Thats good to hear. I fly over the gulf alot so another good reason for altitude! Skip I just re read your message and the miles per gallon is a good start...didnt realize It was available. Do you have a fuel flow gage you would recommend?

Randy,

Here's the link for Shadin and its key features as you scroll down the page.

http://www.shadin.com/products/fuelflow/digiflo.html

I have a JPI 760 connected to my GNS 480 which, between the two of them, provide all the fuel information that a person could want. The JPI will "alarm" (flash) when your overall predicted fuel reserve drops below a pilot selectable amount, in my case an hours worth of gas. It doesn't alarm when I HAVE only an hour's left, it alarms when, based on the fuel on board and my GPS flight plan, it predicts that I will have an hour's worth of fuel left at the destination. In some cases (bad winds) that might be as soon as I level in cruise, so I get plenty of warning.

For tank switching, I use an old school solution. I take off on the mains. When I switch to my tip or aux tanks, I note the amount of fuel on board, subtract 28 gallons (for a bit of fudge factor and write (for example) "TIPS OFF 88" on a post it note that I put right under the JPI. When the JPI says I have 88 gallons remaining, I switch. Works fine.

If it's going to be a max range effort, then I'll burn off all 30 gallons before switching, and warn my pax that there might be a stumble or two.

Jay

By the way, the fuel guages frrom Aerospace Logic Flash when empty. At night it can be a little annoying.

Tom. Can you not turn the flashing empty tank off? That would be annoying if you have the 6 tank model for the tip tanks
as most of time the tips are empty.

Gary

Dear Randy,

Some of the more experienced Comanche pilots I know have run tanks dry on carbureted Comanches (not recommended on Fuel Injected Comanches). I have run tanks dry a few times for the purposes of having the tank be empty when on the ground and ready to remove for replacement. It is not a big deal and I can say that upon landing there wasn't a teaspoon of fuel left in the tank. Ideally, you don't want the engine to quit (can you spell sudden cooling?). The procedure is while at a safe altitude, to know about when it will be empty based on calculated time to empty and have the co-pilot watch the fuel pressure guage. About five seconds before the engine quits, the pressure will drop and you better switch immediately when that happens or the engine will quit. Not complicated, but someone has to be watching the guage in a dedicated manner. Not the pilot during flight. Never tried to run a tank dry while on the ground. Just drain it.

I guess I'm not understanding your question about power settings. If you have a fuel flow type meter and it is hooked to the GPS, then most of them will tell you MPG. If you want to know what is the most economical engine setting to run, just play with the engine setting while watching the MPG on the fuel meter. It will change as you change the power settings and airspeeds. Look for the max MPG or whatever criteria you are wanting.

I use JPI engine analyzers with fuel flow. I'm not sure what to say about recommendations though. While doing the installation, I usually curse JPI about every minute or so. Something about them is a huge pain to install. As a pilot, after all the installation is done, I really like to way it works. Communicating with their factory can be extremely frustrating if you run into any kind of problem. For example, don't try to call them on a Friday. They all go home some time around mid morning on Friday. Be prepared to hold a looooooong time when contacting them. When the instrument is in the panel and working, I forget all that other stuff.

Sincerely,
Skip Dykema

Hi Guys, Here's my two cents. 40 years ago my first Comanche, a '62 250 with 4 tanks, was always run to "tanks dry" on long runs just like the book said to do. Your right the engine does not sputter it just quits! You need to pull the power back to idle switch tanks and turn on the electric pumps. The engine is still windmilling and catches quickly. (If you don't pull the power back the prop will surge up and down as it has gone flat trying to maintain RPM when the power stopped.) You'll usually be 100 feet higher once the engine starts as you just can't help pulling back a bit during the tank switch, the whole thing takes 5 to 10 seconds. I normally took off on the left main switched to both aux tanks at 2000ft and climb speed of 140mph. Aux tanks usually went to 2hrs 20-30mins. switched back to left main and ran to dry usually about the 5 hour mark where the right main was sellected with a planed landing at 2 hours or less which gave a 30 minute reserve. (When you know the tank is empty you won't switch back to it in an emergency).------This all worked well as long as we only had Comanche drivers aboard. However. with regular passengers the pucker factor was high amongst the guests when the fire went out! The solution came with the installation of a fuel pressure switch wired to an amber light placed on the upper left side of the panel. The light came on a good 30 to 40 seconds before "All Quiet" and gave plenty of time to switch tanks. As I recall it didn't cost $100 to have the shop put it in. N6659P only has 60 gallons so I never plan more than 4 hour jumps. (In reality my bladder/butt range is no more than 3 hours so running to dry is not needed anymore). Hope this gives some food for thought. Ray B

Wow. Ray thanks for the great history lesson...and a superbly simple solution for a low level warning.

Gotta ask:
What model is your fuel pressure sensor, where does it measure pressure in the system, and is it preset or did you set it to alarm at a particular pressure?

Skip I also appreciate your higher tech advice. From all a wonderful response to my question. It amazes me how knowledgable and helpful the members of ICS are..THANK YOU.

Randy/Tom... the Shadin, if connected to a GPS will give you MPG... which would be your "best throttle setting"
Jim

I removed My engine/fuel engine cluster and installed a JPI 930 in it's place. It is coupled with my Gamin 530 that has a fuel planning page that computes fuel required, reserve, endurance and several other things. The 930 allows you to view fuel quantity in all 4 tanks on the main page. When a tank goes to zero a red message flashes on the display that tells you which tank is empty. I burn my AUX tanks to zero before I switch and I have never run it completely empty. Usually there is about a gallon left in the tank. Over all the JPI is usually within 5 gallons of actual fuel. There is a calibration process that you can continually adjust. I only adjusted mine a couple of times and left it alone. Also if fuel press goes below .5 PSi it flashes fuel pressure low. I am very happy that I made this upgrade.

Mark,

Nice to hear about someone with the new 930. On the fuel did you mean it is within 5 gallons or 0.5 gallons? I'd be interested in the calibration process. If I have it right - the 930 can replace all the cluster gauges - and that puts it somewhere in the future for us. The shadin we have today and all of its predecessors since 1979 have gotten the fuel to within 0.1 to 0.2 gallon over the 4 to 11 tanks we have/have had in use.

On other 930 functions, would you start a new thread and share what you've experienced? I think several parties might be interested.

Pat,
L
I Meant 5 gallons of total fuel in all of the tanks. But after thinking about it I believe it is a little more accurate than that. If I am not mistaken this uses a Shadin system. I feel sure that I could get it more accurate. I need to go through the calibration again. I always have more fuel in the tanks than what the JPI says. Better this way than vice versa. It is more accurate on a long cruise flight rather than a boring holes flight. It comes with what they call a K factor. This can be adjusted through an in flight procedure of going to 8000 feet and recording temperature, pressure altitude and % HP and comparing to the Charts in POH. It comes with a math formula to come up with the new K factor. I am going to have to read through it again as I am going from memory. I will do that on a 930 thread. With twin you would need the 960.I will say that the initial install was not smooth. Some of the issues were a bad fuel flow transducer, unit for fuel injected instead of carb. As someone has already posted ,JPI is not very customer service oriented. With that being said I love the system. It is also very useful for maintenance. I had a Mag failure at altitude ( checked normal on the ground) a few months ago and my mechanic was able to down load the data with a thumb drive put it on the computer and diagnose the problem. It records what your engine is doing every 3 seconds; temperatures, pressures, and a whole bunch of stuff. It also is a good log book as it keeps a running tally of all your flights. Hope this helps. Be glad to provide more info! But I love it overall!