This article has been divided into 5 parts:
- What is an Aerodrome Category ?
- How to determine Aerodrome Category ?
- Types of extinguishing agents
- Some reserve stock
Due to the chances of mass casualty involved in aviation emergencies, it is critical that emergency response equipment and personnel should arrive at the scene within the minimum possible time. So, as to provide timely response because if the fire (involving an aircraft) is not under control within 60-80 secs then it is better to evacute the place as soon as possible. The aircraft wings are laden with fuel (20000-50000 gallons) and a CFT may be having 12000 lts of water plus some other extinguishing agent to counter, so becoming a hero will not solve the problem, instead timely response and presence of mind will fetch better results.
Now we understand that time is the key when it comes to responding to fire emergency. Thus the concept of response time.
Response Time – It is considered to be the time between the initial call to the ARFF service, and the time when the first responding vehicle(s) is (are) in position to apply foam solution at a rate of at least 50 per cent of the discharge rate of the aerodrome category.
The operational objective of the rescue and firefighting service shall be to achieve a response time not exceeding three minutes to any point of each operational runway, in optimum visibility and surface conditions.
1. What is an Aerodrome Category ?
To determine the level of protection for a particular airport this special category of fire-fighting involves incident response, hazard mitigation, evacuation and possible rescue of passengers and crew of an aircraft involved in an aerodrome (or potentially off aerodrome) ground emergency.
2. How to determine Aerodrome Category ?
The aerodrome category shall be determined based on the length of the longest aeroplane normally using the aerodrome and its fuselage width.
Thus the two criterias are:
- Overall length of the aircraft
- Width of the Fuselage
Note: After selecting the category appropriate to the longest aero plane’s overall length, if that aero plane’s fuselage width is greater than the maximum width, then the category for that aeroplane shall actually be one category higher.
For example – Boing 747-800 has an overall length of 76m and fuselage width of 6.1m so it will be needing an aerodrome to have a category “9” to operate but an Airbus A380 has an overall length of 72.7m (less than 747-800) and a fuselage width of 7.1m which make it fall into the Catergory “10”.
During anticipated periods of reduced activity, the level of protection available shall be no less than that needed for the highest category of aeroplane planned to use the aerodrome during that time irrespective of the number of movements.
The level of protection provided at an aerodrome for rescue and fire fighting should be equal to the aerodrome category determined using the above principal and Complimentary extinguishing agent except that, where the number of movements of the aeroplanes in the highest category normally using the aerodrome is less than 700 in the busiest consecutive three months, the level of protection provided shall be not less than one category below the determined category.
3. Types of extinguishing agents
Water is one of the main fire fighting or fire extinguishing agent but there are other agents too which act differently to bring fire under control and in much effective ways for different scenarios.
a. Principal agents : Produce a permanent control for several minutes or longer
- Foam meating performance level A – Protein Foam
- Foam meating performance level B – Aqueous Film Forming Foam (AFFF)
- Foam meating performance level C
b. Complementary agents : Rapid fire and flame suppression capability but offers transient Control
- Dry Chemical Powder (DCP)
The above image shows the amount of water and extinguishing media an airport operator should have while declaring its Fire Category. If we compare the water requirements for Level “C” foam and Level “A” foam for Category “10” we can see that water in Level “A” is 48200 lts but in Level “C” is just 22800 lts. This reduces a lot of weight to be carried and we require less number of CFTs as the capacity of a CFT is around 12000lts only. But keeping Level “C” Foam makes pockets of an aerodrome operator heavy.
4. Some reserve stock
A reserve supply of foam concentrate and complementary agent, equivalent to 200% and 100% respectively of the quantities of these agents to be provided in the rescue and fire fighting vehicles, shall be maintained on the aerodrome for vehicle replenishment purposes.
Foam concentrate carried on fire vehicles in excess of the quantity identified in Table can contribute to the reserve.
Sufficient propellant gas (Nitrogen) should be included to utilize this reserve complementary agent. Where a major delay in the replenishment of this supply is anticipated, the amount of reserve supply shall be increased.
It becomes really important to decide the level of protection provided at an aerodrome for rescue and fire fighting for safe aircraft operations. It should be as per the aerodrome category determined using the Principal and Complimentary extinguishing agent also keeping in mind incident response, hazard mitigation, evacuation and possible rescue of passengers and crew of an aircraft involved in an aerodrome (or potentially off aerodrome) ground emergency.
Any reduction in the fire category due to reason whatsoever must be notified to the ATC and promulgated as per requirement to maintain the safety of flight operations.
For further understanding: