Tuesday, April 25, 2017

Why is it Always So Freaking Cold (or Hot) on my Plane?

Temperature control on airliners shouldn't be difficult
Freezer or Sauna?

You get to the airport parking lot, run to catch your shuttle, make it through the TSA body cavity search, and then schlep your stuff a thousand yards to the gate. You board and heave your rollaboard into the overhead bin. After finally sitting down you notice two things: you are drenched in sweat and there is almost no air coming out of the vents. Or if there is air, it is warm.

Or perhaps it's July and you have a light shirt and slacks on for your trip but have brought no jacket. But shortly after takeoff you notice that it's cold in the cabin. I mean really cold. Your hands are blue and you are shivering.

So why the heck can the airlines never seem to get the temperature right? How difficult can it be?

As it turns out, getting it right is more difficult than you would think. This issue has about 85 moving parts involving both human and mechanical factors. I'd like to go over each aspect of what goes wrong, but first let me give you a quick description of the systems in place which provide heating and cooling aboard your aircraft.

Heating and Cooling At the Gate

In years gone by, heating and cooling at the gate were mostly provided by running a unit on board the aircraft known as the auxiliary power unit or APU. This is a small turbine engine usually mounted in the tail which provides both electrical and hydraulic power for use during preflight and also pressurized air to run the air conditioning or heating system. 

It generally worked well but consumed a lot of fuel and the technique was eventually replaced by the use of large heating and cooling units mounted directly on or near the jet bridge. Ground crews are required to attach a large air hose to the belly of the aircraft to allow this unit to heat or cool the interior of the plane. The systems are either programmed to provide a preset temperature or a temperature probe might be hung in the cabin to provide feedback to the system.

737 Pneumatic System
737 Air Distribution

Cooling and Heating While Under Way

After the airplane is away from the gate and under its own power, all heating and cooling is provided by onboard systems which are powered by compressed air from the engines. These onboard units are known as pneumatic air cycle machines or PACs (on Boeing aircraft) and not only provide heating and cooling but also pressurization to the cabin while at altitude.

Without going too far down the rabbit hole concerning Carnot cycles and thermodynamic flow equations, suffice it to say that the units take hot compressed air from the engines and make cold air out of it or use the hot air directly for heat. Yes, all the air that you're breathing on an airplane is brought in through the mouth of the engines. It is also why an engine malfunction can quickly fill the cabin with smoke, but that's a topic for another time.

After going through some plumbing and a water separator, the air is distributed to the cabin through ducting and the gasper outlets, which are those little twisty vents over your seat. The system temperature is controlled through the use of a thermostat which is usually located in the cockpit. It is supposed to be a "set and forget" type of arrangement which should always provide a comfortable temperature over a range of aircraft operating states such as taxi, climb, cruise, or descent.

At least that's how it is supposed to work. Let's now take a look at the many things that can go wrong to make you miserable.

Human Factor Errors

One of the basic problems concerning complex feedback systems is that the user...you freezing or sweating in your seat...is not the controller. A systems engineer might say the feedback loop of this control system is in an open state. My suggestion is that you attempt to close the loop by hitting your call button and complaining. Many times certain parts of the plane may be warmer or cooler than others. The galley where the flight attendants spend most of their time may be fine. Let them know that you are not fine.

Another issue could be that the user is feeling perfectly fine, but that person is not you, it is a flight attendant. They are the ones who call the cockpit to request a warmer or cooler temperature. On some airplanes, they can control the temperature directly. Remember, they are constantly on their feet and are likely to appreciate a cooler cabin than you sitting in your seat motionless. Again, if no one complains, they have no way of knowing.

The same dynamic is true for the pilots. If they don't hear any complaints from the back, they'll just assume everything is OK. And speaking of pilots, they are sitting up front in a glass house. It is the guy in the right seat who controls the temperature, so if he is on the sunny side of the airplane and is warm, he'll just dial it down.

Another thing I've noticed is that some folks just naturally run cold or hot. Heavier people seem to like it cooler than thin people. So if your first officer appears as an endomorph and is sitting on the sunny side of the plane, that may explain why you're freezing in your seat. Again, hit that call button and complain.

Operator Errors

Another class of error in temperature control might be classified as operator errors. For instance, on a coolish spring or fall day the ground crews may simply neglect to connect the air hose thinking that the temperature outside is cool so it must be OK inside the airplane. What they don't realize is that several hundred bodies in an aluminum tube will always result in a stuffy cabin even on the coldest of days. This problem is compounded when the pilots fail to look out the window to see a folded up or deflated air hose. The solution is to start the APU and get some air flowing.

