Fuel tank crosstalk

[FlyingDude]

Hi guys,

Has anyone ever installed an optional crosstalk (crossover, etc. you name it) between the two tanks?  Yes yes, I know why low wings don't have that by default: if the ball is not centered (it never is "perfectly" centered), then the fuel will keep flowing into one tank, which might even lead to fuel starvation.

BUT: 

imagine communicating fuel drains installed at 25% or 50% of the tank height above the tank floor.  They would make sure that, in the intended case, with a competent pilot, fuel gets balanced during the flight; and if the plane is not balanced, then the worst that can happen is that the victim tank will still have 25% or more...

Anyone done it?

Edited February 16, 2021 by FlyingDude

[RLCarter]

Complicated fuel systems are more troublesome than they are worth, switching tanks is way better even if you run one wing dry it isn’t that big of a deal

[1964-M20E]

With standard tanks is is not that big of a deal with one full and one empty.  Now if you had the extended range tanks it may cause more issues.  I generally run the first tank for 1 hour that gives me right at 10 gallons switch to the second tank and run it as long as needed until it is empty or 30 minutes from my destination which ever comes first.  Then switch back to the first tank and get ready to land.

[Skates97]

11 minutes ago, 1964-M20E said:

With standard tanks is is not that big of a deal with one full and one empty.  Now if you had the extended range tanks it may cause more issues.  I generally run the first tank for 1 hour that gives me right at 10 gallons switch to the second tank and run it as long as needed until it is empty or 30 minutes from my destination which ever comes first.  Then switch back to the first tank and get ready to land.

This right here is my SOP, although 1 hour in I usually have about 15-16 gallons left in the tank I started on. Running a tank dry ensures I have all my fuel in one tank for landing instead of having 5-6 gallons in each side. Running a tank dry is also a non-event. If you are paying attention to your fuel pressure you can see it dropping and switch tanks without the engine ever stumbling. If you aren't paying attention it is just a couple seconds from it going quite to starting back up after you switch tanks.

[Hank]

2 hours ago, Skates97 said:

This right here is my SOP, although 1 hour in I usually have about 15-16 gallons left in the tank I started on. Running a tank dry ensures I have all my fuel in one tank for landing instead of having 5-6 gallons in each side. Running a tank dry is also a non-event. If you are paying attention to your fuel pressure you can see it dropping and switch tanks without the engine ever stumbling. If you aren't paying attention it is just a couple seconds from it going quite to starting back up after you switch tanks.

I run one hour on each tank, then 1-1/2 on the first ( + however many more minutes I think I need) before switching to the last tank. I've only needed this twice, both flights went 4:45 (one was three legs [home, 20 minutes out for fuel with inoperative pump, then on to destination], one was a deviation around icing with brutal winds aloft). Both flights were 41-42 gallons to fill (capacity is 52 gallons).

Running dry was a non-event the two times I've done it (only the accidental no-fuel flight above, and once when I was distracted and forgot to switch tanks).

[carusoam]

Dude,

Take this with a grain of salt... or two... or a whole shaker... 

You either have a really good idea...

Or one of us is missing something...

Or.... you didn’t get the wing leveler...

Fuel level is constantly changing... it is the only thing changing weight in the plane... unless the kids are moving around in the back...

 

All it would take is a piece of tube and a pump.... so simple, yet nobody will take the risk of doing it...

See everybody’s methodology above on how to burn and balance... at the same time...

Go Long Body... or add the rudder trim yourself...

Rudder trim lifts the heavy wing, no need to balance the load with a complex, leak producing, system...

 

Flying the magenta line in my M20C... can be done by balancing the fuel...  burn a little more from this side or that side...

 

Go find a bunch of other things to work on... there’s no meat on this bone...

PP thoughts only, electric rudder trim and speed brakes... expensive... probably not worth paying for... but great, when they come with the plane...

If going with the new Big G autopilot... get the rudder trim too...

 

It has to be an incredibly smooth day to ever notice the difference...

Best regards,

-a-

[Old Chub]

as carusome stated

"All it would take is a piece of tube and a pump.... so simple, yet nobody will take the risk of doing it..."

However, unless your aircraft is going to surrender its Standard and go experimental there is no way to do this without going the STC route and I don't see anyone wanting to take on that liability.  

