Category Archives: Aviation

Aircraft Turbulence


A reader of the blog (one of probably only two or three!) asked if I would talk a little bit about turbulence and what causes it. I know that turbulence is probably the single biggest fear of skittish fliers, so I want to dispel some myths and explain what is actually going on. Knowledge is power. Understanding brings peace. I’m almost never scared when I fly as a passenger because I know what’s going on and what caused that noise that scared so many other people. When you know and understand what is happing, in any situation, it makes things much less frightening.

When I hear people regaling stories of the terrible turbulence they experience and how they “fell almost a thousand feet,” I work hard to not allow my eyes to roll backward and have to bite my tongue until it bleeds. It never ceases to amaze me what people will say about some incident they had on board an airliner. If someone fell a thousand feet, they’d be dead. If you fell off your dining room chair, you probably break your tailbone, and that was just two feet! Without an altimeter, no one can tell how far they’ve fallen (or risen).

Turbulence, in it’s simplest form, is just shifting air. The air is the airplane’s version of a highway. If the air is moving up, the airplane will go up and if it’s moving down, the airplane will go down, just like a car traveling through the mountains. Now imagine that car traveling through the mountains at 500 miles per hour. That slow, gentle slope will be a big bump and toss you around the inside of the car. Small bumps in the air do the same thing to aircraft. A small ripple, at 500 m.p.h. gets magnified. If a large airliner drops just a few feet in a quick bump, that’s enough to send the flight attendants into the ceiling.

The important thing to remember is that even thought the aircraft is getting tossed all around in a lot of turbulence, it is still flying! I liken it to a canoe. The canoe may hit whitewater and get tossed all around because the river is changing directions and making foamy waves, but even so, the canoe is still floating! It is following the surface of the water and an aircraft is following the current in the sky. Unlike in the movies, unless an aircraft stalls (not caused by turbulence) it cannot fall out of the sky. If it’s nose pointed toward the ground and started accelerating toward the Earth, this would cause an increase in airflow over the wings, which causes more lift, which causes the nose to pitch up, which caused the aircraft to stabilize again. Aerodynamics keep the aircraft inherently stable, and when it gets disrupted, like “falling from the sky,” it tends to right itself on its own, by it own aerodynamic design.

Large airliners often have better glide ratios that even small Cessnas because of the design of their wings. At cruise altitude, even if an airliner’s engines fell off, it would be able to glide over 100 miles before hitting the ground, and in that amount of time, you can be sure the pilots have found an airport and are heading right for it. So, turbulence won’t cause the aircraft to fall from the sky because even through the bumps, it is still flying as it follows the ripples in the air. If airplanes flew by being suspended in the air by a chain, then yes, I’d be nervous too if we started bouncing around, as that will put a lot of strain on that chain. I wonder if we think of flying in the same way — dangling by a rope, so bumps may cause that rope to break. Unless the wings fall off, you are fine in bumps.

There are many things that cause turbulence, but five biggies are:
1) Thermal activity from the sun
2) Thunderstorms
3) Jetsream wind
4) Mechanical mountain waves and
5) Wake turbulence generated behind large aircraft.

The sun causes most of the turbulence you feel. The simple version is that it heats the surface of the Earth at differing levels. The hot asphalt parking lot creates a lot more heat than the cornfield next to it. The hot surface of the parking lot causes the column of air above it to rise more rapidly than the warm air above the corn field. These two columns of air are rising at differing speeds and so when an aircraft flies through those two columns, you feel a bump. The sun also causes the formation of thunderstorms. Now pilots don’t fly into them, as they can be destructive. However, even the air surrounding them can be very bumpy. Thunderstorms form with rising air and then falling air which will cause bumps both inside and outside the storm. Some days, it doesn’t matter what altitude you try or direction you fly, the air is just bumpy from storms. Think of the sun like the flame on a gas range. If you put a pot of water above that flame on the stove, it will boil. The heat causes the roiling of the atmosphere, in the same way the water roils and boils in the pan. The worst, most bumpy days occur on what we would call “a pretty, sunny afternoon.” When you see puffy white clouds in the sky, they are bumpy. The smooth days are usually in the winter (less heat for stirring up the sky) and rainy days, where there is no thunder. The atmosphere is at its most stable in a slow, steady rain, without thunder. Thunder means a thunderstorm, which is lots of turbulence, but when there is just a steady rain, the air is as smooth as glass.

