How FEer explain feeling of weightlessness in a UAing earth?
You'll have to elaborate on what you mean. In general I would guess they would explain it in pretty much the same way it's explained on the globe Earth. Remember, for *most* things UA is indistinguishable from a gravitational field.
Specifically: General relativity says that a UNIFORM acceleration is indistinguishable (by any means) from a UNIFORM gravitational field.
So any flaws in UA must be due to NON-UNIFORMITY.
Hence:
* UA's uniform acceleration cannot reproduce the changes in gravity at equator and poles.
* It cannot reproduce tidal effects.
* It cannot reproduce changes in gravity due to altitude.
All three of those things depend on the fact that gravity can only be considered uniform over small distances - gravity decreases as the square of the distance from the source - UA does not.
Hence UA can be disproved - but
only by examining large scale artifacts.
Most of the FE'ers actually do believe in gravity (of a sort) - claiming that the stars and the moon have a gravitational pull in order to explain changes in gravity with altitude and (they claim) to explain tides.
Sadly:
1) the explanation for tides predicts just one high tide per day - and we really get TWO.
2) the explanation for the variation of gravity with altitude would not follow the inverse square law.
The second point requires a little explanation:
In RET - gravity is proportional to 1/d
2 (d being distance between object and center of earth) - which is 1/(R+h)
2 - with R being the radius of the earth and h being your height above mean-sea-level.
In FET - if the stars are pulling us upwards with UA producing fake gravity DOWNWARDS - then the equation would be UAg-1/(S-h)
2 (where UAg is the acceleration due to UA, S is the altitude of the stars and h is your height above mean-sea-level.
The difference between these equations produces a different gravity-versus-altitude curve for RET and FET - which could be demonstrated by someone with an accurate weighing machine and a sufficiently smooth-flying airplane that wouldn't vibrate the experiment too much...maybe a high altitude balloon.
All you'd need would be a handful of data points - the two curves are very different.
* In RET, the reduction in gravity per thousand feet of altitude should get less and less with altitude.
* In FET, the reduction in gravity per thousand feet should increase with altitude.
This would be an interesting experiment - it would comprehensively disprove (or not) the UA theory.