What weight does

[Lance F]

I read an article recently that talked about pilots' tendency to really load up on fuel before a trip. Since I've had the expression "you can never have enough fuel" burned into my brain. I frequently would TO for a shorter trip with 7+ hours of fuel.

Today I had a short trip to Greenville (GSP) and back. It flight plans at 46 minutes. So I only carried 3 hours of fuel and just me on board. Wow. OAT was about standard 59dF. Climbed out from 900' elev runway to 5,000 at a steady 1000fpm @ 105kts. This with my tired 200hp 4 banger Lycoming.

I'll always carry a conservative amount of fuel, but seeing this climb rate difference may make me rethink how much extra is really necessary.

 

[gismo]

I read an article recently that talked about pilots' tendency to really load up on fuel before a trip. Since I've had the expression "you can never have enough fuel" burned into my brain. I frequently would TO for a shorter trip with 7+ hours of fuel.

Today I had a short trip to Greenville (GSP) and back. It flight plans at 46 minutes. So I only carried 3 hours of fuel and just me on board. Wow. OAT was about standard 59dF. Climbed out from 900' elev runway to 5,000 at a steady 1000fpm @ 105kts. This with my tired 200hp 4 banger Lycoming.

I'll always carry a conservative amount of fuel, but seeing this climb rate difference may make me rethink how much extra is really necessary.

Tankering fuel can indeed be wasteful and being light actually improves safety at takeoff and landing as long as you don't run short. I often leave my aux tanks empty or partiall full unless I expect to be taking a max range trip. With rare exceptions I always have at least 2-1/2 to 3 hours of fuel at takeoff, even for a short hop. Full fuel is 5.5 hours. Given my fuel burn, every hour of fuel is at least 150 lbs.

 

[NC Pilot]

According to one of the Airline's mags (USAir I think) they said it takes one gallon of fuel for every three they carry. So it makes sense to not carry any more than what is needed (with margin of course).

However, the primary reason I fill my tanks after every flight is to avoid the potential of water condensation in the fuel tanks. True especially in the humid South East. Perhaps if I was going on a short flight the next day and had plenty of fuel left I may not tank up.

 

[gismo]

According to one of the Airline's mags (USAir I think) they said it takes one gallon of fuel for every three they carry. So it makes sense to not carry any more than what is needed (with margin of course).

However, the primary reason I fill my tanks after every flight is to avoid the potential of water condensation in the fuel tanks. True especially in the humid South East. Perhaps if I was going on a short flight the next day and had plenty of fuel left I may not tank up.

Are you in a hangar or outdoors? I think the issue of condensation is mostly a myth but I can't say for sure. In the more than 20 years I've owned my own planes, the only times I've found water it was clearly from rain not condensation. Of couse this might be because most of those planes had bladder tanks which offer some insulation between the fuel and the wing surface, especially the top one.

 

[Dave Krall CFII]

I read an article recently that talked about pilots' tendency to really load up on fuel before a trip. Since I've had the expression "you can never have enough fuel" burned into my brain. I frequently would TO for a shorter trip with 7+ hours of fuel.

Today I had a short trip to Greenville (GSP) and back. It flight plans at 46 minutes. So I only carried 3 hours of fuel and just me on board. Wow. OAT was about standard 59dF. Climbed out from 900' elev runway to 5,000 at a steady 1000fpm @ 105kts. This with my tired 200hp 4 banger Lycoming.

I'll always carry a conservative amount of fuel, but seeing this climb rate difference may make me rethink how much extra is really necessary.

It's a hassle to defuel and therefore I never cared too much for most clubs' policies of topping off all the time for aircraft performance reasons since I like to frequent short airstrips but, for instructing it can be good so the flight students will get more full gross performance experience automatically.

 

[NC Pilot]

Are you in a hangar or outdoors? I think the issue of condensation is mostly a myth but I can't say for sure. In the more than 20 years I've owned my own planes, the only times I've found water it was clearly from rain not condensation. Of couse this might be because most of those planes had bladder tanks which offer some insulation between the fuel and the wing surface, especially the top one.

I'm hangered and it may be an OWT, but I've always filled my tanks when I put the plane away. One reason is for the condensation concern, the other is my trips are not always known far enough ahead of time to call the airport and tell them to tank up. Lastly, I have a useful load of 800 lbs with full tanks, so even with full tanks I can still carry four people (or my wife, two kids, two small dogs and baggage) and still be legal. So, it's just easier to fill the tanks when I put the plane to bed and not worry about it.

 

[Let'sgoflying!]

IMO because the fuel exhaustion scenario is so common, (or at least so much more likely than a problem with too much fuel), we are always being pushed to carry all we can, fill up every chance we get.
Not a bad idea (usually); really depends on the airplane, types of flights undertaken and the pilot's level of experience in my view - so many variables.
When I last flew an airplane with an endurance of 90 mins across the flat wilds of the south, I was filling every airport I saw. With long range tanks, lots of people, or at hi DA you can't always, or don't need to 'topitoff'!

There are so many considerations now, will the planned airport even have fuel (or will it be 5$ a gallon!), what if you have to turn back for wx, how much baggage/pax will you return with, will you leave when it is hot tomorrow pm or early morning? I find myself thinking two flights ahead where able to made that decision. Tomorrow I am going with two people, no bags and 40 gallons to a high dollar fuel place A, where we will pick up 100# in supplies, then go to B where we pickup a pax, (no fuel available there) and then I want to fill up at a stop C on the way back to A because C is 2.68/gal BUT I am doing the annual Monday so I really don't want all the tanks full because it makes it hard to move around! How much gas should I get at B or C if the wx is good vfr (and we return by dark)?

