B4- 36 
RELEASE AND RECORDER RECORD 
Continue use of the baroswitch trace for pressure evaluation 
until the difference of this pressure value andthe hypsometer 
is 0 mb. If, however, no point canbe found where the difference 
is 0, prior to the point where the baroswitch trace indicates 
15 mbs, use the point of least difference provided the 
difference is 3 mb or less. If the closest point of difference 
is greater than 3 mb, continue using the baroswitch traces for 
the remainder of the sounding. 
When the above conditions are met, the hypsometer trace will 
be used to evaluate pressure data for the remainder of the 
flight except when the hypsometer fails (see J B4-7.12). 
13.2 The Crossover Point. In order to minimize any pressure differ- 
ence, and to facilitate the placement of levels in the crossover area, 
accomplish the crossover as follows: 
a. 
t= i1S(5Q) 
Select the first point on the recorder record where the pres- 
sure difference between the calibration charts is the smallest 
(see §B4-13.1). Draw a short horizontal line through the hyp- 
someter curve at this point and label it point ''A"'. 
Multiply the pressure difference by two (2). The resulting 
numerical value is the number of minutes below point '"'A" at 
which the crossover point is to be placed. At this point draw a 
short horizontal line through the hypsometer curve and enter 
"HYP USED". If no significant levels are tobe placed between 
point "A" and "HYP USED", omit steps (c), (d), and (e) below. 
Read the pressure from the aneroid calibration chart corres- 
ponding to the contact value at the point where "HYP USED" 
was entered. Find the hypsometer ordinate value correspond- 
ing to this pressure value from the hypsometer calibration 
chart. 
Plot this hypsometer ordinate value on the hypsometer cross- 
over line and label this point ''B". Connect points "A" and "B" 
with a straight line. 
Compute and use hypsometer pressure for all significant 
levels falling between points ''A" and ''B", using line ''A-B" 
as the hypsometer pressure curve. 
FMH#3 
