Joining circuit on base/final legs - Good or bad?

[davebowyer]

G'day all

I'm a 60-hour student pilot (just one more cross-country dual to do, plus the PPL theory, then I'm ready for the PPL exam). On my first solo cross-country navigation exercise, I had an an interesting incident in the circuit at Wollongong Airport (YWOL) that got me thinking about the evident diversity of opinion on the safety/advisability of joining circuits on base or final legs.

I've described the incident fully in my blog post on it here (http://midlifepilot.wordpress.com/2011/05/03/close-encounters-in-the-circuit-was-the-other-guy-in-the-wrong-and-what-can-i-learn/), but what it boiled down to is this. I was on the downwind leg of my approach to land at YWOL, having joined the circuit mid-crosswind. While I was on late downwind, a Diamond made a "joining base" call on the YWOL CTAF and then cut right across my path, to all intents and purposes - as I truly believe - unaware that I was in the circuit. I didn't have to take evasive action, but it was pretty close - any closer to me and it would have been a real danger situation.

I checked out AIP on the subject and note that CASA does not expressly forbid the practice of joining circuits on the base leg, but does not "recommend" it. Similarly, I'm aware from my reading that straight-in approaches (joining final) are similarly regarded by CASA.

Obviously in some situations there might be good operational reasons why you'd need to join circuit on the base or final legs. But as a general practice, is it safe or advisable to do either?

My present thinking is "no", but I'd love to hear from some experienced voices on this topic.

[Trent 972]

Dave, AIP ENR, General Rules and Procedures,


41.
CIRCUIT INFORMATION, SEPARATION MINIMA AND HEIGHT

41.1


Circuit Information

41.1.1 Pilots should fly a circuit commensurate with the aircraft type they are operating. However the use of any circuit procedure does not alter the responsibility of each pilot to see and avoid other aircraft.

Pilots operating in the circuit should manoeuvre to follow traffic ahead of them in the circuit.





48.7 Joining on Base
48.7.1 Joining on base leg, whilst not prohibited, is not a recommended standard procedure. CASA recommends pilots join the circuit on either the crosswind or downwind leg. However, pilots who choose to join on base leg should only do so if they:
a. have determined the wind direction and speed;
b. have determined the runway in use;
c. give way to other circuit traffic and ensure the aircraft can safely (no traffic conflict likely) join the base leg applicable to the circuit direction in use at the standard height; and
d. broadcast their intentions.


It would seem that 'oldmate' that cut you off was either inconsiderate, unaware or just deaf blind and stupid.
As a general practice, is joining on Base leg safe of advisable? Yes, as long as the rules are heeded and commonsense prevails.
Good Luck with the training.

[VH-XXX]

Joining on base can be frustrating for the guy on downwind because in normal "rules of the air" you give way to the aircraft on the right, hence if you are on downwind you may not have anywhere to go to avoid the other aircraft depending on how soon you saw him. If you turned left, you're effectively cutting him off and may be shortening your circuit and if you turn right, you may have to turn quite sharp to avoid him.

The regs are the regs though and the base joiner is supposed to give way, but indeed it doesn't always work out for the best as you have found out!

Straight in approaches can be a little simpler to manage as whilst the other circuit traffic has right of way, the downwind traffic can easily extend if he is kind.

[Xcel]

A few years ago base was fine to join...

Then Casa said 3 legs must be flown...

Now we are back to base joining...

IMHO joining anywhere in the cct can be dangerous given the wrong circumstances and lack of understanding, communication and airmanship.

As long as your situationally aware of the aircraft around you and communicate you can join via an inverted, oblique, sideways, loop the loop special leg.

Unfortunately with a ctaf or ala some "pilots" couldn't organise a piss up in a brewery and flounder away with no communication, airmanship or regard for anyone or anything.

Keep your eyes peeled and thinking the way your thinking (safety aspects and how to fly safer) and you will do great!!

[Andy_RR]

You could always put the wind up them by re-announcing your position late downwind and traffic joining base not yet in sight...

[havick]

That's assuming they're listening to their radio or got the right freq dialed in.

