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Standard overhead joins wrong...?


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ChrisB
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Having received the runway in use and circuit direction when close to an airfield I do some hurried mental gymnastics to work out how to approach for a standard overhead join. I recently discovered the SD “Make Approach” function and was very pleased to see there is a “Standard Overhead” join option.

The first time I used it in the air was arriving at Enstone. I selected Make Approach, Runway 26, Standard Overhead. A nice big purple arrow appeared “for guidance on where to join” (to quote the SD video tutorial). I started heading towards the arrow, but after even more hurried mental gymnastics realised I would be joining from the opposite direction to that required and made corrections.

I have since used the same function arriving at other airfields and they are all wrong. According to SD a standard overhead join is approached from the dead side, with descent on the live side to join the circuit. According to the CAA a correct standard overhead join is approached from the live side, with descent on the dead side to join the circuit on the crosswind leg.

This is more than just misleading it is plain wrong. At worst, a pilot following SD’s guidance would conflict with a pilot doing a ‘correct’ overhead join. At best he would be joining high on the downwind leg and making a total hash of the circuit.

I’ve attached below a screenshot from SD and a CAA diagram of a standard overhead join to illustrate my point. Comments welcome – is there something I’m missing here?

Chris




DaveWhite
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What you are being shown is correct - the purple arrow shows you flying over the upwind end of the runway and turning right into the right hand circuit for 26.

The generic OHJ diagram you show is for a left hand circuit.

It's worth noting that the purple arrow shows your entry into the circuit from after you have joined overhead and descended deadside.  It can't show you the direction in which you join overhead because that will depend of course on the direction from which you approach the airfield.

I've never been a great fan of the generic UK CAA diagram because it only shows what you do when joining from the easiest direction - from the circuit side perpendicular to the runway.  All you do then is fly directly across the runway and descend (deadside), whereas it would be more helpful if it showed you the 'roundabout in the sky' that you should fly when approaching from any other direction, until you get to the point where you are heading towards deadside.  At that position you stop your turn in the 'roundabout', continue to deadside, descend and join crosswind.  (Apologies if that was teaching to suck eggs but it might help someone else)

Edited 9/5/2022 3:57:55 PM by DaveWhite
ChrisB
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I understand what you are saying Dave but I respectfully disagree. You are perfectly entitled to interpret “standard overhead join” as you see fit, but I prefer to use the CAA’s description. You can certainly join crosswind, but that is not a “standard overhead join”.

As per the CAA guidance, when joining overhead I always position myself as shown in the diagram – heading towards dead side – whatever direction I’m arriving from. This is quite clear from another CAA diagram (this time from the Skyway Code – attached below, with my red highlighting). It clearly states “If arriving from the other side of the aerodrome to that depicted, circle overhead so as to start from a similar position”. This is done well above circuit height, typically 2,000’.

In SD the dead side is indicated by the ‘shadowed’ rectangle. According to CAA (and me!) you should always join heading towards the dead side when conducting a standard overhead join, and descend dead side from joining height to circuit height.

You state “It's worth noting that the purple arrow shows your entry into the circuit from after you have joined overhead and descended dead side”. What is the source of that statement about the purple arrow? SD themselves clearly state that the purple arrow is guidance on where to join – not where to enter the circuit. Admittedly “joining” implies entering the circuit (what else would you be joining?), but I hope we could both agree that we are talking about the flight phase just before entering the actual circuit, at circuit height.

I am not intending to be confrontational but, again with respect for your viewpoint, I do firmly disagree. I think SD is great and would never willingly fly without it, but in this instance I believe it is wrong.

Chris


DaveWhite
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I'm not saying you join overhead crosswind - I'm saying just what you have described. We are agreeing.

You join into the overhead (say 1,000 ft above circuit height) and turn (if necessary) until you are facing deadside, at which time you will make a turning descent (in the direction of the circuit) to circuit height on deadside, joining the circuit itself via a crosswind leg over the upwind numbers.

That's a standard overhead join. The CAA diagram shows the simplest possible join above circuit height where there is no necessity to turn until you're facing deadside because you are already doing so because of the direction you entered the join.

The source of my statement about the purple arrow is by inspection - it's what SkyDemon does.  

You can demonstrate it for yourself by planning a flight to an airfield more than once, each time arriving from different compass directions.  You'll see that the purple arrow is oriented relative to the circuit exactly the same whether you arrive from N, S, E or W.





Edited 9/6/2022 9:38:56 AM by DaveWhite
Tim Dawson
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As Dave says, we don't know where you're coming from, so we draw a big fat arrow starting somewhere in the middle of the deadside but turning in the circuit direction, and it's up to you how you get there. This will obviously vary depending on whether you're arriving from the dead side, or the live side, or somewhere in between.

Possibly you were expecting SkyDemon to join all the dots and connect your route to the circuit, no matter what direction you were coming from?

Davidojc
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Hi Guys where is the make an approach toggle.
Thanks DC


DaveWhite
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Davidojc - 9/6/2022 5:46:52 PM
Hi Guys where is the make an approach toggle.
Thanks DC


Navigation Options : Approach Tools : (Enabled)

ChrisB
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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.

Tim Dawson
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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.

Since we understand each other, this thread can be left to gather other people's thoughts, as a change in behaviour that has worked in one way for many years is being suggested.

David Johnstone
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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.
The problem was that the other aircraft had a different interpretation of an overhead join to the CAA approved one.
I was approaching the airfield from the live side and so carried out the standard OHJ as per the CAA chart.
The other aircraft was approaching from the dead side.
I reached the airfield first and called overhead. 5 seconds later the other aircraft called overhead. I could not see him so commenced an immediate descending turn to the left to join the circuit for 27Left
The FISO on duty asked if I had contact with the other aircraft, I replied Negative, but immediately confirmed that. I could now see a twin on a collision course about 100 yards off my right wing. Collision avoided.
But !!
Lessons learned, the twin carried out a dead side join ignoring the fact that I was already established in an OHJ. 
The OHJ only works safely if people get into a one way system, imagine coming to a roundabout and people go either way depending on how the approach the roundabout. Suicidal.
The sad truth is so many people have an incorrect understanding of the OHJ.

GO

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