The danger of setting the wrong QNH | Blunder Error Demonstration by a Real 737 Captain

[@Malk51]

All hail the 'B' key.

[@rockyjetproject1345]

😂been using it since 2008

[@saml6084]

Not in x-plane.

[@Maveriqxs]

Yay tutorials! Any chance we could get more tutorials please (I know you're really busy of late), would love to get some updated tutorials for the virtual type rating for the 73 in MSFS! I have a few mates I've converted into avgeeks, and I show them your channel and they always say 'FD2S is on FSX is that still relevant?' and I'm like 'yes, Capt. Sam's tutorials are the best trust me!' Keep up the amazing work!

[@VNAV_PTH]

12:09 Ha, you did it! That GIF you put on screen remind me of the old days when you were doing tutorials! Love it! 😂

[@VNAV_PTH]

"I was just doing what I was told to do" - VNAV PTH

[@johnboy8846]

another great video thanks Capt

[@derrick1707]

Great case study. Thanks for replicating.

[@Thrust-Set-Simulations]

Very interesting. Will now put the VSD on copilot side. 👍🏻

[@robbo1169]

Love the tutorials. Keep up the good work

[@hassobasso7067]

Look who's back! Hope you are doing well. What happens when you have to hold unexpected, and you havent taken extra fuel, besides the normal ofp fuel (trip/cont/alt/finres) ? You subtract it from contigency fuel right? And after that?

[@albertlopezdiaz2420]

At that time you will need to take a decison. Either stay in the hold and commit to your destination with the alternate fuel, or divert.

[@hassobasso7067]

@@albertlopezdiaz2420 hmm makes sense indeed, thanks for clearing that up.

[@Papershields001]

Morning Cap!

[@flightdeck2sim]

Hi Rory!!

[@iitqrxz]

What mic do you use? It sounds lovely.

[@flightdeck2sim]

It’s the boom mic off the Steelseries Arctis 5 👍🏼 FD2S

[@andrew9027]

Where does the VSD get the aircraft altitude? and why wouldn't it be affected by the wrong QNH setting? I ask as if this is possible why wouldn't Boeing enter a feature to alert the pilots that the VSD source altitude and the PFD altitudes disagree.

[@flightdeck2sim]

The info I have is quite limited. I understand that the terrain profile is based on geometric altitude calculated by the EGPWS terrain database. The altitude data comes from the ADIRU. It reacts just like it did in the MOD, if you have the wrong QNH set the runway and approach path will move above/below the depicted terrain. The question re why Boeing haven't added an alerting feature is a good one! Ultimately it's our responsibility to ensure we have set the correct QNH..... FD2S

[@saml6084]

And people complain about the US using in. of mercury but in reality this scenario is less prone to happening in the US.

[@Arcadiez]

How do you calc the n1 percentage on the MAX for F30 ans F40?

[@Brendanmccreight]

Would you ever use the VSD other than a non precision approach in low visibility?

[@adamwallace0929]

Used for every approach, including ILS approaches. Selected after completing the FRISC checks or before the approach checklist is carried out

[@Elnino2910]

@@adamwallace0929completely operator specific. It has absolutely minimal benefit on an ILS approach.

[@adamwallace0929]

@@Elnino2910 yes of course, Brendan asked a question and I replied to it. I couldn’t comment on what other airlines do regarding the use of the VSD, because I don’t know.. Same regarding the FRISC checks, do other operators do the checks? No idea. Only commenting from what I know

[@Elnino2910]

@@adamwallace0929 fair enough but your original comment didn’t say this and made it sound like this was standard across operators

[@jumpnrun3368]

Lovely thanks. But here´s my question, why is it not more common to use radio minimums on airports where there is no uneven terrain before the runway. That would lower the risk of such incidents because the minimum is based of heigh above ground, not air pressure.

[@737Adventures]

You’ll be surprised at the amount of airports that have terrain that inclines or declines towards the threshold of a runway.

[@flightdeck2sim]

Exactly as pointed out by @737Adventures. A lot of airports have undulating terrain on the extended centrelines so no good using RA to assess vertical profile. FD2S

[@rynovoski]

Curious: I’ve never seen you use the VSD on a stream. When would you and when would you not? I guess RNAV approaches? Ah, at the end you mentioned probably why: FO side is not modeled, and you’re single pilot. Apart from other things, being visual, etc.

[@aviationsummaries7919]

How come baro altitude was not checked with the "1000"- callout, basic stuff, should indicate elevation plus one thousand feet, otherwise GA?

[@flightdeck2sim]

Simple in principle but this presumes the terrain around 3nm out (typically the distance you are around 1000ft AAL) is completely flat which is often not the case. RA is great for detecting gross errors but not really for anything less than 10hPa. FD2S

[@aviationsummaries7919]

@@flightdeck2sim Ok true! However instrument charts often prescribe a hard altitude cross-check at about 4 Nm. The chart you demonstrated provides this at 4.8 Nm. Furthermore charts include mile-on-mile basis reference altitudes for LNAV and LOC CDFA. Cross-checking these altitudes could have prevented this incident, and often times are regarded complacent. Good practice would be to cross-check always, even in ILS and LPV.

