Primarily for general aviation discussion, but other aviation topics are also welcome.
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By riverrock
FLYER Club Member  FLYER Club Member
#1777347
Generally, the higher the compression, the more restrictive the fuel.

I see there is spec for 100VLL fuel which is allowed where LL is allowed (19% less lead than LL). I've never seen that for sale? Certified in 2011 apparently http://www.aero-news.net/index.cfm?do=m ... fc46644a58
From what I hear, VLL meets the spec for LL (as LL specifies a maximum amount of lead and the new standard specifies a lower maximum) so what we are getting sold and are using may already be meeting the VLL spec?

On health, the amount of lead put into the atmosphere used by aviation is tiny compared to what used to be put out by cars, but aviation is now the largest source of TEL in the atmosphere.
The removal of TEL from cars, for the entire US population, during and after the TEL phaseout, the mean blood lead level dropped from 16 μg/dL in 1976 to only 3 μg/dL in 1991, with "elevated" levels said to be above 10 μg/dL.
There have been measured health benefits (average IQ increase across the world) attributed to this.
There has been measurement of lead levels in kids near busy GA airfields and they show a higher level than those who don't live near busy GA airfields. However the numbers aren't particularly significant (although I can't find the studies mentioned by various people such as here: https://www.scientificamerican.com/arti ... tion-fuel/ ). I haven't seen studies of pilots.

I'd say that lower lead is a good thing in aviation fuel. However it really doesn't feel changing will make a significant enough difference to the world for it to be mandated.
#1777352
So how much would it cost the government to bail out all the affected owners at the market value of their aircraft for the good of the environment?

Only the ones with no alternative.

Can’t be that much in the scheme of things.
By johnm
FLYER Club Member  FLYER Club Member
#1777355
TLRippon wrote:So how much would it cost the government to bail out all the affected owners at the market value of their aircraft for the good of the environment?

Only the ones with no alternative.

Can’t be that much in the scheme of things.


It makes no measurable difference to the environment, better to leave well alone :-)
#1777416
skydriller wrote:
Sooty25 wrote: It just needs a bit of research and no resistance to certified modifications.

If someone gave me the option of converting a £50k 300hp engine to run on UL91, for say £5k with the compromise being 280hp, I'd do that rather than scrap the aeroplane. It may not even cost that if tweaking the timing is all that is required.


The trouble is, if you have a little think about that, reducing peak power output by 20hp would introduce all sorts of knock-on performance effects which you really do need to certify are actually acceptable for the overall aeroplane. Remember, for a 200hp Bulldog reduced to 180hp, that is a 10% power reduction...

Regards, SD..


I do get your point, but given the choice of a mod that reduced MTOW a little and maybe increased ground roll a bit, compared to scrapping the aeroplane, which would you pick? The chances are most engines out there are not producing their quoted output anyway and a cylinder refresh would recover everything lost by retarding a couple of degrees anyway.
By riverrock
FLYER Club Member  FLYER Club Member
#1777425
Sooty25 wrote:The chances are most engines out there are not producing their quoted output anyway and a cylinder refresh would recover everything lost by retarding a couple of degrees anyway.

The fixed timing is set to be best for full power, so I can't see how retarding the timing on a lower rated engine will recover any additional power.
You can improve efficiency at cruise with variable timing (
Dual E-Mags which have variable timing can improve efficiency by 10-15% ) but it isn't going to increase power.

Also why do you think that most engines aren't producing their full power? Power level is checked by doing a timed climb on all LAA aircraft at every permit renewal and is easily tracked (although I'm not sure if anyone has averaged the performance loss over flying hours or time) but generally most engines continue to produce most of their power until something goes wrong. Its been shown that they can still produce most of their power even with pretty poor compressions.
#1777454
@riverrock dual emags! Steady on, I can hear the wallets twitching already! :lol: But it would be a good start. Emags would be even better if they had knock sensors so they could advance and retard dynamically.

Retarding timing won't recover anything, it just stops the pre-detonation caused by using a lower octane fuel. My point about refreshing an engine was more the benefits of decoking, honing and re-ringing a 1000 hour engine, will always pull back a few lost horses.