Being a commuter, this is my personal pet peeve. We have a certain set of pilots who mean well but have their priorities askew. They are reluctant to start the APU because they've been told that it uses too much fuel, so in this situation they will call station operations on the radio to request that the ground air be hooked up. Station operations will then call the ramp agent who's probably loading bags and now has to stop what he's doing to hook up the air. All this might take five minutes. And surely you won't mind going into your meeting with sweat stains on your shirt.

My technique is to reach up and to start the APU, get some air to the customers, and to then perhaps chase down why the ground air isn't hooked up or working. Most jet bridges are owned by the airport authority which is usually a city-owned bureaucracy. If they are out of service for maintenance, making a call to get them fixed is literally the same as calling city hall to get a pothole fixed. Good luck with that.

I was even once parked at a gate without a working APU, so the only source of air was the ground unit. As I sat there in a full airplane on a summer day, a city crew pulled up, turned off the unit, and before I could shout at them, drained the coolant out of it to perform some maintenance. When I asked them if they noticed this big blue thing with wings and engines sitting there, the answer back was that they had their orders and didn't know nuthin about no airplanes. Luckily we were close to pushback, but this is part of the impenetrable stupidity that makes the job so enjoyable.

Lastly, sometimes the system is either overwhelmed such as waiting for takeoff on a 110 degree day in Phoenix with a full airplane, or it simply doesn't perform as expected. There's not much that can be done about the former, but if the system won't heat or cool properly, it needs to be written up and fixed. This can take some time.

In Conclusion

The heating and cooling systems on jet aircraft are charged with keeping you comfortable while the temperature outside the aircraft can range from over 100 degrees to 50 degrees below zero at altitude. They usually do a pretty good job but have their limits mainly due to human or mechanical error. The best thing you can do to ensure a comfortable ride is to speak up...and to bring a jacket.

Monday, April 24, 2017

The Curious Case of Dr. Dao

The Curious Case of Dr. Dao
There were no winners here

By now we've all heard of the events on United Express Flight 3411 wherein a passenger refused to deplane to accommodate some deadheading crew and was eventually dragged off the aircraft by Chicago law enforcement officers. The passenger, Dr. David Dao, suffered some injuries including two broken teeth and had to be treated in a hospital following his forceful removal from the aircraft.

As this is an aviation blog, and before I bury the lede too far, I'd like to look at this event from the aspect of what the pilots could or should have done. The answer is much less than you might expect given that the airplane was parked at the gate and that there were no safety concerns. In spite of what a few keyboard warriors hanging around my blog may assert, federal law concerning pilot authority is quite clear on the limits to a pilot's responsibility and authority.

But before I dig into that, let's review the story as it stands so far, shall we?

The incident was captured on various personal devices for our enjoyment and the internet predictably blew up on cue. Many hot takes were given, much outrage was expressed, and many gallons of ink were spilled as everyone who could form an opinion, valid or not, did so. Here are just a few.

Everyone has gotten in on the act

The entire sovereign nation of China, one of United's largest destinations by customer count, wasted no time in ginning up the indignation sirens claiming that Dr. Dao's shabby treatment was a result of racial animus against persons of Chinese descent. This had to be revised to accusations of a general anti-Asian bias when it was revealed that the good doctor is of Vietnamese extraction. (The incident was nothing of the sort, and it would be nice if racism wasn't the knee-jerk go-to explanation for everything under the sun.)

Economists have weighed in on the economics of offering money to entice people to give up their seats. There's a good reason that economics is called the dismal science, as my head hurts after reading about all the game theory that applies. Perhaps United should have just upped the ante of cash offered. Eventually someone would have taken the deal.

Legal eagles have offered advice concerning the fine print that is contained in the contract of carriage which all passengers agree to when purchasing a ticket. One aviation lawyer I found believes that the airline was justified in removing the doctor as his opinion is that no property right is created through the purchase of a ticket. Another lawyer blog believes otherwise stating that United did not correctly follow its own directives. In the end, it will come down to precedent, case law, and the legal interpretation of words such as "boarded" and "oversold". The doctor has hired a competent lawyer and is planning on suing everyone in sight. My personal view is that while United may win the legal battle, it long ago lost the PR war.

