6 minutes contingency

[Banana Joe]

Yesterday on our OFP we had a 6 minutes contingency. I have not found anything in the IR-OPS and our OMA that references a 6 minute contingency, but only a 5% of trip fuel or 5 minutes at 1500 ft AAL above destination aerodrome.

Any hints?
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[FlyingStone]

Could it be that 5% of trip fuel was equal to 6 minutes?

[Banana Joe]

No, the actual value corresponds to 5 minutes. It can't be a typo error since the flight plan is computer generated and the following sector had 5 minutes.

[Mad (Flt) Scientist]

Rounding to tenths of an hour?

[swh]

Do you use PBC ?

Do you have planned mandatory fuel unused at the destination ?

How much fuel did you actually land with ?

[FlightDetent]

Another thread that is worth less without pictures :E.

[Banana Joe]

Do you use PBC ?

Do you have planned mandatory fuel unused at the destination ?

How much fuel did you actually land with ?
Pardon? PBC?

Our flight plans are for max payload, but the actual payload is often less than that so we always have some extra fuel when we arrive at destination, and we did indeed land with fuel well in excess of minimum diversion fuel. 4 tonnes if I remember well.

But I don't understand how a 6 minute contingency comes from, it is s the first time I've seen it.

[FlyingStone]

I think an email to your flight planning department will get you the answer within minutes.

Without your OFP and OM-A, we can just keep guessing...

[srjumbo747]

ETOPS? Did you use it?

[Dirigible]

PBC, or prescriptive based compliance is allowable for contingency fuel planning if the Operator can demonstrate to the satisfaction of the Regulatory Authority that fuel is allocated as described in the Standards and Recommended Practices. (ICAO Annex 6)

The ICAO Document 9976, Flight Planning & Fuel Management Manual (FPFM) states:

4.18.6 An example involves an operator that does not carry five per cent contingency fuel exactly as defined in Annex 6, Part 4.3.6.3. An Authority may consider an operator in prescriptive compliance without the need for an operational variation if the terminology and contingency fuel calculation method used results in a demonstrably equivalent (or greater) amount of fuel. Conversely, an operator may be deemed out of compliance or require an operational variation if the terminology used is largely inconsistent with 4.3.6.3 c) and/or the calculation method used results in a lesser amount of fuel.

As your 6 minutes of contingency exceeded the typical ‘5% of trip fuel or 5 minutes at 1500’AAL’ fuel then you are in compliance with the regs based on PBC. I do agree however that an e-mail to ops would satisfy your curiosity, as technically they are not implementing what is documented in your OMA.

[Banana Joe]

ETOPS? Did you use it?
No, it's a 737-400 flying within Europe.

[Banana Joe]

I've done some further research and it may be that the contingency fuel was based on city pair/aeroplane combination statistical method.

an amount of fuel based on a statistical method that ensures an appropriate statistical coverage of the deviation from the planned to the actual trip fuel. This method is used to monitor the fuel consumption on each city pair/aeroplane combination and the operator uses this data for a statistical analysis to calculate contingency fuel for that city pair/aeroplane combination

CAT.OP.MPA.150

I will of course enquire my flight ops department.
AMC1 CAT.OP.MPA.15

[champair79]

At BA, we call it SCF (statistical contingency fuel). We usually operate to a 95% coverage which allows you to take flight plan fuel in the knowledge that it’s highly unlikely you’ll need more unless the weather is particularly bad etc etc.

If they used this method for you, I’m surprised you were not aware of its existence though. It should be explained in OM-A I would’ve thought.

champ

[swh]

I've done some further research and it may be that the contingency fuel was based on city pair/aeroplane combination statistical method.

an amount of fuel based on a statistical method that ensures an appropriate statistical coverage of the deviation from the planned to the actual trip fuel. This method is used to monitor the fuel consumption on each city pair/aeroplane combination and the operator uses this data for a statistical analysis to calculate contingency fuel for that city pair/aeroplane combination

CAT.OP.MPA.150

I will of course enquire my flight ops department.
AMC1 CAT.OP.MPA.15

This is totally legal under the ICAO 9976 Flight Planning and Fuel Management Manual which EASA has adopted.

The EASA rules I think are

(c) Contingency fuel, which should be the fuel described in (1) or (2) below, whichever is higher:
(1) either:
(i) not less than 3 % of the planned trip fuel or, in the event of in-flight replanning, 3 % of the trip fuel for the remainder of the flight provided that a fuel en route alternate (fuel ERA) aerodrome is available; or
(ii) an amount of fuel sufficient for 20 min flying time based upon the planned trip fuel consumption; or
(iii) an amount of fuel based on a statistical method that ensures an appropriate statistical coverage of the deviation from the planned to the actual trip fuel; prior to implementing a statistical fuel method, a continuous 2-year operation is required during which statistical contingency fuel (SCF) data is recorded — note: in order to implement a SCF on a particular city pair/aeroplane combination, sufficient data is required to be statistically significant; this method is used to monitor the fuel consumption on each city pair/aeroplane combination, and the operator uses this data for a statistical analysis to calculate the required contingency fuel for that city pair/aeroplane combination; or
(2) an amount to fly for 5 min at holding speed at 1 500 ft (450 m) above the destination aerodrome in standard conditions.

