The roundabout concept makes sense, so its in the same direction as the circuit at 2000ft, everyone enters at whatever position suits them but drops out of it when they reach dead-side. Presumably if you happen to arrive on the dead-side you can just descend as you go through the deadside and slot in like when you join the circuit. What if you don't know the circuit direction, perhaps if its unmanned or you need to see the big square runway direction sign? 

Overhead joins are straightforward, but the CAA poster is misleading as it creates the impression that you can only join it from one direction.

The reality is that it’s a big roundabout in the sky, with a diameter slighter longer than the runway in use. You join it from any direction, always turning in the circuit direction, and keep going round until abeam the landing threshold when you start your dead side descent to be at circuit height as you go crosswind.

SkyDemon doesn’t depict all of that so it just gives you the final crosswind descent in the correct direction to a nominal circuit. It would be better if the nominal circuit bit was removed as it serves to confuse.

+x

 

Tony N - 11/25/2023 8:32:08 AM

Chris,

I think the SD function is simply to position you in the, generally, correct location to conduct the type of join you have selected.

You really shouldn't be looking at your SD device when in the circuit - maximum lookout required in that, potentially, busy aviation environment.

I may quickly glance at my SD display to see if I am, more or less, following the necessary circuit path, especially at an airfield I haven't visited before, but that is about it!

Tony

Agree, I've never actually used SkyDemon in flight, I was just commenting on the confusion over what an overhead join is Vs what skydemon calls an overhead join ...

Chris,

I'm nearing the end of a LAPL course and researching overhead joins as there are so many different opinions its not clear to me what the correct method is. It does seem unsafe to me if different people fly it differently.

This topic is very dear to my heart as several years ago I was very nearly killed in a mid air collision which was graded category A by the airprox board.

I think I understand our point of disagreement. In my experience, if one is joining from the deadline, it is common not to proceed all the way to the live side before turning around and doing a "standard" overhead join, back to the deadside before joining crosswind.

Whatever opinion is held about it, I would hope that everyone could agree the UK CAA prescribes something called a Standard Overhead Join. I have already posted two illustrations of this from CAA publications, and here is a third from one of their safety posters at https://publicapps.caa.co.uk/docs/33/ga_srgwebStandardOverheadJoinPosterJan09.pdf



Note the initial blue line in the diagram, and the key bottom right. The blue line is defined as the “joining phase”. The starting point of the joining phase is always on the live side, and it always continues towards the dead side. It does not matter a jot from which point of the compass the aircraft is arriving – the ideal (CAA prescribed) starting point for the overhead join is always in the same place for a given runway and direction. If an aircraft joins somewhere else it is not a “standard overhead join”.

The descent phase (yellow line) is on the dead side. Turn left and descend to enter a left hand circuit on the crosswind leg. Turn right and descend to enter a right hand circuit on the crosswind leg. The key point is you are by then no longer “joining” – you have already done that (the blue line). That’s not my opinion, it’s what the CAA prescribes. I cannot see how anyone can argue any of the above as the CAA makes it all absolutely clear.

The SD arrival function knows the runway in use (the user selects this). Therefore it could very helpfully depict the ideal place and direction to “join overhead”, which would be the same whatever direction the join is from. It's then up to the pilot to arrive there pointing the right way, but at least she knows where she's heading for. For me the best way to represent this would be a big fat purple arrow, with – optionally – its pointed end turned in the circuit direction. Very similar to what SD depicts at the moment, but (correctly) pointing from live side to dead side.

There are several reasons I am labouring this issue. For me, working out the orientation to join overhead (in the prescribed CAA manner) on receiving runway information is quite taxing in an already high workload phase of flight. SD is generally of enormous help to me but lets me down on this one point.

Despite the rationale given for it being correct (such as “the purple arrow shows your entry into the circuit [Ed: therefore at circuit height, way below joining height] from after you have joined overhead and descended dead side”), which may or may not be true, it is not correct “guidance on where to join” (SD tutorial) for a Standard Overhead Join. I like SD to be accurate.

Finally, it seems to me that it’s a simple thing to correct – or ‘improve’ if you prefer. The purple arrows for the other types of join (Downwind, Downwind 45, Base, Long Final) are all spot-on! All the info is there so why not make the Standard Overhead join correct as well? It was said it can't be done because the direction the aircraft is coming from is not know. As explained above - the direction does not matter! The arrows are drawn correctly for the other four types of join despite also not knowing the arrival direction.