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|  MIL-N-85005A(AS)
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3.4.2.1.2 Flight Conditions
(1) Aircraft "on top" Accuracy
(a) Tac Nav - The error in flying over a surface reference
and marking an "on top" position shall not exceed 100
feet (1 σ). This surface reference may be a fixed
point on the earth or a floating buoy.
(b) GEO-Nav - The error in flying over a known geographic
point and marking an "on top" position shall not
exceed 500 feet (1 σ ). The location of this geo-
graphic reference shall be known to within 0.1 minutes
in latitude and longitude.
(2) Surface Motion Accuracy
The surface motion due to wind and sea current shall be
known to within 15% of actual. The actual surface move-
ment (current or tide) shall not exceed 5 knots during
the Doppler Navigation Test.
(3) Doppler Random Bias Errors
The combined ground speed and drift angle errors of the
APN-153 Doppler shall not contribute to more than 9 yards/
minute (1 σ ) overall velocity error.
(4) TAC NAV Test Conditions
Airplane altitude 500 feet or less to minimize visual
(a)
"on top" error.
"On tops" made over a fixed ground reference to
(b)
eliminate non-constant sonobuoy drift errors caused
by variable ocean currents.
"On-Top" revisit-time not less than 8 minutes during
(c)
the bias velocity and the residual drift computation.
The TAC NAV Tests shall be conducted under conditions
(d)
where the wind is steady and not greater than 20 knots.
A (1 σ ) limit refers to a normal (Gaussian) dis-
NOTE:
tribution.
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