Fuel planning

airbornejohnny

airbornejohnny

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I had a bit of a debate in my CFI ground class (141 school) where we were “teaching” planning a vfr xc flight for an up and coming student pilot. I applied into the “lesson” my personal smudge factor of a slightly higher fuel burn than the poh calls for which I’ve been using since day one (since I don’t want to run out of fuel). While my classmates all agree with my approach, our teacher pretty well beat the thought of it up since the poh numbers are what the manufacturer intends pilots to use. I still stand by my opinion, but would like the thoughts of others in here.
 
I plan for one gallon over what the POH says for fuel and one hour instead of the thirty minutes required after reaching the destination. Nothing wrong with flying with the minimums stated in the POH but there is also nothing wrong with using your personal safety limits either. However, for testing purposes in the classroom, I'd go with the instructor's recommendations.
 
totally agree with you. nominal burn for the Skycatcher is 6-gph. when planning my trip I would usually round up. for example...POH says to assume .6 gal for engine start, taxi and TO. I'd round that to 1-gal. if the XC was say 2.7 hours or 16.2-gal I'd round that to 17. instead of a 30-min reserve I planned a 1-hr reserve. my CFI taught me that and I've used it ever since. if that means I have to land midway to refuel or refuel for the return trip well, that's ok.
 
I do that. The Comanche burns 14 gph in cruise. I just round that to 15 for easy math. 90 gallons = 6 hours. I don't plan flights over 5 hours, for personal comfort more so than fuel.
 
In my practical - I used the more conservative approach as people are suggesting here. Examiner was very happy with that. I also plan at 10gph in my Archer, when it can easily cruise at a much lower rate.

Having said all that, not worth an argument with the instructor and it's unlikely you'll ever have an XC that outflys your fuel (or your bladder) during time in school. Might be best to let this one slip by in class and do what you're comfortable with in the real world.
 
I flight plan for book cruise fuel burn properly leaned, and add 1 gal total for taxi and takeoff, plus 1 additional gallon total for climb to altitude (based on estimated additional fuel burn full rich for a 15-20 minute climb). There is maybe a little cushion in this planning because the descent phase will be less than book cruise consumption. Using this method I can typically predict my fuel consumption within +/- 1 gallon for a typical trip. If you check your actual vs. planned fuel burn, you can validate your approach to fuel planning.

VFR or IFR I insist on a 1 hour reserve, which usually means bingo time is about 3+20 to 3+30 on full tanks depending on cruise speed. If your time to destination exceeds your bingo time you divert for fuel. No cheating. (Just 5 more minutes...just 5 additional minutes...OK 5 minutes more...maybe the headwind will abate a little...this will eventually get you in trouble.) Planning 3 hour legs is plenty conservative with my fuel load and rarely results in a diversion for fuel, and affords more options, especially IFR. I usually need a diversion for other reasons by 3 hours anyway!

The main idea is to not run out of fuel while not crippling your useful range by over-conservative planning. There was a much discussed fuel exhaustion accident on the red board where the pilot carefully fuel planned for what was supposed to be 30 minute reserve (too close for my taste) but turned out to be about a 2-4 gallon (15 minute) reserve (!!!!) You don't want to do that. Pick a reasonable bingo time and stick to it.
 
I plan based on the worst fuel burn in the POH. Since I fly at less than that, The actual number has always turned out to be better.
 
We Experimental guys get to write our own POHs. I like to plan for 8 gph, which is 0.5 more than I typically use in cruise. My personal comfort factor is to never land with less than 1 hour of fuel remaining, and so far I've stuck to it (there was that one flight to Baraboo, WI en route to OSH where I came in right at 1 hour's fuel, and even that felt uncomfortable).

Three to 3.5-hour legs are the sweet spot for me. Just remember it's time aloft rather than distance traveled that matters...always be ready to land short of the original destination for more 100LL!
 
From my experience they want you to be able to plan and calculate via the POH and regulations. Like you I rounded up and while they said I wasn’t wrong it’s not what they are asking.

Taxi and run up said 1.5g, I put 2
Fuel burn 10.5, I put 11
Flight time 1.5, I put 2.

My CFI said anyone can guess how much to be safe. Flying for an hour? Just fill it up! But they wanted to see and know you coups calculate it from real numbers.
 
Again, this is in the context of being an instructor, teaching a new student pilot how to plan a xc. I got tore apart by the teacher for using a higher than POH fuel burn. My reasoning being not every engine is brand sparkly new, and it’s usually better to have more gas left than you’re supposed to (by planning to burn more than you do) in th interest of safety. I’m just having trouble understanding why our teacher has a problem with that. Personally, like most who have responded so far, I will continue to plan the way I do and plan a higher than POH burn.
 
