How close will you get to empty?

[MooneyDriver78]

That makes no difference in Indicated vs True Airspeed.

Oh... If it is because I suggested 10K, that comes from your saying you fly at 8000 *+*... Pick any high altitdude you want. But the bottom line is you do not fly slower up high.

Yes I do. Normally aspirated engines loose HP as altitude increases, so TAS and IAS both decrease, obviously TAS not as much because there is less drag.

You have a turbo engine, so you don’t have that.

 

[Let'sgoflying!]

How close will you get to empty?​

When I was a 18yo new pilot working at a the desk of a small airport, we came in at 7:00 one morning to open up.
The lineman fired up an Apache and taxied to the pumps to ready it for the day's training, knew it needed gas because the night before, one of the CFIs had it out on a late night date to a distant airport restaurant.
Enroute to the pumps one of the engine died from fuel exhaustion.
I never heard if the cfi was fired but he should have been shaking in his shoes as the chief pilot was one tough nut.

 

[X3 Skier]

When the float gage in the header tank right in front of my face starts to go down, there’s an hour left. I never let that happen on purpose and if it does, I divert.

 

[chemgeek]

Hard pass for me when the current estimated ETA eats into a 1 hour reserve. That's 3+30 total flight time for me at typical cruise settings. I have on occasion stretched range by throttling back to a painfully slow but economical cruise, but the 1-hour reserve remains: it just comes at a longer distance. I don't use anything but an rpm setting and a watch. I'm usually within +0 to -2 gallons of estimated fuel consumption for a near max range flight.

Fuel exhaustion is the #1 preventable accident. I've never regretted making an extra fuel stop. Better to be thinking "I could have made it" than "oh boy I should have stopped for fuel."

 

[midwestpa24]

I’ve done that before on a long leg, at altitude.
I hadn’t learned to watch fuel pressure.
It just kept getting closer to empty.
I got distracted.
Then rpm went way down & I crushed a lump of coal into a diamond.
Still came right back up when I switched tanks & kicked on the pump.

I've been there before too. My fuel management plan in the Comanche is to take off on one of the mains, 30 minutes into flight switch to opposite aux tank, 1 hour later switch to the other aux tank, then 1 hour back to the opposite main, so on and so forth.

I was nearing the end of the hour on the 1st main, so switching tanks soon was on my mind. Right around that time I entered hard IMC, rain, bumps, etc. ATC was talking to me, switching frequencies, granting deviations when the engine coughed then quit. Fortunately that snapped me back into fuel management and I knew immediately what needed to be done. Boost pump on, switch tanks, count to 5 and the engine was purring again.

 

[FORANE]

When the float gage in the header tank right in front of my face starts to go down, there’s an hour left. I never let that happen on purpose and if it does, I divert.

Same here. I really like having a header tank because I can run the wing tanks dry without any drama and it isn't likely to unport fuel pickup like with a wing tank.

 

[Ed Haywood]

Normally aspirated engines loose HP as altitude increases

At WOT, yes. At cruise power, not until around 8000 MSL, give or take.

 

[iamtheari]

At WOT, yes. At cruise power, not until around 8000 MSL, give or take.

Oddly enough, that’s the altitude @MooneyDriver78 mentioned above. The only way to keep the same power from sea level up to 12,000 without a turbo is to throttle back to 18” MAP. That’s not cruise power; it’s barely loitering power.

 

[Sundancer]

I trusted the 172 POH numbers for an orbit at 8K-9K MSL, leaned, low power. And they were spot on. The gauges lied a bit, showing somewhat more than what we found dipping the tanks after - yeah, I know, the gauges are not to be relied upon - . I wanna say we were up for 6.5 hours, but that was a while back. Maybe it just felt that way. But the experience solidified my faith in the POH duration numbers.

 

[M20K]

At cruise power, not until around 8000 MSL, give or take.

Kind of my point.

