M20C 48 gallon tanks usable fuel

[Raptor05121]

Going back to the OP's discussion, did Mooney actually cordon off more area in the wing in '64 for the extra 4 gallons (48/52) or did they just measure the useable fuel as less in my 63?

[carusoam]

More logic, less answers...

1) Since the tanks are made up of wing structure it is hard to add just a little more...?

Adjusting the pick-up tube a small amount would have a big effect.  I don't recall the actual change that caused this effect.  There were a whole bunch of small details updated in 1965 including the rectangular Windows...

 

2) When making turns in the traffic pattern...

Having fuel run away from the pick-up is the least of your worries.  Fuel running towards the lowered wing would occur only if you are not coordinated.  Not being coordinated in your turns at TPA is bad.

Verify when you are making turns you are sitting straight up in your seat.  Not leaning against the wall or your co-pilot.  If you are vertical in relation to your seat, you are coordinated, and your fuel is staying right where it was as if you were descending in a straight line.

fuel will run forwards when the nose is lowered.  That is away from the fuel pick-up.

Is that what we are saying?

 

Non-CFI knowledge, I'm only a PP...

Best regards,

-a-

[cnoe]

More logic, less answers...

1) Since the tanks are made up of wing structure it is hard to add just a little more...?

Adjusting the pick-up tube a small amount would have a big effect.  I don't recall the actual change that caused this effect.  There were a whole bunch of small details updated in 1965 including the rectangular Windows...

 

2) When making turns in the traffic pattern...

Having fuel run away from the pick-up is the least of your worries.  Fuel running towards the lowered wing would occur only if you are not coordinated.  Not being coordinated in your turns at TPA is bad.

Verify when you are making turns you are sitting straight up in your seat.  Not leaning against the wall or your co-pilot.  If you are vertical in relation to your seat, you are coordinated, and your fuel is staying right where it was as if you were descending in a straight line.

fuel will run forwards when the nose is lowered.  That is away from the fuel pick-up.

Is that what we are saying?

 

Non-CFI knowledge, I'm only a PP...

Best regards,

-a-

You crack me up! When are you finally going to get that (CFI, A&P, ATP, etc.) rating?!!

Despite your logic I still don't like the idea of banking in the pattern towards a seriously low tank. I guess we all have our irrational fears.

Sent from my iPad using Tapatalk

[Hank]

I think my Owners Manual suggests taking off and landing using a tank with at least 6 gals of fuel, but I won't swear to it.just another good reason to concentrate your reserve fuel in one tank!

[cnoe]

I think my Owners Manual suggests taking off and landing using a tank with at least 6 gals of fuel, but I won't swear to it.just another good reason to concentrate your reserve fuel in one tank!

Says 8 gal. in the J POH. Seems prudent.

Sent from my iPad using Tapatalk

[Hank]

11 minutes ago, cnoe said:

Says 8 gal. in the J POH. Seems prudent.

Sent from my iPad using Tapatalk

That's because you have lots of unusable fuel. In a C, it's ine half gallon per side unusable.

[cnoe]

In the E I partnered in we had no idea how much was usable 'cause prior to the tank job the fuel transfer ports were all plugged with sealant.

Sent from my iPad using Tapatalk

[Bryan1016]

I've run a tank dry on a the C model. Full power almost instantaneously with selector swap.

I don't do it anymore. My wife freaks.

Sent from my iPhone using Tapatalk

[Wildhorsesracing]

23 hours ago, Bryan1016 said:

I've run a tank dry on a the C model. Full power almost instantaneously with selector swap.

I don't do it anymore. My wife freaks.

Been there, done that.  My wife claims that's the only time she has seen my "Oh Sh*t!" face. Switched tanks, engine came back to life almost instantly, it was truly a non-event.

My '62 C with bladders has 27.2 gallons per side - YMMV.

[Bob_Belville]

14 minutes ago, Wildhorsesracing said:

Been there, done that.  My wife claims that's the only time she has seen my "Oh Sh*t!" face. Switched tanks, engine came back to life almost instantly, it was truly a non-event.

My '62 C with bladders has 27.2 gallons per side - YMMV.

Have you verified O&Ns numbers for your installation? When they calibrated my rebuilt fuel senders while installing the JPI 930 Twin Lakes Avionics told me they could get no more than 26 gal on either side. 

