(4)
The measured resistance at a given ambient temperature should read as indicated on the temperature. Resistance graph taking into account the tolerance of the ohmmeter (Fig. 501).
(5)
Measure the resistance from either pin 3 or 4 and 2 or 5 to the temperature probe case. This resistance should be greater than 10 megohms.
(6)
Check the heater element by measuring the resistance between pins 1 and 6. The resistance should be approximately 20 ohms at ambient temperature between 60 and 90°F. It should be somewhat less at low ambient temperatures and somewhat higher at high ambient temperature.
(7)
Measure the resistance from either pin 1 or 6 to the temperature probe case. This resistance should be greater than 5 megohms.
(8)
Replace electrical connector on temperature probe.
H31418
543 Temperature - Resistance Graph
Aug 15/73 Figure 501 34-14-21
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
TOTAL AIR TEMPERATURE PROBE - CLEANING/PAINTING
1. Total Air Temperature Probe Cleaning
A. Equipment and Materials
(1)
Compressed air source
(2)
Syringe and water or dry cleaning solvent
B. Cleaning Total Air Temperature Probe
CAUTION: CARE MUST BE USED IN REMOVING FOREIGN MATERIAL THAT MAY BE LODGED WITHIN THE AIR INLET SCOOP TO PREVENT DAMAGE TO THE SENSING ELEMENT.
(1)
To remove foreign material, blow compressed air in a reverse direction through the air exit hole.
(2)
If this method fails, use a syringe and flush the interior of the air inlet scoop with water or a dry cleaning solvent. If foreign particles still exist, it may be necessary to remove the temperature probe from the airplane for additional cleaning.
(3)
With the temperature probe removed from the airplane, soak the air inlet scoop and strut with water or a dry cleaning solvent.
(4)
Move the probe back and forth in the liquid, completely flushing interior of the scoop and strut.
(5)
When the foreign material has become dislodged, blow compressed air through the scoop in a reverse direction.
(6)
After cleaning and before installation, perform test as indicated in Total Air Temperature Probe - Adjustment/Test.
500
May 15/67 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 34-14-21 Page 701
MACH AIRSPEED WARNING SYSTEM - DESCRIPTION AND OPERATION
EFFECTIVITY
GJ ALL EXCEPT B-2509 thru B-2510 and B-2524
1. General
A. The mach airspeed warning system is provided to alert the flight crew when the airplane approaches a critical speed. The warning is accomplished by a pitot static operated switch and an aural warning (Fig. 1 and 2). A push-to-test switch is provided on the overhead panel (P5) to check operation of the warning circuit.
2. Mach Airspeed Warning Switch
A. The switch assembly, under conditions of high mach airspeed will trigger an electronic clacker located in the aural warning devices unit, providing an aural warning signal. The clacker will sound any time the indicated airspeed exceeds the maximum operating airspeed or mach number.
B. The warning switch bellows is controlled by pitot and static pressure inputs and is mechanically connected to a set of contacts. When a predetermined airspeed or mach number is exceeded, the contacts open and 28 volts dc is removed from the switch relay. With the relay de-energized, a ground is applied to the clackers in the aural warning and call devices box. The clackers will remain energized until the airplane airspeed or mach number is reduced.
3. Mach Airspeed Aural Warning Clackers
A. The aural warning and call devices box on the control stand has two aural clackers. Upon initiation by the mach airspeed warning switch, the clackers provide a distinct warning signal which cannot be mistaken for the aural warnings associated with or activated by other systems (Ref Chapter 31-26-0, Aural Warning System).
Feb 20/89 34-15-0 Page 1
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
K39142 H23989
Mach/Airspeed Warning System Component Location 557
34-15-0 Figure 1 May 01/76
Page 2
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
500 Mach/Airspeed Warning System Circuit
Feb 15/68 Figure 2 34-15-0
Page 3
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
