Honeywell MKXXII Timed Audio Inhibit Discrete, Low Altitude Mode Select Discrete, Lamp Format

Honeywell

MK XXII EGPWS Installation Manual

3.3.13.12 Timed Audio Inhibit Discrete

The Timed Audio Inhibit will cause the inhibiting of all audio messages for a period of 5 minutes or until reset. The discrete input is connected to a momentary lighted switch. When pressed the condition is latched in memory and will be reset after 5 minutes have elapsed or pressing the switch again or when landing. The switch lighting, indicating the Audio is Inhibited is driven by a discrete output described below.

Discrete

Timed Audio Inhibit

Position / Status

Momentary Toggle = Gnd Normal = Open

Connector Pin

J1-17

NOTE: Either the Timed Audio Inhibit or the Terrain Inhibit should be used depending on the aircraft operations. See discussion is section 1.

3.3.13.13 Low Altitude Mode Select Discrete

The Low Altitude Mode select is a required input and is used for cruise operation below 500 feet AGL and for operation in high density metropolitan environments such as tall buildings. When selected, the Low Altitude Mode inhibits Excessive Terrain Closure (Mode 2) warnings, retards the Terrain Clearance warnings (Mode 4), and reduces the Terrain look ahead distances and width. When selected, Low Altitude Mode may be de-selected by pressing the switch again.

The Low Altitude select switch is a lighted momentary switch where the selected condition lighting is driven by an output discrete described below.

3.3.13.14 Output Discretes

The discrete outputs are defined in Appendix E Section 7.4. The MK XXII EGPWS supports two kinds of Ground/Open discrete outputs used to indicate various conditions. Monitor outputs are used to indicate failure conditions for the EGPW system. Monitor outputs default to an active state when there is a failure or if power is removed from the EGPWS (no connection if the EGPWC is removed from the rack). The Discrete Out Lamp driver outputs are used to indicate alert modes (GPWS WARN, BELOW GS, etc.) or mode control status (Terrain Display Select, etc.) of the EGPWS.

Short-term current limit protection is provided on all drivers for output shorting conditions. Ground going output discretes may be connected together to produce a ‘wired OR’ function for the active low state of the outputs. If output discretes are ‘wire OR’d’ then diodes must be installed for isolation.

3.3.13.15 Lamp Format

The Lamp Format Type (configuration) is a function of the discrete output pin functions and defines the operation of the red and amber GPWS cockpit lamps.

CAGE CODE: 97896 SCALE: NONE SIZE: A DWG NO: 060-4314-225 REV: C SHEET 100