Plane Answers: Wake turbulence and the TCAS traffic avoidance maneuver

by Kent Wien on

Welcome to Gadling’s feature, Plane Answers, where our resident airline pilot, Kent Wien, answers your questions about everything from takeoff to touchdown and beyond. Have a question of your own? Ask away!

Patrick asks:

Greetings from SE Texas!

I enjoy your Cockpit Chronicles and Plane Answers as much as I enjoy surfing the airliners.net site. I’ve been an aviation enthusiast my whole life, and will often listen to streaming ATC feeds on liveatc.net.

I notice that very frequently I’ll hear the “caution, wake turbulence” callout by ATC and while I understand its importance, does it’s frequent use “dilute” the message? I know that hearing something, over and over and over can make it become just more background clutter.

When you fly a “heavy,” I guess you don’t get that callout, as I’ve never heard a “heavy” receive it from ATC (not that they don’t, I’ve just never heard it). In your opinion, FAA requirements notwithstanding, do you think this “overuse” will have a diluting effect on the warning?

Thanks Patrick,

As you know, we’ll typically receive that warning when operating close to the airport, either before takeoff or on final approach. As you mentioned, it’s an FAA requirement for ATC to warn us when we’re following a “heavy” aircraft, which are jets with a gross weight capability of more than 250,000 pounds.

The wake that a wing produces on these heavy jets has the capability to create significant turbulence for lighter aircraft following a few miles behind. In practical terms, these warnings are noted, but we don’t generally change our course, altitude or speed as a result. It’s simply offered as a ‘heads up’ in case we do begin to experience the effects of a heavy jets wake, at which point we could then slightly offset to smoother air.

As for the warning becoming overused and diluted, I’d agree that it probably has become that way, but in the back of our minds, we’re always aware of the power of these wingtip-generated vortices, even if we rarely come into contact with them.
Calvin asks:

Hi,

I recently had a flight where we took off and then about 5,000ft up we backed off totally where the engines actually sounded like they stopped. Then we felt like we were falling, then the pilot increased the power for about 10 seconds and then sounded like the engines were out again, then we fell again, you could feel the drop.

Then the engines sounded like they fired up and we climbed again. Everyone in the plane thought we were crashing and was very scary. The pilot said afterwards that there was a computer on board that said we were too close to another aircraft and made us go down.

Is this true? I have flown at least 200 times and have never experienced such a thing. I am very scared to fly after this flight and don’t know if we just dodged the bullet or if this happens but the experience of the pilot came into play. Can’t wait for your response.

Hi Calvin,

What you probably experienced was a TCAS (Traffic Collision Avoidance System) resolution advisory. Since the mid-’90s we’ve had a device on board that can direct us away from other aircraft by climbing or descending.

There may have been an airplane above yours that caused the TCAS to alert the pilots to stop their climb and descend. This can happen when an airplane is above you and you’re climbing at a great rate. We’ve learned to slow the climb rate down when we know we’re in an area with a popular arrival corridor above us.

A good example of this is at DFW where we may be cleared to climb to 10,000 feet. At 11,000 feet, airplanes are approaching the Dallas Love Field airport. When we’re climbing at a great rate, the TCAS sees only the potential for a collision and the computer doesn’t know we’re leveling off soon.

It’s hard to know for sure, but I’m convinced that TCAS is no doubt responsible for saving thousands of lives. It’s a great technology that has the potential to help when a pilot or controller makes a mistake.

We’ve learned that having multiple layers of safety in this industry is what prevents accidents. Not that this is what happened in your case. It’s entirely possible that the other airplane was never at the same level, but the rate of closure ‘tricked’ the TCAS into thinking a collision was imminent. Since this resulted in not just one, but two moderately evasive moves on the part of the pilots, it’s entirely possible that there was more than just two aircraft involved.

A display shows the proximate traffic even if it isn’t a hazard.

I’ve received less than a handful of TCAS resolution advisories. They always start out with a “Traffic, Traffic” proximity alert by the magic box. And then comes a command to “Climb. Climb now,” or “Descend, descend now” followed by a pointer on our vertical speed indicator directing us at what rate to climb or descend. When this happens, the other aircraft is being told to perform the opposite maneuver milliseconds after the TCAS systems decide what the best evasive action is.

