Fuel Circles
 

I am sure many of the old and bold on here will have a view on this, and will probably disagree with me, as I know that some of you disapprove of the way I am taught ;) So this is not a question, more something that I thought would get the Ppruners in discussion; I have now got my head around the working out and use of Fuel Circles for nav planning well enough to start a discussion on their useage.

So, picture your triangular navex route drawn on map. For a trip from base to Duxford and back via Grafham Water I have planned six fuel circles at points just after an "event" to check the fuel levels and diversion fuel. We can fly the trip on minimum 75 litres of fuel adn this is what I planned for (if it were the normal "Club fill" of 60 litres we would be into minus fuel!)

The figures I have (from base back to base) are:
72 62 52 47 39 35
57 47 37 32 24 20

The black figure is the amount of fuel which I still have to use. The bottom red figure is the Diversion fuel including FOG (in the Grob's case minimum FOG 15L.

The way to work out ones red fuel is to work out how many litres you are going to use to get to your destination (or furthest point on the navex). IN this case we would use 15 litres to reach Duxford. Therefore, 15 is taken off the last black figure and there you have the difference (in this case 15). Then you work backwards and take 15 (or whatever the difference is) off your black fuel to get your red fuel at that check point along your route. It has the advantage of being there on your chart and not having to check lots of paperwork.

Personally I think its a great system...would be interested to hear if anyone else is taught/teaches/was taught this method, or it is, as I suspect, a very useful military system; and one which I am very pleased to use...despite the incoming which I suspect will appear......:rolleyes:

Fuel Circles

Aim: Navigate from A to B to C to A and not Run Out of Fuel

A'Ship: Fuel Awareness, LOOKOUT

Ah that brings back memories of Jet Provost Navigation Exercises and yes, it sound like fuel circles as approved by RAF Central Flying School when Pontious was a pilot and used by yours truely as both a student and as an instructor decades ago.

Black/top = planned fuel remaining.

Red/bottom figure = "Bingo", your minimum to continue the navex as planned.

Yep, standard RAF technique (except I think your first pair of figures are wrong). Really becomes useful on more complex navexs where you go off-piste or have unexpected injects and need to know where you stand with regards to recovering the plan.

Absolutely Torque, couldn't decipher my own handwriting!!!:O

So, as this system is so useful, I wonder why it is not standard PPL practice to teach it? Makes me glad i'm being taught by the RAF !!

Rather than doing fuel checks just after a turning point, when you're sorting out post-HAAT checks, or at a navigation check point, do them at a low activity point when you do a normal FREDAL check.

Sort the navigation first, do your fuel checks when things are quiet!

I have never been in the RAF (tried to join in 1973 but they were convinced I was KGB :) ) but I would guess that modern pilots don't navigate the way people used to, especially compared with the RAF as it was many years ago.

From what I hear and read, RAF missions were characterised by chronically tight fuel margins. If you fly a jet which has 1-2hrs of fuel, and you are navigating visually by dead reckoning, and you are supposed to do this in real weather, then you need a very robust system, comprising of highly selective recruitment, excellent pilot training, and strictly operated procedures. You also need the D&D 121.50 system which modern GA doesn't need.

GA is very different. Pilot training is very basic. Most "spamcan" missions are characterised by a poor knowledge of how much fuel is in the tanks at any point in the flight; this is dealt with by being very conservative on range and thus wasting much of the plane's capability. And there is a small % of GA which has accurate fuel metering, linked to the GPS flight plan, and they don't need these methods to plan diversions.

And what is the purpose of this 'great system'?

If you are going to plan fuel consuption down to the nearest 5 minutes it may have a purpose - except I have towonder what on earth you are flying that justifies such precision.

But bluntly it is completely pointless. To get the necessary levels of accuracy - you need an accurate fuel flow and totaliser - if you have that then all of the rest of it - - - is pointless.

Typically I have about 2.5 hours of fuel reserve - virtually guarantees me another county, countrt or continent........... depending where I am.

Whatever rings your bell, what do you genuinely think this adds any value?

Really???!!! I'm taught that if you're lost, D&D are there to help anyone who requires it and are only too happy too! 121.50 is a frequency which is etched on my brain!

If in general then, GA "doesn't need" the D&D; I have some questions. What sort of fuel loads do civilian schools teach students to carry? (OK, I know different aircraft have different weights, but generally speaking) How do they teach students to cope in an emergency where I would have no hesitation in using D&D?? I practice planning with a PLOG as well (to pass the skills test when it comes), but on the standard form, there is no where to put the fuel circle info which I put on the chart.

I was introduced to it a couple of years ago when I started flying ex-mil jets.
Bingo rings are good for keeping you on top of your fuel requirement, especially when you depart the original plan.
It is a very useful system to use when "eyes down" time needs to be kept to a minimum (ie. low level fast jet).

Modern GA aircraft with fuel totalisers and gps charts etc etc would have no requirement to use this system, but the technique is always good to know.

I would say that "Eyes down" time needs to be kept to a minimum whatever aircraft you are flying, be it FJ or Tiger Moth. I know that my instructor will want me to have my head in the chart as little as possible when navex-ing... aviate, navigate, communicate.

Also, with this manual system is all worked out, the pilot can keep a better personal idea of the fuel situation and does not need to rely on electronic gadgets which could go u/s at any time...

Agreed -these are ideal for when you need to divert and are an instant indication of where you can divert to, according to the amount of fuel left. Give me a fuel circle any day.

"Minimum" eyes down at 420 knots is different to "minimum" eyes down at 90 knots though. Take it from me.

