What's Up with the Rollercoaster Takeoffs from Orange County?

If you've ever had the pleasure (or perhaps the terror) of taking off in a commercial plane from Orange County's John Wayne airport, you'll know that it is a takeoff unlike any other. Just seconds after liftoff, you will feel your stomach drop as the airplane does a very abrupt pushover. This pushover, similar to what you might feel on a rollercoaster or perhaps a hilly backcountry road, will make you light in your seat. You might even feel yourself being restrained by your seatbelt.

The next thing that you will notice is that the sounds in the cabin will change. Specifically, they will get much quieter. The roar of the engines that accompanies all takeoffs will diminish dramatically. You will sense that the nose of the aircraft has dropped significantly. The incline, or what pilots call the "deck angle" will have gone from the usually steep angle used for most takeoffs, to one that is barely distinguishable from level flight. And all this will seem to be happening much too close to the ground.

Finally, you may become aware of an annoying thumping that you feel in your chest. Don't worry, that's only your heart pounding.

You may think that this is it...game over...and wonder if there's enough time to squeeze a goodbye text to your loved ones before plunging into the Pacific ocean. But you should rest easy. You are not going to die (at least not today). What you have just experienced is known as a noise abatement takeoff. They occur hundreds of times weekly at John Wayne and are an FAA approved and in fact government mandated maneuver. That's right; pilots and airlines will be fined if they don't perform this type of takeoff.

So why, you may ask, are you being subjected to an experience that should probably be featured at the nearby Disney theme park? Well, as I mentioned above, noise. Noise and of course politics. For John Wayne airport is the only airport which mandates such a drastic noise reduction profile. And as legend has it, the Duke himself, the airport's namesake, had a hand in getting those restrictions put in place.

The departure path from John Wayne airport flies almost directly over Newport Beach. And as you may know, Newport Beach is a very well-heeled community. And while I'm not going to make judgements on wealth accumulation, one thing wealthy people are good at is getting things done. Starting with the arrival of the first turboprops and jets in the 1970s, community activism followed soon thereafter. Eventually lawsuits were filed and the restrictions were put in place.

Why Orange County?

John Wayne Airport dates back to 1923 when a landing strip was first opened by a man named Eddie Martin to host a flying school. Then known as Martin Field, Orange County assumed ownership in 1939 with the airport becoming to be known as Orange County Airport. The name was changed to John Wayne Airport in 1979 in honor of actor John Wayne, a nearby resident, upon his death.

Noise restrictions at the airport date back to 1985 when a local group representing residents who lived under the departure path sued the county. The resulting settlement implemented noise regulations and curfew requirements which remain in force today. Noise meters are deployed along the departure path to measure the sound footprint of each departing aircraft. Those restrictions are unique in being some of the first of their kind, and also just about the only of their kind.

In 1990, Congress, fearing that many localities could eventually hamstring the growth of aviation by implementing their own patchwork of noise restrictions, passed the Airport Noise and Capacity Act which outlawed curfews at airports. John Wayne was grandfathered in, however, due to the original lawsuit being filed in 1985.

Why the Rollercoaster?

So knowing why airplanes have to fly quietly, you may be wondering about the "how". And specifically, you might be wondering why airliners don't just use less thrust from the get-go instead of the roar followed by the pushover and silence. Without getting too technical about takeoff performance, much of it comes down to the runway length at John Wayne airport, or to be more specific, the lack of runway length.

The longest runway at John Wayne is less than 6000 feet long. At a scant 5701 feet to be precise, it is one of the shortest runways if not the shortest runway in the nation from which large commercial aircraft fly.

It is the nature of gaining flying airspeed in a very short distance which necessitates the full power takeoff. Once airborne, but before the flaps are retracted, the aircraft reaches a "cutback" altitude of about 800 ft. It is here where the engines are throttled back either manually or by the auto-throttles to a thrust which meets the minimum required climb gradient of about 2.5%. Less thrust also means a shallower climb angle, hence the pushover.

