Plane Answers: Announcements from the captain and Denver turbulence

by Kent Wien on

Rich asks:

Hi Kent, I love your blog and it has really helped me to relax when flying. When I was a kid and used to fly it seemed as though the flight deck would regularly update passengers about what was going on with the trip, the plane, etc. Now it seems as though most of the time I hardly hear anything. It would be nice to know if there is some turbulence coming up or something like that. The best flight recently was an “Express” flight where the pilot told us on the ground that we would be having turbulence the first 30 minutes and then at about the hour and a half mark. It really helped us relax.

Hi Rich,

I once sat in the back of a United plane flying from Denver to Miami when the passenger next to me grabbed my arm during what I would consider light turbulence. As her fingernails dug into my skin, she explained to me how she’d feel so much more comfortable “if the pilot would just say something!”

It left an impression on me. At my airline those announcements are entirely up to the captain, although we’re highly encouraged to keep the passengers informed without being a nuisance. As a copilot, I’m limited to a subtle reminder every now and then about a possible PA, since it would be a bit out of line for me to start talking on behalf of the captain.

We’re given a flight plan before the flight that depicts the reported turbulence at each waypoint along the route of flight, and we could easily incorporate that into our pre-departure PA. Of course, we run the risk when getting specific about the ride to be completely wrong-I’ve run across many flights that were advertised as smooth, only to find light or moderate chop many times during the flight.

Based on the number of fear of flying questions we get, I’m convinced that at least 20% of the population is afraid to fly and I would love to make them more relaxed. A quick PA detailing the forecasted ride conditions along the route is a great idea and I may just do that when I upgrade to captain. It’s already part of our standard briefing to the flight attendants.

Recently we had a nervous passenger on board who really wasn’t interested in coming up to the cockpit. So, while still on the ground, I took the flight plan back to him and showed him the turbulence reports for our flight down to Aruba from Boston. His eyes immediately fixed on our first waypoint, Nantucket.

“Nantucket?” He said. “That’s near where JFK junior went down!”

So I’m not sure if I was able to help calm him much. But the advertised smooth ride proved accurate and he seemed happy upon deplaning in Aruba.

Rich goes on to ask another question:

Second, why does every landing and approach into Denver seem very sketchy? Every time I fly into that airport we seem to make a lot of turns and it feels as though we are either getting pushed out of the sky or the turbulence is so bad that it seems as though the plane would be hard to control. Is it the altitude or the mountains? Thanks again!

Good question. Since the wind typically goes from west to east across the country, when it hits the Rocky Mountains, it will create rough air on the east side of the range. Imagine a large rock in a river. The upstream portion of the water flowing over the rock is usually smooth, while downstream the flow of the water over the rock is disrupted.

Pilots and meteorologists call this turbulence wave action, and it can extend for hundreds of miles ‘downstream’ of a mountain range. In addition, closer toward the mountains, dangerous ‘rotors’ can form that are curving curls of airflow that pack a significant punch. Denver is far enough away to miss this kind of turbulence, but it still sees a good share of rough air.

On nearly every transcontinental flight, you’ll notice this same ‘wave action’ generated turbulence even up at the higher altitudes. It’s the most challenging area to find a smooth ride.

As far as the airplane being more difficult to control, it’s similar to driving on a gusty day. The hydraulically actuated flight controls make it easy to react to some of the gusts, but it’s still going to be bumpy. Next time you fly, notice how it usually gets smoother just before touchdown.

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 Answer’s Plane Answers. Check out his other blog, Cockpit Chronicles and travel along with him at work.

Plane Answers: Minimum fuel requirements and sudden drops inflight

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!

Frank asks:

Kent,

A couple of questions for you:

  • How much reserve fuel does your plane normally carry? For how many minutes of flight or miles?
  • Who decides how much extra fuel to carry, the captain, FO, company or else?
  • Do you have a way to check how much fuel the plane is consuming? My Altima has a nice gauge that lets me know that, I was wondering what a multi-million dollar aircraft might have?

