, ie if the LL is 8500, and we see a mode c return of 8800, we will report it as a VCA. Generally the VCAs I see aren't just 100 feet or so, they are normally way more obvious by over a thousand feet or more.