From the 767 Maint Manual (747 similar)
If the pilot determines the airplane had a hard landing, a
structural inspection is necessary.
(1) For landing at or below the maximum design landing weight on
airplanes with flight data recording systems capable of at
least eight (8) samples per second, the following can be used:
An indication of a hard landing on the main landing gear is a
peak recorded vertical acceleration that exceeds 1.8 G
(incremental 0.8 G). This vertical accelerometer data must be
measured by the flight data recorder accelerometer at a data
sampling rate of at least eight (8) samples per second. This
vertical acceleration G-level threshold is valid for a
conventional landing with impact with no more than two (2)
degrees of airplane roll, main landing gear touchdown first and
normal rotation onto the nose gear.For a hard landing that is a
hard nose landing or is accompanied by more than two (2) degrees
of roll at the time of main landing gear impact, the recorded peak
acceleration can be significantly less than 1.8 G, but a hard landing
inspection may still be necessary.
(2) For landing at or below the maximum design landing weight on
airplanes with flight data recording systems capable of at
least sixteen (16) samples per second, the following can be
used:
An indication of a hard landing on the main landing gear
is a peak recorded vertical acceleration that exceeds 1.9 G
(incremental 0.9 G). This vertical accelerometer data must be
measured by the flight data recorder accelerometer at a data
sampling rate of at least sixteen (16) samples per second.
This vertical acceleration G-level threshold is valid for a
conventional landing with impact with no more than two (2)
degrees of airplane roll, main landing gear touchdown first and
normal rotation onto the nose gear. For a hard landing that is
a hard nose landing or is accompanied by more than two (2)
degrees of roll at the time of main landing gear impact, the
recorded peak acceleration can be significantly less than 1.9
G, but a hard landing inspection may still be necessary.
The key words in the Manual are the first ones "If the Pilot determines the airplane had a hard landing, a structural inspection is necessary" So we work on the basis of, if it's written in the tech log as a hard landing we do the inspection. As a matter of course we pull and analyse the data recorders to get the g-level but if it happens to be below the guide line limit in the book we certainly don't cancel the inspection. Let's face it, tech crew generally aren't in a rush to write up in the log that they've had a hard landing - so when they do make that entry it's generally a real event.
World of Tweed has kindly backed me up,
However, whilst one cannot assume that we pilots are able to judge the subtleties of G on landing we DO generally know when "we've crunched her in" or "stroked her on".
At my airline, we take your word over the data stream(too unreliable and too many variables)