Barometric Minimums Selector

[Guest Bryan]

Howdy,The Baro Mins scale only goes up to 2500, which makes it a tiny bit tough to set DA at the higher airports. Also, I also like to set Baro Mins on dep to flap retraction altitude so I have visual indication of on the PFD when to start cleaning up. Again, the 2500 limitation can make that restrictive, esp if you can't start cleaning up till 3000 due to noise abatement.Can we look forward to this being fixed?Cheers, Bryan

[Guest MSMITH6]

Bryan-Could you be thinking in terms of altitude above sea level versus altitude above the ground? You use this to set the decision height "above ground level". I'm unaware of any approach that has a DH greater than 2500' AGL. There may be some, though. KASE is something like 2380' AGL for the VOR/DME approach so that's pretty close.

[Guest lbb]

Haven't checked Brian's problem (I live in Holland :-) ), but just to make sure: BARO is for setting the altitude above sea level, so I doubt if that is limited to 2,500 feet in real life. BARO is used for most approaches. And as you say, I too use it for setting thrust reduction altitude.RADIO is for setting height above ground level and AFAIK is only used for CAT II and III approaches.Leo Bakker

[Guest Iz]

It isn't limited to 2500 ft, Leo is correct. BARO is always above sea level, not above ground. For departure, we set the BARO bug at n-1 acceleration altitude, which is usually 1000 ft above the ground (this is the altitude that you start accelerating when you lose an engine on takeoff, very critical).

[Guest lbb]

Hi guys,To get back to the original question, I just checked it and I too found it is limited to 2,500 feet in the PMDG737, which, as Iz has confirmed, is not as it should be.Another item on the wishlist for the 800/900 I guess!Leo Bakker

[Guest Stefan Bergert]

AFAIK, DH is also used on CAT I approaches -> only when flying non-prec. approaches, you use the BARO (like LOC, NDB, VOR, GPS appr.), on prec. approaches you use DH.Regards,Stefan

[Guest Iz]

Stefan, on a CAT I ILS you use the BARO setting, trust me :) On the approach chart, you will also see that the Decision ALTITUDE is given (with height above ground in brackets and small print). This DA is the figure you use, since the height in brackets is the DA above a certain elevation, either the elevation of the airport reference point, or, if there's a big difference, the height of the highest point in the runway touchdown zone (the first 1000 ft of the runway). Either way, the decision height there does NOT correspond to a radio altitude! On CAT II approaches and higher, a RA value is given.

[Guest Stefan Bergert]

rgr that ;-)Thanks,StefanAlthough I thought when there's a DH of 200ft (DAlt -rwy elev.) it's also 200ft RA which you could set?

[Guest Iz]

Nope, only in theory if the height in brackets was referenced to the TDZ (touchdown zone) elevation and the point where the glide slope would have you at that height, would have exactly the same elevation.The thing is, that 200 ft is about 0,6 nautical miles before touchdown point. That's 1.1 kilometers. There might be a small hill or a small object, maybe a road or a trench or some trees there. So in fact, the RA may tell you you're at 200 ft RA, while in fact, you're still 250 ft above TDZ elevation and you make a missed approach prematurely. And believe me, I've seen my share of tight calls where you see the approach lights right at minimums.Now for CAT II and CAT III approaches and runways, there are extra requirements for the runway and approach facilities, including a completely flat area in front of the runway. It doesn't have to extend out that much (1.1km) because CAT II DH is about 100 ft RA (which is 300 meters before the threshold of the runway) and is corrected for even a single foot of elevation difference, and CAT IIIa DH is 50ft, which is right above the threshold (CAT IIIb/c = no DH).

[Guest Stefan Bergert]

Allright, thank you very much indeed :-) !(The explanation is really good)BTW: Are you a professional pilot in real life or something like that? To me it seems a bit like thatStefan

[Guest Iz]

You're very welcome!Yes, I fly the 737NG since a couple of months and the 757 before that.

[Guest tmetzinger]

>You're very welcome!>>Yes, I fly the 737NG since a couple of months and the 757>before that.Hey, IzCorrect me please, it's been a while since I've had to think about this.Does anyone ever fly autoland CAT I approaches? I thought not but can't remember the logic of why not.I thought the runway on the airport had to be at CAT II or III standards to allow autolands.I'm gonna show folks how to do the autolands on the PMDG but want to caveat it with real operational limitations.

[Guest Iz]

Well, you can do an autoland on a CAT I ILS, as long as the weather is good, and you still monitor the system (which is according to very strict procedures). Some airlines have a procedure where if one pilot becomes incapacitated, the other should do an autoland if at all possible. Since you have lost the monitoring function of the non-flying pilot, it's not a bad idea to let the aircraft land, while you monitor.To my knowledge, you can do an automatic approach and landing on a CAT I-graded ILS when weather is at CAT I minimums or better, but you have to be ready to do a missed approach at the first indication of faults.Another thing to remember is that when weather is not CAT II/III, the ILS protected areas are not protected. But this is not really a consideration in Flight Simulator :)

[Guest tmetzinger]

>To my knowledge, you can do an automatic approach and landing>on a CAT I-graded ILS when weather is at CAT I minimums or>better, but you have to be ready to do a missed approach at>the first indication of faults.>>Another thing to remember is that when weather is not CAT>II/III, the ILS protected areas are not protected. But this is>not really a consideration in Flight Simulator :)Thanks for the correction!