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Tag: engine failure

UAL 328

On February 20, after the news of United flight 328 hit the airwaves, my phone began blowing up with people wanting to know if I was flying the airplane (no) or if I was on it (again, no).

In case you’ve been living under a rock or just consumed with the Kim Kardashian-Kanye West divorce, 328 is the Boeing 777 that departed Denver for Honolulu, only to sustain an uncontained engine failure shortly after departure. The crew declared an emergency and coordinated with air traffic control to return to Denver, touching down roughly 30 minutes after departure.

It’s understandable that folks want to know what happened, especially given the unusual pictures of debris that landed on yards in residential areas (the true miracle in this is that nobody was hurt on the ground). I have several theories about what might have happened, and all are realistically possible, but they might also all be totally wrong. One person on Facebook pointed out what appears to be damage to one of the fan blades on the engine, but it remains to be seen if the damage caused the explosion, or if the explosion caused the damage.

What I can tell you is that it will take months, if not a year, for the NTSB to come up with a probable cause. Until they do, it isn’t fair to anyone—the pilots, the airline, Boeing, Pratt & Whitney, the FAA, or any others that come to mind—to  pretend to know what did or didn’t happen, especially in a public forum such as this.

But I will say this: Events like the one on 328 are what we train for. We spend countless hours in classrooms and simulators discussing the myriad ways that normal operations can quickly go “abnormal” or “non-normal.” We brainstorm, we talk, we share, and when we get in the simulator, we get to practice dozens of possible scenarios in which a worst-case event is inflicted upon us. Some of them are hopelessly complex and borderline unsurvivable. Some are based on events that have happened in real life.

When we first start training in a new airplane or with a new company, we often make a lot of mistakes, and sometimes “red screen,”  which is the simulator version for a crash. But then we do it again. And again. And again. And for good measure, we do it yet again. Eventually, certain actions become ingrained; certain processes become second nature; and we tame the beast of unpredictability and the unknown. Our confidence in the equipment and ourselves grows. When training is complete, they trust us to let you, the flying public, to put your trust in us without reservation. And when training is complete, we continue to learn, to talk, to share what ifs. We do this every year.

I saw the word “scary” a lot. And I’m sure that the passengers were terrified, especially those that could see the engine doing things it shouldn’t do. As for the crew, my guess is that after a moment of unprintable words and an adrenaline rush, they immediately focused on what needed to be done.

First, fly the airplane. Identify for certain which engine is compromised, and to what extent.

Second, navigate. This flight was headed west, so terrain clearance over the Rockies was probably an early concern. The weather was good, which helped.

Third, communicate, first with each other, and then with ATC. Once an agreement was made on what the issue was, the appropriate checklist needs to be executed. One pilot likely took over the flying and radio, while the other handled the checklists.

Time was on their side. They were at a safe altitude, and there was no inclement weather to complicate the return to the airport. They had plenty of fuel. From what we know so far, the other engine was operating normally, and this is key: The second engine really and truly is a spare, and it really and truly can get a fully loaded airplane safely to an alternate airport. This is just as true over the Lower 48 as it would be had the issue occurred over the Pacific or the North or South Pole.

A far more dangerous scenario, and one we practice ad nauseum in training, would have been an engine failure on the takeoff roll, just before rotation (we call this a V1 cut). At that point, they would have been committed to getting a wounded bird airborne, navigating the transition from barely ground-bound as the wings generate lift, to airborne but with reduced power, which is one of the worst things a pilot can experience.

Losing an engine at altitude? I’ve dealt with this twice, and I’ll take that option over the engine failure on takeoff every time.

Kudos to the crew for a job well done. Years of training, expertise, and experience were put to use. We’ll get the answers about what happened in time, and our system will be better for it.-–Chip Wright

Performance limitations on takeoff

In earlier posts on this blog, I have talked about how airlines plan their flights and how our fuel loads will often limit what we can carry. In this post I want to discuss how performance will affect departure payloads.

The airlines do not plan for a payload capacity just based on what the airplane will carry. That would be too easy. Instead, the most important parameter that must be eliminated first is performance. Two parts factor into this. The first, and simplest, is the requirement to abort the takeoff at V1 minus one knot and still be able to stop on the remaining runway. That’s pretty simple to understand.

The second is an engine failure on takeoff, commonly called a V1 cut or V1 failure. In short, this means that an engine fails at or above the V1 speed, which means that even though the airplane is still on the ground, it will—it must—continue the takeoff. Performance calculations work backwards. Each takeoff consists of a four-segment climb that ends at 1,500 feet agl (there are some slight variations based on certain certification criteria for each aircraft, some of which may be chosen by the manufacturer, and some of which are federally imposed). Each aircraft will have different climb performance capabilities, and will thus reach that 1,500 feet, less one engine, at a different point in time for a given takeoff weight.

Performance calculations, given to the pilots in a useable format by the engineers who did the figuring, essentially work backwards. First, given the weather conditions, especially (but not limited to) temperature, we know, for each airport and each runway, at what point we must reach 1,500 feet following an engine failure. If we are too heavy, we won’t reach 1,500 feet in time, so we must start at a lower weight. As the temperature goes up, the performance goes down, so the maximum takeoff weight goes down. At John F. Kennedy International with a 14,000-foot runway at sea level, it is rarely a problem. At La Guardia, in the same city, with a pair of 7,000-foot runways and a number of potential obstacles not far from the runways, heat becomes a major problem in the summer.

Once we know the maximum takeoff weight based on calculated performance requirements, we can calculate maximum payload. Fuel is the first concern—you aren’t going anywhere without it. Once that is determined, you can determine the passenger and bag count. It gets worse if an alternate is required.

At airports with short runways or at high elevations, I’ve seen days where the CRJ can only carry 30 or 40 passengers. Sometimes the performance penalties are based on the surrounding terrain, and the potential requirement that we be able to fly a single-engine departure in mountainous terrain. Helena, Montana; Roanoke, Virginia; Key West, Florida; Chicago Midway; White Plains, New York; and New Haven, Connecticut, all come to mind as places where I have had to leave a lot of passengers or bags behind–not because of the ability to use two engines to get airborne, but because I need to know that the same airplane will fly safely with one engine shut down.

Winter operations can be problematic as well, because using engine bleed air for deicing operations can degrade performance. So can contaminated runways. Construction projects often wreak havoc as well.
This is a greatly simplified explanation of what goes into performance considerations, but it touches on the highlights. It’s something to keep in mind if you are told by the gate agent or crew that “performance” or “weight and balance” is going to require that you (or your bags) take a later flight.

As inconvenient as it may be, take some consolation that safety is not going to be compromised for the potential of a few bucks for the airline. They’d rather lose your money than your life or their equipment.–Chip Wright