DHC-6 -400 Twin Otter aircraft
CH 34
Navigation
DHC-6 -400 Twin Otter aircraft
The navigation information required for aircraft operations is
provided by the following systems-
flight environmental data,
attitude and direction,
landing and taxiing aids
independent position determining.
DHC-6 -400 Twin Otter aircraft
The standard (Basic) aircraft is equipped with the following
Avionics which are suitable for day VFR certification
DHC-6 -400 Twin Otter aircraft
The IFR Operational Bundle equips the aircraft for day or night VFR or
IFR certification.
DHC-6 -400 Twin Otter aircraft
FORWARD AVIONICS SHELF AFT AVIONICS SHELF
DHC-6 -400 Twin Otter aircraft
The Public Commercial Operations
DHC-6 -400 Twin Otter aircraft
For Additional Equipment
DHC-6 -400 Twin Otter aircraft
Antennas
The VOR antenna installed on each side of the vertical stabilizer and is the half
loop type, VOR antenna.
1) The GS (Glide Slope) antenna, is located on the nose bulkhead behind the
nose cap.
2) The MB (Marker Beacon) antenna is located on the underside of the
fuselage.
3) The ADF antennas, No. 1 and No. 2 are installed in the cabin roof, in line
with each other.
4) The weather radar antenna is part of the Honeywell ART 2000 radar
receiver/transmitter located in the nose radome.
5) The DME antennasare installed on the underside of the rear fuselage.
6) The Transponder antennas
DHC-6 -400 Twin Otter aircraft
DHC-6 -400 Twin Otter aircraft
DHC-6 -400 Twin Otter aircraft
DHC-6 -400 Twin Otter aircraft
Pitot-Static System
The pitot-static system provides the air pressure input
for the Air Data, Attitude and Heading Reference
Systems (ADAHRS 1 and ADAHRS 2), and to the
Electronic Standby Instrument System (ESIS).
Pitot Heads
There are two electrically heated pitot heads,
installed on a mast projecting from the LH and RH
sides of A/C nose.
The LH pitot head supplies air pressure to the Air Data,
Attitude and Heading Reference Systems, ADAHRS 1,
The RH pitot head supplies air pressure to the Air Data,
Attitude and Heading Reference Systems, ADAHRS 2
and to the Electronic Standby Instrument Systems,
(ESIS).
DHC-6 -400 Twin Otter aircraft
ESIS) Static Source Valve
The (ESIS) STATIC SOURCE valve is
located on the dash panel, directly
above the avionics circuit breakers.
The valve can be selected to the
NORMAL or ALTERNATE static source
position.
With the valve selected to the NORMAL
position, the ESIS static lines will be
connected to the upper static vents.
With the valve selector in the
ALTERNATE position, the ESIS static
lines will be connected to the lower static
vents.
DHC-6 -400 Twin Otter aircraft
Attitude and Direction Indication
The attitude and direction system is comprised of the standby magnetic compass,
the Electronic Standby Instrument System (ESIS), the Air Data, Attitude and
Heading Reference Systems (ADAHRS 1 and ADAHRS 2) and is displayed
through the Primary Flight Display (PFD) and the Multi-Function Displays (MFD’s).
Standby Magnetic Compass
The standby magnetic compass gives the aircraft magnetic heading.
Electronic Standby Instrument System (ESIS)
The Electronic Standby Instrument System (ESIS) gives displays for attitude,
heading, altitude and airspeed in case of primary display or systems failures. The
ESIS is powered by its own dedicated PS–850 backup battery, and is entirely
independent of the Apex system.
DHC-6 -400 Twin Otter aircraft
Attitude and Direction Indication
Air Data, Attitude and Heading Reference
System (ADAHRS) (KSG 7200)
The aircraft is equipped with a dual channel
KSG 7200 Air Data, Attitude and Heading
Reference System (ADAHRS). The system
provides primary attitude, heading and air data
parameters from each channel to the Modular
Avionics Unit (MAU).
DHC-6 -400 Twin Otter aircraft
Marker Beacon
The Marker Beacon (MKR) uses visual and audio indicators to
alert the crew for when the aircraft passes over a 75 MHz
transmitter.
The Marker Beacon receiver is contained in the audio control
panel.
Description
Marker Beacon send signal to the MAU for display on the PFD.
Outer Marker- 400-Hertz ‘dash’ tone. two tones per second.
Middle Marker -1300-Hertz tone. short ‘dot' and long ‘dash'
bursts at 95 combinations/minute.
Inner Marker - 3000-Hertz ‘dot’ tone. Tone of six times / second.
DHC-6 -400 Twin Otter aircraft
Marker Beacon
Audio can be heard by selecting the “MKR” push-button switch.
Volume level, adjustment located on the unit.
MKR Antenna - on the bottom of the fuselage, right of the center line,
between station 73.00 and 86.00.
