Yes, they do.
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Nice one, thanks
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The FMC calculates fuel in tons with only one decimal and it rounds conservatively.
Your FPL says you need 8176Kg and you request 8200Kg. It’s a hot day and you used the APU during the whole turnaround. Your taxi is delayed after pushback due to ramp congestion. Then you’re n.5 on departure. You reach the holding position after using more TAXI fuel than expected and you see the message “Using reserve fuel”. Now you have to return to stand to get more fuel because your fuel indicators decimal number changed by 0.1T due to the way it rounds conservatively… Embarrassing.
A return to stand is far more expensive (delays, more fuel burnt, risk of CTOT, stand fees, fuel bowser fee) than adding 100Kg more on those rare flights that we depart with just standard OFP fuel. Keep in mind that most of the times we load more fuel than the OFP says whenever there’s a good reason and there usually is.
In my case it’s also defined in our operations manual. On first departures in the morning the airplane will be pre-fueled before the pilots arrive. This is to avoid delays. Our ground ops staff will always pre-fuel the airplane with at least OFP Block Fuel rounded up to the nearest 100 kgs + 100 kgs as a minimum.
So Block rounded to the nearest 100 kgs + 100 kgs is considered a standard fuel load that we’ll be happy with whenever there’s no sound operational reason to load extra fuel. Anything on top of that is considered PIC Discretionary Fuel and on our EFB a dropdown menu will activate for us to type in the reason for the extra fuel requested (eg. WXR, RWY CHG, DEICING, CTOT, PushAndHold…)
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A higher flap setting would allow you to spend less time on the ground but will affect your initial climb performance. A take off can be limited in different ways. One is, like you said, the length of the runway. But it can also be limited by initial climb performance (obstacle affecting second segment climb gradient). Depending on what’s limiting the departure we will make a decision on how to depart (different flaps settings, full thrust, improved climb and second segment extension or even departing with bleeds off).
On 99.9% of the runways I operate from the airplane can depart safely with the standard F5 and various degrees or thrust reduction. In 6 years of 737 opearation I’ve only used flaps other than F5 maybe 10 times. There are some departures that are climb gradient limited in which a F1 departure will be necessary. F1 departures increase the risk of tail strike due to reduced tail clearance.
I do remember some cases where we always used F25 for take off but not for performance reasons. On some Ukrainian runways the surface was so incredibly bumpy that we used the highest flap setting to unstick the airplane from that runway as early as possible. These were incredibly long and wide runways but very poorly maintained. Seeing the kind of airplanes they had it makes sense.
When performance limited we explore options in this exact order:
-Activating IC/EXT speeds: Increased Vr for improved climb + Extension of 2nd segment (Higher MFRA or Engine Out Acceleration Height).
-Lower flaps when climb limited or higher flap settings when runway limited.
-No engine bleeds take off (this one is last because it involves supplementary procedures and reconfiguration of the A/C panel shortly after take off).
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Most interesting thanks! Is full thrust achieved by taking off in manual rather than TO GA or do I need to change thrust settings in the MFC?
Forgive me, but the way you’ve described that makes literally zero sense.
Obviously I know how the FMC calculates fuel. I’d hope we can agree that whilst the FMC is a guide, what you’ve uplifted and the fuel on your gauges vs your plan is what matters at the end of the day.
That aside, the scenario you’ve described is exactly what contingency fuel is for. In the exceptionally infinitesimal chance you were to burn all your contingency fuel over and above your taxi fuel during taxi (and I’ve never got close even once in 11 years flying the 737 and 9 years of flying the 787) then that is why, assuming you meet the criteria to do so, you’re able to commit to your destination and dispense with your alternate, making sure you always have enough fuel to land with Final Reserves intact. If the weather wasn’t good enough to do that then you wouldn’t likely have taken flight plan fuel anyway. IIRC correctly Contingency Fuel on the 737 was 5% of trip or 200kgs as an absolute minimum. That’s more than enough to account for any unforeseen taxi delays on a 737.
100kgs is a rounding error and there’s absolutely no chance I’d return to stand from the holding point for the sake of that amount. Or are you saying the figure you enter as reserves in to your FMC is Final Reserves + Alternate + Contingency? Obviously that would be incorrect, because that isn’t your reserve fuel. I know airlines have variances on the way they do things but assuming you operate in Europe we’re all operating under the same regulations, so the bigger picture stuff is the same.
No, full thrust is achieved at 26K without assumed temperature. Some airlines have the option to bump to 27K.
What I describe is what’s written in the OM(A) of a 550 airplane airline. That should be good enough a reason for you to not be so defensive about it. This is how it’s done where I work now. When GOPS pre-fuel the airplane for us they round up to the nearest 100Kg and add 100Kg on top of that to make sure we never take off with less than take off fuel in case of having used more fuel on the ground as calculated by LIDO (which is not what contingency is for). Simple as that. In most cases we’ll add fuel on top of that anyway.
And of course in reserves we enter the sum of final reserve+alternate. Why would that be different?
For ground operations we have our taxi fuel. This is a figure that varies and it’s calculated by LIDO based on statistics. In some airports it’s a very confortable figure (300Kg out of EIDW) or a bit tight (117Kg in LEVC).
