Mogas STC

[animalmover]

I hate to beat a dead horse but exactly why can't we have this? I searched this site and either couldn't find it or was looking in the wrong place.

Thanks for the responses in advance.

[FloridaMan]

I read somewhere that it was due to vapor lock issues with the fuel system. 

[Mooneymite]

Low wing aircraft tend to have issues with vapor-lock. Flying your Mooney inverted will avoid this issue. :-)

[Steve65E-NC]

Seems like there are enough Mooneys, Cherokees, Bellancas, Beachcraft etc out there for someone to solve this problem with a specialized, full time, auxiliary fuel pump.  If everyone so effected threw in $5.00 I bet it would be more than enough to solve the problem and get STCs developed for all the affected aircraft.  Maybe someone like AOPA would get involved to organize the effort. I think the time is running short.  

[Riq]

My pa28-150 has a mogas stc, and luckily I have a local station with no ethanol. It has saved a bunch of cabbage on that training bird, plus the plugs are much cleaner...my wife the student isnt the best at ground ops.

 

The compression on my 360 seems low enough to not have an issue, but im not versed in the fuel system, ie diff in the cherokee and mooney.

 

If I didnt have a turbo Id give it a go in 1 tank. Mogas is 3$ diff a gallon here.

 

 

ok, just found this on cherokees with 160hp or greater.

The fuel system modification for PA-28's consists of minor fuel system modifications aft of the firewall and a totally redesigned fuel system forward of the firewall. The Piper installed electric pump is removed and replaced with a pair of redundant electric fuel pumps.

[FloridaMan]

Low wing aircraft tend to have issues with vapor-lock. Flying your Mooney inverted will avoid this issue. :-)

 

Mooneys don't like to fly upside down for very long  (angle of attack and no inverted oil system)

[KSMooniac]

Mostly a moot point these days because of that damn ethanol... it is poison to the fuel tank sealant and other materials in our vintage planes (and boats, cars, motorcycles, etc.).  Find 100% pure mogas is very difficult in most parts of the country.

 

You might try searching the web for Peterson or Petersen mogas STCs and read all about the history.  They tried to make it work in Mooneys and could not make it succeed.

[N601RX]

From Peterson's website

 

The Mooney and Comanche both experienced vapor lock problems when they were tested. We solved the vapor lock problem but could not overcome pneumatic lock. Pneumatic lock takes place when the fuel boils as it enters the carburetor. The engine then dies due to an over rich mixture. This is just the opposite of a vapor lock where the engine quits or runs poorly due to a lean mixture. The better an airplane performs, the more difficult it is to get it through the flight test program.

 

We do not have Auto Fuel STCs for engines using Bendix fuel injection because it failed our flight testing. Continental fuel injection did not have that problem and is therefore approved – I0-470-J or -K (225hp). The 260hp I0-470 and 285hp I0-520 are also approved. These last two require Anti Detonation Injection (ADI).

[nels]

In our cars today the fuel pump it submerged in the tank and there is a return line from the carb or injection back to the tank. All this help eliminate vapor lock. I would think if this method was employed in a plane the alcohol fuel might work ok???

[N201MKTurbo]

I once was checking the fuel and the sample was clear....

 

I went into the FBO office with the sample cup and asked the guy at the counter "what is this"? He looked at it and said "I don't know, where did you get it" I said "out of your 100LL pump"

 

It turns out that the gas company had delivered 89 octane mogas instead of 100LL. The funny thing is that 10 airplanes had topped off and I was the first one to notice...

 

I had a trip to make so i drained out all but 10 gallons and flew to the next airport...

 

The plane flew like it always did.

[carusoam]

Ovations have a return line, and are free from the LL requirement.

I believe high altitudes require the 100 part of the 100LL.

I have not seen 100 delivered to an airport. Would the price be any better without the LL?

Best regards,

-a-

[N601RX]

I once was checking the fuel and the sample was clear....

