Mid-air collision

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TheGreenGoblin
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Re: Mid-air collision

#21 Post by TheGreenGoblin » Thu May 20, 2021 11:19 am

Boac wrote:
Thu May 20, 2021 11:15 am
We have no timings or the durations these aircraft were flying on these headings and when they changed track,
See ian's post at #15 - there are timings and headings.
Ok, then on the basis of that sketchy information, please free to produce a diagram, with its locus on the VOR, with aircraft headings, relative positions, and altitude changes over time, showing how this accident occurred, and who was to blame, and I shall ask some probing questions when you have! =)) ;)))
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Re: Mid-air collision

#22 Post by TheGreenGoblin » Thu May 20, 2021 11:28 am

Boac wrote:
Thu May 20, 2021 11:15 am
We have no timings or the durations these aircraft were flying on these headings and when they changed track,
See ian's post at #15 - there are timings, positions and headings. PXI appears to have made a 180 but not changed altitude?
We can both agree on that point (see blue highlight)....
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Re: Mid-air collision

#23 Post by Boac » Thu May 20, 2021 11:31 am

showing how this accident occurred, and who was to blame,
I read both homing to the VOR from the north-east, PXI then turns ?to track an outbound radial?

a) That is what seems to be the case
b) Little point in allocating 'blame'?
c) Training procedures look as if they need tightening up. I assume SA Aviation Law decrees IFR at night and IFR requires quadrantal FLs outside controlled airspace?

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Re: Mid-air collision

#24 Post by TheGreenGoblin » Thu May 20, 2021 11:33 am

Boac wrote:
Thu May 20, 2021 11:31 am
showing how this accident occurred, and who was to blame,
I read both homing to the VOR from the north-east, PXI then turns ?to track an outbound radial?

a) That is what seems to be the case
b) Little point in allocating 'blame'?
c) Training procedures look as if they need tightening up. I assume SA Aviation Law decrees IFR at night and IFR requires quadrantal FLs outside controlled airspace?
So we are are ad idem then on those points, including c) which pertained when I flew tin cans in SA back in the 80's.

https://aviationdirect.co.za/semi-circular-rules/

http://www.caa.co.za/Aeronautical%20Inf ... 20in%20any

There are some variations on the theme in SA, and with respect to the airspace around Johannesburg.

FAD1.JPG
FAD1.JPG (44.65 KiB) Viewed 247 times
http://www.caa.co.za/Latest%20Accident% ... 052021.pdf

Midair.JPG
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Re: Mid-air collision

#25 Post by TheGreenGoblin » Thu May 20, 2021 12:44 pm

Both selected the local QNH, both were flying at an altitude of 6700 feet. Both were undertaking night flying where where quadrantals using flight levels (below the FAD altitude upper limit of 7600 feet) should have pertained. ZS-PXI doesn't appear to have changed altitude/flight level after the 180 degree turn to take up a heading of 030 degrees (one assumes it was tracking the same). The aircraft collided North East of the VOR. Neither aircraft was tracking directly inbound or outbound, to or from, directly over the VOR is seems. Both aircraft were being flown by PUT's with the respective PIC's being instructor rated pilots. Visibility was good with an almost full moon. Sky was clear.
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Re: Mid-air collision

#26 Post by Boac » Thu May 20, 2021 2:15 pm

It doesn't look as if the terrain has a high SA, so QNH was not relevant.

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Re: Mid-air collision

#27 Post by TheGreenGoblin » Thu May 20, 2021 2:51 pm

I am was talking to a Saffer PPL friend in Jhb and he was telling me that there was some question as to whether one of the aircraft had announced their position, altitude, heading and intention on the correct frequency. The VOR is in uncontrolled airspace and relies entirely on such calls for traffic in and around FAD182. Clearly this will be one hole in the cheese for sure. Actually two holes. The aircraft that issued the Mayday was on the incorrect frequency. Go figure! It was also the one that did the 180 turn.
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Re: Mid-air collision

#28 Post by Boac » Thu May 20, 2021 3:02 pm

Whilst sweating the small stuff, remember they crashed because they were both at the same altitude and neither appear to be looking out.

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Re: Mid-air collision

#29 Post by TheGreenGoblin » Thu May 20, 2021 3:05 pm

Boac wrote:
Thu May 20, 2021 3:02 pm
Whilst sweating the small stuff, remember they crashed because they were both at the same altitude and neither appear to be looking out.
All that too but I would contend that not reporting one's position in such an area (after having being warned about being on the wrong frequency - read the report) is a pretty big mistake in the chain.
The ZS-PXI tracked as per the flight plan and entered FAD 182 at 17:00:50Z flying a heading of 210° towards the GAV beacon at 6 700 feet (ft). At 17:09:44Z,the aircraft could be seen on Secondary Surveillance Radar (SSR) set to commence a left turn. Approximately 1 minute later, the aircraft completed the turn and flew a heading of 030°, remaining on the same altitude of 6 700ft. According to radar data, the aircraft was flying at a ground speed of 95 knots (kts) at the time. The pilot-in-command who was flying an aircraft with registration ZSCPL from the same aviation training organisation (ATO) called the pilot of ZS-PXI on the VHF radio frequency 124.80 megahertz (MHz) and reminded him to change frequency to 122.35MHz when entering FAD 182, which he acknowledged.
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