Plane Answers: Who sets crew rest rules and are MD-80s safe?

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:

Are commercial airline pilots allowed to be flying for up to a maximum number of hours by FAA, or is this at the discretion of the airline they are flying for?

The FAA allows a two-pilot aircraft to be scheduled to fly for up to 8 hours. This is flight time only and doesn’t include any time waiting between flights or getting ready. The duty-day, or the time a pilot can be on duty is sixteen hours, but some airlines have rules, often negotiated by their unions for thirteen or fourteen hour days.

When an extra ‘relief’ pilot is added for a total of three pilots, the flight time can increase to a scheduled 12 hours with a total duty time of 18 hours.

Finally, if four pilots are aboard, the scheduled flight time can be up to 16 hours and the duty time up to 20 hours.

There are other rules designed to keep fatigue out of the cockpit; no more than six days on duty without a full day off, no more than 30 hours of flight time in a week (32 hours for international flights) and no more than 100 hours of flying a month (120 hours for international pilots).

One exception: The FAA has established different flight and duty time regulations for the state of Alaska.

Many of these regulations are likely to change in the next year. The FAA has announced plans to review these regulations and to update them as a result of new alertness studies and last year’s incident in Hawaii where both pilots fell asleep after flying a rather brutal schedule.

Joe asks:

Hi Kent,

I love your site and visit often. I have a question about the MD-80 series airplane. When I was a child, my Mom missed Northwest flight 255.

Her Physician was not so lucky. Ever since that incident, I have been terrified to fly on the MD-80 and have not flown on one! I realize they are very popular and have a fairly good safety record, but I prefer the Airbus 320/321, 737, 757 and the ultimate – 767 for my travels. How do you feel about the MD-80s? Are they a more difficult airplane to fly? I ask because I will be flying on an AA MD-80 in September and I’m very nervous about it. Keep up the Plane Answers! I love them!

PS – Took your advice after watching the DA20 video – After 31 years on this earth and 11 years of police work, I finally have saved the $ to chase that pilot’s license!
Wow, congratulations Joe. One of my primary flight instructors was a police officer, in fact. I’m sure you’re going to love flight training.

I flew the MD-80 for only a year, but I remember it to be a safe airplane that does well in a crosswind, has a reasonable approach speed and isn’t lacking in performance. The technology in other airplanes has improved and the MD-80 has been retrofitted with some of those same features such as GPS and an EFIS (electronic flight instrument system) display.

There isn’t a quieter airplane for those sitting in the front of an MD-80. In the descent, at less than 250 knots, it’s as if you’re flying a glider. It’s not very difficult to fly and it doesn’t rely on any fly-by-wire system for the flight controls.

The NW255 accident was caused by a failure of the pilots to conduct a before takeoff checklist that, among other things, assured the flaps and slats were extended. Contributing to the accident was a failed takeoff warning horn that had a tripped circuit breaker preventing it from working.

Today, we have a checklist (at American it’s a mechanical checklist that’s hard to miss, the importance of which is drilled into every aviator’s head from the beginning of their career. I realize how close to home, so to speak, this occurred for you, but I think you can feel safe on an MD-80. I’m even considering upgrading to it when I have the seniority for captain.

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

Plane Answers: Zeroing in on a few airplane systems

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!

Jason asks:

On a recent round trip on board 757-200s, when we would descend there was a sound like air leaking out of a tire coming from the engine area. It would last from 1-3 minutes in some cases or a matter of seconds at other times. What causes this noise?

Air conditioning and pressurization on an airliner both originate from what’s called bleed-air that comes from the engines. On the 757, as the thrust is reduced to idle for descent, another valve opens allowing ‘high-stage’ bleed air to supplement the existing air.

This hot air is then run through air conditioning “packs” that heat or cool the cabin and provide pressurization.

You may have been hearing the rushing air associated with this valve.

Not being a mechanic, that’s the best explanation I can provide. Any mechanics out there want to tackle this one? Big Ed?

