Freezing rain, airframe ice and the second approach

Freezing rain with temperature and dewpoint both at -1 °C means snow is falling through a warm layer aloft, melting, then falling into a shallow sub-freezing layer near the surface. The droplets arrive at the aircraft as supercooled water, which freezes on impact.

Implications:

• This is a severe icing environment, and it is worst where liquid water content and dwell time in the cold layer are greatest - precisely during the approach descent and the go-around climb-out, when the aircraft is slow, at high power and spending time in the coldest, wettest air.
• Ice accumulation is rapid: already 1 cm of clear ice on the wiper and landing-light area after one approach shows the accretion rate. Clear (glaze) ice is the most damaging form - it is heavy, adheres strongly and disrupts the aerofoil; expect increased stall speed, reduced climb gradient, degraded longitudinal stability and possible tail-plane effects, plus landing-distance penalties from the residual ice and the contaminated runway.
• Air data and engine intakes are also exposed; anti-icing protects only the surfaces it covers, and the airframe behind protected areas can still accrete.

So each additional approach increases the aircraft's degradation without improving the weather. The 400 ft go-around in a downdraught is also consistent with the convective/instability implied by the frontal structure.

The protected fuel is the final reserve (30 min) and the alternate fuel (55 min). Those must remain intact at the point of committing to the diversion. What can be spent while holding is the contingency and extra fuel: 35 min.

A second approach plus a missed approach from the hold costs roughly 15 min of that budget (approach, go-around, climb back). That leaves about 20 min of holding before the diversion must be started, i.e. roughly 35 min total from now before the aircraft must be heading to Bravo.

Now add the weather: the TEMPO says freezing rain and BKN006 until 23:00, so there is no positive forecast of improvement within that window, and the aircraft would arrive at Bravo with only the reserves intact and nothing more. If Bravo's actual weather were worse than forecast, there would be no discretionary fuel left - the crew would be committed. The time budget is therefore technically available but operationally hollow: 35 min of non-protected fuel is not a realistic allowance for a second approach in severe icing conditions with an unforecast downdraught already experienced.

Divert now to Bravo. Reasoning to be articulated, not just the outcome:

• The icing is severe, active and forecast to continue; the airframe already carries ice after one approach. Climb performance and stall margin are being consumed for no gain.
• One approach has already been flown and missed, in a downdraught that was not forecast. A second attempt adds 15 min of icing exposure and leaves only reserves.
• The alternate is comfortably above minima, above freezing, with good visibility, and is within the alternate fuel.

In the air: advise ATC of the diversion, request a climb to a warmer level (clear of the freezing-rain layer) and request the shortest routing; do not make large configuration changes with ice on the airframe; note that if the diversion itself becomes marginal, the alternate's weather must be re-checked, not assumed.

If the aircraft had to land at Alpha: expect a higher Vref and a longer landing distance, avoid flap 40 if the handling is degraded, plan a long, flat, slow approach with a firm touchdown, and treat the braking action as worse than 'medium' given the freezing rain. On the ground, have the airframe inspected for ice damage, report the icing encounter, and file a special air-report for the freezing rain.