Plane Answers: Single-engine taxi, engine-out flight and ATC confusion

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!

Julie asks:

Recently on a short flight on a de Havilland Dash 8, I noticed as we were taxiing down the runway that only one of the props was spinning, and the other one appeared to be off. I have seen this on other flights with the same type of plane, and the first time I ever noticed it I almost thought they had forgotten to turn it on (which is really, really silly I know)!

I know you don’t fly this kind of aircraft, but I thought you might have an answer anyway. I can’t really ever see into a jet engine to tell if it is spinning during taxi, so I guess it is possible that this is something regular with all twin engine aircraft and I just never knew it? Thanks Kent!

HI Julie,

I used to fly the Dash 8’s little brother, the Twin Otter. Even then, when fuel was less expensive than today, we would taxi on one engine as often as possible to save fuel.

Jets do this rather frequently too, but as you said, it’s rather difficult to tell from a distance.

There are limitations, however. We can’t taxi on one engine when we’re too heavy or when we may have to climb a bit of a hill on a taxiway, or if the taxiway may be slippery due to snow or slush. Also, on some aircraft, we need to be sure that we can give a 2 to 3 minute ‘warm-up’ time for the shutdown engine before we take off. So short taxis usually are accomplished with two engines.
John asks:

On a recent A340-500 flight the right engine sounded as if it had trouble. The flight deck crew left the side light on for about two hours and then turned them on every 2 hours after that (this flight was from JNB to ZUR). I was just wondering if we really did have a problem. We have been on many A-340 flights and have not noticed any engine noise.

Can the A-340 fly on 3 engines?

It’s hard to know if there was a problem on your flight, but you can be assured that if there were any indication of an engine issue, such as high vibration, oil loss or over-temperature, the crew would have shut the engine down.

All airliners are certified to fly with at least 50% of their power lost. So on an A340, that means any two engines could have been shut down and the airplane would still fly. They might have had to descend to a lower altitude, but they could still stay in the air.

The light you saw was a wing inspection light, used mainly to see if any ice was building up on the leading edge of the wing. It’s also used, along with all the other lights on the airplane, as an enhancement to the “see and be seen” philosophy when in the vicinity of the airport while on approach.

I’ve ridden in the back of a 737 while pilots were taking their checkrides. One engine was pulled to idle throughout much of this training and I was rather surprised to discover just how difficult it was to tell from the passenger cabin when we were flying on one engine.

While it’s never routine to have to shut down an engine in-flight, an engine failure on a four-engine aircraft is far from catastrophic.

Rishi writes:

I was wondering if you could explain to me the following two questions, please. First, why is that when I listen to ATC talk to pilots that one or both of the parties speak reasonably slowly, and understandably, but then, a moment later, they talk so darn quickly and un-intelligibly?

Second, given that ATC talks really fast at times, how do you pilots ever get to understand what they say? I’m quite surprised because I hardly ever get to catch the name of the airlines when the controller speaks so quickly. Please explain how you get used to this. . .

Hi Rishi,

There are times when pilots have to “read back” instructions from ATC. Those read backs are often spoken rather quickly. Complicated instructions that aren’t routine in nature are spoken much more clearly. So if the phrase is something that’s expected, such as a clearance for an approach or landing, clarity often suffers.

For an example, take a listen to www.liveatc.net and click on one of the audio streams of your favorite airport. After a while, you’ll notice the controllers giving nearly the same instructions to each airplane as they clear them for the approach. It might take an understanding of instrument flying to grasp what’s being said, but you’ll get the idea.

My favorite feed is from Caracas, Venezuela. Listen to the Delta and American flights going in there try to comprehend what’s being said, in between all the Spanish that’s spoken to the other aircraft.

Often it’s not the accent that’s so difficult to understand in a foreign country, but it’s the lack of awareness of the phrases used. I remember the first time I heard a French controller rapidly say “I-call-you-back,” instead of the more common, “Standby” that I was used to.

“Wha..?” I asked the captain.

I’ve now heard that phrase so many times, it doesn’t matter how strong the accent may be, I know what they’re saying.

LiveATC is a great resource for anyone who’s learning to fly or who might be working on an instrument rating.

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 feature.

Plane Answers: Aircraft inspections, air filtration and stalls

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!

John asks:

Hi Kent,

I’m a aviation nut and I’ve always been curious about this question: What is the difference between a C and a D check? I know they both involve overhauling the aircraft.

My friend Ed Straigis has become my ‘go to’ guy when it comes to maintenance questions that come up here. Fortunately, he just happens to perform these overhauls you’re asking about.

Here’s his explanation:

A “C” check is a complete, heavy overhaul; the aircraft is opened up, all inspection panels, seats, galleys, lavs, overhead bins, side-walls and insulation are removed and the aircraft is checked for cracks and out of limit equipment such as hydraulic actuators and bearings.

