Plane Answers: A pilot’s seatbelt sign philosophy and aircraft accident odds

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!

Caroline asks:

Can someone tell me why the pilot sometimes turns on the seatbelt sign but it’s seemingly for no reason? I recently flew Dubai to London and he (or she) kept putting it on however nothing happened. Especially annoying as I needed the bathroom at the time?

Hi Caroline,

There are a couple of possible explanations for a seatbelt sign that turns on and off frequently.

Occasionally we’ll get reports from airplanes in front of us warning of turbulence ahead. It’s best to get the seatbelt sign on if we get a report like this to prevent any injuries to passengers standing in the aisle.

Deciding when to turn the sign on after experiencing some un-forecasted and unreported bumps can be a challenge. Some pilots don’t mind turning the sign on and off as the conditions permit and some will turn it on, only to forget about the sign when the ride improves, thus making every passenger feel like a criminal for using the lavatory for the rest of the trip.

There are some pilots who are concerned enough about the liability involved when turning the sign off that they’ll insist on keeping it lit for the duration of the flight. This actually creates a riskier situation since passengers will disregard the sign, even during periods of turbulence, completely eliminating the point in having a sign in the first place.

There’s another explanation that might surprise you. Pilots have been known to get calls from flight attendants asking for the sign to be turned on so they don’t have to deal with people becoming stuck in an aisle between their carts or otherwise getting in the way of the service.

And occasionally there can be a rather large group of people congregating around the galleys chatting it up. One of the ways to disperse this crowd had been to use the seatbelt sign. This isn’t exactly what the sign was intended for, of course.

Jen asks:

Hi Kent,

In light of the Air France crash, I am curious to know if it is indeed true that passengers pass out first, due to loss of cabin pressure, even before a plane hits the water (assuming it didn’t explode in the air)?

What are the odds of this happening to me? Are the odds of this happening greater or less than winning the lottery?

P.S. This is my take: when I get on the plane, my odds are 50 / 50 : 50% chance that I live and 50% chance I don’t. (haha, ok, joking…)

Hi Jen,

If the flight were to depressurize, and assuming the passengers couldn’t get to their oxygen masks during the descent, then there is a limited amount of time until they will pass out. This time of useful consciousness varies depending on the altitude.

At FL350 (35,000 feet) that time is only 30 to 60 seconds. However if the airplane is descending rapidly, the lower altitude will likely wake people up.

It’s a morbid thought, for sure, but since you brought up statistics, let’s look at the odds of dying in an airline accident a moment.

According to the Insurance Information Institute, the odds of losing your life in any given year is 1 in 502,544 and over an entire lifetime, it drops down to 1 in 6,460.

That’s much better than the 1 in 84 odds over a lifetime that a person could be killed in an automobile accident. It seems to me the most effective way to save lives on a large scale would be to improve auto safety.

The odds of winning the lottery are reported at between 1 in 18 million for a state lottery to as low as 1 in 120 million in a multi-state contest. So, in fact the odds of an airplane accident are greater than the average person’s odds of winning the lottery.

But the automobile odds show that driving is really the risky activity – 77 times riskier than flying, yet it’s unusual to hear of anyone afraid of driving.

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 to travel along with him at work.

Plane Answers: Turbulence causing aircraft to break apart and London holding patterns.

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!

Tai asks:

Hi Kent,

I’m an avid reader of both your blog and Plane Answers and plan to pursue a career in aviation.

I generally keep an eye out in my news feeds for airline/aircraft related stories and came across a CNN article about an Air France A330 which was lost over the Atlantic. Officials are saying that the crash could have occurred as the plane encountered extremely heavy turbulence.

Is it possible for turbulence to be severe enough to actually cause a plane to come down, or would there likely be other factors or problems with the aircraft? Also, if there is turbulence that strong, wouldn’t the captain reroute the flight around it?

I’m often questioned about the dangers posed by turbulence and I’ve explained in the past that modern airliners are engineered to handle the worst case scenarios. But there are absolutely situations, such as extremely large thunderstorms that could cause structural damage to an aircraft.