[Wildhorsesracing]

8 hours ago, Bob_Belville said:

Have you verified O&Ns numbers for your installation? When they calibrated my rebuilt fuel senders while installing the JPI 930 Twin Lakes Avionics told me they could get no more than 26 gal on either side. 

I didn't know how much they would hold until the incident when I ran one dry.  The only markings on my wing were "100/100LL only" and there was no mention of capacity in the logs when the bladders were installed in the 80's.  So running it dry was the 1st time I was able to find out what the capacity was.

FWIW - I always fly with full tanks and rarely try to fly more than 3 hrs without filling back up.

 

[cbarry]

With the vast number of useable airports across the U.S., I'm always bewildered by the absolute need to know useable fuel to the point we stretch the flight into minimum fuel territory.  I also doubt any pilot regardless of equipment on board can tell exactly the amount of fuel on board  or fuel remaining at any given moment (and those that think they can are likely the next ones we hear about landing off field from fuel exhaustion).  Why not simply use some of the old wise adages such as "fly on the top half of the tanks." This may mean landing more often but what's really the harm in that--you get more practice flying your bird in all phases of flight and possibly get to meet more fellow aviators along your way.  

[cnoe]

With the vast number of useable airports across the U.S., I'm always bewildered by the absolute need to know useable fuel to the point we stretch the flight into minimum fuel territory.  I also doubt any pilot regardless of equipment on board can tell exactly the amount of fuel on board  or fuel remaining at any given moment (and those that think they can are likely the next ones we hear about landing off field from fuel exhaustion).  Why not simply use some of the old wise adages such as "fly on the top half of the tanks." This may mean landing more often but what's really the harm in that--you get more practice flying your bird in all phases of flight and possibly get to meet more fellow aviators along your way.  

I'm all for being conservative with fuel margins... but I bought a Mooney for fast efficient transportation, not to waste time at rural airports topping off my half-full tanks. A typical trip may be flying the 594 nm to visit my nephew. It takes about 4 hours and burns about 40 gallons of fuel which leaves me 24 in the tanks upon landing. My fuel totalizer is usually accurate to within one gallon at fill-up and I've never once landed with less than one hour of fuel remaining (which is my absolute personal reserve minimum). I also time and record every tank switch while flying.

There's certainly nothing wrong with making short hops and meeting aviators but if that was my mission I'd have likely bought a C172.

Sent from my iPad using Tapatalk

[gsxrpilot]

In complete agreement with Chuck. It would be one thing if I were a 20 hour per year renter, always flying a different airplane every time. But as an owner flying well over 100 hours per year in the same airplane every time, and as the only pilot flying this particular airplane, I can be confident in my fuel burn and range.  I can accurately predict within half a gallon, how much each tank will accept after a long flight. Therefore I'm also confident to often use 90% of the fuel in the tanks, avoiding the time and fuel burned to land, top off, and climb back to altitude carrying all the extra weight.

I will admit that it took a couple of dozen long cross country flights to gain this confidence and to absolutely know the fuel burn/range. Now that I've sold the plane and acquired a new one, I've got to start all over.  On the flight to bring it home from Ohio to Texas, I could have gone non-stop, but rather stopped in Memphis to top off the tanks. Another 40 hours or so, and I'll learn this 252 and have the confidence to comfortably enjoy it's full range.

[DonMuncy]

Fuel management, like life, is based on odds. There is always the chance a tank could spring a leak and your calculations and FF would not be of any help. The odds of this happening are very very low. The odds of you running out of fuel if you only fly on the top half are very low. If you calculate and keep an hour of fuel in reserve, the odds are not quite that good, but still good. The whole question of how much risk you are willing to take falls on you. The FAA has decreed the limit of risk they will allow you to take is either 30 minutes or 45 minutes, but you are free to add onto that until you feel comfortable. So our discussions here should not be about what "we" think one should do, but just keep everyone aware of the risks, and give everyone good information to help them make their own decision about that risk.

[larryb]

My first plane was a Grumman Yankee with 22 gallons fuel. So any flight of any length resulted in less than 10 gallons remaining. And that never bothered me. Now that I have 64 gallons available I have never had less than 15 gallons remaining, and that made me a bit nervous. I do have an accurate totalizer and my gauges seem accurate as well. But for some reason, now that I start with a lot more, I want more on landing too. 

[StinkBug]

Oops, I did it again. Ran a tank out on purpose that is. This time I actually saw the fuel pressure needle drop to zero and switched tanks just before the motor cut out though. 

