General:

In the ATPL flight planning exam you may be asked which operation requires the most fuel to be on board for the flight. The operations you need to assess are:

• Normal operations.

• One engine inoperative ETP operations.
  
• Depressurised ETP operations.

Whichever of the three requires the most fuel is the fuel we will load on board prior to startup (ie: ramp fuel).
In taking the larger of the three amounts, should any of the operations occur we will have sufficient usable fuel to cover it.

You will not have time to calculate all of them in exact long hand fashion, so must rely on rough estimates of each to find which needs the most fuel. You will need to know the company minimum reserves to get the right answer. You can find them on page 1-16 of the B727 manual.

Some basic points:

Depressurised Ops;

• You must provide for an airport that is at least "Acceptable" (ie: above the landing minima, but may be below alternate minima). You can use a "Suitable" airport also (one that is above alternate minima).
  
• You do NOT need to allow holding fuel for Works in Progress (WIP), or Traffic. Provided the airport is at least "Acceptable" (ie: NOT closed due to weather below the landing minima) you will NOT need to carry weather holding either.
  
• In calculating this you allow for fuel to fly out to the Depressurised ETP in the Normal Ops configuration, and from there to an Acceptable airport. Always fly out to the ETP Normal Ops !
  
  
  One engine Inop
  
• You must provide for an airport that is "Suitable," or Acceptable becoming Suitable if the weather holding (Inter or Tempo) is carried to allow an improvement.
  
• You only carry the weather holding fuel (if required), and NOT WIP or Traffic. You will be given priority on arrival by ATC if you have an engine shut down.
  
• Whichever airport you are considering using as a 1 engine inop alternate (ahead or behind you) has the largest weather holding fuel requirement (Inter or Tempo) dictates the weather holding fuel you will carry. That is, carry the weather on the airport that requires the most holding fuel. If you proceed 1 inop to the airport with the lesser weather holding fuel requirement, you will have margin fuel, which is fine, and a lot better than arriving at the other airport with insufficient weather holding fuel.
  
  
  Normal operations
  
  This assumes the flight goes according to plan, with no cabin depressurisations, and no engine failures. Fortunately this is the 'normal' occurrence in real life.
  

• The same standard of airport weather is required for Normal Ops as is for 1 Engine Inop Ops (ie: it must be at least a "Suitable" airport, or become Suitable with the required weather holding  fuel to allow for a weather improvement).

• You must carry WIP, and Traffic holding fuel if stated in the question.

The ATPL exam question will most likely ask you to specify which operation requires the most fuel, but NOT the quantity of fuel. So the answer options will likely be written statements, NOT number answers.

This means we can be quite rough in our calculations, as treating each of the operations with equal dis-respect will see the order of favouritism and outcome remain unchanged.

Some rough Specific Air ranges are used for the B727. They are:

Let us look at an example:

Example.  Given:
Flight from departure airport "A" to destination airport "C". Distance "A" to "C" 1, 000 nm.
Between airport "A" and "C" is airport "B", which the flight will overfly. Airport "B" is on track, 300 nm form airport "A".

Airport Status:

Airport "A" ... Acceptable, becoming Suitable if Wx holding is carried to allow for TEMPOrary deteriorations below alternate minima. Additionally, notams indicate a 20 minutes traffic holding requirement, and a 15 minute Work in Progress holding requirement during the period of possible use.

Airport "B"... Acceptable for the period of possible use. No other holding requirements apply.

Airport "C"... Acceptable for the period of possible use, becoming Suitable if Wx holding fuel is carried to allow for INTERmittent deteriorations below alternate minima. Additionally, notams indicate a 15 minute traffic holding requirement during the period of possible use.

