Mountain RNAV: The Missed Approach You Cannot Fly

Straight-in: legal, with almost no margin. Circling: impossible.

Straight-in LNAV:

• Required visibility 1 1/4 SM; reported 2 SM - passes.
• Ceiling is not a legal requirement for an instrument approach, but it predicts what you will see. A 900 ft overcast over a 3,440 ft field puts the bases at roughly 4,340 MSL - about 100 ft above the 4,240 MDA. You should expect to break out essentially at minimums, every time, with no room to descend and get comfortable.

Circling:

• The circling MDA is 1,200 ft above the airport, but the ceiling is 900 ft AGL. You cannot legally descend below the circling MDA until in a position to descend for landing while remaining clear of clouds (§91.175(e)) - and at 1,200 AGL you would be inside the overcast. The maneuver is not available tonight whether or not the night restriction applies.
• The 'NA southeast at night' note is a second, independent reason: it removes an entire sector from the only direction you might have wanted.

So RWY 27 straight-in is the only usable option - which makes the next question decisive.

No - you are roughly 40 percent short of the required gradient.

• Groundspeed on the missed: TAS 115 + 10 kt tailwind = 125 kt.
• Required rate = 425 ft/NM x (125/60) = ~885 fpm.
• Your airplane: 550 fpm at 125 kt GS = 550 x (60/125) = 264 ft/NM.
• 264 vs 425 = 38 percent short.

Consequence: the 425 ft/NM is not a suggestion - it is the obstacle clearance gradient the procedure was designed around, in rising terrain. If you go missed, you will be below the protected surface and flying into terrain you cannot see at night.

Note the wind makes it worse, not better: with a 10 kt headwind (GS 105) you would get 314 ft/NM - still short. There is no configuration change in a normally aspirated single that finds 885 fpm at 110 KIAS in a missed approach at 4,000 ft.

Practical rule: the climb-gradient note must be checked at preflight, alongside the weather. If you cannot make it, you cannot shoot the approach, because the missed approach is part of the approach.

Divert now, while diverting is still a choice.

Chain of reasoning:

1. The ceiling (900 ft) sits 100 ft above the MDA, so the probability of breaking out and landing from the straight-in is modest, not high.
2. The probability of going missed is therefore high - and the missed approach is impossible for your airplane.
3. High probability x unacceptable outcome = do not start. Reverse the numbers: the approach only works if you get the 100-ft break, and the terrain is unforgiving if you don't.

So: turn toward an airport with an ILS or LPV in non-mountainous terrain, tell ATC the reason ('unable the missed approach climb gradient at [field], request [diversion]'), and recompute fuel on the way.

If you were already committed and could not divert, the only defensible move would be to negotiate an alternate missed-approach procedure with ATC before the final approach fix - one that keeps you above a known MEA and out of the terrain - and to state plainly that you cannot fly the published missed. Inventing a missed approach at the FAF in rising terrain is how this ends badly.

What would have prevented it: reading the climb-gradient note during preflight, computing required rate at expected groundspeed, and never launching to a one-way-in airport.