Archive for turbulence

Fear of Flying: Turbulence In Perspective.

Posted in air travel humor, air traveler, airline, airline cartoon, airline industry, airline passenger, airline pilot, airline pilot blog, airline safety, fear of flying, flight, flight attendant, flight crew, FoF, travel, travel tips with tags , , , , , , on April 2, 2018 by Chris Manno

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It’s not unusual today to hear about travelers who fear air travel for a variety of good reasons. Fortunately, there’s help dealing with such fears readily available on social media in the form of special interest groups.

There are several Facebook groups centered around “fear of flying,” but here’s the best  one I’ve found:

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In this group, we (I am a member) in a closed forum for everyone’s privacy, using real names, share techniques and experiences that have helped many of our  members successfully get airborne on an airline trip that they’d previously felt was out of their reach. To join, click here and request access–it’s free.

My role there, besides providing cartoons of questionable taste,

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is to share what I’ve learned in 40 years as a professional pilot: 7 years USAF pilot, 33 years American Airlines pilot, 26+ as captain. I truly believe that much of the anxiety that comprises fear of flying can be attributed to fear of the unknown. Here, and on this Facebook page, we bust the myths and fill in the blanks to empower air travelers so that they can embark on a trip with family and friends with quiet confidence.

Here’s one of the most frequently discussed anxiety-producing flight effects we’ve discussed there recently:

Turbulence in flight: is it dangerous? The answer: no. Annoying maybe, startling probably–but not dangerous. The fact is, just like any fluid–the ocean, a river, a lake–the air has eddies and currents that change with velocity (both the fluid and the vessel) which may result in bumpiness.

But, your aircraft is designed with more than enough strength to handle any      turbulence.  Without getting lost in the mathematical and engineering jungle, here’s a thumbnail design sketch. Aircraft manufacturers were given design standards to meet that basically derived a “load[1]” limit the aircraft must withstand in normal flight. To that they added a generous margin and called that the “limit load factor:” the aircraft must withstand this force without suffering any damage or distortion of the structure or flight controls. To that increased margin they again added an additional percentage of force the jet must be able to sustain without experiencing structural failure and that is called the ultimate load factor.

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To put limit and ultimate load factors into perspective, those forces are beyond that ever experienced by an airliner in flight and quite frankly, approach the limits of human ability to tolerate such forces. In other words, the strength envelope is way beyond the endurance of our “2 mile per hour man.” That means your remarkable aircraft is built to superhuman strength standards and will tolerate external forces in flight and even on landing that will protect you well beyond any forces you could possibly encounter in flight.

The next tier of wonder is how aircraft designers maintain Sherman-tank strength standards in a vehicle light enough to fly not only smoothly but also economically and in of thrust required to sustain flight, efficiently. This is achieved through the ongoing evolution of composite materials that are lightweight but even stronger than older, heavier metals, and advanced engine technology that has produced powerful, lightweight and efficient engines.

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This is once again part of the “aviation learning curve” that is the driving force behind commercial aviation: new technology, advanced materials both metal and composite, that are lighter and stronger than in decades past.

Aircraft manufacturers continue to improve designs, producing safer, stronger, more efficient airliners year over year. I’m often asked my preference between the two largest commercial airliner aircraft manufacturers, Boeing and Airbus. I honestly believe both manufacturers produce outstanding, safe, and capable airliners, though I’m a lifelong Boeing pilot at heart. That said, one of the most capable and naturally talented airline pilots I know—my son—flies an Airbus. They’re both great aircraft.

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Me hitching a ride in my son’s Airbus 320 cockpit as he flew us to O’Hare.

That’s the kind of real-world, insider info and firsthand experience we share in this Facebook group. Join us, if you’d like to learn and share.

Also, I wrote this book for the group and periodically, reduce the Kindle price to zero for a few days so everyone in the group can get the book free:

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In this book, I walk you through a normal flight after providing you with a realm of behind-the-scenes experience in the airline pilot world. You can get a copy HERE, or just join the group and wait for the freebie offer.

Either way, if your travel options are limited by fear of flying–yours or a travel partners–just know there are assets available that will get you safely and confidently into the air. The choice is yours.