The jetstream also causes bumps. They are high winds that encircle the globe and cause more problems in the winter than in the summer. In summer months, they recede up to more northerly latitudes, but in the winter, they drop down to lower ones, like through the middle of the U.S. They are jets of wind that can reach 200 m.p.h. and are like a cylinder of wind moving from West to East. At the core of the “tube of wind” the winds are strongest, and out toward the edge, the winds are less, like 50 m.p.h. Passing through these rapid changes will always make for a bumpy ride.

Mountain waves are where wind blows up the side of a mountain and continue to shoot up into the air. On the downwind side of mountains, there can be very serious bumps, where the wind spills over the peak and spirals down the other side. Don’t be there! When I used to fly from Ohio down to Florida, over the Smoky Mountain range, there was almost a predictable amount of turbulence as the mountains sent wind currents up to the flight levels and annoyed me as I tried to sip my hot coffee.

There is also wake turbulence. The lift created by the wings of a large aircraft cause the air to be stirred up behind it. When smaller jets fly behind bigger ones, air traffic control is always alerting the small guy to be cautious of wake turbulence. Air will spiral horizontally (like the curls of a phone cord) behind the wing tips of aircraft and they become larger as they recede from the aircraft, so they are cone shaped. A small business jet might fit inside the wake from a Boeing 757, and that will flip the jet over on it’s back, as the wings follow the spiraling air. Air traffic control is good about providing enough separation that this is as rare as winning the lottery and pilots are keen on that as well. However, when you start descending for an airport and you get a big jolt, it may be wake turbulence.

Above all else, remember that the pilots are not flying the aircraft you are riding on by remote control from some brew pub in their home town. Their lives are at the same risk as yours! They don’t want to die, either, and will do all they can to keep you safe because their life is on the line too. As a matter of fact, if an aircraft hits a mountain side, guess who dies first? The pilots! I remember one of my flights when I was getting ready to leave DFW for Columbus, Ohio and as a lady boarded, she asked if it was safe to fly with these thunderstorms all around. I assured her that we had onboard radar and would avoid the storms. She asked if I was absolutely sure it was safe. I chuckled and told her: “Look, I care a lot about you as a passenger, but I care even more about me, and I won’t go if I think it will kill me!” She laughed and the light came on in her mind as she said, “Yeah, I guess that makes sense.”

Have no fear of the bumps and remember that the aircraft, though bouncing around, is still just as happy as a clam, following the ripples in the air. The airplane is happy, so you can be too! Enjoy the bumps and think of them as the best roller coaster you’ll ever ride.

TobyLaura.com

Imax and Islands


In my not so long career flying the freighter version of Cathay Pacific’s 747, I’ve had the opportunity to carry around some very interesting cargo. Most of the time, we don’t know much about what we are carrying, as it is in huge containers on the main deck. We always know about the dangerous goods and hazardous materials that are on board and where they are located, but beyond that, if the loadmaster doesn’t tell us or we can’t see it, it’s hard to know what we are carrying. Sometimes I think that we may not want to know. All we really care about is the weight of the cargo and if there are hazardous materials we need to be made aware of. The loading agents make sure the weight is evenly distributed so our center of gravity, or C.G. is proper for safe flying.

Cathay has carried relief materials for poor nations from charitable organizations, they’ve carried olympic horses for the olympic games that were held in Hong Kong, I’ve personally carried five Lexus SUV’s, and tonight, as we fly from Toronto to Anchorage, we are carrying something special bound for Shanghai: an Imax screen and projector. The 50 foot (600 inch) screen is rolled up in a huge crate, over 50 feet long, and it is sitting on two smaller crates, that hold the special projector. All the ground crew were excited as they loaded it and got their pictures made with the large boxes. The nose of the aircraft was raised so that the long box holding the screen could be loaded.

I’m proud that the theater in Shanghai trusts us with their special, and no doubt, expensive cargo. Many people in Shanghai will be grateful for the package to arrive, because there aren’t many experiences that can match that of an exciting movie in an Imax theater. I remember as a kid, we would head over to the Fort Worth Museum of Science and Industry and watch movies at the OmniMax. The Omni theater is an Imax sized screen that is curved, so that the view emerses the viewer as you truly are surrounded! It’s like sitting inside the bottom of an egg shell and the shell is the screen. Imax theaters are flat screens, while Omnimax are curved. Either way, the experience is breathtaking, especially when watching a movie fit for that type of screen, like a Nasa flick of a Shuttle launch, or Super Speedway showing Indy car racing.

