Fuel Management

[harrold philippi]

I have read in the POH and it states "fly for one hour, switch tanks, fly on the second tank until fuel is exhausted. Than switch back." My question is, since I do not have a low pressure warning light how much time do you have once the pressure gage starts oscillating before the engine quits running? I have attached page below.

[TheAv8r]

I've never wanted to experience it, so I'm not sure, but I ran one tank dry once on purpose before I put in new fuel senders and when the fuel PSI started dropping, power started dropping linearly along with it. Anything that could cause loss of power inflight is something I'm avoiding.

I personally would not fly it this way per the POH... They're doing that so you can estimate your fuel burn and use that to calculate the other tank. If the plane is new to you, fly conservatively. Estimate a few gallons higher, switch tanks every 30 minutes or 1hr and then see what you add in the tanks at the end of the flight, divide by total time and after a few flights you'll get a feel for how much it's burning. 

I have a JPI 930 with CIES fuel senders in my bird which have been accurate within 1/10th of a gallon so I have the luxury of always knowing what I'm burning and how much gas are in the tanks. Before I had that upgrade, I wouldn't fly longer than 4hours period, switching tanks every 30 minutes.

[Hank]

Running a tank empty is no big deal. I generally switch every hour, which is good for 4 hours.

The way I run my C, I can get 2:45 or so out of a tank, usually done only on long trips so that I'll have the last 90 minutes or so in one tank.

Since we have pretty low fuel pressure anyway (seems like I'm generally 1.0-2.0 psi), putting a fuel pressure warning in would be difficult. So I fly and switch tanks by the yoke clock.

P.S.--our fuel injected brethren seem to run 25-30 psi fuel pressure. My green line goes down to 0.5 psi, with a red line at 6 psi, so take the advice.of anyone with an E, F, J or later with a large amount of salt, they're comparing their oranges to our apples.

[Fly Boomer]

3 hours ago, harrold philippi said:

I have read in the POH and it states "fly for one hour, switch tanks, fly on the second tank until fuel is exhausted. Than switch back." My question is, since I do not have a low pressure warning light how much time do you have once the pressure gage starts oscillating before the engine quits running?

I have no personal experience, but I have flown with someone behind a carbureted engine, and this is SOP for him.  When his fuel gauge gets down toward the bottom, he starts checking fuel pressure more often and, when it gets wonky, he switches.  Usually not even a hiccup from the engine.  Apparently, having a little gas in the float bowl keeps it from suddenly going silent.

[Hank]

12 minutes ago, Fly Boomer said:

I have no personal experience, but I have flown with someone behind a carbureted engine, and this is SOP for him.  When his fuel gauge gets down toward the bottom, he starts checking fuel pressure more often and, when it gets wonky, he switches.  Usually not even a hiccup from the engine.  Apparently, having a little gas in the float bowl keeps it from suddenly going silent.

Even being watchful, you can't count on fuel pressure dropping or even the engine coughing. Sure, it often does, but I've had it stop quicker and smoother than at shutdown. The prop keeps turning, though, and the engine starts back as soon as fuel is restored. Just nudge the throttle back a little bit first . . . .

[N201MKTurbo]

I always like to have some fuel in each tank. That is part of your redundant systems. If you run a tank dry, you have no options. 
 

I switch every 1/2 hour. I still have an analog stopwatch clock. If the minute hand is on the left, I’m on the left tank, if the minute hand is on the right side of the clock, I’m on right tank.

[Pinecone]

OTOH if you run the fuel fairly low, I would prefer 15 gallons in one, the other empty. Than having 7.5 in each

[N201MKTurbo]

3 hours ago, Pinecone said:

OTOH if you run the fuel fairly low, I would prefer 15 gallons in one, the other empty. Than having 7.5 in each

But if you run out the crash site is still in the same place.

[McMooney]

I have an E and run per the POH but with a hard 4ish hour limit, 3ish hours if IFR. ( adjust for fuel flow )

In the E, the fuel gauge starts to wiggle when the tank gets low, that's when you switch it won't shut off.  Just time it.

 

actually it's not really an hour limit, it's more of a tank limit.

Tank1 is for Takeoff/landing

Tank2 is for getting there.

once back on tank1, i'm already on the approach  or within 30mins of a VFR pattern. 

So far, I've landed with a minimum of 1 to 1.5 hours in tank1 when pushing it vfr

OH yeah, engine restarts are a non event, switch tanks it restarts almost instantly.  hopefully you didn't piss off Murphy that day.

from experience, do NOT let the engine stop when riding with the copilot/cfo, really bad things will happen to you

 

 

Edited June 1, 2023 by McMooney

[Greg Ellis]

I have run the tank dry before on my C model per the POH (if that is what you want to call the pamphlet that came with my airplane).  It was and is a non event in my airplane.  Not even a hiccup.  Just did it this past weekend to completely drain a tank that needed the fuel drain replaced.  

