Malaysia Airlines Flight MH370 And The Progress of Technology

Electronics and avionics are much safer than they used to be thanks to the work of thousands of engineers.

popularity

Cable news has been continuously deluging us with lots of speculation regarding the fate of Malaysia Airlines flight 370. Most of us are drowning in a sea of jargon as TV talking heads express incredulity that, “with all our modern technology, a plane disappeared…”

Although the disappearance of flight MH370 is a terrible tragedy, I see the larger context of our progress in commercial aviation as a very positive, and even amazing, technological accomplishment. We should be in awe of the technological advances in aviation that have made flights over large bodies of water possible, even routine. And we have the electrical engineering community to thank for many of the most important developments over the last few decades.

My goal in this article is to explain some of the progress in technology that has enabled safe and routine long-distance overwater commercial airline flights. I will attempt to explain some of the key concepts of the electronics technologies behind these advances, and highlight the amazing electronic technologies and contributions by the electrical engineering community that have made long overwater commercial flights routine.

Framework
Aviation by its nature is the most technological form of transportation we have on earth. Humans only started flying a little more 110 years ago, if you choose to give the Orville and Wilbur Wright credit for the first powered airplane flight.

The mantra that guided the actions and training of the very first pilots still lives today: Aviate, Navigate, and then Communicate.

These three priorities are drilled into every budding aviator’s head from the beginning of ground training through check rides for advanced certifications. In any situation, including an emergency, the first priority is always to fly the plane, i.e. aviate. The second priority is to navigate; direct the aircraft where you want to go and avoid other aircraft and ground obstacles. And when everything is under control, then you can communicate.

I will be using this framework to discuss key technologies that were invented by electrical engineers.
Aviate: ETOPS and the FADEC

For those of you who have traveled a lot internationally over the last 20 years, have you noticed a difference in the types of airplanes, frequency of flights and number of airports used for international routes?

In the late 1980s, a person traveling from North America to either Europe or Asia would expect to fly in a three- or four-engine jet such as the McDonnell Douglas DC-10 or the Boeing 747. Because these planes carry so many passengers, you would have a limited number of flights per day to choose from. In addition, you would not have a great choice of airports. On the east coast you would only have a hub such as New York and maybe Boston as a choice for your flight, on the west coast only SFO or LAX.

Today, things are very different. Your last transoceanic flight was most likely on a twin-engine aircraft such as the Airbus A330 or Boeing 767. If you were taking off from the United States, you are as likely to have taken off from Newark or Houston as from an international hub from the 1980s like JFK. And you probably had a choice of many flight times during your day of travel.

Here’s some data to show how much transoceanic flying has changed: The chart below shows that most passenger flights flown across the Pacific Ocean last year used twin-engine jets, while 4-engine jets like the Boeing 747 were used for most trans-Pacific flights in 2006.

2014-03-26 - flights
Figure 1. 2-engine ETOPS planes fly the majority of trans-Pacific flights today. (Source: OAG and CAPA)

Also, there has been a 52% increase in the number of flights across the Pacific since 2003.

2014-03-26 - passengers
Figure 2. Trans-Pacific airline flights have increased over 50% since 2003. (Source: OAG and CAPA)

Certifying jets with two engines versus three or four engines to fly across the oceans has enabled the airline industry to offer more transoceanic flights from more locations to more people at much lower cots.

But what has enabled safe transoceanic flights with aircraft that have only two engines, versus three or four?

ETOPS!
ETOPS is an unwieldy acronym for Extended-range Twin Operations. Some in the aviation industry jokingly define it as, “Engines Turn or Passengers Swim,” hinting at the core concept behind ETOPS: Significantly increased jet engine reliability.

Up until 1985, all aircraft flying transoceanic routes required 3 or 4 engines because the engines themselves were not reliable enough to safely allow the flight with only a twin-engine jet. The ETOPS program was created to increase jet engine reliability enough to allow twin-engine aircraft to replace 3- and 4-engine aircraft on long overwater routes.
For each engine, the ETOPS standard requires an inflight shutdown rate per 1,000 flight hours of 0.02 or less. That is one inflight shutdown every 50,000 flight hours, or once every 5.7 years!
The chart from Boeing, below, shows how the reliability of modern ETOPS certified jet engines has increased over older engines.

