This is an excerpt from a report made to the Aviation Safety Reporting System. The narrative is written by the pilot, rather than FAA or NTSB officials. To maintain anonymity, many details, such as aircraft model or airport, are often redacted from reports.
After contact with the Santa Clara County Reid-Hillview Airport (KRHV) tower in California, above the landmark known as UTC, we began a straight-in approach to Runway 31R from KRHV at a groundspeed of approximately 85 knots and still in level flight at approximately 2,500 feet MSL.
Afterwards, we began a very gradual descent while I briefed a student pilot on how to fly the straight-in approach to land at KRHV, making reference to landmarks and timing of descent , when we were overtaken from above and on the right side by Plane Y which appeared to be approaching within 75 feet of our plane, both vertically and laterally. The encounter occurred just abeam of the landmark known as Mt. Misery from the straight-in approach (identifiable on the SFO terminal area map).
The intruder aircraft Y overshot our aircraft by at least 10 knots and continued to descend below our altitude.
An ADS-B traffic advisory alerted us to the conflict moments before the encounter, greatly distracting my student during the straight-in approach, forcing me to take control.
We heard no transmission from KRHV control tower indicating that this traffic conflict was imminent.
At the same time, there was another aircraft behind us (Aircraft Z), which I remember hearing on later KRHV transmissions to have been a tailwheel aircraft, which had overshot our aircraft by 30 knots, and was therefore responsible for performing a right – 360° manual rotation for spacing.
The Tower did not inform us directly of this plane, and I did not know its altitude, because the ADS-B did not alert us to this second plane.
Given the significant distraction and uncertainty of the aircraft’s position behind us, I decided to abort the straight-in approach just past Mt. Misery and immediately began a steep climbing right turn from approximately 2100 feet MSL, in order to rehearse the straight-in procedure in the interest of safety, stability of the approach and in the interest of my student.
The tower then asked us “what are you doing”, to which we replied that we were turning back to recover on the final approach to runway 31. The tower then said that we should have informed them of our intentions before “maneuvering”. “, which I acknowledged. It was not clear to me if the aborted approach created a conflict with the Z-plane behind us, as we were at no time informed of their altitude.
The second straight-in approach and landing were then made after turning back over Mount Misery to rejoin the straight-in approach to Runway 31R without incident.
Although it was obvious to me that I had to inform the tower of my intention to abort the straight-in approach even though I was outside of KRHV airspace, I believe the separation provided by the tower was misinformation about Aircraft Y passing us high and from the right, and Aircraft Z passing behind us.
I believe there was also inadequate control of the sequencing of the other two planes, given their significantly faster speeds compared to ours.
In the future, I will query the KRHV control tower before aborting any straight-in approaches to land, in case there is an ADS-B traffic alert, traffic not equipped with ADS-B or otherwise unseen, who could overtake us on the direct approach to runway 31 at KRHV.
Main problem: human factors