Aircraft rescue and firefighting – ARFF

Firefighters are the first responders when an mass accident occurs. More than 100 people travel in airliner at once. What are the safety measures to avoid such mass accidents?. Once any abnormal situation occurs the pilot reports to the ATC. The pilot then tries to glide the plane and land the plane in any nearby airport. The next step is to rescue the passengers and secure the aircraft. Who does this job of rescuing the passengers and securing the airplane?.

Airports have dedicated firefighters known as Aircraft rescue and firefighting – ARFF. They are highly skilled and trained to handle critical situations. Aviation emergency are considered to have mass casualty potential. They use specialised foams and chemicals which have the capability to quickly extinguish fire caused by aviation fuel. They are responsible to mitigate the hazard such as blasts. Every airport have a specialised team of  Aircraft rescue and firefighting crew.

There are several safety rules that are needed to be followed for operating the Aircraft rescue and firefighting crew.  There are regulations that are provided by the government aviation organisation which operates under International Civil Aviation Organisation (ICAO). Airports are required to keep in reserve a particular amount of extinguishing agents depending on the size of aircraft operating and the frequency of aircraft operation.

How to stop an airplane? – Autobrake

How do you stop your car travelling at 100 km/hr?. Ofcourse by pressing the brake pedal placed right next to the accelerator. But how to stop an airplane which is approaching at a speed of 315 km/hr?. Yes the maximum landing speed of an Airbus A320 is almost 315 km/hr. What kind of brakes have the capability to stop such aircraft?. There are multiple matters that are needed to be taken care by a pilot during take-off and landing. So how does a pilot stop an aircraft?.

There is a system known as “autobrake” system which helps the pilot to stop the aircraft.

What is an autobrake system?

It is nothing but an automatic hydraulic brake system which are used in modern airplane. They are normally applied in the time of landing and take-off. There are buttons which helps the pilot to activate the kind of effect he needs. Such as low braking or maximum braking effect. The buttons are marked in the panel as “LO” or “MAX”.

How is an autobrake useful in take-off?

Autobrake system is used in case of RTO (Rejected Take Off). There is a separate mode for RTO which is indicated on the instrument panel. In this case an autobrake system considers several conditions and applies the hydraulic brake automatically.

Aerodynamic Heating

Have you ever used ambient air for cooling?. Air is normally used for cooling purposes, such as bypass air in turbofan engine etc. But, ambient air may also heat things up. Wonder how?. This occurs in the process of aerodynamic heating.

When an object moves at high speed, the surrounding air heats up the object. This happens as the the kinetic energy is converted into heat due to friction. Aerodynamic heating is effective at Mach numbers typically above M>2.2. If the object or aircraft’s material isn’t made to withstand such conditions it may cause destruction. So, which vehicles travel this fast?. Vehicles such as rockets, reentry vehicles, hypersonic vehicles, hypersonic missiles, and high speed supersonic jets travel at such speeds.

There are several technique which are used for sustaining aerodynamic heating. Such as thermal resistive coating, Blunt design etc are generally used. Especially spacecraft use ablative materials to protect themselves from such high temperature. Reentry vehicles and supersonic aircraft also use this kind of technique to avoid disintegration.

Which parts of an aircraft does this aerodynamic heating affect?

Aerodynamic heat is highly concentrated at the leading edges as they confront the fast moving air. But, the complete body would heat up if the aircraft maintains such speed. Special care is to be taken while designing such high speed vehicles.

Are all aircraft stable?

Stability means the state of being stable. With six degrees of freedom available in aircraft stability means a lot. This means if you accelerate too much you gain additional lift thus increasing altitude. If you slow down too much you loose lift and start to decent. The deflection of control surfaces needs to be carefully calculated and executed because a little increase in deflection may cause instability that may have adverse results. Are aircraft stable all the time?.

An aircraft is stable during most of its flight regime. But if an aircraft is completely stable you won’t be able to manoeuvre it. To manoeuvre an aircraft it needs to be un-stabilised for a little duration. Because stability is nothing but a state of equilibrium. An aircraft needs to be designed with such kind of stability which would automatically bring back the aircraft to a stable condition once confronted with a disturbance.

Fighter jets are highly unstable. As a result of highly unstable design they are able to perform difficult manoeuvres with ease. Adding control surfaces such as canard would make the aircraft more unstable. If you go further into the concept of stability you would like to know static stability and dynamic stability.

V speeds – The threshold in aviation

You might have noticed the speedometer in your car or bike. It would have  had various speed indications. You might have also noticed some coloured rings alongside the number markings such as green, yellow and red. Have you ever wondered the reason for using them in speedometer?. They indicate the safe speed of operation. Similarly there are certain speed limits in aviation which are used to know the threshold. These speed limits or speeds are called as V speeds.

There are approximately 44 regulatory V speeds and 29 other kind of V speeds in use. Of all the 73 V speed 26 of them are most commonly used in aviation. They define some thresholds such as minimum take-off safety speed (V2min), maximum operational speed (VNE). This maximum operational speed (VNE) is also known as never exceed speed. All these V speeds are defined and standardised by aviation regulatory bodies. These V speeds are specific to the type of aircraft.

How is this V speed determined?

V speed are determined during the flight tests and type certification of the specific model of the aircraft. These data are generally obtained from flight designers and aircraft manufacturers.

Where are these V speeds defined?

You can find these V speeds in Federal Aviation Regulations (FARs)