 

I went into the FBO office with the sample cup and asked the guy at the counter "what is this"? He looked at it and said "I don't know, where did you get it" I said "out of your 100LL pump"

 

It turns out that the gas company had delivered 89 octane mogas instead of 100LL. The funny thing is that 10 airplanes had topped off and I was the first one to notice...

 

I had a trip to make so i drained out all but 10 gallons and flew to the next airport...

 

The plane flew like it always did.

There is an AD for a similar incident at a airport in CA.  Its a strange AD and list certain tail numbers and anyone else who purchased fuel from the FBO during a certain time window.  If I remember correctly it required a mandatory engine teardown and inspection.

[Bennett]

As I recall, and it was quite a few years ago, Chevron delivered a "bad" batch of fuel to Rabbit Aviation at San Carlos Airport (CA). If was more than just an octane situation, and I don't believe it involved auto gas. Rabbit was able to track the airplanes they fueled over a two day period by charge slips, and Chevron did in fact pay for teardowns and inspection, and I seem to recall they replaced an engine of two. I think jet fuel somehow contaminated that particular batch of fuel that was sold as 100LL. I don't believe that any aircraft crashed as a result, and that several aircraft owners noticed an unusual color and smell when sumping before the next flight. I will check with Rabbit next week to see if anyone there recalls the details.

[N601RX]

I went back and looked it up.  It was 2 airports over a couple of weeks. The AD listed a 100 or so tail numbers. As Bennett said it was avgas with Jet A contamination.

 

That action requires teardown and analytical inspection for engines certified to operate on 91 or higher octane aviation gasoline (avgas), and differential compression test and examination of the oil filter for engines certified to operate on 80 octane avgas. That action was prompted by reports of reports of aviation gasoline (avgas) being contaminated by Jet A fuel. After investigation, the source of the contamination has been determined to be the refiner of the avgas. Through its distribution system, the refiner inadvertently caused Jet A fuel to be loaded into distribution tanks intended for avgas. Contaminated avgas from these distribution tanks was then shipped to local fuel distributors. The FAA has determined that aircraft with certain Textron Lycoming engines installed were fueled with this contaminated mixture between May 22 and June 2, 1994, at Sacramento Executive (SAC) airport, or between May 18 and June 2, 1994, at Sacramento Metro (SMF) airport. The list of U.S. registered aircraft specified in the applicability paragraph of this AD is based on investigation of fueling records secured from the two affected airports, which the FAA has determined to represent the population of affected engines. That condition, if not corrected, could result in detonation due to low octane, which can result in severe engine damage and subsequent failure.

[Steve65E-NC]

I think the octane and ethanol problems can be solved for a specialized aviation fuel.  I am more concerned about the morning we wake up and there is no more tetra-ethyl lead.  As I understand, the major problem in shifting from 100LL to a mogas equivalent 100 octance is the vapor problem.  If the fuel is still specially manufactured and colored and controlled for aircraft that does not bother me.  The only thing worse than high price fuel is no fuel at all.  Then every ramp becomes a scrap metal yard.   I understand that lead has a marginal, high temp,  lube function in our engines but I am pretty sure there are non-lead additives that can work around that.  Apparently from the above, this problem was solved for some Cherokees with redundant full-time fuel pumps.  It is past time to move ahead and solve it for the rest of the fleet.

 

Steve 65E-NC   

[Steve65E-NC]

If the solution requires something like double wall counterflow or closed loop (working fluid and radiator) cooling for some fuel distribution lines, that can be worked into the STC.

[nels]

I think the use of alcohol in fuel will increase the fuel consumption per power setting. it is somewhat of an octane improver due to its lack of energy relative to gas and it attacks dye cast parts in the system, attacks some rubber fuel lines and probably eats away at the sealant in the gas tanks.

