737NG Low Fuel

[Dogma]

These days with us all flying around on vapors! How confident can I be in committing to the destination airfield and commencing the approach with about 1.2 tons ie Amber 600 each side!

If I go around will the power plants continue to produce power for my next "no go around" approach with 300 kg each side?

Any ideas, experience welcome

[BOAC]

1) Yes
2) Probably, but you have erred.

[Rainboe]

As far as I am aware, the aft main tank pumps should produce pressure almost down to empty, so you would still be in a situation where you had just under 30 minutes to dry tanks- a GO around to 1500' should not use a great deal. Actual unuseable fuel should be quite small, after all that is the aim of design! Carrying out the Low Fuel procedure should ensure you crash without asymmetric power (that's a joke!). I would have confidence that you could GA with 1200 and fly a circuit, though I might insist it was a short one!
I did Amber 760 recently. Not especially desirable, but at $150 a barrel, we are no longer tankers when not economical.

[Dogma]

BOAC - I hear what you are saying. However it is not uncommon these days. CRM is only 1800 in a lot of cases.

Thanks Rainbow and further info welcome. What about turbulence in these low fuel cases?

[BOAC]

Yes, D, but to go from 1800kg total to 600kg total would take some significant errors, don't you think? Perhaps you should be sure before you 'commit' that you will be able to land first time? Best not to get yourself into that 'statistical quagmire' you describe. We are beginning to go down the 'what if I get 2 emergencies' line and aviation is NOT designed to cater for that. As someone said elsewhere, if you are worrying yourself about that scenario, should you be flying at all?However it is not uncommon these days. - what is 'not uncommon'? 600 kg total, 1200kg total or what? A CMR of 1800kg should not get you anywhere near any of those.

The aft pump feed is only relevant during the g/a and accel. Once you either slow down or put the nose down for landing...................... In any case, providing they can find fuel in the tank, the motors will run without tank pump pressure.

Half of this problem (737NG) comes from the 'factory' (high) LOW setting at 907kg (discussed in another thread). Any yellow warning anywhere and people start twitching. 1810kg is a lot of fuel in reality. 1200kg is equivalent to 30 minutes holding. The Classic does not call for any drills until below 453kg on any side, and the NG burns less.

[blueoreas]

Our emergency fuel is 3000lbs and the final fuel(1500AFE to touchdown) is 300lbs.

[lederhosen]

After a lengthy period of flying into airports where go-arounds have been few and far between, I have recently been operating out of an airfield where they are much more common, due to weather and airfield facilities. It has rather focussed my mind on this subject.

I am a bit sceptical about the statement that a go-around to 1500' should not use a great deal. I suppose it depends what you mean by a great deal. But on the last three occasions (with a 737) it was between 600 and 700 kilos. Given the need to declare an emergency at 1200 kilos, or rather more pertinently if you believe you will land with less than 1200 kilos, obviously there is not a lot of margin.

You would have to be pretty brave (some might say foolhardy) to take minimum fuel under these circumstances, as I am sure most if not all would agree. The more interesting question is how much is then enough? If a go-around is a distinct possibility I favour taking enough to try an approach and then have enough to divert and land with some options left.

[Rainboe]

The structure of fuel reserves is usually of the order to fly to destination, go around and divert to alternate, plus Contingency (5% or 15 minutes holding), and land with 30 minutes left. As a planning minimum this is enough. As fuel becomes more expensive, you must tailor the cost of carrying any extra to your perceived risks on the day, as that extra fuel you carry every flight will hit the profit. You cannot justify this for the once in a blue moon event of a diversion through low fuel which may cost less than carrying extra fuel on average every flight. Remember, extra fuel mostly doesn't prevent that diversion. On most occasions when I have diverted, extra fuel merely delayed the inevitable.

[lederhosen]

I am in complete agreement that extra fuel costs money. I suggest 3.5% per hour for the extra carried on the 737 is a typical figure. So taking the proverbial fag packet and rounding up, a thousand kilos extra on one of our average flights costs 40 kilos.

If there are no perceived risks, as you put it Rainboe, then there is no problem taking flight plan fuel. However your suggestion that needing extra is a once in a blue moon requirement is a bit short of the mark in my experience. On those occasions 50$ as against the thousands for a diversion is reasonable insurance.

Maybe you are a management pilot and have access to all the statistics (lies, damn lies, statistics etc.). But the statement that extra fuel merely delays the inevitable sounds a bit subjective.

