PA28 Fuel management
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IO540: I use commercial reserves - even when flying a PA28. I.e, 5% contingency fuel, plus enough for a go-around, 30 minutes "holding" fuel, and a diversion to a suitably planned alternate. A bit like an airliner's Computed Minimum Reserve if you will. It usually ends up at around 7.5-8 US Gallons (depending if it's a Cadet, a Warrior or an Archer) leaving about 4 hours' endurance (even without leaning). That still allows to fly beyond Le Touquet.
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Originally Posted by G-EMMA
OK the 20 billion dollar question, why doesn't a PA-28 have the option to select both? Was it just cost or does anyone know if there is a good reason for it?
I don't know about the PA28, but the PA25 (pawnee) comes in a couple configurations. One is a single cowl tank, the other is two wing tanks. Our pawnee with the wing tanks is plumbed to take fuel from both tanks, with no selector. There is a fuel shutoff which is downstream of the tanks. We typically fly for 1.5 hours, and the fuel is never balanced between the tanks. Sometimes the left tank will be very low and the right tank will be nearly full. What bugs me about that is what happens if one tank runs out first? Seems like the fuel pump would rather pull air than fuel, as it is much less work. This is a lot different than a high wing, where gravity wants to push the heavy fuel downhill, and leave the light air in the tank. But when I fly a PA28 I can ensure that I don't run a tank out of gas, by managing the fuel selector.
-- IFMU
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There are two different questions being asked here (and a third not being addressed)
1 - How do you make sure you do not accidentally run a tank dry on a longish flight in an aircraft that feeds from only one tank at a time.
- Lots of good answers in the thread
2 - How do you Actually know how much fuel is left at any time
- Fewer good answers (IO's definitely, FougaMagister seems to fly the same or similar aircraft multiple times so uses a close approximation of IO's)
On many aircraft, fuel burn is highly dependant on leaning technique which is one of the reasons pilots are often taught not to trust the book numbers. FMS commercial technique applied by a less experienced pilot without accurate leaning could easily wind up as a glider on a flight that actually had to execute the diversion
3 - (The one not asked yet) How do you operate a maximum range flight. Ie. How much usable fuel is really in your tanks (more important for bladder than integral tanks) and what fuel configuration do you want on landing.
Deakin has an article on Pelican's perch (AvWeb) where he advocates running each tank dry (on separate flights!) so on refilling he can establish exactly how much useable fuel there was, He then advocates, if you have to stretch every drop out (i.e. an emergency) running one of the tanks dry so you have all of your fuel in one tank on landing and minimise the risk of un-porting or being on the slightly less full tank and accidentally running it dry in the pattern. Finally of course as usual, he recommends a full engine analysis and a known calibrated fuel totalizer. And finally, there is an implied caution to make sure you have plenty of enroute diversion options
1 - How do you make sure you do not accidentally run a tank dry on a longish flight in an aircraft that feeds from only one tank at a time.
- Lots of good answers in the thread
2 - How do you Actually know how much fuel is left at any time
- Fewer good answers (IO's definitely, FougaMagister seems to fly the same or similar aircraft multiple times so uses a close approximation of IO's)
On many aircraft, fuel burn is highly dependant on leaning technique which is one of the reasons pilots are often taught not to trust the book numbers. FMS commercial technique applied by a less experienced pilot without accurate leaning could easily wind up as a glider on a flight that actually had to execute the diversion
3 - (The one not asked yet) How do you operate a maximum range flight. Ie. How much usable fuel is really in your tanks (more important for bladder than integral tanks) and what fuel configuration do you want on landing.
Deakin has an article on Pelican's perch (AvWeb) where he advocates running each tank dry (on separate flights!) so on refilling he can establish exactly how much useable fuel there was, He then advocates, if you have to stretch every drop out (i.e. an emergency) running one of the tanks dry so you have all of your fuel in one tank on landing and minimise the risk of un-porting or being on the slightly less full tank and accidentally running it dry in the pattern. Finally of course as usual, he recommends a full engine analysis and a known calibrated fuel totalizer. And finally, there is an implied caution to make sure you have plenty of enroute diversion options
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IO540: I use commercial reserves - even when flying a PA28. I.e, 5% contingency fuel, plus enough for a go-around, 30 minutes "holding" fuel, and a diversion to a suitably planned alternate. A bit like an airliner's Computed Minimum Reserve if you will. It usually ends up at around 7.5-8 US Gallons (depending if it's a Cadet, a Warrior or an Archer) leaving about 4 hours' endurance (even without leaning). That still allows to fly beyond Le Touquet.
Incidentally, the fuel flow difference between a) full-rich and b) leaned to peak EGT, is about 30%..... a LOT. Most UK PPL training is done full-rich, which robs the plane of a large chunk of its useful range for going places.
