Efficency End To End

From The Economist:

ENGINES on airliners are highly efficient when they are in flight, but not when operating on the ground. When a plane is taxiing under its own power, the engines burn vast amounts of fuel. A Boeing 747 can consume a tonne of fuel and emit several tonnes of carbon dioxide during an average 17-minute taxi to take-off. And when the aircraft lands there is likely to be another long drive to the passenger gate. Which is why there are various methods being developed for aircraft to use other means of propulsion while moving around an airport.

If you think about it, this was an area ripe for innovation for a long time now. Obviously having a second engine for taxi purposes on board is ruled out for weight and space reasons. Something external is obvious since these negatives are shed when it’s detached. Since engines would only need to start shortly before takeoff it would also mean less noise at airports.

It’s interesting that in engineering you focus on the primary use case and make it efficient. Once you’re done you continue to refine and make it more efficient. The folly is when you forget about other low hanging fruit near the edge cases, in this case when the plane is on the ground. While not a huge savings, it can potentially add up.

The Genius of Airline Baggage Tag Design

Slate has a great read on the design of airline baggage tags. My favorite part is the description of what the design needs to be able to deal with:

Let’s look first at how an ABT is made. In the interconnected, automated, all-weather world of modern aviation, tags must be resistant to cold, heat, sunlight, ice, oil, and especially moisture. Tags also can’t tear—and crucially, if they’re nicked, they must not tear further—as the bag lurches through mechanized airport baggage systems. And the tag must be flexible, inexpensive, and disposable. Plain old paper can’t begin to meet all these requirements. The winning combination is what IATA’s spokesperson described as a “complex composite” of silicon and plastic; the only paper in it is in the adhesive backing.

Bag tags must meet another set of contradictory requirements. They must be easy to attach, but impossible to detach—until, that is, the bag arrives safely at its destination and the traveler wants to detach it. Old tags were fastened with a string through a hole, but mechanized baggage systems eat these for breakfast. The current loop tag, a standardized strip of pressure-sensitive adhesive, looped through a handle and pressed to form an adhesive-to-adhesive bond, debuted with the ABT in the early ’90s. And the ABT, unlike string tags and earlier loop-y tag ideas, is easily attached to items that lack handles—boxes, say. Simply remove the entire adhesive backing and the loop tag becomes a very sticky sticker.

If you really think about it, it’s a pretty daunting set of requirements. The design they went with is not only quite simplistic and easy to print out it’s also quite effective.

While you can reduce it to a mundane sticker it’s a pretty impressive feat of engineering from the selection of a glue that can meet these requirements to a composite “paper”.

Air France Flight 447

Air France Flight 447 is the most puzzling crash since TWA Flight 800 because it just doesn’t make sense for the pilot to pull back and increase the angle of attack if they believed they were in a stall situation.

The NY Times reports:

The report offered an answer to a central puzzle: the consistent and aggressive “nose up” inputs by the pilot at the controls, which added to the loss of lift. Pilots are normally trained to point the nose of the aircraft down in a stall to regain speed.

The report said that the readings being gathered by the automated flight director — which uses cross hairs superimposed over an artificial horizon to indicate the required positioning of the plane — would have resulted in repeated calls for the plane’s nose to be lifted.

Popular Mechanic had a breakdown of the cockpit transcript a few months ago with this little tidbit:

02:11:03 (Bonin) Je suis en TOGA, hein?
I’m in TOGA, huh?

Bonin’s statement here offers a crucial window onto his reasoning. TOGA is an acronym for Take Off, Go Around. When a plane is taking off or aborting a landing—”going around”—it must gain both speed and altitude as efficiently as possible. At this critical phase of flight, pilots are trained to increase engine speed to the TOGA level and raise the nose to a certain pitch angle.

Clearly, here Bonin is trying to achieve the same effect: He wants to increase speed and to climb away from danger. But he is not at sea level; he is in the far thinner air of 37,500 feet. The engines generate less thrust here, and the wings generate less lift. Raising the nose to a certain angle of pitch does not result in the same angle of climb, but far less. Indeed, it can—and will—result in a descent.

Another seemingly valid explanation, though still puzzling that a pilot would try that at that altitude. Ultimately the end result was tragic:

By now the plane has returned to its initial altitude but is falling fast. With its nose pitched 15 degrees up, and a forward speed of 100 knots, it is descending at a rate of 10,000 feet per minute, at an angle of 41.5 degrees. It will maintain this attitude with little variation all the way to the sea. Though the pitot tubes are now fully functional, the forward airspeed is so low—below 60 knots—that the angle-of-attack inputs are no longer accepted as valid, and the stall-warning horn temporarily stops. This may give the pilots the impression that their situation is improving, when in fact it signals just the reverse.

So the final lesson is that they didn’t know how to fly the aircraft without the fancy computers, or at least forgot how to do so under pressure. Scary. Technology is great at assisting humans or replacing humans. However when ill equipped and prepared humans think they know better bad things can happen. This is why training is important.

This goes well beyond aviation. Knowing how/why things work, even when it’s computerized is important. Even more so when many lives are at stake.