The brakes and tires are replaced and the aircraft gets washed and polished and comes out looking like new. This usually takes about 3-4 weeks.

We don’t do “D” checks, since we’re allowed by the FAA to do repetitive “C” checks, with each “C” check being more involved than the one before. Our C checks usually occur about every 18-24 months depending on the number of cycles (flights) on the aircraft.

Other carriers that do “D” checks usually do them every 4-5 years. They require the aircraft to be out of service for at least a month or more. It’s about the same a a C check but more involved.

Since we do our “C” checks more often that other airlines and cargo outfits, we’re able to find small problems and fix them before they become major problems instead of waiting to discover the issue during a “D” check.

Thanks Ed. I have always wondered about that myself.

Mark asks:

Kent, I continue to really enjoy your writing. You may not know this, but I often wonder how the hours I am putting on the King Airs I fly compare to those of the typical airliner. My operation has 6 King Airs and we are flying them about 1200 hours per plane per year. How does this stack up against what a typical airliner does?

Thanks Mark,

I looked up the latest airplane I flew yesterday, a 767 that was built in June of 2003, to get a feel for the utilization of our airplanes. It has 22,500 hours right now and it has made 3555 flights so far. This represents an average of 4,219 hours a year or 11 1/2 hours per day.

It’s pretty easy to have efficient utilization when each flight averages over 6 hours.

Years ago, when I flew the 737, I watched the hours on those airplanes as they approached their first full year flying and found them to consistently be in the 3,500 hour range. That makes sense, because domestic aircraft are on the ground more often, loading and unloading passengers, which keeps the utilization down.

Hope that helps, Mark. I would have loved to have flown a King Air.

Joe asks:

Hello Kent,

I have a question about the air circulation systems. When I was younger and would fly pretty regularly across the states to see my grandparents, my parents always seemed overly cautious to see that my sister and I would get enough vitamin C and other remedies that day to keep us protected “from all the sick people on the plane.”

That mindset seems to have rubbed off on my older self. Whenever I fly, part of me is always scared that I’m going to catch the flu from that guy twenty rows up because the air on the plane is “recycled” and that his pathogens are going to inevitably make it through my nostrils–and worse, the crew’s.

Is this true? I know planes are pressurized, but how does the air filtering work? Are planes REALLY disease-spreading pastures of sorts, or is my being concerned unjustified?

Your parents were definitely on to something. My wife, a former flight attendant, would get sinus infections every few months when she was working. I haven’t had as much of a problem as a pilot, but our air is recirculated more often than it is in the cabin. This has less to do with keeping pilots healthy and more to do with keeping the avionics and instruments cool in the cockpit.

Boeing discusses these cabin air quality concerns, explaining that:

“Microorganisms do not pass through the filters of the highly efficient air recirculation systems on today’s jets. The system delivers a mix that is one-half outside air and one-half filtered recirculated air. It normally produces between 14 and 20 cubic feet of air per person each minute. As a result, the air supply in the cabin is essentially sterile and particle-free.”

Boeing does go on to admit that anytime you’re in close proximity to other people, there is always a risk of catching whatever your neighbor has.

In addition to the air filtration systems in all airliners, some even have “ozone scrubbers” that are necessary to fly across the Atlantic in the more northern latitudes. When our airline first started to fly to Manchester, England, from the east coast, some of the airplanes we flew didn’t have these ozone scrubbers, for the first few months, which meant we were restricted to altitudes of less than 35,000 feet until the entire fleet had been retrofitted.

Apparently Ozone (O3) builds up in aircraft cabins and can present a health problem–especially to crews who spend a great deal of their lives flying. According to this article, it’s the most significant issue affecting the air quality in airliners today.

Fortunately, passengers flying on the new 787 will enjoy a lower cabin altitude, more humidity and greater circulation of the passenger air, according to Boeing. I really hope I get the chance to fly it at some point.

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Finally, Michele writes:

Hi Kent!

Another question from me, this one came up after hanging out at San Francisco’s Fleet Week air show a few weeks ago. What is stall speed? I had always assumed it had something to do with the engine, but I’ve been told it actually is more about lift and air speed. Can you clear up the meaning?

Good question Michelle, and one that is often messed up by the media.

A wing can only produce enough lift if it is flying fast enough. This airspeed will vary depending on the wing’s shape, whether the flaps are up or down, and how heavy the airplane is.

So when you hear about an airplane that ‘stalls’, it’s always related to a lack of sufficient airspeed.

Some people probably confuse it with the term “the engine stalled”, meaning failed to work. But that isn’t a term used in aviation. To be more clear, the media needs to understand that airplane engines don’t ‘stall,’ they simply quit or fail.

787 interior image at top provided by Ruthann O’Connor.

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 Friday’s Plane Answers feature.