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[1] In laymen’s terms, “load factor” refers to the number of G’s, or the force of gravity, the aircraft must be able to tolerate.

 

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Air Asia Crash Raises Questions For Pilots.

Posted in air travel, airline pilot blog, airliner, airlines, flight crew, pilot, Uncategorized with tags , , , , , , , , , , , , , , on January 9, 2015 by Chris Manno

The search continues for the Digital Flight Data Recorder (DFDR) and Cockpit Voice Recorder (CVR) from the lost Air Asia flight 8501 and as that process drags on, speculation about the cause of the crash abounds.

Multiple news media sources advance abstract theories based more on the wide-open field of “what could happen” rather than what’s likely, serving only to blur the line between fact and fiction.

I won’t speculate on what happened to QZ 8501 because until the DFDR and CVR are recovered, transcribed and the recovered data analyzed, any theory advanced is just more noise in the media clamor aimed mostly at ratings rather than facts.

But, I can speak to what concerns me as the pilot of a modern, 160 seat airliner flying often in the same circumstances encountered by the lost flight. My goal in learning what the flight’s recorders report is simple: I want to know how to avoid a similar outcome.

With that in mind, here are my concerns. First, the slim margin between high speed and low speed limits at high altitude and the liabilities of each. Second, the problems presented by convective activity in crowded airspace. Finally, recovery from any inflight upset at altitude that may be encountered as a result of any or all of the above factors.

Early in any flight, the aircraft’s weight is the highest, limiting the ability of the aircraft to climb into the thinner air at higher altitude. As the flight progresses and fuel is consumed, the aircraft grows lighter and climb capability increases. Generally speaking, later in flight there are more habitable altitudes available due to weight constraints easing.

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But don’t think that climbing is the only option for weather avoidance. Often enough, a descent is needed to avoid the top part of a storm, the anvil-shaped blow-off containing ice, high winds and turbulence. Equally as often, lower altitudes may turn out to have a smoother ride.

The other major climb restriction along frequently used jet routes is converging traffic. Aircraft flying opposing directions must be separated by a thousand feet vertically, so if I  want to climb to avoid weather, I have to nonetheless stay clear of oncoming traffic. The New York Post reported the incorrect statement that the air traffic controllers handling the Air Asia flight “made the fatal mistake” of denying the Air Asia’s pilot request for a higher altitude. The first job of air traffic control is to separate traffic, particularly converging nose to nose. Climbing through conflicted airspace–or granting clearance to do so–would more likely be a fatal mistake.

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But there’s even more to the story: air traffic controllers respond to such requests in a more fluid fashion than the static “no” being implied by many media reports. In actual practice, for a climb or descent request, the denial would be more typically, “Unable climb, you have traffic on your nose,” or, “It’ll be 5 to 7 minutes before we can clear you higher,” or, “We can vector you off course so you can clear the airway and traffic and then climb,” or, “Unable in this sector, check with the next controller.” Regardless, there are other options to avoid weather.

If changing altitude is not an immediate option, lateral deviation is the next choice. But the same obstacles–weather and traffic–may limit that option as well.

So now, if vertical and lateral deviation isn’t immediately available, you must do your best to pick your way through the weather with radar, if possible, until one of those options comes available (again, at ATC denial isn’t final or permanent) or you’re clear of the weather.

Which brings us back to the margin between high and low speed limit. This is even more critical in convective weather, because turbulence can instantaneously bump your airspeed past either limit if there’s not enough leeway to either side of your cruise Mach.

The picture below shows a normal airspeed spread in cruise. Notice the speed tape on the left with the red and white stripe above and the yellow line below the airspeed number box. The hash marks represent 10 knots of airspeed. The red and black marker above the speed readout is called the chain, and it depicts the maximum speed limit for weight and altitude. The yellow line below the numbers is called the hook, and it marks the minimum speed required to keep flying.

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Turbulence, or more accurately, high altitude windshear, can bump you past either limit, or both, if there’s less than say, ten knots of slack, because moderate turbulence can cause swings closer to twenty knots; severe turbulence even more. Essentially, turbulence can instantly bump an aircraft out of its flight envelope.