2014-03-25 - reliability
Figure 3. Today’s ETOPS certified jet engines have much have orders of magnitude better reliability than previous engines. (Source: Boeing)

Each ETOPS aircraft model is certified for a specific length of time that the aircraft can fly overwater. For example, the Boeing 737 Next-Generation aircraft family is “ETOPS 180” certified, which means it can fly on routes that take it overwater a distance equating to 3 hours from the nearest alternate airport. (This explanation is simplified, but explains the concept.)

The MH370 Boeing 777-200ER is “ETOPS 330” certified, allowing it to fly over water for 5.5 hours from the nearest alternate airport. In the graphic below from Boeing, you can see how ETOPS has expanded route possibilities between the continents.

2014-03-26 ETOPS
Figure 4. ETOPS expands the number of transoceanic route opportunities. (Source: Boeing)

Electrical engineering and the FADEC
What technological advancements led to the huge increase in reliability that allows today’s ETOPS flights? The main one is the FADEC, or the Full Authority Digital Engine Control.

The FADEC is similar to the electronic engine control in today’s modern automobiles. It manages the fuel/air ratio in the engine to provide maximum efficiency given the pilot’s throttle position and flight regime inputs. But more importantly for ETOPS, the FADEC works behind the scenes to keep the jet engine from accidently straying beyond design tolerances during flight operations.

extra
Figure 5. FADEC system block diagram showing control and sensor inputs. (Source: BAE)

Engine reliability studies for the ETOPS program found that the root causes of jet engine faults leading to shutdown were primarily linked to the pilot’s throttle commands accidently causing the engine to operate, if even for a fraction of a second, outside the tolerances for which the engine was designed. Repeated episodes of out-of-tolerance operation result in mechanical stresses within a jet engine, especially in the turbine “hot section”, where repeated incidents can cause a “thrown turbine blade” spinning at 10,000 RPM, and other havoc-inducing events.

The electronic sensors and controls in the FADEC work to ensure the engine never reaches these out-of-tolerance conditions, no matter what the throttle setting. A second, and equally important, benefit of the FADEC is that it monitors the health of the engine over time, and transmits this data periodically to the aircraft’s maintainers so that they can proactively repair or replace an engine before it requires an inflight shutdown. This near real time monitoring of engine performance is a significant pillar enabling ETOPS reliability.

Navigate: Sextants, INS and GPS
When it comes to long-range navigation with no landmarks, the sextant has been the go-to tool since 1757. It’s kind of like a slide rule for aviators: Slow to use, always accurate, no batteries required.
The first long-range jets included a sextant port for “shooting cel” (shooting celestial) inflight. Don’t believe me?

Here’s a picture of an unsuspecting Boeing 747 copilot getting doused with water through the sextant port by one of his crewmates:

2014-03-26 - b747 sextant port
Figure 6. Right-seater getting a bath from the captain through the Boeing 747’s sextant port. (Source: Damien Chng, Airliners.net)

The new versions of the 747 still have the port, but the sextant equipment is no longer used. This is because the Apollo moon program invented a new technology for navigation that finally replaced the sextant.

Inertial Navigation System (INS)
How do you know where you are when you are in space?

That was the problem faced by the MIT engineers designing the Apollo guidance and navigation system. Their solution combined the use of the trusty sextant with a new device: a gimbaled gyroscope platform that allowed the vehicle’s pitch, roil and yaw angles to be accurately calculated, and linear acceleration to be measured. The Apollo astronauts would “take a fix” on a star using their sextant, enter the fix into their new system, and then allow the system to continuously compute their current position using the fix as the starting point. Because the position calculated by this system, which came to be known as an “INS”, would “drift” from the actual position, astronauts were required to update it with a celestial fix on a periodic basis.

The Boeing 777’s INS is called the Air Data/Inertial Reference Unit (ADIRU). It has 6 ring laser gyroscopes, 6 linear accelerators, 4 processors, 3 power supplies and 3 I/O interfaces.

2014-03-27 - FADEC
Figure 7. Boeing 747 ADIRU block digram. (Source: A Fault-Tolerant Air Data/Inertial Reference Unit by Michael L. Sheffels, IEEE AES Systems Magazine, March 1993, http://www2.cs.uidaho.edu/~krings/CS449/Notes.F09/449-09-28.pdf)

Global Positioning System (GPS)
In addition to requiring periodic updates, the INS has some other undesirable characteristics. First, it had moving parts that could fail, including gyroscopes spinning at 10,000+ RPM. Second, old INSs were large and heavy. In 1973, the U.S .military started a project to create a smaller and more reliable navigation system. That system is now known as GPS.

