91UL / UL91 / 96UL / UL96 / UL98 etc (merged thread)

If you’d ever tried to scale a small machine to a large machine you’d find the same design challenges as those who already have The UL 200 HP engine is a reasonable design but 3200 rpm is really too high for prop effiicency at 200 HP power level. in addition, as I understand it the UL engine power drops off pretty quickly with rpm – which is an important consideration for climb, assuming a fixed pitch prop and a wide speed range plane. You end up climbing with substantially limited power, well below 3200 rpm.

That’s why 8000 or whatever RVs are flying with 4 cylinder Lycomings, ones that can just about cope with Mogas and also make a 180 knot plane climb climb at over 1800 fpm on a fixed pitch prop.

Another direction to get useful GA level power with poor quality fuel is multiple engines, as per the Tecnam twin which does its best with 200 HP. Now you end up with eight cylinders, four carbs (at least for some of them), two constant speed props and so on, plus a pretty limited capability plane. There’s really no free lunch.

None of these aircraft are long rage tourer, or even certified for IFR.
Which engine is certified for CoA aircraft? Midwest, D motor or UL Power?
Still not in the range 230 to 300hp.
Engines don’t fly without an airframe.

Markus,

the problem is that travellers are not necessarily the customers who use most fuel. These are the flying schools and clubs with their usual airplanes with lower power engines.

In Europe, a lot of these schools who have invested in new material have gone either to Rotax powered airplanes such as Da20 Katana, Sport Cruiser, Tecnams and the likes for basic training and have equally bought Mogas STC’s for every plane they had it was available for. And there are many. Most of the typical spamcans can be modified to use Mogas, PA28, C172 and even some C182 have STCs for it. With the hours they make and the pricing difference one does not even need a calculator to figure out that without this, the price to just obtain a PPL would have gone even further up than it has. Who the hell would blame them trying to buy fuel at up to 1 € less per liter!

The same goes for a lot of owners who fly recreationally. I have several friends who fly either Rotax powered airplanes or who got Mogas STC’s for the very reason that it allows them to afford a plane they otherwise could not have.

I did talk to several producers of airplanes yesterday in particularly the Pipistrel guys as i wanted an answer regarding the engine swap. The answer was clear: Mogas. The IO390 for some reason is no longer on the road to Mogas, the IO540 they are going to use is certified and they will certify the airframe with it. Logically it can also then use UL91.

I have a lot of contacts with aeroclubs and AOPA people who also have the concern that many people today are critical of our kind of GA because we still use the politically uncorrect lead. So getting rid of that, no matter whether Mogas or UL91, will take this argument away.

And last but not least: UL91 will do away with a problem I only know too well in my O360… spark plug fouling. Seeing that many engines suffer from this and quite a lot of them actually can easily use UL91 I can not see any reason why they should not. Most of these engines were actually made for 80 to 90 octane fuel so they naturally will run better on Ul91.

However, you are totally right when you say that there is no solution so far for the 250hp plus class of airplanes. From my perspective, there’d better be. And I guess there will be. Actually, Lycoming might well think again whether not finally to modify their diesel offering for civil use, which, as I was told at the Aero, would be primarily a paper exercise, albeit an expensive one. It would be pretty suitable for quite a lot of airframes too.

I do remember vividly the oil crisis which took the big fuel guzzler cars off the road. The attitude then was the same as today in aviation: There will NEVER be a 3l/100 km car, there will NEVER be fuel without lead, there will never be…. well, we know that was wrong and it will be wrong here too. It has to be, or otherwise in 20 – 30 years this class of airplanes will be found in museums and there only. While the GA of that time will continue happily on the engines everyone now calls names. Centurion, SMA, Rotax are names which are here to stay, so is Austroengine and so are Lycoming and Conti. Conti has obviously gotten the Diesel message but drags its feet with UL91 approvals, Lycoming seems to be tending in the direction of UL91, in the end, it is a question of survival for them as well. If the eco lobby in the US bans Avgas, they better be ready. And who would be surprised if their now moderate reluctance to certify their engines will make space for a pretty hasty re-invention of their future?

Personally I can do with any way to make flying more affordable. And cheaper fuels are the most needed. Of course the tax lords will try to fleece us once again,so there will be a challenge to stop them for AOPA and even EASA.

This thread illustrates why European GA is in such a mess.

One group of pilots is happy to shaft another group, on the I am allright Jack! principle.

91UL is not going to penetrate the European market – even if it does well in small pockets of GA like perhaps Norway. This is because it isn’t economical for an airfield to carry two different but similar fuels. Even if it sold them 50/50 that means buying only half the volume of each, which means they pay more for it, and the differential was so small to start with so there is no point.