What you would have loaded is the 5 minutes, your statistical contingency must be less than that amount. This typically occurs where the departure and arrival procedures have complicated/inefficient routing (like maintaining below 7000 ft for 70 miles, and then a zig zag STAR) which are there typically for loss of communications purposes. When radar identified significant shortcuts are normally available reducing the actual trip distance/fuel down significantly. Have a look at the planed trip distance compared to the actual distance flown on flight radar or similar. My guess is you are typically seeing a saving of around 100 nm over the city pair which is converted into contingency fuel via the statistical method.

[wiggy]

What you would have loaded is the 5 minutes, your statistical contingency must be less than that amount.

Unless I've miss understood the context of the OP in order to get the 6 min figure that is being queried isn't it the other way around?

[NARVAL]

Unless I've misunderstood the context of the OP in order to get the 6 min figure that is being queried isn't it the other way around?
Dear friends...
I am retired, thanks to a god who forgot to point his finger at me during my career...
I admire your knowledge, your professional curiosity and I love reading the tech logs.I wish you all the best during these difficult times. But here I feel compelled to say STOP!
Who cares about five minutes six minutes and statistical survey of approaches for the last fifty years?
Take a reasonable amount of fuel using your knowledge and experience. Never let the statisticians dictate you anything. Ask your copilot if he is happy with the fuel you decided to take. That's important. And stay cool...very cool...Aviation is a very simple art complicated by people who do not have a very happy life. And they are more obtrusive as times goes by...

[FlyingStone]

But here I feel compelled to say STOP!
Who cares about five minutes six minutes and statistical survey of approaches for the last fifty years?
Take a reasonable amount of fuel using your knowledge and experience. Never let the statisticians dictate you anything. Ask your copilot if he is happy with the fuel you decided to take. That's important.

You also need to be legal. You need at least the minimum amount of fuel on board, and sometimes this includes "statisticians dictating you", if one's employer uses such method.

[Fly3]

Narval.

Well said sir.

[AerocatS2A]

Dear friends...
I am retired, thanks to a god who forgot to point his finger at me during my career...
I admire your knowledge, your professional curiosity and I love reading the tech logs.I wish you all the best during these difficult times. But here I feel compelled to say STOP!
Who cares about five minutes six minutes and statistical survey of approaches for the last fifty years?
Take a reasonable amount of fuel using your knowledge and experience. Never let the statisticians dictate you anything. Ask your copilot if he is happy with the fuel you decided to take. That's important. And stay cool...very cool...Aviation is a very simple art complicated by people who do not have a very happy life. And they are more obtrusive as times goes by...
Quite right, however, questioning the nitty gritty of a computer flight planning system is good practice as it can sometimes uncover errors in the programming. I once discovered that our flight planning system was not applying a wind correction to the climb segment. It didn't normally make much of a difference but on one flight a 100 knot headwind at relatively low levels resulted in a plan that was significantly light on fuel. Question and understand the small anomalies because one day those small anomalies will be magnified into a big one. Maybe a one minute difference is a rounding error, maybe it's a consequence of rarely used section of the fuel policy, or maybe it is an error that is symptomatic of a larger issue. There is no harm questioning why your plan says 6 minutes instead of 5 even if you are actually taking 30 minutes of extra fuel.

[Trossie]

With the present price of fuel, just bung loads extra on anyway and don't worry about those little numbers!

[FlightDetent]

+1 Aerocat.

If Banana Joe's CFPs were legally calculated using statistical contingency, an observant and engaged person like himself would have noticed long ago.

Not to mention the OM part A explanation (which itself is a pre-requisite for its approval).

[Vessbot]

Good airmanship requires that we're 1) legal, and 2) safe; not one or the other. In so many discussions, when someone gets down in the weeds of legality, someone else pipes up about forgetting all that stuff and seeing the big picture, as if it's a forced choice and seeing the big picture requires ignorance of the technicalities. I think sometimes it may stem from the person giving the big picture advice, himself failing to see the even bigger picture that the details must be adhered to, regardless of if safety can be assured with or without them. One is not a replacement for the other, but this goes both directions. And other times I think it may stem from a desire to show off their street smarts or ages of experience.