When established on final, set the MDA/DA (SOP-forgetting ATC said 1700ft...they did then say "cleared for the approach".) but still in VS: down you go all the way to the MDA, possibly before the FAF=bust 1700ft at DNNIS.
Good job Capn Bloggs!
Here's another from the old Westwind 1: (with old fashioned Collins F/D mode controller) AP is engaged and GPS NAV source selected with course captured. this is planned as a LNAV only approach with manual step downs. ATC tells you to "descend and maintain 1700 to DNNIS cleared approach". PNF dials up 1700 on the preselect and presses ALT SEL on the mode panel. You pitch wheel the nose down to establish a nice rate of descent then select VS to hold it at that ROD. Neither of you notice that the "ALT SEL" caption is not illuminated. (SimuFlite mantra: latching indicator on the button is a rumor and the lit mode caption is confirmation!) Since ALT SEL is not armed you'd better be keeping your scan up if you're gonna catch this error before it turns into an altitude bust. You either bumped it out of ALT SEL when pushing VS or it was never engaged when it was selected. Just one of those gotchas you learn to look for in this airplane, fancy GPS/FMS or not.
From the Lear 60 with Proline 4 and UNS1-B or C dual FMSs:
Same approach and instructions as before. 1700 is preselected and ALTS mode auto engaged. Select VS mode and spin the VS knob to desired descent rate. This will be a LNAV/VNAV approach and doing the proper things in the proper order at the proper time is essential in order for the vertical modes to behave as desired. Upon capturing 1700 the ALT (hold) mode will auto engage At this time the approach mode may be armed and new altitude (MDA or MAA as appropriate) may be set in the preselector. If the ALT preselect is changed prior to ALT capture at 1700 the AP will be bumped out of ALTS mode and will continue descending in PITCH mode until a vertical mode is selected. Another gotcha that you hopefully learn in a way that doesn't have any real consequences.
But as I indicated before, I've made these errors myself and I'm rarely surprised when I see these or other similar oopsies in the cockpit whether flying with very experienced PICs or brandy-new nugget co-pilots. To date neither has led to anything more than a need to make a timely correction. I have known other pilots who didn't catch it in time to avoid consequences and I wouldn't want to trade places with them. In the best of circumstances one's superior airmanship will make it unnecessary to display those superior skills or something like that...
In my experience these "rookie" mistakes usually happen when under time pressure of either the externally or internally generated variety. Tired or mentally drained pilots make plenty of errors, especially when they allow themselves to become task saturated. Being "go mission" oriented folks in general, pilots are particularly prone to continuing an approach even when behind the task curve. NTSB reports repeat the same theme over and again. Prior Planning Prevents P!ss Poor Performance (the 6 'P"s) is a good way to remind oneself of the importance of effective cockpit work flow management.
The magnitude of consequences resulting from whatever errors that ARE committed is determined in large part by how soon they are detected and rectified. A habitual pattern of crosschecking and rechecking coupled with a cynical refusal to believe everything will happen as intended goes a long towards having the right attitude. Admit that being 99.9% infallible isn't nearly good enough and be prepared to detect and correct those mistakes before anyone else notices.
That way even your flying partners might begin to think you know what you're doing some of the time!
And hey the flights seem to go pretty smoothly too...
Man I gotta get back in the air. This groundpounder teaching stuff I've been doing since I lost my flying job sucks.