My retort would have been, if the calculation is correct and described correctly, but based on a more conservative burn rate than the POH, that is fine. If the calculation turned out to be an overly optimistic burn rate, but still calculated correctly I would point out the optimism and potential pitfalls.

The only time the "correct" POH number must be quoted should be on the pre-solo written and oral preps.

Note: I'm not a CFI. But I've seen a few professionally. :)
 
airbornejohnny said:
Again, this is in the context of being an instructor, teaching a new student pilot how to plan a xc. I got tore apart by the teacher for using a higher than POH fuel burn. My reasoning being not every engine is brand sparkly new, and it’s usually better to have more gas left than you’re supposed to (by planning to burn more than you do) in th interest of safety. I’m just having trouble understanding why our teacher has a problem with that. Personally, like most who have responded so far, I will continue to plan the way I do and plan a higher than POH burn.
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What was the explanation given by the instructor for why they didn’t like the more conservative approach?

One thing I can think of is that if you decide not to teach your students to use the POH numbers for fuel consumption what else will they deviate from the book on? It can be a slippery slope.

If you were my student I personally wouldn’t care about wanting to be a little more conservative but I don’t think it is necessary.
 
I use book numbers, but I always plan to land with 1hr fuel.
 
Crashnburn said:
The only time you have too much fuel is when the airplane is on fire.
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Well, every gallon you leave behind in some circumstances is another six pounds less overgross you are :)

I compute things exact and adjust my reserves. For checkrides, do it by the book and then explain your additional safety fuel.

In flight, I use the most pessimistic of: my watch (i.e., my preflight calculations), the fuel gauges, and my fuel flow totalizer.
 
Plan it by the book, that's why almost every flight plan I get has dispatcher add, for when the book is wrong!
 
If you use your own numbers, you lose margin flying in mountains and weather due to additional weight.
I was taught to calculate per the POH or based on actual numbers from previous trips based on how you fly (e.g. 50% power LOP vs 65 ROP in the POH)

You do NOT fudge your fuel requirements, instead you adjust your reserve requirements till you are comfortable.

The anecdotal example given was a friend of the instructor who always planned 18GPH in the Bonanza vs the 16GPH he flew with. One time strong headwinds and a heavy load conspired to use up the planned one hour reserve. But he counted on the extra couple of gallons, so he pushed on.... till he ran out of gas. Got lucky and landed on a road.

Using the wrong numbers you are lying to yourself and counting on that as a special reserve later. Best bet, do not lie to yourself, and just admit you want land with two hours of fuel.

How many other performance metrics will you lie to yourself about?

Sent from my SM-J737T using Tapatalk
 
Plan per the POH during checkout/fam flights. Then use your actual numbers there after. You're accuracy improves the more you fly that airplane. If your weight won't be a factor with planned fuel, there's no crime in carrying more. Just as there's no crime in landing for fuel before you need to.
 
tspear said:
Using the wrong numbers you are lying to yourself and counting on that as a special reserve later. Best bet, do not lie to yourself, and just admit you want land with two hours of fuel.

How many other performance metrics will you lie to yourself about?
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You'd have to be an idiot to "count" on that reserve being there later. You won't get two pilots that can lean identical or even match trying to reach a specific POH LOP-ROP BHP setting without a great engine analyzer (this was a CFI being questioned which means the rental probably has crap for avionics).

I trained in a Sparrowhawk converted 152's for high DA in my area. After conversion they were allowed to operate with the same POH. Flying them you'd find the fuel burn was at least 15-20% higher after the conversion ... so technically I guess I was fudging calculating a 7.75 GPH burn rather than 6.0 and mine was nearly dead on ...
 
danhagan said:
You'd have to be an idiot to "count" on that reserve being there later. You won't get two pilots that can lean identical or even match trying to reach a specific POH LOP-ROP BHP setting without a great engine analyzer (this was a CFI being questioned which means the rental probably has crap for avionics).

I trained in a Sparrowhawk converted 152's for high DA in my area. After conversion they were allowed to operate with the same POH. Flying them you'd find the fuel burn was at least 15-20% higher after the conversion ... so technically I guess I was fudging calculating a 7.75 GPH burn rather than 6.0 and mine was nearly dead on ...
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How many times do pilots still run out of gas today? How often does ducking under the cloud to beat the weather result in CFIT due too VMC to IMC?
Humans in general have an amazing ability to rationalize almost anything. Therefore, for simple items like a fuel calculation, why lie to yourself?

Tim
 
I like the approach of being conservative and accurately informed than I like having a vague fudge factor. With accurate info I know what the margins are. Fudge factors are for days when the plane will carry way more fuel than I need and I just need to quickly estimate the trip's requirements.