 

[gibbons]

Are you in a hangar or outdoors? I think the issue of condensation is mostly a myth but I can't say for sure. In the more than 20 years I've owned my own planes, the only times I've found water it was clearly from rain not condensation. Of couse this might be because most of those planes had bladder tanks which offer some insulation between the fuel and the wing surface, especially the top one.

I very, very seldom find water in the tanks. However, I've been told by several mechanics that keeping full fuel in the bladders will extend the life of the tanks. I don't know if it's true or not, but I generally top off the Bonanza after a flight.

 

[gismo]

I very, very seldom find water in the tanks. However, I've been told by several mechanics that keeping full fuel in the bladders will extend the life of the tanks. I don't know if it's true or not, but I generally top off the Bonanza after a flight.

Yeah, I've heard the same thing as well, but I suspect it's also at least part OWT. For one thing, topping the tanks doesn't actually "fill" them, there's always an air bubble at the top and if trapped air could dry out the bladder, the spot where the bubble normally sits would dry out pretty quick. Also for those who insist the fuel vapors are what "preserves" the bladder, they are present in about the same concentration when the tanks are nearly empty. Then theres the fact the materials used in today's bladders are far more robust than what was originally used AFaIK and it wouldn't surprise me that avfuel is actually what eventually damages the bladders if there's any chemistry involved. Finally if fuel is actually somehow beneficial to the bladder material, it's much more likely that sloshing it around in flight is the key, not keeping them nearly full while sitting on the ground. Personally I suspect that the only thing that shortens the life of fuel bladders is leaving the plane out in the sun when it's hot which heats up the tops of the bladders though conduction and radiation. In that case having fuel in the tanks might actually help as it would keep the temp of the bladder lower.

 

[gibbons]

Finally if fuel is actually somehow beneficial to the bladder material, it's much more likely that sloshing it around in flight is the key, not keeping them nearly full while sitting on the ground.

If that's true then I'm sure most of my landings are good for the fuel bladders.

 

[NC Pilot]

Personally I suspect that the only thing that shortens the life of fuel bladders is leaving the plane out in the sun when it's hot which heats up the tops of the bladders though conduction and radiation. In that case having fuel in the tanks might actually help as it would keep the temp of the bladder lower.

I think that is what the real story is behind topping off the fuel tanks to preserve the bladders. It keeps the bladders from getting hotter and degenerating when the plane is parked out in the sun.

 

[Anthony]

I have never experienced condesation in my tanks inside or outside. I used to be a proponent of keeping the tanks filled, but with my Tiger even at sea level I have to trade fuel for back seat passengers. However, with 38 gallons out of the 51 total useable, I can still have close to a 4 hour indurence so three hour legs are doable. When I moved to Colorado, this is more the norm than the exception if we do any mountain flying at all. I now have the more the mentality of fuel to the tabs or my leg distance plus 1 hour fuel instead of just filling it up all the time. This is less of a concern in the winter months where the plane performs better because DA's are much lower.

 

[wsuffa]

These days, the extra fuel weight can hit your pocketbook, too! Or not.

Down here, there is a $1.00+ per gallon difference between airports that are 20 miles apart. That's a significant chunk of change, especially if I can run 50-gallons or so out of the tanks before refilling. My home base airport is more expensive than T89, for example, so it makes sense to fill over there.

The added weight will make some difference in climb rate (and therefore fuel burn), especially if you have a turbocharged engine. I figure the math this way: Fuel burn during climb = 21-22 GPH, fuel burn during cruise = 11-12 GPH. Saving 6 minutes of climb time will save 1 gallon of fuel. An extra 100 ft/min (if your baseline is 500 FPM) of climb rate will yield 6 minutes of savings if you climb to 18,000' (OK, so I go to 17K on long trips, same difference). Now you need to figure the weight savings you need on your plane to get that additional climb rate.

From a practical perspective, for the kind of flying I've done (typically longer flights), I'll usually depart full from the nearest "cheap" gas. If I have plenty of fuel to make it to a cheaper fuel stop (or home and later on to the cheaper airport), I'll depart and go fill up elsewhere. I did that recently on a trip SSF-LBX-AUS-SSF. SSF was $3.75/gal at the time, LBX was $2.60, AUS was $4.20. So I took on just enough fuel to make LBX (with reserves), filled at LBX, stopped at AUS (paid a ramp fee in lieu of fuel - it was cheaper), then came on back to SSF. The next hop will be to T89 for fuel...

 

[poadeleted20]

In the Cougar and Tiger both, I routinely refuel only to the tabs (3+30 in the Tiger). If I need more for a long flight, I'll top off at that time, but I like the increased performance and flexibility afforded by not routinely topping off, and don't view flying with "only" two hours reserve on most flights to be a significant increase in risk.

 

[AirBaker]

Are you in a hangar or outdoors? I think the issue of condensation is mostly a myth but I can't say for sure. In the more than 20 years I've owned my own planes, the only times I've found water it was clearly from rain not condensation. Of couse this might be because most of those planes had bladder tanks which offer some insulation between the fuel and the wing surface, especially the top one.

I have gotten water in the fuel when having mostly empty tanks. Only happened once, and we were hangared at the time.

But... who knows.

 

[ejensen]

I now have the more the mentality of fuel to the tabs or my leg distance plus 1 hour fuel instead of just filling it up all the time. This is less of a concern in the winter months where the plane performs better because DA's are much lower.

Ditto. I run tabs most of the time (50 gals). Sure helps get over the top in the summer. That's 4.5 hours.

Eric