“You must have been warned against letting the golden hours slip by; but some of them are golden only because we let them slip by.” James M. Barrie

“I saw the angel in the marble and carved until I set him free." Michael Angelo

Tuesday, December 11, 2012

The Invisible Killer

There is a weather phenomenon known to pilots which has caused the loss of many lives. This weather phenomenon is called a microburst and it has been compared to tornadoes and hurricanes. Microbursts can significantly affect people or property on the ground, but it is considered to be more dangerous to pilots. The reason microbursts are said to be “invisible,” is because they are difficult to detect.

Microbursts are a form of wind shear. Wind shear is a sudden and drastic change in wind direction, speed, or both within a small area. Wind shear can be divided into two components: vertical wind shear, wind shear measured in the vertical direction and horizontal wind shear, wind shear measured in the horizontal direction. The effects of a microburst are more dangerous when encountered near the surface. When wind shear occurs at lower levels in the atmosphere near the surface it is known as Low-Level Wind Shear (LLWS).

LLWS can form in several ways, but most of the time thunderstorms are the cause of the most severe type of wind shear, if under the right conditions. Certainly changes in vertical motions constantly happen through the life cycle of a thunderstorm. During the dissipating stage, the final stage of the thunderstorm cycle, the thunderstorm dissipates due to the overcoming downdrafts (downward moving–negatively buoyant air) that can reach approximately 6000 feet per minute.

Thunderstorms create the anvil–like shapes during the dissipating stage. The anvil–like shape is due to the weakening of vertical motions near the top of the storm and downdrafts overcoming the updrafts and dissipating the cloud from the bottom up. Downdrafts are formed by hydrometeor drag and evaporative cooling.

Precipitation (water and hail) drags air downward contributing to the generating of the downdraft is known as hydrometeor drag.  However, the biggest contributor to the downdraft formation within a thunderstorm is evaporative cooling.

Evaporative cooling is evaporation of rain and cloud drops or sublimation of ice crystals, making the air parcels colder than their environment and thus negatively buoyant. As cloud droplets becomes heavy enough to overcome the updraft and fall, they travels into a warmer environment, evaporating (changing state from liquid to gas) or sublimating (changing state from solid to gas) by taking heat away from its surrounding and cooling the air around. Entrainment, mixing in of drier air occurring along cloud edges, is also known to enhance the downdraft strength because it leads to evaporative cooling.

A lot of the mixing of drier air that occurs aloft is due in part by the jet stream at higher altitudes carrying dry air and mixing it with the thunderstorm. This increases the evaporative cooling and strengthens the downdraft and acting as a rear inflow jet by carrying the cold, dense and negatively–buoyant air to the ground.

When the downdraft occurs at the bottom of the thunderstorms, reaches the ground and spreads out, it is called a downburst. Downbursts can be subdivided into two: macrobursts and microbursts. A macroburst is a downburst in which a region of more than 4 kilometers (km) is affected; consequently, a microburst is a downburst affecting a region of 4 km or less.

Macrobursts can last up to 30 minutes with wind speeds of up to 116 knots. Microbursts however, are difficult to detect because they occur over a very small area. Some microbursts have been known to occur in a space of less than one mile horizontally and within 1000 feet vertically. The lifespan of a typical microburst is of approximately 15 minutes and although they are smaller than macrobusts, their wind speeds can be much higher, as high as 145 knots, the same as category 5 hurricane winds.

Dry microbursts also exist. They are harder to identify and are more commonly found in western U.S. in areas where there are dry conditions at lower altitudes and an increase in moisture with altitude. Dry microbursts often occur with less than 0.01 inch of precipitation as opposed to wet microbursts of 0.01 inch or more of precipitation. Virga, rain that evaporates before reaching the ground, is associated with dry microbursts and is present most of the time. Dry microbursts are as dangerous as wet microbursts.

But is this “killer” so “invisible”?—to an extent. Even though there are common systems already being used such as the LLWS Alert System and the Doppler Radar, there are other much simpler ways for pilots to detect and warn themselves of possible LLWS and/or microbursts as a last resort.

Taking a closer look at microbursts, there are some features that can be used to identify them. These features include some of the types of clouds generated by a thunderstorm as well as the use of a sounding.