[@flightdeck2sim]

That 4.8nm height check point is based on barometric altitude and not radio altimeter height so isn’t going to help you if the wrong QNH is set. As discussed before if the radio altimeter is completely different it could be an indicator of an incorrect QNH setting but if the runway is located on a cliff or has high terrain on the extended threshold it’s not going to be useful in detecting small differences. I don’t know of any approach chart that uses radio altimeter or references height above the ground. All distance cross checks using a barometric altimeter for vertical navigation (that’s how VNAV works and the Airbus equivalent). This means you’re prone to QNH Blunder error as it will not detect an incorrect barometric altimetry setting. Altitude distance cross check with the altimeter will always show you on profile whatever the QNH. We demonstrate this during the Type Rating and point how (A) - the radio altimeter MIGHT” help detect QNH blunder error but only really useful for gross QNH errors (+/-10 hPa) and how the VSD will move the runway display. Thankfully ILS/GBAS is not vulnerable to blunder error (using an external beacon).

[@aviationsummaries7919]

​@@flightdeck2sim I disagree. Imagine you would be stationary at the 4.8Nm point with the correct altitude and correct QNH set. Now start moving the baro dial, the altitude indicator would show incorrect altitude in reference to the chart, wouldn't it? Why would the cross-reference altitudes be published in the first place then? And I think there has been incidences with ILS where overdue maintenance or equipment malfunction have led to false glideslopes being followed, which could have been noted with altitude cross-checking. I have personally flown an ILS where DME malfunction gave false altitudes at published DME distances while being in IMC, which I noted during the approach. That was due to equipment malfunction at the airfield, and this led to a bulletin in the organization for that airfield. Infallibility of any equipment does not exist.

[@flightdeck2sim]

@@aviationsummaries7919 I think you're misunderstanding this situation. So you're quite right, if you were stationary and changed the QNH the altitude would indicate the incorrect altitude and you'd see the error. The problem is you're not stationary, you're moving at +150mph. Secondly refer to 10:20 of this video. As soon as I set 1001 the altimeter and VNAV profile instantly changed and if I was to do a altitude distance cross check at that exact time you would see the error BUT watch the aircraft, it levels off to recapture the VNAV PTH and the altitude distance cross check when back on path would still show me on profile. Altitude and distance cross checks are great but you MUST have the correct QNH set. You are also correct re false ILS G/S captures. Altitude distance cross checks will show you off the correct path but we are referring to approaches using BARO-VNAV and Non-Precision Approaches. Please take a look at this EASA article - www.easa.europa.eu/community/topics/incorrect-barometric-altimeter-setting which explains exactly what's happening. Note the following quote. "It is particularly worth highlighting that when using barometric altimetry for vertical navigation, altitude/distance cross checks in the standard operating procedures do not detect an incorrect barometric altimetry setting." Hope this helps 🙂

[@JeremyBrady-j2g]

What airline do you fly for?

[@flightdeck2sim]

Alpaca Airways.

[@JeremyBrady-j2g]

Thank you for the reply. What real world airline do you fly for?@@flightdeck2sim

[@GREGORY5TV]

747-8 also has vsd

[@XavierJensen-c1e]

At 12:52, you mention "the Air France crew error"..but it wasn't an AF crew nor an AF flight!

[@martin_gkf]

... Then again: if the VSD knows where the runway is according to the QNH AND Also knows where the ground is - why not just let it calculate the correct QNH to put the runway where it is supposed to be - or, if they don't match give oral warning When approaching the FAF or something?

[@albertlopezdiaz2420]

Because it has to be temperature corrected also. That means that in temperatures near 0 or below, even with the correct Qnh set, the runway will show below the ground if no isa devation is set on the descent forecast page.

[@rustyc6805]

Does anyone know the flight number

[@flightdeck2sim]

Of the CDG incident, it was Norwegian Air Sweden flight D84311 (Info in the video description!) FD2S

[@rustyc6805]

@@flightdeck2sim sorry bud guess I'm lazy 🏴󠁧󠁢󠁳󠁣󠁴󠁿🤣

[@rustyc6805]

@@flightdeck2sim PS would love to see another DC-6 flight. Absolutely loving that machine just now. I would also love PMDG to implement a similar thing for the 737 second officer. Can't imagine that will be too much work says a mechanical engineer 🤣. Awesome channel bud, very informative and entertaining also. 🤟

[@allanj]

Hmm, really? Boeing has an advantage over Airbus...? That can't be true... ;)

[@flightdeck2sim]

Maybe Airbus has an equivalent? Not sure! FD2S

[@flightdeck737]

What are your PC specs and your XP11 Settings?