#Lnav aviation meaning how to
#Lnav aviation meaning full

With Vertical Speed, the pitch holds your climb rate constant, and the throttles vary to hold your airspeed.

#Lnav aviation meaning full

In 'full up' FMC/VNAV/Autothrottle airplanes, Level Change tends to be an 'all or nothing' option for power: full climb power to go up, and flight idle to come down (with pitch holding the commanded speed in both cases). Again, it is usually a 'dumb' mode and doesn't look at anything but vertical speed and aircraft pitch.

This mode usually adjusts the pitch of the aircraft in order to maintain a specific vertical speed.

For this reason (keeping in mind that passenger comfort could be an issue) many people avoid speed modes, especially at higher altitudes.

A lot of autopilots (especially older ones) tend to oscillate around the target airspeed and constantly pitch up and down while trying to fly a specific airspeed.

You could toggle between the 'normal' climb and the 'high speed' climb by hitting the FLC button more than once.

Another aircraft that I have flown in the past even had two climb schedules.For instance, a descent schedule might be Mach 0.80 until 29,000 ft., 350 KIAS until 10,000 ft. In some systems, the pitch is adjusted to maintain a specific climb/descent schedule which automatically changes based on altitude.In some systems the aircraft altitude is used to change the behavior (for instance, in one aircraft that I have flown, if you are below 8,000 ft MSL and hit FLC, it will descend at 1,000 FPM but if you are above 8,000 feet it specifies a 250 KT IAS hold).In some systems your actual altitude is compared to the selected target altitude and a minimum climb or descent is maintained even if the airspeed can't be maintained.By increasing power, your vertical speed will increase.By reducing power, your vertical speed will decrease.You usually control the vertical speed of the aircraft by making power adjustments:.In simple systems, the only inputs that are used are airspeed and aircraft pitch. This mode usually adjusts the pitch of the aircraft in order to maintain a specific airspeed.Regardless of which mode that is used, remember that it is the pilot responsibility to monitor the aircraft and to make sure that it is doing what they want it to do! Many autopilots don't even have a Flight Level Change mode, but instead have an Indicated Airspeed (IAS) mode.Īutopilot modes like these are typically 'dumb' and just do what they are told, without taking anything else into consideration.

Note that the modes even behave differently depending on the aircraft / autopilot, so referring to the actual aircraft/autopilot documentation is essential. They are different modes that control aircraft pitch in different ways, and as a pilot you select what you want based on your current requirements. I'm referencing the Garmin GFC700 as it's the only autopilot I've used with FLC mode, but I imagine the same steps and rules would apply.

for aircraft without auto throttle you'd set your target altitude, enable FLC, adjust your target speed if needed, and set your throttle for climb or descent to maintain the desired altitude change rate.

aircraft with auto throttle will maintain speed and an appropriate rate of descent automatically.

#Lnav aviation meaning how to

How to use FLC would depend on the equipment available to you: As another answer points out, by maintaining airspeed, climbs are made safer as the autopilot will not attempt to maintain a rate of climb regardless of whether or not the airspeed is safe.įLC mode is typically only available in advanced autopilots, and as far as I know they need to connect to an Air Data Computer to get the necessary information. Often air traffic controllers will request that you 'maintain 250 knots in the descent' or something to that effect, which is much easier to achieve when using Flight Level Change.

FLC mode maintains airspeed during a climb or descent, while VS mode maintains a specific vertical speed.