 

 

 

[FlyingDude]

20 hours ago, 1964-M20E said:

.  I generally run the first tank for 1 hour that gives me right at 10 gallons switch to the second tank and run it as long as needed until it is empty or 30 minutes from my destination which ever comes first.  Then switch back to the first tank and get ready to land.

That's the recommended procedure in my '67 E POH

[FlyingDude]

21 hours ago, RLCarter said:

Complicated fuel systems are more troublesome than they are worth, switching tanks is way better even if you run one wing dry it isn’t that big of a deal

Yeah, but I'm reading Weather Flying by Buck and they too state what I had already heard of: people who crashed due to fuel starvation with one tank full... 

I could be on to something or maybe it's a flop like the self-extending gears (not only horn at low MAP but also self deployment of gears). That actually "caused" accidents, so they got rid of it...

[FlyingDude]

17 hours ago, carusoam said:

Dude,

Take this with a grain of salt... or two... or a whole shaker... 

You either have a really good idea...

Or one of us is missing something...

Or.... you didn’t get the wing leveler...

Fuel level is constantly changing... it is the only thing changing weight in the plane... unless the kids are moving around in the back...

 

All it would take is a piece of tube and a pump.... so simple, yet nobody will take the risk of doing it...

See everybody’s methodology above on how to burn and balance... at the same time...

Go Long Body... or add the rudder trim yourself...

Rudder trim lifts the heavy wing, no need to balance the load with a complex, leak producing, system...

 

Flying the magenta line in my M20C... can be done by balancing the fuel...  burn a little more from this side or that side...

 

Go find a bunch of other things to work on... there’s no meat on this bone...

PP thoughts only, electric rudder trim and speed brakes... expensive... probably not worth paying for... but great, when they come with the plane...

If going with the new Big G autopilot... get the rudder trim too...

 

It has to be an incredibly smooth day to ever notice the difference...

Best regards,

-a-

You touched a sore point... I would LOVE to have an autopilot but currently am dumping my money on other trivia (done pucks, now going for tires and tubes and brake line hoses, MAP sensor fix, etc)... You know anyone giving away a non-working accutrak? I can fix the electronics 

If I implemented this, I wouldn't use a pump. Just a pipe link. I'm wondering how much of a level mismatch would be created between the tanks by uncoordinated flight.

maybe I should just put a reminder placard saying "switch tanks"...

[Hank]

4 hours ago, FlyingDude said:

maybe I should just put a reminder placard saying "switch tanks"...

Do you have the windup clock in the yoke? Every time the moving (white) minute hand overlaps the nonmoving (red) minute hand, I switch tanks.

Having 2-1/2 hours' endurance in each tank keeps it interesting . . . .  

[carusoam]

Dude,

May I recommend starting with the known projects before getting bogged down with the write your own STC projects...

unless you are, or know an STC writer... we have a few around here...

 

Also know...

They make these fancy in the inspection panel fuel level gauges.... that are accurate and cheap... cheap on an aviation scale of things...

It helps to have good precision while filling on the ground... or just knowing before you decide how much fuel you want...

There are methods for defueling the plane as well.... all written around here somewhere...

 

How often do you account for useable fuel?

I believe my fuel gauges read zero when no useable fuel is left...  they don’t register anything for the few gallons below...

 

When using a stick... my tanks go dry at the bottom before I get to non-useable fuel...

 

PP thoughts only. Not a mechanic...

Best regards,

-a-

[FlyingDude]

Hey A,

40 minutes ago, carusoam said:

May I recommend starting with the known projects before getting bogged down with the write your own STC projects...

I blame my nature for this  Anyway, my initial thought was to poll the community to see if anyone already did something. You know, maybe one of you was going to say "oh yeah, I did that 5 years ago, it works marvelously"... Can't know that without asking 

Yeah, I have working fuel gauges, too Anyway, I'll go the placard route. I really don't feel like fueling before/after every flight... I don't like the idea of defueling into portable tanks, either. I think it's even illegal in Michigan due to fire hazard ...

Yep, I'll print and laminate the new placard tomorrow ...

[carusoam]

For the most part...

Most people around here...

Are filling evenly...

Then burning evenly...

There are no restrictions for burning all of one tank or the other...

If everything is rigged well....

You might find finger tip pressure on one side of the yoke or the other based on the fuel burned...

The amount of pressure required would give you a hint of how much fuel you have used...  or how much the passenger in the right seat weighs...  

