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 scrubbed from the reports.
On short final to a visual landing, the autopilot (which was turned off) pushed the nose towards the ground. I was surprised. I pushed and held the autopilot disconnect, recovered, and landed.
I was familiar with the ESP (Electronic Stability & Protection) feature on my recently installed Garmin GFC 500 autopilot in theory, but seeing it in practice was scary.
Landing speeds for my Bonanza 33 are 64 to 70 knots depending on weight per the POH. I was light, winds were light, and I intended on landing at 68 knots. The GFC 500 ESP pushes the nose down below 70 knots.
Note that a V Tail bonanza with the exact same flight characteristics has a GFC 500 ESP speed of 65 knots, which is better.
This is a hazard that needs a software modification to correct.
Primary Problem: Aircraft