Thursday, 15 March 2018
THE EMERGENCY PROCEDURE NOBODY PRACTICES …. And why we all should!
Acknowledgements: John Zimmerman (AIR FACTS)
"Turbine-powered airplanes don’t crash very often these days, so when they do we should all take notice. Upon reviewing such accidents from the past few years, it’s clear there is a disturbing trend in modern cockpits: pilots struggle to control the airplane after the autopilot suddenly quits flying. Now before you start bemoaning the current state of stick and rudder skills and urging all pilots to start flight training in a Cub, let’s consider another option.
Can you recover if George walks off the job?
Air France 447 is probably the best-known accident, since it garnered non-stop news coverage and the airplane wasn’t found for almost two years after it went down in the Atlantic Ocean. While the accident was complicated, the short version is that the autopilot kicked off at night, in IMC, over the ocean, and the pilots proceeded to stall the airplane and fly it stalled all the way to the sea. The important lesson is that the pilots were not in the loop. When suddenly forced to fly the airplane, they did not have the situational awareness or the training to handle it.
Another accident, and one that received less attention, involved a Pilatus PC-12 in Florida. The final report is not complete yet, so all the details aren’t known, but it’s clear that the pilot lost control of the airplane in IMC and it crashed nearly straight down. The question is why? One plausible theory is similar to the Air France accident: the airplane, at near gross weight after making a fuel stop, was climbing through 25,000 ft. in the clouds when the autopilot disconnected due to turbulence.
The Pilatus has a stick shaker that will disconnect the autopilot at high angles of attack, and the slow speed required to climb at FL250 plus the convective weather in the area could have caused exactly that. This is not unique to the PC-12 – most autopilots will disconnect if the turbulence gets bad enough.
If he did lose the autopilot, the single pilot, who was relatively new to the airplane, may have simply lost control in the clouds. I’ve been in a similar situation and it’s quite unnerving, as you go from monitoring the autopilot to flying (often with no flight director) in an instant. You do not have long to get the airplane under control.
None of this is to suggest that autopilots are dangerous, or that they should be avoided. Modern autopilots are nothing short of amazing, and I firmly believe they increase safety. For example, single pilot IFR is certainly possible without an autopilot, but the safety margins are thinner. If you have an autopilot, you should use it. If you don’t have an autopilot, you should add one.
But even the most ardent autopilot supporter has to admit they have limitations. And in some critical situations, like the accidents described above, autopilots essentially throw up their hands and say to the pilots, “your airplane!” There is no warning that the autopilot may be about to shut off and no in-between state: it’s there one second and gone the next.
One response to this could be to design autopilots that react better, and some pilots have advocated this approach. Theoretically, autopilots could have some type of fall back mode, where they don’t disconnect completely, but revert to basic attitude hold. Better annunciators are another option, where the autopilot explains why it disconnected and whether it can be turned on again.
Some of this may be possible, but a far more practical (and more affordable) option is for pilots to regularly practice this failure scenario. Call it unusual attitudes for modern airplanes – we need to experience what it’s like to be unexpectedly thrust on stage. I had never done it myself until very recently, and in talking to a number of other pilots, I haven’t met one yet who does this on a regular basis. We all practice emergency scenarios that are exceedingly unlikely to happen, like engine failures, and yet we ignore a scenario that has proven to be both possible and fatal.
The best way to practice autopilot unusual attitudes is to go up with an instructor or safety pilot and fly like you would on a real trip. Put on the hood and engage the autopilot, then have your co-pilot randomly disconnect the autopilot, both straight and level and in turns.
Be realistic – if you spend a lot of time with your head down, looking at your iPad, practice recovering from this position. Staying in the loop is a critical part of the exercise, since many of us may relax in cruise flight and may not be spring-loaded to fly.
In particular, it’s the transition that counts. Many instrument pilots feel a little uneasy when they first transition from VMC to IMC, especially if they haven’t flown lately. The same is true with autopilots: the key is those first few seconds after you lose the autopilot.
It’s basic attitude flying, and the focus should be on flying the airplane and nothing else. Also consider that the autopilot may have disconnected due to an AHRS or air data issue (as in the case of Air France), so it’s a time to rely on your profiles. What power setting and what pitch attitude lead to straight and level? You should know that cold.
Curmudgeons may scoff at this as another sign that modern avionics have made us all bad pilots. But I think that’s an overreaction. Even the best new technologies still have quirks to learn and new procedures to practice. Nobody argues that celestial navigation is better than GPS simply because a GPS receiver can fail and stars don’t.
The trade-offs are worth it. Practising autopilot failures is just part of being a safe, modern pilot who embraces all the tools available. Don’t just read about it in the manual – get out there and fly it!"