If we’re directed to descend, there’s a good chance that we’ll pull the power back to idle which will feel very much like the engines were shut off. Virtually every descent you’ve probably experienced is accomplished at idle throttle, so you can imagine how startling it would be to go from a climb at a high power setting to a descent at idle so suddenly.

That said, our procedure is to turn off the autopilot and to smoothly but without delay, follow the directed commands of the TCAS while letting ATC know we’re responding to a TCAS resolution advisory.

Do you have a question about something related to the pointy end of an airplane? Ask Kent and maybe he’ll use it for next Monday’s Plane Answers. Check out his other blog, Cockpit Chronicles and travel along with him at work.

Plane Answers: What’s really in a pilot’s ‘kitbag?’

by Kent Wien on

Welcome to Gadling’s feature, Plane Answers, where our resident airline pilot, Kent Wien, answers your questions about everything from takeoff to touchdown and beyond. Have a question of your own? Ask away!

James asks:

Hi Kent,

I’ve always wondered what is in a professional pilots flight bag? Is there a difference between what the FO brings versus the captain? Furthermore with respect to airport diagrams and charts, do you carry only the approach and departure plates for the destinations you are flying to?

Ahh, yes. The kitbag. A twenty-five pound behemoth that constantly reminds pilots that we’re a long way from a paperless cockpit. Although Boeing and Airbus have recently introduced built-in electronic flight bags to their airplanes, those of us flying the older generation aircraft still need to carry around suitcases full of charts, manuals and procedures.

Since Gadling features a “What’s in your pack” series, I think it’s about time to ‘fess up about my tote.

As a kid, my friend and I would grab a couple of chairs and my dad’s retired kitbag full of discarded, outdated approach plates, and position ourselves so we were inside a closet, imagining we were pilots. I had no idea what the contents of the kitbag were for, but I knew we needed them to fly.

So what exactly is in one of those bags? Let’s start with the heaviest part first.

Jeppesen Approach Plates

There’s a company based in Denver that has specialized in creating maps and instrument approach charts for aviation use since 1934. What started out as a $10 book that early United pilots carried, turned into a large corporation that is now owned by Boeing.

We carry up to two of these volumes that weigh at least 3 pounds each. For international pilots, a domestic book and Europe, South America or Pacific manual is carried. These manuals include every conceivable landing airport we might fly to, along with alternate and emergency airports.

The books are updated every week or two with an envelope delivered to our mailbox at work containing the latest pages to be replaced. The most minute change at an airport will require a new set of these ‘plates’ that have to be swapped out.

Lots of occupations require a person to bring the work home with them–but pilots, for the most part, could leave their job at the door when coming home if it weren’t for these revisions.

Aircraft Manuals

There are three manuals for each airplane airplane our company operates. Two of them are about the same size as the Jeppesen binders, but we’re only required to carry one, the operating manual, which details the limitations, procedures and systems of our airplane. The other manual stays at home and it goes deeper into the aircraft design.

The third manual is much smaller than the other two. It’s called the Quick Response Handbook (QRH) and it combines all the emergency and abnormal procedures that we may need to accomplish. Emergency procedures, which cover engine fires, smoke in the cabin, rapid depressurization, etc., are marked with red tabs. Abnormal procedures, which deal with everything else, such as overweight landings, oven overheats and volcanic ash encounters, are marked with orange tabs.
Company Procedures and Regulations Manual

The captain is required to carry a manual we call “Part 1” which covers the company rules, procedures and FAA regulations. In this manual you’ll find information on flight planning, crew qualifications and responsibilities, approach and landing regulations and even specifics on our uniform dress code (black socks are OK, blue are not).

Aircraft Specific Minimum Equipment List

The FAA requires that everything operates on an aircraft before it can depart. But they understand that a flight needn’t be delayed to fix a seat-back recline mechanism for a seat that won’t be used, or an oven that’s inoperative.

So the airline, working with the FAA, has come up with a list of the minimum equipment needed to fly an airplane. Pilots call this the MEL and they refer to it anytime something isn’t working properly while on the ground. If the specific item isn’t in the MEL, (the extreme example is, say the LEFT WING) then obviously the airplane isn’t legal to fly.

