Plane Answers: Takeoff speeds, weights and lavatory drains

by Kent Wien on

We’re combining five questions that were recently submitted for Plane Answers. We’ll look into who foots the hotel bill for a crew’s layover, what is the typical speed and weight at takeoff, how pilots line up with a runway visually and where does that lavatory sink water go inflight?

When pilots layover for a night before returning home, who picks up the bill?

The airline picks up the tab for each crewmember’s hotel room. Meals are up to the employee, although often there’s a small per diem of about $2 an hour that’s paid by the company to cover these expenses.

I’ve always wondered what’s the ideal speed for a plane like a 737 to takeoff.

The takeoff speed is based on the weight of the airplane which varies. But you can think of it as a speed between 135 and 155 knots or so. Add 15% to convert knots to m.p.h. and you’ll have a liftoff speed of around 155 to 178 m.p.h.

What is the maximum weight that the average passenger plane (737,757 etc.) can carry and be able to takeoff and remain airborne? As a frequent flyer, I become concerned when I observe a number of 300 pound passengers boarding; and then there’s the cargo below. On occasion, I have been on a plane where the weight load was so light, passengers were asked to shift around to balance the plane weight. Does the opposite ever occur?All U.S. airlines use an average passenger weight of 190 to 195 pounds depending on the time of year. In the FAA’s mind, people in the winter either put on weight after the holidays, or they just wear more clothing. The load planning computer is able to keep the weight distribution spread out evenly through the cabin for balance purposes. The cargo is weighed before it’s loaded on to the aircraft so we know that number to the exact pound.

All of this data is totaled and sent back to the pilots who make sure that the actual weight is below the maximum allowed either structurally by the airplane’s manufacturer, or below the maximum that the runway will allow based on the airplane’s performance and the outside temperature. As an example, a 757’s maximum takeoff weight, assuming it’s not limited by a shorter runway, is 250,000 pounds. It’s empty weight, without fuel or passengers, is around 130,000 pounds.

When flying the final approach visually, how do you line up the runway centerline visually?

It’s not unlike lining up a car when turning onto a road. Controllers usually give us an intercept angle of no more than 45 degrees or so, and it’s our job to join the imaginary extended centerline from the runway. Once on final, it’s not hard to see if you’re right or left of course. Small heading corrections using the ailerons to bank left or right and we’re perfectly lined up. We also use any available navigation aids (GPS, ILS, or Localizer) to cross check our position.

This is kind of a goofy question but I always wonder about it when I use the restroom on a plane. Why is the drain stopper always closed? I notice that when I drain the water in the sink there’s an “air” sound. Does it have to do with the air pressure in the plane?

The sink drain actually ‘vents’ out of a heated drain mast (to prevent it from freezing). If they left the plunger open, it would create a lot of noise, and use a tiny amount extra bleed air to pressurize the airplane, which I imagine would cause a small decrease in fuel economy.

I took this video that shows a 777 inflight when someone is draining the sink. Take a look–It’s at the 1:14 point:


Have you ever been curious about what goes on at the pointy end of an airplane? Ask Kent and maybe he’ll use your question for next Friday’s Plane Answers feature.

Plane Answers: When are pilots afraid of turbulence?

by Kent Wien on

Welcome to 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!

Kyle writes:

First of all, thanks for taking the time to respond to people’s questions. There’s something I’ve always wanted to know. Do pilots ever get scared of turbulence? If so, what makes them bad enough to actually be scary. Is there a way a passenger can know when to be concerned and when it’s just normal bumps and shakes?

Thanks, Kyle.

Turbulence is more annoying than frightening, usually. But I think it’s more upsetting for passengers than some pilots realize.

I learned a good lesson when flying as a passenger some years ago. I was sitting next to a really nice lady who had previously worked as an agent for another airline. She had obviously flown a great deal, but she startled me when she grabbed my arm as soon as the airplane hit the slightest bit of light chop (pilot-speak for small rhythmic bumps). She said to me, “If the pilots would just ACKNOWLEDGE this turbulence–if they would just say something, I’d feel so much better.”

That moment stuck with me. As a co-pilot, it’s not really my place to make reassuring PAs–that’s up to the captain–but I will do my best when I move to the left seat.

Turbulence becomes worrisome to a pilot when it could cause harm to our flight attendants or passengers who aren’t buckled in. That’s our biggest concern. I’m very confident that the airplane will hold up to the roughest of air, but we just don’t want anyone to get hurt. Take a look at this Boeing video showing the maximum inflight load the 777 will take before failing. The wing finally failed at 154% of the maximum rated load. The video that follows after the jump has to give you confidence in today’s airliners.

Often though, pilots might not realize just how bad it is for the flight attendants in the back. When flying on the longer airliners, the ride in the cockpit can feel like light chop, while conditions in the aft galley make it impossible to stand up. The next time you fly, see if you can tell the difference with the flight attendants working in first class versus those in the back during a bumpy period.