Once beyond the noise sensitive area, or about six miles after takeoff, the aircraft resumes its normal climb profile using full climb thrust.

Is It Dangerous?

I suppose that depends on your definition of the word dangerous. Any time you monkey around with large power changes on a turbine engine, you increase the odds of something going wrong. In fact, many engine failures occur not on initial thrust application such as takeoff, but rather on a large thrust reduction. That said, the odds of that ever happening are infinitesimal. Still, it isn't unknown for engines to fail as was dramatically illustrated by the uncontained engine failure on a Southwest Airlines 737 several weeks ago. Infinitesimal odds, but not zero.

So no, it isn't dangerous in the conventional sense of the word. Avoiding flights out of Orange County to avoid takeoffs using this procedure would be silly. And likely more dangerous as a longer commute up the freeway to LAX would definitely expose you to more absolute danger in your car. Of course, the safest course of action is to hide under the bed which still won't protect you from meteorites...or dust bunnies.

So when you do get on that airplane leaving the OC, be sure to get a window seat on the left side of the airplane which gives the best views of Catalina, relax and enjoy the ride. But don't put your arms in the air and scream as if on a real rollercoaster. People will stare.

Flying to Cuba on One Engine

Brian Hall (center) and his Bonanza in Havana

This past August saw an important landmark in aviation history with the first scheduled commercial flight between the US and Cuba taking place in nearly fifty years. On August 31st, a JetBlue Airbus flew from Ft Lauderdale to Santa Clara, Cuba with 150 passengers, journalists, and dignitaries. JetBlue is one of six US airlines which won approval to fly direct routes from the US to Cuba.

As historic as that occasion was, an equally historic flight took place earlier in 2015. Scooping the first scheduled commercial flight by over a year, was the first flight of a private civilian aircraft to Cuba from the US. On January 15 of last year former Air Force C-130 pilot and businessman Brian Hall flew his Beech Bonanza from Fort Myers, Florida to Havana. Flying under the rules of Part 91, Hall's flight was the first flight of this type in over fifty years.

Hall is hoping to start a new ferry service called CubaKat between Florida and Cuba. He flew to Havana to discuss business details with his Cuban employees and government officials. He might be considered a serial entrepreneur as he is currently the CEO of a marine engineering company and has had a hand in starting or running everything from ferry services to an airline to an energy services company and consultant services.

While travel to Cuba for tourism is still not permitted under current rules, other reasons for travel such as cultural exchange are permitted. In addition to his proposed ferry service, Hall also spoke to Cuban officials during his visit about starting airline service between cities in Cuba itself. There is apparently a need for intra-island air transportation and Hall seems to be in the right place at the right time to capitalize on business opportunities in Cuba. He is proposing to start service using Cessna Caravans to deliver passengers and cargo.

Well as it turns out, Hall was a student pilot in my flight at the 98th Flying Training Squadron at Williams AFB in Phoenix, Az, nearly thirty years ago. The 98th trained students to fly the T-37 primary jet trainer while on their way to become Air Force pilots. After graduation from undergraduate pilot training, Hall went on to pilot C-130 Hurricane Hunter aircraft before leaving the service to start his career as a businessman.

The Road to Cuba

I was able to catch up with him about a week ago and ask him how his path led him to make history flying a single engine aircraft to Cuba.

He told me that his fascination with Cuba came from his grandparents who had often vacationed on the island. They would tell stories of their travels which captivated him. Many years later, he was able to arrange a retreat to Cuba for some family members and from that point on was hooked. He has since been back to Cuba many times on cultural exchange trips, though always having to travel by chartered aircraft.

In December of 2014, President Obama announced a restoration of full relations with Cuba thus ending decades of stalemate and embargo with the island nation. Hall knew that this was his opportunity to get in on the ground floor with the establishment of ferry service between Cuba and Florida. His CubaKat venture, which will use large catamaran ferries carrying up to 200 passengers, is still awaiting final government approval to begin operations.

