I have gathered some common questions and answers that I get from people about flying. Do you have a question of your own? Keep it fairly simple and remember: This is not a pilot forum! It’s a forum where people and passengers interested in aviation can get help with common questions. OK? Let me know!
Can you land in no visibility?
With the Airbus 320 series, we can land without actually seeing the runway before we land. The requirement is 75m visibility on the ground, which in practice means 0m when coming from above. However, there are a lot of requirements concerning these CAT III approaches, covering:
- Equipment at the aerodrome
- Wind limitations
- Procedures in connection with the active runway
- Aircraft equipment
- Training and recency requirements for the flight crew.
Why does the engines suddenly stop roaring, just after takeoff?
Due to noise restrictions!
Aviation is today restricted in many ways, especially concerning noise. Before every takeoff, the pilots makes their takeoff calculations in respect to weight, runway length, wind, temperature etc. when feeding all this information to the aircrafts computers, we also program an altitude where we reduce engine thrust. Typically, this altitude is between 800-3000 ft depending on noise sensitive areas around the actual aerodrome.
What is turbulence?
Turbulence is in simple terms the same phenomena as waves at sea!
Modern aircrafts are built to withstand turbulence. It’s unpleasant and tiresome, but there is no major risk for the aircraft itself. But the human beings inside the cabin needs to be secured with seat belts in order not to be injured. This is also valid for equipment, service carts etc. onboard in order not to harm the humans around it.
There are different types of turbulence. Let me give you 3 examples:
- Clear air turbulence (CAT)Low and high pressure air masses fights about domination of the air all the time. In connection with this, strong winds are sometimes a result. These winds are called “Jet Streams”. Before every flight the pilots study weather maps covering the actual flight route. On these charts, the metrologist has predicted where these jet streams will be, and where there is risk of turbulence etc. Typically, when passing through different air masses or jet streams, this will often create a certain amount of turbulence. There are no other visual indications where the turbulence is, so you need to rely on the weather charts and be proactive. Sometimes it’s better to switch on the fasten seat belts signs at the first indications of turbulence.
- Turbulence in connection with clouds and thundershowers.All clouds has some form of interior “movement” inside. Warm air rises, expands and cools off. During that process the small droplets present in the air is being condensed and for different types of clouds depending on pressure, temperature etc.
The key element concerning turbulence is movement of air. The higher the density (amount of droplets) the more risk of turbulence. So how do we know which clouds to avoid and which clouds that are acceptable to fly into? The answer is RADAR. As soon as we suspect that there is some Risk of turbulence, we switch on the airplane radar. The radar beam bounces on the droplets and indicates where the density is high and where it’s not. High density – Red color on our radar screen – Avoid the area! Simple 😉
- Wake turbulence.Just like ships at sea, aero planes creates “waves” in the air. If you fly too close to a preceding aircraft, you get into its “wake” and you will experience turbulence. Larger aircrafts with more lift creates bigger waves and more turbulence. That’s one of the reasons why the Air Traffic Control (ATC) separates approaching aircrafts with a certain distance. You need more separation (larger distance) between a large and medium aircraft, both at takeoff and at landing.
Why is there always at least two pilots?
Just like the airplane itself, the safety systems are always doubled or tripled – 2 pilots are better than one! But only if…(see below). The statement above is valid only if certain systems are in place.
The pilots a needs for instance:
- Clear and respected Standard Operating Procedures (SOP).
If every crew member knows their SOP, the others know how he/she will react and solve a present challenge.
- Safety Culture
A safety culture which clearly states that SAFETY is number one! Nothing is more important. This should be communicated to the employees at every level, and mid & top management needs to show the others that this is rule number one.
- Proper training!