Moderate turbulence is strong enough to move things around in the cabin. As a test, you can set a cup or glass on your table. If it gets knocked off–and not just small sliding movements that take it over the edge–then you are likely experiencing moderate turbulence. You’d feel a definite strain against your seat belt. If we encounter this kind of ride, be assured that we’re talking to air traffic control or other airplanes to try and find a smoother altitude. This would be a good time to mention how important it is to wear your seatbelt when seated.

Pilots don’t like these bumps any more than passengers do, but they’re generally not something that cause us to be frightened. That said, we always have a healthy appreciation for the turbulence that thunderstorms are capable of, so we strive to avoid them by at least 20 miles. Fortunately, these cumulonimbus clouds are relatively easy to spot on our weather radar. But don’t be too concerned about flying into the puffy cumulous clouds that have little vertical development. These clouds don’t show up on our radar and pose little problems other than light chop or turbulence.

We also rely on pilot reports from other aircraft in the area to keep us away from any clear air turbulence. Over the North Atlantic, we monitor a pilot-to-pilot frequency that allows us to give some warning to flights behind us when we enter areas of unforecasted turbulence. When flying in the domestic U.S. we rely on Air Traffic Control to let us know where the smoothest rides may be.

Have you ever been curious about what goes on at the pointy end of an airplane? Ask Kent and maybe he’ll use your question for next Friday’s Plane Answers feature.

Plane Answers: When do pilots use the autopilot?

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!

Justin asks:

My question concerns the autopilot. During the course of a flight how often is it used? Are there times where it can not be used because of heavy turbulence and other weather phenomenon?

Great question, Justin.

First, I should describe the autopilot system in a jet. It’s essentially a device that a pilot will program to climb, descend or hold an altitude while following a specified route of flight. The system also includes autothrottles, which maintain the speed of the airplane in cruise and adjust the power automatically for climbs and descents.
The autopilot in an airliner is really analogous to the cruise control feature in your car. Just as you wouldn’t use your cruise control when leaving your driveway, we never use the autopilot for takeoff. In fact, there’s a limitation on the 757 and 767 that doesn’t allow the autopilot to be used below 1000 feet, after takeoff. Above that and it’s the flying pilot’s option if they’d like to use it.

I usually prefer to ‘hand-fly’ the airplane to about 18,000 feet before turning on the autopilot. We generally don’t hand-fly after leveling as it becomes rather tedious after a while. And one sudden push of the yoke would cause the passengers to float toward the ceiling. Some airlines charge for this weightless experience, but our passengers tend to prefer a straight and level ride.

Some pilots will bring the autopilot on right after takeoff, and again, that’s their option. When I first started flying commercially, we tooled around in a commuter airplane that didn’t have an autopilot, so I sometimes crave a little stick and rudder time.

But there are times when the other pilot is busy making the PA or talking on the radio and you need to take a closer look at the weather radar up ahead or you’re trying to decide what the best cruise altitude will be. In these cases, the moment you start getting busy, it’s a good idea to get the autopilot on to reduce the workload for you and the non-flying pilot.

Some airplanes (I’m looking at you, 737-800) have a tendency to hunt or oscillate during climbs and especially descents. The airplane will go from 500 feet per minute down to 2500 feet per minute and back again before eventually stabilizing. This makes for a rather uncomfortable ride in the back and it’s probably why many 737 pilots prefer to hand-fly most of the climbs and descents.

The autopilot can handle a significant amount of turbulence. There’s no requirement to turn it off during the bumps, but if you feel it’s not doing an effective job at holding an altitude or airspeed, then you’re encouraged to ‘click it off’ using a thumb activated button on the control yoke and fly the airplane yourself.

There are times when the weather is below a certain level of visibility where airplanes must be flown using the autopilot. If the visibility is less than 1800 feet (550 meters) and the airport has the capability, we will still be able to land using the autopilot. In fact, the 757, 767 and the 777 can be flown down to a visibility of 300 feet (75 meters) with touchdown occurring without actually seeing the runway.

When we print out the current weather and it reports a low enough visibility to require an autoland you can just about read the disappointment on the flying pilot’s face. Hand-flying the landing is the icing on the cake for pilots, and to fly all the way across the country only to be denied a landing takes some of the fun out of coming to work.

These autolandings (known as Cat III approaches in pilot-speak) also require more setup to fly, and a significant amount of monitoring to be sure the airplane is tracking correctly. We don’t have to fly them very often–I think I only had two autolandings last year.

Have you ever been curious about what goes on at the pointy end of an airplane? Ask Kent and maybe he’ll use your question for next Friday’s Plane Answers feature.

Plane Answers: How close are airliners allowed to fly?

by Kent Wien on

Welcome to 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!

This question was submitted by Jim,

Hi Kent,

My question concerns how much advance notice pilots get when there are other planes in their immediate air space. In some of my travels, while at cruising altitude, I’ve seen other planes cross paths just below us. Knowing how many planes fill the sky each day and knowing that your reaction time is minimal, I wonder how pilots and controllers work together to keep all those planes apart. Also, what’s the rule on how much distance must there be between planes when on the same route and at intersection points?Thanks Jim,

I know it can be a little disconcerting to see another airplane cross under or zip by overhead just as you look out the window of an airliner.

