Fuel reserves

[turboplanner]

Let me ask you this. How many of you would submit an incident report, if you landed having eaten into your 45 min reserve?Just read the RAA ops manual with regard to safety reporting, not a lot of guidance there!

I don't want to appear the teacher's pet, but I'd do it, more to beat myself up because my standards were slipping and I'd moved a perfectly good aircraft up to a higher potential risk zone.

 

It's also good insurance against prosecution by CASA who have a lot more to gain when their pilots learn lessons from their mistakes.

 

 

[kaz3g]

Let me ask you this. How many of you would submit an incident report, if you landed having eaten into your 45 min reserve?Just read the RAA ops manual with regard to safety reporting, not a lot of guidance there!

I experienced some engine running problems and a stronger headwind on a long flight in a remote area and ate into my reserves. The only alternate was the main road.

 

I was in constant contact with ATC at the time but I was so shaken by what happened I didn't even think about reporting it to authorities. I was totally preoccupied with discovering what had gone wrong after landing because it gave me a serious fright! A cracked spark plug insulator was the primary culprit.

 

It was one hell of a personal lesson that has stayed with me over the ensuing years. I shared it with others by telling the story in a couple of flying journals at the time and I suppose I should have written something for the crash comic but that publication seems to have suffered death by a thousand cuts anyway.

 

My next next big trip will be across to north-west WA from Alice Springs and there are a couple of very long hops for me with my current fuel capacity. I plan to buy a 40 litre flexible auxiliary fuel tank. This would become my reserve and allow me to plan flights of up to 375 NM using the full 120 litres in the tanks. These tanks aren't cheap (approx $1000) but they are designed for the job and are a much safer proposition than carrying a couple of jerry cans and hoping for somewhere suitable to set down and top up.

 

Kaz

 

 

[turboplanner]

I think that was understandable Kaz, wouldn't have been uppermost in your mind.

 

 

[facthunter]

The reserve is there for "unplanned? unforseen " circumstances. You cannot plan to use your reserves (or you do not have reserves).

 

How many of you know what the reliable useable fuel is? Will you get it all out if you need it? ( if you can't rely on it all then the whole notion is hypothetical). What are you relying on when you get to the 45 minutes? Gauges? (most of them are unreliable). IF you are over water or tiger country and with 45 mins fuel ( but not even sure of that) your attention will be increasing, and you should be looking for somewhere to get it on the ground. You should never get yourself into that situation, in normal circumstances. To have your engine stall with fuel exhaustion after landing is NOT clever at all. YOU were JUST LUCKY. Not good judgement.

 

This is not directed at Kaz It's a general statement written before I read that post. I don't think 45 minutes is a lot of fuel because it is not guaranteed to be there and you cannot measure it accurately and therefore cannot count on it. Perfect engines still need fuel to run on. I usually had about one and a half hours in the Citabria in which I mostly did fairly long trips. Long trips need to include a % of fuel burn too inless there are available diversions along the way. Nev

 

 

[turboplanner]

I notice you didn't answer the question......

 

 

[facthunter]

No , you're right . There are many different answers for different situations and it gets in to equi-time points and PNR's of various kinds. I'm looking initally at the purpose of reserves.

 

When I look at some of the possibilities that CASA suggest should be covered I think they are not quite in a world of reality. Perhaps they are considerations.

 

. When and IF you do run out of fuel it will be because YOU didn't have enough whatever your planning was, though they didn't suggest that fuel should be carried to cover the possibility of fuel leaking, which I have experienced a few times. so you can't cover everything.

 

It is certainly worthwhile to try to keep fuel to the engine, because it's a silly way for it to go quiet.

 

I'm a bit conservative so, On figures I reckon 10% flight time and arrive with one hour as well. You can replan/ recalculate in the air with this method. Cut the hour back depending on destination and how accurately you measure your fuel flow and quantities.. Nev

 

 

[Guernsey]

I'm glad I don't have my Tyro anymore, with a standard fuel tank I wouldn't be going anywhere.

 

Alan.

 

 

[turboplanner]

I'm glad I don't have my Tyro anymore, with a standard fuel tank I wouldn't be going anywhere.Alan.

How many flights at $6000.00 a flight did you do?