In the meantime, Hall saw an opportunity to make a historical flight. He actually owns two aircraft, a single engine Bonanza and a twin engine Baron. And while the general rule for overwater flying is that more engines are better, Hall said he had insurance problems with taking the Baron to Cuba. As a result, he had to take his single engine 1953 Bonanza for the 217 mile journey to Havana.

While many pilots fly single engine aircraft to the Caribbean islands, Hall said that the one concession he made was to wear his life vest rather than to just have it available. The last thing a pilot wants to be doing if forced to ditch in a small aircraft, is to simultaneously fly the plane and make a distress call while figuring out how to don a life vest.

While planning for his flight, he did contact the US Immigration and Customs service who for some bureaucratic reason or another informed him that he couldn't make the flight as he had planned. It had something to do with Miami being the only approved airport for flights from Cuba. Being steeped in the culture of entrepreneurial risk taking, he found that it was in fact easier to beg forgiveness than to ask permission and had no trouble upon his return to the states.

Lacking the Basics

Hall told me that the actual mechanics of flying to Cuba were rather routine. The Cuban controllers were all perfectly gracious, spoke good English and his flight to Havana was uneventful. It was upon arrival that he realized that Cuba has a ways to go as far as aviation infrastructure is concerned. Routine expectations such as tie-downs and chocks, available at most US airports, were notably lacking. They also didn't have fuel, which might have been a problem had he not had the foresight to carry enough fuel for a round trip.

Since his first trip, Hall has been back to Cuba in his own plane three times. He says that the lack of overall infrastructure to handle the tsunami of Americans expecting to visit the island will be a brake on the tourism industry once the tourism ban is eventually lifted. Hall told me that one of his employees requested that he bring a toilet seat along on his next visit. It took two visits as the first one he brought was oval when a circular one was required.

Hall also mentioned that travellers to Cuba should not forget to bring enough cash to cover their expenses while visiting as there are almost no ATMs on the island. The Cubans, for their part, seem to be catching on that there is money coming along with their new island visitors. On one of his latest trips, a new $40 departure tax was levied which hadn't been mentioned or collected before. Of course you must pay if you wish to take off.

Cuba is His Passion

Even though the regulatory hurdles Hall faces to get his CubaKat venture going can be a real headache, he doesn't plan on quitting the island anytime soon. He's there to stay in one fashion or another. His motto is that if a businessman isn't earning, then he's learning. And Brian Hall, Air Force pilot turned entrepreneur turned Cuba evangelist seems to have enough passion and energy to do plenty of both.

Is Aviation Automation Killing Us?

"When we design our systems, we need to assign appropriate roles to the human and technological components. It is best for humans to be the doers and technology to be the monitors, providing decision aids and safeguards."

 - Captain Sully Sullenberger

The past week has seen several high profile aviation incidents come to light. The first one was a preliminary accident report on the crash and fire which destroyed an Emirates Boeing 777 in Dubai last August. The second was the release of the final report by the Australian Transport Safety Bureau (ATSB) regarding an AirAsia Airbus A330-300 enroute from Sydney to Malaysia last year which suffered navigation and other system failures as the result of erroneous input by the pilots during preflight.

The Emirates crash tragically took the life of a responding fireman, while the AirAsia incident caused no injuries but did result in a diversion. Each incident had the potential for great loss of life, though. The improper use of automation can be implicated in both the Emirates and AirAsia events. Let's take a look at each of these and see if we can draw some parallels.

Emirates 521

The crash report on the Emirates flight, released by the General Civil Aviation Authority (GCAA) of the UAE details that the approach was flown by the captain. The autopilot was disconnected for the landing while the autothrottles remained engaged. The aircraft experienced a longitudinal wind component which changed from a headwind of 8 kts to a tailwind of 16 kts during the approach. As a result of the decreasing performance wind shift, the aircraft made a long touchdown.