On our airplane, the Captain carries the 757 MEL and the co-pilot and relief pilot, if there is one, carry the 767 MEL.

Trip Book

This is entirely optional. But I carry a smaller binder with the approach plates and maps for the more common airports that I fly to. Right now, I have the Jeppesen pages for Boston, Miami, London, San Juan, Santo Domingo, St. Thomas, Aruba and Cancun in there, but it can change every month as we add or remove destinations from my base.

I also carry the normal procedures paper checklist in this book, an RNAV approach guide and a quick reference guide to be used if our airlines dispatching computer system is offline before a departure.

Other Items

The FAA also requires that we carry a Flashlight adequate to accomplish all required tasks as well as a spare pair of glasses or contacts if we wear corrective lenses.

The airline provides a headset and wearable microphone in each airplane, but many pilots, myself included, prefer to buy our own type to use. I’ve tried a number of them so far, but most recently I’ve been using the Telex Airman 850.

And most importantly, I always carry a camera with me. I prefer to use something with a wide-angle lens, and the Panasonic LX3 is perfect for a kitbag camera. If I had more room in my bag, I’d bring a DSLR on every trip, but the added weight and bulk of the full sized Canon means the Panasonic sees more frequent use.

I often carry a Sigg water bottle with me as well.

Can’t we make this bag lighter?

In the past few years, our company has allowed us to carry what’s called a Class 1 Electronic Flight Bag. It’s a fancy name for a laptop, essentially. I have a Macbook loaded with the company manuals in a PDF format along with an extra battery and powerport charger.

This allows me to ditch the regulations manual, the MEL and the aircraft manual. I now only carry the QRH and the trip book in my kitbag, and I’ve been putting the larger two Jeppesen manuals which we’re still required to carry, in my main suitcase which sits behind my seat, since we rarely need access to them.

So with a need for a much smaller bag, I searched for the perfect solution. After reading Scott Carmichael’s review of the Tom Bihn Checkpoint Flyer, I figured this could be the lightweight bag I need. And maybe I’d set a new trend in pilot kitbags.

I have a feeling this type of bag will be far more common in the future among airline pilots, especially as cockpits enter the 21st century. The Tom Bihn bag had all the features I wanted and a few that I didn’t realize I needed.

It includes a fold out section that houses a laptop, which the TSA now allows in lieu of taking the computer out of it’s case. Flip out the laptop portion and let it slide through security. It’s definitely been a time saver, especially when you have to go through the process two or three times a day.

There are side pockets that hold my camera and headset perfectly, and the main section which holds the trip book and QRH. They’ve even got a small pocket on both ends that’s perfect for a flashlight and keys.

I shouldn’t be too surprised at the pilot oriented layout for this bag, since Tom Bihn’s dad was a Pan Am pilot.

I can think of no less than five pilots who have done damage significant enough to require surgery while lifting their full-sized kitbags into the cockpit. This Tom Bihn bag, coupled with the EFB and Jeppesen manuals relocated to a wheeled suitcase is my attempt at avoiding injury.

Hopefully airlines will retrofit their airplanes quickly with electronic flight bags, in which case, the behemoth kitbag might be a thing of the past.

Do you have a question about something related to the pointy end of an airplane? Ask Kent and maybe he’ll use it for next Monday’s Plane Answers. Check out his other blog, Cockpit Chronicles and travel along with him at work.

Plane Answers: Pilots are either heroes or villains after an accident

by Kent Wien on

Welcome to Gadling’s feature, Plane Answers, where our resident airline pilot, Kent Wien, answers your questions about everything from takeoff to touchdown and beyond. Have a question of your own? Ask away!

After an accident, pilots are either portrayed as heroes or villains. I talked a few weeks ago about Chesley Sullenberger’s heroic status, but we may soon see attempts to classify the Dash 8 pilots of Colgan Air flight 3407 as villains.

Speculation

Much has been reported about the crew of that ill fated flight. Theories began early, as some questioned whether the de-ice boots had been activated (they had) or if the pilots were aware of the icing (they were).

Reports came out detailing how long both pilots had been working at the airline, the number of hours they each had and some even queried the airline as to the experience each pilot had before joining the company.

I long for another couple of years without having to mention an airline’s flight number in the title to a Plane Answers post, but I felt the need this time to clarify a few inaccuracies.