Now if there were only something in the POH (like the Speed Power vs Alttitude) that showed your TAS increasing as you went from SL up to where your engine could not create Cruise Power... Even if you don't have a turbo.

 

[IK04]

I firmly believe the 30 minute reserve is a planning number only. If I use part of that reserve to get safely on the ground, It served its purpose.

 

[William Pete Hodges]

Yes I do. Normally aspirated engines loose HP as altitude increases, so TAS and IAS both decrease, obviously TAS not as much because there is less drag.

You have a turbo engine, so you don’t have that.

Yes, NA engines lose power at WOT as you gain altitude, but most engines cannot be leaned above 75% anyway, so even turbo normalized engines have to reduce power for cruise. And who is to say you have to cruise at 75%? You can cruise at 60-65% and get better fuel economy (especially LOP) with a minor drop in airspeed of about 10-14 MPH. My Mooney is rated 63% all the way to 15,000 feet, at 181-185 MPH, and 877-896 mile range ROP. At 10,000 feet 63% cruises 175-179 MPH with 1001-1024 mile range ROP. That range increases to about 1200 miles if tuned for 63% LOP. So yes, you lose available HP and it does affect rate of climb dramatically as you gain altitude but it doesn't affect cruise as much as think.

 

[WDD]

Back to the OP topic: I land with 2 hours of fuel.

1) I have long range tanks, and I almost always depart with them full.
2) I calculate total flight time burning 15 gallons an hour, which is on the very high side of what's possible. At this high rate, I have 5 hours of flight time.

This gives me a landing with 2 hours of fuel at the minimum, as flying a 3 hour leg is probably the max the wife (and I) would ever do at one time.

Works well for all flying. For close in round trips, I don't have to worry about / take the time to refuel outside home airport. For longer X country / overnights, I don't ever worry about running out of flight time/fuel.

Little downside. I'm going to buy the fuel and burn it anyway, it's not going to go to waste. Even with full fuel load I'm not going to go over weight, so that's not a concern.

So for me, why not take advantages of the plane's fuel and carrying capacity to make the trip a bit safer and more convenient.

 

[Albany Tom]

Back to the OP topic: I land with 2 hours of fuel.

1) I have long range tanks, and I almost always depart with them full.
2) I calculate total flight time burning 15 gallons an hour, which is on the very high side of what's possible. At this high rate, I have 5 hours of flight time.

This gives me a landing with 2 hours of fuel at the minimum, as flying a 3 hour leg is probably the max the wife (and I) would ever do at one time.

Works well for all flying. For close in round trips, I don't have to worry about / take the time to refuel outside home airport. For longer X country / overnights, I don't ever worry about running out of flight time/fuel.

Little downside. I'm going to buy the fuel and burn it anyway, it's not going to go to waste. Even with full fuel load I'm not going to go over weight, so that's not a concern.

So for me, why not take advantages of the plane's fuel and carrying capacity to make the trip a bit safer and more convenient.

Your plan makes complete sense, and I'd do that if I owned my own aircraft. I rent, mostly pa-28-150's, and that aircraft performs a lot better with tabs fuel than full on a hot day, out of a moderate field - say 2500'. So for most trips I'll be local and short, and I'll go a little over tabs, giving me well over an hour by the time I'm back. For long trips, I'll either take an aircraft with more HP, or a cooler day, or whatever it takes to make sure my first leg is fine climbing out.

 

[Mooney Fan]

3 hours and 45 minutes on the tach.

 

[Lance F]

My goal is to land with 40 gallons (on totalizer), about 1.3 hours in cruise.

 

[Rich Holt]

I once landed with 8 gal onboard in my AA5. That is how I found out that the tachometer was incorrect. On my next flight, I took an optical tach with me and found out that when the tach was reading 2300 rpm, the prop was actually spinning closer to 2500. That's when it went back into the shop. I would prefer to land with no less than 10 gallons onboard (1 hr reserve), which equates to about 3 hrs airborne.

