Category: Flying the Line

I used to say there were only two things that worried me while flying an airplane: in-flight fire, and structural failure. Both are unpredictable, can occur with very little or no warning, and are insidiously dangerous. SwissAir 111 was an in-flight fire that quickly consumed the crew all aboard perished. American 587 was a structural failure that occurred after take-off when the vertical stabilizer separated from the aircraft. All aboard perished.

Those are dire and dramatic incidents, but they happen and they can happen again. These aren’t the only two accidents of this nature to occur but sometimes a better outcome is possible. In-flight fires can be fought, maintained, or extinguished. Structural failure doesn’t always lead to a loss of aircraft control. Aloha 243 suffered massive structural failure with a large piece of the fuselage separating from the aircraft and that plane landed safely with one casualty, a flight attendant. She was never found.

Nevertheless, these types of incidents are possible and are always something that I think about and wonder “what would I do?” or “will I even be able to react?” The worst thought for myself is encountering an incident where I don’t even have time to react to manage the situation. As pilots we all hope that we have the wherewithal to react appropriately and successfully manage the situation to a safe landing.

In light of my two fears, I’m not sure if I’m adding a third or just re-classifying my structural failure into a slightly broader category. In the past 18 months I have had two incidents of in-flight vibration that persisted through multiple phases of flight. This is significant because usually vibration is caused by the flight controls or the engines. If a power change doesn’t change the vibration then it’s likely the flight controls as they are the only parts that are supposed to be movable. If it turns out it’s not the flight controls then we have a bigger problem and structural failure could be next.

Last summer I was operating a ferry flight from Chicago to Raleigh-Durham. The aircraft had just come out of maintenance and they had either replaced or re-rigged the ailerons. The ailerons being the “little wing” on the trailing edge of the outside portion of the wing. These are the control surfaces that move in unison to roll the aircraft along the longitudinal axis.

I don’t usually worry too much about an aircraft just coming out of maintenance. I don’t have many superstitions when it comes to flying. I might avoid a 666 squawk code or flying at 13,000 feet if I have to. But maintenance isn’t something I worry about.

We actually had to drive to the hangar to pick up the aircraft which I guess should have been a bigger clue to pay close attention to the aircraft maintenance history. I didn’t actually know why it was at the hangar until after the event happened.

The Captain and I arrived at the aircraft and began our preparation to fly to Raleigh-Durham. Besides the fact that we would have no passengers, this would be a normal flight. The flight attendants were already on-board and ready to go. The plan was to fly to Raleigh-Durham and pick up a load of people that got stuck overnight and fly them to Newark. Standard stuff. Nothing out of the ordinary.

Once we figured out the slightly convoluted maintenance hangar ramp procedures, we were ready to taxi. After we started both engines, we began our long taxi to the departure runway at O’Hare. From the hangar to runway 22L was about the longest taxi you can get for departure. By the time we were ready to depart the brake temperatures were approaching the maximum limit for take-off.

As long as they don’t exceed 300 degrees, we can take-off. However, what happens when you depart and put the gear up into the closed off gear wells? Usually they get warmer. This meant that after we took-off we would leave the gear down for a few moments to allow them some extra time to cool off.

What really happened is out of habit when we took-off we put the gear up. Then the Captain regretted that decision and wanted to put the gear back down. Which required us to slow the aircraft back down below gear extension speed.

Isn’t this about in-flight vibration? Yes. Good focus.

The gear did two things to us in this situation. It distracted us from any abnormal cues, and it required us to slow the aircraft down. For a few minutes during our initial climb our focus was on the gear, the airspeed for gear extension, and the brake temperature. Once we cooled off the landing gear and put the gear up, we accelerated to our normal climb speed.

Which is where life got interesting. Once the airspeed was above 300 knots in the climb, we felt a very consistent and very noticeable vibration. I was actually out of my seat when the vibration first started. Being a ferry flight, I had walked to the galley to pour myself another cup of coffee. It was like a scene from a movie, I am pouring my coffee and the plane started vibrating and my coffee cup shuddered in my hand.

“That’s odd…” I thought to myself as I walked back into the cockpit.

“What the hell was that?” I said to the Captain.

“I don’t know.” He said looking at the instrument panel, head half-cocked to the side like a curious puppy.