In that case, the aircraft can depart controlled flight in a couple of different ways. The one that concerns me most is on the high end: if turbulence or any other factor pitched the nose down and the airspeed then climbed above the chain, the worst case is a phenomenon rarely discussed outside of the jet pilot community called “Mach tuck” that affects swept wing aircraft. Essentially, if you don’t immediately apply the proper corrective input, in a matter of seconds, recovery is beyond all means from the cockpit.

On the low speed side, if the wing stalls due to an airspeed below the hook, recovery is possible once the airspeed is regained. That takes altitude to regain, but normally can be done if a stall occurs at cruise altitude. But even that requires recognition and then the proper corrective control inputs, and Air France Flight 477 with three pilots in the cockpit entered a stall at cruise altitude but never identified the problem or applied the proper recovery inputs, resulting in a crash into the Atlantic that killed all aboard.

Bottom line: you need a wider spread between high and low speed limits in case of turbulence. If you can’t avoid turbulence and need to change altitude, you must assure a wide airspeed margin between limits to avoid being pushed by turbulence beyond either speed constraint. Here’s what the airspeed range looks like at high altitude:

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There’s very little tolerance for turbulence and any associated airspeed fluctuation.

In the worst case scenario, if the aircraft is pushed beyond its flight envelope to the extent that controlled flight is departed, a pilot must quickly and accurately recognize which situation is at hand, high or low speed buffet, then immediately apply the correct control input.

Problem is, they may initially look the same, and the correct remedy for one applied to the other severely worsens the situation. Specifically, if the aircraft begins a descent at a speed beyond the chain, the corrective action would be to deploy speed brakes, pull throttles to idle, apply back pressure to raise the nose, and I’d be ready to even lower the gear to add drag, even knowing that would likely result in gear doors being ripped off the aircraft.

If this recovery is not done early in the pitchdown, the result will be a dive with no chance of recovery.

If a low speed stall is encountered, the proper corrective action would be to add power and lower the nose until flying speed was recovered. But, if the high speed departure–also a pitch down and descent–was mistakenly interpreted to be a slow speed stall, applying the slow speed recovery to a high speed departure would be fatal.

The other way? If you mistakenly added drag and pulled back power in a slow speed stall? That would prolong the stall, but if the correct control input was eventually applied, the aircraft could recover, altitude permitting.

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Adding the factors that make this vital task of discrimination difficult would be any associated systems failure and the physical effects of turbulence that can make instruments nearly impossible to read.

In any pitch down, if rapid and deep enough, can cause electrical failure due to generators failing at negative G-loads associated with the pitch down. Yes, back up controls and instruments exist, but recognizing the situation, taking corrective action and reading backup instruments also takes time and attention.

Pitot-static failure, one of the contributing causes in the Air France slow speed stall, can also be difficult to recognize in turbulence or in an electrical failure.

Regardless, the high speed situation must be correctly identified and recovery initiated in a matter of seconds. Both situations would be difficult to diagnose and both recoveries would be very challenging to perform in turbulence and with any other systems failure or complication. Both recoveries are time-sensitive and if not managed correctly, one recovery could induce the other stall. That is, too much drag and power reduction carried beyond the return from the high speed exceedence can induce a low speed stall, and too much nose down pitch and excess power from a slow speed recovery could push you through the high speed limit.

So here are my questions, which are those that will be asked by The QZ8501 accident investigation board. First what did the aircraft weigh and what was the speed margin at their cruise altitude and at the altitude they had requested? What type turbulence did they encounter and what speed and altitude excursions, if any, resulted? What collateral malfunctions, if any did they encounter? And finally, what departure from controlled flight, if any, occurred, and what remedial action, if any, was attempted?

These questions can only be answered by the DFDR and CVR and my interest–and that of every airline pilot–is mostly this: I want to know what exactly happened so as to be prepared in case I encounter the situation myself, and I want to know what they did in order to know what exactly I should or shouldn’t do.

Like pilots at all major US airlines, I get annual simulator training in exactly these scenarios, hands-on practice recovering from stalls and uncontrolled flight. Is that enough? Can we do that better?

Once the facts contained in the flight’s recorder are extracted and analyzed, we’ll have the answers to all of these questions, which will help us prevent a repeat of this disaster. Beyond that, speculation is just a sad, pointless part of unfortunate ratings-hungry media circus.

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