 

Most people never think that although they may take off successfully, they won't necessarily be able to ghat back on their own airfield. There was an example of a Cessna 172 unable to get back into Tyabb because fog rolled in after takeoff, Someone can screw up a landing and block the runway - a variety of reasons. So the questions, even when you are just going up for a few circuits are: "What is my alternate field?" and "how much fuel do I need to get there?"

 

 

[facthunter]

With a short field single runway destination it might be wise to carry an alternate in case the runway is obstructed by a disabled aircraft. This happens more often then you would think. Most of this is common sense but you have to be able to cover the requirements at test time. When I flew GA Initially we nearly always filled the fuel tanks. When you are operating commercially you may rarely fill the tanks. Nev

 

 

[motzartmerv]

Fuel Fuel Fuel!!!.. How much have I got, how much do i need, how quickly am I burning it...

 

We would want you to know pretty accuratly, how much fuel you have remaining. Guages are not accurate enough to bet your life on, so a combination of fuel burn rate over time, guages, known quantity at start up and for those lucky enough, a fuel flow meter. Although this can lead to trouble aswel if your tanks are leaking. Which happens. A common cause is a fuel drain cock left partially open after a drain, the lower air pressure outside the tank during flight can squeeze the fuel out. This wont show up on your burn over time calcs, or your fuel flow meter, but will show up on the guages.

 

45 mins fixed reserve is a bare minimum in my books. For ANY flight. Even a quick test flight or a couple of ccts. Like tubz said, you never know when you may have to go elsewhere. The general rule on variable reserve is 1.15 % of flight fuel. But, a much better plan, do a MTOW check and take as much fuel as you can carry. Only time you have too much is when your on fire.:)

 

 

[kaz3g]

I think that was understandable Kaz, wouldn't have been uppermost in your mind.

It was 252 NM from YTNK to YBAS and I started with full fuel. I plan 100 knots TAS at 34 LPH. My tanks hold 120 litres and I plan 3 hrs 30 minutes until the noise stops. So I had a tad under 1 hr reserve in nil wind. The forecast variable became a gentle southerly of around 10 knots making my revised estimated flight time 168 minutes instead of 150 minutes so I still had my fixed reserve in theory.

 

There are really no sensible alternates along the VFR corridor until you get to Bond Springs but Auster fuel gauges are not renowned for either readability or accuracy --- and the belly tank doesn't have a gauge at all.

 

The maintenance guys ground ran it for 23 minutes on the tachometer. I warmed it up, say 10 minutes, and taxied to the bowser and it stopped all by itself.

 

Because it was running roughly, I had kept it up around 2500 rpm. I also found it was a little better with the mixture rich. My fuel consumption climbed accordingly but I was under pressure and was only thinking about an unplanned landing, not my fuel consumption...after all, I started the flight with plenty, didn't I?

 

Going into Alice, my thoughts were all concentrated on a possible engine stoppage, but for another reason. The tower cleared me with an extra thousand feet and I knew I could glide all the way in as I crossed above the town but I had been stressing for more than an hour and had developed a sort of tunnel view of things. I was so focused on what the engine was doing, where I would put down if the fan stopped, how far I had to run, and what clearances I needed, I stopped thinking about remaining fuel altogether.

 

A big lesson, indeed!

 

Kaz

 

 

[poteroo]

Let me ask you this. How many of you would submit an incident report, if you landed having eaten into your 45 min reserve?Just read the RAA ops manual with regard to safety reporting, not a lot of guidance there!

I've picked your post Howard, because it really asks the big question. The answer is NO - because this little rabbit learns from his mistakes without asking Big Brother to intervene. If you haven't worked out what caused your miscalculation - ask your CP or CFI.

 

In any case, let's toughen up a little here. Everyone is sooking on about the regulations and remaining compliant with them. What is really important is not having a fuel crisis, and to do this, you take as much fuel as you can uplift, and use it wisely.

 

happy days,

 

 

[turboplanner]

You're assuming everyone knows what an incident report is, and everyone knows how to calculate fuel burn in climb, cruise and descent and the influence of density height etc.

 

Without the calculation knowledge, not having a fuel crisis becomes a matter of luck.

 

 

[motzartmerv]

In any case, let's toughen up a little here. Everyone is sooking on about the regulations and remaining compliant with them. What is really important is not having a fuel crisis,

happy days,

Yes, and a good place to start is the reg's. Ask your CP or CFI where you went wrong? The first thing he would do is point you to the regs, providing the little rabbit survives the "mistake" and is around to learn from it.

