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.
I was descending for a visual for Runway XXL. As I descended lower from an initial cruising altitude of 8,000 feet I began experiencing occasional moderate turbulence.
During the initial descent I received a single stall warning, which I attributed to the sharp turbulence I had just experienced. As I descended lower the Cirrus SR22 experienced increased moderate turbulence. The Controller had also advised a prior aircraft of wind shear on final approach.
As I continued the descent and intercepted the final approach course, the stall warning system started triggering repeatedly with both visual and aural alerts. I also noticed the PFD (Primary Flight Display) indications seemed incorrect with the bottom of the speed tape red in color. I had slowed to below my flap speed and decided to add in 50% flaps, which seemed to quiet the stall alerts momentarily.
As I continued the approach the alerts returned almost continuously along with the strange PFD indications. I disconnected the autopilot and found very heavy control forces. I decided to level off to assess the situation and received an “Autopilot Engaged” aural alert from the Perspective system indicating the envelope protection system had activated. I felt the servo activation in the control yoke and a pitch down movement. At this point I held down the autopilot disconnect switch to override the system.
I immediately advised ATC because I realized I could not safely land the plane and was not sure I had full control with the envelope protection system engagement. After advising ATC I reverted to my training, prioritizing aviate, navigate, and communicate.
I asked my passenger who was sitting in the copilot seat to look down at the breaker panel next to my right leg and pull the autopilot circuit breaker. She could not initially find it but began reading off the various breakers. When she said “stall warning” I asked her to pull it which immediately silenced the continuous alerts.
At the point I felt I had full control of the aircraft and informed the Tower that I had cleared the priority. They issued turn and climb instructions and a handoff to Approach which I complied with.
I was vectored onto the final and executed a safe landing requiring full rudder deflection and heavy aileron use to hold the centerline in the strong crosswind. I also experienced strong wind shear over the numbers. This cemented in my mind the decision to advise ATC.
Some of my takeaways are:
- Having a deep understanding of how the technically advanced systems work is very important in situations like this
- Reverting to aviate, navigate and communicate priority order is imperative when being overwhelmed in the cockpit
- Don’t hesitate to advise ATC. It allows you to do what is needed to keep the flight safe.
- After advising ATC, ATC kept asking questions which was incredibly distracting. Don’t be afraid to use the word “standby” or completely ignore them as you work the problem.
Primary Problem: Software and Automation
ACN: 2107447
I teach pilots to know how to disconnect the autopilot. There’s more than one way as most know. If those 3-4 don’t resolve it turn the master off (hopefully in VMC).
It’s another classic demonstration of why a TAA should not be used for Private Pilot training.
I re-read this and still missed where this was mentioned to be a training flight. In my opinion, students using a TAA in primary flight training makes the pilot even more proficient with the equipment and a safer pilot because of the training they received on it.
Lessons learned from others: Do all practice approaches until proficient before using any part of the autopilot system. Then practice with it but having someone fail a part of it.
Why? Auto pilots tend to hand you the airplane at bad times/points. Because the WX got it outside of the envelope it was designed for. Could be ice, could just be turbulence, or a Microburst.
How many airliners (and others) have crashed because of micro-bursts, and similar things that an autopilot and auto throttles couldn’t handle or anticipate?
The pilot mentions an “envelope protection system” as possibly malfunctioning?
It’s actually called “Electronic Stability and Protection” (ESP), and it’s a function provided in Garmin GFC autopilot-equipped Cirrus SR-22s.
Based on the pilot’s narrative, it sounds like it was working exactly as advertised.
Straight from Garmin: “ESP is a safeguard created to assist you in maintaining safe, stable flight when hand-flying your aircraft. It monitors the aircraft’s flight condition, functioning independently of the autopilot, and it applies a control force toward stable flight whenever pitch or roll deviations exceed recommended limits. ESP can also recognize when underspeed or overspeed conditions are about to occur — such as a stall or too-steep of a descent — and it makes appropriate adjustments to the controls. Plus, if the system detects that ESP has been activated for a specified period of time, the autopilot will engage with the flight director in level mode to bring the aircraft back to level flight. However, if you’re training or practicing, ESP can be manually disabled to allow intentional flight maneuvers.”
So…as the pilot notes in his “Takeaways”:
1. Having a deep understanding of how the technically advanced systems work is very important in situations like this.
He had 396 Cirrus SR-22 hours when this occurred…I hope he got back into the books before he flew another.
extending flaps caused the stall warning to stop…that’s what flaps, lower stall speed.
pulling the stall warning breaker, as his passenger did, will stop the warning also.
control forces heavier when speed was slow…yep. Aerodynamic laws hard at work.
Worked out well, and congrats to you.
Now, turn the automation off and fly for 25-50 hrs without it and learn the plane.
Excellent job. All these autopilot safety systems are as bad as Boeing in causing problems. This pilot got smart and turned the system off. All you have to remember is pitch and power is airspeed. Fly with me you get no instruments and all the safety systems get shut off. Then you really learn to fly. To many have lost the basics. The quality of training these days is very poor. Had a customer who kept telling me his plane felt different on short field landings, it was the autopilot engaging because it thought the plane was to slow. Know your systems and install a switch to shut the whole system down instead of pulling the breaker on the garmin autopilot and others.
This pilot won a heroic struggle against the elements (wind). Would old-fashioned ‘steam gauges’ given a better picture to this pilot? Too much computerized logic ‘thinking’ it’s smarter than the human in the left seat. His excellent airmanship got him safely back on terra firma. Just like the early days when all there was on the dashboard were a compass and altimeter. Flying the plane was the pilot’s job. Good job, pilot. When in doubt, tell the glass panel to go to Hades and just fly the plane. Then thank the Good Lord you made it back to earth alive. Regards/J
Perhaps they thought you sounded confused and were just trying to stay with you.
Advising them you need some time to diagnose the issue and will get back to them would work. But maybe not since you stayed on the inbound course.
Good question for ATC.
“After advising ATC, ATC kept asking questions which was incredibly distracting. Don’t be afraid to use the word “standby” or completely ignore them as you work the problem.”
You left that part out of your story. The part where ATC kept calling.
“This is an excerpt from a report made to the Aviation Safety Reporting System. “