I didn’t write that quote BTW – I questioned it 
Capitaine wrote:
Our club’s Rotax-powered Aquila is run on Mogas because avgas is too ‘dry’ so the oil has to be changed every 50 rather than 100 hours
If running on 100LL (with lead), the oil in a Rotax must be changed every 25 hours. The lead is accumulated in the oil, and will destroy the gears in the PSRU. At least that’s what I have been told, or read? don’t remember. 100LL is toxic waste anyway, don’t use it unless you absolutely have to.
I’m waiting for the explanation of how Scandinavian non-alcohol gasoline contains no toxic benzene or toluene at all.
100LL is great stuff for my purposes, I like high quality fuel over cheap stinky car gas. However in truth for my use I’d prefer the same stuff minus the lead because my engines don’t need it.
Silvaire wrote:
I’m waiting for the explanation of how Scandinavian non-alcohol gasoline contains no toxic benzene or toluene at all.
Different shades of grey. Heroin and alcohol are both toxic, but a shot of Jäger is much preferable over a shot of heroine (for most people at least).
I’m we aware of the 1800rpm shutdown procedure to reduce lead fouling of the plugs on C152’s. However what about O200 powered aircraft? As far as I can tell continental don’t make such a recommendation and the o200 certainly suffers from lead fouling.
LeSving wrote:
If running on 100LL (with lead), the oil in a Rotax must be changed every 25 hours. The lead is accumulated in the oil, and will destroy the gears in the PSRU. At least that’s what I have been told, or read? don’t remember. 100LL is toxic waste anyway, don’t use it unless you absolutely have to.
Just to be nitpicking- as per Maintenance Manual, the oil change interval goes down to 50 hrs, not 25. Using leaded fuel (for more than 30% of the time) pretty much halves each maintenance interval on the engine, but it has a 100-h base period to begin with.
The exception is the gearbox, which goes down to 600h instead of 1000h with unleaded fuel, which gives you three gearbox inspections within the 2000h TBO instead of only one.
The main reason for this is not the gears, but the overload clutch inside the gearbox. It is designed to open in case of a prop strike, and protect the core engine from any shock loading. Works like a charm, but it cannot operate properly if it is covered with “greasy” lead, so to prevent it from slipping during normal operation, it has to be opened and cleaned.
Sorry for the slightly off-topic post…
A_and_C wrote:
Above we have seen a lot of opinions about the effectiveness of the 1800 RPM shutdown in cleaning the spark plugs some of this has a basis in scientific fact and others no so, however now for some hard fact.My Cessna 152 fleet had spark plug fowling problems being a regular occurrence when the engine hours got towards 50 ( oil change and other Lycoming SB’s actioned at this point ). The introduction of of the Lycoming recommended shut down procedure has eliminated this problem ( and the three hours Labour getting a licence engineer to drive to the aircraft & fix the problem. ) so all in all from an operational point of view complying with this Lycoming SB saves me a lot of money.
But that’s a training fleet, right? So no wonder you get a lot of plug fouling – training aeroplanes generally operate at full rich most of the time.
I lean aggressively on the ground and per Deakin’s preachin’ in the air, so unsurprisingly I never see any plug fouling. Just about the only times I’m fully rich are startup, power checks, takeoff and climb below about 3,000ft.
You don’t have to shut down like that if you know how to properly lean your engine during ground operations. Its purpose is to avoid plug fouling.
During ground ops I set my power to 1200rpm and lean very aggressively until it is impossible for the engine to run higher rpm. It helps avoiding spark plug fouling, taxying unnecessarily fast and you can’t take off with mixture like that since engine will immediately stop if you try to increase power beyond 1200rpm. With such aggressive mixture setting you can idle all day long if you have to.
Agree. This running up to 1800 RPM before shutdown makes unnecessary noise and also identifies you as an ignorant (regarding engine operations) pilot.
boscomantico wrote:
This running up to 1800 RPM before shutdown makes unnecessary noise and also identifies you as an ignorant
But that’s not an engineering argument. At my airport, that noise gets drowned out by all kinds of other noise. Nobody would look at me as ignorant. I actually have never seen any aviator on any airport that gets irritated by engine noise.
