Investigation into mid-air engine failures yet to yield answers as pilots fear for their safety

[SSCBD]

https://www.msn.com/en-au/video/sport/mysterious-engine-fails-under-investigation/vp-BBNLAWl

 

[/url]Investigation into mid-air engine failures yet to yield answers as pilots fear for their safety

 

 

 

 

 

 

[Birdseye]

Odd but appropriate typo: "A series of engine failures are lead to be because of a change in aviation fuel in the Northern Territory ", as apparently it may be related to a reduction in lead content and an increase in aromatics in the fuel.

 

 

[Downunder]

So...let me get this....

 

Kids sniffing avgas had high lead levels........ The fuel mfg replaced some of the lead with aromatics to keep the govt off their backs (either pre-emptive or under pressure) but did not tell the users of the fuel that it will probably damage their engines......and then it turns out the kids now "love" the aromatics in the fuel.

 

The net result is premature failing of engines, putting lives at risk, with no reduction what so ever in the amount of sniffing going on......FFS...,!

 

 

[facthunter]

. Could well be a serious problem. They introduced OPAL fuel years ago which was allegedly based on avgas for general use. I think avgas was still 100LL but L is not that LOW, but the scarcity of people and users would hardly produce a lead problem in the environment up there. Isn't LL still the same here?.. If your engine's acting up get on the ground as soon as safely possible is good advice

 

Mogas contains aromatics and NO lead. and we have often "shandied" fuels without concern...Nev

 

 

[Birdseye]

The original text based article: 'Waiting for someone to get killed': No answers over mid-air engine failures

 

 

[facthunter]

Some may recall the kerfuffle with Avgas from the Mobil Refinery in Victoria. where some planes using Avgas never flew again due caustic causing corrosion to fuel system components. Avgas and avtur are highly regulated products and there should be no question of their formulation being suspect. In the 90's I saw some Pratt & Whitney ex cropduster use radials that had run on Mogas.. stripped for repair. Gum and crud everywhere. Perhaps oil not suitable but it put me off running mogas except with the 912 Rotax which recommends it.. Nev

 

 

[kaz3g]

I saw the cue bowl off a C65 that had run for tons on mogas. Not a pretty sight.

 

Kaz

 

 

[kaz3g]

That was carburettor bowl...bloody iPad.

 

 

[onetrack]

The basic problem with todays unleaded fuels is the oil companies are struggling to find a suitable valve-protecting ingredient that matches the superb valve and valve-seat protection ability of lead additives.

 

The car engines of today use high-tech valves and valve seat materials that are highly wear resistant, in the absence of valve-protection additives in todays unleaded crap fuels.

 

The aircraft engine manufacturers of today are lagging badly in keeping up with modern car engine technology.

 

The use of nitrided valve seats, sodium-filled valves, titanium alloys, and Inconel and Nimonic alloys, are all valve and valve-seat technologies that have been in use in heavy commercial vehicles and racing vehicles, for years, to provide superior performance.

 

These technologies involving superior valve and valve-seat materials could easily be utilised in aircraft engines running on MOGAS and Avgas, but the bean-counters always seem to have more sway in boardroom decisions, than the engineers.

 

 

[onetrack]

There are a number of Japanese automotive components suppliers, and at least one American company that I know of, who have designed, and are producing, vastly improved valve seats to raise the durability levels of these critical items.

 

These companies are utilising state-of-the-art powder metal, sintering and tungsten carbide matrix metals to produce valve seats of exceptional durability, whilst retaining relatively easy machining and modest cost of their valve seats.

 

In the high performance versions, solid lubricant particles are included in the metal matrix to aid in valve seat lubrication when poor-quality fuels such as our current ULP are being used.

 

This valve seat lubrication was previously carried out exceptionally well by the lead in petrol - in fact, I can recall the advertising from the 1950's, where the oil companies regularly produced breathless motoring ads, reporting on the outstanding valve-protection abilities of their latest type of lead additive.

 

It's about time the aircraft engine manufacturers stepped up to the plate, and started providing superior materials in valves and valve seats, that provides adequate durability over the range of less-than-stellar petroleum fuels we are being provided with.

 

Powder Metal Valve Seats

 

 

[Downunder]

In one sense, the aircraft mfg's didn't have to improve they valve wear technology BECAUSE of the lead.....