Carry an alarm clock - set it at takeoff for whatever the minimum endurance is. Alarm goes off - find runway and land - sorted!

If you are lost, but nowadays that should not happen in the first place.

People who get lost do so almost always because they didn't use a GPS.

It is true that 121.50 is a great service but if a GA pilot needs it, then he has screwed up on multiple fronts. Or more likely just followed his WW1 PPL training ;)

Its the leather flying helmet, coat and gauntlets that really make the difference Peter ;)

Seriously though, I know nothing about GPS, but I thought it was for location and in case of need for diversion...not to tell the pilot what their fuel state is?? Don't get me wrong, I have nothing against a GPS, and I daresay i'll treat myself to one when qualified. Also the aircraft fuel gauge is good; and of course we all do our FEEL cx.... But fuel gauges and GPs systems can go wrong. It is then that you require a manual back up.

Sure you want a backup but with any backup system (not just in aviation) you have to ask yourself what the value of it is, relative to the primary system.

To take a silly example but one which illustrates the point: would you drive a Vauxhall Viva, and tow a Toyota behind it in case the Viva breaks down?

In flying, lots of things are inter-related and end up being only as good as the thing they are depending on.

Take the whole concept of MSA for example. This is utterly dependent upon accurate navigation. If you are unsure about position, MSA is out of the window. As many people know; most are dead, but some were very lucky.

Fuel reserves are dependent upon various things, all of which can be accurately known if you have the right equipment, but in the typical GA context they are not:

The fuel reserves firstly depend on how much you started off with. You had a chance to physically check that, so that's :ok: (well not always but there is one born every minute and some of them are bound to get a PPL :) ).

Once you get airborne, the fuel reserves depend on various things. Ground speed (not airspeed, which you should know well) is the key. Lateral nav is of course important if you want to get to the destination :) But along the route it is not too vital so long as you are going roughly in the right direction.

If you cannot find the destination then you have a potentially major problem. It could be anywhere.

Most cases of a pilot doing dead reckoning getting lost are ones where he "positively" identified a ground feature but got the wrong one, so he then flew quite a bit further before realising the c0ckup. Or he forgot to start (or stop) the stopwatch. The outcome of such an error is usually highly embarrassing... This is why a cunning choice of visually unambiguous waypoints is vital.

Once airborne, most GA pilots have no idea of the actual fuel state. The fuel gauges are invariably useless. The fuel burn is only taken from the POH, which was prepared about 30 years previously. The pilot has never been taught what the red lever does, and that its correct use can yield an extra 20-30% more MPG.

In GA, the way this is properly addressed is with a GPS, which gives you precise navigation both laterally and along the track (ground speed, time and distance to run to target) and an accurate fuel flowmeter which is initially loaded with the FOB (fuel on board) and which gives both the instantaneous flow rate and the fuel remaining. This data is fed to the GPS (this is panel mounted kit, not handheld) which is programmed with the route and thus knows the distance to run, the ground speed, and it will constantly recalculate the projected fuel at destination based on the current GS (which assumes that the wind etc doesn't change, but that is a reasonable assumption, and pilots doing long trips should be aware of the overall weather pattern anyway).

Here is an article which describes the typical system. It really is far removed from the stuff taught in the PPL, but is not expensive. It is probably also far removed from 1960s-1980s RAF practices, if a I have just read is anything to go by. I know this will draw ridicule from RAF people here, and I don't suppose the Russians had anything better at any given time, but I think it is a huge piece of good luck that the RAF rarely had to do this stuff for real. For example, IIRC, after the Falklands bombing it was realised that the fuel burn of the Vulcan, under the particular conditions of that flight, was several tens of percent worse than had been assumed for many years beforehand.

Not so. The Vulcan fuel burn at high weight was entirely in accordance with the Operating Data Manual. The problem was that some complete idiot decided to use training weight rule of thumb figures which were grossly inaccurate at high AUW - nobody had flown the Vulcan at high weight for years as the nuclear bomb weighed considerably less than 21 x 1000lb conventional bombs. Fortunately the AAR planners insisted on ODM calculations after the fool had made such a nonsense of the planning.....

Thanks for the correction Beagle. However my point was that these people were the very best around; the best selected, best trained, and far more current than anybody in GA.

Today, there is no need to do stuff like this. The equipment and methods exist to plan a flight and execute it accurately and predictably. And if the MPG does drop (e.g. a massive unexpected headwind) then you will be able to divert early.

So much of what we fly with and how we fly is still hanging on 1940s 1950s 1960s practices. I've just done the JAA IR conversion, on which about 90% of the time was spent doing NDB holds and approaches, which almost nobody does (using the ADF) nowadays. Translate that to a typical 55hr ME IR and multiply it by the # of FTO ATPL students and add up the cost... for exactly what purpose?

Gloves off!
 

An interesting thread with the GPS will solve all crowd in one corner and the ex-military in the other corner.

However the thread can only raise awareness of the appalling standard of fuel planning that I find in the flying clubs, keep this one up guys it might just get a few people thinking about the subject.

Agree with A&C re fuel planning. I was trained as an FI with fuel circles and that's what I teach my students as all the proprietrary plogs are woeful as fuel planners. Fill a PA28 and you don't need to bother about fuel planning in a UK context. However fill a Chipmunk 22 with 18 and you do.

Problem with using it in light aircraft is that you need an accurate enough fuel gauge - which basically means a sight tube. You'll get that in many microlights, and some vintage aeroplanes - but few spamcans.

Given that, in most light aeroplanes, where it's reasonable to do fuel planning on the basis of predicted performance (plus a bit of a safety margin of-course), I think that the method will work, but using time rather than fuel state.

G