An automatic system on the Boeing warned the crew about the long touchdown, and a decision was made to go around. So far so good. Going around rather than accepting a long landing due to shifting winds is the correct decision.

What happened next wasn't so good. The nose was raised, the flaps were reset and the gear were retracted, but go-around power was not added until three seconds before the aircraft impacted the runway with the gear partially retracted. The post crash fire destroyed the aircraft entirely.

Adding power during a go-around is...or should be, instinctual. It's considered aviation 101, or rather it used to be. Today's highly automated aircraft, however, all employ autothrottles which automatically advance themselves when the "Takeoff-go-around" or TOGA button is pushed. This is how go-arounds are performed on automated aircraft.

The 777, however, has a feature which disables the TOGA button after touchdown. This makes sense as you don't want the throttles to advance after landing in case of accidentally touching the TOGA button. After a normal landing, that is. There are times when a rejected landing, or go-around, occurs after touchdown. The reasons vary, but a landing can be rejected any time until the thrust reversers are deployed, even after the gear touch down.

This is what happened to the Emirates 777. It touched down, and then attempted a go-around without adding power. Questions remain as to whether or not the captain actually engaged the TOGA button but in any case, the captain should have manually pushed up the throttles for the go-around or ensured that the autothrottles automatically advanced.

Why would he not do that? Easy. It's called negative conditioning or negative training. Go-arounds are routinely practiced in all airline simulator training programs, but go-arounds after touchdown are practiced much less frequently. Over time, muscle memory will expect the autothrottles to advance themselves during a normal go-around as they always do.

Put a pilot in a highly dynamic situation such as a windshear landing, and then perhaps throw in a non-routine distraction such as the automatic runway length warning, and voila, muscle memory takes over and the throttles don't get pushed up. Automation, which is supposed to make flying easier and safer, might have helped make a crash such as this inevitable.

AirAsia X 223

On March 15 last year, an AirAsia A330 suffered multiple inflight malfunctions of  its navigational display systems rendering the aircraft incapable of either continuing to its destination in Malaysia, nor of returning to its origination point of Sydney due to low ceilings. The aircraft eventually landed uneventfully in Melbourne, which had clear weather.

Subsequent investigation revealed that the pilots made a data entry error during their pre-flight checks consisting of a single digit error in programming the aircraft's location.

Modern navigation systems on today's commercial aircraft are capable of guiding an airplane to a spot on the other side of the globe with accuracy down to several feet. But in order to know where to go, the computers on the airplane first have to know where they are. 

Part of the preflight process is to enter in the aircraft's current location in the form of a latitude and longitude. The pilot entering this data made some sort of fat finger error which resulted in the actually entered position being thousands of miles away from the Sydney airport. So after the aircraft departed, discrepancies between where it actually was and where it believed it was caused the computers to crash resulting in a nearly complete failure of the navigational system.

After identifying  and while attempting to fix the problems with the navigation systems, the crew compounded their problem by cycling two of their three flight computers to off and back on. This incorrect procedure resulted in the loss of other primary flight displays and rendered the aircraft incapable of flying even a simple approach back to Sydney necessitating the diversion to Melbourne.

Even after arrival at Melbourne, the aircraft had to make several attempts at a completely manual landing without the benefit of either the autopilot nor autothrottles. There is little doubt that flying a highly automated aircraft left the pilot's manual flying skills in a somewhat rusty state, which is completely expected.

Automation: Friend or Foe?

Automation of commercial airliners is with us to stay. It provides many benefits and economies but there are problems with its deployment which contributes to accidents and incidents such as these. The old aphorism which states that computers just allow humans to make mistakes faster and with more efficiency certainly applies here. 

Over reliance on automation is also well known to cause a deterioration in manual stick and rudder piloting skills, which go unmissed until they are needed. The crash of Asiana 214 in San Francisco several years ago was a perfect example of this.

But as Captain Sully warned in the quote above, automation is best deployed as an enhanced decision making tool, not something which a bored human being should be tasked to sit and watch, as it is today.