From a law enforcement point of view, three officers from the Chicago Department of Aviation, were the ones who removed the doctor from the plane. The doctor resisted their efforts and in the process of this resistance hit his face on an armrest resulting in his injuries. At least one of the officers has been placed on leave for not following standard operating procedure (SOP). While I have no doubt that an investigation will determine whether SOP was followed or not, it seems to me that if a 69 year old man can't be removed from an airplane without being bloodied then perhaps they were doing it wrong. On the other hand, resisting law enforcement is never a good idea.

Civil libertarians of course see this as one more road sign along the route to the coming police state. I'm not so sure that this incident is reflective of an improper use of law enforcement. After all, should you plant yourself on a couch at Macy's at closing time and refuse to move, you will likely be escorted off the property by some form of law enforcement given enough time. United for its part has forsworn the future use of law enforcement to remove passengers. I think I can safely predict a new class of delay as passengers refuse to disembark for this reason or that and nothing gets done.

For some homespun humor and common sense about the incident we turn to Mike Rowe who points out that a simple appeal to reason would have quickly resolved the problem.

Lastly, many are pointing out that the good doctor himself has a somewhat shady past involving drugs and sex which cost him his medical license for a while. Even the doctor's story as to why it was important for him not to be removed was not quite true. So what does this have to do with anything that happened on the airplane? Absolutely nothing. Nothing, that is, unless you are a lawyer trying to paint the doctor as a quick witted grifter who intentionally acted out in search of a pay out. It will be left to the lawyers, judges, and jurors to sort that one out.

Pilot's Authority

The pilots of United were quick to point out that this incident actually took place on a Republic Airways owned and operated flight hoping to avoid association with the affair. That's some facile reasoning as the airplanes are branded with the United brand and the Republic employees are clothed in United uniforms. But the pilots probably shouldn't be so defensive. The pilots on that plane likely had zero input into any of the events that transpired. They may not even have known what was going on until the police arrived.

This of course brings us back to the topic of what the pilots could or should have done. There may have been a time in the distant past where pilots were expected to exercise authority over every aspect of the operation. Think back to, say, a Pan Am Model 314 making its way around the Pacific Rim in 1939. Back then the captain was the chief customer service agent and company representative. He had to be. There was no one else around.

Today things are different. Ticket agents, operations agents, boarding agents, customer service agents, ground operations supervisors, and the big kahuna, complaint resolution officials control nearly all aspects of airline customer service while the airplane is parked at the gate. They decide who goes on and who gets pulled off. The pilots do not.

 Federal Aviation Regulations (FARs) are quite clear on this matter. Here's the relevant text:

 §91.3   Responsibility and authority of the pilot in command. 
(a) The pilot in command of an aircraft is directly responsible for, and is the final authority as to, the operation of that aircraft. 
(b) In an in-flight emergency requiring immediate action, the pilot in command may deviate from any rule of this part to the extent required to meet that emergency.

In case you were wondering, the term "operation of that aircraft" does not include who gets denied boarding while parked at the gate. Do pilots have any input into this process at all? Yes, but only from a safety or security point of view.

For instance, should a flight attendant inform me that a customer appears to be inebriated during boarding, it is my responsibility to make sure we don't fly with an inebriated passenger, which is a violation of FARs. However I have been given zero training in recognizing the signs of inebriation. Perhaps the passenger has a medical condition or just took a pill to help with anxiety. I don't have the slightest way to tell.

Fortunately, the airline has hired and trained individuals who do have the expertise to make such a call. In fact all airlines expect their hired and trained experts to handle such customer service issues. Any pilot who came charging out of the cockpit to throw a passenger off for anything other than a clear safety issue would quickly find himself in the chief pilot's office making arrangements for an unpaid vacation or the target of a discrimination lawsuit or both.

In the case of a mis-boarded passenger as was the case here, pilots have little or no input. Oh sure, pilots can offer an opinion, but customer service issues are the purview of customer service agents. And once law enforcement arrives to remove a passenger at the direction of ground operations, pilots again have zero official input.

In Conclusion

United airlines unwittingly touched the third rail of customer dissatisfaction by becoming a lighting rod for an ocean of pent up frustration concerning airline passenger treatment (to mix metaphors). This frustration is no doubt heavily contributed to by the goons running the TSA, but it is the airlines' problem to solve. All airlines should do themselves a big favor by using this unfortunate incident to take a good look in the mirror and to ask themselves why their customers are so ready to grab the pitchforks when it comes to customer service. Incidents like this don't help.