Training in a 2 pilot system is vital in order to work as a team. The pilots train at least two days a year in a simulator, often more! Together with some training, the pilots needs to show an acceptable standard coping with the scenarios and failures they face. The session is graded and a form is filed for the authorities and eventual follow up. If the pilots don’t pass, they will receive an evaluation pinpointing what needs to be corrected. If unsuccessful, in the end, the pilot(s) will loose his job. Sometimes I wonder why I chose an occupation where you need to put all your skills, airmanship and certificates on the table and say “If I don’t measure up, then you can take it all…”! On the other hand, it’s good both for me and for my passengers to know that we are checked and passed for the duty we are about to perform! A safety barrier!
- Selected crew members!
The people working in the airline have been interviewed, tested and selected as suitable for the task. Airlines makes big efforts in order to hire the best and most motivated persons among the applicants. Every dollar spent this early is money well spent!
- Pilots are humans!
We make mistakes, forget things and sometimes take doubtful decisions. That’s why we call out and check the other pilot all the time to confirm that things are going the right way. And of course – pilots gets ill and sometimes die, just like other humans. We go to yearly medical checks etc. but anything can happen. Then it’s nice to know that there is another pilot ready to take over land the plane safely!
What happens if an engine fails at lift off?
The multi engine aero planes still flies! Training, aircraft performance and procedures covers this situation as well!
All takeoffs are preceeded by careful preparation. Before every takeoff, the pilots runs through different “what if” – “then this”! The pilots study departure procedures, brief Eachothers regarding climb out routes, weather, and what to do if an engine fails. Other scenarios are also briefed, i.e. If smoke or fire occurs, if we have to stop in the runway and evacuate etc. by being prepared, the pilots know what to do if a critical situation should come up.
Our performance calculations assumes that the most critical engine will fail at the most critical point. If the calculations at present weight shows that the aircraft can takeoff safely, we are good to go. The calculations shows which speed will be decision speed (V1), how much margin we will have if stopping on the runway, what altitude we shall clean up the aircraft etc. Some of these figures are programmed into the aircrafts computers and after a proper check, we’re good to go!
Aircrafts have different categories – Why?
“You use CAT D minima on the A321? Why is that? Never heard of that before…”
Depending on a lot of things, aircraft weight, approach speed, etc. the people designing our landing and go around procedures have to keep that in mind. For instance, if your aircraft has higher approach and go around speed than your colleague – you won’t be able to make as tight turns. Then, your go around procedure needs to be tailored for that in order not to trick you into a mountain or a mast. The faster you need to fly, the larger turn radius.
So, one way of solving this is to raise your minima slightly. Then, when making your go around decision, you won’t be as close to the ground as your colleague. Safe and sound.
So, Lasse – our A319 and A320 are classified Category C, while our A321 is Category D. This means that if the weather is marginal at our destination (excluding auto land with no minima) you’ll have a slightly better chance to land an A319/320 than a A321. This is rather theoretical – most often the minima only differs 10-20 feet (see illustration taken from WAW runway 11 approach plate) but still, there is a difference!
FAQ: Fire fighting equipment onboard aircrafts
“I work within the shipping industry, where we nowadays use fire extinguishers with powder in many places. Last week, when departing from Seoul with a Boeing 747-800, I began to wonder what kind of fire extinguisher you use onboard your aircrafts?”
We use HALON 1211 on our aircrafts. Halon is, as you already know, an extraordinarily effective fire extinguishing agent. It’s a liquefied compressed gas that disrupts combustion and has the chemical formula CBrClF2. It’s best suited for class B (flammable liquids) and class C (electrical fires), but it is also effective on class A fires. One of the advantages is that’s it’s clean and leaves no residues, which is especially appreciated in an aircraft.
HALON 1211 was introduced already during the seventies, but due to the effects on the ozone layer, it was restricted (Montreal protocol) to special areas only. Aircraft use is one of the few. As you mentioned in your letter, a switch has been made (long time ago) to other agents within your industry. The fire extinguishers onboard an aircraft are seldom used, and there is an effective recycling system in use.
In Scandinavian Airlines System we train and practice firefighting every year in a fire mock up. I used to instruct on these occasions before, and the training is very interesting AND fun! During training, we use CO2 or Foam, and it’s so nice to refresh your skills and know that you’re up to the challenge when needed!
