Rwy Elev: 0 hpa
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Rwy Elev: 0 hpa
Can someone explain why would a pilot need to know the Rwy Elev in hpa. Could it be that is use in conjunction with QFE, and if so how would it be use. Approach plates in the US don't display this particular information.
I am reviewing the approach for Hongqiao China ZSSS what is the importance of the chart in the upper left in the plain view?
thank U.
I am reviewing the approach for Hongqiao China ZSSS what is the importance of the chart in the upper left in the plain view?
thank U.
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I'm not an expert at QFE but according to the (Jeppesen) chart legend, the 0 hPa number refers to the "barometric altitude equivalent".
The way I understand it is such, that if you are using QFE and are receiving at QNH (e.g. from the METAR), subtract the "Rwy Elev" number from the QNH and get the QFE. E.g. at LSZH, with QNH 1013 hPa and Rwy Elev 50 hPa, use a QFE of 1013 - 50 = 963 hPa.
At ZSSS, airport elevation is almost sea level, so QFE and QNH are almost equal, hence Rwy Elev = 0 hPa.
However, I stand to be corrected by an expert.
As for the inset in the ZSSS chart (Jeppesen?), at least the Jeppesen 11-2 chart has a feet @ QNH to meters @ QNH table. China uses metric flight levels and altitudes, so the table is for those (western) airplanes using non-metric altitudes for quick conversion.
550m QNH equals to 1810' MSL. So, if you are asked to descend to 550m (QNH), ATC wants you at 1810' MSL.
The way I understand it is such, that if you are using QFE and are receiving at QNH (e.g. from the METAR), subtract the "Rwy Elev" number from the QNH and get the QFE. E.g. at LSZH, with QNH 1013 hPa and Rwy Elev 50 hPa, use a QFE of 1013 - 50 = 963 hPa.
At ZSSS, airport elevation is almost sea level, so QFE and QNH are almost equal, hence Rwy Elev = 0 hPa.
However, I stand to be corrected by an expert.
As for the inset in the ZSSS chart (Jeppesen?), at least the Jeppesen 11-2 chart has a feet @ QNH to meters @ QNH table. China uses metric flight levels and altitudes, so the table is for those (western) airplanes using non-metric altitudes for quick conversion.
550m QNH equals to 1810' MSL. So, if you are asked to descend to 550m (QNH), ATC wants you at 1810' MSL.
Dunno about "expert", but I teach this stuff regularly and EoD is quite right, it's used to derive the QFE when only the QNH is available. Some operators still use QFE, and some types require one altimeter to be set to Threshold Zero for take off performance reasons.
A common source of confusion in your situation of 0 hPa, is when do you follow the QNH Altitudes on the Approach profile, and when do you use the QFE Heights, when you haven't changed the actual altimeter setting?
A common source of confusion in your situation of 0 hPa, is when do you follow the QNH Altitudes on the Approach profile, and when do you use the QFE Heights, when you haven't changed the actual altimeter setting?
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Using QFE
There is one airport where our company has us using QFE, primarily, I suppose, because everyone else there is using it. Metric altitudes begin upon entering the FIR . A conversion table is used for this. Descending through the transition level, QFE is set in the altimeter. QFE comes from both the ATIS and the approach controller, so there is no derivation exercise from QNH. Conversion of feet to metres for each altitude assignment is continued until glideslope intercept. Using QFE has never been a problem. The conversion to metric becomes a well orchestrated exercise, each pilot doing their part.
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This is a throwback to when the military controlled all the avaition and airfields in PRC. In the beginning all airfields used QFE procedures. Increasingly however the airfields have been taken over by civilian authorities and companies and are now using QHN. To aid operators that were using QHN in the QFE environment Jepp introduced the conversion chart that I think you refer to.
This enabled crews to quickly convert a metric QFE clearance to QHN in feet and thus avoid the obvious errors in the heat of the moment.
Hongqiao is now a QNH airport along with Pudong ZSPD which would probably be your div airfield if you were going to Shanghai. From memory all the other airfields that an overseas operator would be allowed to file to in the Shanghai area are similarly QNH now.
This enabled crews to quickly convert a metric QFE clearance to QHN in feet and thus avoid the obvious errors in the heat of the moment.
Hongqiao is now a QNH airport along with Pudong ZSPD which would probably be your div airfield if you were going to Shanghai. From memory all the other airfields that an overseas operator would be allowed to file to in the Shanghai area are similarly QNH now.