Over the past few flights I noted my Lance's performance. I have a habit of doing this because it tends to point to issues if it is slowing down from previous benchmark performance numbers. But now I'm been puzzled how I suddenly gained about 3 knots without adding performance mods.
There are only two things that I have done:
1) Adjusted cowling to fit tighter. This could potentially reduce air slippage out the top of the cowling.
2) Changed engine mounts.
Speed gain measured by TAS indicator. RPM, MP and fuel flow same as I normally run it. Measured against last set of test data that I did after annual. Nothing on the engine has changed - except the mounts.
So I was thinking: Could the engine mount cause a performance increase?
Think about P-factor. When the nose is high you need right rudder. When the nose is low in relation to the airflow you need left rudder.
If the engine was sagging due to aged engine mounts, would it tend to cause the airplane to be slightly pitch up? Because the engine would be pointing slightly downward, right? Would that not be the same effect as nose-high pitch attitude? And if the airplane is in nose-high pitch attitude (relative to angle of attack on wings) it would be slower, just as if pitching up for slow flight.
Nah.. couldn't be, right? But when I changed the engine mounts I noted that I had to adjust the rigging a bit. The airplane wanted to roll slightly left when previously it was perfectly level.
This was a puzzle to me. However, when you think about it, engine up would mean that the wings would have a slightly different angle of attack.
I've often wondered why one airplane will be 4 - 5 knots faster than another when all other factors such as mods, weight, engine time, compressions, flight conditions, etc. are nearly the same. So tell me - Am I crazy here or did I accidentally stumble upon a performance mod for tired old airplanes?
Thoughts?
There are only two things that I have done:
1) Adjusted cowling to fit tighter. This could potentially reduce air slippage out the top of the cowling.
2) Changed engine mounts.
Speed gain measured by TAS indicator. RPM, MP and fuel flow same as I normally run it. Measured against last set of test data that I did after annual. Nothing on the engine has changed - except the mounts.
So I was thinking: Could the engine mount cause a performance increase?
Think about P-factor. When the nose is high you need right rudder. When the nose is low in relation to the airflow you need left rudder.
If the engine was sagging due to aged engine mounts, would it tend to cause the airplane to be slightly pitch up? Because the engine would be pointing slightly downward, right? Would that not be the same effect as nose-high pitch attitude? And if the airplane is in nose-high pitch attitude (relative to angle of attack on wings) it would be slower, just as if pitching up for slow flight.
Nah.. couldn't be, right? But when I changed the engine mounts I noted that I had to adjust the rigging a bit. The airplane wanted to roll slightly left when previously it was perfectly level.
This was a puzzle to me. However, when you think about it, engine up would mean that the wings would have a slightly different angle of attack.
I've often wondered why one airplane will be 4 - 5 knots faster than another when all other factors such as mods, weight, engine time, compressions, flight conditions, etc. are nearly the same. So tell me - Am I crazy here or did I accidentally stumble upon a performance mod for tired old airplanes?
Thoughts?