There are definitely two churches out there as far as extra fuel is concerned. The minimalists are in the minority in our company judging by our remaining fuel figures. But obviously I cannot see those in your company.

I definitely agree fuel and cost can be saved in this area. I guess where we disagree is in the size of the cost / benefit equation, when also factoring in safety.

[BOAC]

Where have I seen all this before (http://www.pprune.org/forums/showthread.php?t=328249).....................?

Well, that was the LAST time:ugh:

[lederhosen]

Are you suggesting

1. Rainboe and I have not read a thread which stretched to 5 pages (unlikely at least in Rainboe's case)

2. The subject is not interesting (in which case why did you reply to the original post)

Last time I looked Danny was trying to encourage debate by professionals. Does this somehow not qualify?

As an aside, most times I have posted something on Pprune that I considered reasonably thought through, the thread then died. Pprune does seem to thrive on controversy. So I am trying to get with the flow!

[Rainboe]

Mostly when I have diverted, I already had taken extra fuel. It did not change the outcome. last time I diverted, I held for over 2 hours at ARN waiting for fog to clear- it didn't and we wasted nearly 5 tonnes. We still returned to departure point having used up all our round trip fuel to get nowhere in 4 hours.

My estimation is that extra fuel, although nice to have, does not achieve half as much as people think. Personal opinions, but I get fed up with people wanting hundreds 'for Mum' to a non-delay destination on a good weather day. I used to do many long range flights from the Far East to UK with restricted minimum fuel. I never had a crisis. Ran low sometimes, but carrying extra on flights like that costs big time. I didn't feel additional was worth the cost.

Itmight be interesting to consider if you have diverted, had you already taken extra? Would carrying even more have saved the diversion? It's not as clear cut as 'carry extra=no diversion'.

This for unexpected problems of course

[lederhosen]

If you have the luxury of flying a route regularly you can see how generous or not the flight plan fuel is, regular short cuts and better cruising levels for instance. We have an interesting situation, where the plans for our NGs are spot on, but the classics tend to need a bit extra. Anyone else have this problem?

At the end of the day I believe strongly in the red face test. If you can explain at the end of the day why you did what you did and not go red in the face explaining to your superiors, then things are OK.

I see the self evident target as landing at my destination as close to minimum diversion fuel as often as makes sense. I think landing with less is at least as bad as landing with more. In many cases landing with more reflects that you have saved fuel rather than wasted it!

[BOAC]

Carrying ABEFM does not guarantee you will not g/a with 600 a side.Are you suggesting
1. Rainboe and I have not read a thread which stretched to 5 pages (unlikely at least in Rainboe's case)
- Yes, well should have2. The subject is not interesting (in which case why did you reply to the original post) - No. The SUBJECT was interesting. Hence the interest. ABEFM is not - here in this thread.

The thread is not "a closed subject" but there is this awful cemetary-like atmosphere of dead bodies being dug up again. What using 5 tonnes of fuel holding has to do with a low fuel g/a I cannot see.

To attempt to answer your question, Dogma, turbulence will be a factor, although the overall 'average' fuel available to the feed pipes will be sufficient as it sloshes around. Attitude and accel/decel are more crucial, hence the QRH.

[lederhosen]

I get it now BOAC, you were declaring thread creep! Why did you not say so clearly in the first place?

Not particularly sure I agree, but it is your train set.

[frontlefthamster]

We'll all stop flying around 'on vapours' after about three hull loss accidents with a couple of hundred dead each time. Anyone care to start a sweep on a date? My betting is that it won't be anytime soon.

Until then, the drill is simple: pumps on, crossfeed open, and mayday.

[Rainboe]

Er......how many times has that happened? Do you expect it to? Why? If you carry fewer reserves, you must make your decision earlier. Extra fuel gives you extra thinking time. That optional luxury of extra thinking time is becoming increasingly expensive. Therefore you must take your decision earlier, and save the decision to take extra for when it is really necessary.

[glad rag]

As a non "operator", looking from the outside in, so to speak, I think the whole issue of low fuel levels and how you professionals "cope" and the difficulties that it brings with it actually comes down to experience.

Lots of experience.

The trouble is now, with foreshorted training designed to meet those training "targets" the flying hour/experience ratio is going the wrong way, IMO.

Please feel free to correct me as you feel fit!

glad rag.

[Rainboe]

The biggest problem is when you follow mandatory procedures and are obliged to declare Mayday, Pprune gets hold of it and it is looked on as crew shrieking 'My God, we're in distress! Call out International Rescue, call out the Coastguard, call out everybody with a uniform with a Red Cross!' when it is simply a procedural thing, and compulsory. What is needed is a new word to convey 'low fuel situation- not about to die (but that possibility is not excluded).'