I really don’t get this. Exactly which groups are you talking about, and where do you put yourself in relation to these groups?

Sweden is very similar to Norway. They have managed to have 91/96 UL and 100LL together there for 30 years. 91/96 UL being made and distributed by Hjelmco. I too initially thought this would be an economical problem, but it really isn’t. It could have been if Shell with their highly inefficient distribution still were to serve the market. Right now Shell is out and Warter is in. With Warters method of distributing, straight from the refinery in anything from single barrels to bulk, there really is no limit for how small the delivery can be. Even so, distribution cost can hardly the bottleneck regarding price even today, because if it was, then why is 100LL cheaper in Norway than most other places in Europe? The whole perception that serving several fuels is costly is just a myth, there is nothing that can substantiate this. There are other factors than distribution cost that are to be blamed here. Also, to get one thing clear, the point of reducing the amount of 100LL is to reduce the usage of TEL, nothing else.

The little Rotax is actually a pretty good design if what you need is 80-100 HP and don’t mind a disposable engine that will be economically beyond repair at 2000 hrs, versus perhaps 8000 hours for a Lycoming.

This is wrong. A complete overhaul of a Rotax costs about 7-10 thousand Euro, the TBO is 2000 hours. It will last for at least 4000 hours or more, but I don’t think anyone has run for more than 5000 hours, they are still too new. For a certified Rotax, it is probably cheaper to just sell it at 1500 or so hours and get a new one though.

The UL 200 HP engine is a reasonable design but 3200 rpm is really too high for prop effiicency at 200 HP power level. in addition, as I understand it the UL engine power drops off pretty quickly with rpm – which is an important consideration for climb, assuming a fixed pitch prop and a wide speed range plane. You end up climbing with substantially limited power, well below 3200 rpm.

I agree, but the UL Power also weigh in at 108 kg compared with 150 for a 200 HP lycoming. The cowling can be made much more streamlined. It has FADEC. The benefit will be faster cruise at much lower consumption. And of course, you can run on mogas or UL91 An RV-8 are not exactly power constrained with 200 HP no matter how you look at it, and 42 kg less helps a lot as well. A CS prob would be much better, if you can find one that will accept 200 HP and 3200 rpm that is. A super light, super smooth RV-4 with the smaller UL 390iS and fixed pitch would perhaps be more fun. I’m building a RV-4 (amongst other things) and have not yet purchased an engine for that one (to be honest, I will much more likely put in a true and trusted Lyc 320/360 though).

The US tree huggers will never manage to ban avgas. The FAA will stop them. Eventually a “100UL” will be found, and it will spread all over the world.

Maybe, but in the mean time we have UL91 for 90% of us, and it will always be cheaper than 100UL if it should ever materialize.

I do remember vividly the oil crisis which took the big fuel guzzler cars off the road. The attitude then was the same as today in aviation: There will NEVER be a 3l/100 km car, there will NEVER be fuel without lead, there will never be…. well, we know that was wrong and it will be wrong here too. It has to be, or otherwise in 20 – 30 years this class of airplanes will be found in museums and there only.

This argument is a real problem for aviation engines because they are fighting a perception formed by cars, which are an entirely different application. We all know that car engines run almost always at low power settings, whereas aircraft engines runs at high power settings – which are already efficient. The real ‘efficiency problem’ is that aircraft go faster than cars and that a wing is a less energy efficient way to support a load than rolling friction. When you remind people of that they often agree (again!) and then later seem to come right back to the same incorrect perception. Aircraft engines are already pretty fuel efficient but they produce a lot of power, continuously, and thereby use a proportional amount of fuel.

I’d bet my retirement fund that in 20-30 years most of the 8000 RVs will be flying happily with their existing engines. Whether European politics can push private piston powered transportation aircraft out of Europe is another question, and I think the universal conversion of the European GA fleet to Mogas would be a good political move, including derating some engines. An even better political move would be to maintain the largest number of active aircraft by any means, with any engines. However, there will be no miraculous mass conversion to magic engines.

we have UL91 for 90% of us

Doesn’t get any more truthful by repeating it…

Peter,

The decline in GA is only partly due to fuel cost.

