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!

I get a lot of question about the specific details or features of airplanes. I thought I'd round up a few for today's Plane Answers.

Kevin asks:

I fly on A319 and A320s a lot. As we are on landing approach I hear three shrill tones or whistles from the cockpit. Sometimes it is close to the runway sometimes not. What is it?

Hi Kevin,

I checked with my friend Chris, who's an A320 pilot who has a good answer for what's causing the noise.

He's most likely hearing the autopilot disconnect siren. It has a two-tone chime that repeats three times. It's loud enough to easily be heard in first class and sometimes the first couple of rows in coach. A lot of pilots will allow the AP to trim up the aircraft after all the configuration changes before disconnecting the autopilot. That is why he hears it at about 1000-1500 feet on visual days.

The other possibility is the flight attendant call tone. It wouldn't happen close to the runway, but it's so loud that it blocks all other noises–including master caution warnings. They're trying to get Airbus to turn it down a bit.

I've often heard the altitude callouts on the MD-80 from first class. "50, 40, 30, 20, 10." It seems if passengers can hear it in the cabin, then maybe it's just a little too loud. Unfortunately, we don't have any control over the volume. Thanks Chris for the A320 insight.

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!

Deb asks:

Are there any favorite/hated runways by pilots? Pictures and videos of the one in St. Maarten made me wonder.

I'm sure every pilot has a few favorite or hated runways, and I'm no exception. Here are my top and bottom three:


LGA – New York's LaGuardia

With it's reputation for delays and cancellations, LGA might not be on the top of most passengers' lists. But it's often the challenging runways that are the most enjoyable for pilots. While LaGuardia's runway 13/31 is short at just 7,003 feet, and it has water on both ends of the runway, the expressway visual takes you over the former Shea stadium and it requires some planning to make the sharp turn and perfectly line up on runway 31. But the most beautiful approach I've ever flown is the 'River Visual' up the Hudson to runway 13. Sailing past Manhattan at night, with the buildings seemingly at eye level, and then making a right turn over Central Park to line up with the runway, is certainly a rush.

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!

Ruthann, who's my proofreader for Cockpit Chronicles and this column asks a question about her recent Delta flight across the Atlantic:

About 15 or 20 minutes after departure from Shannon, there was a loud thump/bang/shudder. Not like an explosion or anything, but more mechanical, something falling/moving/colliding. We were sitting in row 26, right over the wing centre, on a 757-2.

Initially I thought, did we just lose a panel? But then I assumed it was more likely to be cargo shift. Something heavy. We were climbing at the time of course. It felt like it was right below us, or very close, but I'm not sure what the cargo layout is near that section with central fuel tank, etc?

My nervous-flyer mother had her headset on listening to music, but still heard it and wasn't too pleased. Luckily, I don't think she heard how loud it was. It bothered some other passengers, who asked the flight attendants, and I guess they mentioned it to the captain.

He made an announcement saying it had just been sudden, unexpected turbulence. He put on the seat-belt sign, but of course there was no sign of turbulence. It was just one single thump, but I don't suppose they heard it up front, either way.

I had hoped to look at the aircraft when we landed to see if it could have been a panel, but it wasn't possible to see out of the airport terminal.

Is noisy cargo-shift common? What else could it be? How often do panels fall off/pop out? Can you hear them go from inside the cabin?

I assume the gear had been up too many minutes to blame any issues there, and I'm sure if there had been a problem with that, they would have mentioned it before approach/landing, wouldn't they?

How much do pilots not tell their passengers? Where do you draw the line? Do you ever get semi-decent ear/eye-witness reports from those in the cabin? Do you appreciate them? Remember the lady who failed to mention the little crack she spotted on boarding Aloha 243?

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.

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.

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?

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.

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.

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!

Richard asks a technical question:

I have seen several photos of what I believe are later model 737s with what appears to be a small drogue chute trailing off the top back of the vertical stabilizer. I have done a few searches on the internet about it but have never found anything explaining what this item is.

I had to check with my friend Tom, who is a Boeing test pilot. He explained that this drogue chute is actually a "Trailing Cone," which is often used in flight testing to accurately sense pressure experienced during various flight test conditions or maneuvers.

The cone stabilizes a plastic tube, which in turn conveys the sensed pressure information to the flight test instrumentation system. The pressure information must be taken at a significant distance away from the aircraft, so as to not have the pressure probe immersed in a disturbed flow field, which can occur if pressures are sensed too near the aircraft.

Usually the cone and tube are "reeled out" after takeoff, and reeled back in before landing. When being used in flight to provide accurate pressure information, the cone and tube are typically trailed behind the aircraft at distances of approximately 100 to 125 feet.


Wes asks:

My pilot on a 737 said on departure from Las Vegas that we were taking off in the opposite direction than normal. He said this was due to the following issues: it was hot and jet engines perform lower in high heat; the runway had a slight incline to it; and the plane was full. I was wondering if these were valid reasons to reverse the departure route on a runway. Thanks.

Welcome to Gadling's Friday 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!

Lee asks:

How is it that the plane stays straight as it's accelerating down the runway? Is there an actual "steering wheel" of sorts that one of the pilots steers? If so, is it an "art" or talent of such to keep the airplane straight?

On the captain's side of the airplane, next to his left knee is a 'tiller' that helps him steer the airplane at slow speeds-anything less than 40 knots or so. The captain will steer the airplane onto the runway and once it's aligned he'll take his hand off the tiller. Either he or the co-pilot will then make the takeoff using their rudder pedals.

Unlike the pedals found in your car a car, the rudder pedals on an airplane do three things. They allow a pilot to steer on the ground left and right, turning the nosewheel up to six degrees either way at full deflection. They also control the rudder, which is most essential when flying on one engine when pilots need to counter the yaw associated with an engine failure, or when landing in a crosswind when pilots will use the rudder to align the airplane with the runway just before touching down.