Won't be nearly so exciting in pprune though.

[Dogma]

Thanks for the answers, suggestions and conjecture.

BOAC .. CMR = 1800 and you say that commencing the approach with a predicted landing fuel of 1200 = problem? ie you have committed and have breached no legal limit.

I want to know what the perceived wisdom is concerning arrival fuel. Personally I feel planning to arrive with a CMR of Low Fuel with NO mitigating factors is not correct or commensurate with good airmanship.

That said if you are up against it (Low Fuel), due enroute problems, should you have a gear, flap, slat, hyd, cont, brake problem then you need to be absolutely clear about your rapid course of action!

[lederhosen]

The last time it actually happened, if I remember correctly, was the Avianca Boeing in New York that flamed out on its second attempted approach into JFK. Links nicely to another current topic of crew not being able to communicate properly in English.

[BOAC]

If you read the other thread you will realise that CMR can be less than 1800kg, and, indeed, FR can be less than 1200kg.

Most (UK) 737 commercial pilots, expecting to land close or below final reserve, work on an emergency call in your example 1) which should take away any aerodrome factors causing a g/a.

[Dogma]

Is it just me or is BOAC hard to follow? Perhaps he's just a hard act to follow :8

The unfortunate reality is that my colleges in Gatwick are planned to arrive with 1800 kgs which is the alternate fuel for Heathrow. Personally I would not be happy starting a diversion to John L from MAN with 1800 never mind Heathrow!

Sorry if this has been done to death, but at the moment I am seeing some pretty low figure in the tech log.

Dogs

[lederhosen]

I have to agree. The people contributing seemed to know what they were talking about, even if we hold differing views about the underlying issue. That is after all the purpose of good debate.

Yesterday dodging thunderstorms on four legs round Germany I was jolly glad to have taken a bit extra.

[Flagon]

'Scuse me for joining late here, but there is a lot of 'subjective' discussion here on fuel. Rainbow has told you all that the luxury of padding up the fuel 'just because' is no longer an option, and if you don't like it, well, you will need to think about changing careers as the way oil price is going, this is your future!

We need to know what "I am seeing some pretty low figure in the tech log." means - you need to state airfield, weather, runway availability and weight of your ?737? at landing plus taxy time to define "very low" - otherwise it is meaningless. Remember your company probably do not consider you to be 'very low' until you are at or below reserve if you are allowed to and are committed, and Boeing treat 906kg TOTAL as 'LOW' non-ETOPS.

Let's 'cut to the CHASE', Dogma, what is the lowest you have put in the log on shutdown, assuming, of course, you actually fly? As for 1800kg, that's enough for MAN-LGW, let alone a quick hop westerly MAN to westerly LPL!!! You could do a couple of circuits on arrival at LPL. Are you, perhaps, one of those F/Os who go all white and floppy when they see 2000kg on the gauges, or are you a hairy old Captain who NEVER shuts down "with less than 3000kg"? Have you ANY idea what other airlines like BA are 'putting in the Tech Log' on shutdown at LHR? How does that compare with your "very low". Shutting down with less than 1800kg in tanks is pretty common in my experience. If 1800kg MAN-LPL is bothering you, I think you need to talk to someone?

[lederhosen]

Flagon, why don't you post the average of the last ten fuel remaining entries on your 737 tech log. Obviously take out the tankering sectors, although that might provide interesting additional data for another survey. Then we can really start comparing across companies,anonymised of course. That is if you really fly the 737. Anyone else feel free to add their own experience. I have no problem with this becoming another thread by the way. Although given the average level of real experience behind the bluster I suspect no one will respond.

[Flagon]

post the average of the last ten fuel remaining entries on your 737 tech log. - Any "average" is meaningless without lots of other data. I cannot recall the figures, but a guess would be around 1750kg.

[lederhosen]

By the way if you believe your average is 1750 then you would be landing consistantly below our minimum diversion fuel (which is 1200 kg final reserve plus an OM stipulated minimum diversion of 600kg). I am sure others do it differently. If you really do that then there are indeed huge differences in the way companies operate.

[Flagon]

You asked for Tech log fuel entries. I make mine on stand, not on landing, and I reckon I might just burn more than 50kg taxying in.

