Back in October 2020, Greg Stockman sent in a question to General Aviation News‘ engines expert, Paul McBride, asking about permanently removing a vacuum pump in a Lycoming IO-360-C1C6, installed on a PA-28R-201 Arrow III, built in 1978.
Paul’s answer offer Greg a couple of options for removing the vacuum pump. Now he wants to follow up on that answer with a little more information:
Thanks to a good friend who acts as my “conscience” for my columns, I’ve been advised that I may have mislead Greg and any others who may be thinking about the change he inquired about. This is very important and I hope this information is shared by our readers.
As I stated in my response to Greg, there are no Lycoming Service Publications that cover the removal of a vacuum pump. However, back in the day this type of request was normally discussed with your FAA Principle Maintenance Inspector followed up by submitting an FAA Form 337. This typically was approved in a short period of time and you could proceed with your project.
Now, I’m told that apparently those days are over, and the FAA has taken a different approach. It seems now when you submit the proper paperwork it is reviewed by the regional FAA Aircraft Certification Office (ACO).
I learned a long time ago that, sadly, there is not a lot of consistency among these ACO offices, which has been known to cause some confusion. As an example, one ACO may routinely review and accept your paperwork for removal of the vacuum pump in this case, when a different ACO may reject the very same thing.
My recommendation is that you ask your FAA PMI any questions you may have prior to submitting any paperwork and most certainly before doing any work.
The other important thing I learned from my “conscience” was the fact that Lycoming does not supply the complete vacuum system on any aircraft. It’s true that Lycoming supplies the capabilities for driving the vacuum pump, in addition to several other accessories provided by the original airframe manufacturer, therefore any of those components will be covered in the airframe manufacturer’s Type Certificate for any particular aircraft rather than any of Lycoming’s publications.