|WLV : WING-LEVELER: This will simply hold the wings level while you figure out what to do next.|
|HDG : HEADING HOLD. This will simply follow the heading bug on the HSI or Direction Gyro.|
|V/S : This will hold a constant VERTICAL SPEED by pitching the aircraft nose up or down.|
|HOLD: This will hold the current or pre-selected ALTITUDE by pitching the nose up or down.|
|SPD : This will hold the pre-selected AIRSPEED by pitching the nose up or down. (leaving throttle alone)|
|PTCH: Pitch-Sync: Use this to cause the plane to hold it's nose at a constant pitch attitude. Commonly used in King-Airs to just hold the nose somewhere until the pilot decides what to do next.|
|ATHR: This will hold the pre-selected AIRSPEED by adding or taking away engine thrust.|
|FLCH: Level-Change: This will use THROTTLE to go to a new altitude, just adding or taking a way a bit of power to change altitude. Commonly used by airliners to change from one hi altitude to another in cruise.|
|LOC: Localizer. This will fly a VOR radial or ILS localizer, or to a GPS destination.|
|G/S: Glideslope: This will fly the glideslope portion of the ILS.|
|VNAV: Vertical Navigation: This will fly the altitude commanded by the FMS if you have an FMS in your airplane.|
|BC: Every ILS on the planet has a LITTLE-KNOWN SECOND LOCALIZER THAT GOES IN THE OPPOSITE DIRECTION AS THE INBOUND LOCALIZER. THIS IS USED FOR THE MISSED APPROACH, ALLOWING YOU TO CONTINUE FLYING ALONG THE EXTENDED CENTERLINE OF THE RUNWAY, EVEN AFTER PASSING OVER AND BEYOND THE RUNWAY. To save money, some airports will NOT bother to install a new ILS at the airport to land on the same runway going the other direction, but instead let you fly this second localizer BACKWARDS to come into the runway from the opposite direction of the regular ILS! This is called a BACK COURSE ILS. Using the SAME ILS in BOTH directions has it's advantage (it's cheaper) but a drawback: The needle deflection on your instruments is BACKWARDS when going the WRONG WAY ON THE ILS! Hit the BC (back coourse) autopilot button if you are doing this. It causes the autopilot to realize that the needle deflection is BACKWARDS, and still fly the approach. (Note: HSI's do NOT reverse the visible needle deflection in the back-course because you turn the housing that the deflection needle is mounted on around 180 degrees to fly the opposite direction... thus reversing the reversal!) (NOTE: The glideslope is NOT available on the back-course, so you have to use the localizer part of the procedure only.)|
|WING-LEVELER and PITCH SYNC:
Just hit them and they hold wings level and pitch-attitude at the current pitch.
|HEADING, VERTICAL SPEED, SPEED-HOLD,
Just hit them and they will hold whatever values are entered into the selectors.
Note! When using VERTICAL SPEED, keep an eye on your airspeed and adjust throttle as necessary (or use ATHR)! VERTICAL SPEED will try to maintain your set vertical speed and will stall the plane trying.
Just hit it and it will climb or descend to and hold whatever value is entered into the selector. Note: If you do not have an altitude SELECTOR instrument, then the autopilot will simply hold the CURRENT altitude.
Note: You must FIRST ENTER THE ALTITUDE IN THE SELECTOR, THEN HIT THE ALTITUDE HOLD BUTTON. Order matters. Why? Because ATC will often tell you to expect a new altitude in 10 minutes, so you want to be able to dial the expected altitude into the autopilot in advance, even though you aren't allowed to actually climb or descend yet. Thus, FIRST enter the desired altitude. Then, whenever you like, hit the ALT button to go to that altitude. Then enter a NEW altitude... the plane will not go there until you toggle the ALT button again!
Once you've engaged ALT HOLD, dial in the vertical speed you want to reach the selected altitude at. Keep an eye on your airspeed and adjust throttle as necessary (or use ATHR)! ALT HOLD will try to maintain your set vertical speed and will stall the plane trying.
You must be established with ALTITUDE HOLD and AUTOTHROTTLE, holding a constant altitude and constant speed. Dial in the new altitude and hit the FLCH button. Then add or subtract power to climb or descend.
When do you use ALT HOLD and when do you use FLCH? FLCH is an effective mode for climb-out in heavies. It allows you to set the engines for climb power, and then let the plane climb to cruise altitude at whatever rate the engine power will allow. Remember that the engines become less powerful at higher altitudes, so your climb rate must be less as you approach cruise level. If you try to climb out using ALT mode with a set vertical speed and ATHR, you'll periodically have to reduce your climb rate to avoid overstressing the engines, or, in the extreme case, running out of power, losing airspeed, and stalling the plane.
ALT HOLD is the better choice for descent, giving you a predictable desceent rate, and with ATHR, predictable airspeed, getting you to target altitude at the right time and place.
|LOC and G/S:
These are the ones nobody can figure out. Here is how they work: They must obviously be able to fly either NAV-signal 1, NAV-signal-2, or GPS. But how do they know which of those 3 signals to use? The answer is the switch labelled "NAV-1 NAV-2 FMC/CDU", (with filename "but_HSI_12GPS" in the HSI folder). This switch, based on its position, will cause THE HSI AND THE AUTOPILOT to be based on either Nav-1, Nav-2, or the Flight Management Computer (which gets its signal from the GPS).
|If you set this switch to Nav-1, then the the HSI will show deflections from the Nav-1 radio, and the autopilot will fly VOR or ILS signals from the Nav-1 radio if you hit the LOC or G/S buttons.|
|If you set this switch to Nav-2, then the the HSI will show deflections from the Nav-2 radio, and the autopilot will fly VOR or ILS signals from the Nav-2 radio if you hit the LOC or G/S buttons.|
|If you set this switch to FMC/CDU, then the the HSI will show deflections from the GPS, and the autopilot will fly to the GPS destination if you hit the LOC button. Remember that if you enter destinations into the FMS, they will automatically feed into the GPS, so the autopilot will follow them if you select LOC|
|Enter an ALTITUDE in the ALTITUDE window to hold until you intercept the ILS.|
|Hit the altitude HOLD button to hold it.|
|Enter a HEADING in the HEADING window to hold until you
intercept the ILS. Check your map to make sure the heading will cross
the localizer centerline an adequate distance away from the airport.
|Hit the HEADING HOLD button to hold it.|
|Hit the LOC button. It will ARM (orange)|
|Hit the G/S button. It will ARM (orange)|
|Now, as soon as you intercept the
the LOC will go from orange to yellow, abandoning the HEADING mode and flying the localizer.
|Now, as soon as you intercept the
CENTER of the glideslope:
the G/S will go from orange to yellow, abandoning the ALTITUDE HOLD mode and flying the glideslope. The autopilot will then track you right down to the runway, and even flare at the end, cutting power if autothrottle is engaged.
Back to the Flying page