As for leaving a gallon in the tank or some such thing, the fuel gauges in my plane are a joke. In fact yesterday the empty tank still indicated a small amount of fuel which is not normal, but whatever. I do have a fuel totalizer, but like Pauls it's a little bit on the pessimistic side. Generally I just obey what it says knowing that I'll always have a little extra. Ultimately though if you start full, or with equal amounts, and you use the method outlined in the POH (run a tank dry while timing) you'll always have a good idea how much TIME you have. You don't necessarily know how many gallons you have, but knowing how much time you have is the more valuable number. 

When the first tank runs dry you also know exactly how much you've used and how much you have left and can do another double check on your burn numbers. Trying to switch with 1 gallon left (or was it 1.5, or 2?) doesn't give you that accuracy. If you have ultra precise instrumentation then ok, but I've yet to fly a plane myself that had gauges I'd trust with my life. 

[cnoe]

I've been reading the latest Nall Report that just came out and with regards to fuel-related accidents we're doing significantly better than years past. In the past two years of the study fuel management accidents have decreased 18% and 16% for non-commercial fixed-wing pilots. Most recently fuel management was cited in only 7% of all accidents (NCFW). If you toss out contamination and systems operation accidents the percentage drops to 4.28%.

It doesn't state the cause for improvement but it couldn't hurt that more and more planes have engine/fuel-flow monitors.

Sent from my iPad using Tapatalk

[carusoam]

Prediction for the future...

When you have your plane long enough...

It will have...

1) a decent engine monitor...

2) FF with a totalizer calibrated to the finest detail will be the norm...

3) accurate fuel level will be monitored by digital floats.  This will cover the 'what happens when a tank leaks or my FF sensor lies' argument.

4) These items will be integrated together with the GPS and programmed with audible alarms.  Fuel required to destination monitored continuously and compared to actual FL in the tanks.

 

You will know...

5) your useful fuel, and fuel burn rates, and fuel related procedures.

6) a type club or have other internet based resources that will make it much better than the days of old...  Go MS!

 

It is getting extremely difficult to accidently run out of fuel on an ordinary day.  Fortunately a PIC is still required to provide the safety of the flight.

Props to CNOE and AOPA's George for detailing the statistics of the latest Nall Report.  I blurted out (I was alone at home) the headline improvement didn't tell the whole story.  George (in the AOPA video) then filled in the details that the improvement did include the change in hours flown over the years.

Congratulations everybody on a job well done!

Let's try to maintain those improvements...

Best regards,

-a-

[Tcraft938]

Good information in this thread.  After a year with the 1963 D/C I got the nerve to try it yesterday on a long cross country.  7,500' and in an area with many airports I could make it to.  Left tank was getting low and my time calc confirmed it and I knew I had 22 gallons in the right.  Watching the digital fuel gauge read 2 gallons and start flashing and not swap tanks went against every fiber of my pilot being.  LOL  When it hit zero or shortly before the fuel pressure actually increased from the usual 4.5 to almost 5, but stayed steady.  My hand were at the ready and eyes on that FP gauge.  20 minutes after the fuel gauge said I was empty, the little bird is still soldering on like it's full.  So my mind starts thinking did fuel pressure increase because it's sucking air, no.  Is this stupid, what if there's dirt and debris from the tank sealant that now is getting sucked in and swapping tanks will still starve the engine?  At 24 minutes after the fuel gauge said I was empty the fuel pressure went from 5 to 4.5 where it normally is in cruise and stayed there steady. No stumbling of the engine, but of course my imagination thought maybe I was detecting something, but all gauges were steady and speed no change.  At 32 minutes past empty ATC had me  turn 20 degrees left and the FP momentarily went below 4 then right back to 4.5, then maybe one little change of sound.  That was enough for me, fuel pump on, retard throttle and swapped tanks, return throttle.  I landed 20 minutes later.  Looking in the left tank there was no fuel to see (first I had seen the bottom of the tank) and it took 22.6 gallons of fuel.  So that plus what the TCDS says of" 15lbs unusable" divided by 2 means I should add 1.25 gallons to that figure and the total is 23.85 gallons, which pretty darn close to the 24 gallon capacity.  Since I did not run it out, I likely could have use at least another 0.15 gallons before it quit.  

