Not sure it is the issue. The picture so far is certainly not inconsistent with a crosswind join that was flown overhead the upwind numbers and continued on an appropriate track.

BUT,

By the UK rules, that cross-over is at a defined place and with one a/c 500 ft above the other. Isn't that what the airways tolerate too ?

They are on an overhead join so long as they are established at circuit height before entering the "live" part of the circuit - same would apply to the 45 degree US join, ie a/c should be in level flight before entering the the live part of the circuit.

The way to reduce "blind spots" is to ensure proper lookout - wherever you are.

It's ok joining on the 45 if know exactly where the airfield is. But, I find that if I'm trying to find a small airfield I haven't visited before it's easier from 2000ft agl rather than circuit height 1000ft. From the overhead it's easier to spot the wind-sock, signal square and observe traffic in the circuit and generally get myself orientated to the field. To use the 45 degree method you have to know the runway in use to plan your circuit which probably implies being given instructions by ATC. "Horses for courses".

Both the UK "standard rejoin" and the USA "45 degree rejoin" work. I use them both and am not sure which one I prefer.

However, unless pilots are disciplined to fly either given procedure correctly, these accidents will always happen despite all the "lookout" in the world.

Couldn't agree more. I've always found the UK join rather dangerous.

There is a US way of doing so, sometimes referred to as 'teardrop arrival' which pretty well describes the path of the joining a/c. In a nutshell you overfly the field MIDFIELD above circuit (pattern) height, typically at 2000 ft, of course taking potential jet circuit heights into account. This way you get to a great vantage point and see everything that's going on below you: traffic, windsock, a/c on ground. Importantly, doing this midfield you are not in anybody's way. You then proceed live side outside the pattern and descend in a long curved path (that's where the 'teardrop' comes from) upwind. Thus you have any traffic joining on the 45 in sight and can adjust accordingly. You then fly a standard 45 join. IMHO safest way to do it.

Have asked this before but where is the statistical evidence that the US 45 deg join is "safer" than an OHJ?

We might all have some sort of subjective feelings about which is safer but until someone can show me stats on airproxes/collisions in the circuit for different types of join, I am yet to be convinced.

I don't think that their is any statistical evidence in favor of either procedure.

Both are flawed if the procedure is not flown correctly.

In the UK over the numbers means - over the numbers

In the US intercept at 45 degrees means - intercept at 45 degrees.

Making up your own joining procedure in either country, in a busy circuit, with all the lookout in the world, will not stop this happening again.

Maybe, a N reg parachute ;) will be mandatory next, along with Mode S and 8.33kz spacing.

In the US there is nothing to stop you flying overhead the airfield at a safe height first then fly away turn and descend out of the way of the airfield before joining on the 45.

The key is to have the big picture in your mind. For two to collide like this at an ATC controlled field is nuts, especially because both pilots would no doubt have been listening to RT for some minutes before the event and should have been aware of the other.

Englishal - you are right, both aircraft should have heard one another on RT, but, Shoreham does not have radar. They probably rely solely upon pilot information.

If for example, aircraft A calls up for departure, for a standard circuit and whilst accelerating in the roll hears aircraft B call up "letting down deadside for rejoin" Aircraft A for sure would be looking out for aircraft B.
Once aircraft A has reached 500ft he would then turn left still ascending onto crosswind still looking out to his left for aircraft B "joining" crosswind.

Why would aircraft A be looking directly behind in the climb on crosswind. One doesn't expect a prop chomping away at your *rse from behind.

When I call downwind and another aircraft calls finals, the picture that I am expecting is the other aircraft to be in front of me, having completed base leg and descending on the runway heading, but after this discussion I will now be looking everywhere for that traffic.

