"Caravan" to Africa

Santa Maria, Azores, Portugal

At Halifax this morning we had below-freezing temperatures and low clouds, a combination that mitigated against our departure, even though above the cloud layer there were clear skies and warmer temperatures due to a warm-front inversion. We dared not risk climbing through even a thin layer of icing conditions while carrying the extra weight of our trans-oceanic fuel load. The FAA has authorized us to fly at 30 percent over normal maximum weight for purposes of this flight. Our loaded weight is about 11,000 pounds. The Caravan is capable of flying at this weight, but its climb performance is diminished. So we waited, and by about 10AM the cloud layer had thinned enough to permit departure. We expected the route to be mostly clear of clouds, featuring above-freezing temps at 5000 ft. for the entire route, and at 7000 for most of the route. We would be looking at an arrival in the Azores late at night in clouds and rain, but with solidly positive temperatures. There are three airports with lighting and with approaches to low minimums: Santa Maria, Ponta Delgada, and the military airbase at Lajes. We even have the option of a diversion to the island of Madeira as a last resort. These circumstances provide an acceptable margin of safety. Mike is PIC on this leg: he decided to go, and Chad and I concurred. Further delay would not be helpful, since there was worse weather headed for both Halifax and the Azores tomorrow.

So off we went. Canadian regs require us to wear these heavy survival suits for such a flight.



After a nice loooong takeoff roll on runway 24 at Halifax, the airplane settled into a modest but steady climb. Mike and Chad are used to flying fully loaded Caravans at the high elevations and warm temperatures common in Kenya, and they say that the 30% overloaded Caravan, at sea level in winter, has performance similar to one with a normal full load coming out of Nairobi. There's extra power and lift available due to the lower elevations and cooler temps here. Initially we flew in bright sunshine over thinly scattered clouds, leaving the coast of Nova Scotia behind shortly after departing from Halifaz.



We headed southeast for about 200 miles before turning eastward toward the Azores. In that area the cloud layer became solid and we lost our view of the ocean. Mike said that he preferred seeing the cloud tops because it allowed him not to think about all that water. Darkness came quickly, at about 3 PM on my watch, which is still set to eastern US time. The early hours of darkness allowed us a smooth ride in clear air at 9000 ft., well above a solid cloud layer. The weather maps showed an area in mid-ocean of colder air, with freezing levels down to 5000 ft., and more extensive clouds and rain. This showed up as forecast, and we were forced to descend, in small increments, from 9 to 7 thousand, and then from 7 to 5, by repeatedly encountering the bottom of a downward-sloping freezing level. At each step down the hope was, maybe this will be low enough, but for a while it kept proving not to be so. While flying in cloud, hitting the freezing level immediately resulted in a layer of ice beginning to form on our airplane. It was clearly visible in the beam of a flashlight aimed at the windshield or out onto a wing, and each time it formed we were obliged to descend further to get rid of it. We also lost our smooth ride and had instead moderate turbulence, in addition to the clouds and rain. All of this was exactly as forecast and therefore not unexpected - but it was a bit disconcerting, to be flying in such conditions at night, so low over the sea and so far from land. But it did not provide grounds for turning back, even though at that point we still had the option of returning to Maine (though not to Nova Scotia or Newfoundland, where the weather was colder again). At all times in that period, there was still warmer air below, behind, and to the right, available if we needed it.



The weather forecast continued to prove accurate, and 5000 feet was the lowest we needed to go to keep the ice off the airplane. After a few hours, the freezing level at last began to rise again, the clouds thinned out and the ride became smooth. A few stars appeared above, and below there were glimpses of the sea through breaks in the clouds. Chad did not agree with Mike's preference for having clouds as scenery. He said he would rather be able to see other things. He wanted, he said, to see some ships, and was pleased eventually to be able to spot two of them. I was the non-flying crew member on this leg, and so was free to get some sleep, which I proceeded to do. Only to be awakened, about two-thirds of the way across the ocean, by Mike and Chad briefing each other on the approach they were planning to fly at Santa Maria. I asked whether it was now standard AIM-AIR procedure to begin briefing an approach while still 600 nautical miles away from the destination. They laughed and said, "What else is there for us to do?" Even though we had by then the option of returning to a higher flight level, it turned out that our tailwind was more favorably aligned, and our groundspeed greater, at 5000 than at 9000, so we stayed low. The route across the Azores preferred by Portuguese air traffic control passes over some high terrain on one of the western islands, and has a minimum eastbound altitude of 11,000 ft., which even there would have been above the freezing level again, so we could not use it. Chad planned an alternative route that remained over the sea at all points, and negotiated permission to use it from the Portuguese controller, who was friendly and helpful. Our HF radio communications with both US and Portuguese controllers remained clear all the way across. In the end Mike flew a routine night-time approach to the Santa Maria, with a 1000-ft. ceiling and 6 kilometers visibility. I said that it was not nearly as challenging as the approaches to minimums that Chad flew at Lancaster and Essex County. Mike said that after a such a flight, it was OK with him to have a routine approach. The distance was 1800 nautical miles (about 2000 ordinary miles). It took us 12 hours to fly. Now on to Spain. Posted by Barry at December 18, 2003 07:20 AM