The various versions of the ATPL CQB have for a number of years included two questions of this type. One uses the term “wind speed increasing rapidly with height” and the other uses the term “wind speed decreasing rapidly with height”.
The answer we will come to for each of these questions depends upon how we interpret these statements.
If the term “wind speed increasing rapidly with height” means that the wind speed increases as the height above the ground increases, then the correct answer is that the descending aircraft will fly into a decreasing wind, which will cause its ground speed to increase. This increased ground speed (with a constant rate of descent) will cause it to fly above the glide slope with increasing deviation. But this is not the answer that has been selected as being correct by the examiners.
If the term “wind speed increasing rapidly with height” means that the wind speed increases as the height above the ground decreases, then the correct answer is that the descending aircraft will fly into an increasing wind, which will cause its ground speed to decrease. This decreased ground speed (with a constant rate of descent) will cause it to fly below the glide slope with increasing deviation. But again, this is not the answer that has been selected as being correct by the authors of the question.
In both questions, the examiners have selected answers that appear to be based on a different interpretation of the terms “wind speed increases rapidly with height” and “wind speed decreases rapidly with height”. To understand how the examiners came up with these answers we must set aside the obvious conclusion that they are just plain stupid, and try to deduce what interpretation they are using.
Their answers to these questions suggest to me that the terms used should have been something like “wind speed increases rapidly with decreasing height” and “wind speed decreases rapidly with decreasing height”. If the rate of change of wind speed is sufficiently great, this second condition (wind speed decreasing rapidly with decreasing height) would be a case of vertical wind shear. In the first case we would fly below the glide path and in the second case we would fly above it.
Last edited by keith williams; 9th Jun 2014 at 19:13.