Time
The time in FlightGear and the properties affecting it are represented internally as properties in the /sim/time/ property subtree. The time can be manipulated using simulation rate/speed-up, to increase or decrease the speed of the simulation, and time warp/warp delta, to speed up or reverse local and UTC time.
The terminology used in FlightGear is a bit inconsistent even within the GUI. For the one used in this article, see terms used in this article.
Key bindings
| Keys | Binding | Remarks | |
|---|---|---|---|
| A | ⇧ Shift+A | Increase / decrease simulation rate | Affects /sim/speed-up
|
| W | ⇧ Shift+W | Increase / decrease the warp offset | Affects /sim/time/warp
|
| T | ⇧ Shift+T | Increase / decrease time warp in steps | Affects /sim/time/warp-delta
|
Simulation rate vs. time warp
Simulation rate and time warp manipulates the speed of the simulation and time in FlightGear. The simulation rate affects how much faster or slower the FDM appears to run and the time warp affects how fast local and UTC time changes. Neither simulation rate or time warp will affect for example the airspeed of the aircraft.
Simulation rate
When the simulation is sped up and slowed down, the integer factor /sim/speed-up will increase and decrease. The aircraft will appear to fly /sim/speed-up times faster over the terrain. When running FlightGear at normal simulation rate /sim/speed-up is one.
This will only affect the speed of the simulation, not the local and UTC time.
FDM rate
By default, the FDM runs at 120 Hz. You can change it by modifying the /sim/model-hz property.
Time warp
When time of day is sped up or reversed using time warp, /sim/time/warp-delta seconds are added or subtracted to /sim/time/warp each second. In essence, the former is not a factor and the latter is an offset. When running FlightGear at normal time warp /sim/time/warp-delta is zero, and when running in real time, /sim/time/warp is also zero.
This will only affect the local and UTC time, not the speed of the simulation. The aircraft will fly just as fast over the terrain, but the sun and clock hands will speed up or reverse.
Terms used in this article
The terms used in the source code, keyboard binding descriptions and Time Settings dialog labels are a bit inconsistent. Therefore, in this article these terms (mostly from the Time Settings dialog) will be used:
- clock time
- The local system time as represented by the
/sim/time/real/property subtree. - local time
- The in-sim local time as represented by
/sim/time/gmt+ the offset represented by/sim/time/local-offset. - real time
- When running FlightGear with zero warp, so that local time is equal to clock time, and zero time warp so that local time is at the same speed as clock time.
- simulation rate
- Simulation rate speed-up factor as represented by
/sim/speed-up. This is not related to the FDM rate, the speed at which the flight dynamics model is run. - time warp
- Local and UTC time change rate as represented by
/sim/time/warp-delta. - UTC time
- The in-sim UTC time as represented by
/sim/time/gmtand the/sim/time/utcproperty subtree. In essence the time shown on many cockpit clocks. - warp
- The offset between local time and clock time as represented by
/sim/time/warp.
Nasal scripting
See maketimer() and settimer() for details.