 

 

[facthunter]

TEL came in in the late 20's I'm sure the aero engine manufacturers are not using metals they did back there. They have been constantly striving to get the engines to 2400 hours without a "top", which would be an exceptional achievement. Low use of engines (sitting idle) has to be an issue. Car engines spend most of their time at low power settings, unlike aero engines that run with a steady 75% load generally and must be as light a safely possible. Very few manufacturers have succeeded at making a reliable up to 350 hp aero engine. Bear that in mind when criticizing the present ones. IF someone does better it will take the market which is relatively small and very litigious. We are still waiting. Nev

 

 

[Thruster88]

If lead is the protecter of valves, how do turbo diesels (dual cab utes) survive with amazing high specific output.

 

 

[onetrack]

Diesels normally use stellite or stellite-faced valves and valves seats, and alloy steel or sodium-cooled valves, which component materials withstand the additional, and longer heat output, of diesel engine combustion chambers and exhausts.

 

https://www.engineaustralia.com.au/sites/default/files/engine_seb/SB020abs.pdf

 

 

[Birdseye]

Very few manufacturers have succeeded at making a reliable up to 350 hp aero engine. Nev

Rolls Royce did quite well making engines in the 1000 to 2200hp range .... Not sure that tetraethlylead had much to do with the numbers of manufacturers building engines, I suspect it was more to do with the economics.

 

 

[Birdseye]

If lead is the protecter of valves, how do turbo diesels (dual cab utes) survive with amazing high specific output.

LPG also results in some incredibly long lasting motors that are internally very clean.

 

 

[Thruster88]

https://www.google.com.au/url?sa=t&source=web&rct=j&url=https://www.casa.gov.au/files/awb-85-024-issue-1-piston-engine-exhaust-valve-and-valve-guide-distress&ved=2ahUKEwjjnYuO0_LdAhVVFogKHcmTCfUQFjAAegQIARAB&usg=AOvVaw388Xh-XB7WJiJZyZdPvGKY

 

Awb-85-024 explains the problem, if lycoming is having trouble I wonder how others are getting on in the top end (NT).

 

 

[Mike Borgelt]

There was lead free Avgas available in Sweden some years ago. 93 octane I think. Just take the lead out of ordinary Avgas100LL. Never heard of any problems. The old 80/87 usually contained lead but did not have to if the feedstock met the octane rating. I've read that the "lead protects valves" is also a furphy.

 

 

[facthunter]

The RR military engines were not long life Engines. Very limited( about 2) airlines used them commercially as they were never able to be certified for Civil operations.. TEL enabled more power to be obtained at take off particularly from lighter engines and gave better fuel efficiency. Valve SEAT life was a secondary consideration. not the reason for using the additive. A lot of valve gear in those days was out in the open and had to be greased manually at short intervals. While that might appear crude the head was exposed to better cooling air flow without enclosed rocker boxes..

 

IF the valve seat is not making good contact with the head in the recess formed for it and maintaining an interference fit, it won't transfer the heat through it from the valve head. 500F is pretty hot, as a limiting head temp. I think from memeory 235 C was the limit on most radials I had experience with. That's 455 F which is a bit lower. but I reckon hot enough.. (especially with what we are running Jabs at). Nev

 

 

[Mike Borgelt]

Once again, with the lack of urgency, we see on display CASA's real concern for aviation safety. ZERO. The only concern for safety is the safety of their jobs and nobody will ever get fired or sanctioned for dereliction of duty at CASA.

 

 

[Mike Borgelt]

I know of glider towplanes have used a shandy of 25% avgas, rest unleaded and gone to 2000 hours before overhaul. O-540. Pretty severe service too.

 

 

[Thruster88]

Once again, with the lack of urgency, we see on display CASA's real concern for aviation safety. ZERO. The only concern for safety is the safety of their jobs and nobody will ever get fired or sanctioned for dereliction of duty at CASA.

What should casa be doing in this case which does not seem to have any clear cause, I'm sure the fuel and failed parts have all been tested for compliance.

 

 

[facthunter]

Since these failures are happening sometimes as low as 100 hours for a cylinder in service time an aware of what's normal prop pull through where it's safe to so do might be a good idea. I'm inclined to think it s a seating problem of some kind and as always is the case it will deteriorate rapidly if not detected and rectified..

 

The lead did help valve SEAT life. Gas vehicles always needed extra quality valves and seats in some instances. Later Falcons ran Inconel exhaust valves anyhow but harder seats would be installed if you did really high miles on gas. No lead fuel had a similar effect. Unhardened iron head motors wore the valve seats quite rapidly till you eventually ran out of the hydraulic lifters range and the valves unseated with resultant power loss..

