Primarily for general aviation discussion, but other aviation topics are also welcome.
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#1778468
Crash one wrote:No doubt a conversion would involve skimming a few millimetres off the cylinder head or fitting longer pistons, all of which will need gold plating at vast expense, with reams of even more expensive paperwork and carried out by the highest qualified rocket scientists in the land, before the crazy notion will stand a chance of nearly being successful .

Don't you mean somehow adding a bit to the cylinder head or shorter pistons?

Humour aside, I often wonder why engines that absolutely must have 100LL are still being installed in brand new aircraft. I can't see leaded fuel still being available in two or three decades time.
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By Paul_Sengupta
FLYER Club Member  FLYER Club Member
#1778503
terrybarr wrote:Don't you mean somehow adding a bit to the cylinder head or shorter pistons?


Not to convert it into a diesel, no...

terrybarr wrote:Humour aside, I often wonder why engines that absolutely must have 100LL are still being installed in brand new aircraft. I can't see leaded fuel still being available in two or three decades time.


They're not, really. They're being produced for the octane rating available in fuel these days. Most aero engines have long since had hardened valve seats, so the lead is irrelevant. It's just an octane booster. As soon as someone comes up with a 100UL which is universally accepted as a 100LL replacement, it'll be able to be used in pretty much all existing aeroplanes. No one's going to design an engine for mogas, and in most of GA-land, they don't know of the existence of UL91. So rather than invent a new avgas, they make engines which are able to use what's available. Which is 100LL, 80/87 having long since been forgotten.

If you wanted to use lower octane fuel and maintain the same power, you'd have to either increase the engine capacity or increase the RPM. You could have a complete redesign of engine with a greater number of smaller cylinders which would allow high compressions with low octane fuel, but that's a big risk in engine design. Many have tried, many have fallen by the wayside. Rotax is one of the few who have succeeded in a small cylinder high RPM engine being acceptable to the masses but they are only for low-ish power engines at the moment.
#1778564
terrybarr wrote:Humour aside, I often wonder why engines that absolutely must have 100LL are still being installed in brand new aircraft. I can't see leaded fuel still being available in two or three decades time.


What is the situation across the pond ?
If 100LL is going to be available for the foreseeable future then as a substantial market that is where these engines are targeted for.
By riverrock
FLYER Club Member  FLYER Club Member
#1778568
oldbiggincfi wrote:What is the situation across the pond ?
If 100LL is going to be available for the foreseeable future then as a substantial market that is where these engines are targeted for.

The UK is the only producer of TEL in the world, although I don't know how much effort it would take to bring a plant in USA back online again.
The vast majority of 100LL is consumed in the USA. The FAA are sponsoring research into alternatives but so far none of the options have stacked up: https://www.faa.gov/news/fact_sheets/ne ... wsId=14754
There is currently no suggestion that 100LL will be phased out before alternatives can be found.
#1778575
However, the current effort is to provide a lead free fuel that can be used by every piston aircraft. It's also possible that (generally the higher pressure and turbo) aircraft could run with substitute non-lead additives. That wouldn't be ideal, it would require some managing, but it simplifies the horrendously complex ask of the current effort. IMO AFAIK
But feel free to post that you don't want the hassle, you can't be bothered, there isn't enough poison to make a difference, or you spent money recently, it's not fair and why you and you should be compensated...
I DON'T think it's an easy problem or that it's OK to shaft people who are affected badly by this. But I do think it's worthwhile correcting an historical anomaly that led (lead - geddit) us to be still using leaded fuel in 2020 when it was removed for cars [edit]30[/edit] years ago.

And don't mention carb icing!
Last edited by neilmurg on Tue Jun 23, 2020 9:09 pm, edited 1 time in total.
By johnm
FLYER Club Member  FLYER Club Member
#1778592
Bathman wrote:What I can't understand bis why certified aircraft and engine manufacturers are building aircraft that are not capable of running on mogas with say 10% ethanol. Look at the pipers pilot 100 and Cessna's skycatcher.