On another note, one of the many things that I enjoyed about the T-6A was that it only had 1.5 hr legs, that is about as long as I liked flying around strapped to a rocket seat anyway. Those 1.5 hrs would yield about 600 miles, though.

 

[brcase]

This is a question I like to ask on Flight Reviews. To put into a Scenario form.
You come out the the airport with the intention of fueling and going for a flight, only to find out that the fuel pump at the airport is down.
You know the next airport 5 miles away has fuel. What is the minimum fuel you would take off with to go get fuel at the next airport?

Of course the answer depends on the airplane and personal minimums. Which is the point of the question.

I have had that or similar scenerio's occur several times.

One interesting one was I was asked to pick up an airplane fly to the next airport (4 miles away) where I would pick up my passengers and they would buy fuel for the plane. When I preflighted the 182, that had auxiliary tanks in the extended wing tips, I found it only had about 5 gallons in each main tank confirmed by the fuel totalizer and dipping the tanks.
I will say taking off solo in a 182 with the longer wings and only 10 gallons of gas was impressive. After the 3 minute flight to the other airport and loading 3 passengers and topping off with 90 gallons of fuel (the wing extension increased the gross weight of the airplane). It was quite a different experience taking off at gross weight, more like a loaded Cessna 150 climb performance.

Brian
CFIG/ASEL

 

[AV8R_87]

I sort of implied it in my previous post, but I'll say it again:

It's not just the amount of fuel, it's how it's stored in the tanks. If I'm down to 6 gal (45 minutes), I'd feel a lot more more comfortable with those 6 gallons in one tank than split between two or more.

If I'm ever in a tight fuel situation I would definitely try to use all the fuel from one tank (which might get me the "unusable" fuel as well), before switching to the other one.

Which brings up an interesting question for fuel totalizer users: do you configure it for total fuel or useable fuel?

 

[Half Fast]

Of course the answer depends on the airplane and personal minimums.

Exactly.

My Beech's POH prohibits takeoff with less than 11 gallons in each tank. That's enough fuel for nearly two hours of cruising flight, so the 5 mile distance to the other airport becomes moot; it's the POH that is controlling in your example.

The position and shape of my tanks, along with the wing dihedral, causes fuel less than 11 gallons not to be visible from the filler. There could be 10 gallons in the tank, but by visual inspection and sticking the tank, it could be empty for all you know.

Ya gots to know yer airplane!

 

[Half Fast]

Which brings up an interesting question for fuel totalizer users: do you configure it for total fuel or useable fuel?

Unuseable fuel might as well be air for fuel planning purposes. It only matters for W&B. Why would you configure a totalizer for it?

 

[AV8R_87]

Why would you configure a totalizer for it?

Because it could still be used in a critical situation. Not for take-off and landing, but most likely available in level/coordinated flight.
Understand the limitations of a particular fuel system and use it to your advantage in an emergency.

 

[Ed Haywood]

This is a question I like to ask on Flight Reviews. To put into a Scenario form.
You come out the the airport with the intention of fueling and going for a flight, only to find out that the fuel pump at the airport is down.
You know the next airport 5 miles away has fuel. What is the minimum fuel you would take off with to go get fuel at the next airport?

Of course the answer depends on the airplane and personal minimums. Which is the point of the question.

Our pump has been down for almost a year. Nearest AVGAS is 10 miles away. My minimum is 7 gallons, which is sufficient to takeoff, climb, and cruise for 30 minutes past the other airfield. Below that, I'll borrow a 5 gallon gas can and drive over to fill it.

The real conundrum is what to do if you land at the other airfield and find the gas pump is also inop there. That has happened. I ask around before departing.

 

[Ed Haywood]

most likely available in level/coordinated flight.

Do you know this for a fact? And what level of confidence is "most likely"?

 

[AV8R_87]

Do you know this for a fact?