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Know your aircraft !
I agree with almost all that IO540 has to say on the subject, however if you know the aircraft well you don't have to have any more than an EGT indicator to get accurate fuel flow numbers.
On both the Robins that I have owned (same engine as the PA28) I could get the fuel flow numbers to the nearest litre, I fly (by UK GA standards) long flights direct to northern Spain and the far south of France from Oxfordshire and have never had a fuel management problem.
To achive this I make sure that the power and mixture are accuratly set and at the end of a flight check that the fuel uplift matches the plog fuel burn (to monitor engine performance).
As for fuel planning I use the basic commercial reserves as outlined above however on the longer flights I use the en-route alternate system. this cuts the contingency fuel down to 5% overhead the destination airfield and gives about 30 Nm more range but requires carefull fuel monitering
at each waypoint along the route.
The biggest problem with the average PPL holder is poor education when it comes to fuel management, most clubs treat the mixture lever as an "on-off switch". I have found when doing recency checks for a local flying club that most pilots don't even know how to set 75 or 60% power and this is essental for accurate fuel flow at these are the numbers in the flight manual with the performance graphs.
Can someone please tell me how most new PPL holders have got a licence and never used the mixture lever correctly?
On both the Robins that I have owned (same engine as the PA28) I could get the fuel flow numbers to the nearest litre, I fly (by UK GA standards) long flights direct to northern Spain and the far south of France from Oxfordshire and have never had a fuel management problem.
To achive this I make sure that the power and mixture are accuratly set and at the end of a flight check that the fuel uplift matches the plog fuel burn (to monitor engine performance).
As for fuel planning I use the basic commercial reserves as outlined above however on the longer flights I use the en-route alternate system. this cuts the contingency fuel down to 5% overhead the destination airfield and gives about 30 Nm more range but requires carefull fuel monitering
at each waypoint along the route.
The biggest problem with the average PPL holder is poor education when it comes to fuel management, most clubs treat the mixture lever as an "on-off switch". I have found when doing recency checks for a local flying club that most pilots don't even know how to set 75 or 60% power and this is essental for accurate fuel flow at these are the numbers in the flight manual with the performance graphs.
Can someone please tell me how most new PPL holders have got a licence and never used the mixture lever correctly?
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Can someone please tell me how most new PPL holders have got a licence and never used the mixture lever correctly?
My tip is always leave one tank with 15 minutes more fuel in it because thats the tank you want to run on in a fuel emergency landing
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Well the problem is knowing what's in the tanks and what comes out.
In a GA context, there really are three scenarios:
a) fly your own a/c, ideally equipped with a good fuel-flow meter. This is the ideal situation, as you know your machine AND have the instrumentation to check what it is actually up to. Great, seems to be IO's circumstance.
b) fly one or two club a/c regularly, therefore get to know them well and develop empirical data. Some may even have a flow meter.... mostly (with exceptions) my situation.
c) fly a wide variety of spamcans w/o flow meters. Now we're down to guesswork or book numbers with all the associated problems. This, alas, probably describes a good portion of GA flying
My personal approach is to err on the side of caution and I usually adopt an approach similar to Fouga's - also because I seem to be in a similar situation, as mm-flynn points out.
Leaves us with the question on how to plan a maximum-range flight. My - short - answer would be: don't with an unfamiliar a/c unless it is equipped with a good (and working) fuel flow meter. I've had to do this a number of times, and my approach is to do a couple of short(ish) hops and see what really happens. Most of the time you can start a long journey by doing a few short legs first, figure out what's what and then go about the long-haul (well, in GA terms) planning.
Now seriously drifted from PA28 fuel management
In a GA context, there really are three scenarios:
a) fly your own a/c, ideally equipped with a good fuel-flow meter. This is the ideal situation, as you know your machine AND have the instrumentation to check what it is actually up to. Great, seems to be IO's circumstance.
b) fly one or two club a/c regularly, therefore get to know them well and develop empirical data. Some may even have a flow meter.... mostly (with exceptions) my situation.
c) fly a wide variety of spamcans w/o flow meters. Now we're down to guesswork or book numbers with all the associated problems. This, alas, probably describes a good portion of GA flying
My personal approach is to err on the side of caution and I usually adopt an approach similar to Fouga's - also because I seem to be in a similar situation, as mm-flynn points out.
Leaves us with the question on how to plan a maximum-range flight. My - short - answer would be: don't with an unfamiliar a/c unless it is equipped with a good (and working) fuel flow meter. I've had to do this a number of times, and my approach is to do a couple of short(ish) hops and see what really happens. Most of the time you can start a long journey by doing a few short legs first, figure out what's what and then go about the long-haul (well, in GA terms) planning.
Now seriously drifted from PA28 fuel management
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I think that's exactly it: you cannot do a max-range flight with an unknown aircraft, working on POH data.