Maybe “using reserve fuel” is an exaggeration but I do remember situations where it could have happened (CTOT expired at the holding point and having to wait there an undefined amount of time).
I’m joining another airline in April. If things are different there I’ll make sure to describe it to you for approval.
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I’m not being defensive in the slightest, but clearly we have a different understanding of what contingency fuel is and when it can be used. Are you saying that your operator doesn’t allow you to burn contingency fuel on the ground? That’s a complete new one on me as obviously mine does. It’s for unforeseen changes to the plan and can be used at any time after the aircraft has dispatched.
The point I was making is this;
Of your 550 aircraft let’s say 125 of them are not flying at any one time. Of the remaining 425 aircraft let’s say each airframe flies two 2 rotations of 4 sectors per day, so 8 sectors total. On each of those 8 sectors you are loading an extra 100kgs of fuel. So, per airframe, per day you are loading 800kgs of extra (and dare I say unnecessary) fuel. Multiplied by 425 airframes that is 340 tonnes of extra fuel per day, or 124,100,000 tonnes of fuel per year your airline loads for no real reason I can see.
A quick straw poll of mates from a variety of carriers suggests they’ve never heard of this either. Their answer was universally ‘you’d burn the contingency, obviously’.
I’m not here to discuss whether my company policy is better or worse than your company policy. It’s their airplanes. I fly them how they want me to and arguing about that is pointless when things are on the safe side. We’re talking about the largest operator in Europe and third in the world by passenger volume. I’m pretty sure they know what they’re doing.
If company policy is for GOPS to pre-fuel to BLOCK rounded up +100Kg before we tell them our final figure (which it more often than not higher than OFP block) why should I or you question this? When I start flying at my next airline I will follow their OM(A) and the day I start my own airline I will consider other options.
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I questioned it not because of your airlines policy, but because you don’t seem to understand what contingency fuel is. What you’re saying now has nothing to do with your original answer. Out of pure curiosity I simply asked you why you loaded an extra 100kgs and rather than say ‘the ground ops people pre-load flight plan fuel + 100kgs on the first flight of the day to prevent fuelling delays to the first rotation’ you said this;
What you’ve shown me in the ops manual is clearly a policy to prevent fuelling delays to the first rotation, something that is very common across many airlines. You then said this;
Unforeseen delays after dispatch is absolutely what contingency fuel is for. I’m not questioning the policy at all, I’m questioning your first answer to my original question
That’s my last post on the matter.
PRE-FUELING is done to prevent delays.
What we’re discussing is not the pre-fueling itself but the reason for the 100Kg on top of the already rounded figure. I assume it’s done to prevent taking off with anything less than planned take off fuel. But who knows. I don’t care why GOPS loads 100Kg on top. It’s not my problem. It’s extra fuel and I will not complain about extra fuel.
This is how it’s done in my current airline. I couldn’t care less what you think. Now other users of the forum know that there’s a least one airline out there, and a very large one, that does things this way.
You are a strange individual with a very weird ego. If I saw the comment of a fellow pilot on here or anywhere else that is different to what I see in my day to day operation I would think “Oh, maybe they do things differently in other airlines”. I wouldn’t answer saying “THAT MAKES NO SENSE, YOU DON’T KNOW ANYTHING!”
In other words. I’m done with you and please stop replying to my posts.
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You are making this sound like just because they are loading extra fuel, that they are also burning it. I don’t see it that way. If extra fuel is loaded, then the next refueling will take that into account and load fuel based on what is estimated to already be on the aircraft.
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I thought his argument was not that they are burning it, but that they are hauling it. The extra weight of it being a cause for higher fuel consumption.
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I doubt that an extra 100 kilos is going to make much of a difference.
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It is, but <200kg is just insignificant noise in the overall list of variables that affect fuel consumption of real world aircraft and real world engines flying in an environment composed of real world winds.
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I’m certainly not arguing a case here, just noting what I interpreted the argument to be about.
The Wikipedia article about a largest European airline has a section regarding fuel “incidents” occurring in 2012. Perhaps it is the outcome of the investigations over said incidents that has led to a change in fueling policy that is unique to that airline.
Again, I’m not arguing anyone’s side here, I’m just a curious bystander who’s been following this discussion.
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I try to pop up panels in PMDG.(right Alt and left click)
Problem is they appear in full screen, instead of windowed screens.
Any help please?
Thanks in advance
That article is a bit misleading.
If you want to have a better understanding about what happened that day you can read the AVHERALD article and the comments. I’m happy to comment about it.
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I was back in the day a real 737 and 747Captain. Mt experience with the PMDG NG X series is that it’s pretty good and I can fly it like a real aircraft. Always we have limitations in our control setups and I’m still tuning those. Flying the 747 we were usually given skinny but legal reserves, sometimes I had to point out that Sydney noted to expect 20 minutes of holding. The tightest go around you could fly used about 3500 kg! On our dispatch paperwork we were supplied with a last minute change correction for added fuel or payload to fuel burn expressed as so many KG/1000KG.
There are a few items in this bird that I am still sorting out, but then’s it’s not a real class/ sim instruction program.
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