Can someone pls explain the QNH/QFE ?

Question

in as much depth as u can please.

Answer 1

QNH gives you altitude above sea level based on your barometric setting of the altimeter, whereas QFE is altitude above ground level at a particular point, ie an airfield.

Answer 2

QNH--The barometric pressure as reported by a particular station.

QFE--The barometric pressure as measured at a particular station.

Answer 3

Basically....

QnH is the Altitude above sea level.

QFE is the height above the ground of the departure air field.

After the "transition altitude" where you go from QnH to 1013mb or 29.92Hg, which makes the altitude of all the aircraft standardised.

Answer 4

Q comes from morse code meaning station.

In the US a pilot would set QNH (Station Normal Height) on the altimeter. It's the local altimeter setting. Say the local altimeter is given as 30.10 and the field elevation at your airport is 1135 feet above sea level. The altimeter should read very close to 1135 if the altimeter is set to 30.10 (Most airports are not perfectly level).

On flights longer than a few hundred miles, a jet would climb  to and cruise at an altitude above 18,000 feet into the flight levels. Until then, the pilot may be given different local altimeter settings to use away from the departure airport which are still QNH settings. The altitudes the jet passes through or levels off at are called altitudes, and based on local altimeter settings.

Passing 18,000 feet in the climb is called the transition altitude and the jet has entered into the flight levels and now sets the altimeter to the standard setting of 29.92 also known as QNE (Station Normal Enroute). A pilot might report "passing one seven thousand three hundred climbing flight level 230".

During descent from the flight levels, the reverse is made. Passing FL180 is called the transition level and the controller will give a local altimeter setting (QNH) to use once below FL180. A pilot might report "leaving flight level two five zero descending one five thousand".

In Europe the flight levels vary with each country, there is also transition layers. The layers might be a few thousand feet thick. For example, the pilot will set QNH on the ground, and climbing through 5,000 feet (transition altitude), set QNE. During descent, while using QNE (standard altimeter) and then passing through a transition level of 7,000 feet, QNH (local altimeter) would be used. The altimeter setting used in the transition layer is dependent on whether the pilot is in a climb or descent. These altitudes are listed on the departure and arrival charts.

QFE (Station Field Elevation) is used in Russia and China mainly and only for departure and arrival. Using the given altimeter setting, the altimeter will read height above field elevation on approach, and read zero at touchdown.

Answer 5

For the aviation industry, the atmospheric pressure at mean sea level has been standardised as 1013.25 mbars or 29.92 inches of mercury.

In the small window of the altimeter, if either of the above two values are set, then the altimeter should correspondingly read zero. This is known as QNH. Therefore, the altimeter in an aircraft flying with a QNH setting will show its height above the mean sea level.

The QFE, on the other hand, is the existing pressure at a given place like a runway, which may not be at the mean sea level. Consequently, when a QFE reading is set into the altimeter of the aircraft, the altimeter reads the height of the aircraft above this particular airfield.

To conclude, QNH setting will give height above sea level while QFE will give height above ground level at a designated place.