Following on from a previous question from MIDO about flight fuel can someone please clarify what is meant by Fixed Reserve fuel. CAAP 234-1(1) and draft CAAP 234-1(2) both suggest that the reserve fuel is calculated at the holding rate

Looking through CAAP 234-1(1) the fixed reserve is defined as an amount of fuel, expressed as a period of time holding at 1500' AAL ...


The draft CAAP 234-1(2) goes on to define the fixed reserve as the amount of fuel, expressed as a period of time, required to fly at holding speed at 1500' AAL ...


Notwithstanding the above, the VFRG exercise below indicates that the fixed reserve is calculated at cruise fuel flow - not the holding fuel flow as defined in the CAAP



Have I misinterpreted CAAP 234 or is CASA trying to have it both ways!

I don't see where the confusion is. The fixed reserve has always been an amount of fuel that is sufficient to allow the aircraft to remain airborne for 45 minutes. It is left up to the operator to decide how to calculate that. The only requirement is that you are capable of 'hanging around' for 45 minutes. It is normal for light GA aeroplanes to calculate the fixed reserve as 45 minutes at normal cruise consumption rate.

That's because, for these types of aircraft, the difference between 45 minutes at cruise rate and 45 minutes at some reduced power setting is less than the fuel you throw away after you do a water check! The VFRG calculation you give above is an example only and is not meant to be taken as some kind of legal requirement.

Larger aircraft either stipulate the fixed reserve fuel flow in the company ops manual, or nominate a 'block' of fuel in gallons or litres to serve as the fixed reserve based on a reduced consumption rate. In every case, it must allow for 45 minutes airborne.

Thanks Bob

A few comments if I may!

It is left up to the operator to decide how to calculate that.
Surely most operators would use CAAP 234-1 which suggests using a holding rate FF - whatever that may be.

It is normal for light GA aeroplanes to calculate the fixed reserve as 45 minutes at normal cruise consumption rate.
That is how it was when I did my training back in the 70s. I don't know how that came to be, but there was no CAAP specifying a holding rate FF at that time

That's because, for these types of aircraft, the difference between 45 minutes at cruise rate and 45 minutes at some reduced power setting is less than the fuel you throw away after you do a water check!
This may be true for a very small single engine aircraft. For a heavier twin engine aircraft that would be one large water check.

On further investigation I did manage to find the answer I was looking for in your CPL Performance Supplement - see citation below.



Notwithstanding the above, I see no harm in calculating the fixed reserve at the cruise FF - however if looking for the minimum legal fixed reserve it should be calculated at the holding FF as specified in the CAAP.

I do acknowledge that CAAP 234 is advisory in nature and not law. That being said, the inclusion of CAAP 234 into the company fuel policy would make it law.

A few thoughts.

Your comments are completely valid. Most operators of larger aircraft do simply state in their company operations manual that the company's fuel policy is to comply with the requirements of CAAP 234.

There certainly is no harm in calculating the fixed reserve at cruise rate. That is entirely up to you unless you are restrained by your company's fuel policy.

I didn't really expect you to take the comment about water-check fuel seriously.

Most of you wouldn't recall the following mishap www.newspapers.com/newspage/121177792/ Jim had a very strange idea about reserves and how they should be calculated on his own aircraft (but was a bit more conservative on his day job at a local airline). It all turned a tad topsy for him on that occasion. Nice aircraft - used to belong to Lang Hancock, hence the registration. I clocked up quite a few hours in it but never would I go without enough (read "plenty of") reserve fuel.

Might I suggest that one needs to be a bit circumspect with light aircraft fuel gauging. Larger aircraft are a different ball game altogether but little birds are way too risky at low indicated fuel quantities in flight .. If you fancy gliding, probably a better strategy is to go fly sailplanes.

For the larger aircraft, a fingernail biting tale from our colleagues in the west is worth a read www.pprune.org/pacific-general-aviation-...years-ago-today.html. There has been a number of similar fuel incidents over the years with met surprises.

In the exams, fine, but please do be very wary of shaving reserves down in light aircraft in real time ... just not worth it.

In the exams, fine, but please do be very wary of shaving reserves down in light aircraft in real time ... just not worth it.
I could not agree more - I was looking at the subject of fixed reserves from a lawyers point of view. I personally would calculate the FR fuel at the cruise FF for a real world flight.

Notwithstanding the above, I believe that the FAA, NZ CAA and ICAO only require a 30 min FR for private day VFR operations - that does make the hair on the back of the neck stand up.

I found a short story in Australian Flying that may be of interest

CASA are currently considering reducing the fixed reserve to 30 minutes. With the limited fuel management systems available in GA and the vulnerability of relatively slow GA aircraft to wind and weather, you'd have to be nuts to skimp on fuel. A 300HP fuel-injected engine not properly leaned in cruise can chew up fuel at an alarming rate.

As the old saying goes. The only time you have too much fuel is when you're on fire!