GPS uses a constellation of satellites and an in-aircraft receiver to allow very precise measurements of present position. It works by triangulation. Each GPS satellite emits signals, travelling at the speed of light, that are received by a GPS receiver in the aircraft. The GPS receiver then calculates how far away each satellite is based on how long it took for the signals to arrive.

2014-03-27 - gps constellation
Figure 8. A GPS receiver needs to receive signals from at least 3 satellites to calculate and accurate position. (Source: www.gps.gov)

The beauty of GPS is that the receiver requires no moving parts and little power. It can be made so small; you probably have one in your phone.

Up until 2000, GPS was pretty much relegated to military use only because the GPS signals available for civilian use were intentionally degraded with an expected precision of only 100 meters. In a controversial move, this restriction was ordered removed by President Bill Clinton, increasing the precision to 20 meters and opening up the huge market for consumer electronics that use GPS today.

Communicate: SATCOM and ACARS
The third leg of aviation is communications, and there have been significant technological changes to aviation communications that enabled transoceanic flights. The first big change was the implementation of Satellite Communications, or SATCOM. In the old days before SATCOM, aircraft communicated over very long distances using high frequency (HF) radios, also called “shortwave radio.”

If you have any friends who are amateur radio operators, I’m sure they can regale you with stories about how atmospheric conditions were so perfect one time that they were able to talk to someone on the other side of the world using their shortwave radio. For HF communications to occur depends on atmospheric conditions, sunspot activity and a host of other things to be just right. It also requires a good operator. Pilots are busy people in the cockpit, and fiddling with an HF set to give a position report over the ocean is a pain. SATCOM removes this pain.

2014-03-25 - b777-radio-control-panel
Figure 9. Boeing 777 audio control panel. (Source: www.meriweather.com)

The airline industry uses Inmarsat as their SATCOM provider for voice and data. Inmarsat uses 11 satellites in geostationary orbit over the earth’s equator at an altitude of 22,236 miles (35,786 kilometers). This provides near 100% coverage of the earth surface, except for some gaps near the poles.

2014-03-27-inmarsat
Figure 10. Airlines subscribe to Inmarsat’s voice and data plans, which cover the earth except for the poles. (Source: Inmarsat)

Airlines subscribe to Inmarsat’s data and voice plans just like individuals subscribe to cable or satellite TV plans. There are a lot of options and prices fluctuate, and some airlines will subscribe to the bare minimum in voice and data services to save cost.

Aircraft Communications Addressing and Reporting System (ACARS)
SATCOM provides a better medium in which to communicate compared to HF, but what should be communicated?

Airlines are businesses, and their fleet operations divisions need to know which planes are on time, and which are not. The first use of automated digital communications was used to address this business issue and is called ACARS. ACARS was created primarily to automatically detect and report back to fleet ops when the aircraft leaves the gate, takes off, lands, and comes back into the gate. Sensors in the aircraft parking brake and a weight-on-wheels sensor automatically detect these events and send them through the ACARS system. The ACARS systems usually uses the SATCOM or normal VHF and HF radio systems to transmit this data back to flight ops.

2014-03-27-ACARS
Figure 11. The Boeing 777’s ACARS can communicate using VHF, HF or SATCOM. (Source: www.theairlinepilots.com)

Once ACARS was installed in planes, the airline industry came up with more uses for it: Pilots use it as a text-messaging client to communicate with flight ops and to obtain weather reports. And engine manufacturers like GE and Pratt & Whitney use it to periodically communicate engine reliability data from the FADEC back to the engine manufacturer or servicer to proactively schedule maintenance. This last use case has provided much of the information we know about the last hours of flight MH370.

Conclusion
By this time, I hope you know a little bit more about the technology invented by EEs that has helped make transoceanic flights commonplace. Although accidents and tragedies do occur, it is important for us all to keep them in context. It is because of the innovation and hard work of electrical engineers that we are able take transoceanic flying for granted.

Additional Sources:
Digital Avionics Handbook, Third Edition.