 On the fourth day of this trip, as I headed back to Anchorage from Hong Kong, we were able to fly the newest 747 in Cathay’s fleet, B-LIF, an extended range freighter. It’s an amazing peice of machinery and it was an amazing flight. The weather this July, in the North Pacific, was absolutely beautiful today. Normally, we cross the entire Northern Pacific and never see the water because of all the low clouds and rain or snow. Today, however, was much different — clear as a bell. Way out on the Alutian Islands, sits Earickson Airforce base, on little old Shemya Island. The runway there is almost as long as the island itself. We use that as an emergency place to land in case we have a fire or major mechanical problem. Today, as we passed nearby, we could see the runway and the small buildings there. The island is only about 5 square miles, and 99% of the time, the weather there is terrible: freezing cold, blowing rain, howling winds up to 50 m.p.h., with visibilities less than a mile with fog, and the like. It’s often not availble as an alternate landing site because the weather is just too poor. But today, it was clear skies and calm winds. I almost wanted to take her in there, just to see what it was like there on the 10 nice days it has a year. My captain said that there are guys who’ve been here 20 years and never have actually seen the island.

A few miles from Shemya, is the Attu Island. There is no airfield there but it is much larger and has towering mountains and beautiful grass and trees that line the slopes. Even in July, there was snow about half way down the mountain slopes. There was even a nice looking valley that lead to a peaceful beach shore and I’m sure today would have been the day to visit. I wonder about who first found these remote places out in the tryrannical North Pacific. Were they lost and just happy to find land and decided to stay? Were they marooned there and forced to stay? Why would anyone live in these remote places. No Home Depot, no neighbors (or if there are, you’d better hope you like them!), no real contact with the outside world, and dare I say: no internet? I know they don’t have any Imax theaters, for sure.

After thinking about all that, I’m glad to be up here in my safe, warm, 747 that is smoothly taking me toward civilization at 9 miles a minute. I’ll visit one of those islands if I absolutely have to, but otherwise, no thanks, I’ll just keep trucking on to Anchorage thank you very much.

TobyLaura.com

747 Walk around

My last trip took me through Chicago O’hare. It wasn’t my turn, but because I brought my camera along, I volunteered to do the walk around inspection. It was a beautiful morning and it gave me the chance to take a few photos of the majestic bird I get to fly. I had just landed her in Chicago, in from our flight from New York’s JFK, while the captain was going to be taking her up to Anchorage. It was a great trip for sure. Click on the photo for a link to a slideshow on our website, of photos I took on that walk around and flight to Anchorage.

TobyLaura.com

Liters vs. Gallons

A reader asked, “I heard Chinese and Russian air space uses the metric system while most other countries use the imperial system of measurement. Is it alot of trouble converting the different system of measurement? I remember a Air Canada 767 having to make an emergency landing due to running out of fuel from wrong metric conversion. That won’t happen with Cathay?” — Tomcat1

Two great questions that I wanted to answer in my blog, one at a time. The first issue deals with metric flight levels and the second issue deals with metric fuel volume. I’ll answer the fuel question below, and the flight level question is addressed in the previous blog entry here.

Fuel is always an important topic of conversation on the flight deck of today’s commercial airliners. We always want to have enough of that stuff out in the wings while we’re airborne. Fuel can be put onboard an aircraft in several different ways: By weight in pounds or in kilograms, or by Volume, in gallons, liters, or imperial gallons. Many regional airlines in the U.S. don’t have to worry much about this, as all fuel in the U.S. is sold by weight in pounds with the less important amount of gallons somewhere on the fuel receipt. Problems can arise at international carriers, where they visit countries that use different units of measurement. An example would be like one of my flights that starts out in the U.S. where gallons are used, and then travels to Hong Kong, where liters are used and kilos are on the receipt. Getting these figures backwards or messed up can lead to serious consequences.

To keep all this straight, we have a fuel order form that we fill out once we’ve decided how much fuel to put on. Both pilots check the fuel slip before we give it to the fueler. Cathay pilots always order fuel in kilos and the trained, approved aircraft fuelers know this. Once the fueler has put the required fuel on board, he takes the fuel slip we gave him and writes down how many gallons or liters he put on, by taking the reading off his truck.

