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But the hope dies last.
Which series ist your O-320?
Because if we manage to gather, say – ten owners with a O-320-D, it pays off.
Btw, I wrote Gomolzig (in german) and never got an answer. What I have read in a report is, that Gomolzig is in the state of compensation (do you say so in english? Similar to bankruptcy) with self – administration, so perhaps they are no longer interrested?

LOAN, Austria

I just had a call with Mr. Gomolzig himself. He confirmed that actually there is no mogas STC available for TB9 in combination with O-320 D2A and no qualification in progress or in planning. Meanwhile the cost of such a test-program is estimated with about 30000,- Euros.
There is no doubt that such tests will be successful and a STC will be achieved in any case.
Who might be interested to take part to start such a qualification? Gomolzig is willing to step in as soon as minimum 10 owners will join.

Please let me know.


Well I am, but meanwhile I also heard also other opinions about problems when actually running Lycomings in special situations, like high altitudes and heat.
To pay off, I think 10 participants is also minimum for cost sharing. On my TB9, it woult take at least three years, to have a return of investment.
meanwhile, I am rather trying to optimize fuel consumption and costs by taking leaning really serious, and looking out for fuel prices.

Three greens to all of you,
Axel der Aerotekt

LOAN, Austria

Thank you for your feedback. Of course you are right, pay of is a point. We calculate with 100 hrs per year and by that, pay off will be within 1 1/2 year.
We still use Mogas in a Piper 28-181 since many years. Sometimes we faced problems using the wrong Autofuel quality ( winter fuel!).
But at the end until now experience is good as well as during this hot summer period where we did more than 70 hrs with 30°C and higher.

Do you know about other interested owners?



I think, best would be a post in the TB forum.
I don´t know, if this topic has been treated there to a conclusion, but I am thoughtful about the fact, that nobody seems to discuss it anymore.

Axel der Aerotekt

LOAN, Austria

There are nowadays very few European pilots active on It is mostly just a small band of Americans.

The difficulty of getting owners together to fund any STC is that for every 100 persons interested only a few will actually stick their hands in their pocket when it comes to funding the project

And it gets more difficult still as the airframe value approaches the lower end of the market i.e. there will be a lot more interest in doing something for a say €300k aircraft than for a say €30k aircraft. As an example, various people have struggled to product avionics STCs for Robins – basically everything works against you: the typical hull value, the typical mission profile, the typical investment an owner has in the aircraft long-term. In this case you need to ask yourself what % of TB9 owners have mogas available at an airfield pump (jerrycans are not viable for a TB9; you would need a pickup truck and big muscles for hauling them).

Shoreham EGKA, United Kingdom

But STC´s are also affecting US-based airplanes, although prices in the US don´t seem to differ that much.
So perhaps US-citizens are not that much interrested in Mogas -STC´s, as Europeans. But on the other hand, they outrange the Europeans by number, so the final bunch, willing to take money in their hands, may not be so small? I don´t know. But I think it would be worth trying.

LOAN, Austria

AFAIK Mogas is not big in the USA, relative to Avgas pricing.

Also not as many TB9s were sold in the USA as one might expect. One could spend some time here adding them up…

And finally the airframe scrappage rate is highest in the TB9/TB10 population, relative to the TB20/21 population. This is partly due to any spar corrosion being uneconomical to repair.

I don’t know the relative TB airframe numbers but something like 1500-2000 TB airframes are still flying.

An EASA STC would not be directly useful in the USA.

I am not saying it is not worth doing, but it would be a good idea to get some numbers, and find a way to contact a good number of the TB9 owners.

Shoreham EGKA, United Kingdom

Peter wrote:

AFAIK Mogas is not big in the USA, relative to Avgas pricing.

Auto fuel STCs were a big thing in the 1980s and into the 90s, but with the advent of alcohol in US auto fuel the STCs became inapplicable. Also, in many US areas 100LL is only about 20% more expensive than premium auto fuel.

There are some areas of the US where non-alcohol auto fuel is still available. I recently took a 3500 km motorcycle trip, in a group, within the area where non-alcohol fuel is still available. Everybody in the group used it. The groups average fuel consumption decreased by what I’d estimate very conservatively to be at least 15-20%, and this was consistent over all the types of motorcycle in the group. This certainly reinforced that I wouldn’t use the auto fuel available near home in an aircraft.

Last Edited by Silvaire at 24 Sep 16:41

I find it difficult to see the real advantage of MOGAS as firstly there is only one brand of MOGAS available in the UK that is free of any ethanol. Ethanol is a real problem for some of the seals in the fuel system and recent experience with seals in a motorcycle fuel system leave me not wanting ethanol in the fuel tank of a machine I own unless unavoidable.

Rather than looking to put MOGAS in your aircraft I would suggest that there is an electronic ignition system that will shortly be certified in Europe ( it’s already certified in EASA land if you have an FAA type certificate) and the indications are that this can save about 1USG/ hr in normal operation and up to 20% furl burn above 10,000 ft.

With the advantages of better starting, smoother running and lower fuel consumption this would seem to offer far more advantages than trying to put cheap fuel that eats seals and is prone to vapour lock into your aircraft.

To this I should say that the previous owner of my aircraft used MOGAS, he would take off and land with AVGAS from the wing tanks and cruse on MOGAS that he put in the main tanks when you selected the MOGAS tank you got a 50 RPM drop and about 100F rise in EGT resulting in a 3-4 Kt reduction in cruise speed…………….. I did not like the whole idea and after I took delivery of the aircraft I burnt the main tank almost dry and the aircraft has never seen MOGAS since.

Last Edited by A_and_C at 30 Sep 06:05
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