Instant Expert

Any time an accident occurs, neighbors and friends will always ask me for an opinion. Just yesterday, the father of my daughter’s school friend asked me about the Colgan accident. I was surprised he was so familiar with the differences between anti-ice and de-ice devices.

It’s been the top story for the past three nights on the national news, so I suppose I can understand his interest. But I’ve learned that speculating on a cause before the preliminary report from the NTSB can often make the ‘experts’ look foolish when the report is released.
I’m never fully comfortable with commenting on something like this–I’m patient enough to wait for the exhaustive investigation that will be tackled by the NTSB.

But in this case, I’ve flown a similar type of aircraft in the state of Alaska, and I’ve run into significant amounts of ice.

So you’d think I would, like many other pilots, jump at the chance to offer a theory. I’ll admit, I’m inclined to think it was icing on the horizontal stabilizer, and that seems to be the leading culprit. We may learn that an issue with the aircraft is the true cause, or the pilots did something out of the ordinary. But it really is impossible to say until the NTSB team issues a preliminary report.

Is tail ice the culprit?

When ice builds up on the tail, the stability of the airplane is reduced, making it more difficult to control the pitch attitude of the plane. As the pilot lowers the flaps on the approach, the tail struggles to do its job. Some might be surprised to learn that the tail doesn’t actually provide lift, it does the opposite. So if the tail becomes ineffective, the nose of the airplane will pitch over.

In this 20-minute video, NASA demonstrates this issue with the same type of airplane I used to fly, the little brother to the Dash 8, the Twin Otter. The theory is the same for the Dash 8. If you really want to understand what the pilots may have experienced, take a look at this fascinating video.

NASA has successfully detailed the ‘feel’ of an airplane loaded with ice on its tail. As the flaps are lowered, or as the speed increases, a tail with as little as 1/4 inch of leading edge ice struggles to hold the nose up. The NASA pilots inadvertently entered a stalled tail condition and performed a perfect recovery by temporarily bringing the throttles to idle and raising the flaps. They managed to lose only 300 feet. But of course the NASA pilots knew what to expect and they knew they were right on the edge of a tail stall.

I’ve experienced light to moderate icing conditions in the Twin Otter, but I don’t remember it being significant enough to affect the pitch stability of the airplane. Perhaps that was because the aircraft was restricted to no more than 10 degrees of flaps after encountering icing conditions, a restriction that might find its way to the Dash 8.

Aviation experts are quick to point out the experience disparity between major airline pilots and those at a regional carrier. But these pilots weren’t exactly inexperienced. Furthermore, It’s unlikely a jet airliner pilot would face the same icing problems as the Colgan pilots that night.

Tail icing is such a non-issue in a jet that many airliners don’t even have anti-icing or de-icing capabilities on the tail. That includes all the popular Boeings, the 737. 757, 767, and 777.

Time for the blame game

Should the Colgan pilots have turned off the autopilot? Maybe so, but that also conflicts with our training that says we may want to use the autopilot to reduce our workload during low visibility approaches.

I have no doubt that a number of pilots that day accomplished that same approach in similar conditions with the autopilot on. It’s unfortunate that it takes a loss of lives to fine tune some of our procedures.

But you can be sure that we’ll see new training scenarios for flying turboprop aircraft in icing conditions, or even new restrictions. Pilots will become so familiar with these procedures and regulations that they may look back years from now and monday morning quarterback the decisions made by the Colgan pilots.

That’s how aviation continues to improve. If it turns out to be a mechanical problem with the airplane, or a training or procedural issue, the Colgan pilots will neither be heroes or villains, but simply victims just like everyone else on board.

But if they’re found to be at fault, as new reports are surfacing, then the villain label will most certainly be applied even before the investigation is complete.

Do you have a question about something related to the pointy end of an airplane? Ask Kent and maybe he’ll use it for next Monday’s Plane Answers. Check out his other blog, Cockpit Chronicles and travel along with him at work.

Plane Answers: Minimum fuel requirements and sudden drops inflight

by Kent Wien on

Welcome to Gadling’s feature, Plane Answers, where our resident airline pilot, Kent Wien, answers your questions about everything from takeoff to touchdown and beyond. Have a question of your own? Ask away!