How I Raised Four Amazing Children as the Husband of an Airline Pilot

I, no we, my wife and I, have four amazing kids. No, seriously, they are. I couldn't possibly be biased, but I'll let you judge:

Marlon, the oldest, (not their real names) recently graduated as an officer from one of the service academies where he was a collegiate swimmer, and is now in training with a special forces unit. He was offered a pilot training slot but turned it down to go into special forces (a subject for a future post).

Bronwyn has recently returned from a two year dance school in Canada and is embarking upon her career as a professional modern/jazz dancer. Genevieve, my third, is also a cadet at a US service academy and in her sophomore year studying operations research, while Poppet, my youngest, is a high school senior sorting out her options. She is finding out that being a National Merit Scholar semifinalist means a mailbox full of Ivy League promotions on a daily basis.

So they're awesome kids, and what's more is they're really nice people, which in my book counts for more than their accomplishments.

But I am not going to be shy about taking at least some of the credit here because my wife, their mother, abandoned the family. At least weekly. Oh, she would always eventually come home only to fly out the door in a week or so leaving me alone with an infant and three toddlers for days on end.

She's not a bad person either, but she is an airline pilot. Part of her job description is to be gone. And she wasn't only gone for her three to four trips a month, but for many weeks of time every time her airline decided to send her to train on a new aircraft.

I've Got the T-Shirt

Short of actually giving birth to these children, there wasn't a single child rearing function that I was not required to master. They're 15,16 and 19 months apart so for a short while we had four in diapers. Did you know that a running clothes dryer can calm a crying baby in seconds? No, not in it, but rather on it where the changing table was. And I bet you didn't know that a bungee cord stretched from a bedroom door across the hall to the bathroom door is an excellent means to corral a toddler who won't stay in bed.

When giving baths, be sure to buy the cheapest conditioner available and then use about half the bottle per child per bath to ease the brushing of hair tangles. Learning how to apply drywall texture can also be a useful skill you will need to repair downstairs water damage from bath time. And doubling the recipe for hamburger helper, otherwise known as "Daddy goulash", leaves enough food to put in their thermos for a tasty and nutritious school lunch the next day!

Now I know that many of the stay at home dads and all of the moms reading this are thinking "So what? You're not doing anything that I haven't done." And you would be right. But to give credit where due, remember no one applauds the dancing bear for dancing well, but rather for being able to dance at all! The kids turned out OK, so I figure we must've done something right. What exactly that was, I have no idea, but there are a few clues. Here are my best guesses.

Full Disclosure

For full disclosure, I am also an airline pilot. My wife, Sandy, and I were both Air Force pilots which is where we met. Sandy flew transport aircraft in Desert Storm and left the military shortly afterward to start her airline career. She has flown numerous aircraft over a 20+ year career to include the 747 and is currently flying the 777 on international routes.

I have also been flying commercially for about 26 years, but after leaving active duty, I found a job in the Air Force Reserve. As a "weekend warrior", I flew the C-5 jumbo transport concurrently with my airline job until retiring from the military in 2002.

Can You Juggle?

The nature of being an airline pilot (or flight attendant) means that you can't bring work home. Once you park the jet and set the brake, you're free. This means that while you are home, you are one hundred percent home. There are no business calls to take, emails to answer or projects due on Monday.

Over the years, I've met quite a few "industry couples" trying to raise a family. The entry of women into the piloting ranks as well as men into the flight attendant ranks means that more "assortative mating" is occurring. This is a fancy way of saying that there are more pilot-pilot couples and flight attendant-flight attendant couples.

Each couple has to decide for themselves how they are going to structure their family life. Sometimes this involves one person giving up their career to be a full time parent while the other becomes the sole breadwinner. Where both parents keep working, as we did, an important decision has to be made. Will they both be gone at the same time or will they fly opposite schedules?

