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## Adding weight without Index Units

• bchappell17
• Topic Author

### bchappell17 created the topic: Adding weight without Index Units

Hey guys,

Just been doing an online performance exam and I have come past three questions worded similarly like this one.....

Given the following data for a charter flight in an ECHO aeroplane: -

Empty weight + pilot = 2109 kg
Fuel on board at TAKO = 300 litres
Flight fuel to first intended landing point = 110 litres
Fixed reserve = 15 gallons
Taxi allowance = 3 gallons
The maximum weight of baggage (ignoring balance) that may be carried is closest to:

A. 481 kg
B. 521 kg
C. 629 kg
D. 320 kg

The answer is A (481 kg)

It confuses me when it states the fuel onboard at takeoff is 300L but does that include the fixed reserve, variable and taxi allowance?

Any help would be appreciated, cheers.

• John.Heddles
• Offline
• ATPL/consulting aero engineer
• Posts: 477

### John.Heddles replied the topic: Adding weight without Index Units

It confuses me when it states the fuel onboard at takeoff is 300L but does that include the fixed reserve, variable and taxi allowance?

This can only reasonably mean the total usable fuel at takeoff. That is to say, all the fuel you started with less start and initial taxi. Hence it will include FR, VR, final approach and landing, and taxi in plus any margin fuel.

Unusable fuel is included in the empty weight and doesn't figure in any fuel calculations unless the question makes some specific reference. Note that, that you might just be able to use some of the unusable fuel in steady flight ... but you can't plan on doing so.

Engineering specialist in aircraft performance and weight control.
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• Posts: 2155

### bobtait replied the topic: Adding weight without Index Units

The question gave you the fuel on board at take-off as 300 liters (213kg). That is the actual fuel in the tanks so it includes all reserves and margin fuel but not the taxi fuel since the fuel given was at take-off (the 3 gallons taxi fuel is irrelevant).

The Echo has a ZFW limit of 2630kg and you are carrying 213kg of fuel.

The Echo has a maximum structural landing weight of 2725kg and the fuel burn-off to the first landing is 78kg.

You are landing weight limited at 2803kg.

2803 - all the fuel = 2590kg so you are not ZFW limited

2590 - pilot and empty aircraft = 481kg.
The following user(s) said Thank You: bchappell17