The odds of multiple instrument failures, all showing the same erroneous result, are infinitesimally small. I really do not think that was at work here.
But your question, “why don’t pilots trust their artificial horizon“, is a matter of basic human physiology. In order to fly IFR, you have to overcome physiology.
The vestibular input to your brain has been a developed pathway since you were born, when you learned to walk, you learned to rely on the vestibular input for balance, it’s how you determine when you are level, how to put one foot in front of the other.
It’s extraordinarily powerful. Most people have never experienced a disconnect between what their visual input and vestibular input. A lot of pilots who have never flown truly high-performance aircraft have never experienced it, at least, not significantly.
I watched a friend* of mine fly a perfectly good airplane into the water one night. It was March 15, 1996, on the John C. Stennis. You’ve never experienced dark until you’ve been on an aircraft carrier at sea, at night, under a cloud layer. There are no lights. There are no stars. There is absolutely no way to determine where the horizon is because everywhere you look is the same uniform inky blackness. An experienced naval aviator. A pilot with extensive training there was nothing wrong with the airplane, most likely scenario, because the airplane sank in 15,000 feet of water, was that he looked down at a warning light and then looked back up immediately, following a catapult shot. His plane nosed over and descended into the water. I was on the LSO platform at the time, watching the launch, and I grabbed the radio, realized I was on a different frequency than he was, and by the time I had rotated the selector, he was gone.
A significant longitudinal acceleration, like a catapult shot makes you feel that you’ve been tilted backwards. That is the effect of the fluid in your inner ear, rushing backwards under the acceleration. It makes you think that you’ve tilted nose up. You haven’t, of course, but the somatogravic illusion is strong.
https://en.wikipedia.org/wiki/Sensory_illusions_in_aviation
https://skybrary.aero/articles/somatogravic-and-somatogyral-illusions
Things like a strong acceleration, like a Lear 55 on takeoff, confuse your inner ear, and the effect is more powerful than people realize. I’ve watched it kill an experienced, capable and disciplined crew.
I sincerely doubt that the crew of this Lear 55 had the skills, training, and discipline of my friend, and it is my belief that they simply succumbed to the same illusion that overpowered him.
*LT Don Cioffi, from Freehold, NJ. A good man, a good pilot, and a good LSO.