Thanks Frank.

There’s been some attention in the press lately about some airlines cutting back on the extra fuel carried because of the extra expense in adding unnecessary weight to the airplane.

The FAA requires that domestic airlines carry enough fuel to continue to an alternate airport plus an additional 45 minutes after that. The alternate airport has to have good weather in the forecast.

Our flights have been averaging 70 minutes of additional fuel which works out to almost 500 miles. I can personally think of just a few times when we have been in a holding pattern and needed to divert because we were getting close to our minimum FAA fuel (45 minutes plus enough to get to our alternate airport). In two of those cases, we were allowed to land at our destination. At no time were we sweating the amount of fuel on board.

Before each flight, the captain reviews the fuel requirements, the fuel computed by the dispatcher and the weather at our destination and alternate airports. If he feels we need more, he’ll pick up the phone and ask for an extra one or two thousand pounds from the dispatcher. The fuel decision is up to the dispatcher and the captain, but I’ve never heard of a captain being refused an extra fuel request.

During the flight, we have a fuel log print-out that comes up via ACARS and looks like this:

This fuel plan shows the time and the amount of fuel we are computed to have at each waypoint. It takes into account the forecasted winds, the altitude we’ll be flying at and the weight of our aircraft.

We write down the time and actual fuel as we cross each waypoint. Typically we’ll be up or down a few hundred pounds and a couple of minutes. If there’s a significant difference, we’ll look into the cause and consider diverting if we feel it could be necessary. The company also tracks our fuel burn via automatic updates which are sent from the airplane to ground VHF radio stations and then forwarded to the dispatcher.

As for any fancy indications in the cockpit, we do have a gauge that shows the fuel flow in thousands of pounds for each engine. On a 757, they read around 4,000 lbs an hour for each engine at cruise.

Cassandra asks:

Here’s another question for you (again, hyped by the media!). Why is it they love to report when going through turbulence that the plane dropped 500 feet or 1,000 feet? How do they get this information anyway and come up with these numbers?

Is this even possible?

There is a propensity for passengers and the media to describe a rough flight in terms of how far the aircraft “dropped.” But as you suspected, planes don’t just drop. I’ve used the analogy in the past that it’s like driving in your car and suddenly finding yourself on an interstate two miles away.

The media and a few movies have reinforced this idea that airplanes can hit ‘air pockets’ and drop hundreds or thousands of feet.

As I mentioned in a previous Plane Answers post about turbulence, even during some of the roughest air, we don’t gain or lose altitude generally.

There is one exception, however. If an airliner were to get far too slow, the resulting recovery back to a safe airspeed would require an immediate descent.

And on a similar topic, Kat wonders:

Sometimes when we are cruising in the air, there are moments when its feels like we have dropped a little bit and you get that roller coaster feeling and my stomach moves into my throat a little bit. Is that just the pilot maintaining our altitude? Is it supposed to happen? It’s scary sometimes because it can be a lot or very small–and yes I am one those people who are afraid of flying.

As we get to the higher altitudes, the flight controls are a bit more sensitive. So if a pilot is flying without the autopilot, the movements can be exaggerated, especially for passengers riding in the back. The autopilot can occasionally have some minor oscillations when it’s trying to level off or maintain altitude.

Imagine how smooth a road would have to be to drive a car at 500 to 600 miles per hour. Even the slightest change in the pitch of an aircraft will tend to make your stomach queasy.

Occasionally we’ll also get some oscillations when we approach a turbulent area. As the speed of the airplane increases or decreases when approaching changing weather, the autopilot adjusts to maintain altitude. This causes some very short climbs or descents of just a few feet that you’ll feel in your stomach.

As I’m sure you know, these movements aren’t dangerous for the airplane, but they can certainly be annoying. It’s just another reason everyone should keep their seat belts fastened while seated.


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 to travel along with him at work.