ON SUPERCOOLED CLOUD DROPS AND TRAGIC AIR CRASHES
A few days ago (November 1, 2026) a sleek business class jet, on a flight from Austin Texas to the Bahamas happened to arrive over Florida just as a massive thunderstorm, driven by warm moist rising air was forming over central Florida.
The crew contacted Miami Air Control and was alerted to the dangerous storm clouds ahead. The crew of the Learjet 60 altered their route but could not avoid the encountering a zone of rapidly rising and descending air currents (turbulence) in the center of the storm. The plane entered an area of heavy rain, turbulence, and hail. They reported moderate icing and turbulence, and asked for permission to rise to higher elevation above the storm.
A few short minutes later the Learjet crew called in a “MayDay” as the plane began an uncontrolled loss of altitude. Only a few minutes later they were observed over an urban area in Greenacres, Palm Beach County, Florida. The plane was photographed from the ground, streaking out of the sky, nose down, like a lawn dart. Tragically the plane slammed into the earth at 20,000 ft per minute (or 227 miles per hour) and instantly exploded into a massive fire cloud killing nine passengers and crew. The explosion created a massive crater in an urban street surrounded by upturned burning and smoldering road asphalt.
What happened up there that can disable a high powered airplane?
At these altitudes far from the warming influence of the Earth’s surface, the air is very cold. Freezing temperatures usually occur above 10,000 ft to 15,000 feet (10k ft) above ground. But at 30,000 to 40,000 feet where these planes fly temperatures may fall very much below freezing. (Often as cold as: -47ºC or 47 degrees below zero).
The air is thin, there are few particles like dust or pollen grains up there. Winds are strong, (the Jets Streams) and flow smoothly from west to east, moving horizontal to the earth surface. The Jet Streams make flying at these altitudes….very pleasant. There are no birds to be struck and gobbled up in the jet’s air intake, few clouds, and most often little turbulence to annoy or theaten air passengers.
What is occurring in these thunderheads?
When warm moist air rises from ground level it encounters cooler air aloft, being warmer than its surroundings it continues to rise in this cooler air and as it does so it expands under lower pressure and. cools. Water vapor in the air condenses into cloud drops to form white puffy clouds. The process of condensation (from gas to liquid) releases heat warming the air and intensifying the lofting effect.
In this rising air water droplets may freeze into ice crystals when they rise above the freezing (OºC or 32ºF) level. Ice crystals can grow rapidly in moist air where water vapor deposits directly from gas into ice. Growth is very rapid. At some point the rising and growing ice crystals grow large enough and heavy enough to overcome the updraft lofting them upward—-at this point they begin to fall.
Falling ice crystals have considerable surface area…which, as the crystals fall, drags surrounding air (or entrains air ) to fall and create strong down drafts in the cloud.
These downdrafts plunge toward earth while, near-by, within the “active columnar-like storm-cell” inside the cloud, there are near-by rapid-rising updrafts. Collisions between the particles rising in the updraft air and those in near-by downdrafts cause electrons to strip off of the moving particles, dust, pollen as well as the forming ice crystals. These charges can build up in parts of the cloud to form charged areas within the cloud, which when they build up to high enough levels may discharge —as lightning strikes—from the negatively charged to the (positively charged) ground, or to other areas of the cloud which have been positively charged—-thunder and and lightning are the result.
For water to freeze into ice it needs some solid surface on which to attach. In the lower levels of the atmosphere, the troposphere (up to @30k feet) there are many sources of particulates, pollen, mineral dusts, organic particles, smoke particles from fires, soot, hydrocarbon condensate droplets, etc. Here ice crystals form readily. But higher up in the stratosphere and rising cloud tops there are few nuclei of condensation (like pollen, dust, etc.) ice can no form and water droplets remain as liquid even as the temperature falls well below freezing, even at air temperatures 10 to 40 degrees below freezing. Here supercooled droplets of water form. They remain in the liquid state, just ready to freeze solid if they come in contact with some solid object like a plane wing. These droplet forms are very serious threats to air traffic. They cause plane icing.
So beside the updrafts and downdrafts and turbulence in the top of a thunderhead cloud there are potentially damaging hailstones, strong up-and down drafts which cause wind-shear and most threatening of all, supercooled water drops..that can turn instantly into ice when the drops come in contact with any solid—like a plane’s outer skin surface.
Ice is heavy and adds weight to the plane, but more seriously, it interferes with air flow over the wing or tail-fin surfaces and can reduce the pilots ability to control or even more seriously— it reduces the lift the wings and the tail-fins generate.
It is the smooth flow of air over the top of the wing surface which generates lift. That is what keeps a plane aloft. Looking out on a wing from a passenger seat—you might imagine that the top surface of the long wing has a low pressure surface all along its length—“sucking” the plane wing upward. (There is no such thing as “sucking”) With loss of lift the plane begins to lose altitude. It falls like a heavy body falls through the air.
Ice on the wings simply reduces lift and the plane loses altitude. But it is the tailplane that operates like and upside down wing to hold the nose of the plane up. If ice builds up on tail-wIng or the “tailplane”, the craft is forced into a nosedive.
Early attempts to explain the tragedy of the Learjet 60 seems to suggest that icing was the main cause. In addition, evidence from the ground revealed the left tailplane (horizontal portion of tail assembly) was recovered according to recent reports some 4 miles from the crash site. Without that part of the tail the plane could no longer be controlled. It would make a nosedive to the ground. Perhaps the left tailplane could have been damaged and then detached as a result of the violent turbulence within the storm cell.
Icing and turbulence within clouds are both terrible threats to all planes in cold as well as tropical climates.
A tragedy occurred sadly as the result of being in the wrong place at the wrong time…
No comments:
Post a Comment