Why Airplane Bathrooms Have Ashtrays

Everyone has seen that airplane bathrooms still have ashtrays, despite smoking being banned on flights for almost a generation now. Engineering Infrastructures For Humans has a great blog post explaining why (spoiler: because some people will still smoke). Even greater is the takeaway for anyone who builds anything:

You don’t engineer your systems with the belief that none of your computers will ever break. That’s insane; you KNOW they’re going to break. So don’t assume that your users will never break the rules. Build in graceful failure as often as possible, whether you’re designing a user interface or a security policy.

Airplanes are actually quite redundant in almost every respect from human error to mechanical failure. They are, generally speaking the gold standard for engineering.

Painting A Boeing 747 Is A Jumbo Job

Painting A Boeing 747

When you see a large get it’s not terribly hard to appreciate it’s size. It’s not that hard to appreciate the amount of power needed to get it airborne. If you need a reminder, stand behind one that’s taking off.

It’s pretty easy however to overlook the amount of time/effort that goes into the giant task of painting an airplane. This several minute time lapse is pretty eye opening. It takes a long time and many people to paint even the most “simple” livery onto a plane. And that particular aircraft has had at least 3 distinct paint jobs, perhaps more since it’s over 20 years old.

Confession: I’m A Touchscreen Snob

Continental Touchscreen

I’m a touchscreen snob, and I bet you are too. I bet every human being is. We get upset when things don’t react as expected and we get frustrated when things aren’t instant. Statistically this page loads on average under 2 seconds and it’s likely still too long for you. It’s not just touch screens. For example, 100 ms increase in load time of Amazon.com decreased sales by 1%. We’re an impatient species.

I took the above photo on a 757-200 equipped with touch screens on the back of every seat. I remember the days with only a handful of TV’s, or that big projector thing up front on planes, so I appreciate that a choice of entertainment is an upgrade. Lets take a look at it’s sins as it makes a great example:

Resistive Touchscreen

I’m virtually certain based on it’s poor performance it’s a resistive touchscreen. Unresponsive, and it requires a lot of pressure which the person in the seat in front of you enjoys for 8 hours. Resistive touchscreens are much more cost effective, though I wonder that difference is splitting hairs on a $65-80 million aircraft given there are only ~200 seats and the displays are relatively small.

There was a time when nobody would notice, but even a Droid v1’s touch screen is more responsive, and that phone is extensively laggy.

Poor Contrast

Part of this is likely because of the substrate used for resistive touchscreens, but the poor contrast is obviously an issue. Color reproduction is bad, but that’s not a deal killer, it’s a nitpick. Contrast is critical especially on a vehicle where lighting varies from dark to virtually unfiltered sunlight glaring on the display. Contrast controls are minimally helpful here.

Laggy

I suspect these are units are just terminals, so the performance can sometimes lag. It’s forgivable and likely will not be an issue in future generations. Thanks to the mobile revolution low powered ARM chips can be found everywhere. The need for these things to be dumb to save space and power is drawing to a close.

Sound

I’ve yet to figure out why airlines can’t manage to get rid of the noise in the lines. Sure when you use the $0.25 headsets they hand out you can’t tell the difference. But when you use your own higher quality headset you sure can. Given a cheap mp3 player can manage it, I wonder why this is so difficult. Weight?

My second gripe about sound is the volume differences. The movie is set to a comfortable level. If the crew takes over to show a video of your destination or a safety video, it’s uncomfortably loud. If the captain speaks, it’s painful. This is more than a nuisance, this is actually a safety issue.

The Recirculated Air Myth

Airplanes don’t recirculate air any more than most environments you spend time in. Despite this, people frequently claim various versions of this urban legend. Some say the air when they close the door stays in the cabin until they open it on landing. Others say it’s actually coming from air canisters stored on the aircraft. It is not true.

The air is really a 50/50 blend of recirculated air and new air bled through the engine air compressors (before combustion). The NY Times has a nice little writeup on cabin air:

Cabin air, he said, is refreshed about 15 times an hour, compared with less than 12 an hour in an office building. On most full-size jets, the air is also circulated through hospital-grade HEPA filters, which are supposed to remove 99.97 percent of bacteria and the minuscule particles that carry viruses. The cabin air is also divided into separate ventilation systems covering every seven rows or so, limiting the ability of germs to travel from one end of the plane to the other.

The reason most people feel the air quality is so low is because the humidity is about 10% to prevent corrosion of the aircraft, which is almost always metal. Newer aircraft are now being made using composites allowing for more natural humidity. The other factor is pressurizing to approx. 8,000 ft, which is higher than you’re used to.

Those HEPA filters employed are also more than adequate to filter air leaving it cleaner than most homes [pdf].

Presumably the confusion is aided by the emergency oxygen system on board modern airliners.

So next time someone claims that the air is literally unchanged through a 9 hour flight, you should call their bluff and ask for documentation. This has been a pet peeve of mine.

Google Fighter Jet

Dornier Alpha Jet

The movie Terminator is becoming more of a premonition as time goes on as I’ve suggested before. Google has taken another step closer to becoming Skynet. The company controlled by top Googlers just got it’s first Fighter Jet, a Dornier Alpha Jet.

Before you know it, this April Fools joke article by InfoWorld about Google acquiring the U.S. government will become true.

[Photo: Adrian Pingstone via Wikipedia]