Plane Answers: Do airliners ever intentionally takeoff without flaps?

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!

Just a note, we’re moving Plane Answers to Mondays. The question pool has been drying up a bit lately, so let’s hear from you.

Ray asks:

I was recently on a flight from Bangkok to Singapore on an A319. As I always do (as a Private Pilot), I listen for that reassuring sound of the flaps being lowered for take off as we taxied to the runway. We got to the hold short line…nothing. My heart start beating a little faster as we crossed the first runway and still nothing…we lined up and got ready to takeoff and still NO FLAPS.

I had visions of running up to the cockpit or shouting at a stewardess and telling them. I could see myself being interviewed after we landed in a rice paddy saying “I was going to say something…!” But instead I put on my iPod and clenched my clammy fists as we screamed into the air. Is it common for a jet airliner, even with light load or short route not to use flaps for takeoff?

Hi Ray,

I can’t think of any airliners that are certified for zero flap takeoffs. But I ran your question past my resident A319/A320 expert, Chris Norton, who responded:

The most common flap setting for takeoff is flaps “1” which means leading edge and a little bit of trailing edge are extended. The trailing edge usually doesn’t travel very far, and the LE makes almost no noise.

I am not surprised that he didn’t hear the flaps, but had they tried to take off without flaps I am sure he would have heard the takeoff configuration warning up in the cockpit. The A320/319 is not approved for zero flap takeoffs.

On short runways, at heavy weights or high density altitude, we will use optimized takeoff criteria which would mean we are at balanced field length, and could use flaps 3. It is not very common though. Think Las Vegas in the summer or Orange County.

Thanks Chris, for your insight into the A319. I’ve always wondered how I’d react as a passenger if I were in the same situation as Ray–staring out the window at a wing with flaps in the up position. When riding in the back, passengers put a great deal of trust in the pilots, their checklist adherence, and the takeoff warning horn that’s installed in every airliner. The recent Spanair MD-80 accident is a rare example of the failure of all three levels of safety built into the system.

This rather scary USAToday article mentions some similar events over the past 30 years. They accurately point out that distractions and human errors happen, and if that occurs at the same time as a failure of the takeoff warning horn, the results could be disastrous.

To ensure the safety of an airliner, there are many items that are redundant. Electrical systems, hydraulics, fuel pumps and pressurization are some of the many mechanical components of an airliner that are double and triple-redundant. A single failure of any of these things isn’t disastrous, but when all the layers are compromised, accidents can happen.

There’s a certain amount of trust passengers need to have in the design of the airplane, how it’s maintained and in the pilots who fly it. If that doesn’t comfort you, just try to remember that there are 10 million flights a year, and over 10,000 flights per day in the U.S. alone.

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 feature.

Plane Answers: Route planning, shunning reverse-thrust and side-sticks

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!

Vivian asks:

Hi Kent,

I enjoy your column very much and I have a pretty basic question. How exactly is a route for a particular flight planned? I recently flew ORD-DEL and we went to the North Pole and then due south through Asia. Wouldn’t a route through the Atlantic and over the middle east be a more direct route?

Believe it or not, flying from Chicago to Delhi will normally take you very close to the North Pole. Imagine using a piece of yarn over a globe to trace the route.

But an easier method is to go to this site and put in the three-letter codes yourself to see the great circle route depicted. Here’s the ORD-DEL example:

These routes, which are often made up of waypoints every few hundred miles, change every day to take advantage of the winds. Our dispatchers look at the shortest “wind distance” which they will usually use, subject to ATC approval. To fly over the pole, crews have to have special training and the airline has to be approved for this kind of flying.

These flight plans are filed with the FAA a few hours before the departure, so it is possible for the winds or weather to change the eventual route of flight.
Alex asks:

Hi Kent,

I was on a 757 about a year ago and I noticed that when we landed at our destination the thrust reversers weren’t used. I asked for a seat close to an engine because I like to see the thrust reversers deploy but it didn’t happen that day.

I thought that maybe there was something wrong with an engine but the flight crew didn’t mention anything so I lingered around the gate to see if a maintenance truck would pull up to the plane but that didn’t happen either.

Someone told me that maybe it had something to do with noise abatement, but it was about 5 or 6pm.

Can you think of any other reason why the thrust reversers may not have been used?

Hi Alex,

Great question.

There are a few airports–Manchester, England comes to mind–that restrict the use of thrust reversers early in the morning or late at night.

But I suspect that wasn’t the case on your flight. I’ll let you in on a little secret.

Occasionally, if a pilot touches down early enough on the runway and the point at which we plan to exit is a ways down field, we’ll consider NOT using any reverse thrust. Usually, however, we’ll do this by opening the reverser blocker doors, but not adding thrust to stop the aircraft.

Why, you ask?