A shelf cloud or arcus cloud is a cloud that forms as a result of the warm air lifted by the gust front of a thunderstorm and can be an indication of a microburst in the region. The downdrafts within a thunderstorm that reaches the surface as downbursts (microburst) transports the cold, dense, negatively–buoyant air and high wind speeds from higher altitudes to the surface from the rear inflow jet. Areas, sometimes called “pools” of cold air at the surface are known as the thunderstorm’s outflow. The storm’s outflow can be identified as small scale cold front, known as a gust front, decreasing temperatures at the surface and lifting warmer air.

Behaving as small scale cold fronts, under the right conditions, gust fronts can start the formation of other thunderstorms. Pilots inadvertently flying in thunderstorms can avoid entering a downburst situation if they spot a shelf cloud indicating the existence of a downburst.

Another indication of possible downbursts is the peculiarly–shaped Mammatus clouds. Mammatus are basically "blobs" of cooled air that sink under the anvil as a result of strong evaporational cooling by the interaction with dry air below the anvil. If flying into a thunderstorm inadvertently, pilots can predict the possibility of microburst situation through observing Mammatus clouds as an indication of strong evaporational cooling. However, this is still highly improbable since they form in a very turbulent environment. 

Soundings can also be used not only to predict the presence and strength of thunderstorms and thus the possibility microbursts, but also the type of microburst. “Inverted–V” soundings indicate dry microbursts are possible. This type of sounding indicates dry air at lower levels and moist air at higher levels, the opposite of the conditions expected with wet microbursts.

“Success is not measured by what you accomplish, but by the opposition you have encountered, and the courage with which you have maintained the struggle against overwhelming odds.” Orison Swett Marden

Monday, December 10, 2012

3 2 1 Descent

I’ve recently been taught that using the VNAV (Vertical Navigation) function to meet crossing altitude can get pilots into trouble. This for example, in terms of meeting a crossing restriction while descending on an Instrument Approach Procedure (IAP) or a Standard Terminal Arrival Route (STAR). This isn’t new. Pilots should know never to fully trust technology. There have been many incidents and accidents that are as a result of complacency.

Whether using VNAV or not, stabilized descent planning is important. A 3:1 descent is a good stabilized descent to use. Here’s how to plan one:

In order to establish a 3:1 descent and meet a crossing restriction, proper planning should begin various miles before, depending on the altitude to lose. The altitude to lose should be first determined by finding the difference between the crossing restriction altitude and the aircraft’s cruising altitude. Since 3:1 descent is going to be used, the difference in thousands of feet is multiplied by 3 to determine the distance to start the descent before the crossing restriction.

Speed reduction is an additional factor that needs to be taken into account when calculating the distance to begin the descent. Since transport category aircraft can’t reduce their speed and descend at the same time, pilots must level off to reduce speed. A rule of thumb to use to determine speed reduction distance is 1nm/10kts of speed reduction. This is then added to the distance determined to be used for a 3:1 descent.

In addition to finding the distance to start the descent before the crossing restriction, the Rate of Descent (ROD) that will maintain a 3:1 descent must also be calculated. For this we use True Airspeed (TAS), but since wind is always present, Ground Speed (GS) is used instead. The formula (GS/2) * 10 is the rule of thumb used to calculate the ROD. As the aircraft moves through different altitudes and descends to thicker air, GS will be changing through the descent and so the ROD must be periodically recalculated in order to continue to maintain a 3:1 descent. Below are some examples.

Example 1:

An airplane is being flown at FL200 on an arrival procedure and is 40 nautical miles (nm) from its next fix, FIRST. FIRST is at FL120 and the instructions are to cross it at 280 knots. The airplane is currently flying at 300 knots. There is a 40 knots headwind at FL200.

Distance to descend: 20000ft – 12000ft = 8000ft/1000 = 8 * 3 = 24 nm

Speed reduction distance: 300 knots – 280 knots = 20 knots/10 = 2 nm

Begin speed reduction: 26 nm from FIRST

Start descent: 24 nm from FIRST

3:1 ROD: 280 knots – 40 knots = GS = 240 knots/2 = 120 * 10 = 1200 ft. /min (initially)

Example 2:

Pilots flying an airplane at FL380 are instructed to descend to FL310 before passing its next fix, SECON. The pilots are also instructed to cross SECON at 330 knots. The airplane is currently flying at 360 knots. There is a 75 knots headwind at FL380.