Both of these options have their advantages and disadvantages. We tried both and then settled on flying opposite schedules. We figure that after almost 30 years of marriage, we probably have maybe 10 years of time actually spent together. (We may have accidentally stumbled on another secret of a long and happy marriage!)

As far as the couples who choose to be away at the same time, both parents being away simultaneously can be made much easier with the help of a grandparent or other adult family member willing to help out. Many couples make these sorts of arrangements.

Who's This Person with Our Children?

For others who wish to fly the same schedule, but without the benefit nearby family, hiring a nanny is required. This is how we started. We found a lovely older woman through an agency and made arrangements for her to live in while we were both away. When Barb, our nanny, started, we had two children aged 7 and 22 months.

We quickly found out that we were profoundly uncomfortable with the arrangement. Barb was loving and warm, but we simply realized that we just didn't know her that well. I think we both came to this conclusion one night when talking on the phone while we were both on a trip. Sandy was in Medford, Oregon and I was in perhaps St Louis. We never had any reason to believe that Barb wouldn't take good care of our children, but we still wondered whether she would get up in the night to comfort a crying baby. And that was that.

We learned that we were expecting again soon afterwards. Two babies later and after Sandy returned to work, we started flying opposite schedules and haven't looked back. It's not quite as harsh as it sounds though. We'd typically fly perhaps three trips passing in the night and then enjoy a week off together. Airline schedules can be flexible and we had the ability to occasionally give away trips for some time off.

 Effectively Single Parent

So we ended up raising our kids as serial single parents. I can't be certain, but I think the kids learned some independence from this arrangement. Each of us had our own parenting style to which the kids had to adapt. But unlike real single parents, the parent who happened to be home at the time was, as I mentioned, completely available and involved. In a sense, the kids were the only full time residents in our house with Mom and Dad coming and going.

As the kids got older, they had to by necessity take more responsibility for their own activities. Telling Dad for instance that a form was due with a check for some activity did little good if when by the night before it was due, Dad was away and Mom was the parent on duty. I have little doubt as well that the kids used our part time status against us in ways we can only imagine.

As technology bridged the physical communications gap, keeping the travelling parent in touch with family life became much easier. In the days before cell phones we paid for our own personal "800" number which would ring at the house. Later on we used cell phones to call home, but now we mostly use video links such as Facetime or Skype. We would occasionally sit in on family meals and homework time as a disembodied head on the iPad, even from overseas.

We even took a stab at homeschooling for a few years after becoming disenchanted with our local schools. I could write pages on that experience alone, but I'll just say it was hectic, tiring and totally worth the effort. We eventually moved and put the kids back in public school.

High Expectations and Priorities

One thing we never lost sight of in the chaos of a dual airline career was the importance of family priorities. We always had sit down dinners at a set time and tightly controlled TV time. I think that children need guardrails and routines. Even though my wife and I would run the house somewhat differently, the kids knew that our priorities were the same.

Being kids of airline employees, our children have become adept at navigating air travel and have travelled extensively by themselves, even to overseas destinations. When it came time to look for colleges, we told our kids that we were in for half the cost and that we'd buy a car for whoever got a free ride through scholarships. I may end up buying three cars.

So that's it. When we started this journey, we had no contact with other parents who had done this and we more or less made it up as we went along. It worked out but I think our key to success was to keep focused on the important things.

 

So How Do Jet Engines Work and Why Would One Blow Up?

This past week a Southwest Airlines 737 suffered a very dramatic engine failure while on a flight from New Orleans to Orlando. It appeared as if the entire front of the engine came off judging from pictures taken from inside the cabin. The aircraft also suffered a rapid decompression which was most likely due to debris from the engine striking and puncturing a hole in the fuselage. Considering that the time of useful consciousness (TUC) at 31,000 feet is only one to two minutes, the crew did an outstanding job of prioritizing their emergency action responses and safely recovering the aircraft into Pensacola.

