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Lack of Fuel (and other fuel based issues)

A lack of fuel (also known as a fuel shortage) is a state in which the aircraft is running low on fuel and may not have sufficient fuel to make additional maneuvres (such as holding) at the arrival airport.  In less serious cases, the aircraft may not have enough fuel to make it beyond the destination airport and then on to the alternative.

Causes 

  • Poor preflight planning
  • Unexpected inflight weather
  • Delays at the departure airfield (long holding times on the ground)
  • Delays inflight – having to hold on numerous occassions enroute
  • Fuel leak

Take some time to think about each of these causes and try to explain how they could lead to a lack of fuel.

Considerations

When we suspect that we might have a lack of fuel, we need to consider the terrain that we will have to fly over and also consider the terrain at the destination airfield.  For example, if the destination airport is in a mountainous area, or an area of high ground, we might consider diverting to a closer airfield or an airfield that has better terrain in the event that an emergency landing has to be made off of the airport.

The position of the aircraft also has to be taken in to consideration as we might need to modify the way in which we approach the airfield and how we will speak with ATC.  We might, in serious cases, need to consider making a straight in approach to a runway with a tailwind if we do not believe that we have enough fuel to make a full ILS procedure.  In order to conserve fuel, we need to calculate if it might be possible to make a “thrust idle” descent in order to use less fuel during the descent phase of flight.  In some extreme cases, we might also choose to put our flaps and landing gear down later than usual in order to save fuel due to the reduced drag of the aircraft.

Endurance/Fuel Remaining

Aircraft endurance is the amount of time that the aircraft can fly with the amount of fuel that it has.  For example, an Embraer 145 which full fuel might have an endurance of 4.5 hours.  Meaning that after 4.5 hours it will have used all of its full using a normal flight envelope.

Inflight endurance can be calculated by know how much fuel you have and how much fuel you are burning per hour.

For example.

Aircraft A is in the cruise and has 5 tonnes of fuel. It is burning 2.5 tonnes per hour.  the endurance is 2 hours.  This calculation does not take in to account the fuel burn at later stages of the flight.  The endurance when calculated correctly will be slightly longer as we will use less fuel in the descent.  However, other factors could reduce the endurance enroute, for example we may be requested to fly at a lower altitude, this lower altitude will reduce our endurance because the denser air will increase the drag of the aircraft.

Headwinds and tailwinds do not have an affect on aircraft endurance as endurance is about time and not distance.

Headwinds and Tailwinds DO have an affect on aircraft range however.

Other Common Fuel Related Problems

Fuel Exhaustion:

The aircraft has totally run out of fuel.  The engines will flame out and the aircraft has now become a glider!

Fuel Starvation:

Fuel starvation is related to the engines of the aircraft.  In the event of a fuel starvation the fuel can not get to the engines.  Fuel Starvation can be caused by a variety of reasons:

  • A blockage in the fuel line
  • Contamination in the fuel
  • A broken fuel pipe that is leaking fuel
  • A blocked fuel filter
  • A broken fuel pump
  • If the aircraft is inverted and has no inverted fuel/oil system, the fuel will not be useable

Fuel Contamination:

There is something else in the fuel other than fuel itself which will obviously effect engine performance, and in serious cases can also stop the engines from working.  Common contaminants are:

  • Water
  • Oil
  • Sand (Areia)
  • Rust (Ferrugem)

Some other “bizarre” contaminents have been found in fuel tanks including (dead) birds, mice, insects and in one case, a cat!

Here is a fantastic video from Baltic Aviation Academy highlighting the most common fuel problems in jet aircraft.  It is great for learners of Aviation English due to vocabulary and the presenters accent, which is from Eastern Europe.

Airport Fueling Facilities

At airports there are two main ways of refueling.  Refueling can be done either from a fuel truck, which is a dedicated vehicle that carries fuel with it to any point on the airport at which an aircraft needs to be refueled

Many larger airports have an integrated refueling system, in which the fuel is stored in underground resevoirs and is fed in to the aircraft from fuel pipes that can be found at the gate (see below)

Using this system, the truck works as a pump that sucks the fuel from the resevoir and feeds it in to the aircraft.  This is considered to be a much les dangerous system as the trucks are not driving around full of fuel and so, in the event of a collision, the chance of an explostion is much lower.

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