[Captain Nomad]

48.7 Joining on Base
48.7.1 Joining on base leg, whilst not prohibited, is not a recommended standard procedure. CASA recommends pilots join the circuit on either the crosswind or downwind leg. However, pilots who choose to join on base leg should only do so if they:
a. have determined the wind direction and speed;
b. have determined the runway in use;
c. give way to other circuit traffic and ensure the aircraft can safely (no traffic conflict likely) join the base leg applicable to the circuit direction in use at the standard height; and
d. broadcast their intentions.

I'd also like to highlight point (d) here - 'BROADCAST THEIR INTENTIONS.' Intentions are what you are GOING to do. ie. It is expected that a broadcast of intentions to join base be made when making the first inbound call (as with intentions for straight-in approach). This call should be made at 10nm or earlier (Jepp. ATC pg 716). Jepps are another publication of the AIP. If the call of actually joining on base was the first time 'old mate' piped up he has broken both (c) and (d) and I hate to be cynical but probably doesn't give a stuff about (a) and (b) also. As with driving on the roads, sometimes it is up to the law abiding citizen to make safety decisions and corrections to allow for the stupidity of others...

[Captain Nomad]

Obviously in some situations there might be good operational reasons why you'd need to join circuit on the base or final legs. But as a general practice, is it safe or advisable to do either?


Further to your original post, a lot of higher performance aircraft, especially turboprops and airline flights for example, do favour straight in approaches. They generally offer more efficiency and less low level manoevering with the opportunity to establish a nice 'stabilised' approach from some distance out. They can be conducted very safely and usually such aircraft are monitoring and making calls on the CTAF from 30nm or more out. When communicating about INTENTIONS it keeps everyone informed and the procedure can be carried out safely so long as all parties are involved. By all means, don't be afraid to speak up and talk to these guys on the radio if you think you will be in the circuit around the same time as them! Even though they might make a call at 30nm they can be in the circuit in well under 10 minutes and that has caught many people by surprise.

An important reminder here for both light GA pilots and heavy metal pilots. Refer Jepps ATC pg 715 (section 6.2.1.8) and CAAP 166-2(0) section 11.2

So as not to impede commercial aviation, pilots flying
recreational or sport aircraft for their own enjoyment, or pilots
flying GA aircraft for their own leisure, should consider giving way
to aircraft being used for ‘commerce’ provided that the
inconvenience to their own operation is not great and it can be done
safely. Operators of commercial flights should never expect a give
way offer to be assumed or automatic. Any offer to give way must
be explicit and its acceptance acknowledged.

For someone such as yourself, a circuit join from overhead is hard to beat and gives you time and space to fit in with traffic as well as the best look at the windsock prior to landing. At the PPL stage, most good flying schools would encourage you to primarily follow this principle but don't forget (as you have now well experienced!) that there are others out there joining at other points in the circuit.

[Andy_RR]

Further to your original post, a lot of higher performance aircraft, especially turboprops and airline flights for example, do favour straight in approaches. They generally offer more efficiency...


So as not to impede commercial aviation, pilots flying
recreational or sport aircraft for their own enjoyment, or pilots
flying GA aircraft for their own leisure, should consider giving way
to aircraft being used for ‘commerce’ provided that the
inconvenience to their own operation is not great and it can be done
safely. Operators of commercial flights should never expect a give
way offer to be assumed or automatic. Any offer to give way must
be explicit and its acceptance acknowledged.



This is undeniably good practice, but it comes with the reciprocal consideration of the commercial guys not bitching and moaning about "subsidizing" the costs of recreational/sport/rich boys flying.

[davebowyer]

On this forum, and over at Downwind (http://www.downwind.com.au/index.php/community/pilot-forum/5-pilot-experiences/6671-joining-circuit-on-basefinal-legs-good-or-bad), I've had heaps of good comments and feedback on this topic. It's given me much good food for thought. Thanks everyone!

[Old Akro]

We need to remember that joining on base was accepted and common practice for decades. As far as I know there was no history of accidents that caused CASA to change. I believe it came out of a risk management meeting with a bunch of faceless Canberra bureaucrats.

In the "good old days" we seemed to get along happily without transponders, higher traffic movements and a greater diversity of aircraft in the circuit. I agree with Tony Kern when he talks about a need recognise that safety is more to do with taking personal responsibility rather than looking for the system to save us.