Set Boeing 777 barometric pressure correctly: use the EFIS BARO control, enter QNH, select STD at transition altitude, and avoid unit errors.
On a Boeing 777, use the BARO selector on each pilot’s EFIS control panel. Select HPA or IN, rotate the selector to the local QNH or altimeter setting, and cross-check the PFD and standby display. Select STD passing the transition altitude, then restore destination QNH at the transition level.
In real-world Boeing 777 operation and detailed aviation simulators, the altimeter and barometric pressure are not separate settings. The BARO control changes the pressure reference used to calculate indicated altitude; it does not change atmospheric or cabin pressure.
How do you enter QNH on the Boeing 777?
Set QNH on both pilots’ sides and on the independent standby flight instrument before departure or arrival.
- Obtain the pressure setting. Use the latest ATIS or ATC value. A METAR can provide it as a group such as
Q1016orA2992; our guide to identifying pressure values in a METAR explains those formats. - Select the correct units. Use the IN/HPA selection associated with the BARO control. Choose HPA for hectopascals or IN for inches of mercury.
- Enter the value. Rotate the BARO selector until the required pressure appears on that pilot’s primary flight display. If
STDis displayed, deselect the STD function so the local setting becomes active. - Repeat on the other side. The captain’s and first officer’s barometric references are independent. Do not assume changing one has updated the other.
- Set the standby instrument. Its pressure reference is also independent on accurately modelled aircraft.
- Cross-check the result. Both PFDs should show the same pressure and a plausible altitude. On the ground with QNH set, indicated altitude should be close to the published aerodrome elevation.
The exact mouse action varies between simulator aircraft: some use the wheel, some require dragging, and some provide separate click areas for STD and the unit selector. Trust the PFD indication rather than assuming the input was accepted.
What pressure should you set?
Use local QNH near the ground and standard pressure when operating by flight levels.
| Reference | Setting | When it is used |
|---|---|---|
| QNH | Local pressure from ATIS, ATC or weather | Departure, arrival and flight below the applicable transition level |
| STD | 1013.25 hPa or 29.92 inHg | Flight-level operation above the transition altitude |
| QFE | Pressure giving approximately zero at a specified datum | Only where a procedure or controller specifically requires it; uncommon in airline operation |
Do not type the aerodrome elevation into the BARO control. Enter the pressure value itself. For the underlying terminology and unit conventions, see our explanation of QNH and standard pressure in flight simulators.
When do you select STD on a Boeing 777?
Select STD during the climb when passing the published transition altitude, and select destination QNH during descent at the transition level.
The transition altitude is not universal. In the United States it is normally 18,000 feet, while other countries and individual aerodromes publish different values. The transition level may also vary with pressure, so use the charted, ATIS or ATC information rather than guessing.
Pressing the central STD function on the BARO control selects the standard reference. The PFD should then show STD. Operator procedures and ATC instructions govern the exact timing in an actual aircraft.
Why does the Boeing 777 altimeter show the wrong altitude?
An incorrect indication usually comes from the wrong pressure, unit, mode or instrument being adjusted.
- STD remains selected: deselect STD and activate the local QNH before the transition level on descent.
- HPA and IN are confused:
1016is a hectopascal value, while an AmericanA2992report means 29.92 inHg. - Only one side was changed: check the captain, first officer and standby indications separately.
- The pressure is stale: use the latest simulated or real ATIS/ATC value rather than an older departure report.
- QFE was entered instead of QNH: QFE can make the altimeter read near zero at its reference aerodrome.
- The simulator shortcut affected a different instrument: operate the virtual EFIS panel and verify the displayed value.
A small difference from published field elevation can result from pressure changes, instrument tolerances or simulator terrain and weather modelling. A large discrepancy calls for another check of the pressure source, units and STD status.
Does the BARO setting affect the radio altimeter?
No. The barometric altimeter calculates altitude from air pressure, while the radio altimeter measures height above the terrain directly beneath the aircraft.
Changing QNH or selecting STD does not alter radio altitude. Our explanation of how radio altitude differs from barometric altitude covers where that indication is used during approach and landing.
Also avoid confusing the BARO pressure control with the EFIS BARO minimums selection. Barometric minimums set an approach alert altitude; they do not set the altimeter’s pressure reference.