This is a picture of an excerpt of our fuel slip and shows the math formula we use to double check the fueler’s job. If he fuels us in gallons, he writes the amount of gallons in the gallons section. If he fuels us with liters, he places those digits in the liters section. We multiply the amount of liters times the *specific gravity* of the fuel (fuel changes density depending on its temperature, so the fueler, who knows the specific gravity, gives us that number, something like 0.794) to get our uploaded amount in kilograms. If he used gallons, we first take that value and multiply by 3.785 to convert the gallons to liters, and then multiply by the specific gravity. We end up with the kilos we have in our tanks.

Both pilots check the math, and finally, we check the fuel gauge to see if it agrees with what we ordered. If the fuel slip math and the gauges agree, we are good to go. If the fueler put in wrong numbers or put the numbers on the wrong line, we’d catch the error by crosschecking our math numbers versus the numbers we are seeing on our fuel gauge.

In a famous accident in Gimli, Manitoba, Canada, Air Canada crashed a 767 onto a deserted runway because they got their fuel order wrong. They messed up the whole liters and gallons math. Normally, this would be no big deal, as their math error would be caught by crosschecking the fuel gauge. The trouble that day was that their fuel gauges were not working, and they were using a procedure where fuel was uploaded based on a previous known quantity. This is a perfectly acceptable method, but if it is used, the math better be right! You can read more about that accident here, and the amazing way the captain, a glider pilot as well, glided the aircraft to an injury free landing.

Another famous accident involving fuel, or the lack thereof, was an Air Transat Airbus A330. They developed a fuel leak and didn’t catch it in time and ended up also doing an amazing job to glide the aircraft down to a landing in the Azores. You can read more about that accident here.

We’ve learned from other carrier’s mistakes, and our procedures at Cathay help mitigate fuel problems caused by leaks because we check the fuel once an hour. The flight management computer, or FMC, gives us two readings on fuel: the amount we are calculated to have based on fuel burn, and the totalized amount from fuel sensors in the tanks. If the calculated value and the totalized value differ by a certain margin, we have procedures that help us figure out what the problem is, and how to solve it.

Ultimately, mistakes can and do happen because we are all human and machinery breaks down occasionally. Usually, mistakes come from carelessness or fatigue when running the numbers. Thankfully, fuel issues rarely occur and Cathay has made it a strong focal point to make sure we check and recheck our numbers when it comes to fuel.

TobyLaura.com

Metric flight levels

A reader asks, “I heard Chinese and Russian air space uses the metric system while most other countries use the imperial system of measurement. Is it alot of trouble converting the different system of measurement? I remember a Air Canada 767 having to make an emergency landing due to running out of fuel from wrong metric conversion. That won’t happen with Cathay?” — Tomcat1

Two great questions that I wanted to answer in my blog, one at a time. The first issue deals with metric flight levels and the second issue deals with metric fuel volume. I’ll answer the flight level question below, and the fuel question in the next blog entry here.

Most of the time, you and I hear the captain come over the P.A. and say that we will be cruising along at 37,000 feet. Because he told us a value in feet, it makes sense. This is because ICAO, or International Civil Aviation Organization, the world standard on aviation issues, has deemed that altitudes and flight levels will be measured in feet. There are some nations though, that use metric altitudes and flight levels and don’t follow ICAO rules and suggestions. CIS countries (former Soviet countries dissolved in 1991 that have names that end in “stan”, like Uzbekistan) and Russia and China assign altitudes in meters instead of feet. The captain on a flight traveling from Moscow to Beijing might say we that we will be traveling at 10,600 meters. Huh? How high is that?

As a side note, there are altitudes and there are flight levels. In North America, below 18,000 feet is called an altitude, and 18,000 feet and above is called a flight level.**

The issue then becomes, when transiting the airspace of a country that uses meters, there has to be a transition from feet to meters for our assigned altitude. This occurs all the time and happened on my last flight from Anchorage to Hong Kong, as we passed through Russian airspace. Before we crossed into Russian airspace, we were flying at 38,000 feet, or flight level 380 (three eight zero). The American controller asked us what our requested flight level was in meters and we told him 11,600 meters. He then passed that on to his Russian counterpart, and when we crossed into Russian airspace, the Russian controller told us to climb and maintain 11,600 meters. This metric altitude is equivalent to 38,100 feet, so we climbed 100 feet.