Even an old engine will use gas at the rate the book says it will, as long as it's reasonably healthy (i.e., runs smoothly when leaned to POH specs). What suffers is how efficiently the plane turns that gas into forward motion, so your airspeeds may suffer by a couple of knots. I suspect this CFI is being a little heavy-handed about it, but I prefer to plan on actual fuel burn with conservative airspeeds and reserves. I find that I have a much more accurate picture of how much fuel I have than when I round the fuel burn up.
 
Tim,

tspear said:
The anecdotal example given was a friend of the instructor who always planned 18GPH in the Bonanza vs the 16GPH he flew with. One time strong headwinds and a heavy load conspired to use up the planned one hour reserve. But he counted on the extra couple of gallons, so he pushed on.... till he ran out of gas. Got lucky and landed on a road.

Using the wrong numbers you are lying to yourself and counting on that as a special reserve later. Best bet, do not lie to yourself, and just admit you want land with two hours of fuel.
Sent from my SM-J737T using Tapatalk
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Being conservative is different than the scenario you laid out above. The guy believed he had more fuel than he did, AFTER he burned through his hour reserve. Using a more conservative number for burn rate and FLYING conservatively, means nearly always ending up with more fuel than you expect when you land refuel and staying well above legal reserve minimums. In your example, there was nothing conservative in how he flew.
 
@Hang 4

You are missing the point. Regardless of what you call it, if the plane burns 16.1 GPH consistantly and that is what you lean for; and then you use 17 GPH you are not being conservative. You are lying to yourself. At some point, you are going to be a on flight and say, oh I really have an extra 4 gallons since my real fuel burn is lower than plan for the first four hours....
A gallon here, a gallon there... pretty soon you are talking about 25% of the fuel load of the plane.

Tim
 
No - Plan and FLY the more conservative number. The lying part is how you treat the gap between the two.
 
tspear said:
How many times do pilots still run out of gas today? How often does ducking under the cloud to beat the weather result in CFIT due too VMC to IMC?
Humans in general have an amazing ability to rationalize almost anything. Therefore, for simple items like a fuel calculation, why lie to yourself?
Click to expand...

To be totally honest, I'd be surprised if ANY pilot on one of these forums would operate in that manner ... their participation here indicates their desire to fly safe. Can bad things happen? Can weather change from what was listed? Sure, but we do what we can to reduce bad outcomes or break chain links.
 
danhagan said:
To be totally honest, I'd be surprised if ANY pilot on one of these forums would operate in that manner ... their participation here indicates their desire to fly safe. Can bad things happen? Can weather change from what was listed? Sure, but we do what we can to reduce bad outcomes or break chain links.
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Yeah, I have been on BeechTalk and other forums long enough that I know people who have crashed and died. When you look at the ADM, you always say, WTF were they thinking.
As much as I may look at participation of a forum showing some interest in skills, learning and good ADM. At the end of the day, we are all human, and there is a bell curve. Therefore, I believe straight honesty and avoiding rationalization is the best medicine.

Tim
 
I add a 2gal/hr buffer. Always have.
 
tspear said:
You are missing the point. Regardless of what you call it, if the plane burns 16.1 GPH consistantly and that is what you lean for; and then you use 17 GPH you are not being conservative. You are lying to yourself. At some point, you are going to be a on flight and say, oh I really have an extra 4 gallons since my real fuel burn is lower than plan for the first four hours....
A gallon here, a gallon there... pretty soon you are talking about 25% of the fuel load of the plane.
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No, YOU are missing the point. The whole point is to assume you will burn 17 GPH. You do not change your assumption mid-flight. That's like changing your personal minimums every time you fly which defeats the purpose of having personal minimums.
 
dmspilot said:
No, YOU are missing the point. The whole point is to assume you will burn 17 GPH. You do not change your assumption mid-flight. That's like changing your personal minimums every time you fly which defeats the purpose of having personal minimums.
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No I get it. You just made you plane less useful and likely less safe. You reduced performance margin in flight, you reduced range, and reduced available carrying capacity. Just because it makes you "feel" conservative. Because this is a minimum you will not touch.

So why carry it?

Sent from my SM-J737T using Tapatalk
 
Jesus dudes.

Just fly the way you normally fly, stick the tanks before and after, calculate YOUR fuel burn, use those numbers and legal or higher reserves, and bobs your uncle.

Not rocket surgery ;)
 
tspear said:
No I get it. You just made you plane less useful and likely less safe. You reduced performance margin in flight, you reduced range, and reduced available carrying capacity. Just because it makes you "feel" conservative. Because this is a minimum you will not touch.

So why carry it?
Click to expand...

Adding a safety margin makes you less safe, okay buddy. You can believe whatever you want to believe.
 
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