.
the radio altitude increases to DH +75 feet
.
the radio altitude is equal to zero feet (i.e. during touchdown).
Note: Following an electrical power interruption, the DH value defaults to 200 feet.
Copyright . The Boeing Company. See title page for details.
10.40.4 December 1, 2000
Flight Instruments, Displays -EFIS System Description 737 Operations Manual
Mach Display
The current Mach number from the related air data computer (ADC) is displayed if the following are satisfied:
.
accelerating – Mach is equal to or greater than .40
.
decelerating – Mach previously above .40 and still greater than .38.
Ground Speed Display
A digital presentation of the current ground speed is displayed. The ground speed data is received from the FMC or the IRS, with the FMC being the primary source. The numeric range is from 0 knots to 999 knots.
True Airspeed Display (as installed)
The current true airspeed from the air data computer is displayed. The numeric range is from 101 knots to 999 knots.
Pitch Limit Symbol
The position of the pitch limit symbol is a function of the stall warning computer.
the pitch limit symbol appears any time the flaps are extended. During takeoff, the pitch limit symbol is fixed at 15 degrees pitch attitude until the stall warning computer commands a value greater than 15 degrees (at approximately 100 knots). Above this speed, the position of the pitch limit symbol is a function of the various inputs to the stall warning computer and is limited to a maximum of 30 degrees of pitch.
In general, the pitch limit symbol is programmed so that stick shaker activation will coincide with a pitch attitude equal to the pitch limit symbol indication.
In a rapid pull up, the pitch attitude may exceed the pitch limit symbol indication
for a brief period of time without initiating the stick shaker warning. On some airplanes delivered in 1989 and earlier, when light weight, the stick shaker may be activated by the low speed limit logic of the stall warning computer even though the pitch limit symbol is positioned slightly above the airplane symbol.
Speed Tape Display (as installed)
The speed tape display consists of a graduated scale which moves relative to a fixed airspeed reference pointer. On some airplanes, the pointer contains a rolling digit readout of current airspeed. Various symbols related to airplane performance are positioned on the speed tape. An explanation of the various speed tape symbols follows.
Flight Instruments, Displays -EFIS System Description 737 Operations Manual
Speed Tape Scale
A range of approximately 84 knots is displayed on the speed tape. Numbers are placed on the tape at 20 knot intervals from 40 knots to 420 knots. The speed tape scale scrolls up and down, and current airspeed is indicated by the digital readout.
Digital Readout
On some airplanes, a digital readout of the current calibrated airspeed is located within the fixed airspeed reference pointer. The units digit “rolls” continuously based on the current fractional unit value of the calibrated airspeed to emulate the rolling digit readout of a conventional electrical/mechanical airspeed indicator.
Airspeed Trend Arrow
A green arrow of variable length which points to the predicted airspeed that the airplane will achieve within the next 10 seconds. This prediction is based on the present airspeed and airspeed acceleration. Than airspeed trend arrow is not displayed unless its magnitude is greater than 4 knots. The airspeed trend arrow is removed when its magnitude becomes less than 3 knots.
Command Speed
The command speed is displayed as a magenta, double–line cursor located on the speed tape scale if the command speed is within the currently displayed speed tape range. It is displayed in a numerical form, above or below the speed tape scale, if the command speed is not within the currently displayed speed tape range. The indicated command speed is equivalent to the selected speed on the MCP or to the FMC command speed, whichever is applicable.
Maximum Operating Speed (VMO/MMO or Gear/Flap Placards)
The maximum operating speed is represented by the high speed red and black barber pole. The position of the maximum operating speed symbol is a function of data supplied to the symbol generator from the stall warning computer. The maximum operating speed is the lower of the gear–extended placard speed, the flaps–extended placard speed, or VMO/MMO.
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