Ask Captain Lim

Hi Capt Lim,

First, I would like to say that this is the greatest web page I have found on flying. Thanks!

I have two questions:-

You mentioned that, when flying long distance over water, the route is never further than one hour from an airport for any emergency landings. I wondered about this while looking at the map in the airline magazine. When flying from TYO (Tokyo) to LAX (Los Angeles), where are the emergency airports on route? Also, when flying from LAX to TYO, why does the route head further north and then further south when returning to LAX?

In flight, I also see people standing around the door areas and I am sure there is no way they could open it, but tell me, am I correct about this! :) ..one of those silly questions I guess that I have wondered about.

All my other concerns were answered in your web page and it is all so very interesting to read anyway. I too get some jitters from time to time while flying, but what I say to myself is "You are right where you are suppose to be at this minute" and that over water puts me at peace. Flying is fantastic and it lets me go places that I never would be able to visit if not for flying. So the thrill of adventure outweighs any fear. It still amazes me just the same, this whole flying business! I love it.

Thanks in advance for any answers you can give me to my questions.

Nola Glen

Hi Nola,

From your email, I have summarized the 3 questions:-

1. Where are the emergency airports within an hour's flying on the route
from TYO to LAX?
2. Why is the route from LAX to TYO appears to be curve on the map?
3. Can the passenger doors be opened in flight?

1. As regard to your first question, I was discussing a topic on extended twin engine operations (ETOPS), peculiar to any two-engine airplane. This is not applicable to a Boeing 747 because it has 4 engines. Historically, for a twin engine commercial airplane to fly over water or land, Regulations require it to be within an hour away from an emergency airport if it loses one of its engine due to mechanical problem. Therefore, these airplanes can only operate in Airways within an hour from an emergency airport. In your case, I believe you flew on a Boeing 747 from TYO to LAX and the law need
not require it to comply with this one hour rule.

2. I am sure your second question is a very interesting one for those who are not very familiar with the various types of maps. Do you know that when you first did Geography in School, many people were not aware that the basic World map was a distorted representation of the Earth's surface. Only those countries around the Equatorial regions are truly represented by its size. Those nearer to the Poles are highly magnified. The basic World map is similar to a ball being stretched so that its shape is made to fit into a piece of paper. The most accurate map is in fact the map on a Globe.

The shortest distance between TYO and LAX is in fact a straight line between these two cities. So if you place a string on a Globe between TYO and LAX, you would see that the shortest distance is in fact the one that head further north and then south to LAX. Because the map you so often used or see is in fact a distorted map, the shortest route now appears like a curve on the map in the Airline magazine.

3. Your third question shows your concern about the airplane doors which could be accidentally opened in flight by those standing around them. I can assure you that it is almost impossible to open the doors in flight even if they have been deliberately unlatched. You know why? The differential pressure in most airplanes is around 9 psi (pounds per square inch). So there is a tremendous amount of pressure holding the door to its seals. The only way to open the door in flight is to fully depressurize the airplane
cabin pressure to zero differential pressure. In fact, this is automatically achieved when the aircraft lands. The reduction in pressure is so gradual that you hardly feel it unless you have a cold and your ears are blocked!

Your questions are not silly and I am sure many passengers are just as curious as you are ! :-)