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I marked them with white circles. What are they for? enter image description here

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    $\begingroup$ You are basically asking about the entire PFD (which seems to be from a 737NG). Have you tried googling/reading official docs from Boeing? you could have at least numbered the different items to make answering easier $\endgroup$
    – DeepSpace
    Feb 5 '20 at 11:59
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    $\begingroup$ Downvoters, please explain why you downvote. If you cannot find a way of improving this question, this will at least give clue to the OP for how to ask its next question. $\endgroup$
    – Manu H
    Feb 5 '20 at 12:25
  • $\begingroup$ I upvoted this question as it comes back to basics which is a good entry point for new comers. $\endgroup$
    – Manu H
    Feb 5 '20 at 12:27
  • $\begingroup$ @Mohammad Gohardoust - To further you’re interest in aviation, I would highly recommend becoming familiar with the standard steam gauge six-pack. Every airplane will have their own version of these instruments. If you add to that autopilot and VOR/ILS Course Deviation Indicators, you will be able to decipher most of the front panel of even the most sophisticated aircraft. Most of them have their PFDs set up in very similar fashions. A Garmin G1000 w/ GFC700 is a good example of a generic PFD for beginners. $\endgroup$
    – Dean F.
    Feb 5 '20 at 13:21
  • $\begingroup$ thank you very much $\endgroup$ Feb 5 '20 at 13:23
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  • .78:

    This is the target speed or Mach number, meaning the aircraft should travel at $ 0.78 \times c $ (speed of sound). The current Mach number is 0.779 (shown in white at the bottom of the speed tape).

    Selected Speed (magenta)

    Displays target airspeed:

    • indicates the airspeed manually selected in the IAS/MACH window
    • indicates the FMC computed airspeed when the IAS/MACH window is blank.
  • ARM LNAV VNAV SPD:

    This is the Flight Mode Annunciatior (FMA), indicating that the autothrottles are armed (ARM), the roll mode is Lateral Navigation (LNAV) and the pitch mode is vertical navigation speed (VNAV SPD).

    FMA

    1 Autothrottle (A/T) Engaged Mode

    2 Roll Engaged Mode

    4 Pitch Engaged Mode

  • Red band:

    This is the so called Barber's pole indicating the indicated airspeed range that is above the current maximum speed.

    Maximum Speed (red and black)

    Bottom of the bar indicates the maximum speed as limited by the lowest of the following:

    • Vmo/Mmo
    • landing gear placard speed
    • flap placard speed.
  • CMD:

    This is indicating that one of the autopilots is currently engaged in command mode (CMD). The 737 also has a different autopilot mode called control wheel steering (CWS).

    7 Autopilot Status

    (see previous image above)

  • 254:

    This is the current calibrated airspeed in knots. The magenta marker is the current target speed for the autothrottle / VNAV descent.

    Current Airspeed (white)

    Indicates current calibrated airspeed in knots. When current airspeed decreases into the minimum maneuver speed amber bar:

    • airspeed readout box turns amber and flashes for 10 seconds.
    • box returns to white when airspeed is above minimum maneuver speed.

    Speed Bug (magenta)

    Points to the airspeed:

    • manually selected in the IAS/MACH window
    • indicates the FMC computed airspeed when the IAS/MACH window is blank.

    When the selected speed is off scale, the bug is parked at the top or bottom of the tape, with only one half bug visible.

  • 36620:

    This is the current altitude in feet as measured by the static ports. This is not necessarily the actual altitude above sea level because the reference pressure for the altimeter is set to STD (see below).

    Current Altitude

    Displays current altitude in increments of thousands, hundreds and twenty feet:

    • for positive values of altitude below 10,000 feet, a green crosshatch symbol is displayed
    • a negative sign appears when altitude below zero feet is displayed
    • readout box becomes bold to denote altitude acquisition
    • readout box is highlighted in amber and flashes to denote altitude deviation (refer to Chapter 4, Automatic Flight and Chapter 15, Warning Systems).

To the right of this (not circled in the picture, but worth mentioning) is a scale with a white needle pointing between numbers 2 and 6 on the scale:

This is the vertical speed indicator or VSI. It indicates the direction and rate of the planes vertical movement. The numbers on the scale indicate thousands of feet / second, and since the needle is pointing downwards, the plane is currently descending. Below the scale is numerical display giving the exact rate of descend or climb. In this case, the plane is descending at 2800 feet/minute

  • REF 30/128:

    This is the reference flaps and speed for landing. The pilots have already selected that they want to land with flaps 30 and at a reference speed of 128 knots in the CDU.

    Speed Reference Display (green)

    Displayed if the airspeed and/or weight is entered via the speed reference selector on the engine display control panel:

    • on the ground, V1, VR, and takeoff gross weight may be selected; if VREF is selected, INVALID ENTRY is displayed
    • in flight, VREF and landing gross weight may be selected; if V1 or VR is selected, INVALID ENTRY is displayed
    • removed when the speed reference selector is moved to the SET position.
  • STD 30.21 IN.:

    This is the current and pre-selected altimeter reference pressure. STD means that the current reference pressure is 1013 hPa (29.92 inHg), which is the standard value selected above the transition altitude. The pilots have already pre-selected a value of 30.21 inHg, which will be activated when descending below (or being cleared below) the transition level.

    Barometric Settings (green)

    Indicates the barometric setting in either inches of mercury (IN) or hectopascals (HPA) as selected on the EFIS control panel. Display is boxed amber if numeric is set and airplane is climbing above transition altitude, or if STD is set and descending below transition flight level.

    Preselected Barometric Setting (white)

    STD is displayed when the Barometric Standard (STD) switch is selected on the EFIS control panel. When STD is displayed, a barometric setting can be preselected on the EFIS control panel barometric selector and is displayed in small white characters below STD.

  • Circle at bottom:

    This is the current heading indicator. It is showing that the aircraft's nose is pointing towards 260 degrees as measured from magnetic North (see the green MAG text), but is actually moving across the ground (track) at 256 degrees (white line). The current selected heading on the MCP (mode control panel) is shown by the magenta marker and text (also 260 here).

    Heading and Track

    1 Current Heading Pointer (white)

    Indicates current heading.

    2 Track Pointer (white)

    Indicates current track.

    3 Selected Heading (magenta)

    Digital display of the selected heading bug.

    4 Selected Heading Bug (magenta)

    Indicates the heading selected on the mode control panel. If the selected heading exceeds the display range, the bug parks on the side of the compass rose in the direction of the shorter turn to the heading.

    5 Magnetic/True Heading Annunciation (green)

    Displays selected heading reference:

    • MAG indicates display is oriented relative to magnetic north
    • TRU indicates display is oriented relative to true north; a white box is displayed continuously around TRU

all images and quotes: Boeing 737 NG FCOMv2 (4.10 Automatic Flight - Controls and Indicators, 10.10 Flight Instruments, Displays - Controls and Indicators)

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  • $\begingroup$ very useful Thank you very much $\endgroup$ Feb 5 '20 at 12:30
  • $\begingroup$ @Sami I always used $c$ for speed of sound, too. Wikipedia seems to do the same. $\endgroup$
    – Bianfable
    Feb 5 '20 at 15:14
  • $\begingroup$ I took the liberty of adding a description of VSI even though it was not actually asked about... $\endgroup$
    – Jpe61
    Feb 5 '20 at 16:47
  • $\begingroup$ thank you so much $\endgroup$ Feb 5 '20 at 17:51

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