 

Aircraft engines don't have the same operating environment as a car's engine does any fault will become a major one quickly.

 

Diesel valves don't reach the same temps a petrol or gas one does, it would appear probably mainly as they are more efficient thermodynamically. Nev

 

 

[Mike Borgelt]

What should casa be doing in this case which does not seem to have any clear cause, I'm sure the fuel and failed parts have all been tested for compliance.

Geez, the fuel formulation got changed (Going from 1% to 16% aromatics and reducing lead seems like a big change - the fuel might meet spec but was any testing done on real engines or just laboratory spec testing?) and they are having trouble. Just go back to the old formulation. If that doesn't fix it check out the source of the new valves and seats and test for material properties/manufacturing methods.

 

They were quick enough to ground aircraft for the Mobil avgas contamination issue and happy to screw over Jabiru on flawed evidence.

 

 

[Mike Borgelt]

More than you ever want to know about lead in Avgas and the replacement effort :

 

https://repository.tudelft.nl/islandora/object/uuid:d7c5a6f6-f49f-432b.../download

 

Here's a relevant part on the necessity for lead in avgas from Lars Hjelmberg - Hjelmco. Hjelmco have been supplying unleaded Avgas in Sweden for years. Page 113/114 of the report. Answers from Lars in quotes.

 

Appendix 1E Hjelmco

 

BRGDS Från: Ali Noormehr [mailto:[email protected]] Skickat: den 28 september 2015 02:08 Till: Lars Hjelmberg - Hjelmco Ämne: Re: HjelmCO.se HELLO, As known, the AVGAS 100LL is being viewed as a common fuel blends in the general aviation industry. Given the fact that a large portion of lead emission is from the general aviation, the EPA is urging the involved organization such as operators, refiners, manufacturers to stop using 100LL in the near future. To do this, the 100UL type has been introduced as the best alternative for 100LL. My questions are as following: - - TEL is being viewed as a critical component in the 100LL composition in order to avoid aircraft engineknock. Given the fact that the 100UL contains no TEL, is this fuel type still recommended for use in the general aviation?

 

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=10&ved=2ahUKEwjt97_4h_PdAhUYQd4KHQ6tDKYQFjAJegQICRAC&url=https%3A%2F%2Frepository.tudelft.nl%2Fislandora%2Fobject%2Fuuid%3Ad7c5a6f6-f49f-432b-b489-c4796bb454f4%2Fdatastream%2FOBJ%2Fdownload&usg=AOvVaw0nTCBjE8gV6ykI2TfThR71

 

" No-one knows - there is still no production standard for an 100 UL AVGAS – so no-one knows the outcome." - - Study shows that an increase in the aromatic level is the only way to replace the TEL. Is that true??

 

" No"

 

Could you tell me more about the aromatics? I know only the Toluene as aromatic, are there more aromatic components in the fuel composition?

 

"There are several aromatics that may increase octane-numbers. Some of them can not be used at all - others cannot be used in desired amount. Aromatics cause fuel to burn slower, has lower energy content and cause deposits. "

 

- - Usage of TEL in the fuel composition is beneficial for some of the engine-parts such as enginevalve.

 

"Not correct."

 

The question arises, are there any other engine-parts that could be affected as result of TEL absence?

 

"TEL is not needed in AVGAS 100 LL for any other reason than to increase octane numbers. Sweden has unleaded AVGAS in use since 1981."

 

- - What about the distribution and infrastructure? Is there any change needed in the current infrastructure as results of 100UL deployment?

 

"This can only be known after knowing the final composition of the fuel – which currently is unknown. Using an unknown component in the aviation field – may cause damage to existing tanks, gaskets, hoses etc."

 

- Did you ever run an aircraft engine with an unleaded fuel type? If yes, does this fuel type have an improving impact on the engine performance?

 

"Sweden pioneered with unleaded grade 80(octane) in 1981. This fuel was also used by the air-force. In year 1991 our second generation unleaded AVGAS grade 91/96 was launched. This fuel is still used in Sweden and also elsewhere. In Sweden regularly about 80 % of the piston powered fleet is using this fuel, which after 25+ years has flown for millions of flight hours in thousands of aircraft and in any weather /technical condition. Removing lead from an engine improves life time of the valvesystem. An engine using 100 LL may have 2000 hours for TBO. The same engine using our unleaded grade 91/96 UL usually runs 3000 hours between TBO"

 

---------------------

 

Note the last.