Withdrawing TEL could be a damn good excuse for so many LAA maintained "lycsaurus" types to be dragged into this millenium. Improved ignition and fueling systems would solve the problem without scrapping.

Edge performance are probably already there for a number of engines with this kit

https://shop.edgeperformance.no/en/home/381-efi-ignition-for-lycomingcontinental.html

It just needs to become an LAA standard mod.
#1777826
Sooty25 wrote:Withdrawing TEL could be a damn good excuse for so many LAA maintained "lycsaurus" types to be dragged into this millenium. Improved ignition and fueling systems would solve the problem without scrapping.

Edge performance are probably already there for a number of engines with this kit

https://shop.edgeperformance.no/en/home/381-efi-ignition-for-lycomingcontinental.html

It just needs to become an LAA standard mod.


.....and be damned with all the certified owners.
#1777831
So how much would it cost the government to bail out all the affected owners at the market value of their aircraft for the good of the environment?


If it ever happens, rather than coughing up ££££gazillions in bail outs, they'll probably make high octane fuel unaffordable to the masses and it's use will decline naturally. :roll:
#1777882
Using Feb 2019 GINFO database, excluding MOGAS burners, there are around 3600 G REG aircraft that could run on UL91 and around 1700 that can only run on leaded AVGAS. The majority of the latter are those with Continental Engines.

I recall that for the time that I was flying certified Tecnam aircraft with ROTAX engines if they were run on UL91, or less than (I think) 25% AVGAS100LL in total, then they had a 100 hour inspection, compared to 50 hour.

Does anyone know if this applies only to ROTAX or if other/all certified engines have the same exception?
#1777889
TLRippon wrote:
Sooty25 wrote:Withdrawing TEL could be a damn good excuse for so many LAA maintained "lycsaurus" types to be dragged into this millenium. Improved ignition and fueling systems would solve the problem without scrapping.

Edge performance are probably already there for a number of engines with this kit

https://shop.edgeperformance.no/en/home/381-efi-ignition-for-lycomingcontinental.html

It just needs to become an LAA standard mod.


.....and be damned with all the certified owners.


Not at all, once there is a 100 or so LAA types flying reliably with converted engines, it will make justification for modifying certified aircraft more acceptable. We would be your "guinea pigs". :thumleft:
#1777933
Mick Elborn wrote:
Does anyone know if this applies only to ROTAX or if other/all certified engines have the same exception?


Only applies to Rotax engines. The service intervals are actually 100hrs, which are reduced to 50hrs on Avgas due to the build up of lead compounds in the oil which reduce the lubricity to the gearbox (which shares the same oil).

Your big bore Lyconentals don't have gearboxes and use different oils so not affected by this.

Andy
Mick Elborn liked this
#1777939
johnm wrote:There was never any evidence that TEL was a health risk
Palpably not true:
'Symptoms of acute high-level exposure include delirium, nightmares, irritability, and hallucinations. Chronic effects of tetraethyl lead include poor neurobehavioral scores in tests of manual dexterity, executive ability, and verbal memory. Treatment is mainly supportive.'
Deadly TEL === Big list of scientific articles on health effects of TEL
#1777960
skydriller wrote:
Sooty25 wrote: It just needs a bit of research and no resistance to certified modifications.

If someone gave me the option of converting a £50k 300hp engine to run on UL91, for say £5k with the compromise being 280hp, I'd do that rather than scrap the aeroplane. It may not even cost that if tweaking the timing is all that is required.


The trouble is, if you have a little think about that, reducing peak power output by 20hp would introduce all sorts of knock-on performance effects which you really do need to certify are actually acceptable for the overall aeroplane. Remember, for a 200hp Bulldog reduced to 180hp, that is a 10% power reduction...

Regards, SD..

Take out the spark plugs and throw away . Fit injectors in it's place. Fit a turbo . Find somewhere to make a glow . Bottom ends are big and strong .
The call this company for a new pistons.
https://newatlas.com/new-technology-tur ... esel/4695/
Fill with half price Jet Fuel ( available almost anywhere ) and knockeddy knock , off you go.
Crash one liked this
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