Pat
Guest
Sturgis, MI
- Aircraft Year
- 1993
- Aircraft Type
- 114B/115
- Reg Number
- N374JW
- Serial Number
- 14595
There are 2 articles on the BeechTalk Newsletter - 04-11-2020 that are very interesting. The first one is about a design flaw of the Continental Engines.
[url]https://www.beechtalk.com/forums/viewtopic.php?f=37&t=180489[/URL]
A segment of the article:
“I am now thinking that the root cause of the exhaust valve-related issues on our engines is fundamentally inadequate mechanical design of the cylinder to begin with; specifically the design relating to the rocker arm and the geometry of the valve stem actuation.
If you watch Dave's video, you will notice that the rocker arm puts a small side load on the valve stem every time the valve opens and closes. In other words, instead the rocker arm's force being perfectly in-line with the axis of the valve, the force vector is slightly off-axis. Over time, that side load translates into wear in the valve guide A cylinder removed only after 200 hours or so, as Dave confirms, already exhibits that side-step when it closes. I witnessed this also and can attest this even on "good quality" Millenniums. You can see this, during Borescoping, as the valve will "scoots" ever so slightly when it seats.
Given that the exhaust valve receives very little lubrication and operates in extreme temps, it is not surprising that it becomes the Achilles' heel of the whole set-up especially if its actuation is subject to side loads.”
The second one is about a FAA comment period. I am sure it will raise some comments.
https://www.beechtalk.com/forums/viewtopic.php?f=37&t=180462
FAA to Open Comment Period on Rulemaking Banning Lean of Peak Since Most Pilots Don’t Understand It
[url]https://www.beechtalk.com/forums/viewtopic.php?f=37&t=180489[/URL]
A segment of the article:
“I am now thinking that the root cause of the exhaust valve-related issues on our engines is fundamentally inadequate mechanical design of the cylinder to begin with; specifically the design relating to the rocker arm and the geometry of the valve stem actuation.
If you watch Dave's video, you will notice that the rocker arm puts a small side load on the valve stem every time the valve opens and closes. In other words, instead the rocker arm's force being perfectly in-line with the axis of the valve, the force vector is slightly off-axis. Over time, that side load translates into wear in the valve guide A cylinder removed only after 200 hours or so, as Dave confirms, already exhibits that side-step when it closes. I witnessed this also and can attest this even on "good quality" Millenniums. You can see this, during Borescoping, as the valve will "scoots" ever so slightly when it seats.
Given that the exhaust valve receives very little lubrication and operates in extreme temps, it is not surprising that it becomes the Achilles' heel of the whole set-up especially if its actuation is subject to side loads.”
The second one is about a FAA comment period. I am sure it will raise some comments.
https://www.beechtalk.com/forums/viewtopic.php?f=37&t=180462
FAA to Open Comment Period on Rulemaking Banning Lean of Peak Since Most Pilots Don’t Understand It
