January 2, 20215 yr I believe I successfully entered a plan into the 146-100 FMC from Ayes Rock to Sydney (YAYE to YSSY). I'd elected to land on RWY34L and for argument's sake to use the RIVET 3 STAR. I'm a newbie when it comes to FMCs, not too many of the planes in my virtual hangar have "proper" FMCs fitted: Ignore the 35000 feet cruise - I forgot to input 30000 when I obtained the plan although I did input that value in the FMC. When the TOD was reached I descended down to the next point which was 26800 at PKS according to the VNAV page on the FMC. I expected that at some point I would be descending down to 9800 at KADOM, but the VNAV page switched to TAMMI, yet the autopilot flew the plane to RIVET and BIGEM etc. There is no VNAV on the 146-100 so I was trying to match the rate of descent manually. In the end I knew I had to be at 3000 feet to intercept the 34L ILS, which, after flying out to sea on a 155 heading I duly turned back and landed. Due to my flightpath coming in from the northwest, did the FMC pick TAMMI on the VNAV even though the plane went out of its way to go to RIVET? Needless to say I'm a little confused at the moment. I cannot recall exactly what I did, but what SHOULD have happened? Hopefully those in the know can understand! thanks. Mark Robinson Part-time Ferroequinologist Author of FLIGHT: A near-future short story (ebook available on amazon) I made the baby cry - A2A Simulations L-049 Constellation Sky Simulations MD-11 V2.2 Pilot. The best "lite" MD-11 money can buy (well, it's not freeware!)
January 6, 20215 yr On 1/1/2021 at 7:39 PM, HighBypass said: I expected that at some point I would be descending down to 9800 at KADOM, but the VNAV page switched to TAMMI, yet the autopilot flew the plane to RIVET and BIGEM etc. There is no VNAV on the 146-100 so I was trying to match the rate of descent manually. ... Due to my flightpath coming in from the northwest, did the FMC pick TAMMI on the VNAV even though the plane went out of its way to go to RIVET? Your description is kinda hard to follow. But In the 146-100 the FMC's VNAV is advisory only, so it would have no impact on what route or altitude the aircraft takes when the autopilot is on. Based on your description it took the correct routing RIVET BIGEM TAMMI, so LNAV appears to have done its job. If i had to guess TAMMI may have been the next crossing restriction that had to be met (at or below 9000), that may explain why it displayed. There's no restriction at RIVET , and you could pass over BIGET without an issue. But to yad to be at least 'at' 9000 when crossing TAMMI.
January 7, 20215 yr Author @JeffLewis4 - thank you very much for that explanation. I did struggle with trying to explain what had happened! 🍻 What you said makes a lot of sense to me now. Yes the VNAV is advisory on the 146, but I had fun trying to match the suggested rate of descent by leaving the AP in V/S mode whilst manipulating the throttles (as per the QW manual). I look forward to carrying out other trips with this bird Mark Robinson Part-time Ferroequinologist Author of FLIGHT: A near-future short story (ebook available on amazon) I made the baby cry - A2A Simulations L-049 Constellation Sky Simulations MD-11 V2.2 Pilot. The best "lite" MD-11 money can buy (well, it's not freeware!)
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