Distance to descend: 38000ft – 31000ft = 7000ft/1000 = 7 * 3 = 21 nm

Speed reduction distance: 360 knots – 330 knots = 30 knots/10 = 3 nm

Begin speed reduction: 24 nm from SECON

Start descent: 21 nm from SECON

3:1 ROD: 360 knots – 75 knots = GS = 285 knots/2 = 142.5 * 10 = 1425 ft. /min (initially)

“You are not only responsible for what you say, but also for what you do not say.” Martin Luther

Saturday, September 22, 2012

The Beauty and Sadness of Cuba

The world is a beautiful place and I love to travel. Unlike some who can afford it, I haven’t been to many places, but I can’t complain. Within the United States, I’ve driven along most of the east coast of Florida, from Jacksonville to the keys, and once been to Grand Rapids, Michigan. Outside the U.S, I’ve visited my homeland, Cuba, and traveled to Italy twice passing through Positano to the south, Florence to the north, and everything in between.  Like me, many people aspire to travel and see the world. Just last month, I visited my homeland once again.

Cuba is an island that has been governed by communism since 1959. There are about 10 million Cubans in Cuba, and the number hasn’t changed due to number of people who escape the country in search of freedom each year. The island isn't just a place of poverty, hunger, and no human rights, it is mostly known for the famous Cohiba Cuban cigar, the Havana Club rum, amazing beaches, and really good baseball teams. It is a place where time has stood still since the 50’s with the same classic cars still roaming the streets and buildings that are now falling apart.

I was born in Havana, Cuba, the capital of the country. When I was 9 years old, I left the country with my mother and brother while leaving family members behind. Ever since we left, most of my family from Cuba has also left in search of a better life and are now spread around the world. The first time I visited Cuba was in 2003 when I was 13 years old and last month was my second visit.

My mother, my brother, and I were going to meet with my two cousins and aunt who were arriving a day earlier, coming from Rome, Italy. All six of us were going to spend the next 2 weeks in Cuba after a year kept apart by an ocean. We were also going to see other family members, old friends, and swim in Varadero’s beach.

Like us, every other Cuban passenger was taking as much clothes as they could to aid their families and friends in Cuba. Limited by the amount of weight their baggage could carry, almost everyone was wearing excessive amounts of clothes. A man was wearing 3 hats of different colors, others wore two or three jeans, my mother wore a sweater in the middle of summer and my brother and I both wore hats along with our heaviest clothes, cameras, and anything else we could take.

Our flight from Miami lasted only 30 minutes while our cousin’s flight lasted 14 hours including connection time in Madrid, Spain. We spent more time in Jose Marti International Airport in Havana, Cuba than the time we spent in Miami International Airport and flying to Cuba altogether. At first people couldn’t find their bags and later the long lines to be charged for the medicine and food bag each person is allowed to bring for their families. Each of us had money at hand in case we needed to bribe airport personnel because they could become difficult. In the end we finally escaped the worst without problems and met our aunt outside who was waiting for us with an old friend, who had a car, and she had hired him to drive us during the time we were going to be in Cuba.

Upon arriving at our old home, everything seemed small. I could not recognize the street where I grew up. As a child I remembered the houses and the building where I lived much bigger, and roads much wider. Now with three long steps I can cross to the other side of the street.

Over the next few days, we slept, along with my mother’s cousin and my uncle, who was staying over to spend time with my cousins, in a small apartment on the top floor of a 3 story building; what used to be our home in Cuba. It was no surprise to me how eight people could live in such a small home, but the fact is, before I even migrated to the United States, the six of us did live there along with my grandparents.  

Many old friends and family members came to visit us in the apartment and received the things we had brought them. We didn't bring items for entertainment, or jewelry, or for decorating; we brought shoes, clothing, medicine, money, etc; things that help people in need. More than 80 percent of our baggage was used to aid our family and friends.

