Cessna 182 1978 - Blowing out Lines; Pitot System Inspection and Leakage; Static Pressure System Inspection and Leakage Test

MODEL
182 & T182
SERIES
SERVICE
MANUAL
ed by the electrical system. A static
pressure alter-
NOTE
nate source
valve
may be installed
in the
static sys-
tem for use when
the external static source is mal-
If leakage rate exceeds the maximum allowable,
functioning. This valve also permits draining
first tighten all connections,
then repeat leak-
condensate from the static lines. Refer to Pilots age test. If leakage rate still exceeds the maxi-
Operating Handbook for flight operation using alter- mum allowable, use following procedure.
nate static source
pressure. The encoding
altimeter
supplies an altimeter reading to the optional 300 or i. Disconnect static pressure lines from airspeed
400 transponder for signal
transmission. The stand- indicator and
vertical speed indicator. Use suitable
by altimeter is connected to the static system by a fittings to connect lines together so altimeter is the
tube to the vertical speed
indicator. The static tube only instrument
still connected into static pressure
installation
will vary when an alternate
static source system.
is installed. j. Repeat leakage test to check whether static pres-
sure system or the bypassed
instruments are
cause of
15-12. MAINTENANCE. Proper maintenance of leakage. If instruments are at fault, they must be
pitot and static system is essential for proper opera- repaired by an "appropriately rated repair station"
tion of altimeter, vertical
speed and airspeed indi- or replaced.
If static pressure system is at fault,
cators. Leaks,
moisture and obstructions in pitot
use following procedure to locate leakage.
system will result in false airspeed indications,
k. Attach a source of positive
pressure to static
while static system malfunctions will affect readings source opening. Figure 15-4 shows one method of
of all three instruments. Under instrument flight obtaining positive pressure.
conditions,
these
instrument
errors
could be
hazar-
dous. Cleanliness
and security are the
principal
rules
for system maintenance.
The pitot tube
and
static ports MUST be kept clean
and unobstructed. Do not apply
positive pressure with airspeed
indicator or vertical
speed indicator
connect-
15-13. STATIC PRESSURE SYSTEM INSPECTION ed to static pressure system.
AND LEAKAGE TEST. The following procedure
outlines inspection and
testing of static pressure
1. Slowly
apply positive pressure
until altimeter
system, assuming
altimeter has been tested
and in- indicates
a 500-foot decrease
in altitude and main-
spected in accordance with
current Federal Aviation tain this altimeter
indication while checking for leaks.
Regulations.
Coat line connections and static source flange
with
a. Ensure static system
is free from entrapped LEAK-TEC
or a solution of mild soap and water,
moisture and
restrictions.
watching for bubbles to locate leaks.
b. Ensure no alterations
or deformations of air- m. Tighten
leaking connections. Repair or replace
frame surface
have been made which would
affect parts found defective.
the
relationship between air
pressure in static pres-
n. Reconnect
airspeed and vertical
speed indicators
sure system and
true ambient static air pressure for into
static pressure system and repeat leakage
test
any
flight configuration.
per steps "c"
thru "h".
c. Seal one static source
port with pressure
sensi-
tive tape. This seal must be air
tight. 15-14. PITOT SYSTEM
INSPECTION AND LEAKAGE
d. Close static pressure alternate source valve, TEST. To check pitot system for leaks, place a piece
if installed.
of tape over small hole
in lower aft end of pitot tube,
e. Attach
a source of suction to the remaining static
fasten a piece of rubber or plastic tubing
over pitot
pressure source opening.
Figure 15-5 shows one tube, close
opposite end of tubing and slowly roll up
method of obtaining
suction. tube
until airspeed indicator registers in cruise range.
f.
Slowly apply suction until
altimeter indicates
a Secure tube and
after a few minutes recheck
airspeed
1000-foot increase in altitude. indicator. Any leakage will have reduced the pres-
pressure
is reduced gradually.
Otherwise instru-
When applying or releasing suction,
do not ment may be damaged.
If test reveals a leak in sys-
exceed range
of vertical speed indicator or
tem, check all connections for tightness.
airspeed indicator.
15-15.
BLOWING
OUT
LINES.
Although the
pitot
g. Cut
off suction source to maintain a "closed"
system is designed to drain down to pitot
tube open-
system for one minute. Leakage shall not exceed ing, condensation may collect at other points in sys-
100 feet of altitude loss as indicated on altimeter. tem and produce a partial obstruction. To clear the
h. If leakage rate is within
tolerance, slowly re- line, disconnect
it at airspeed indicator. Using low
lease
suction source and remove tape from static
pressure air, blow from indicator end
of line toward
port. the pitot tube.
15-5