DHC-6 -400 Twin Otter aircraft
Independent Position Determining
The independent position determining system has the
following sub-systems:
Stormscope System
Weather Radar System
Radar Altimeter System
Traffic Alert and Collision Avoidance Systems (TCAS)
Enhanced Ground Proximity Warning System (TAWS)
DHC-6 -400 Twin Otter aircraft
Stormscope
A passive sensor as antenna receive signal to detect the bearing and
range of EM lightning.
System maps EM signals (lightning) 360 degrees around the a/c to a
max radius of 200 nautical miles.
HSI display info from the Lightning Sensor Sys in partial compass
format
Lightning display has two components:
mode/fault annunciations/Strike Rate and lightning cell strike data.
Mode/fault and Strike Rate annunciations - outside of the HSI Display
area while lightning strike signals - inside the HSI.
DHC-6 -400 Twin Otter aircraft
LX CLR in the HSI overlay clears all strike signals.
Stormscope consists of a RXR (rear avionics rack) and a top mounted
ANT at STA 400.
A RXR inhibit line is interfaced to the ACP ensures erroneous strike
signals are not displayed when a TXR is keyed.
The WX–500 as three levels of self-test.
Power-on self-test, continuous self-test and pilot initiated self-test.
Results are by System Status messages and Faults Code messages.
During pilot initiated self-test time data is not updated.
The Stormscope interfaces: MAU & ACP
DHC-6 -400 Twin Otter aircraft
Weather Radar System
The RDR 2000 WXR radar (Radio Detecting and Ranging) system gives
the pilot a selectable horizontal display of thunderstorms or high density
precipitation in front of the a/c.
When a pulse intercepts a target, the energy is reflected as an echo, or
return signal, back to the antenna.
From the antenna, the returned signals are transferred to the
receiver/transmitter unit.
The returned signals, are then displayed.
DHC-6 -400 Twin Otter aircraft
Weather Radar System
Ground mapping (GMAP)
In GMAP mode, prominent landmarks are
displayed which enable the pilot to identify
coastlines, hilly or mountainous regions,
cities, or even large structures.
RT Unit has 4kW TXR, config module, a
RXR, and an integral processing unit, in
nose radome.
The pitch and roll signals from the ADAHRS
via ARINC 429 and processes this data to
stabilize the 12 inch flat panel radar ant.
DHC-6 -400 Twin Otter aircraft
Weather Radar System
The sensor unit xmts a beam of pulsed microwave energy.
When a pulse reaches visible moisture, the energy is reflected back to ant.
The return signals are processed and sent to the MAU.
The air/ground system automatically switches to STANDBY mode when the
aircraft is on the ground.
The config module stores the config and cal data for the RDR 2000 system.
DHC-6 -400 Twin Otter aircraft
The ant pedestal elv assy permits the radar
beam to be tilted up or down 15 degrees.
Tilt may be controlled manually on the multi-
function controller or may be determined
automatically.
In the case of auto tilt, the manual tilt control
provides a trim capability around the auto set
position.
Stab capability of up to 30 degrees in pitch and
roll is possible.
Combined ant stab plus tilt angle is functional
over a range of ±30 degrees.
DHC-6 -400 Twin Otter aircraft
Weather radar displayed on as overlays on:
PFDs and MFD
on the side of the HSI display
Pressing the OVRLY soft key displays the overlay selection
menu. Selecting WX RDR will enable the weather radar
overlay to be displayed on the HSI.
There is also an OFF section to remove the overlay.
Wxr Radar controls are located on the MF Controller.
A WX RADAR dual concentric knob - a push select function is
used to control the mode and the tilt, gain settings.
The outer control is a four position rotary knob with the
position OFF/STBY/TEST/WX.
The inner control is rotary click control knob and is pressed to
modify the tilt or gain setting.
DHC-6 -400 Twin Otter aircraft
Weather radar information displayed on as overlays on
PFDs and the navigation map display of the MFD
The PFD weather radar overlay can be assessed by
pressing the soft key on the side of the HSI display
The soft key identifier OVRLY then appears in white.
Pressing the OVRLY soft key displays the overlay
selection menu. Selecting WX RDR will enable the
weather radar overlay to be displayed on the HSI.
There is also an OFF section to remove the overlay.
The controls for the weather radar are located on the MF
Controller.
A WX RADAR dual concentric knob control with a push
select function is used to control the mode and the tilt,
gain settings.
The outer control is a four position rotary knob with the
position OFF/STBY/TEST/WX.
The inner control is rotary click control knob and is
pressed to modify the tilt or gain setting.
DHC-6 -400 Twin Otter aircraft
The azimuth motor drives the ant up to 50 deg left and right for a total max
scan angle of 100 deg, although in practice a 90 deg image is scanned.
The scan rate is 25 degrees per second, providing 16.7 “looks per minute”.
The system displays storm intensity levels in colour against a black
background.
Rainfall intensity is presented in four colours: green, yellow, red, and magenta,
with magenta representing rainfall of the highest intensity.
GMAP mode uses green, yellow and magenta colours to display the different
reflectivity
Separate sensitivity timing control (STC) compensation is used for weather
and GMAP modes.