Although Cuba is a place of poverty and necessity, more money is spent vacationing in Cuba than other places around the world. The Cuban government invented a currency for the country, apart from the real Cuban currency, that really has no value, it’s just paper, but they claim it’s worth more than a dollar or Euro and the government really uses it to steal real currency. Hundreds of thousands of Cubans spread around the world send money to their loved ones each year, the Cuban government exchanges it for their worthless CUC, and keeps the real currency. One so called CUC is worth 1.25 dollars, 0.61 Euros, or 20 Cuban pesos. Cuban citizens get poorer while the government gets richer and soon real currency won’t exist in the streets of Cuba.

During our stay we spent the first few days in Havana, visiting the city and spending time with family members and old friends. On the fifth day, we were dropped off at the bus terminal by Ardiel, our old friend, and Carlos, my second cousin’s friend who also owned a car. At the station we saw tourists as well as Cubans who were there to travel to cities all over Cuba, including where we were going; Varadero, Cuba.

The trip to Varadero reminded me that there is also true beauty in Cuba. Before exiting Havana, Cuba, I got a glimpse at various plazas and its monuments of Cuba’s long lost heroes from before 1959, El Morro (Havana’s lighthouse), and El Malecon (Havana’s breakwater). In the country side was able to see the country’s beautiful mountains, trees, and rivers. We also saw beautiful towns and cities, one being the city of Matanzas. Each town or city we passed by had its own special identity and one could remember each by the way they looked, the people, or lifestyle. Even Varadero was unique.

From the bus terminal in Varadero, we decided to walk 2 miles with our baggage to the house my aunt had rented for the week and stop to eat on our way there. That same afternoon after setting up our belongings, we went to the beach which was just 4 blocks away.

We went to the beach every day, swimming in the morning, returning to eat at the house, and returning to the beach at around 3pm, when the intensity of the sun had diminished, to bathe and see the sunset. On our first day at Varadero, I experienced the most incredible sunset I had ever seen in my entire life. We spent the nights listening to music and playing the traditional Cuban dominoes.

The beach was amazing. The sand was naturally thin and the water crystal clear. It was shallow for a considerable distance, the bottom was clean from rocks or seaweed far out to sea, there were little to no waves, sandbars lined up parallel to the shoreline, and no worries of sharks. We saw little fishes many times and a lot of sea stars.

Unlike Miami, which is all coasts, the beaches in Cuba are actual beaches. People don’t have to worry about sharks in Cuba’s beaches because since there are coral barriers, bigger fish don’t bother swimming inland when they know there is little or no food after the barrier. They also know they can be trapped and die off when the tide is low. Some people have stood on some of the island’s coral barriers during a low tide condition with the water up to their knees.

In the morning of our second day at the beach, my cousins, my brother, and I did as our mother used to do, and swam out as far as we could with the help of a pool float when the tide was calm. We went as far as we could to see if we could find anything interesting along the way at the bottom of the sea and bring it back to shore. The water was always crystal clear and Varadero is such an amazing beach that we didn’t see anything but plain sand, no matter how deep it got. When we became tired, we swam back to shore. I remember seeing around 12 feet deep at one point.

That same day we tried swimming as far out as possible, in the afternoon when we returned to the beach we began to find sea stars. My cousins, my brother, and I, started walking around in the water looking down to the bottom through the clear water, searching for sea stars. Every star we found we would bring back to the pool float, which was half filled with water, and took pictures with them. I had never seen so much sea stars in one place; we counted almost 50 sea stars that day.

The rest of our time in Varadero was much the same. We enjoyed the beautiful beach, the domino nights, and ate fish. The day before we left, we went to the coral barrier northern Cuba. My aunt and my mother talked to the person who takes tourists to the coral barrier in a small sailboat. They acted as if we were from Havana and not tourists, so that the guy would charge us less.

At coral barrier, my cousins, my brother, and I, swam in 20 feet deep water. There were corals at the bottom, a variety of fishes of different colors and sizes swimming around us, and even a 2 feet diameter orange cushion sea star. Among the fish we saw, there were blue tangs, baby billfish, and yellowtail snappers.

We travelled back to Havana in a van. On our way back, again I saw the beautiful country side, the different cities and towns, and stopped on Cuba’s highest bridge. El Puente de Bacunayagua or the bridge of Bacunayagua, crosses from the top of a mountain to the other. Looking to one side, the south, the landscape is filled with beautiful mountains, a plain filled with Cuban palms, and a river. Looking to the other side, the north, I could see in between both mountain ridges, the sea. There was rain coming from a single cloud over a small portion of the sea. The sight was amazing.

