Show Posts
1
Hangar Flying / Re: Engine Replacement Criteria
« on: May 17, 2010, 07:41:46 PM »
I would encourage you to read articles by Mike Busch on this topic. Try googling his name, or look at his website, Savvy Aviator. If you want to save a lot of money, sign up for his Savvy Aircraft Maintenance Management service for $750 per year--they act as advisors regarding all maintenance decisions for your plane, which is really valuable at times like you are going through now. They tell you who to use for different services and bring data and experience to your decisions.
Regarding TBO, it only has legal relevance for Part 135 planes (basically for-hire planes), which have to be rebuilt at TBO. Part 91 does not require adherance to TBO times for certified planes, nor do TBO's apply to experimentals. Increasingly, smart operators are using engine condition instead of time to decide when to overhaul. Related, the data increasingly are showing that engine maintenance itself causes many failures, so it is foolish to replace good parts just based on time because you increase risk of failure. There are a few exceptions, such as magnetos which apparently do wear based on time. But, to make decisions based on condition, you need good data, such as oil analysis and borescope observations of the condition of the valves and cylinders, as well as EGT data for each cylinder, which most Long EZ's do not the equipment to capture.
I don't have any thoughts about causes of your oil consumption problem. I did not know that you could lose a large quantity through a valve guide, as opposed to through the rings or by blowing it out--but ask an expert, which I am not. I assume the bottom end is in good shape because it only has 950 hours, although the oil samples could confirm this. If that is true, then clearly you would be better off repairing the cylinders instead of overhauling the whole engine. Too bad they did not replace the valve guides when they replaced the rings.
Best wishes.
Regarding TBO, it only has legal relevance for Part 135 planes (basically for-hire planes), which have to be rebuilt at TBO. Part 91 does not require adherance to TBO times for certified planes, nor do TBO's apply to experimentals. Increasingly, smart operators are using engine condition instead of time to decide when to overhaul. Related, the data increasingly are showing that engine maintenance itself causes many failures, so it is foolish to replace good parts just based on time because you increase risk of failure. There are a few exceptions, such as magnetos which apparently do wear based on time. But, to make decisions based on condition, you need good data, such as oil analysis and borescope observations of the condition of the valves and cylinders, as well as EGT data for each cylinder, which most Long EZ's do not the equipment to capture.
I don't have any thoughts about causes of your oil consumption problem. I did not know that you could lose a large quantity through a valve guide, as opposed to through the rings or by blowing it out--but ask an expert, which I am not. I assume the bottom end is in good shape because it only has 950 hours, although the oil samples could confirm this. If that is true, then clearly you would be better off repairing the cylinders instead of overhauling the whole engine. Too bad they did not replace the valve guides when they replaced the rings.
Best wishes.