Don't bank on it. I once flew through Shawbury CMATZ on my way back to Halfpenny Green and spoke with ATC there. Also flying through the MATZ was an aircraft which had left from Blackpool. Having been given the QFE X4 and replied "Roger" X3, it was the FI with him who answered correctly on the 4th time. Now, I had heard him and he, no doubt had heard me but when he arrived in the circuit at EGBO and was told he was No2 to me his response was "Visual with HIM!". I do not have a male-sounding voice but I suppose I should be grateful that he had at least seen me. :\

Absolutely agree. Just a thought - as earlier posts have said, a final ATC clearance for this join is typically given when positioned north abeam Worthing Pier to "descend to circuit height, join crosswind and report downwind". I have often found when joining crosswind at Shoreham (eg. when traffic is light) that I am not asked to report crosswind. So, there could have been a period of a few minutes with no ATC exchange with the joining a/c before the collision as it hadn't quite reached downwind.

Having done that very crosswind join so many times, once over the upwind numbers I'm busy looking at the downwind leg to merge with any traffic approaching from my right and would not have seriously imagined (until now) there would be a serious conflict with an a/c taking off below and to my left, especially if the take off clearance is for an immediate left turn out - which is unusual, but could well turn out to be the case here as it fits better with the evidence available and provides a scenario in which every party involved acted professionally and rationally.

I find Shoreham ATC superb at alerting and helping to deal with possible conflicts.

This thread has personally made me question a whole load of assumptions and issues about crosswind joins etc.. Many thanks.

Spotthedog - your description of the crosswind join in para 2 is spot on :ok:

Had YOU been that DA40 on the day in question, you would have seen the other aircraft climbing crosswind (parallel with your track) in your 3 o clock position, range approx 1 mile/1.5 miles.

Have you seen the geographical photo's on previous pages ?

I have seen the geo pics and my thinking is that the RV wreckage site (and the area to its south east towards the children's play area and the A259 bridge) is a much better indicator as to where the collision took place than the other sites marked .. based upon:

a) the earlier observation in this thread that a prop can travel a significant distance when it detaches, and possibly other smaller pieces too.

b) Witness statements suggest the RV fell speedily from a low height (although we don't know what height yet do we - even 1100 feet might appear "low" to a muggle, as to "400 feet" - surely this isn't true but time till tell).

c) Witness statements suggest that the RV appeared to turn away from the houses (on the east and south of the A259) and a bridge (which surely must be the A259 bridge and not the A27 bridge as quoted in the Mail article).

So if I was the DA40 joining crosswind (over the numbers and then tracking over the recreation park towards the A259 bridge) the other a/c would probably have been coming at me from below and from the left as it had just taken off from R20 and, the presumption here, made an agreed early left turn, in order to reach the point of collision.

But suppose, as you suggest, the RV had continued on a more 'normal' R20 departure, it still would have to have turned sharpish left and departed the published circuit track at some point, in order to approach me from my 3 o clock. But yes I would have stood a better chance of seeing it ... and it me. But I have several problems with this scenario so it seems less likely to me - based on what we know.

Early Left Turns EGKA
 

I will admit to sometimes not following the circuit pattern when departing 20 and going off to the east.

If im doing T&G,s my focus is on a cross wind climb out of 110deg until I reach circuit height of 1100ft

But if im going east I now realize that once IV crossed the coast I have forgotten the circuit pattern and followed the coastline which is 80deg as it feels safer to hug the land rather than the wet water.

Probably its due to my C152 not have such a great rate of climb as compared to other high performance planes that I have never reached 1100ft as I went under the Crosswind / Downwind area of the circuit.

However im going to make sure I keep to the pattern from now on

So, from this, and foregoing information, I understand that each aircraft could have been somewhat "out of position" relative to what would normally be expected? The DA40 was crossing the runway centerline farther along the Van's takeoff path than the Van might have expected (and could not see down, as a wing could block that view)? The Van's perhaps had the capability of a climb rate after liftoff, which would enable it to be higher than normal along it's departure path, and maybe even had a pitch attitude which would lessen the forward field of view?