The two test flights I referred to earlier can be easily done in the context of two trips somewhere.
The two test flights I referred to earlier can be easily done in the context of two trips somewhere.
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I agree that fuel management is something that woofully inadequately taught on the PPL, in fact when I look back on mine I dont think they spent more than 5 mins on the subject! It was only when I really started flying regulary in the club/group atmosphere you start to pick up on things and supplement your PPL - as keeps getting said "Its a licence to learn"
I like to keep it simple so hence the clock face approach, I think doing it every FREDA check is a bit excessive but it works for you then stick with it. You also dont need a fuel flow meter, just look at how many litres they put in on your return and you can easily work out your gallons/hr, again keeping it simple, not 100% accurate but good enough.
Leaning again is something I really got my teeth into post PPL and I think something which wasnt stressed enough on my PPL. A mate (from our group) and myself did an experiment in our PA28, 2 flights upto about 4500, first without leaning and second with. We got from 11 USG/hr down to 7.8 USG/hr, so quite a saving on a long trip and also quite a range improvement (hate the phrase "mission capability" - makes it sounds like I am going to bomb someone ). These are approx figures as we worked it out from the uplift of fuel back on thre ground, but as pay a dry (not wet) rate for the aircraft its all money that stays in our pockets not Mr Browns.
My 2p worth.
J.
I like to keep it simple so hence the clock face approach, I think doing it every FREDA check is a bit excessive but it works for you then stick with it. You also dont need a fuel flow meter, just look at how many litres they put in on your return and you can easily work out your gallons/hr, again keeping it simple, not 100% accurate but good enough.
Leaning again is something I really got my teeth into post PPL and I think something which wasnt stressed enough on my PPL. A mate (from our group) and myself did an experiment in our PA28, 2 flights upto about 4500, first without leaning and second with. We got from 11 USG/hr down to 7.8 USG/hr, so quite a saving on a long trip and also quite a range improvement (hate the phrase "mission capability" - makes it sounds like I am going to bomb someone
). These are approx figures as we worked it out from the uplift of fuel back on thre ground, but as pay a dry (not wet) rate for the aircraft its all money that stays in our pockets not Mr Browns.My 2p worth.
J.
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OK the 20 billion dollar question, why doesn't a PA-28 have the option to select both? Was it just cost or does anyone know if there is a good reason for it?
It's hard to explain but try this...
Get 2 cups, each with a straw. Fill one cup with water and leave the other empty. Now put both straws in your mouth and suck. You should find that it's almost impossible to draw water from the cup that is full. Fill them both, and you have no problems!
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Two fuel systems provides additional safety, the fuel in one tank could be contaminated,( I have known private owners fill one side with avgas and the other side with automobile fuel) there could be a blockage or leak in part of the system in that side. Having the ability to run on the other system allows the engine to continue running in these circumstances.
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Leaning makes a difference at any altitude. I normally fly an Arrow III, and at 1500 feet, 23 ins/2300RPM/fully rich, the flow gauge indicates 14.5gph. if I lean it to just rich of peak, it drops to about 11 gph. The cruising speed is slightly higher when leaned (the actual speed depends on loading).
Fuel management - I use the "clockface/half hourly" method.
The only reliable fuel gauge is to look into the tanks before takeoff. I work on "full" and "tabs". I also stick to the same "fuel reserves" as mentioned above by FougaMagister. If it's below 1½ hours, I should have landed already.
Over several years, I find that the fuel burn is very consistent. Leaned to an indicated 11 gph, it does indeed burn 11 gph. That's not to say yours will, but it works for me.
Fuel management - I use the "clockface/half hourly" method.
The only reliable fuel gauge is to look into the tanks before takeoff. I work on "full" and "tabs". I also stick to the same "fuel reserves" as mentioned above by FougaMagister. If it's below 1½ hours, I should have landed already.
Over several years, I find that the fuel burn is very consistent. Leaned to an indicated 11 gph, it does indeed burn 11 gph. That's not to say yours will, but it works for me.
Similarly to '540, I check the fuel consumption in each of the aircraft I fly - and I fly in general aviation for a living.
The aircraft I fly have multiple tanks (up to 6) but my method is similar to '540s: On a typical trip that allows full tanks - and there's always one, soon enough - I do from start to top of climb on one tank. After setting cruise power & leaning I change to the other tank and note the time interval since start.
I then burn only from that tank until I have to reduce power during the descent & approach. Prior to reducing power I change back to the main tank and note the time interval.
After shutdown I note the interval again & have the tanks filled. The fuel consumption from the cruise tank gives me cruise power fuel flow. Using that FF for the intervals where fuel was consumed for the departure & arrival gives me the figure that would have been burnt if that entire period was in the cruise. The difference between that amount and the amount that was consumed from the departure & arrival tank gives me the additional departure & arrival fuel for required for a typical flight.