Not only fuel but general cost, of which fuel is a huge factor. I am one of those pilots who can just about afford to fly, but it is too important to me so I will sacrifice other interests in order to make it happen. Fuel is a big factor in this. My airplane can take 200 liters of fuel, so one single load of fuel could be up to €200 cheaper if I could use Mogas or can actually be up to €60 cheaper only if I can find UL91. For me that is a lot of money. Maybe for others not. But if the greenies get their way and really push up the fuel price to €5 a liter for “recreational fuels” such as Avgas, then that will be it for me unless I can change to Jet A1 where this can not be done that easily.

A lot of it is due to pilot demography, itself driven by younger people having other stuff to do.

A lot of our youngsters simply shy away when they first see the price of a PPL, then get indoctrinated by their schools and clubs that airplane ownership is a total no-no? Some of those club exponents are talking worse than the outer left politicians… Youngsters need a cost effective and attractive way to get their license and thereafter cost effective and attractive airplanes to fly with. I have in recent years gotten several people to become satisfied owners, ALL of them had to explain themselfs to their families and significant others to be allowed to do this and efficiency and cost saving was the first and most important deal breaker for them. Cost is EVERYTHING today.

There are plenty of people with money to do lots of GA flying but most of them are spending their money where they get a better return in terms of “fun”.

Well, there may be but they are NOT the people who get youngsters to fly and generate new pilots. On the opposite, some of them actually discourage youngsters from trying aviation because it is only for the “rich”. That perception is wrong, but it also has backing in politics, why else can we be shafted the way we are with fuel taxes and the likes?

The average private pilot needs a low cost and low maintenance airplane to be able to do the flying they want, not airplanes costing more than a house. For these people, fuel price is paramount. That is why Rotax is so successful as it uses Mogas, that is why Mogas STC’s are still very successful and that was why a lot of clubs went Diesel during the first Thielert hype, only to be shafted later when Thielert collapsed, creating a huge distrust in a technology which otherwise I am convinced would today be normal rather than exotic.

Aviation today is way too expensive and it is mostly so due to the elitist image it has as well as the perception that pilots are all money bags who have unlimited funds. That, Peter, is the biggest problem I come across all the time when people learn I fly and heaven behold even have the impertinence to own an airplane.

Turn it as you wish, but without fuel no airplane flies and a 30% difference between a niche product fuel and what is technologically possible today for a huge part of engines is a huge factor for many pilots who struggle to keep their currency. the cheaper the fuel the more they fly, the more expensive, the more drop out or fly their 12 hours minimum.

Silvaire,

This argument is a real problem for aviation engines because they are fighting a perception formed by cars, which are an entirely different application.

True. But the primary difference between aviation engines and car engines is that there has been a tremendous technological development in car engines following the 70ties while we still fly with airplane engines from before that time. The main reason is that airplane engine development is next to impossible to finance. No car owner would today accept an engine which needs “secret rituals” to start successfully, which uses no electronic ignition and which uses exactly the same amount of fuel a 50 year old car uses? There is no reason whatsoever that we still have to use manual mixture, which most pilots don’t use correctly anyhow, no reason why we have to work with mechanical ignition and need aftermarket mods to have a proper injection system. The only one is that the industry has stopped developing new products because a) they can get away with selling the old ones or at least think they can and b) the hurdle for new engines is so high nobody can or wants to pay for it.

When you remind people of that they often agree (again!) and then later seem to come right back to the same incorrect perception. Aircraft engines are already pretty fuel efficient but they produce a lot of power, continuously, and thereby use a proportional amount of fuel.

All true, yet I am convinced that would those engines be brought up to todays technical standards, there could be similar savings we had in the auto industry. When I remember our trusty VW Beetle with it’s 1300 cc engine, it burned 10 liters / 100 km and had about 35 hp with leaded fuel, todays 1300 cc engines burn half of that and get 70 hp out of it on unleaded fuel. We don’t need to re-invent physics but we need to bring those engines up to todays standards. The only ones who have done that, using a car engine base, is the Diesels, where the results per se are very promising. I don’t see any reason why the same could not be done with gasoline engines.

I think the universal conversion of the European GA fleet to Mogas would be a good political move, including derating some engines. An even better political move would be to maintain the largest number of active aircraft by any means, with any engines.

The universal conversion as far as possible is certainly a large goal. Even better would be a unleaded and cheaper fuel that most engines can use without even getting an STC. UL91 is such a fuel, even though it’s price is kept up artificially in some places it appears.

But again. Imagine we never had the 71 crisis in the first place, the auto industry would never have considered the cost intensive research and development they had to do as a consequence. Maybe it needs the ban of Avgas in order for developers to finally get their thumbs out of where the sun don’t shine and get to work on something a bit more up to date? Some people do need a shotgun to their head before they act. Only we’ve had it for years and nobody notices.