February 9, 20251 yr 1 hour ago, Stearmandriver said: Your scenario wouldn't give you any descent advantages over level change or VS anyway, and those modes will honor MCP altitude restrictions. I mean I agree totally! I mostly in the sim use VL then APP or if heading straight in APP alone. Personal preference to turn IN before I head down! I was playing devils advocate as Boeing sells to clients all round the world with different needs and wants, some alien to us. I could imagine someone landing via ILS in a flat desert not caring whether lateral or vertical kicks in first! In theory if further out you WILL be higher than FAF anyway right? Another thing at play is the (IMO after extensive testing) very sloppy and unreliable VOR/ILS capture with planes using default GPS in MSFS. It is common for the plane to turn in and intercept as soon as it detects signal rather than when the radial is close by. Not for this thread though! Russell Gough SE London
February 11, 20251 yr On 2/9/2025 at 12:09 PM, sloppysmusic said: In theory if further out you WILL be higher than FAF anyway right? Sure, but if farther out being down at that altitude could be completely inappropriate. Literally there will never be a time when you'd want the airplane to capture the glideslope before the localizer. I could see it being an option for economic reasons; heck, prior to the Max accidents, a second AoA vane was an option to be paid for. We had them so I never knew that until this all came out after the accidents, but it's pretty amazing the things that manufacturers charge for as options... And equally amazing, the number of operators who are cheap enough not to pay! Edited February 11, 20251 yr by Stearmandriver Andrew Crowley
February 11, 20251 yr 1 hour ago, Stearmandriver said: prior to the Max accidents, a second AoA vane was an option to be paid for. Wait....I've studied deeply the MCAS specs before and after update.....IF you had paid for the 2nd AoA sensor would MCAS have used both or just the one anyway? From my research ONLY the one AoE sensor was included in the MCAS logic. The new logic causing MCAS disconnect if AoE disagree occurred was only coded AFTER the tragedies? Not the thread for this but from memory the new FCOM detailed the new logic for MCAS used both sensors? Russell Gough SE London
February 11, 20251 yr 2 minutes ago, sloppysmusic said: Wait....I've studied deeply the MCAS specs before and after update.....IF you had paid for the 2nd AoA sensor would MCAS have used both or just the one anyway? From my research ONLY the one AoE sensor was included in the MCAS logic. The new logic causing MCAS disconnect if AoE disagree occurred was only coded AFTER the tragedies? Not the thread for this but from memory the new FCOM detailed the new logic for MCAS used both sensors? No, you're correct, the original version of MCAS would only ever have used data from one AoA input (and the new version will always compare across two inputs). What the second AoA sensor made available before (and still does) was the ability to compare values and display an AoA comparator flag, which is an excellent clue to explain all the other myriad and sometimes opposing alerts that are occurring. It can make what's happening a lot more obvious and might have helped the accident crews from an SA standpoint. Andrew Crowley
February 11, 20251 yr 33 minutes ago, Stearmandriver said: What the second AoA sensor made available before (and still does) was the ability to compare values and display an AoA comparator flag, which is an excellent clue to explain all the other myriad and sometimes opposing alerts that are occurring. Brilliant thanks for clarifying! Russell Gough SE London
February 11, 20251 yr Pictures https://ibb.co/ymy50c1Z https://ibb.co/WvTxGdnS Michael Moe Michael Moe
April 25, 20251 yr Author On 2/10/2025 at 11:48 PM, Michael Moe said: Pictures https://ibb.co/ymy50c1Z https://ibb.co/WvTxGdnS Michael Moe Nice pictures. Thank you.
April 28, 20251 yr Regarding LOC first, then APP... I cannot speak to the 737, but there is a programming variant in some 747 models that will let you capture the localizer and glideslope independent of one another. Other versions of other aircraft may behave the same way--I do not know how widespread this is in the world of avionics. The obvious fix is to hit LOC first until established, then APP, thus preventing an unprotected descent. Another equally obvious fix is to use APP, but fly an aircraft that won't descend without the localizer being captured. You can test this in MSFS, to see what the sim's (pr PMDG's) programming is. If you can't descend on the glideslope in the absence of a captured localizer, then doing "LOC first then APP" is harmless but unnecessary; all things being equal, it doesn't add any operational or safety advantage. Perhaps some real-world flight training departments teach it as a holdover, from times (or fleets) where "LOC first then APP" was a needed safety measure. Edited April 28, 20251 yr by prolixindec
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