Visnu

High Speed or the modern aircraft’s are efficient and fuel saving at high altitudes.In order to take advantage of these properties the interior of an aircraft flying at high altitude is pressurized to allow passengers and crew to function normally without the need for additional oxygen.

Insufficient O2,( Hypoxia) will give a negative effect to a overall human performance such as nausea, lack of concentration, vomiting, & etc.

Up to an altitude of 10000 ft (3.3 km), the air pressure and consequently the amount of oxygen is sufficient for humans to operate without too many problems. However, lack of oxygen can become apparent at altitudes above this and cabin pressurization systems are designed to produce conditions equivalent to those of approximately 8000 ft (2.6 km) or less. This means that there is no need for oxygen equipment except for emergency use by crew or passengers and the effect of low atmospheric pressure on passengers is negligible.

Once the cabin altitude exceeds of 10 000 ft, the crew should be on Oxygen mask whereas the remaining passenger will be on their oxygen mask when the cabin altitude reaches 15 000 ft.

What is cabin altitude?

Cabin altitude is defined as— Cabin pressure, in terms of altitude, above the mean sea level, while the aircraft cruising at a certain altitude.

The overall differential pressure between the cabin pressure altitude and the ambient pressure should not exceed 8-9 psi or a negative differential pressure of -0.5 ot -1.0.

Differential Pressure = Cabin Pressure – Ambient Pressure (Outside of Aircraft)

The difference in pressure between the inside and outside of the pressurized areas of the
aircraft or differential pressure produces hoop stresses which are applied cyclically every time the aircraft is pressurized and de-pressurized causing fatigue which can, ultimately, lead to structural failure.

How a Cabin Pressure Is Maintained?

Cabin Pressurization is controlled by having a constant mass flow of air entering the cabin and then varying the rate at which it is discharged to atmosphere. The constant mass flow of air is supplied by the air conditioning system via the mass flow controller and is discharged to atmosphere by the discharge or outflow valves.
The operation of these valves is governed by the pressure controller when in automatic control and by the flight crew when in manual.

System Instrumentation

The minimum indications required for a pressurization system are:
• Cabin Altimeter. This gauge reads cabin pressure but is calibrated to read this in terms of the equivalent altitude of the cabin.
• Cabin Vertical Speed Indicator. This indicates the rate at which the aircraft cabin is climbing or descending.
• Cabin Differential Pressure Gauge. This indicates the difference in the absolute pressure between the inside and outside of the aircraft cabin and is generally calibrated in psi. In the event of a malfunction of the pressure controller or outflow valve, this instrument would indicate that the safety valves were controlling the cabin pressure at the structural (emergency) maximum pressure differential.

Erwin Romm (Real name withheld for personal reasons)

“Hello, I’m Erwin, hailing from Kuantan, Pahang. As of now, I’m 20 years of age. I applied for this cadetship on April 2018 and got my offer letter the same exact day the Enola Gay dropped the first atomic bomb on Japan: August 6^th 2018.”

I stumbled upon Visnu’s(V) blog when I randomly Googled ‘AirAsia Cadet Pilot’. The first article V published captivated me and I was enticed to getting to know the Legend. I got in touch with V and he immediately introduced me to a WhatsApp Group set up under his own initiative for a simple purpose: To enlighten and share resources among its 200+ members in the hopes of giving an edge to the members among the rest and pass through the stages.

In Stage 1, our group discussed past year questions where we tutored one another. Stage 2, a member was kind enough to forward a sample test of the Harrison Assessment. Stage 3 was the most memorable stage for me as I got to meet some of the members who banded to train together for the Psychomotor Test (The hardest stage in AA, many faltered at this stage). The result, all six of us who pulled our weight together managed to pass Stage 3. Truth goes far for the old adage “Strength is found in numbers.”

In Stage 4, we discussed questions and adopted Visnu’s previous strategies where he and another candidate (Tan from TurtlesFlyToo) exchanged quickfire questions between one another. True to form, this strategy helped me enormously when I faced the dreaded IV panel at Stage 4.

Finally after a long wait, I received word that I had been shortlisted for the loan briefing. I was tremendously overjoyed. Nothing could make me happier. Once again, I think all of this would not have happened should I forego V’s guidance and his WhatsApp group. I also would like to attribute my success to others too who have gone out of their way to help me throughout this journey. Most heroes don’t wear capes; they wear ray-bans instead. XDXD

For those who stumbled upon this cadetship. Keep your head up high as AA will resume their cadetship next year as well. A little backtrack homage towards V on his two word-one meaning advice to all of his readers “Be Prepared”. Thanks V. ^^

“By failing to prepare, you are preparing to fail.” – Benjamin Franklin

Whenever we ask someone how an aircraft produces lift they are able to answer based on Bernoulli Principle(BP); the airflow above the aerofoil has a higher velocity whereas the airflow on the lower surface of the aerofoil has a lower velocity. Based on BP the higher the velocity the lower the pressure therefore the difference in air pressure produces lift.

When a follow-up question is asked why the airflow on the upper surface is great, a majority of us are unable to answer. So today I will be splitting on Why & How the airflow has a greater velocity on the upper surface.

This is a typical Cambered Aerofoil (Asymmetrical Aerofoil):

Just for your information. Cambered aerofoils are not used in most modern aircraft, Symmetrical and Supercritical aerofoils are used.

To start off, Aerofoil basically uses two principle in producing lift:

1. The Principle Of Continuity
2. Bernoulli Principle

1.The Principle Of Continuity

The air mass flow, or mass per unit time, through the tube will be the product of the cross-sectional area (A), the airflow velocity (V) and the air density (ρ).

Mass flow will remain a constant value at all points along the tube. The Equation of Continuity is:

A × V × ρ = Constant

For An Example, The Mass Flow throughout Point 1, 2 and 3 is the same.

Which means that the flow of mass is constant throughout every part of the tube. When a same amount of volume passes through a narrower tube the velocity increases whereas when it travels through a wider tube the velocity is lower.