While flying a friends '79 T-Arrow this week I observed that the manifold pressure drops several inches and then returns about every 5 minutes. Cont TSIO 360 FB I have not observed this drop on other aircraft flown and certainly not on my own T-Arrow.
Manifold pressure set at 30" at 15,000 (same thing happens at lower altitudes, doesn't seem to be related to altitude) the manifold pressure will slowly drop 2 or 3 inches over the course of 30 seconds and then return to 30" in about another 30 seconds. This will repeat every so often and isn't predictably repeatable. Sometimes it does it and sometimes it doesn't.
The fuel system has been setup per Cont's service recommendations. However, I am suspicious the manifold pressure drop may be related to fuel. Upper deck vacuum does not appear to be leaking. Engine has about 1,500 hrs SNEW and a new top 100 hrs ago.
Any other suggestions on investigation?
Manifold pressure set at 30" at 15,000 (same thing happens at lower altitudes, doesn't seem to be related to altitude) the manifold pressure will slowly drop 2 or 3 inches over the course of 30 seconds and then return to 30" in about another 30 seconds. This will repeat every so often and isn't predictably repeatable. Sometimes it does it and sometimes it doesn't.
The fuel system has been setup per Cont's service recommendations. However, I am suspicious the manifold pressure drop may be related to fuel. Upper deck vacuum does not appear to be leaking. Engine has about 1,500 hrs SNEW and a new top 100 hrs ago.
Any other suggestions on investigation?
