GNSS
Yip, there is a GNSS app, with a step decend. They could have been "out-of-step" It happens so darn easily, maybe a bit of complacency. One tend to forget a step decend if you think you know the plate, ive seen it in my own experience. Doing a letdown with a citation in west Africa - reduced visibility, but with the ground and runway insight. I told my FO to stay on the letdown as its good practise. Asked him if he would like to brief me on the plate and he replied with "i know the procedure" He went out of step with me keeping visual contact outside. Obvioulsy there was a reason for the step and I told him to look up - there was a huge hill right infront of him! Great experience and a good lesson. As I said, it happens so bloody easily!