Plane Answers: Why can’t airlines wait at the gate vs. in a queue on the taxiway?

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!

Mike asks:

Hello Kent,

There are times when I find myself on a plane that is waiting in the queue to depart and I wonder if this makes sense. After all, having 10 airplanes push from gates only to idle their engines for 20-30 minutes waiting to take off does not seem to be a good idea for an industry where fuel is the largest single cost.

Can you explain who decides when an aircraft pushes back and queues up to take off? Is there a reason that airplanes get in line to depart as opposed to just being assigned a number and waiting at the gate until it’s their turn (other than if the gate is needed for an arriving plane)?

It doesn’t really make sense, Mike. But some airports have adopted a gate hold program that does just what you’re talking about; hold airplanes at the gate until the line begins to clear out. London and Paris both use this technique. However, even after holding at the gate for 15 minutes to an hour, we still often find ourselves waiting in line for departure as we approach the runway. It’s simply a matter of the required spacing for departures combined with the number of flights scheduled to leave at the peak times that causes this.
There is also a concern by ATC that there may be no aircraft ready at the end of the runway for departure if they’re held at the gate at the last minute, which would result in even more inefficiency.

Other airports (especially in the U.S.) will advise flights of a ‘wheels up’ time, allowing the pilots to push back at their discretion as long as they can be ready by the time given by ATC. This works to some extent, but flight crews are paid only after they push back from the gate, so the incentive to begin taxiing early is something that admittedly factors into their decision.

To prevent this, our company has a system in place to start the pay clock for pilots and flight attendants once an ATC delay is given which, in theory, would eliminate this incentive. In practice, many pilots don’t trust the system to log the time or have been denied the extra pay in the past and would rather take the delay off the gate – possibly to an area where ATC will allow them to shut down the engines.

Richard Branson at Virgin made an attempt to think outside the box and looked into a tug system that could tow the airplanes to the end of the runway. Such a system could have saved hundreds of pounds of fuel per flight. Unfortunately, it was discovered that the extra wear and tear on the nose wheel would cost more than the savings generated by the reduced fuel burn.

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: A heavy question

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!

Ken asks:

I hope this is the appropriate place to ask this question.

Why do some aircraft identify themselves as “heavy” on the radio? Does this refer to its size or load? Why is it important to so identify?

Thanks Ken,

It’s the perfect place to ask, actually. The “heavy” designator is attached to aircraft that weigh over 255,000 pounds in the U.S. This term informs the controllers to add spacing between heavy aircraft and non-heavy types since the heavier aircraft create their own turbulence which can be rather dangerous to smaller airplanes spaced too closely.

A vortex is generated from the wingtips of high gross-weight airplanes and is known as ‘wake turbulence.’

It has become a bit more confusing for air traffic controllers lately, since some 757s have been modified to allow for a heavier gross weight takeoff. These 255,500 pound gross weight capable airplanes are now full fledged ‘heavy’ aircraft with spacing requirements that are the same as a 747..

I had no idea just how complicated the spacing criteria could be until I posed the question to Dayron Fernandez who works at the Miami tower.

Read on to hear Dayron explain just what is involved for an air traffic controller when dealing with the different types of aircraft:
Required radar separation minima is 3nm for all IFR [instrument flight rules] aircraft in a terminal environment. In other words, say, with Miami Approach.

In the center environment [en route] it is 5nm for all IFR aircraft. Since the Centers have everyone separated by 5nm, wake turbulence doesn’t apply and so they don’t use the “heavy” designator behind the call sign in the U.S.

In the terminal area, we can use a reduced separation because our radars sweep faster, and since the separation is down to 3nm, wake turbulence rules apply. So here they are:

  • Any IFR (non-heavy) aircraft behind a Heavy : 5nm
  • Heavy IFR behind Heavy IFR : 4nm
  • Any large or heavy IFR aircraft behind a B757: 4nm
  • Any Small IFR (PA28, SW4 etc) behind B757: 4nm
  • Any IFR behind any other IFR aircraft: 3nm

The increased separation applies only to those aircraft following Heavy or B757 aircraft.

And just when it couldn’t get any more complex, because the effects of wake increase as airplanes fly slower and the AOA [angle of attack] increases:

  • Small landing behind a Heavy: 6nm
  • Small landing behind a B757: 5nm
  • Small landing behind a Large: 4nm

As you are aware, for departures we use 2 minutes behind heavy or even the non-heavy 757s OR we can use radar separation. For the latter, what counts is that the wake separation exists at the time the trailing aircraft becomes airborne. (i.e. 5nm) For both landing and departing traffic we must issue cautionary advisories to aircraft departing/ arriving behind any heavy or any 757.

The FAA weight cutoff for a heavy is 255k. However, ICAO uses 300k. Thus the increased gross weight of some of the B757s brings it above 255,000 pounds but sits below ICAO’s standard.

So we now have to wonder which 757 we’re dealing with. And what’s more, since we now file flight plans in ICAO format, and they don’t recognize that weight class as heavy, pilots/dispatchers can’t file these larger 757s as heavies, so we manually have to make that change in our host computers for every H/B757 flight.

Times Square becomes a pedestrian zone

by Sean McLachlan on

New York City’s famous Times Square became free of cars this Monday.

This is the latest in two decades of radical changes to what used to be a dirty, dangerous, but uniquely vibrant part of one of the world’s greatest cities. City officials have blocked traffic from 42nd to 47th Streets at Times Square and between 33rd and 35th Streets at Herald Square in a much-anticipated move we first reported on back in February.

The traffic jams are being replaced by pedestrian plazas and more shops. The hope is to attract even more visitors to New York City’s iconic square by getting rid of noise, pollution, and frequent accidents. New Yorkers celebrated Monday with a big block party and setting up lawn chairs in the middle of the road. The city plans to have various events and street performers every night in the coming weeks to attract more people to Times Square.