Having a rudder trim would be the fancy way to handle the weight difference in the wings...

Great idea...

What else do you have in mind...?

Best regards,

-a-

[Hank]

23 minutes ago, FlyingDude said:

Hey A,

I blame my nature for this  Anyway, my initial thought was to poll the community to see if anyone already did something. You know, maybe one of you was going to say "oh yeah, I did that 5 years ago, it works marvelously"... Can't know that without asking 

Yeah, I have working fuel gauges, too Anyway, I'll go the placard route. I really don't feel like fueling before/after every flight... I don't like the idea of defueling into portable tanks, either. I think it's even illegal in Michigan due to fire hazard ...

Yep, I'll print and laminate the new placard tomorrow ...

What placard do you need? I stick my tanks before every flight, and now that I'm mkstly flying local instead of interstate, that may be 3 or 4 flights per fill up. I know how much I start with, which gives me a flight time; I know how long I fly, that gives me fuel used. The rest is 2nd grade math. (Then again, I'm an engineer and consider everything up through differential and integral calculus to be "easy math".)

Seriously, if I have 22 gal in the left and 18 gal on the right, that's over 4 hours. Fly 1:15 and put her away. Next time, I have 10 and 18 because I didn't switch tanks, take off on the 18 gal tank and be sure to land in 2 hours, leaving me my Golden Hour in reserve.

Works well for trips, too. Flew 1:15 home once. A few days lagee, hopped 20 minutes for fuel (none at base). Their pump wouldn't work for me, the local A&P or the FBO guy. A quick check of my fingers showed I had 4 hours' fuel, and myntrip was a little over 3 hours. My map and experience showed several choices tomget fuel in the last hour, so off we went. I made sure to change tanks and run one as close to empty as possible so that my remaining fuel would be in one tank--turned out to be about 5 minutes before starting descent, a good place to be with 90 minutes fuel in one tank. Descend power on, reduce throttle to slow down, reduce more for pattern entry, reduce more for descent, go to Idle on short final. The refill was 41 gallons, leaving 12 of my 15 gallons in the tank, or another 1:15 flight time, well past the Golden Hour in reserve.

No checking logs or notepads from last week--dip the tanks and know how many gallons are in each tank, and running one dry is the best way to get max range. My engine may have coughed just before that switch, I kept saying "5 more minutes" on that trip . . . . 

Never guess or hope when it comes to fuel. KNOW how much fuel you have, and where it is, and switch tanks accordingly. If you get worried, stop and buy some. I've made flights where full tanks weren't possible without leaving someone home, and we made a fuel stop where I dipped the tanks and filled each one to 17 gallons for a projected flight time of ~90 minutes. Four hours fuel was plenty, there were clouds and rain about.

[FlyingDude]

45 minutes ago, Hank said:

Then again, I'm an engineer and consider everything up through differential and integral calculus to be "easy math"

Yeah, I'm an engineer too and spent years using Maxwell equations and Green's diades on a daily basis... Now I'm a manager, so I just talk all day long

It's not the math, it's the having to do the math. I don't know guys, it's psychological. If I could forget about it, I'd be a happier man.

Here's my new placard. Just reminding me to check on these items to make sure they're congruent with the current phase of flight. 

 

[FlyingDude]

Here's my other placard. The first one fell off, I'll laminate this one. 

 

[Hank]

There's no math for fuel, I literally count on my fingers. Each tank hold 2-1/2 hours, giving mr 5 hours' duration. That leaves ~45 minutes in reserve, or a little more, split between both tanks. Thus on long flights, the second time on one tank I burn as much as I can  so the reserve is all in one tank.

There is a little math when I depart without full tanks. Dip the tank, divide gallons by 9 and that's my flight time on that tank. Makes it easy to tell if I have enough for a trip or not. Weight and balance (on a spreadsheet if I'm close to any limits) tells me how much fuel I can load.

But I don't like flight legs longer than 4 hours, I need to stand up and walk around. Makes it easy, literally math using my fingers. 

[N201MKTurbo]

11 hours ago, Hank said:

Do you have the windup clock in the yoke? Every time the moving (white) minute hand overlaps the nonmoving (red) minute hand, I switch tanks.

Having 2-1/2 hours' endurance in each tank keeps it interesting . . . .  

I keep it simpler than that.

If the minute hand is on the right side of the clock, I'm on the right tank, if the minute hand is on the left side, I'm on the left tank.

