Airborne_Again wrote:
Well… In my club we never follow that drill and we have never had any valve sticking problems either. We did have some very minor problems with lead fouling of the spark plugs which were easily fixed by running lean at full power for a short while during engine runup. After switching to unleaded fuel (91/96UL) some years ago that problem has gone away, too.Our aircraft use Lycoming (I)O-360 engines.
We had the same problems with similar aircraft. Solved it with fine wire spark plugs and occasionally unleaded fuel.
We never rev up the engine more than needed, but always run it leaned on the ground.
Bathman wrote:
Well as you use 91/96 unleaded fuel I would say thats the reason you don’t have any plug fouling or sticking valve problems. How its operated won’t have anything to do with it.
Sure, but as I wrote we didn’t have any valve sticking problems even when we were using 100LL.
Airbourne_again.
The vast majority of problems are with O-235 engines, however the long taxi time at this airfield so the O-360 gets the same shutdown to keep SOP both within the club and with the other military operator of SEP aircraft.
I so have a question as to why some think us ignorant ?
We have a problem.
We use approved manufacturers data and practices to solve that problem.
We reduce operating costs and increase reliability.
Result We slagging off from some inthe GA community .
A_and_C wrote:
I so have a question as to why some think us ignorant ?I’ve certainly never called you ignorant and I don’t doubt that there are combinations of engines and operating conditions where this matters.We have a problem.
We use approved manufacturers data and practices to solve that problem.
We reduce operating costs and increase reliability.
Result We slagging off from some inthe GA community .
But you wrote that “the lycoming shut down drill is required to assure engine reliability” and I simply can’t see that it is, in general.
A search for e.g.
spark plug condition
digs out lots of good reading.
What I have found is that, on the engine warm up run immediately prior to doing a service, the spark plug condition is determined mainly by what you do in the last few minutes before shutdown.
If you really really lean the engine before shutdown at 1200rpm (lean to the point where the EGT peaks, which at 1200rpm is very lean) then you get clean plugs, and because the power setting is so low there is zero risk of doing any damage. I posted the plug photos here several times.
If you think about the physics, this is pretty obvious. The thermal time constant from the combustion chamber to the spark plug is going to be in the order of seconds at most, especially given the density of the gas (of the order of 100x surface density). As will any substance deposition (or sublimation of the same) on the plug.
Hence I think the 1800rpm is spurious. I am not saying it is ineffective; it probably does what people claim for it. But nobody really thought about why it works. GA is like that. Stuff is written down, everybody follows it, 99% of maintenance has zero owner involvement so nobody spots any correlation between what a pilot does and what the engine looks like. If you need evidence of the foregoing, ask any engine shop whether you should fly lean or rich; I bet you most will tell you the engine will melt if you fly lean. Almost no mechanics fly… In the land of the blind, the one-eyed man is King.
You see the same throughout “technology” wherever there is a disconnect between users and “engineers”. For example, in most of retail IT, there is no connection at all and you can sell a piece of total crap which doesn’t work for most users and the manufacturer will never find out – and if he did he would not care anyway because he’s now developing v2. Try googling for some IT issue; nearly all the hits you get are crap, recycled from other websites and loaded onto the website you found as click bait for advert clicks.
I’d say the Lycoming shut down drill isn’t required for reliability.
My aircraft does high numbers of very short flights in the summer while towing gliders. The act of very aggressively leaning for ground operations (the mixture knob is a hair from idle cutoff during taxi) has prevented any plug fouling. I personally inspect my own spark plugs and they are never anything other than the proper “healthy” colour.
Also my alternator quite happily puts out 10A+ at 900RPM :-)
spirit49 wrote:
And before I forget; You don’t have to warm your engine for 15 minutes just outside my open hanger door with 1800rpm to get into the green on your oil temp meter before moving to the holding area.
Oh yes! I hate it when people do that. One of my hangar neighbours even went so far as to tow his aircraft nose-first 6 m straight out of the hangar door, fire the aircraft up and then do his run-up right there, blowing straight inside the hangar! However that is not frequent. Helos hovering close to open hangar doors are our worst offenders.
Yes I keep RPM around 1000 or even less all the way to the runup area. The problem is that in order to avoid brake use, sometimes I need to taxi at 700RPM and that means I will be discharging 20 amps throughout my taxi. Hence I need to charge back up in the runup area or, even worse, shutdown area when out of base.
One exception is on soft grass where I do not seem to have any charging issues.
spirit49 wrote:
I have never seem a discharge on my battery at 1000rpm.
Hmm, I thought you had the 90 amp Ford…either you have few avionics, you leave your strobes, pitot heat and landing light to your ‘entering runway’ checklist or your regulator is better than mine (Zeftronics) or I have some high-resistance elsewhere in the system…
People will do that when they are being billed brakes-off to brakes-on, which is pretty common on the GA scene, and is the product of a lack of trust in the renter. Not without reason; I saw this myself, and one instructor was the worst culprit!
With so many people in GA being only just able to afford the flight, the only way around this problem is to bill for airborne time only, and then you need some means of verifying the reported airborne time. An EDM700 will do nicely – as that instructor found out 
He tampered with the FOB in the fuel totaliser but didn’t know the EDM700 was storing stuff every 5 seconds…
My plane draws about 25-28A with everything on so long low rpm idle is not an option.
A_and_C wrote:
I so have a question as to why some think us ignorant ?
Because there is a high correlation between high rpm startup/idle/taxi/shutdown practices and:
Peter wrote:
People will do that when they are being billed brakes-off to brakes-on, which is pretty common on the GA scene, and is the product of a lack of trust in the renter. Not without reason; I saw this myself, and one instructor was the worst culprit!
When I was doing my PPL and renting for a short period thereafter, we were billed on the Hobbs meter. No incentive therefore for excessive time on the ground with the engine running. Once you’ve started it, get moving – that was my mantra. Required abandoning the school-published checklist for a more realistic procedure.
