What Is Fuel Dumping in Aviation?
When discussing aircraft, you may have heard about the process of fuel dumping or fuel jettisoning, that of which is a procedure where fuel is forcibly removed from the vehicle prior to landing. This is an emergency procedure, only conducted in very specific instances, such as when the aircraft needs to rapidly return to the airport after takeoff, or prior to an emergency landing at the intended destination. While there are valid concerns over this procedure, it is not something that is done regularly or on a whim. Instead, it is used for the safety of those in the aircraft when certain issues arise. To help you better understand what fuel dumping is and why it is carried out, we will discuss it in detail in this blog.
For an aircraft to remain airworthy and efficient for flight, it must have a controlled weight that does not exceed design limitations. The two most important forms of weight limits are maximum takeoff weights and maximum structural landing weight, the former being the max weight the aircraft can have to effectively takeoff at the beginning of a flight, while the latter is the maximum weight it can have when landing at its destination. By limiting the amount of weight and ensuring these maximums are not exceeded, most aircraft can conduct their typical operations with an optimal fuel consumption rate. If an aircraft attempts to land with a weight that exceeds its structural landing weight, for example, there is a chance that structural damage may ensue, leading to the possibility of a breakdown.
Rulings on weight limitations have been around for many decades, and it was around the 1960s when the Federal Aviation Administration made the ruling that aircraft with a maximum structural takeoff weight and maximum structural landing weight ratio exceeding 1.05 require a fuel-dump system. This affected notable models such as the Boeing 727 and Douglas DC-8, and such aircraft implemented technology that would permit a fuel jettison to be conducted for safe landing. As newer aircraft increased their weight with advanced engines and apparatuses, this ruling has been adjusted over time.
For a majority of aircraft featuring a fuel jettison ability, specialized nozzles are situated on wings. In the instance that fuel needs to be dumped as a result of an emergency, the pilot can activate a system which uses fuel pumps to expel fuel from the nozzle and into the atmosphere. This generally means a few tons of fuel dumped in a matter of minutes, but safety features ensure that there is a limitation to how much is expelled in a fuel dump to guarantee a safe amount to finish the flight.
While the dumping of such large amounts of fuel is not good for the environment, there are certain ways in which pilots try to mitigate the effects. For example, pilots are directed to only dump fuel at a safe height above the ground, and they are supposed to only expel fuel when they are in a remote area away from people and surrounding aircraft. Generally, fuel is dumped over the sea at altitudes exceeding 5,000 feet, meaning that fuel should vaporize before it has the chance of reaching the ground in a liquid form. Only in select situations has fuel been improperly dumped at altitudes and in areas where it should not have.
As alluded to prior, not all aircraft feature fuel dump systems, especially narrowbody aircraft and most regional jets that can effectively carry out various critical maneuvers to land while having a high weight. For aircraft that may not have fuel dumping capability but need to conduct a landing, the pilot may be able to just circle around the landing area to burn enough fuel to make it safe for landing. While this can take much longer than dumping fuel, it does keep the environment much cleaner as compared to the alternative.
A dump-and-burn is a related process to standard fuel dumping, though it is something that is not typically used for emergency procedures. A dump-and-burn utilizes the same method of fuel dumping, albeit directing the expelled fuel into the aircraft’s afterburner to create a large flame behind the vehicle. This is often used by aircraft that are carrying out the procedure for entertainment, such as for an air show, Olympic game, or similar celebration. Instead of the fuel dump nozzle being situated on the wing, it will be placed between the engine exhausts for safety and ease of burning.
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