Would you typically fly a square circuit in a Vans? Could it have been flying a tighter oval circuit with an earlier lift-off point due to a t&g?

500man
 

You can fly a tight oval circuit in any aircraft, but it is very bad practice to fly a circuit that is not the one published.

A number of years back a Cessna 150 flown by a mate ( with a young passenger) was hit by an aircraft doing a non standard circuit, all were killed.

Before anyone jumps on me this is a general comment as I am not in a position to comment on the Shoreham accident.

Why did they hit?
 

Reading the aaib report it looks like the DA40 had the RV in its 2 oclock position for about 45 seconds. With two experienced pilots on board I would have hoped that one of them would have seen it, or perhaps they were still flying on instruments and not looking out of the cockpit

Firefly Bob wrote:

Is that a demand that can ever be answered? First of all, you'd need a significant number of accidents to work from. Secondly, you'd need to account for differences in pilot training and familiarity with procedures when you were defining your populations for each group.

Are you building a Luciole?

Would anyone like to read that AAIB report on page 6 (of the PDF; fig 3) and compare the RV's track with the published Shoreham circuit pattern ?

Not suggesting who (or anybody) might be in the wrong place, but the two are quite different in how far out over the water one should climb before turning left to join downwind.

peterh337

The AAIB view appears to be that the Shoreham diagrams are "generic diagrams", not navigational maps to use to refer to ground features / tracks. With one exception, and that is the 20 degree turn after takeoff on 1 runway.

I do note that the published tracks, if indeed they are intended tracks, are so far from Shoreham they take you outside the ATZ :confused:

NoD

My look is that the tracks are per published procedures.

The RED track seems to show
1 - A staight out departure with a teardrop (to the left) turn back to SHM to commence instrument practice(as per the detail of practice instrument training)
2 - What appears to be appears to be two trips around the hold (at about the published distance, which of course is considerably outside the ATZ)
3 - Exiting the hold, on the NDB 20 outbound (with a base turn that is significantly too tight)
4 - Regaining the inbound track to SHM then breaking off to the right for some airwork (all consistent with normal procedures and the AAIB detail)
5 - Airwork to the West
6 - A crosswind rejoin, pretty much along the track line previously used by the RV
7 - One dot beyond the collision point, then a turn to the airport with loss of radar contact halfway there.



The Blue track (the RV) shows

1 - the general handling to the West
2 - A crosswind join over the numbers (i.e. the correct location)
3 - A pattern where the downwind leg looks about 1/2 KM closer to field than that published, but in all other respects consistent with the track.
4 - A departure (the T&G) with a turn commencing 1/2km or less earlier than the track published
5 - A downwind slightly inside of the published track
6 - A loss of track at the collision


All looks pretty much as per published procedures and the circuits seem to be slightly inside the referenced tracks.

ISTM that had the RV come out further over the beach (on the runway track) then a) that would have destroyed the constant-aspect feature which formed such a big part of this accident and b) he might have had a better chance of spotting the DA40 on his LH side.

Of course "nobody" likes to fly any distance over the sea.

In general, I find it much easier to look for circuit traffic when well away from the circuit. Once in the circuit, you have to watch various things and lookout is hard unless somebody is more or less straight ahead, or within a +/- 45 or so degree arc left/right.

It is interesting the very detailed radar information that is available from the NATS head, and yet no radar in the tower at Shoreham.

Its a hobby horse of mine but the last time I asked its £100K plus annual fees to place a repeater in the tower although the "real" cost is far far less.

Whether Shoreham would want a repeater and whether they could make use of the data I dont know - but I do know they certainly couldnt afford one at these rates. In contrast Calais does have a repeater and it seems to me chatting to the ATCO it is a very useful tool.

Its interesting that no comment is made in the report with regards to whether the availability of this data could considerably enhance safety.

NATS' accounting policies are very political, not least because most light GA pays no route charges.

However you would also need radar qualified ATCOs which is another salary increment.

