What it is that it is …?

Q1. Do you know the cruising altitude of an aircraft ?

Q2. Why are aircraft windows Round in shape ?

Q3. Do you know which is the dirtiest place on the aircraft ?

Q4. Do you know the average life of an commercial aircraft ?

Q5. Why do eardrums causes irritation during a flight ?

1. Do you know the cruising Altitude of an aircraft ?

According to USA Today, the common cruising altitude for most commercial airplanes is between 33,000 and 42,000 feet, which is even beyond the highest peak in the world which stays at 29,031 feets (8848.86 m). The area is called the lower stratosphere, which is just above the troposphere, lowest part of the atmosphere.

The biggest reason for this altitude lies with fuel efficiency. The thin air creates less drag on the aircraft, which means the plane can use less fuel in order to maintain speed. Thus with higher altitude the aircraft gets lesser wind resistance, lesser power loss, lesser effort and also least traffic to avoid. So an aircraft can comfortable cruse at one specific altitude as altitude changes also reduce fuel efficiency.

At this altitude the weather generally remains more or less constant and chances of turbulence is also the least. Long haul flights generally take these altitudes to avoid short haul traffic.

2. Round windows are stronger that Square !

Square windows would be hazardous for airplanes because the pressure inside and outside the cabin is very different; much that the sharp edgy corners wouldn’t be able to handle the pressure and would thus give in.

Sharp corners naturally concentrate more stress, which further gets weakened by the immense air pressure. Curved or Round shaped windows distribute the stress of the outside pressure of air equally through out the window structure, and thus are stronger and less prone to deformation because of the pressure.

3. Dirtiest place on the aircraft is the traytable behind the seat !

Are you a germaphobe? Then this is an ALERT !!!! The dirtiest place on a plane was found during recent studies to be the tray table on the back of the seat in front of you. In fact, there were eight times as many bacteria found here when compared to the toilet flush button! So, make sure to take some sanitary wipes with you on your next journey.

4. Lifespan of an aircraft is measured in terms of number of pressurized cycles !

The lifespan of an airliner is not truly measured in time, instead, it is counted based on pressurization cycles. Each time an aircraft is pressurized during a flight its fuselage is subjected to stress. The “lifespan” of an aircraft is reached when there are certain  metal fatigues and cracks which may pose danger. The “service life of 20 years” is generally expressed by approximate figures of 51,000 flight hours and 75,000 pressurization cycles for most aircraft. If an aircraft is used on long haul routes it experiences relatively few pressurization cycles in its “life” and can remain airworthy far beyond 20 years and you know the reason behind this by now.

5. Eardrums cause irritation during a flight ! Why?

The pressure at mean sea level is 14.7 psi (pound per square inch) and the aircrafts are pressurized vessels. Pressurization systems are designed to keep the interior cabin pressure between 12 and 11 psi at cruising altitude. On a typical flight, as the aircraft climbs to 36,000 feet, the atmospheric pressure is about 3 – 4 psi but the interior of the plane maintains a pressure of 11 – 12 psi as if the cabin has “climbed” to between 6000-8000 feet only.

So, the obvious question is why not keep the cabin at 14.7 psi to simulate sea-level pressure and maximize comfort? The aircraft must be designed to withstand differential pressure, that’s the difference between the air pressure inside and outside the aircraft. Exceeding the differential pressure limit is what makes a balloon pop when it’s over inflated. The greater the differential pressure, the stronger (and heavier) the airplane must be built. It’s possible to build an aircraft that can withstand sea-level pressure during cruise, but it would require a significant increase in strength and weight. A 12 psi cabin is a good trade-off in that case!!

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