 

Call it sooking if you please, but the regs are there for a good reason, and are a good place to start when your talking about this sort of thing.

 

 

[Wayne T Mathews]

Having spent years managing the fuel on flights going backwards and forwards over the longest stretch of "nowhere to land" in the world (USA West coast - Hawaii, >2,000nm), I'm going to go out on a limb here. You don't have to be a rocket scientist to fly our aircraft. But you do need to be aware of possible problems, and plan to cover them accordingly. The broadbrush descriptive titles we're using in this case are; airmanship and risk management. And we do it all the time.

 

 

Now, knowing how to calculate fuel burn in climb, cruise and descent and the influence of density height etc.

 

is important to people flying big jets over big distances. But it's not so important to us down at the altitudes we fly at. For practical purposes, we need to know how much fuel our engine is burning on average per hour. We need to know how far we have to go. And we need to know what ground speed to expect. With that infomation we can calculate how much fuel we expect to burn. Then we look at "do we need an alternate?" If the answer is yes, then calculate the fuel required for that. When you've got those numbers, add 45 minutes of fuel, and you've got what you need to plan the flight. The next thing is, how much fuel is in the tanks, is it enough, and will the aircraft lift it?

 

In the big jets, carrying extra fuel is a No-No. Lifting 7,000kg of extra fuel (10,000 ltrs as an example and using round figures) up to 35,000 feet takes a lot of energy (read $$$). So if they don't need it, the big boys won't take it. But for us, taking an extra 10 ltrs may well mean 30 minutes of extra noise, which gives us warm and fuzzy feelings, and the energy expended lifting that extra 7kg to say 5,000 feet, is minimal. So again, being practical, let me repeat what Poteroo had to say, "... take as much fuel as you can uplift, and use it wisely."

 

 

Honestly folks, it's not rocket science.... Calculate how much fuel you need for the planned leg. Add the amount of fuel you need to get to any alternate you're carrying. Add 45 minutes of fuel to the above, and you have the minimum fuel you're going to take-off with. Anything more than that is cotton candy... so take it if you can.

 

 

 

[turboplanner]

Honestly folks, it's not rocket science.... Calculate how much fuel you need for the planned leg. Add the amount of fuel you need to get to any alternate you're carrying. Add 45 minutes of fuel to the above, and you have the minimum fuel you're going to take-off with. Anything more than that is cotton candy... so take it if you can.

So does anyone here do this?

 

 

[Wayne T Mathews]

So does anyone here do this?

Methinks "So does anyone here not do this?" would be a more relevant question...

 

 

[facthunter]

Perhaps, if you put "as a minimum".?

 

Long flights have the potential to use up the reserves, IF something is different from the facts you planned the flight on. You could have greater headwinds higher fuel consumption , lower TAS than expected etc. IF you can monitor your fuel quantity very accurately, you might work to these minimums.

 

Frankly With a U/L or more basic GA plane I have never operated to just 45 minutes fixed reserve. except on a local or short ferry flight.

 

On reasonably long flights (say,3 hours+) you could easily eat into your reserve and technically when your burn to complete the trip leaves you with less than the planned minimum reserve, you would be legally required to divert to a nearer (air time) aerodrome. Once you become aware that your minimum reserve is not going to be there, and another safe and legal course of action is available, you must take the other course of action. IF you cannot go anywhere else then you do what you have to do with the remaining fuel, but make sure that your decisions are sound and defensible and preserve life before property. Try to never get yourself into this position, in the first place. Monitor your fuel use against planned constantly during the flight. Having an engine fail due to fuel exhaustion, on final over a heavily built-up area is not the best outcome at all Nev

 

 

[Wayne T Mathews]

Call it sooking if you please, but the regs are there for a good reason, and are a good place to start when your talking about this sort of thing.

Too true Motz: "the regs are there for a good reason, and are a good place to start when your talking about this sort of thing."

 

But let's not get all focussed on and bogged down by "the regs". They were after all, written by men (admittedly, quite often in blood), so they're not perfect... I like to consider the advice my mentor once gave me, "The book was written for the guidance of wise men, and the blind obedience of fools." ... Having said that, experience has definitely taught me, "the regs are there for a good reason, and are a good place to start when you're talking about this sort of thing."

 

 

 

[Wayne T Mathews]

Perhaps, if you put "as a minimum".?

Yep, definitely as a minimum.