Airplanes do a lot of things at different times during flight. Vibrate ain’t one of them. The engines produce very small vibrations that can sometimes be felt in waves as they are out of sync slightly. The low hum of the outside wind flying around the fuselage is constant and loud. Airplanes do not vibrate like a washing machine with a lopsided load. They shouldn’t. Ever.

What you’re really feeling is an oscillation. Sometimes oscillations get worse and worse until something departs the aircraft for good then who knows what will happen. Sitting down in my seat and putting my seatbelt back on I had the feeling of “this is not good.” I put my coffee down and started looking around for clues.

The airbus has very good system synoptic pages that tell us a story about the aircraft and what it’s presently doing or not doing. We can look at the flight controls on our display and see if they’re moving in ways they shouldn’t be (fluttering in the wind, creating the oscillations or vibrations we’re feeling). They weren’t. We can look at the hydraulic systems to see if they’re over-pressurized and we’re feeling some feedback through the fuselage from the hydraulic pumps or lines. We’re not. We can look at the pressurization page to make sure the pressure vessel is intact and we’re not feeling the inside trying to fly to the outside. We’re not.

All this looking and we’re no smarter than the puppy with his head half-cocked.

We slowed the airplane back down below 300 knots and that seemed to alleviate the vibration significantly. Well that’s a step in the right direction. As of right now we have no idea what’s causing it or how to fix it but we can make it less dramatic by slowing down. This is good news and it’s an immediate relief of sorts. We’re still not happy but we’re not concerned about pieces departing the aircraft or losing control of the aircraft.

This is when we start making decisions about where we’re going. We very clearly are not going to Raleigh-Durham anymore. Are we going back to O’Hare? Are we landing immediately? Should we declare an emergency?

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I'm working a crazy schedule this month. Crazy awesome, that is. For the first time in my five plus years at the airline, I'm working three days followed by four days off. It's crazy having four days off in a row every week. It hasn't exactly been as much of a boost to my homework productivity but it has been a boost to my Netflix queue. Currently, I'm avoiding homework to write about something that happened on a flight last week.

"When something does happen that accellerates the pulse we usually have the ability to problem solve or otherwise mitigate said accelleration."

I've recently crossed the 5,000 hours logged threshold and I'm getting pretty comfortable in my "new" airplane that I transitioned to in 2013. I've got about 1,200 hours in the jet and there aren't a lot of things happening for the first time anymore. Rigamoral and boring is the ideal as a pilot. We strive to limit the exciting or abnormal happenings. When something does happen that accellerates the pulse we usually have the ability to problem solve or otherwise mitigate said accelleration.

Recently on our return flight to Chicago from El Paso, we were in search of a smooth ride at 31,000 feet. Our dispatcher had filed us down low in an effort to avoid the turbulent air above, however, we were bouncing along the cloud tops right at 31,000 feet. I try to reiterate to the passengers whenever we're in turbulence that it's nothing more than an annoying inconvenience, but we still try our best to avoid it. So up we went, 33,000, and eventually 35,000 feet. Even all the way up there we were still grazing the upper reaches of the clouds.

We had only been in flight for about 30 minutes by the time we made it up to 35,000 feet and the ride was finally starting to smooth out as we progressed towards Chicago. As you can imagine, the airspace up at these altitudes is usually pretty busy with airline and business jet traffic. Today was a little less busy as it was mid-day on Sunday, but we still had a decent amount of airplanes crossing our path. When another airplane crosses in front of us, air traffic control will alert us so we can be aware of them. They'll tell us which direction from us they are, which direction they're travelling, and their altitude and aircraft type. This helps us locate them, and ensure they're where they should be and that no collision threat exists.

"Traffic at your 2 to 3 O'clock, north-west bound, leveling a thousand feet below you, is a Phenom."

"Traffic at your 2 to 3 O'clock, north-west bound, leveling a thousand feet below you, is a Phenom." An Embraer Phenom is a very light jet that some private operators fly as well as some corporate and charter companies. This call from ATC was nothing out of the ordinary, we get these types of alerts from ATC probably a hundred times a day. We look outside for the airplane, make sure we're going to miss them, and then we resume reading the instruments (newspaper).

