Maybe I should go back to my books...in any case the difference wont be larger than 80 ft...so if in extreme cold weather you dont go below DH,youll be alright..maybe time time to use the rad alt??
Arrrgh! This statement makes a lot of presumptions that are not supported by the design of an ILS procedure. You have no way of knowing where the controlling obstacle is located and this is a serious flaw in your suggestion.
If the controlling obstacle is in the final approach segment, you will only clear it by the height loss margin! The further away from the landing THR that this obstacle is located, the larger your TEC will be and, therefore, the less clearance you're likely to have.
The situation is much worse if the obstacle is in the precision missed approach segment because, while you still won't know where the obstacle is, you may only just barely clear it, in the event of a missed approach. Thus, an error of even 80 feet, as you put it, could ruin your day if you have to go missed approach.