Because we’re vain. Passengers tend to think it was a smoother landing if we avoid following up a nice touchdown with the noise and shake associated with the reverse thrust.

So there you go. Vanity!

Marius asks:

Does it take a lot of force to advance the throttles and yoke or can you hardly feel them at all?

And would you prefer a sidestick to yoke?

The throttles on the 767 are rather stiff. Most of the other Boeing aircraft have throttles that move back and forth rather smoothly, with little or no resistance.

Each airplane has a different ‘feel’ on the yoke (control wheel). Some are rather heavy, like the 757, and some are light, such as the A300.

The A320 and later Airbuses have a side-mounted stick. I can’t tell you what it’s like to fly this type of stick, since I’ve only flown Boeings and the MD-80, but I really would like to give it a try.

One interesting thing about the Airbus side sticks; they aren’t interconnected between the captain and the co-pilot. So when you move one side stick, the other one doesn’t move.

If the captain pushes full down and the co-pilot pulls full back, the inputs cancel each other out.

The yokes on Boeing aircraft move together, so it does give you an idea what the other guy is doing when they’re flying.

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 Friday’s Plane Answers feature.

Plane Answers: Runway numbers, climbs and descents, becoming a pilot

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!

Dave asks:

I am a frequent flyer on several airlines (SW, UAL, Alaska). I have been flying for 25 years but always wondered about the runway numbers. I am not a pilot, but I thought the numbers had something to do with compass readings. 14L was 140 degrees. Is that correct? If I’m wrong, what do they mean?

You’re absolutely right, Dave. The magnetic headings, minus the last digit, represent the runway number. So yes, runway 14 may be 143 degrees.

If there are parallel runways, they’ll name the left one 14L and the right one 14R. If there are three it’s usually 14L,C & R. And sometimes they’ll have a parallel that’s organized for example like Miami, as 8L, 8R, and 9, even though they’re all the same direction. 9 just happens to be further away and south of the terminal.

These same runways are named 27, 26L, and 26R going in the opposite direction. Also, contrary to what you might see on TV and in the movies, we call them two-six right and not twenty-six right.
Herbert asked:

I used to work for an airline, so I’ve done a lot of travel. But there’s one thing that I’ve never understood: What determines your rate of descent and speed? The same for take off, do you climb at the fastest safe speed at the highest rate of ascent? Does it save gas by getting to cruise level quickly or slowly?

We descend either at the airspeed ATC assigns us or the speed that the FMS computer calculates is the most economical, or at whatever speed we feel is a good compromise between on-time performance and fuel savings. Once we’ve decided on that speed, to start the descent the throttles are closed and we will come down at whatever rate, say 1500-3000 feet per minute, that the selected airspeed gives us.

Climbing is almost the same. We set the power at the maximum climb thrust, adjust the airspeed for efficiency or timeliness and we then climb at a rate of 1000 to 5000 feet per minute to our most efficient altitude, or whatever flight level ATC assigns us.

Getting to that cruise level as soon as possible and staying there as long as possible before starting our descent is the most efficient way to fly, generally.

Jean asks:

Hi Kent,

I’m 34 years-old with five children and it is my dream to become a commercial pilot. How can a man like me with no money accomplish my goal?

That’s a tough one, Jean. There’s no way to do it without any money unless you go the military route, and your age disqualifies you for that.

That said, I’ve had friends who were rather broke but they managed to fly a few hours every week to earn their private pilot’s license. They were still in college and managed to starve a bit in the process, though.

For them, it was possible to share the aircraft rental costs with friends and worked toward their commercial and flight instructor ratings.

After acquiring their instructor ratings, at least they didn’t have to pay to fly. In fact, flight instructors can make around $20 to $40 per flight hour. If you reach this milestone, you may be able to instruct on the weekends if you’re lucky to find a small airport nearby that offers flight training. After that, it’s a matter of building flight time and gaining some multi-engine experience (perhaps as an instructor) before landing a job at a commercial operator, whether that’s at a corporate flight department, a small freight operation or a regional airline.

This is the most common civilian route. Others have had good luck towing banners or flying traffic report aircraft for radio stations.

Like many career paths today, it’s not easy to land a job right away. And with the industry concentrating on shrinking to survive, now isn’t the best environment. And you might get stuck along the way either at the flight instructor level, or in a time-building job that doesn’t pay well.

But surely the hiring will turn around and you could be in a position to advance if that’s the case. You’ll have to take it step-by-step, but I assure you, each step along the way can be fun.

As for your age, I did talk about this a few months ago. I’ve heard stories of people learning to fly well into their 30’s who ended up at the airlines. And now that the mandatory retirement age has changed from 60 to 65, you’re effectively five years younger.

If you still want to do it, the first step is to check out this site: www.beapilot.com

Good luck!

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 Friday’s Plane Answers feature.