Fuel Management

[toomany]

i've got a comanche that i'll run the 15 gal aux tanks dry on longer trips, but i usually keep splash in whatever main i select after the aux tanks are dry- this also depends on how high or cold i'm flying. i don't run tanks dry when OAT is below 30 to 40° F.

I ran the bravo dry on a tank once and it took longer than i expected to regain power, so o don't run them dry. it also runs a little hotter so i try to avoid anything that would cause quick decreases in cht's -  shock cooling. 

on switching tanks - i always burn the opposite tank that's into the wind in the bravo until about 1/4 to 1/2 full depending on wind to help the AP out a little. once both tanks are 1/2 or less i'll burn the leeward tank to about 5 gallons then switch to the upwind tank. 

had a tank run dry once in the comanche on final into va kpvg at about 500 agl - had the whole family aboard. i always fly higher and faster patterns so we still would have made it w/o power, but it woke me up. a great pilot once told me the cheapest insurance you can get is fuel, altitude, and airspeed. 

[Pinecone]

What does wind in cruise have to do with anything????  

FYI, I do not typically run the tank dry.  Maybe run 10 minutes or so after the low fuel light comes on to maximize fuel in the fuller tank.  I do not plan or fly that close to both being empty.  

[RoundTwo]

10 hours ago, toomany said:

 i always burn the opposite tank that's into the wind in the bravo until about 1/4 to 1/2 full depending on wind to help the AP out a little. once both tanks are 1/2 or less i'll burn the leeward tank to about 5 gallons then switch to the upwind tank.

The plane, and AP, are oblivious to wind direction. Like a boat on the ocean, without ground reference, currents are unknown. 

[Hank]

1 hour ago, Pinecone said:

FYI, I do not typically run the tank dry.  Maybe run 10 minutes or so after the low fuel light comes on to maximize fuel in the fuller tank.  I do not plan or fly that close to both being empty.  

Oh, you and your fancy plane, with Low Fuel warning lights! I have two needles on the far side of the panel, so I fly by the clock in the yoke that I'm holding. Usually two 1-hour segments, but on long trips the first tank will be one hour, then an hour on the other, then 90 minutes on the first tank.

On really long flights, I'll go a little longer than 90 minutes, but realistically there's only another 15-20 minutes unless I've been extra lean.

[RobertGary1]

15 hours ago, Denis Mexted said:

In another life I would fly heavy Chieftains 3 hours out to sea and land on a small bit of bitumen. (Lord Howe and Norfolk Island)

Past half way, there was no other place to land. We always ran tanks dry. If you were alert fuel lights would give you ten seconds notice to change. But mostly it was a bit of a surge. 
We never had a problem. 
If you’re doing any sort of range flying I think it’s a good idea to have real world figures of what’s in your tanks. 

That’s why they invented the totalizer

[Skates97]

On 5/31/2023 at 3:59 PM, 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.

This is my SOP depending on flight time. I take off on one and switch after an hour, that typically leaves me with 14-15 in the tank depending on how long I spend in the climb. I will either run the new tank dry, or if I will be landing with 10 in it I will stay on that tank the remainder of the flight. If I will be landing with under 10 I will switch on descent. I like to be landing with 10 in whatever tank I am flying on.

As to running dry in a carbureted engine, it is a non-event. I have done it many times. I have CiES fuel senders and know when the EDM900 says zero I have about 10 minutes left on that tank and start watching the fuel pressure. When it starts dropping, I just switch tanks. Even before I had that setup with just 1965 factory gages, I would go off time and just keep an eye on the fuel pressure to know when to switch.

My experience is that once you see the fuel pressure begin to drop you have about 5 seconds to reach down and switch the tank before everything goes quiet. If you have a fuel flow meter expect to see it spike up momentarily as the carb bowl is refilled, then it will level back out.

There have been a couple times where I got distracted and didn't notice the pressure dropping and the engine quit, which gets your attention, but it starts back up once you switch tanks.