It's also not uncommon for a climbing aircraft to trigger a traffic alert from our anti-collision system called TCAS (Traffic Collision Avoidance System). This alert sounds an aural caution "TRAFFIC! TRAFFIC!" to let the pilot know that an aircraft is approaching and could become a collision threat. At lower altitudes these alerts are very common and almost always never become a resolution advisory (actual collision threat exists). At higher altitude however, these alerts are almost non-existent. Not today.

As the aircraft approached their cleared altitude of 1,000 feet below us, we recieved the "TRAFFIC! TRAFFIC!" alert. Up at 35,000 feet this is acutally pretty rare because climb rates are usually reduced in reduced vertical seperation airspace (RVSM). This alert got our attention and started that accelleration we try to avoid. The TCAS system is designed to alert us of traffic visually, aurally, and if needed, also provide vertical escape guidance both aurally and visually. It's a tiered system that escalates the alerts as needed based on the threat of collision. The system had shown us this aircraft visually at first, as just another airplane near us. Next it will show you an airplane that has a potential for a collision by changing the color and symbol on our display and giving the first aural alert of "TRAFFIC! TRAFFIC!" Finally, when an actual collision threat exists the display changes again to a red symbol and the aural alerts now give commands on what manuever to begin in order to avoid the collision.

"As a testament to the limitations of the human body during times of stress, I never heard the first aural RA."

"CLIMB! CLIMB NOW!" was the resolution advisory we received. The display also modifies our vertical speed indicator to show what rate of climb or descent is required to vertically navigate away from the threat. This was actually a corrective resolution advisory as the first one told us to descend. As a testament to the limitations of the human body during times of stress, I never heard the first aural RA. I think it was "MONITOR VERTICAL SPEED" – even though the aircraft was in level flight, we were experiencing some light mountain wave turbulence which causes the aircraft to oscillate a few hundred feet. Our vertical speed indicator is an instananeous indicator and will sometimes show a climb or descent as much as 1,000 feet per minute for brief moments. This tricked the TCAS into thinking we were in a descent when the RA was triggered.

"The tricky thing here is getting the aircraft away from the threat expeditiously while simultaneously avoiding loading the wing too much and inducing a high altitude stall. Yay we missed them! Boo now we're falling with style!"

After initially commanding us to maintain a rate of descent to avoid the aircraft, the system calculated that our descent was no longer an option to avoid the aircraft and it then commanded us to climb. The tricky thing here is getting the aircraft away from the threat expeditiously while simultaneously avoiding loading the wing too much and inducing a high altitude stall. Yay we missed them! Boo now we're falling with style! Up at this altitude the airplane has a much smaller margin of "too fast" and "too slow," it is inbetween these speeds that we must remain in order to be considered still flying. Entering a high rate of climb at this altitude is usually non-sustainable (and non-habit forming). Our goal in this situation was to climb fast enough to avoid the conflict, but not so fast or too quickly to deplete the energy on the wing to induce a high altitude stall.

Luckily for me and for all the people behind me, we managed to avoid all the pitfalls of the event and complete an uneventful flight. It did take a few minutes for the reality of the situation to register. We spent quite a few moments recollecting what happened and why. It's very rare for this type of event to happen, especially at such a high altitude where aircraft are meticulously seperated from each other.

We never heard the other aircraft on our frequency, so it's likely he had already been switch to a new controller. We don't know if they had the wrong altitude programmed or if they were simply climbing so fast the computer calculated a collision risk. What a lot of people don't know is that scenarios like this one is how our modern day FAA got started. 

Less than one month left on my probation as a first officer. Looking back I can hardly tell where the year went. It certainly didn’t feel like any year I spent as a flight instructor. This year, pardon the cliche, flew by.

When you think of employment probation, time frames that often come to mind are; 90 days, 6 months maybe. Did you ever think you could be on probation for an entire year? I didn’t. I had never even contemplated that as a possibility. Well that’s how long my probation as an airline pilot has been so far. Considered an industry standard, the year long probation pretty much removes any requirement for the airline to have substantiated reasoning to cut loose a pilot. Although some people will fear this more than others, it’s important to remember that I am an investment to the airline. They spent a fair amount of capital training me and keeping me employed. However I’m sure I’ve earned more for the company than I’ve cost them in terms of revenue service completed.

My probation was just a few different interviews with my chief pilot at 6, 9, and soon to be 12 months. Included in that is a probationary check ride. Part of the glamour and glory of being an airline pilot, is the pleasure of jumping in a simulator every year. That is until I upgrade to captain, then they double the pleasure, double the fun, double the check rides. At that point you go every 6 months.