Michael asks:

While working, I flew Northwest from MSP to AMS monthly. When flying DC-10s, the cabin display showed the same flight level the captain reported – 35,000 feet = 35,000 feet. Now flying the A330, the captain reports 35,000 feet but the IFE reports something like 34,824 (a guess, not the actual number). Does the IFE not get its travel info from the plane’s instruments? Since FL350 is about 10,600 meters, does the IFE work in metric units (rounded to the nearest 100 meters) and convert to an exact English equivalent i.e. 34,777 feet?
On older aircraft such as the DC-10, I can’t recall where the inflight entertainment screen pulls the altitude information from, but the newer jets all use GPS data to display the altitude on the map back in the cabin. In addition to locating an airplane’s position on a map, the GPS can also compute an approximate altitude.

Since we refer to an altimeter in the cockpit that’s entirely based on air pressure, our version of 35,000 feet actually varies slightly depending on whether we’re flying through a low or high pressure area.

It’s not important that we’re exactly 35,000 feet above the ground, but it IS important that we’re using the same measurement as all the other aircraft. And this barometric altimeter is considered the most accurate way to establish our altitude relative to all other airplanes.

Down low (below 18,000 feet), we manually correct the altimeters for the variations in pressure with a small knob using a setting provided by air traffic control. This keeps us at a safe and known altitude above the terrain.

So you may notice that the altitude displayed in the cabin while in level flight below 18,000 feet is much closer to a given 1,000 foot measurement, such as 11,000 or 5,000 feet when temporarily leveling off during a climb or descent.

Michael goes on to ask:

Also, the system in the cockpit that warns of impending collision – does it work by getting transponder information from nearby aircraft or is the information derived from the ground? Over the mid-Atlantic, out of ground based radar coverage, is separation dependent on seperation leaving Canada and maintaining a constant Mach number or will the system warn if you are getting too close?

The TCAS system (Traffic Collision Avoidance System) works over the Atlantic, since it uses the transponder of each airplane to decide who, in the case of a controller or pilot mistake, needs to climb and who needs to descend to avoid a collision.

But you’ll almost never hear that warning over the Atlantic since the Gander (Newfoundland) and Shanwick (Shannon, Ireland and Prestwick, Scotland) controllers place aircraft on ‘tracks’ at a proper spacing and altitude that should stay relatively constant with an assigned speed for the crossing.

It’s far more common to receive a TCAS alert while flying domestically or while in Central or South America. And since the introduction of GPS, which has effectively reduced our airways from up to 8 miles wide to a much more narrow .1 of a mile wide due to vastly improved accuracy, TCAS has saved numerous lives already, usually without passengers even knowing it.

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

Plane Answers: How safe are oxygen generators and my dream airplane.

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!

Luke asks:

I happened to catch a show the other night about the oxygen generators used in planes. I know that this source of oxygen creates massive amounts of heat when in use. What are the precautions that are taken to insure that a generator will not accidentally activate during a routine flight and perhaps cause a fire? Plane Answers is awesome. Love Planes, but hate to fly.

Thanks for your time…

Thanks Luke.

I passed this question along to my friend Ed, in maintenance. He offers some pretty good insight into just how those oxygen generators work.

Here’s his take:

Well, first off the oxygen generators are installed above your seat in the overhead bin, and the mask doors are held in place electrically.

Now there are two ways they can be deployed; one way is through a decrease in cabin pressure, and the second method is to use a switch in the flight deck.

When the masks are deployed you pull on the mask and this action starts the flow of oxygen.

As you pull the mask there’s a lanyard or cable attached to a firing pin – when the cable is pulled out of its locked position the pin fires a primer, much like on a round of ammunition and this starts the chemical reaction with calcium carbonate which, when burned, produces oxygen.

Firing off the canister causes the temperature to reach around 500 degrees Fahrenheit, but the passengers are protected by the case around the canister. Of course by the time the canister has burned out the pilot will have brought the plane below 10,000 feet where there is no need for supplemental oxygen. As a side note, the canisters will burn about 30 minutes give or take a minute or two.

Thanks Ed! Great insight.