Frank asks:

Kent,

A couple of questions for you:

  • How much reserve fuel does your plane normally carry? For how many minutes of flight or miles?
  • Who decides how much extra fuel to carry, the captain, FO, company or else?
  • Do you have a way to check how much fuel the plane is consuming? My Altima has a nice gauge that lets me know that, I was wondering what a multi-million dollar aircraft might have?

Thanks Frank.

There’s been some attention in the press lately about some airlines cutting back on the extra fuel carried because of the extra expense in adding unnecessary weight to the airplane.

The FAA requires that domestic airlines carry enough fuel to continue to an alternate airport plus an additional 45 minutes after that. The alternate airport has to have good weather in the forecast.

Our flights have been averaging 70 minutes of additional fuel which works out to almost 500 miles. I can personally think of just a few times when we have been in a holding pattern and needed to divert because we were getting close to our minimum FAA fuel (45 minutes plus enough to get to our alternate airport). In two of those cases, we were allowed to land at our destination. At no time were we sweating the amount of fuel on board.

Before each flight, the captain reviews the fuel requirements, the fuel computed by the dispatcher and the weather at our destination and alternate airports. If he feels we need more, he’ll pick up the phone and ask for an extra one or two thousand pounds from the dispatcher. The fuel decision is up to the dispatcher and the captain, but I’ve never heard of a captain being refused an extra fuel request.

During the flight, we have a fuel log print-out that comes up via ACARS and looks like this:

This fuel plan shows the time and the amount of fuel we are computed to have at each waypoint. It takes into account the forecasted winds, the altitude we’ll be flying at and the weight of our aircraft.

We write down the time and actual fuel as we cross each waypoint. Typically we’ll be up or down a few hundred pounds and a couple of minutes. If there’s a significant difference, we’ll look into the cause and consider diverting if we feel it could be necessary. The company also tracks our fuel burn via automatic updates which are sent from the airplane to ground VHF radio stations and then forwarded to the dispatcher.

As for any fancy indications in the cockpit, we do have a gauge that shows the fuel flow in thousands of pounds for each engine. On a 757, they read around 4,000 lbs an hour for each engine at cruise.

Cassandra asks:

Here’s another question for you (again, hyped by the media!). Why is it they love to report when going through turbulence that the plane dropped 500 feet or 1,000 feet? How do they get this information anyway and come up with these numbers?

Is this even possible?

There is a propensity for passengers and the media to describe a rough flight in terms of how far the aircraft “dropped.” But as you suspected, planes don’t just drop. I’ve used the analogy in the past that it’s like driving in your car and suddenly finding yourself on an interstate two miles away.

The media and a few movies have reinforced this idea that airplanes can hit ‘air pockets’ and drop hundreds or thousands of feet.

As I mentioned in a previous Plane Answers post about turbulence, even during some of the roughest air, we don’t gain or lose altitude generally.

There is one exception, however. If an airliner were to get far too slow, the resulting recovery back to a safe airspeed would require an immediate descent.

And on a similar topic, Kat wonders:

Sometimes when we are cruising in the air, there are moments when its feels like we have dropped a little bit and you get that roller coaster feeling and my stomach moves into my throat a little bit. Is that just the pilot maintaining our altitude? Is it supposed to happen? It’s scary sometimes because it can be a lot or very small–and yes I am one those people who are afraid of flying.

As we get to the higher altitudes, the flight controls are a bit more sensitive. So if a pilot is flying without the autopilot, the movements can be exaggerated, especially for passengers riding in the back. The autopilot can occasionally have some minor oscillations when it’s trying to level off or maintain altitude.

Imagine how smooth a road would have to be to drive a car at 500 to 600 miles per hour. Even the slightest change in the pitch of an aircraft will tend to make your stomach queasy.

Occasionally we’ll also get some oscillations when we approach a turbulent area. As the speed of the airplane increases or decreases when approaching changing weather, the autopilot adjusts to maintain altitude. This causes some very short climbs or descents of just a few feet that you’ll feel in your stomach.

As I’m sure you know, these movements aren’t dangerous for the airplane, but they can certainly be annoying. It’s just another reason everyone should keep their seat belts fastened while seated.


