Complex sentence: This bank angle should be included in the legend of the climb performance chart-one engine operating, because not maintaining this bank angle renders the presented performance data invalid; the airplane might not even be able to maintain altitude if the bank angle is not maintained.
Split into simpler sentences: This bank angle should be included in the legend of the climb performance chart-one engine operating. The note is included, because not maintaining this bank angle renders the presented performance data invalid; the airplane might not even be able to maintain altitude if the bank angle is not maintained.