But then I have an A13A1 clock where I can start the minute hand at the start of the flight.

[FlyingDude]

17 minutes ago, N201MKTurbo said:

f the minute hand is on the right side of the clock, I'm on the right tank, if the minute hand is on the left side, I'm on the left tank.

I love this!!!

[slowflyin]

1 hour ago, N201MKTurbo said:

I keep it simpler than that.

If the minute hand is on the right side of the clock, I'm on the right tank, if the minute hand is on the left side, I'm on the left tank.

But then I have an A13A1 clock where I can start the minute hand at the start of the flight.

+1. My procedure as well.  Never have the “did I switch” moment.  

[N201MKTurbo]

41 minutes ago, FlyingDude said:

Guys, I hope I'm not jinxing myself with all this fuel talk and that I don't crash by fuel starvation and burn with the full fuel on the other tank 

If an engine quits, the first thing you do is switch tanks.

When I was on my ATP check ride in the gawd awful Seneca II, I was in the middle of a DME arc when the right engine quit. I immediately switched tanks and the engine came back to life. The examiner got a little pissed and said he wanted to see how I handled an engine failure. I said "I just showed you"

[FlyingDude]

4 minutes ago, N201MKTurbo said:

If an engine quits, the first thing you do is switch tanks.

To be pedantic, the first reflex should be "mixture full rich, boost pump on, switch tanks, carb heat".  No need to separate them or dwell on the sequence, if you accomplish all four in 100milliseconds.  You could have descended from 9000' for landing without cutting throttle and with your mixture setting left at the 100F LOP @9000', your mechanical pump might have failed, your tank might have dried up, and carb heat is a b**ch...  

Anyway, I love the "minutes hand of the clock matching the tank to be used" idea, but I don't have a mechanical clock.  I use the counter/timer on G 345 for IFR things. I might get a 1cm diameter clock and Velcro that next to the placard

 

[Ragsf15e]

1 hour ago, FlyingDude said:

Well, when I'm flying all by myself with no luggage and just the mains full, in winter time, I lean to peak (-10 / 20F for buffer) to warm up the cabin. That gives me 7.3 gph. On MTOW, peak gives me 9gph. When it's hot out, I go 100F ROP, to keep cylinders under 380F, which gives me 10.5gph. Climbs always full rich, at 14 gph. Your rule of thumb is cool for a situation check, but not good for precise planning.

In 2007 I flew a TB 10 from LILE to Sicily. Stopped overnight at Figari, Corsica and followed the coast. Airports on route, past the first hour or so, were either closed due to easter Monday or the airport was open but fbo was closed. You can't self serve in Italy. I think you are allowed in France but they always stopped by and fueled for me... So when I got to Reggio Calabria (tip of the boot, closest airport to my friend's house in Messina on the NE corner of the island), I had 40 min fuel left (topped off and back calculated). Legal, yes. Could have landed prior or diverted? Yes. Scared? Da hell. Especially given my 150 or so hours back then. So now, I'm just happy trying to be precise and trying to eliminate potential pitfalls

Slight hijack... if you’re really 10-20f lean of peak (just barely past peak), you should see cylinders cooler than 100 rop.  Mine are all at least 30 deg cooler.  Are you sure you’re getting just past peak on all cylinders?

Also, have you tried target egt in the climb instead of full rich?  Works much better and is pretty easy to execute.

Both of the above require knowing all 4 egts.  Do you have an engine monitor that shows all or just one?

[FlyingDude]

@Ragsf15e

"if you’re really 10-20f lean of peak (just barely past peak), you should see cylinders cooler than 100 rop."

Why?  If I'm dwindling around peak with EGT 100F warmer than 100ROP, why should the cylinders be cooler?  Isn't all that extra gas in the rich setting supposed to further cool the cylinders?  I'll measure that specifically next time.  Now I don't recall the comparison.  But I'm curious about your reasoning...

I have JPI700.  CHT and EGT on all cylinders are pretty much balanced, except for Cyl4 running a bit warmer, because the oil cooler is stuck on its back.

I read the Lycoming IO360-A1A manual and I recall full rich for take-offs and all climb situations.  Same in '67E POH.  It mentions leaning for run-up, take off and climb in hot temps or high elevations.  In those cases, yeah, I've done that.  But, it's not my general rule.  

Edited February 18, 2021 by FlyingDude