Run a tank until the engine quits, then see how much it takes to refill it. That's how you know for a particular aircraft.

And what level of confidence is "most likely"?

Determined by the run dry test above, and with a fudge factor to account for the pilot's comfort level.
For my tanks, on a day that's not too bumpy, that would amount to a 90% confidence.

If I'm ever in a situation where I have to rely on that fuel, it's nice to be able to track it.

 

[WDD]

The real conundrum is what to do if you land at the other airfield and find the gas pump is also inop there.

Check NOTAMs. Good chance if fuel is temp not available it will be noted there.

 

[MauleSkinner]

Check NOTAMs. Good chance if fuel is temp not available it will be noted there.

Amazing what doesn’t make it into NOTAMS. Lowest I’ve ever been on fuel in a jet was because there was no fuel at the airport during construction…and no NOTAM.

I actually declared min fuel before engine start.

 

[WDD]

Amazing what doesn’t make it into NOTAMS

True. Just because it doesn’t say “no fuel” doesn’t mean the pump isn’t down, but if the NOTAM does say “no fuel” you can make other plans.

 

[Silvaire]

So you put it off and finally decide to divert with just barely enough fuel then a guy in front of you does a gear up on the only runway.

 

[AV8R_87]

That's what parallel taxiways are for.

 

[Zeldman]

So you put it off and finally decide to divert with just barely enough fuel then a guy in front of you does a gear up on the only runway.

This has been discussed earlier. Doesn't necessarily mean the airport/runway is closed, just means land at your own risk, either on the remaining runway or on the taxiway, or even in the grass next to the runway.

But yes, not something I would want to depend on.

 

[Dana]

I've deliberately flown down to zero fuel...





... but that was in an ultralight (PPG) circling over the airport. I was around 7-8000' when the engine sputtered and quit; it was a nice long (but chilly) glide back down.

 

[brcase]

Our pump has been down for almost a year. Nearest AVGAS is 10 miles away. My minimum is 7 gallons, which is sufficient to takeoff, climb, and cruise for 30 minutes past the other airfield. Below that, I'll borrow a 5 gallon gas can and drive over to fill it.

The real conundrum is what to do if you land at the other airfield and find the gas pump is also inop there. That has happened. I ask around before departing.

Check NOTAMs. Good chance if fuel is temp not available it will be noted there.

A few years ago one of the major vendors of Self Serve fuel systems had a server go down. Essentially every pump of that brand was out of service for a few days. Not every airport with that brand fuel pump was able to get Notams out, in part because they expected them to come back on line at any time. Smaller airports may not have even noticed it down for a day or so.

Brian

 

[Ed Haywood]

A few years ago one of the major vendors of Self Serve fuel systems had a server go down. Essentially every pump of that brand was out of service for a few days. Not every airport with that brand fuel pump was able to get Notams out, in part because they expected them to come back on line at any time. Smaller airports may not have even noticed it down for a day or so.

Brian

Some of the local fields have sketchy data connections for their self serve pods. It's not unusual for them to be down for a few hours without warning. Has happened to me twice. Once the manager took cash. The other time, the connection reset after 30 minutes while I was wandering around the field looking for help.

 

[UngaWunga]

Or self-serve pumps not really being self-serve, and the office mgr has just left for the day. Ran into that on my way to Oshkosh one year. Called his # from the AFD, he came back after dinner to help me out.

 

[Albany Tom]

This is a question I like to ask on Flight Reviews. To put into a Scenario form.
You come out the the airport with the intention of fueling and going for a flight, only to find out that the fuel pump at the airport is down.
You know the next airport 5 miles away has fuel. What is the minimum fuel you would take off with to go get fuel at the next airport?

...

Brian
CFIG/ASEL

Has anyone ever answered that they'd taxi over to their friend's airplane and siphon gas from that? Creative problem solving is a good thing.

Oh, and another plus for the low wing. Way easier to siphon from a 172 to a PA-28 than the other way around...