For many certified aircraft the weather and atmospheric conditions they fly in make this dodgy. Diesels using Jet A1 are a better option.
#1778637
riverrock wrote:..
Could your electric motor be driven by a RAT? ..


<usual further drift :oops: >

.. of which the finest are made in Gloucestershire, of course :)

https://www.dowtyheritage.org.uk/conten ... ir-turbine

</>
riverrock liked this
#1778657
kanga wrote:
riverrock wrote:..
Could your electric motor be driven by a RAT? ..


<usual further drift :oops: >

.. of which the finest are made in Gloucestershire, of course :)

https://www.dowtyheritage.org.uk/conten ... ir-turbine

</>


Joking aside, I definitely think that burning dead trees and dinosaurs is a bit “old hat”. In the first place we are running out of them, they are messy, it can’t be used for any other form of power, unless you convert it to electricity.
All any aircraft needs at the moment is an airflow from front to back, whether it’s from a prop or turbine or a can of compressed air is irrelevant.
There should be far more research being done on electric motors/batteries/ generators.
Problem is there is too much money tied up in the oil/fuel industry that would suddenly be worthless, which won’t go down well with those involved!!
By riverrock
FLYER Club Member  FLYER Club Member
#1778665
There are millions of pounds, Euros and Dollars researching batteries. Electric motors are fairly light and efficient - its energy storage that is the issue.

Maybe we could attach a reservoir in a tank on top of our aircraft. When we want to accelerate we let out some water to drive a turbine. The electricity produced can drive the prop.
Fill-up is easy (and hose would do) and it would be non polluting.
Anyone up for a hydroelectric aircraft?
#1778674
Paul_Sengupta wrote:
terrybarr wrote:Don't you mean somehow adding a bit to the cylinder head or shorter pistons?


Not to convert it into a diesel, no...

terrybarr wrote:Humour aside, I often wonder why engines that absolutely must have 100LL are still being installed in brand new aircraft. I can't see leaded fuel still being available in two or three decades time.


They're not, really. They're being produced for the octane rating available in fuel these days. Most aero engines have long since had hardened valve seats, so the lead is irrelevant. It's just an octane booster. As soon as someone comes up with a 100UL which is universally accepted as a 100LL replacement, it'll be able to be used in pretty much all existing aeroplanes. No one's going to design an engine for mogas, and in most of GA-land, they don't know of the existence of UL91. So rather than invent a new avgas, they make engines which are able to use what's available. Which is 100LL, 80/87 having long since been forgotten.

If you wanted to use lower octane fuel and maintain the same power, you'd have to either increase the engine capacity or increase the RPM. You could have a complete redesign of engine with a greater number of smaller cylinders which would allow high compressions with low octane fuel, but that's a big risk in engine design. Many have tried, many have fallen by the wayside. Rotax is one of the few who have succeeded in a small cylinder high RPM engine being acceptable to the masses but they are only for low-ish power engines at the moment.

Sorry, I thought that you were talking about modifying existing engines to run on 91UL.
As you say, TEL is just there to increase the octane rating. I vaguely remember reading in my youth that it was possible to produce high octane fuels without the addition of the TEL but that using TEL allowed the production of more high octane fuel from a given amount of crude.

I wonder what the fuel spec for Formula 1 is these days? At some point in F1 history there was a meeting to decide on the regulations for the latest version of F2. One of the proposed rules was for pump fuel to be used. A guy by the name of Chapman stuck his hand up and asked 'Which pump?'. The rule was changed from pump fuel to Avgas.
Before this the engine designer s main job was to meke the engine stay together. The fuel chemist provided the horsepower.
#1778676
terrybarr wrote: A guy by the name of Chapman stuck his hand up and asked 'Which pump?'. The rule was changed from pump fuel to Avgas.


That's because like me , ending up landing in places which were too small to get out with the on board fuel load .
His Seneca and my Aztec and others became flying bowsers .
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