[toomany]

13 hours ago, RoundTwo said:

The plane, and AP, are oblivious to wind direction. Like a boat on the ocean, without ground reference, currents are unknown. 

i'll have to tell my auto pilot that wind doesn't have any effect on the aircraft. When you're taking 30-40 knots off the left side heading north at 16000' and your AP is steering into the wind to keep true course corrected it's easier on the clutches to keep the weight into the wind. Unless i'm flying a hang glider i usually have a ground reference i'm using - it's most times the destination. 

[kortopates]

…When you're taking 30-40 knots off the left side heading north at 16000' and your AP is steering into the wind to keep true course corrected it's easier on the clutches to keep the weight into the wind…

Perhaps you could take a stab at explaining how that’s helping or easier on the clutches of your AP?


Sent from my iPhone using Tapatalk

[Pinecone]

So, you fly wing low into the wind during cruise?   REALLY?

In cruise flight, yes, a cross wind moves you in relation to the ground, but your or your autopilot uses a wings level crab angle to maintain the desired ground track, NOT wing low.

This is almost as good as the fairly well known You Tube pilot that says that in a steady rate, level turn, the up wing has higher lift than the low wing.

[toomany]

14 hours ago, kortopates said:

Perhaps you could take a stab at explaining how that’s helping or easier on the clutches of your AP?


Sent from my iPhone using Tapatalk

if you are wing heavy on one side the aircraft will tend to want to turn in that direction. i often fly close to gross and heavily weighted on one side due to passengers and or fuel (long range tanks) - i had to have my ap clutches adjusted due to slippage from it trying to maintain true course in the above situation. 

if you maintain that fuel and/or cabin loading plays no part in this situation, give it a try. load up heavy on one side (fuel and cabin) and give it a go. 

[Pinecone]

I agree that loading is an issue.

I do NOT agree that a crosswind in cruise will have ANY effect on the clutches.

[PT20J]

It’s good to keep things fairly well balanced laterally since the airplane will be more efficient. The GFC 500 has a fuel imbalance limitation of 15 gal. for the M20J/K.

When flying in a crab (not a slip) to compensate for cross track drift due to a crosswind, the wings are level and the ball is centered, so there is no constant force on the servo clutches.

[toomany]

1 hour ago, PT20J said:

It’s good to keep things fairly well balanced laterally since the airplane will be more efficient. The GFC 500 has a fuel imbalance limitation of 15 gal. for the M20J/K.

When flying in a crab (not a slip) to compensate for cross track drift due to a crosswind, the wings are level and the ball is centered, so there is no constant force on the servo clutches.

not sure i agree w you on that one - when i'm hand flying in a steady crab due to winds off of one side i have to maintain continual aileron into the wind, which increases if i'm wing heavy opposite wing.  ball is centered because the ac is trimmed w rudder and aileron for the wind.  

i feel like i'm explaining something too much that i don't care whether people agree with or not - when you take your aircraft in for ap work because the clutches are slipping because you've flown it too long w the ap compensating too much for out of balance situations maybe it'll make sense. 

[PT20J]

3 hours ago, toomany said:

not sure i agree w you on that one - when i'm hand flying in a steady crab due to winds off of one side i have to maintain continual aileron into the wind, which increases if i'm wing heavy opposite wing.  ball is centered because the ac is trimmed w rudder and aileron for the wind. 

A steady wind doesn’t affect an airplane in flight. The airplane moves through the air and it doesn’t matter aerodynamically how that air is moving relative to the Earth. 

You have to be careful about trimming in an airplane with rudder trim. Having the ball centered is not itself an indication of proper trim. The wings must be level AND the ball centered. There is a aileron-rudder interconnect spring on Mooneys and if the rudder trim is not set correctly, the spring will deflect the ailerons causing the airplane to fly one wing low which of course the autopilot will have to compensate for.

[Pinecone]

11 hours ago, toomany said:

not sure i agree w you on that one - when i'm hand flying in a steady crab due to winds off of one side i have to maintain continual aileron into the wind, which increases if i'm wing heavy opposite wing.  ball is centered because the ac is trimmed w rudder and aileron for the wind.

Then you have a rigging problem.

A few months ago I was flying with almost 80 knot winds at altitude (good thing NOT on the nose, so effectively about 20 knot headwind).   NO aileron force.  The airplane doesn't know what the winds aloft are and doesn't care.  YOU care as you are trying to go somewhere.