galaxy flyer,
Hi. "
Why do airlines stick with QNH in QFE regions?"
Good question. In our case, the FMC can be operated in QFE mode (selectable), but after doing so VNAV becomes unuseable. Company policy is to make full use of LNAV and VNAV. (That doesn't imply that I agree with it!).
Operations of a QNH/Altitude in Feet/Subscale in hPa aircraft to regions where these three criteria do not apply is really a "no brainer". It's really no big deal so long as you stay on the ball.
Having said all that, it is my strong personal conviction that a great many CFIT tragedies occur due to altimetry errors of one sort or another. Consider the following differences between altimetry systems in various countries -
(1) Altimeter sub-scale in Inches of Mercury or Hectopascals,
(2) Altimetry measured in feet or metres,
(3) Variable Transition Altitudes and Transition Levels,
(4) Altitudes referenced to QFE and/or QNH, with possible mixing traffic.
I'm sure that there's more than this, but these immediately come to mind.
If a demented person wished to create havoc with air operations, leading to a steep rise in the possibility of CFIT, I doubt that they could do better than to introduce these conflicting systems.
I have no particular prejudice, I learned to fly in QFE operations, but went to work in a QNH environment. All of the systems have their good and bad points, but FOR HEAVEN's SAKE, let's have
ONE system. I don't care which one it is, as long as it's ONE system.
I concede that for reasons of the highest terrain in a particular region, variation in Transition Altitudes and Levels would be necessary (It would be awkward to apply the Tibetan terrain constraints, for example, to the U.K.).
There are thousands of regulatory differences between various jurisdictions, the odds are that, apart from Altimetry, they probably won't hurt you if mis-handled. A pilot under pressure at night and/or bad weather flying an aircraft primarily equipped for one system, but flying into an "alien" altimetry system, is on a count-down to a CFIT. The Swiss Cheese holes are lining up.
Regards,
Old Smokey