David asks:

Hi Kent,

Lovely post on the Paris Air Show, and it got me thinking. As a pilot in general, is there an airplane or class of airplane that you dream of flying?

And lastly, as a commercial pilot is there an airplane that you dream of flying regularly or are you pretty happy flying narrow-body Boeings?

Thanks David,

Without a doubt, the airplane I’ve been most excited about for more than a decade has been an experimental airplane called the Aircam. This experimental, kit-built airplane was originally designed for National Geographic to study the Ndoki rainforest over the Congo.

The Aircam’s spectacular view and short field performance along with its two engines, fuel systems and electrical systems make for the perfect airplane for me.

In fact, it’s my retirement dream:

As for which airliner I’d most like to fly, I must admit the Boeing 787 looks very appealing to me. With just the right amount of technology, such as a built in class three EFB (electronic flight bag) and HUD (head up display) as well as a completely new aircraft design that will have a more comfortable cabin with more humidity, who wouldn’t want to trade in their older Boeing to fly the Dreamliner?

I may even pass up a 737 captain position just to get the chance to fly the 787 as a co-pilot when my airline finally takes delivery of them.

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But I’d trade in the new and fresh smelling 787 for a chance to have flown Concorde regularly. (It’s such a special airplane that you’re not allowed to call it ‘the’ Concorde, but just Concorde). I had the opportunity to ride in the jumpseat of a British Airways Concorde while on a ferry flight from New York to Cincinnati and it left an impression, for sure. I told the pilots they weren’t flying an airplane, but that they flew a rocket.

But nothing really compares to the feeling a person can have while flying an Aircam. And on the day I retire, I look forward to upgrading to the Aircam, no matter what I’ll be flying prior to that.

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: Sudden acceleration on landing and lining up on final approach

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!

Darren from Engadget asks:

Hey Kent!

Just got back from a LIR -> ATL -> RDU trip, and I thought of a question. When the plane (we were on a 737) is just seconds from touching down on the runway, it feels & sounds like the plane suddenly accelerates. For a few minutes leading to landing, it feels like we’re slowing down, and right before the rubber hits the road, there’s like a small burst in speed, followed by touch down and then massive wind as I assume the engines are thrown in reverse to stop us.

So, what’s that acceleration just before touch down for? Or am I dreaming? Thanks!

Hi Darren,

Nope, I’m sure you experienced this.

Occasionally if a pilot is a bit slow (say 2 or 3 knots below your ‘target speed’) they can add a small boost of power in the flare to cushion the inevitable thump of a landing. But it’s really not a very good technique to use regularly.

And some pilots don’t just use it when they’re a tad slow, but they use it as a substitute for a finessed flare on every landing.

It can lead to a very ‘flat’ and fast landing. Touching down like this eats up a lot of runway unnecessarily and puts more wear on the brakes and tires.

You’ll hear in this takeoff and landing video the instructor repeat “flare and squeeze” to the captain as he’s about 30 feet over the runway. He’s telling him to start his flare, or round out the glide path angle to allow for a smoother touchdown and to “squeeze” or pull the power back to idle before touching down.

And you’re right, the noise you’re hearing after landing comes from the reverse thrust mechanism which is simply a set of ‘blocking doors’ that divert the thrust out the sides of the cowl and forward, angled away from the engines.
Ainsley asks:

How important is a reference point in lining up for landing?

Hi Ainsley,

If the weather is clear, we are often able to make up our own final approach to landing in, for example, the Caribbean. At densely populated areas and in the weather (flying on instruments) we fly an approach that usually has a straight-in segment of about 10 miles. We’re almost never turned in any closer than 3 miles out.

As you can see from the video linked in Darren’s question above, while on the final approach it’s easy to tell if you’re lined up correctly with the runway.

In San Juan, Puerto Rico, we line up for one runway (10) and in the last 300 feet make a turn to another runway (8) for landing. It’s a ‘charted’ visual approach procedure that’s rather fun.

The approach is similar to the ending of this video I took while flying in a small Diamond DA-20 airplane:

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.