I remember, a few days before we left Cuba, we went to a famous place in Havana called El Coopelia, where people go to eat ice cream. They served us water before we ordered, but instead we drank from our bottles. Everyone looked at us weirdly and I wondered if they knew why we were drinking from the bottles.

Because the tap water in Cuba is contaminated, during the 2 weeks we spent in Cuba, we boiled water every day careful not to get sick, and then carried it in a bottle or two. Cubans are accustomed to drinking the contaminated water, but we who have been living outside the country are accustomed to cleaner water.

Leaving El Coopelia, we walked through Havana and took taxies back to our neighborhood, as we had done before since we had arrived in Cuba. We had found out that while stretching out our hands to signal for a taxi, depending on how we positioned our fingers, could tell a passing taxi driver to what part of the city we wanted to go. The taxi driver would then stop if he was willing to take us there. Almost everyone who is fortunate enough to have a car in Cuba uses it as a taxi to make a living.

Driving through the city one can imagine the hardship and see there is no future. Many qualified young people can’t study what they want; no one is allowed to have internet; keeping everyone apart from the outside world; there are less than 5 television channels with made up news, to make the country seem like the safest place in the world; and streets are filled with highly educated persons with low moral standards. Despite all the hardships, unlike the United States, everyone knows everyone in the neighborhood. Neighbors are friendly and always lend a hand, giving each other hope.

We left Cuba the following day. Like many other family members visiting, we felt helpless knowing that we can’t do much for our friends and relatives in the island. We left Cuba feeling sad, thinking that what we did wasn’t enough and that we could have done more to help our loved ones.

“Talent is a gift that brings with it an obligation to serve the world, and not ourselves, for it is not of our making.” Jose Marti

Tuesday, February 7, 2012

The Ingredients

For endless reasons, weather has always been a major issue in the aviation industry. It's hard to predict, it's hard to understand, it's continuously underestimated, and it constantly poses a threat to anybody. Whether you are on the ground or in the air, weather will be there and it will affect you. According to the National Weather Service (NWS), weather has been responsible for an average 543 deaths in the United States each year for the past 10 years; about half are aviation related.

Normally, teachings in flight schools about weather, go only as far as the basics. Pilots learn how to interpret charts, read the undecoded, and understand the theory to some extent. What many pilots don’t learn is the details of how the weather phenomenon forms and comes to be as it is. Knowing what specific factors or “ingredients” are needed for the formation of an affecting weather phenomenon, will not only help pilots have a greater understanding of the theory, but also to have a better overall picture and know what to expect.

Thunderstorms often present some of the most hazardous conditions. They are responsible for damaging hail, heavy rain, icing, tornadoes, lightning, and turbulence in many forms, including downbursts. Normally, there a 2 categories of thunderstorms: Air-Mass Thunderstorms and Severe Thunderstorms.

Air-mass thunderstorms are isolated thunderstorm cells showing little organization that form in a maritime tropical air mass (warm and moist air mass). They are the most common type of thunderstorm and usually form as a result of daytime surface heating in areas of very little to no vertical wind shear. Vertical wind shear is the change in speed and direction of wind with increasing altitude.

Severe thunderstorms are the strongest type of thunderstorm and form in areas of strong vertical wind shear. These are most commonly found along or ahead of cold fronts and often show more organization. Unlike air-mass thunderstorms, severe thunderstorms are longer lasting, sometimes forming as a result of contrasting air masses, can spawn tornadoes under the right conditions, and present more hazardous conditions to both aircrafts and people on the ground.

Seven various ingredients are needed in creating a severe thunderstorm; these are:

1.   Wind shear
The foundation of a severe thunderstorm is dependent upon wind shear. With vertical wind shear, wind speed increases abruptly and changes direction with height; this gives a severe thunderstorm a tilt that helps to fuel the storm thus increasing its life span. The tilt creates updraft (rising air) on a section of the thunderstorm and downdrafts (sinking air) on sections where precipitation occurs. The updrafts and downdrafts side-by-side work together to increase the life span, generate hail and sometimes create tornadoes. Tornadoes occur when horizontal and vertical wind shears near the surface work together to spin and tilt columns of air.

