What stops Germanwings 9525 happening again — a suicidal pilot crashing the plane?

Question

I'm unpersuaded and still afraid, after reading What safety rule replaced the now-rescinded two-person rule (after Germanwings 9525)?. What's to stop or prevent another lone suicidal pilot from crashing the plane by suicide? Pilots and people can easily lie about whether they have psychiatric illness. They can readily fake and lie through medical exams and psychological evaluations. Psychiatrists’ experiences of suicide assessment

One of the respondents, however, argued that it was not up to the doctor to question the narrative of the patient.

” It is not the least difficult to lie to one’s psychiatrist, it is rather easy, it is very easy. It isn’t our job to unveil the patient’s untruths.”

The truth about lies

"It’s not just common, it’s ubiquitous," notes Barry Farber, PhD, a professor in the clinical psychology program at Columbia University’s Teachers College and the editor of the Journal of Clinical Psychology: In Session. "Lying is inevitable in psychotherapy," he says.

Farber isn’t just speculating—he’s studied this topic for decades. In a survey of 547 psychotherapy clients, 93 percent said they consciously lied at least once to their therapist (Counselling Psychology Quarterly, Vol. 29, No. 1, 2016). In a second survey, 84 percent said this dishonesty continued on a regular basis.

And while therapists might suspect that they can tell when patients are being less than truthful, research shows this is not the case. In Farber’s study, 73 percent of respondents reported that "the truth about their lies had never been acknowledged in therapy." Only 3.5 percent of patients owned up to the lies voluntarily, and in another 9 percent of cases the therapists uncovered the untruth, notes Farber, who reports on this and related research in a new book, "Secrets and Lies in Psychotherapy," with co-authors Matt Blanchard, PhD, and Melanie Love, MS. "It seems therapists aren’t particularly good at detecting lies," Farber says.

So, in other words, what measures are currently available to prevent unstable pilots from causing harm, given that the psychiatric tests are evidently unreliable?

Answer 1

Any security precaution will be shared with the pilots. Therefore, a determined pilot will know those and be able to find ways to circumvent them beforehand.

What are some of the possible precautions?

• Give both pilots their individual key? Easy - disable the lock before the other pilot leaves the cockpit, maybe by breaking off your own key when it is stuck into the lock.
• Use a numeric keypad for unlocking the cockpit door which can only be reset on the ground? After the first terrorist attack where this system is abused, this will be disabled. And it is easy to figure out scenarios where the terrorists will learn the passcode from an unwitting pilot.
• Similarly to military ground collision avoidance: Don't let the FCS allow too low flight levels outside of terminal areas? Disable the system by pulling the appropriate circuit breakers.
• Let traffic control take over the plane by remote control when limits are exceeded? Easy again - just jam the radio signal. Again, it is easy to imagine scenarios where such a system is abused.

Also, what works for rail-based systems cannot be transferred to aviation. Stopping an airplane in mid-flight does not work as it does with trains.

The pilots have to be able to control the airplane exactly because in an unforeseen emergency they are the last resort which can bring it down in one piece. Taking away this ability does not enhance safety but would be the only basis of really stopping a suicidal pilot.