KLM MD-11 - Aircraft Clock; Air Data System

MD-11 Flight Crew Operations Manual
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Instrumentation and Navigation -
Description and Operation
Inst.10.8
Aircraft Clock
An electronic clock/chronograph/elapsed timer is controlled and located on the
maintenance panel. The clock provides the Universal Time Coordinated (UTC)
and date reference for the FMC and DEUs.
The ND provides UTC, elapsed flight time, and an individual count up/down
counter. The elapsed flight time starts when the aircraft transitions from
ground-to-air and stops 30 seconds after the air-to-ground transition. The elapsed
flight time is held as long as aircraft electrical power is available. The elapsed
flight time is reset when V2 is computed on the FMS TAKEOFF page for the next
flight. The elapsed time display is the default display.
The count up/down counter is started, stopped, and reset from the controls on the
lighting control panel. The count down timer value is entered on the FMS
APPROACH page. A tone will sound when counter passes through zero. The
counter display will override the elapsed counter display.
Air Data System
The air data system consists of pitot and static air lines, one Total Air Temperature
(TAT) sensor, two AOA sensors, two CADCs, and one standby altimeter/airspeed
indicator.
Baroset data is received from the glareshield control panel. Wing tip fuel quantity
data is received from the Fuel Quantity Gauging System (FQGS) for VMO
computation.
Three pitot tubes (Captain's, First Officer's and auxiliary) sense aircraft pitot
(impact) pressure and send it to the two CADCs and the standby altimeter/airspeed
indicator.
The four static ports sense the static (outside air) pressure and send it to the two
CADCs, standby altimeter/airspeed indicator and the avionics fan control pressure
switch.
The TAT sensor (one for both CADCs) sends total air temperature to the CADCs.
The AOA sensors send angle-of-attack data to the CADCs.
Wing tip fuel quantity from the FQGS is used to compute VMO/MMO.
VMO/MMO will decrease linearly as wing tip fuel quantity decreases. Wing tip
fuel quantity does not affect VMO/MMO when tip quantity is below 60% full.
The CADCs compute and output airspeed, Mach number, altitude, maximum
airspeed, vertical speed, TAT, static air temperature, AOA, True Airspeed (TAS),
and pressures (pitot, impact, and static).
Static source (position) errors and AOA effects are corrected in each CADC. TAT
is corrected for anti-ice heater effect.
November 16, 2009