A few days ago I was doing and ILS approach and after being transferred from approach to tower, I was instructed to go around because the QNH in the tower was gone. After 10 minutes or so they recovered it so I could land.
I was with the ATC on the phone and they said that is contingency and no operations are allowed if there is no QNH indication. I told them I was on final in VMC and with the runway in sight. Same answer again.
The QNH I was given by approach 3 minutes before could have change by just 1mb (25ft) in the worst case scenario.
My question is, is there any EASA rule that could explain this situation? I’m thinking of emailing the tower/airport manager in order to propose a change of the rule.
Regards
One assumption on ILS is that somehow the PIC is legally required to validate glide path at FAF using altimeter & QNH before descending on it, to avoid busting airspace or hitting terrain, ATC insisting on that during CAVOK is odd though 
This would have been funky with GPS 3D on WAAS, as the altimeter and it’s QNH is the weakest thing in that chain…GPS altitude & geometry work fine for LPV, LNAV+V and L/VNAV with SBAS
My question is, is there any EASA rule that could explain this situation? I’m thinking of emailing the tower/airport manager in order to propose a change of the rule.
Not an EASA land, at least 3 countries have different perceptions of lack of AD QNH on approach: in Germany, the whole airport gets NOTAMed closed to IFR (LBA, DFS, DWD seems to agree on this for Baro-VNAV but as precaution they decided to shutdown everything), in France, you can be given regional QNH if SATP/ATC are OFF but you fly on higher minima (they are written on plates with/without local QNH), in UK, I have flown approaches on QFE
Also, was your airport in “mountain area”? they may prohibit IFR operations without local & official QNH but other than “what can go wrong”? PANS-OPS ICAO Doc 8168 Vol II has provision for no AD QNH…
While 7hp delta between aerodrome & regional is enough to hit ground from ILS minima, I expect the winds to be in 100kts…
https://www.icao.int/safety/meteorology/amofsg/amofsg%20meeting%20material/amofsg.9.sn.030.5.en.pdf
Ibra wrote:
This would have been funky with GPS 3D on WAAS, as the altimeter and it’s QNH is the weakest thing in that chain…GPS altitude & geometry work fine for LPV, LNAV+V and L/VNAV with SBAS
It might be the weakest link – but it’s still an independent source for a check. The reason why one checks altitude on the glide path with the altimeter is not that the barn alt is more precise that the glide path – the opposite is the truth. The reason is to have an independent source of opportunity to figure out something is wrong with the glide path.
Checking an RNP-approach with the GPS altitude is not suitable for that purpose as the altitude source for both is the same.
Ibra wrote:
https://www.icao.int/safety/meteorology/amofsg/amofsg%20meeting%20material/amofsg.9.sn.030.5.en.pdf
I wonder if any pilot would be able to calculate this while already past FAF – therefore a go around is legally necessary…
speed wrote:
I told them I was on final in VMC and with the runway in sight.
Did you also tell them “cancelling IFR”? Being on a visual segment of an IFR flight also requires QNH…
Checking an RNP-approach with the GPS altitude is not suitable for that purpose as the altitude source for both is the same
Indeed but for RNP (non Baro), there is no requirement to cross-check the glide path on the pilot side: it’s done as part of SBAS algorithm (no SBAS it’s done as part of RAIM algorithm 2nm before FAF), then when flying the glidepath an FDE algorithm runs continuously to maintain glide path integrity…if you have 10 satellites, you can calculate “6 different altitudes” and make your mind that is very independent !
I agree on ILS, it make sense to cross-check QNH FAF & FAP and it’s a completely independant source
I wonder if any pilot would be able to calculate this while already past FAF – therefore a go around is legally necessary…
1ft for 1nm 
+200ft and you are largely OK, unless you are flying IFR on oceanic route not talking to anyone
speed wrote:
because the QNH in the tower was gone
I wonder about the redundancy of their systems! Only one QNH indicator and no backup? Really weird.
And given they knew how to “handle” the issue (i.e. telling you to go around), it’s quite likely it was not the first occurence
Ibra wrote:
Indeed but for RNP (non Baro), there is no requirement to cross-check the glide path on the pilot side:
Agree – as far as I remember, however, the decision altitude still refers to either a baro alt or (as DH) to a radar alt. So very late but still an independent source…
Hi,
The airport is at Sea Level.
ATC it’s a local procedure approved by Spanish CAA and if I don’t agree, I should complain to them. I told them that Flight Safety is concerned in this situation and they should also propose a change to Spanish CAA. No further reply from ATC. I will also complain to the airport manager.
The airport is sometimes without ATS so you can land and depart without qnh nor wind. Does this make sense at all?
speed wrote:
The airport is sometimes without ATS so you can land and depart without qnh nor wind. Does this make sense at all?
You can land there IFR without ATS? Didn’t know that this is possible in Spain…