Peterh337 yes of course. The cost of a radar qualification is probably not that great; the cost of a radar feed prohibitive. It's not going to happen.

However as I understand matters the investigators will put on record their recommendations which if implemented could reduce the chances of a similiar accident often without direct regard to cost. It would be interesting to know if a radar feed had been available the chances of the accident would have been reduced? If it would have been reduced the reporter has missed an opportunity to draw attention to Nats failing to enhance safety by making it unviable to share data other than amoung the vary largest airports.

I use onboard traffic and as long as the circuit traffic is transponding this sort of accident would be very unlikely. I don't doubt with the availability of a radar feed the atcos traffic awareness would be greatly enhanced.

Mode S traffic alert
 

Well here is a thought. As NATS charge a stupid fee for what amounts to a data feed for a computer to display a radar image, how about a mode S receiver for the control tower. This could snoop on the mode s replies from aircraft with a suitable transponder and produce an alert if they were conflicting. As an alternative I wonder if NATS could have a link to shoreham and instead of sending a radar image, just send conflict alerts. If a suitable threshold for these could be set then the tower would get an alert if a dangerous situation was developing. As this was not displaying a radar image I would imagine that it would not need a radar qualified controller and would enhance safety.

Looking at the G1000
 

I do wonder if the pilots were to busy pressing buttons on the G1000 or looking at the instruments when in the circuit. I do find it difficult to imagine that they did not see the other aircraft for about 45 seconds especially as there were two qualified pilots in the cockpit who should have been looking out.

This technology exists but I think that ATC would need a quick release window pane in the tower, to jump out of if anybody saw them use it :)

In this case, however, I don't see any ground based surveillance technology would have helped. TCAS in either aircraft (and Mode C or S in the other) - yes.

The equipment under discussion, which is used by Aerodrome Controllers in VCRs, is called an Aerodrome Traffic Monitor (ATM).

Peter wrote:

Here is the first paragraph in MATS Part 1 about the ATM, with my bold text:

A google search for CAP 493 will find you the whole document. The relevant section is Section 17 of Chapter 1.

:rolleyes:

Ah, so what should it cost for Shoreham to have a radar repeater and how might this enhance safety in the approach to and in the circuit?

Uk and air traffic services rules are quite hard to follow for those of us not from the UK! :)

As for radar display in the tower: I worked TWR with radar display for the twr controller from 2002 to 2009. At two airports with a majority of VFR operations, including light aircraft and helos, both MIL and CIV.

One year we did not have radar info available for "twr traffic altitudes" due to failure of one of two sensors. That was a hard year.

Even if you spend 90% of the time head up, looking out, there are situations where a radar display with SSR info is valuable. Traffic blocked by the tower roof, and traffic hidden by surrounding terrain. (For the not so flat parts of the world)

We did not use civ overhead joins, but often MIL break pattern for light training aircraft. Break turn allways hidden by the tower roof. Radar was nice to have then.

Somebody told me the Kinetik box shows position of all Mode S traffic.

How does that work, for aircraft with Elementary Mode S which is not permitted to radiate that data? Non-EU reg Mode S aircraft will probably be radiating it (because the "Elementary" v. "Enhanced" Mode S is a purely European invention) but an EU reg banned it for local reg ones.

Such a box would benefit ATC situational awareness but - like London Information which has similar unofficial radar access - they would still not be able to legally make a radio call to an aircraft which they thought would benefit from the information.

It depends. With the benefit of a radar feed they now know exactly where to look for the aircraft and having seen them that much earlier / recognised the potential for conflict issue appropriate instructions.

Sure... what I meant to say is that they would not be allowed to make a radio call which revealed they can see where somebody is, using "radar".

They would have to be discreet in how they use it.

The sooner we have ADS-B the sooner this will be possible to do properly, and the regs on radar visibility by non authorised ATC/AFIS personnel will de facto fall by the wayside, which will be good for everybody.

AAIB report
 

Interim report is on the AAIB site under 06/12