Air traffic controllers have rules on how far laterally they must keep airplanes apart as well as how much vertical space needs to be kept between them.

For lateral separation, airplanes that are en route–flying faster and further away from the ATC facility–must have at least 5 nautical miles between them. When the airplanes enter the approach controller’s airspace, that requirement goes down to 3 nautical miles. Finally, when the airplane is in the control of an airport’s tower controller, aircraft can be spaced much closer if that controller has visual contact with the airplanes or if at least one pilot reports they have the other aircraft in sight. A good example of this is the visual approaches to San Francisco where airplanes are lined up on final approach for the parallel runways. You would think the airplanes are flying in formation at times.

This visual separation doesn’t apply when airplanes are in the clouds, in which case the controllers keep airplanes spaced about 2 1/2 NM apart, more if the preceding aircraft is a heavy (over 250,000 pounds–757 or larger) and the following aircraft is not. This limitation is a function of the wake turbulence generated by larger airplanes.

But I suspect the airplanes that you’ve been seeing lately have been even closer laterally than that. Because of some technology improvements to corporate jets and airliners, most of the world has adopted the Reduced Vertical Separation Minima (RVSM) standards. This allows aircraft flying above 29,000 feet to be spaced at 1,000 foot intervals. In the past, that number was 2,000 feet apart.

This has actually had the effect of doubling our airspace above 29,000 feet, which allows for more direct routing and the ability for us to get out of annoying areas of turbulence.

Westbound aircraft are normally put at the even flight levels (altitudes) and eastbound aircraft fly at the odd levels. That doesn’t apply to the North Atlantic, where most of the traffic flies westbound in the morning and eastbound in the afternoon. In that case, airplanes are spaced 1000 feet apart which makes for some great views from our seat as you can see from the following video clip:


Have a question for Kent? Ask away and he’ll pick one to answer here on Friday.

Plane Answers: “When did first class become the crew lounge?”

by Kent Wien on

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

Dennis asks:

As one who travels somewhat frequently for business and pleasure, I have taken notice recently of just how pervasive it has become for United Airlines (the carrier I usually fly) to seat airline employees dressed in full uniform (most probably dead heading to the next hub) in the First Class cabin, even though in many cases there are ample seats available in economy. Somehow I get a little offended by this. At the very least, wouldn’t it be a show of goodwill if space is indeed available to upgrade paying customers at the gate and let the crew sit in back? Is this a common practice amongst all airlines? What are your comments on this topic?

Thanks for the question, Dennis.

While I can’t speak for United Airlines, I can give a little background on this practice as it relates to my airline. Employees have negotiated improvements to their benefits as they relate to non-revenue travel and deadheading while at work.
For us, non-revenue coach travel is free for employees with at least five years of employment. If the employee would like to travel in first class, a fee is assessed. In either case, the employee is responsible for the taxes normally applied to airline tickets as well as a separate income tax on this benefit.

Deadheading employees are often used to fill gaps in coverage at other bases or if one of their legs of a trip has cancelled. These employees can put themselves on the upgrade list online or while at the gate.

In both of the above cases, crews are offered seats up front only after all first class revenue passengers and frequent flyer upgrade requests have been met. These seats would have otherwise gone unfilled. Pilots and flight attendant unions often negotiate these benefits, and airlines are willing to use them to attract new employees.

I discussed this policy with a gate agent today and she explained that some confusion occurs when passengers that request to use an upgrade voucher give up and decide to take their originally assigned coach seat during the boarding process. Usually the agents wait for no-show passengers before processing the upgrade requests, and if a passenger elects to take their seat in the back they’re unable to go on board and move that passenger up to first class.

Airlines are hesitant to upgrade coach passengers even with empty seats in first class probably because they don’t want remove any incentive for travelers to pay for that premium seat.

Employees have sacrificed their pay and work rules for the past seven years–often helping their airlines pull through some tough times. I hope you don’t fault them if they’re sitting in an otherwise unused first class seat every now and then.

On a somewhat related note, my Irish friend Ruthann provided me with a story that might just work for you if you’re out of upgrade vouchers:

Several years ago, a sales department (frequent travelling) co-worker of mine was passing through LAX on his way back to Ireland when he decided to try his chances with the AA desk clerk and charm her with his Irishy Irishness. He put on his best leipreachán accent and requested an upgrade to first class.

The lady seemed to flirt with him, and was very happy to upgrade the remainder of his trip to first class for free. It was love at first sight, at least for her. He promised her the world, being the funny, jokey charmer that he is. He came back and boasted to us all about the AA clerk he’d charmed into a free upgrade.

A few days later, he got a long distance call. She had kept his info and phoned him, just to see if he got to Ireland safely…

Several years later and they’re due to get married soon.

So there you go. But you might want to proceed with caution if you don’t have the requisite Irish Irishyness!