Anyways, the probie ride was pretty straight forward. Just your regular ‘ol proficiency check. Kind of like what is required for part 91 pilots, known as a flight review. The PC covers all the essentials plus a few. Most flight reviews don’t include instrument approaches however, and since we don’t have to log approaches for our instrument currency, we get to demonstrate some on the PC.

I was extremely nervous and hopefully slightly over prepared. There is so much pressure right now to not fail check rides and PCs and especially at the 121 level. The industry is in reactionary mode right now in the wake of some previous accidents. As such, they are putting a lot of pressure on applicants that basically equates to check ride failures = not getting hired. Certainly there are exceptions to this, however it’s pretty wide spread belief that more than 1 failure, sometimes even just one, can mean the difference between you and other qualified applicants. Now put on top of that, the rumored belief that if you fail your probationary check ride, you could get fired! Not only could I maybe not get another job, but I might get fired from my current job?! Holy Toledo!

Now most of that is just rumored speculation, however, at a stressful time such as in the moment of the PC, it doesn’t matter. It adds to your stress level and it overcomes you. Which was the case with myself. I studied religiously, read endlessly, and prepped relentlessly. In the end it paid off, however my stress level was pretty high for a few days prior to the day.

I got incredibly lucky to have a very cool, calm, and relaxed check airman. He helped me relax, and he showed me some pretty neat insights. I was also lucky to have a cool captain that helped me out a lot too. I think they both understood the pressure level assumed for probationary rides and they both were a huge help.

One interview left, and it’s on to bigger and better things!

One of the stall warning indicators the airplane is equipped with is the stick shaker. It helps provide a ‘WAKE UP’ warning to an impending stall. It literally creates vibration in the yoke control that simulates a car on a dirt road feeling. The mechanism that creates it is loud, while holding the yoke with it active it will shake your entire arm.

There is no mistaking what is occurring when you feel and hear the shaker activate.

Recently during a departure from a hub airport, we were cleared for take off immediately following an Airbus 319. You’d be surprised how close they clear us for take off normally, however during this departure they were stacking us pretty close.

This specific hub airport utilizes RNAV(Area Navigation, more commonly known as GPS) departure procedures for all RNAV capable aircraft. This means that the flight path for 99% of the traffic departing the airport is within one tenth of a mile of each other. With adequate lateral and vertical separation it’s never really a problem. During this departure we had significantly less lateral separation, however still beyond the minimum required.

Around 1500 feet above the ground we encountered the wake turbulence from the Airbus.

Predictable.

Wake turbulence is defined as a byproduct of induced drag. As airflow over the wing passes over the tip of the wing, it rolls over as it’s mixed with the air from under the wing. There is a small amount of span-wise flow from the air under the wing that creates a rotational vortex. These vortices flow outward and down from the wing tips of the aircraft. Since these are created as a byproduct of induced drag, the heavier the aircraft, the more intense the vortices. There are other factors that create more wake turbulence such as clean and slow aircraft. Clean referring to lack of high lift device deployment such as flaps or slats. Without those devices employed a higher angle of attack is required for flight which increases lift production, which increases induced drag. Slow aircraft require more angle of attack as the amount of lift generated is directly proportional to the indicated airspeed of the wing.

Put all of these factors together and you can see that during take-off, you have the highest amount of wake turbulence creation after take-off.

Small vibrations of what normal light turbulence feels like first. The captain is hand flying the aircraft throughout the climb. One of the signs of wake turbulence is the rotation force exerted on the aircraft that requires aileron input to keep the wings level. That happened next.

Another stall warning and protection device our aircraft uses is a pitch limit indicator. It shows how close to the stalling angle of attack the aircraft it currently at. It immediately showed that we were less than 3 degrees from stalling angle of attack. Simultaneously the stick shaker activated.

The entire event lasted less than 5 seconds.

I spent years teaching students about the dangers of wake turbulence and the techniques to avoid it. This made me realize I need to be more vigilant about it. Almost every take off and landing we hear ‘caution wake turbulence’ because we’re either landing behind or taking off behind a heavy airplane. Perhaps that dumbs it down a little or dilutes the seriousness of it.

Land above and beyond, rotate before and climb above.