EFFECTIVITY AIRPLANES WITH SUNDSTRAND
CONFIG 2MARK II COMPUTERS 799 Page 5/6
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2) With flaps in the landing configuration, the warning boundary is limited as shown in Fig. 3, Sheet 3. No altitude gain is required to turn off the TERRAIN aural warning after the PULL UP aural warning is activated. The PULL UP aural warning is inhibited at radio altitude below 700 feet with landing gears down. Only the TERRAIN aural warning is activated.
3) To provide additional nuisance warning protection at the runway threshold during steeper approaches, the lower limit of mode 2B varies as a function of barometric rate as shown in Fig. 3, Sheet 3.
(c) Takeoff altitude loss warning (Mode 3) 1) A warning consisting of a visual GPWS and an aural DON'T SINK is provided when the airplane is in takeoff mode before acquiring 700-foot terrain clearance with landing gear or flaps up and a barometric altitude loss is detected as shown in Fig. 3, Sheet 3. The altitude loss required to activate the warning varies with the height of the airplane above the ground at the time of inadvertent descent occurs. At a climbout altitude of 100 feet, any loss of altitude will activate the warning. At 700 feet an altitude loss of 70 feet will activate the warning.
2) A magnetic latch provides logic between mode 3 and 4. During takeoff, the latch is set to arm the takeoff mode and disarming the terrain clearance warning. Upon acquiring 700 feet of altitude, the latch resets, arming the terrain clearance warning.
(d) Unsafe Terrain Clearance Warning (Mode 4)
1) With landing gear not down, the computer will provide a warning if the airplane is below 500 feet and speed below
0.35
mach, as shown in Fig. 3, Sheet 4. The warning is visual and aural consists of TOO LOW-GEAR repeated every
1.5
seconds. For speed above 0.35 mach, the aural warning changes to TOO LOW-TERRAIN, repeated every 1.5 seconds and the warning threshold increases lineraly to a maximum of 1000 feet above the terrain.
2) With landing gear down, the minimum warning threshold decreases to 200 feet and a TOO LOW-FLAPS warning comes on if the flaps are not in landing configuration as shown in Fig. 3, Sheet 4. A magnetic latch is used to select mode 4A or mode 4B, so that power interruption or missed approach below 500 feet prevent reactivation of mode 4A until at least 700 feet of terrain clearance is reached.
(e) Glide Slope Deviation Warning (Mode 5)
EFFECTIVITY
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1) The glide slope warning is armed when an ILS frequency is selected. The warning envelope consists of two regions as shown in the Fig. 11. The BELOW G/S indicators accompanied by a reduced volume of aural warning GLIDE SLOPE come on, if the deviation of the airplane below the glide slope exceeds 1.3 dots between 1000 and 150 feet of radio altitude. The aural warning increases to full volume if the deviations of the airplane below the glide slope exceeds 2 dots when the airplane is between 300 and 150 feet of radio altitude.
2) In order to allow the pilot to purposely descend below the glide slope without triggering a warning, the glide slope warning mode may be inhibited by pressing the PUSH TO INHIBIT switch when the radio altitude is below 1000 feet and hard warning is not in progress. The glide slope warning cannot be inhibited when the hard warning is on.
XA (6) ALL EXCEPT AF, IB, AND GN WITH 34-2171; The ground proximity warning output for all modes is inhibited whenever the stall warning system is activated. The warning outputs are also recorded through the flight recorder system.
(7) System self-test may be initiated by pressing the GROUND PROXIMITY TEST switch. During self-test, the GPWS, BELOW G/S, and GPWS INOP indicators come on, and a loud GLIDE SLOPE and WHOOP WHOOP PULL UP aural warning occurs. The PULL UP aural warning may repeat up to seven times.
B. Controls
(1)
The GROUND PROX WARN CMPTR circuit breaker on electronic circuit breaker panel P7 controls the 115-volt ac power to the computer. The ground proximity warning system operates continuously whenever the essential instrument bus is energized.
(2)
System control includes the ground proximity warning system test switch and the glide slope inhibit switch.
EFFECTIVITY
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GROUND PROXIMITY WARNING SYSTEM - TROUBLE SHOOTING
__________________________________________________
1. General
_______
A. The following trouble shooting procedures are based on performance of the system operational test and are presented in tree-type format. The test steps (heavy-line boxes) are connected by shaded arrows to show the OK condition path. When all steps in the OK condition path check out, the system is operable.
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