 

There are a zillion reasons why our plan can need modification once we're airborne. And it's for those reasons we monitor our flight's progress, checking to see we're still travelling to plan. And if/when we find we're not, we need to amend the plan, one way or another, to keep us within known acceptable minimums. As I said, it's not rocket science...

 

 

[turboplanner]

Methinks "So does anyone here not do this?" would be a more relevant question...

I think you have your answer by the deafening silence on this thread; if it was about how to buy a cheaper GPS or similar the thread would be filled with posts.

 

 

[Wayne T Mathews]

I think you have your answer by the deafening silence on this thread; if it was about how to buy a cheaper GPS or similar the thread would be filled with posts.

You could be right Turbz. But to be fair, it is a subject that could leave one's butt and scrotum hanging uncovered in the breeze.

 

 

[turboplanner]

Since an increasing number of people are using RA aircraft for cross country flights, I think the five or so nights doing the climb cruise descent exercise, is not only an enjoyable, empowering experience, but could save some butts from gravel rash.

 

 

[facthunter]

I am afraid it is an area which appears to be under undertood. The RAAus put out a lot of stuff about fuelling and not running out of..... Maybe it is a cultural thing. I have heard of a couple of pilots who have done it while doing solo circuits and others have done it while in the vicinityof aerodromes.

 

Fuel is the life force of your aeroplane (unless it is a glider) On most aviation courses Fuel Management requires a mark of 100% to pass. ( Same as with weight and balance).

 

You can go into it And flight planning to a complex extent but that is possibly not required here, and now, but a clear understanding of the basics by everybody IS.

 

Practically , WHO has checked their plane to see how much fuel is unuseable, and just how much the tanks hold. Have reliable fuel flow figures been established and noted recently? (They can change). If part full fuel loads are used how accurate is the measurement? Do the dip sticks give accurate readings? How level has the plane to be to cause a significant error on dipsticks and full quantities.

 

Now I know that this may seem to be a bit off the discussion of reserves, But in the context of undertanding the situation where reserves are likely to be considered fully, the other factors must come into the discussion. Nev

 

 

[turboplanner]

Good basis to start FH.

 

USEABLE FUEL

 

In designing and constructing a fuel tank, rarely does the designer get an even break. In a perfect world the bottom of the tank would be a dome, or tapered from all sides, but space cost or other components usually decide that it's tubular, has a V bottom or the bottom is recessed to provide clearance for other components.

 

In a perfect world, the suction/drain point would be at the very end of a tapered or rounded bottom, but practically by the time you allow for weldable metal, weld width, spigot width, thread width and pipe thickness, you'ved moved some distance from the end of the tank.

 

If you could tilt the tank, the unuseable volume would be small, but even that gets compromised, so even in an optimised design a surprising about of fuel remains trapped in the tank.

 

In the case of aluminium round or square truck tanks, trapped fuel averages 5%, and similar shaped aircraft tanks will lose a similar percentage.

 

If you have two tanks, double the fuel is trapped

 

This might come as a surprise to you, but some aircraft companies don't tell you about this.

 

For example, the specification sheet may quote 140 litres tank size, fuel furn 15 litres per hour, and cruise speed 95 kts.

 

So you might thing your range is 140/15*95 = 886 Nm

 

But if the useable fuel is only 95% of this the calculation is

 

140 less 5% = 133/15*95 = 842, or 44 Nm less. (81 kilometres)

 

If you are being belted around by headwinds on a trip, an error of calculating with total fuel rather than Useable fuel can take away a few options, or catch you by surprise.

 

The Jabiru J170 operators manual is great - quoting Useable fuel of 135 litres in two wing tanks.

 

How you make sure you've got that 135 litres of fuel in the tanks is another story for another day.

 

If you don't have a friendly manufacturer who has already calculated Useable fuel for you, you can do this:

 

1. Jack the aircraft in cruise flight position

 

2. Fit a temporary tap to the suction point of the empty tank.

 

3. Fill the tank using a calibrated jug and measure how many millilitres per jug.

 

Note the amount of fuel used to fill the tank to a repeatable, practical marker level ("Remembering" is not noting - this will affect every trip you do)

 

4. Empty the tank into the jug and measure by millilitres.

 

5. Add up the jug totals you could get out with the aircraft in flying condition and that's your useable fuel.

 

You only have to do that job once, then you can flight plan accurately every time.