Question: Which of the answers listed best represents the fuel requirements for this flight ?

a. Normal operations fuel requirement exceeds the 1 Inop requirement, but NOT the Depressurised fuel requirement.
b. One engine inoperative fuel requirement exceeds both Normal and Depressurised fuel requirements.
c. Depressurised operations fuel requirement exceeds the Normal operations requirement, but NOT the 1 Inop requirement.
d. Normal operations requirement exceeds both the Depressurised and 1 Eng Inop fuel requirements.

Route Sector Winds and Temperatures (RSWT) will almost certainly be quoted in the question, but can be ignored.

The most fuel critical position to lose the cabin pressure will be approximately half way between airports "B" and C".

The most fuel critical position to lose an engine would be approximately half way between "A" and "C". Remember that you cannot plan to use airport "B" for 1 Engine Inop operations as it never get's above an acceptable airport during the period of possible use. You must fly on to "C", or return to "A". You will need to carry the weather holding on whichever of those two airports has the greatest weather  holding requirement. In this case departure airport "A" ... TEMPO = 60 minutes = 4, 000 kg.

With normal ops you carry all holding on your destination airport only.

The Normal Ops flight profile:

The way to calculate the rough 'Flight Fuel' from departure to destination airports is to multiply the number of miles by the normal ops (all the way) SAR of 10.0 kg air nm, then add an arbitrary 1, 500 kg to the result to allow for extra fuel burnt in the climb, and approach.
In this case we have (1, 000 nm x 10.0) + 1, 500 kg = Flight Fuel of 11, 500 kg.
Next add the reserves. Refer to Normal Ops fuel summary.

Normal ops Ramp fuel Summary

The Depressurised flight profile:

For this operation we can use airport "B" (acceptable). There are infact two depressurised ETP's possible. One is approximately half way between "A"  and "B", and the other is approximately halfway between airports "B" and "C". The one furthest from departure usually requires the more fuel.

Plan to fly normal ops out to half way between "B" and "C" (ie: 10.0 kg per air nm), then the rest of the distance on to "C" in the depressurised configuration (ie: 12.5 kg per Air nm). refer to profile below.
Remenber you can either go on to "C," or return to "B", you cannot split the aircraft in half and have half the pax go on and half go back to "B".

The flight fuel requirement in this case is:

• Normal Ops for (650 nm x 10. 0 kg/air nm) + 1, 500 kg = 8, 000 kg.
  
• Depressurised 350 nm x 12.5 kg/air nm = 4, 375 kg.
  
  
  Total flight fuel then is 12, 375 kg. To this you add the reserves for depressurised ops. Refer to fuel summary.

Depressurised ops Ramp fuel Summary

The 1 Engine Inop Profile:

For this operation, we do NOT have the option of using airport "B", as it remains only Acceptable
during the period of possible use. We must either RETURN to airport "A", or continue ON to airport "C".
In other words, for 1 Inop operations you must consider that airport 'B" does NOT exist !

The 1 Engine Inop ETP is then approximately half way between airport "A" and airport "C". (ie: approx 500 nm past "A". The flight fuel then is made up of normal ops  fuel from "A" to the ETP, then in the 1 Engine configuration ON to airport "C" (or back to "A"). Refer profile below. Because the flight time BACK and ON are the same from the ETP, the flight fuel BACK and ON will be approximately the same.

Remember that you will carry the weather holding fuel only on the airport that requires the most weather holding (in this case airport "A" with 60 min = 4, 000 kg). No traffic or Works In Progress holding is required.

The flight fuel requirement in this case is:

• Normal Ops for (500 nm x 10. 0 kg/air nm) + 1, 500 kg = 6, 500 kg.
  
• 1 Eng Inop Ops 500 nm x 10.7 kg/air nm = 5, 350 kg.
  
  Total flight fuel then is 11, 850 kg. To this you add the reserves for 1 Engine Inop ops. Refer to fuel summary.

1 Engine Inop ops Ramp fuel Summary

A second training editorial will cover the fuel requirements when the destination requires an alternate. This is scheduled to appear within the next two weeks. Watch this space !

Best regards

Rob Avery