Probes are generally used for static pressure, total pressure and
direction measurement in supersonic streams. The straight heads are
usually mounted in a special holder.
As pitch and yaw measuring probes, they can be mounted in a holder
with angular adjustment in two directions and the angles determined
by balancing the pressures measured at opposite sets of holes. The
angles can also be determined up to about 16¡Æ with the probe in a
fixed position by reading the pressures and calculating pitch and
yaw angle from the readings. Where the air stream has a pitch or yaw
angle of less than 10¡Æ the average pressure of the four holes corresponds
closely to static pressure of the same cone at zero angle of attack.
The static pressure measured on the surface of the cone can be corrected
to true stream static theoretically, following curves of the general
shape shown in Fig. 1. Total pressure of Types B and D can also be
corrected theoretically to give free stream values so the probe is
useful as a supersonic velocity probe. The total pressure holes in
Type B and D give a blunt tip to the cone, which will affect the static
readings if the ratio m/n (Fig. 2) is less than 25. This limits the
minimum size of probe of this type which can be used with purely theoretical
corrections since the minimum size of blunt tip is approximately .025".
However, a smaller m/n ratio can be used if the probe is calibrated
against some other standard. Types A and C probes are more convenient
for static pressure measurements in the smallest sizes.
National Advisory Committee for Aeronautics, Technical Note 2190,
describes tests made on conical tip probes and gives references for
the calculations necessary to correct the readings to stream static
and total. Other NACA reports TN 1428, 2579 and 3213 give further
information on the use of conical probes.
||4 hole tip for static
pressure only, straight stem.
|| 4 hole tip for
static pressure only with 90¡Æ bend.
||5 hole tip total
and static pressure, straight stem.
||5 hole tip for total
and static pressure with 90¡Æ bend.
|HOW TO ORDER :
||Ordering Part No. (e.g. SAC-12-6-15¡Æ-.315) covers exact