On my C model there was plenty of time between a drop in fuel pressure and engine stoppage and never really got to that point.  I do have a friend who had an A model that when he did this it shocked him how quickly the engine quit with no real time to get prepared.  So I think that you will find something different between airplanes even with the same engine and fuel delivery setup.

[BloodRedSkies]

Running a tank dry isn't a big deal. That's pretty much how you know when to switch in a multi. 

[RobertGary1]

In 20+ years of flying my Mooney I’ve never terrified my passengers with an engine shutdown over the spikey mountains of the sierras or out over open water, etc. I just keep a fuel log driven off the fuel flow counter and compared with the gauges. I don’t see any reason to run a tank dry. Never been off more than 1 gal of how much is in each tank. 

[PT20J]

I used to fly float Beavers part 135. The fuel tanks in the Beaver are in the belly. You have to be circumspect about putting fuel in the aft tank due to CG considerations. On long flights with a light load, we would fill the aft tank to avoid a fuel stop, but it was SOP to run that tank dry for the next pilot. When the gauge got low, we would watch the fuel pressure and when it would drop you had a few seconds to switch tanks before the float bowl ran out of fuel and the engine would die. The problem was that it’s several minutes between low fuel level and low fuel pressure and it is easy for a distraction to take your attention away from the fuel pressure gauge. I can tell you from experience that passengers hate it when the engine quits. After that, I decided that a couple of gallons didn’t amount to enough to be worth it.

Skip

 

[Hank]

1 hour ago, RobertGary1 said:

In 20+ years of flying my Mooney I’ve never terrified my passengers with an engine shutdown over the spikey mountains of the sierras or out over open water, etc.

Tell 'em what's going to happen, and react yourself like it's nothing to worry about, your pax will stay calm.

Surprise engine events are not pleasant for anyone, especially the uninitiated. A small dose of easy-to-understand briefing before it occurs will go a l-o-o-o-o-n-n-g-g-g way for you.

[0TreeLemur]

6 hours ago, N201MKTurbo said:

But if you run out the crash site is still in the same place.

Bonus: by starting with 7.5 on both sides, you now have two opportunities to run out of fuel!

[PT20J]

Running the tank dry must be a good idea because all the airlines do it, right? And, the airlines always try to dispatch with minimum legal fuel because tankering extra fuel costs money. 

[Jim Peace]

1 hour ago, PT20J said:

the airlines always try to dispatch with minimum legal fuel because tankering extra fuel costs money. 

I tankered a lot of fuel this morning into Mexico City...we saved thousands according to the paperwork...depends on fuel prices....

[Fly Boomer]

2 hours ago, Hank said:

A small dose of easy-to-understand briefing before it occurs will go a l-o-o-o-o-n-n-g-g-g way for you.

I would say that's great advice surrounding any event not previously experienced.

[Fly Boomer]

1 hour ago, 0TreeLemur said:

Bonus: by starting with 7.5 on both sides, you now have two opportunities to run out of fuel!

Somebody finally said the quiet part out loud.

[A64Pilot]

13 hours ago, Pinecone said:

OTOH if you run the fuel fairly low, I would prefer 15 gallons in one, the other empty. Than having 7.5 in each

That’s exactly the advice given to me by a very experienced Ferry pilot, if you KNOW one is empty then you’re more likely to divert and land etc. but if you have fuel in both sides your more likely to overestimate the amount of fuel remaining.

So far as running out of fuel, it’s exactly like it us in a car etc. you’ll lose power, then it usually comes back, engine may stumble etc., but you switch tanks and it comes back, remember the prop will keep windmilling. I’ve not had one just suddenly stop with no warning.

Personally I burn 10 gls then switch tanks, If I burn 20 out of a tank then I consider it empty. I have bladders so I hold something like 54 or something, I forget.

I don’t even come close to pushing fuel, those days are behind me

 

[N201MKTurbo]

It’s amazing how many people run out of fuel on final….

[MikeOH]

2 hours ago, N201MKTurbo said:

It’s amazing how many people run out of fuel on final….

"Missed it by that much"....Agent 86

[RLCarter]

I’ll be honest, I haven’t read every post in this thread. That being said, I personally never stretch my fuel and try and switch tanks well with gliding distance to an airport, I’m just not in that big of a hurry

[211º]

I alternate 10 from each tank twice for a total of 40 used. I have a hard rule that I will land - regardless of how much father - before switching “just one last time.”

So my 5 hour flights are always LOP at 7.5 gph even though I could probably do it a little quicker ROP and use just a little over 40 gallon.

[Hank]

On 6/2/2023 at 12:41 PM, 211º said:

I alternate 10 from each tank twice for a total of 40 used. I have a hard rule that I will land - regardless of how much father - before switching “just one last time.”

So my 5 hour flights are always LOP at 7.5 gph even though I could probably do it a little quicker ROP and use just a little over 40 gallon.

I've gone 4:45 twice in my C due to headwinds, I don't like legs that long, it's nice to stand up and walk around occasionally. Both times I put in 40-42 gallons, leaving ~1:20 in reserve. Good enough for me!

Learn your plane and your fuel burn.