On September 8th last year a British Airways 777 aborted its takeoff from Las Vegas after its left engine failed and burst into flames. The entire left side of the aircraft was engulfed in flames by the time emergency responders were able to put the fire out. Again, thankfully, no one was injured. The aircraft was later repaired and returned to service.

So in these two high profile incidents, jet engine failures caused very dramatic and potentially life threatening damage to commercial airline flights. But how do jet engines work in the first place and what would make one blow up? Is there any way to make engines safer or are these types of mechanical failures just something with which we'll have to learn to live?

Suck Squeeze Bang Blow

Modern turbine aircraft engines are simultaneously simple in operation, yet highly complex precision machines. Their operation, which can be simplified into the title of this paragraph, consists of four elements. Air is first drawn into the front of the engine and is next compressed by a series of blades rotating on a center spool. 

This compressed air is then combined with fuel sprayed into the combustion chamber and ignited. The resulting flow of hot expanding gas flows over turbine blades also connected to the center spool and then exits at high speed providing thrust. The turbine blades provide power for the compressor blades and the process repeats.

The earliest jet engines were known as "pure turbine" engines where all the air from the inlet went through the hot section. Since then, large fans have been employed where only some of the air goes into the hot section but most of the thrust is created by the fan and bypassed around the core of the engine. High bypass engines are now the standard on airliners though pure turbines are still used on military aircraft.

And that's it. Conceptually quite simple and very few moving parts. 

What Could Go Wrong?

The truth is that because jet engines have so few moving parts in comparison to other types of engines, there is very little actually to go wrong. The problem is that when things on a jet engine do go south, they can make a big mess as seen in the two above mentioned incidents.

As far as the central operation of the compressor-turbine assembly is concerned, metal fatigue and subsequent failure are the primary culprits. Investigation of the BA 777 incident revealed that the spool in the high pressure section of the compressor had failed and parts of the compressor spool and blades were subsequently thrown through the engine case and cowling.

A similar metal failure was implicated in the crash of United 232 back in 1989 which claimed 111 lives. Thankfully, advanced metallurgy and inspection technologies make these types of problems quite rare.

The speculation of what caused the failure of the Southwest Airlines engine ranges from mechanical failure of the fasteners which keep the structure attached to possible failures of the engine anti-icing system which is located in that area. An NTSB investigation is ongoing,

Simple and Yet Complex

While the operating principles of jet engines are simple, many of the technologies used to make them work are quite complex. The metallurgy used in building the fan and compressor blades is state of the art. These structures are mostly made of titanium which while being extremely strong and flexible is notoriously difficult to cast. Titanium castings are required to be forged in a vacuum as any air can induce impurities resulting in cracks in the metal. Newer technology engines now use composite materials in fan blade construction while retaining titanium for the leading edges of the blades.

The tolerances required inside the fan and compressors of jet engines are extremely fine. Modern jet engines even have what is known as an ablative coating around the primary fan which is designed to wear away as the fan blades expand through heating. This keeps the gap between the fan and its housing as small as possible for efficiency.

As you might imagine, any solid object which is ingested by a jet engine can cause havoc. Any damage to the compressor section of a modern jet engine can cause what is known as a compressor stall which is a major disruption in airflow. When the airflow is disrupted, the fire can go out or be severely restricted. This is how Sully and his passengers ended up in the Hudson river courtesy of a flock of Canadian geese.

I should add a note about all the auxiliary components that, while not central to the operation of a jet engine, are attached to the engine in what is known as an accessory drive unit. It is located either beneath or on the side of the engine yet inside the cowling. Things like hydraulic pumps for the flight controls, generators, and fuel control units are driven through a drive shaft powered by the main turbine. Problems with these components may or may not result in engine failure depending on the affected component and the nature of the failure. 

In Conclusion

Modern turbine engines are models of efficiency and simplicity. They are highly reliable power plants and yet, like any machine, subject to occasional failure. That they fail so infrequently given the extreme conditions in which they operate is a testament to their design and upkeep.