E. Test Pitot-Static Probe
(1)
Use pneumatic test unit and pitot control valve to apply pressure
4.53 (| 0.16) inches of mercury above ambient or 300 (| 5) knots to pitot system as indicated on pitot system test gage.
(2)
When system has stabilized, close pitot cutoff valve. Read and record value being indicated by the captain's airspeed indicator or pitot system test gage.
(3)
After 1 minute, read and record value. The pressure must not have decreased by more than 0.16 inches of mercury or 5 knots.
(4)
Operate pneumatic test unit and static control valve to apply a vacuum equivalent to 11.10 (| 0.10) inches of mercury (absolute pressure) or 25,000 (| 200) feet of altitude to the static systems as indicated on static system test gages.
(5)
When required vacuum has been reached and has stabilized in static systems; close all cutoff valves.
CAUTION: TO PREVENT INSTRUMENT/EQUIPMENT DAMAGE, VACUUM MUST BE
_______ HELD AS A BACKUP BEHIND CUTOFF VALVES DURING CUTOFF PERIOD. FOLLOWING THIS, CUTOFF VALVES ARE REOPENED. RELEASE OF VACUUM IS GRADUAL AND SIMULTANEOUS FOR ALL PITOT AND STATIC SYSTEMS.
(6) After 1 minute, read and record values. The vacuum must not have decreased by more than 0.20 inches of mercury or an equivalent fall of 400 feet in indicated altitude.
(7) Return pitot and static systems to ambient pressure. (8) Remove test adapter and seals on pitot-static probes.
WARNING: FAILURE TO REMOVE VINYL ADHESIVE TAPE FROM STATIC PORTS
_______
BEFORE FLIGHT MAY CAUSE LARGE ERRORS IN AIRSPEED SENSING AND ALTITUDE SENSING SIGNALS, WHICH MAY LEAD TO LOSS OF SAFE FLIGHT.
CAUTION:_______TO PREVENT PITOT-STATIC PROBE DAMAGE VISUALLY CHECK EACH PROBE AND VERIFY THAT NO PIECES OF COLORED TAPE REMAIN ON PROBES.
(9)
Reconnect pitot and static hoses if disconnected.
(10)
Reinstall flight recorder magazine (if removed) (Ref 31-31-01).
(11)
Test probe heater circuit of installed pitot-static probe (Ref 30-31-00).
(12)
Close TE FLAP LOAD RELIEF circuit breaker on P12 panel.
EFFECTIVITY
ALL 19.1 Page 504 Oct 25/9834-11-01
PITOT-STATIC PROBE - INSPECTION/CHECK
_____________________________________
1. General
_______
A. The inspection check visually inspects the pitot-static probe for physical damage to the strut, head and precision-contoured surfaces and for foreign material in the static ports, drain hole and pitot opening. The pitot-static probe should be replaced if it fails any of the visual inspections (Ref 34-11-01, Pitot-Static Probe - R/I).
B. Fly Back Limits
(1)
Replace the pitot-static probe for one or more of the conditions that follow:
(a)
The flight crew finds a cross-panel airspeed or altitude difference.
(b)
The pitot-static probe is out of tolerance.
(c)
There is mechanical damage.
(2)
Do these steps when you see deterioration of the pitot-static probe:
(a) You can dispatch the airplane from a base without maintenance facilities until one of the conditions that follow occur: 1) 48 hours elapse. 2) The airplane gets to a miantenance base.
2. Equipment and Materials
_______________________
A. Standard Tools and equipment
(1) Gages or Wires - 0.004 to 0.035 inch, OR
Optical Micrometer - Model 966A1
Monicle Industries, Inc.
P.O. Box 2426 Coppell, TX 75019, OR other suitable instrument
3. Inspect Pitot-Static Probe
__________________________
A. General Probe Condition
(1)
Remove the pitot-static probe (Ref 34-11-01, Pitot-Static Probe - R/I).
(2)
Visually inspect the pitot-static probe for physical damage to its precision-contoured surfaces and for foreign material in the static ports, drain hole and pitot opening. To remove the foreign material, refer to 34-11-01, Pitot-Static Probe - Cleaning/Painting.
(3)
Check for any detectable bending or twisting of the head or strut sections of the pitot-static probe.
B. Aerodynamic Contour Condition
(1)
Check the static pressure ports to make sure their edges are perpendicular to the probe's machined contour surface. Rounded or raised static port edges should not exceed 0.003 inch (Fig. 601).
(2)
Check for scratches, nicks or surface irregularities located within 0.5 inch of the static ports, and deeper than 0.015 inch.
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