[Rainboe]

Chaps, the point I am trying to make is that extra fuel is a 'comfort thing'. When that 'comfort thing' was bought at $15/barrel....fine. When that same 'comfort thing' comes in at $150/barrel, it becomes a luxury that is very expensive, and it behoves us to only make our employer pay that if it is absolutely necessary. What is happening is pilots are not reacting to the increase in cost of that 'comfort thing' by buying less- habits are not changing, and they have to. It does not mean planes are going to run out of fuel. We have had to go back over 30 years I believe to find an example in the western world, and that involved significant technical problems and a complete breakdown of CRM. Without the 'comfort thing', one must make the decision that will come later that little bit earlier. Because of the price of fuel, we must be a little bit sharper. To blindly say one is still going to carry around the same figures with the way costs have gone up is plain ignorant.

If you are flying around in Cbs, then who is going to complain if you have a good reason?

[lederhosen]

First of all I totally agree with Rainboe's point about taking too much fuel, in fact I think we should have been doing it much earlier than now.

I agree with Flagon's point that this is subjective which is why I suggested we compare some data. The average on shutdown for us seems to be around 2700. I am convinced we can reduce this, ideally to around 2200.

However I still find Flagon's figures improbable. Sure you use 14kg/min getting on stand. It makes 50 to 100 kg difference. Your flight plans are sampled by the boys from the Belgrano. If you are regularly arriving with 1750kg or less I suggest they are going to start asking questions about your flight planning software. Don't you ever get any shortcuts or save any fuel? That is after all the real target.

[Flagon]

The average on shutdown for us seems to be around 2700. I am convinced we can reduce this, ideally to around 2200. - meaningless!

Incidentally, I shut down a while back with 5250kg, non-tanking, single runway, CAVOK, no delay, 737NG, CMR 1750kg, and I needed all that fuel. What do you make of that? See what I mean?

I'm still waiting to hear what "very low" is for Dogma and why 'it' cannot get to LPL from MAN with 1800kg.

[Rainboe]

When I was on 747s, we used to usually end up with round about 11k which is just over an hour to dry tanks. This would equate to about 2.3 on an NG, which is usually about CMR + 500 Contingency. About right, just over an hour to dry tanks. Landing with CMR is fine, Contingency is available to be used. There seems to be great horror amongst younger pilots if you ever start dipping into it. Flying back from the Far East and unable to get above FL260 for many hours because of overflying traffic, you can see your Contingency disappearing. You then have to restructure your fuel reserves in whatever way you can, and even end up losing your alternate altogether. But the younger guys really don't understand how it all works- when you can disregard your alternate. When I took minimum fuel recently, one of them came up with this: 'but if we use more than taxi fuel to get airborne, we HAVE to divert, don't we?'. I have to confess I looked at him and wondered whether to put him right, but I thought 'I really can't be bothered!'

As for shutting down with average figures of 2.7, this would be too much in a European operation. One must think of carrying 500kgs too much every flight, and what this costs over a year, and compare it with the cost of the diversions over a year if it were not carried. I would suggest no contest as there would probably be none. That 500kg statistically mostly merely delays a diversion that would happen anyway, so the justification for carrying it is not there.

[Flagon]

Rainboe - for one so wise you have fallen into the same trap. How do you KNOW 2700kg is "too much"? As I have said before, without details of CMR/company policy/runway availabilty/weather factor etc we can not be sure - as in my 5250kg example. Was that "too much"? I'm sure you are right, however, but we must avoid this nebulous subjectivism on fuel carriage. It is essential we are OBJECTIVE on it, and statements like "Personally I would not be happy starting a diversion to John L from MAN with 1800 never mind Heathrow!" merely reinforce your observations on F/Os .. while it is always good to have a sensible input/query from a knowledgeable F/O, those sort of questions leave me gasping too.

[Rainboe]

Thankyou, but I am not wise! Aviation management is controlling your stupidity so nobody susses you out effectively! I can achieve that 90% of the time- as long as I get the impression most people are below that score, then I'm not too unhappy!
I think in a summer European or US high density airport environment, average arrival figures of 2.7, especially in summer, need urgent looking at. But there may be a good reason. The graph of arrival fuel amounts versus numbers of aircraft should be starting from zero and going up to a peak and down to zero again in a nice pretty sine-type wave. the idea is to keep the beginning of the wave to the right of the zero point (origin)-ie EVERY single arrival with some fuel! The question is how far to the right to have that curve start, and where the peak should be. If part of the reason for the high average arrival figure is because of tankering for economy reasons, that may explain why it is so high.