Production of new Halon ceased in 1994. Therefore, recycling and reusing the existing supply intelligently and responsibly to protect lives and property is the smartest thing to do.
- Class A fire – Common combustibles (wood & paper)
- Class B fire – Flammable liquids
- Class C fire – Electrical fires
- Class D fire – Combustible metals
TCAS – Becoming invisible or not?
Is it possible to switch off the Transponder and become “invisible”? // Best Regards I.D.
TCAS and MH 370
I often receive questions concerning TCAS, especially during 2013 and the search for Malaysian MH370. But there are still questions, and I’ll try to describe it as simple as I can, in order for everyone to comprehend.
So, what’s TCAS (Traffic Collision Avoidance System)? There are many versions of TCAS, but regulations today (ICAO) requires that your aircraft should be equipped with such a system if >5700 Kg or 19 PAX.
Aircrafts “shaking hands”
TCAS uses SSR transponder signals and monitors the airspace around our aircraft in order to avoid a mid-air collision. It interrogates all aircrafts in the vicinity and waits for a response. A TCAS-equipped aircrafts then answers with information including altitude, speed and heading etc. This will be presented in our cockpit on a display with information relative to our own aircraft.
The airspace (bubble) around our aircraft is divided into different sectors, both in lateral and vertical aspects. When another aircraft enters our “bubble”, it’s called an INTRUDER. Targets are color coded, depending on time to a possible collision:
White Aircrafts not presently a factor.
Yellow Aircrafts 40-25 sec to collision.
Red Aircrafts 25-0 sec to collision.
When the INTRUDER becomes YELLOW, we receive a TRAFFIC ADVISORY.
When the INTRUDER becomes RED, we receive an aural RESULUTION ADVISORY.
TRAFFIC ADVISORY (TA) “TRAFFIC, TRAFFIC”
RESULUTION ADVISORY (RA) “CLIMB, CLIMB” // “INCREASE CLMB” “DESCEND, DESCEND” etc.
When the intruder isn’t a factor anymore, an aural “CLEAR OF CONFLICT” is given.
Follow the TCAS!
You are not allowed to disregard TCAS commands or maneuver in the opposite direction. If the intruder doesn’t follow commands, the TCAS system is reactive and tries a new corrective command. It can for instance change from CLIMB to DESCEND, DESCEND NOW if deemed safer. The commands are coordinated between the conflicting aircrafts i.e. CLIMB instructions to one aircraft, DESCEND instructions to the other! Smart!
In the tragic Überlingen mid-air collision in 2002, the Bashkirian Airlines Flight 2937 didn’t follow TCAS commands. Instead, they relied on the instructions from Air Traffic Control (ATC) in order to avoid a collision. After this accident, it was reinforced that YOU SHOULD ALWAYS FOLLOW THE TCAS (unless visual contact with conflicting aircraft has been achieved). The TCAS alerts the pilots when something has gone wrong, maybe at the ATC. Then you should disregard further instructions from ATC and follow the interactive TCAS system!
So, is it enough to just switch off the Transponder and TCAS in order to be completely invisible to the system? No, the “Stand By” function still gives a presentation on our TCAS display, but without any information about altitude, track etc.
To be completely invisible, you have to pull some circuit breakers and disconnect another systems, before being completely invisible. This is of course not something we do! Instead of pulling circuit breakers, you could become invisible if there is something wrong with the system OR if you have a fire that destroys vital cables and systems. In my opinion, that’s a more plausible cause for the disappearance of Malaysian MH 370.
It’s important to know, that most flying objects can be picked up by military radar stations (Primary Radar), even if the transponder and TCAS aren’t working. There are Primary Radars stations scattered around the world, mostly in connection with important borders or sensitive objects. These radar stations can pick up signals even if our aircraft isn’t using a Transponder and a synthetic tag. However, it requires skills and a defined sector being watched.
The article is a simplification and not a TCAS operation manual.
Illustrations taken from various sources on the internet.