Do you have a question about something related to the pointy end of an airplane? Ask Kent and maybe he’ll use it for next Monday’s Plane Answers.

Check out his other blog, Cockpit Chronicles to travel along with him at work.

Plane Answers: Why captain Sullenberger and his crew deserve the hero status

by Kent Wien on

There’s an interesting trend in our culture that cites pilots either as heroes or villains based on their performance in an emergency. I would imagine that Captain “Sully” Sullenberger would actually cringe at a pilot being given either label. And while we won’t hear from him until the airing of 60 Minutes this Sunday, I imagine he’ll proclaim that he simply did his job the best he could, and that the entire crew’s training contributed to the successful ditching.

But Captain Sullenberger might deserve far more credit than he’s (hypothetically) giving himself. Sullenberger’s ‘stick and rudder’ skills are what I would hope most pilots are capable of. But his true act of heroism, and the main reason he may actually deserve that label, isn’t getting much attention.

It was his decision to abandon any chance of an engine-out landing back at LaGuardia or the Teterborough airport, and make his way for the Hudson River, that should be commended. Considering the position they were in, I’d imagine a majority of pilots (probably myself included) would have made the attempt to turn back to LaGuardia. Of course, in hindsight, this would have been far riskier.

Prior to US Airways 1549, ditching an airliner in icy water has, for most pilots, been a euphemism for meeting thy maker.
We train for ditching scenarios mostly in ground school, since the simulator can’t really recreate a water landing. In a classroom we cover the emergency equipment, slide and emergency exit operation, safety equipment location and crew member responsibilities every 9 months to a year during our recurrent training.

We’ve been told that a successful ditching is entirely possible, that the airplane will have a rather significant amount of buoyancy, and in fact “may float for a considerable amount of time if intact.”

This Pan Am ditching is a good example of that theory.

In the simulator, we often end our training session with a ‘dead stick’ (engine out) landing at an airport within 50 to 100 miles of our location which is rather realistic. Realistic enough to be sweating by the time you touch down.

Even after being taught about the potential for a successful ditching, most pilots imagine their scenario in the middle of the Atlantic. And this thought has led many of us to consider a successful ditching rather improbable.

Since every pilot has now witnessed how successful a well planned ditching can be, Captain Sullenberger may deserve some credit in the future for saving lives. There haven’t been many recent ditching examples, and certainly none have received more attention than that of US Airways 1549.

I’m sure many pilots would have made attempts to go for the other airports with varying degrees of success. I’m looking forward to running through this exact scenario in the simulator. I’ll be sure to share the excitement of attempting to land at LaGuardia in a future Cockpit Chronicles. In the meantime, you can try your luck using a rather ridiculous web simulation.

My hat’s off to the captain for making this difficult decision, his command of the evacuation and even his presence of mind to retrieve the aircraft logbook after checking for any other passengers before being the last to step onto the slide-raft.

And the rest of the crew?

US Airways has seen an amazing amount of stagnation – more than any other U.S. carrier in the past decade. First officer Jeffrey Skiles has witnessed that first hand. He was previously a captain at the airline but even though he was hired in 1986, his seniority caused him to be bumped back to the right seat during the past 8 years of shrinking.

Skiles immediately jumped into his role as the non-flying pilot after the bird strike caused captain Sullenberger to take over. He turned to the only procedure in the book that might get them out of the situation, a loss of both engines checklist and made every attempt at getting an engine started.

It was a procedure that was designed to be accomplished at a higher altitude with more speed. But who knows; with the right combination of starting the APU (auxiliary power unit used for electricity and the air to start an engine at slower airspeeds) and his relentless attempts at a relight, maybe first officer Skiles would be the hero today.

Every ground evacuation seems to result in either broken bones or, in some cases, fatalities. That’s what makes the water evacuation led by the very experienced flight attendants at US Airways all the more amazing. With no fatalities and minimal injuries to the passengers, flight attendants Shelia Dail, Doreen Welsh and Donna Dent pulled off one of the most challenging procedures in their manual with, by all accounts, the utmost in professionalism.

Do you have a question about something related to the pointy end of an airplane? Ask Kent and maybe he’ll use it for next Monday’s Plane Answers.

Check out his other blog, Cockpit Chronicles and travel along on one of his trips.