[Dogma]

I have had a number of PM's about the issue of arrival fuel into the UK particularly into London airports. Clearly the use of the Low Fuel checklist and committing with the very real potential of burning Final Reserve is not acceptable.

With a CMR of 1800, planning to arrive with 2400 is excellent airmanship and contributes directly to flight safety.

[BOAC]

You'll have no argument from me, Dogma, on carrying extra into London airports and that is, as I'm sure you know, just what we are all supposed to do. Of course it is illegal to PLAN to commit and I trust there is no airline doing that?

[lederhosen]

Well I think we are in what I would call violent agreement, Took minimum fuel yesterday arrived with 2400. On the way back my FO suggested we take a bit more than I had originally planned. I was happy to do so. Given reports on the radio this morning of snow plows clearing the aftermath from the storm overnight as it moved on, I think the extra 40kg or so we burnt doing this was good insurance.

Having run a few successful improvement projects in the past I am pretty familiar with people's initial reaction of trying to trash any data/methodology .. eventually common sense prevails.

[Flagon]

Dogma - You never told us why you could not make LPL with 1800kg or in which company you were seeing these VERY LOW figures or even what they were.

Do you have ANY idea what sometimes goes in the Tech Log in a medium twin at a 2-runway airfield. Often pilots do a fair bit of 'committing' which will put them fairly well below 2400kg.

Now, back to topic please. Anyone got any useful input on g/a's with low fuel? Never had to do one myself, so any experience welcome. Did you get a pump light or 2 on or did you manage to avoid that? Has anyone been down to 'LOW' fuel (NG non-ETOPS) - ie 906kg total - and still been flying?:eek:

[Rainboe]

Before Rainboe grabs you, never begin a sentance with 'But'.

But I don't mind chaps! But please cool it- the whole point of the discussion got lost sometime back!

[Dogma]

Copy that Rainboe

As stated, I have a number of PM's that I have received have expressed grave concerns about fuel planning with Low Fuel figures at destination arrival.

[john_tullamarine]

I am guilty of not keeping a close eye on this thread. Had a complaint about things getting a tad heated up .. not important who complained or to which posters the complaint related ..

Just to restate the ground rules for Tech Log ..

(a) any discussion is fine so long as it has at least a tenuous link with professional flying

(b) a reasonable level of politeness is required. That is not to say that we need to be namby pamby .. but the aim is to play the ball .. not the player.

(c) outright bad-mouthing is not acceptable at all

(d) revisiting subjects which have been aired before is more than acceptable as Tech Log acknowledges an educational role with the new folks always coming up through the ranks

With apologies to many, I have conducted a slash and burn operation on the thread to remove the odd comment and then endeavoured to tidy up other posts so the thing still flows ... inadequacies in so doing remain mine alone.

I accept that the occasional thread stirs up passions a bit .. and fuel is something near and dear to our hearts .. except for the sailplane colleagues who prefer a quieter life ... perhaps we can all take ten deep breaths and carry on the arguments in a more dignified manner ?

regards,

John T

[mnttech]

Just how accurate are the 737NG fuel qty indicators anyhow?
I know that each type of system has it's own pros and cons, but per the FAA (for those aircraft built under FAR 25)

§ 25.1553 Fuel quantity indicator.
If the unusable fuel supply for any tank exceeds one gallon, or five percent of the tank capacity, whichever is greater, a red arc must be marked on its indicator extending from the calibrated zero reading to the lowest reading obtainable in level flight.

Having flown the old probe system, I know that pitch and roll angles changed the readings. Also, there was the question of how long ago the system was calibrated.

[BOAC]

I have had a number of PM's about the issue of arrival fuel into the UK particularly into London airports. Clearly the use of the Low Fuel checklist and committing with the very real potential of burning Final Reserve is not acceptable - Great! Are you planning to do anything with these PMs? Are you presenting the case to the CAA, who will probably point at the AIC and (rightly) say 'at least 20mins extra is about 2400kg - what's the problem?'? This is a very old PPrune topic and one which has been pretty-well thrashed to death before. The answer is already in place and there should be NO 'planning' into LON with the fuels you offer. If you can get a change in CAA regulation of airlines we will all benefit from being able to carry that 'little bit extra' into busy airports, whereas at the moment the other thread suggests that 1800kg (and below) is an 'acceptable CMR' in the CAA's eyes (see post#22 and other thread). If you are intending to try to stop a/c 'committing' there will be big issues at big airways! Do you have issues with 'statistical contingency fuel' as used in BA?