Air-mass thunderstorms, on the other hand, form with little to no wind shear and therefore have a tower-like shape with no tilt and no chances of tornadoes. Without wind shear, a thunderstorms would be classified as air-mass thunderstorms.

2.   Contrasting air masses
Tornado Alley is an area of the United States known for its amount of tornadoes each year. Severe thunderstorms in that area are very common. One of the reasons why severe thunderstorms occur at this location is due to 2 contrasting air masses that interact in that very region causing strong fronts. Strong fronts are ideal lifting mechanisms for the formation of powerful long-lasting thunderstorms. Due to the differences in moisture levels, dry lines form causing the most hostile conditions.

3.   Low level moisture
In Tornado Alley, warm, moist air coming from the Gulf of Mexico to the south, lower in the atmosphere, brings the high levels of moisture. Moisture is needed for the formation of storm clouds since it is one of the things that fuels thunderstorms. The higher the moisture levels, the more powerful a thunderstorm will become.

4.   Cold, dry air above
Cold, dry air from the northwest also comes to Tornado Alley. Cold air is essential for strengthening a thunderstorm. The colder the air above than the air below, the more unstable the conditions become due to a higher decrease in temperature with altitude and strength of the cold front’s lifting mechanism.

5.   Low level jet
Low level jets are also needed for the formation of wind shear. A low level jet is a rapidly moving stream of air at lower levels in the atmosphere. In Tornado Alley the low level jet brings the warm, humid air from the gulf that helps fuel the storm.

6.   Upper level jet
An upper level jet bringing the cold, dry air from the west at high speeds is also necessary. The jet stream is a continuous rapidly moving stream of air. Pressure differentials at the surface sometimes accelerate a section of the jet stream, called jet streaks; as a result, jet streaks curve and speed up. This is a sign of strong upper level divergence and low level convergence in the area of low pressure at the surface. This means more unstable conditions and increase updraft strength to form severe thunderstorms.

7.   Upper level trough
A trough is an elongated area of low pressure. When there is an upper level trough, strong upper level divergence exists upstream (east side in the northern hemisphere) of the trough, a factor that contributes to strengthening the lifting mechanisms of the surface low pressure center and the updraft strength in a severe thunderstorms. Usually, one can expect stormy weather upstream of an upper level trough. 

Now that you know the basics of the ingredients, I encourage you to do a little more research. There are actually 3 ways in which severe thunderstorms organize themselves: Squall Lines, Multicell Thunderstorm Complexes, and Supercell Thunderstorms. The most common severe thunderstorm is the Squall Line and the rarest is the Supercell Thunderstorm (most powerful).

"The more man meditates upon good thoughts, the better will be his world and the world at large." Confucious

Sunday, January 15, 2012

A Line Separating Life from Death

Armstrong’s line is named after Harry George Armstronga man who made significant contributions in the field of aviation medicine. At around 63,000 feet or 12 miles high, Armstrong’s line is a point in our atmosphere where water changes from the liquid state to the gaseous state at human body temperature (98.6˚F). Upon reaching such an altitude, things like tears, sweat, saliva, and any other water content in the body will boil causing a slow and painful deathincluding blood?

The reason water boils at this altitude is mainly due to atmospheric pressure. At higher altitudes there is lower pressure than at lower altitudes. Being in a lower pressure environment (higher in the atmosphere), less vapor pressure is needed to boil water; therefore a lower temperature is needed to boil water.

In case you are wondering, according to americasblood.org, plasma accounts for 55% of the blood in a human body and 90% of plasma is made up of water. So concluding that water makes up about 50% of a person's blood, it is true that the water content in the blood will boil. In addition to boiling, gas bubbles inside the bloodstream can at some point block blood flow in an artery causing the person to die of a heart attack.

Not to worry, because thanks to Mr. Armstrong, fighter pilots today have pressurized suits keeping them alive at such high altitudes. In addition, pilots continuously breathe on oxygen masks to compensate for the decrease in oxygen partial pressure. Without oxygen masks at 60,000 feet, exposed pilots would become incapacitated due to hypoxia in a matter of seconds.

There are some humans who have been close to 12 miles high without pressurized suits; one example is passengers in a Concorde.

“As a day well spent brings happy sleep, so life well used brings happy death.” Leonardo DaVinci