Old-time New Yorkers like yours truly have fond memories of the old Times Square, full of seedy bars, seedier adult shops, and crumbling movie houses where you could watch a double feature of martial arts films for two bucks. I saw my first Jackie Chan film in Times Square, my first zombie picture, not to mention countless Z-list action flicks. Ah, the Eighties!

But not everyone liked Times Square at its decadent best. It was too close to Broadway, where accountants from Omaha wanted to see musicals without being reminded that the world isn’t like it is in A Chorus Line.

First to go were the movie theaters, replaced one by one by adult video centers, as if the area didn’t have enough of those already. No more blaxplotation or ninja flicks, just hard core. Then the porn shops got shut down. Times Square began to look like Disneyland. Now the squalling, bumper-to-bumper traffic has gone the way of the dodo. The armpit of New York has been replaced with the outdoor equivalent of a shopping mall. Progress? Well, it’s certainly safer (how I survived my teen-aged trips to the old Times Square still amazes me) but I can’t help but think that by killing Times Square, New York City has lost something.

Every city has its grotty area. Amsterdam has its red light district, London has Elephant and Castle, and New York had Times Square. The thing is, these neighborhoods are often really interesting and alive. The red light district in Amsterdam has some of the city’s best architecture. Elephant and Castle has an amazing variety of African shops and restaurants. Times Square has. . .well, had. . .an exciting street life and a variety of movie houses for every taste. And no, I’m not talking about the adult stuff. Back in the day, all sorts of people went to Times Square, everyone from well-heeled businessmen up to no good, to curious teenagers like I was, all the way down to street hustlers and petty thieves. That’s what I liked about it. Now it’s tourists and the middle class. Aren’t there enough places like that?

Any other old-time New Yorkers out there have any thoughts on this?

Memorial Day travel surge to be followed by silence

by Tom Johansmeyer on

So, there are two visions of the near future: one immediate, the other a bit further out. For Memorial Day, expect to see plenty of traffic, thanks to a drop in gas prices, according to AAA. More than 10 percent of the country’s population – north of 32 million people – is expected to ht the road (though some will take planes). This stands in stark contrast to last year, when it cost $4 to put a gallon of gas in your car.

But, the fun will end when the summer starts.

An estimated 20 million fewer trips will be taken this summer compared to last year – which translates to $43 billion less in travel spending. According to a recent poll by AP-GfK, a third of Americans have already canceled at least one trip this year as a result of the ongoing financial calamity. Only 42 percent of us are going to take a leisure trip this year, down from 49 percent in a similar poll conducted in May 2005.

Apparently … brace yourself … income is a factor. Two-thirds of people making more than $100,000 a year are expected to take some kind of recreational trip this summer. If you make $50,000 to $100,000, the chances are around 50-50. Only a third of people making less than $50,000 a year are likely to hit the road (all incomes based on family, rather than individual).

Grim? It gets worse.

Twelve percent of those traveling are staying in their home states, with 67 percent venturing across state lines and only 19 percent leaving the country. Twenty percent are staying close to home for financial reasons, and 23 percent will save a few bucks by staying with friends or family.

Plane Answers: Cockpit jumpseat etiquette and inefficient arrivals

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!

David asks:

Hi Kent,

While riding in the jump seat do you ever double check what the PIC and SIC are doing? Have you ever seen something that you would have done differently and pointed it out? I know the cockpit is supposed to be sterile below 10,000 ft but have you ever said something or pointed out a checklist item that might have been overlooked?

When we have jumpseaters we almost always mention to them that if they see anything out of the ordinary, speak up. You’d be surprised at the things you can see sitting further away from the instrument panel. An extra set of eyes are always welcome.

Most of these items aren’t safety related, so I’ll usually stay quiet unless something could pose a problem later. But I wouldn’t hesitate to say something even below 10,000 feet (the sterile period) and I’d hope another jumpseater would feel the same way when sitting behind me.

Anthony asks:

Hi Kent,

I enjoy your blog and try to visit regularly. I have a question about standard arrival procedures (STARs?). They seem to add quite a bit of time to the flight as you go all over the place before finally lining up and landing. I have been told that in the early days of jets, pilots would simply throttle back the engines and descend at a fairly high rate with the engines at idle giving a faster trip.

Given that you often hear of a departure being delayed because of flow control (it even happens on trans-continental flights here in Australia), why can’t the flow control be more precisely devised for quicker arrivals like the old days?

Is this what is being planned with the trials by Air New Zealand, Qantas and United flying from the South Pacific into California?
Hi Anthony,

We often wonder about the reasons for the extended vectors around populated areas at major airports.

They tell us that in order to sequence a number of flights into an airport with multiple runways, it’s becoming necessary to have ‘corner posts’ or other waypoints around the airport that allow for the proper alignment and spacing at an airport.

We still fly to many airports with very little traffic. When flying into Shannon, Ireland or some of the Caribbean airports, we’re often able to descend at the most efficient angle (which, like you described, is done with an idle descent at the latest possible point) resulting in significant fuel savings.

Flying into the New York airports or any other high density terminal areas usually requires an airplane to descend earlier while being ‘vectored’ by ATC to get around departing aircraft from other airports. Prior to that, aircraft are sequenced well in advance to avoid a saturation of arrivals at the same moment.

I’d love to understand more about it, but as pilots, we don’t always have the big picture as it relates to multiple airports with multiple departures and arrivals.

In the U.S. there’s a lot of talk about an ATC program called “NextGen” which promises to allow for more efficient flight plans. Let’s hope so.

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.