Learned a lot from it.  One I should have right then and there, started putting two gallons at a time in and see how accurate my measure stick is.  I also learned that my fuel gauge reports lower volume than actual (at least the left tank, I need to test right next).  However, don't get cocky and plan on that.  I flew comfortably for more than 30 minutes past the reported ZERO, so that is a nice reserve that hopefully never will use.  Even the Fuel Calculator (JPI) which monitors both tanks, said I had 3 gallons less than I really did.  Again, good to know and I would rather have it read a little lower than give false sense of security.  

The best/fun part was a buddy was flying with me (sort of) in his 180hp Citabria.  Similar engine and prop as the Mooney, but despite him leaving a half hour ahead of me, I still got on the ground and fueled up before he landed, and he burned seven more gallons to do the same trip.  :-)

[Hank]

1 hour ago, Tcraft938 said:

The best/fun part was a buddy was flying with me (sort of) in his 180hp Citabria.  Similar engine and prop as the Mooney, but despite him leaving a half hour ahead of me, I still got on the ground and fueled up before he landed, and he burned seven more gallons to do the same trip.  :-)

Ain't that great???

1 hour ago, Tcraft938 said:

. . . what if there's dirt and debris from the tank sealant that now is getting sucked in and swapping tanks will still starve the engine? 

If you've ever flown in turbulence, the "crud" you are worried about has been shaken off the bottom of your tanks and burned . . . . Especially if your selected tank was less than half full at the time. It doesn't magically wait until the last inch of fuel remains to leap up and into the fuel port.

[Tcraft938]

40 minutes ago, Hank said:

Ain't that great???

If you've ever flown in turbulence, the "crud" you are worried about has been shaken off the bottom of your tanks and burned . . . . Especially if your selected tank was less than half full at the time. It doesn't magically wait until the last inch of fuel remains to leap up and into the fuel port.

Hank, good point and very logical.  However, you must not be aware that I am apparently a close cousin to Murphy's law.  With my luck 57 years of "crud" will suddenly jam into the filter at once, or that is when the fuel selector handle decides to break off in my hand, etc.  Any rate, I did it, survived and it wasn't bad.  Albeit, I did not let the engine stumble, but based on the fuel put in, I'm betting I was very close.

[RobertGary1]

Remember that if there are any issues with your fuel selector seal and you run a tank dry you could continue to suck air into the fuel system after you select a full tank. 
 

-Robert 

[gsxrpilot]

Great job @Tcraft938! Where this has real practical value is on a long cross country. It's, of course, good to have reserve that you don't ever go below. Let's say 10 gal. You'll always plan to land with at least 10 gal still in the tank as an example.  I'd much rather land with one tank empty and 10 gal in the other tank rather than land with 5 gal in each tank. 

If I'm on a cross country where I want the range, I'll climb to cruise altitude on the first tank. Then after leveling off and setting power, I'll switch tanks and run it until dry. Then switch back for the remainder of the flight.

[Skates97]

2 hours ago, gsxrpilot said:

Great job @Tcraft938! Where this has real practical value is on a long cross country. It's, of course, good to have reserve that you don't ever go below. Let's say 10 gal. You'll always plan to land with at least 10 gal still in the tank as an example.  I'd much rather land with one tank empty and 10 gal in the other tank rather than land with 5 gal in each tank. 

If I'm on a cross country where I want the range, I'll climb to cruise altitude on the first tank. Then after leveling off and setting power, I'll switch tanks and run it until dry. Then switch back for the remainder of the flight.

This is my procedure exactly for long cross countries. Did it just last week going to Salt Lake from SoCal and back and a few weeks before that going to Salt Lake and then Phoenix. 

Just as a data point for @Tcraft938, with the carburetor you don't have to turn the fuel pump on and retard the throttle. You can watch the fuel pressure and when it is empty it will steadily and smoothly go to zero. If you switch tanks before it gets to zero the engine never skips a beat because there is still fuel in the carburetor. If you have a fuel flow meter you will see it momentarily increase after you switch tanks but then it will come back to where it was. If you don't catch it before the engine stumbles just switch tanks and because the prop is still windmilling and the plugs are still firing as soon as it has fuel/air mixture again it starts right back up. It really is no big deal and ensures all your fuel in one tank as Paul said.

One thing I always check both before flight and during flight is to run my finger around in the cup for the selector to make sure nothing has fallen in there that could jam it when I go to switch tanks.