Next time I need to plan fuel consumption I need only to plan the entire leg at the measured cruise fuel flow and add the calculated departure & approach allowance.
Until I can do that for an aircraft I plan fuel consumption conservatively. In all cases I always check fuel uplift against time flown to get a block fuel flow for that aircraft. Periodically I revisit the extended method to check accuracy.
When I was flying air ambulance between the Shetlands & Scotland I would not have been able to do some trips without an accurate fuel consumption. The availability of alternates would be so limiting that a rough & ready fuel rate wasn't sufficient.
The aircraft I fly have multiple tanks (up to 6) but my method is similar to '540s: On a typical trip that allows full tanks - and there's always one, soon enough - I do from start to top of climb on one tank. After setting cruise power & leaning I change to the other tank and note the time interval since start.
I then burn only from that tank until I have to reduce power during the descent & approach. Prior to reducing power I change back to the main tank and note the time interval.
After shutdown I note the interval again & have the tanks filled. The fuel consumption from the cruise tank gives me cruise power fuel flow. Using that FF for the intervals where fuel was consumed for the departure & arrival gives me the figure that would have been burnt if that entire period was in the cruise. The difference between that amount and the amount that was consumed from the departure & arrival tank gives me the additional departure & arrival fuel for required for a typical flight.
Next time I need to plan fuel consumption I need only to plan the entire leg at the measured cruise fuel flow and add the calculated departure & approach allowance.
Until I can do that for an aircraft I plan fuel consumption conservatively. In all cases I always check fuel uplift against time flown to get a block fuel flow for that aircraft. Periodically I revisit the extended method to check accuracy.
When I was flying air ambulance between the Shetlands & Scotland I would not have been able to do some trips without an accurate fuel consumption. The availability of alternates would be so limiting that a rough & ready fuel rate wasn't sufficient.
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A lot of the above cant help you if you have a fuel leak in flight, gauges are the only real means of detection until it all goes quiet. Some have mentioned that the gauges on some aircraft are very inaccurate but what they really mean is that they tolerate flying unservicable aircraft.
Being a professional pilot dosnt make for better fuel planning(as suggested) all the low fuel emergencies I can remember involve professional pilots.
Being a professional pilot dosnt make for better fuel planning(as suggested) all the low fuel emergencies I can remember involve professional pilots.
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A lot of the above cant help you if you have a fuel leak in flight, gauges are the only real means of detection until it all goes quiet. Some have mentioned that the gauges on some aircraft are very inaccurate but what they really mean is that they tolerate flying unservicable aircraft.
A renter can't walk into a school and demand they rip out the crappy 30 year old gauges and replace them with new ones.
Duff fuel gauges are an integral part of general aviation - tolerated along with all the other crap we put up with.
The only "escape" is to rent from one of the very few schools that have modern fleets, or scrape up enough money to buy something decent like a TB20GT with a 28V system whose capacitive fuel gauges are accurate to a few percent. But the TB20 will probably have a flow totaliser anyway.
Of all the planes I have ever rented, not one had gauges usable to the extent of being worth reading for any fuel management purpose. This includes PA38, various PA28s, C150, C152. I have never trained in any plane whose fuel gauges were useful.
That's why one has to either play very conservatively (starting from a physical check) or establish the fuel flow experimentally and then basically work on timing the flight.
Being a professional pilot dosnt make for better fuel planning(as suggested) all the low fuel emergencies I can remember involve professional pilots.
But ultimately you are only as accurate as your equipment, and an awful lot of "professional" flying, at the piston end of things, is done in old wreckage, which is just the same as the wreckage used for training, only bigger and with more engines. The pilots of the ancient clapped out Trislanders for example have no better idea how much fuel they really have than a GA renter.
Depends on the rules of the country. Under FAR, yes. In Oz there must be a fuel guage calibration card that gives the correct** quantity for the gauges divisions.
Even so, most GA gauges measure [i]volume[/] but fuel consumption is by weight. That in itself affects how accurate the gauges can be to determine endurance.
As for the accuracy of a fuel gauge, the certification requirements aren't that high a hurdle to jump. What might seem rather poor can still be within requirements without necessarily being faulty.
**But then ground attitude doesn't have to equate to flight attitude. Oops, another contributor to fuzzy accuracy.
Even so, most GA gauges measure [i]volume[/] but fuel consumption is by weight. That in itself affects how accurate the gauges can be to determine endurance.
As for the accuracy of a fuel gauge, the certification requirements aren't that high a hurdle to jump. What might seem rather poor can still be within requirements without necessarily being faulty.
**But then ground attitude doesn't have to equate to flight attitude. Oops, another contributor to fuzzy accuracy.