Adding an arbitary 50' to an MDA is just that - arbitary. The PANS OPS height loss margins for a pressure altimeter are as follows: Cat A 130', Cat B 142'. Cat C 150', Cat D 161'
Indeed so.
I suspect this 50 foot business was propagated by BA some years ago, and like a London fog, has crept ever so slowly into other regions.
Completing an 1179 sim session about ten years ago, the UKCAA inspector thought the 50 foot idea was the greatest thing since sliced bread, until I pointed out the PansOps data stated above.
For this, he had no ready answer.