Often times, this transition is done outside of radar contact, meaning we are not on anyone’s radar scope. The onus is on us to make the proper correction so we don’t hit an oncoming aircraft going the other direction. To make sure this is done properly, we have a small chart that we always pull out, even though we know what it says, and it tells us the metric values and their equivalents in feet. Another nice little handy dandy thing in the 747 is a meters button on the instrument panel. When it is pressed, our digital altimeters show both feet and meters together, making this procedure a no brainer. However, we use the chart, even though we have a meters button, because we always set our altitude in feet, even in a metric environment. Why? Easy: The autopilot only takes inputs as feet, in 100 foot increments. In some situations, the metric equivalent could be right in between these 100 foot increments, at say 39,450 feet. If that is the case, do you set 39,400 or 39,500? So that every Cathay pilot is on the same page, we set the altitudes given us by the conversion chart, and keep meters selected on our altimeter to double check our altitude in meters. That way, the chart does the rounding for us and it’s even less of a no brainer.

The great thing about no brainers? They are hard to mess up, so the procedure is safe and effective. Now, has the other pilot, in his 747, screaming along at 600 knots, coming right toward us in the opposite direction, has he set his altimeter correctly? Ha ha! To protect for that, there’s TCAS.

TobyLaura.com

** A flight level is an altitude where altimeters are set to a standard barometric setting, 29.92 inches. In the U.S. and Canada, this is done at 18,000 feet and higher, so that below 18,000 is called an altitude and 18,000 feet and above is called a flight level. Other countries have different transition levels, where the pilots adjust to the standard setting (in Hong Kong, it’s 9,000 feet) but the principle is the same. Closer to the ground, we want our altimeters adjusted for local barometric pressure, as this can affect what the altimeter reads. With the local pressure put into the altimeter, the more accurate it is at telling us our height above the ground. Air traffic control lets us know what this baro pressure is. Up away from the ground, to help everyone to be separated by perfectly equal amounts of accurate airspace, we set a standard of 29.92, keeping everyone’s altimeter reading the same value, no matter what the local pressure is. Ground contact isn’t a factor, and altimeters give us an accurate reading, not above the ground, but a standard plane, at 29.92 inches of mercury. This allows tight vertical spacing of aircraft, because with everyone’s altimeter reading the same altitude above the same level plane, aircraft can safely fly more closely together.

Cathay Cargo: The Samaritan


Cathay Cargo made the news again with their help in partnering with Billy Graham’s son Franklin and Samaritan’s Purse to deliver donations from Charlotte, North Carolina to Chengdu, China. Cathay did the same thing last year with the same organizations to send aid to China after a terrible earthquake.

It’s great to see my employer helping out in giving aid to other nations and partnering with Faith-based organizations. Here is the article.

TobyLaura.com

Emergencies high over the Pacific


Have you ever wondered what would happen if you were a passenger on a long flight over the Pacific and something terrible happened? I know I have, and like most of us, we probably envision treading water for a long time, or sitting in a life raft because the water is too cold for survival. (In the North Pacific in the winter, the water is survivable for about four minutes without protection or a lifeboat.) Fortunately for today’s passengers and crew, this possibility is quite remote, thanks to many modern conveniences like excellent communication equipment, well designed and highly reliable aircraft engines, and safety procedures that are well thought out.

I can think of three major emergencies that we as pilots can plan and prepare for, that if the safety procedures are followed, are completely survivable, even when there are thousands of miles of ocean below the airplane.

These are: Fire, Engine Failure, and Cabin Depressurization.

There are many other things that could go wrong, but they are not as severe as these three biggies. Bigger than these, like the wings falling off, either usually don’t happen or aren’t survivable anyway, so why plan for or worry about them?

An onboard fire is probably the worst of the big three because it can quickly escalate from harmless to deadly in just a few minutes. Recall all those warnings about tampering with the smoke detectors that you hear prior to departure? Yeah, those are deadly serious — no pun intended. The cargo compartments will seal themselves shut in the event of a cargo compartment fire to starve it of oxygen and fire suppression systems like Halon extinguishers take care of the rest of the fire. The cabin is a bigger problem because unless the fire is in a galley or lavatory trash can, it requires people like flight attendants to fight it. There have been several major fire disasters because the cabin caught on fire, like this Air Canada DC-9 and this South African 747 Combi (A combi 747 is one where the back half of the plane is cargo, and the front half is set up to carry passengers.) I’m sure that the lack of passenger smoking on planes has saved many lives.