It’s a big part of why airlines, and pilots specifically, are so concerned about accurate weather reports, good radar technology, flight planning and operating procedures that keep us away from thunderstorms.

Our manual even specifies a 20 nautical mile distance to be flown around thunderstorms. But don’t confuse every cumulous cloud as having the potential of a thunderstorm.

One of the few examples of an airliner being brought down due to turbulence that I’m aware of hits rather close to home for me. In the late 1960s the airline my grandpa had started 40 years earlier purchased a competing airline.

Just weeks after that purchase, one of the recently acquired airplanes, a Fokker F-27s broke up in-flight near Illiamna mountain after an encounter with severe-to-extreme turbulence.

It was the worst accident by far over the 60-year run of the company. So while I’d love to say turbulence could never cause an accident in a modern airliner, I wouldn’t rule it out as a possibility today.

But I’m not so sure that’s what happened to Air France 447. In fact, by definition aircraft accidents are usually the result of something rather unanticipated. So I don’t buy any speculation by the analysts at this point, even with the small clues the ACARS maintenance status messages give us. This is the stage of an investigation where nothing is ruled out.

Jackie asks:

Hi Kent!

What a great service you do here. I have read through numerous posts and it has surely helped calm some of my fears of flying.

A few months ago, I was on a BA flight from PRG to LHR and about 30 minutes outside of London, the captain came on to tell us that due to heavy traffic volume, we were to be placed in a racetrack holding pattern. This holding pattern lasted about half an hour before we began our final descent to LHR. As someone who is a very nervous flyer, anything out of the ordinary makes me very on edge. I’ve flown a great deal, but this was my first experience with a holding pattern. I guess I have been fortunate!

My question is: Just how common are racetrack holding patterns? Are some airports (such as LHR) more notorious for holding planes in that way? Also, I was curious as to whether there is any type of “hierarchy” for exiting the holding pattern? I mean, is it truly first-in, first out? Or since we were in a smaller plane (737 or A320) for the short hop from Prague, would preference be given to the heavies coming from the USA and such?

One final question, when we were in the holding pattern, and in the midst of a turn, the plane quickly jolted/banked to the side in which we were turning and then quickly jolted to the extreme other side as if the pilot quickly corrected this. He then came over the speaker to say that we had hit an air pocket. Does that sound right? Is there any danger in “hitting air pockets” while in a holding pattern turn? I do remember we were pulled out of the pattern to land soon after that experience.

Hi Jackie,

Holding while on the arrival portion of a flight is probably more common in London than any other place I’ve flown. I’d estimate that half the time I have flown into London involved a hold, usually for only one to three turns.

The priority is based on first in, first out. So you may start holding at 16,000 feet and be given lower as the airplanes below you clear out. Finally, at perhaps 11,000 feet, you’d be the next one in line and could then start the rest of the approach.

You almost certainly came across another airplane’s wake. You can think of these currents that are generated by aircraft much in the same way a boat creates a wake as it plows through the water.

In your case, there was probably an airplane holding at the same altitude that had been cleared lower and your flight began holding at that level as well. The wakes usually descend as time goes on, which can be an issue when holding below another aircraft.

Since the holding patterns drawn and flown by the airplane’s computer known as an FMS (flight management system) is so precise when coupled to GPS technology, it’s no surprise that you happened to come along another airplane’s wake.

Generally, they’re startling, but they don’t threaten the safety of airliners.

Coincidently I have a video that shows a flight we did last year as we were about to enter the London holding pattern over “OCK” or the Ockham VOR which is a specific point we navigate to near the town of Guildford. Notice the holding pattern drawn by our computers for our airplane to follow.

In the third to last scene, you can see the airplanes on the screen that we can view in the cockpit. And the final scene shows us selecting a lower altitude before I put the camera away.

Thanks for the great question.

Do you have a question about something related to the pointy end of an airplane? Ask Kent and maybe he’ll use it for nex
t Monday’s
Plane Answers. Check out his other blog, Cockpit Chronicles and travel along with him at work.