Tetra ethyl lead has no competition when it comes to a octane improver. There is nothing even close! It is my understanding that it was removed from fuel to protect the catalytic converter not because it was killing anybody. As a result, compression ratios had to be lowered to accommodate the new low octane fuel and air pumps had to be added to the engine to supply air for combustion in the converter. The fuel system had to be enriched in order for unspent fuel to be introduced to the converter to be reburned so as to get the converter hot enough to do its job.

So,why not just leave the lead in the fuel? Or is that just too simple?

[N201MKTurbo]

The environmentalists think we are all going to die from lead poisoning and kill all the children too.

[jetdriven]

deleted, see next. 

[jetdriven]

Ovations have a return line, and are free from the LL requirement.

I believe high altitudes require the 100 part of the 100LL.

I have not seen 100 delivered to an airport. Would the price be any better without the LL?

Best regards,

-a-

 

The Bendix RSA fuel injection has no return line, any bubbles that pass the firewall must pass through the injectors. Continentals circulate fuel and have plenty of cool fuel available.

 

Also, the Reid Vapor Pressure of autofuel is much lower than 100LL, and this aggravates the vapor lock situation.  Ethanol in the motor gas makes the whole STC moot.

 

Turbo and high compression engines need 100 motor octane to prevent detonation.  I havent seen an STC for a high compression aircraft engine, except the IO-470K and the IO-520.  The Continental IO-520BA has one but only with water/methanol ADI injection, and that's an 8.5:1 compression engine. The IO-360 is the same 5.125" bore, but 8.7:1 compression.

[nels]

I don't know for sure if this is true but I have heard lead is not good in an engine running real low compression ratio, like 6:1. The Jacobs radial engines are very low compression and supposedly the lead deposits out in the combustion chamber and cylinder walls and ends up in the engine oil. Anybody know anything about this?

[carusoam]

Have you seen tiny lead balls in your lower spark plugs?

My O360 would collect a few each year. They got removed at each annual.

We are using LL. I can't imagine what it used to be like with regular L. A fair amount more than what is required of modern engine construction.

Best regards,

-a-

[Steve65E-NC]

It is my understanding, maybe incorrect,  that  100 octane can be produced without lead or ethanol.  So that leaves the vapor problem.  I am talking about a non-lead, specialized, aviation fuel.  

[N201MKTurbo]

100 octane aviation fuel (Green) has 6gm/Gal TEL

 

100LL aviation fuel (Blue) has 4gm/Gal TEL

 

The last premium mogas with lead had 0.1gm/Gal TEL

 

Anything they do to make unleaded AvGas will make it more expensive!

 

I would be willing to detune my engine by retarding the timing so it would work with a lower octane aviation fuel. This fuel would be 100LL without the lead which is about 95 octane (not exactly sure).

 

On another blog I stated this and everyone thought loosing some engine power was worse then death.

 

I would consider the continued economical operation of my airplane to be more important. Plus it would spur the development and acceptance of electronic ignition and fuel injection systems that would restore the performance with the lower octane fuel.

[nels]

Electronic, computer controlled injection and ignition will have to be initiated for sure along with retrofit systems for older planes.

I'm quit certain that 100 octane fuel with no lead will have a significant energy loss when compared to today's fuel. Possibly 20 percent or more with a higher price per gallon than we see now. Flying will get even more expensive with really no reduction in pollution. We will be putting more pounds per hour out in the atmosphere than we are now.

100 octane aviation fuel (Green) has 6gm/Gal TEL

 

100LL aviation fuel (Blue) has 4gm/Gal TEL

 

The last premium mogas with lead had 0.1gm/Gal TEL

 

Anything they do to make unleaded AvGas will make it more expensive!

 

I would be willing to detune my engine by retarding the timing so it would work with a lower octane aviation fuel. This fuel would be 100LL without the lead which is about 95 octane (not exactly sure).

 

On another blog I stated this and everyone thought loosing some engine power was worse then death.

 

I would consider the continued economical operation of my airplane to be more important. Plus it would spur the development and acceptance of electronic ignition and fuel injection systems that would restore the performance with the lower octane fuel.