But what about the cargo planes, like the one I fly? The cargo section of the main deck of the 747 is cavernous and there is no way to have enough Halon to put out a fire on that type of scale. But surely we have a way to fight it while it’s three a.m. over the Pacific or Himalayas, right? The answer is yes, and it’s actually a better system than in the passenger versions of the 747. Because we don’t have to worry about keeping 400 people alive down below us, we depressurize the entire airplane while wearing oxygen masks, to starve the fire of oxygen. When we get a fire warning, we put on our oxygen masks and raise the cabin altitude to 25,000 feet, where there isn’t enough air to burn an open flame. Once the fire is out, we lower the cabin back down to five or six thousand feet and take off our masks. It’s a simple system that should prove to be very effective, however, I hope I never need to test it.

Along those same lines, another major problem that we can deal with effectively is cabin depressurization. If our plane can’t maintain pressurization, then we can’t maintain consciousness and everyone goes to their final sleep. Contrary to what some believe, aircraft don’t carry large tanks of oxygen to allow people to breathe, they simply pack air into the cabin to provide pressure similar to sea-level pressure. See, the ratio of oxygen in the air, 21% is the same at sea-level as it is at 40,000 feet, there just isn’t enough pressure in the atmosphere to breathe it in at high altitudes. Aircraft don’t have to constantly supply oxygen, it is already there at 21%, they just have to make the pressure available for us to be able to breathe. They do that by taking high pressure air off the engines and sending it into the cabin. The cabin’s “altitude” is controlled by how much of that pressurized air we let out, with a special valve called an outflow valve. As the valve opens, the pressure in the cabin lowers, and as the valve closes, the pressure gets greater inside the cabin. At high altitudes, we need lots of pressure to maintain breathable air, so at cruise, the valve is mostly closed.

When that system fails, or a hole gets blown into the side of the cabin, we lose all our pressure. The masks drop and provide air for a little while, but only for a few minutes at high altitude. We have to descend down to more breathable air, but doing that increases our fuel burn dramatically. On our Cathay 747’s, we first descend to 14,000 feet, until all the oxygen in the masks are depleted, and then we descend to 10,000 feet, where everyone can breath normally. Our fuel burn will be around 50% more down at 10,000 feet, so if we are out over the Pacific, our destination is off the table. We will have to go to an en-route alternate, decided upon by using our point of no return, or PNR, described in the last blog here. Again, we always have to have enough fuel when we depart, to have a depressurization at any point along our route, and still be able to reach a suitable alternate.

And finally, there is the little matter of engine failure. Do any nervous flyers ever worry about that? I didn’t think so :o) No, it seems everyone’s fear is engine failure, especially when traveling over such huge expanses of water. The good thing about the 747 is that it comes with four engines, so there is little chance of major trouble. But even superb aircraft like the 777 that only has two engines doesn’t cause much concern for alarm as engine failure is so remote. These engines are not like a car’s engine. They are millions of dollars worth of precision, and because they rotate, there are very few parts that wear like engine parts wear, and their maintenance is much improved over the maintenance you and I give our cars, for sure!

However, with that said, failures do occur, and when they do, pilots need to be ready for them. Much like the last blog entry described about PNR’s here, we have a three engine PNR, where if one fails prior to a certain point, we know we’ll need to return to a certain airfield, and if it fails beyond that point of no return, we will be able to continue to another airfield. This is because we now may not have the fuel to continue to our destination.

Why? Because we actually burn more fuel with three engines than with four. It sounds counter intuitive, but think of it like this: When we go from four to three engines operating, we now have less thrust. Less thrust means we can’t maintain the same altitude, and have to descend a few thousand feet. This is because the higher we fly, the more thrust it takes to keep all that weight up in the sky and when we lose some of that thrust, we start to slow down. If we lost an engine and didn’t descend, we would slow down beyond the speed at which our wing would be able to maintain lift, and we would stall — where the wing can’t produce enough lift for the weight it is having to carry. The trouble is, when we do descend, we burn more fuel and that is why losing an engine will actually cause fuel troubles. Also, I believe the synergy affect applies here, too. The thrust from four engines is better and more efficient than the increased thrust of three, making up for the lost engine, if the aircraft maintains the same weight and altitude.

So, I write this to give you a little bit of insight into what we plan for in the 747 as we get ready to cross large expanses of inhospitable terrain, either mountains or oceans. When crossing the United States, there are so many airports to duck into if trouble pops up that there isn’t much planning to do. But when there are vast distances between places of refuge, proper planning is essential. Never fear, as even with the three biggest troubles that can occur, there is always enough fuel to get to a suitable landing field, because if there wasn’t, we wouldn’t be taking off in the first place. Cathay doesn’t pay me enough to take that type of risk!

TobyLaura.com