Dave Siciliano
Final Approach
On the Bonanza Net, there has been a lot of discussion about whether one should do a run up and mag check before each flight. Please keep in mind these are plane owners that have a lot of flying time-many former military and airline pilots. Some folks have wondered why they don't see others do a runup. Here's one thread that is pretty enlightening. There was a lot of other discussion also. Many of these folks have a lot of after market parts on these aircraft: so, they may be much different than what you are flying or what even a normal Bonanza might be.
Dave
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This problem is new to me, but it ties in well with my thoughts that many of us spend way to much time and effort on engine runups.
All we really need for a mag check is a quick observation at twelve to fifteen hundred RPM that all plugs are firing. The best time to do a diagnostic magneto check is inflight.
Why do we check the props before very takeoff? Personally, I think cycling the propellors before takeoff is a throw back to ancient propellor design and ancient oils.
I quit cycling my propellors when I read in a Continental overhaul manual that I should not cycle the propellor before the first test hop of the engine because that action took oil pressure away from the front main bearing and that the new engine needed all the oil it could get.
In the olden days, we were taught to cycle the propellor to get warm oil into the dome and to help remove the sludge. What will happen if we don't cycle the prop? Well, it may surge on takeoff.
Modern propellors have a small flow of oil all of the time. If the engine is thoroughly warmed at moderate power, the oil will be circulated adequately.
I have not cycled the propellor in the last three thousand hours of operation of my airplane and it has never surged even once.
Modern propellors fed with modern oil do not need to be cycled.
Now, how about the feather check? Well, if you check it once, how do you know it hasn't failed immediately after that check?
Personally. I make a feather check before my first flight in any multiengine airplane. After that, I check it only on occasion.
When that occasion arises vary's based on my knowledge of the airplane. Once a week or once every twenty to thirty hours of operation serves me just fine. Most of our light twins have fixed mechanical connections that maintain featherability. If the mechanisms work once those connections are made, it should continue to work as long as those connections are properly maintained.
Back when I was a gainfully employed airline pilot flying piston engined airplanes, we checked the feather buttons after every start because they were electrically operated and the power for the feathering motor came through the same current limiter that was used for starting the engine. The idea was that by hitting the feather pump momentarily, we were checking the current limiter. There was no need to run that pump any longer than was needed to assure that it was getting electrical power. It always occurred to me that we might even fail that current limiter by the momentary check, but it never happened to me, so I guess it worked acceptably.
We cycled the propellors with the propellor controls only at the first runup after picking up any particular airplane. If we made ten more stops that day, no more cycling and only a long enough tap of the feather button to assure electrical continuity.
Do all the runups really needed to assure proper operation of the components, but don't do them needlessly or without thought as to why you are doing what you are doing and what, if anything, is being accomplished.
Dave
==========================================================
This problem is new to me, but it ties in well with my thoughts that many of us spend way to much time and effort on engine runups.
All we really need for a mag check is a quick observation at twelve to fifteen hundred RPM that all plugs are firing. The best time to do a diagnostic magneto check is inflight.
Why do we check the props before very takeoff? Personally, I think cycling the propellors before takeoff is a throw back to ancient propellor design and ancient oils.
I quit cycling my propellors when I read in a Continental overhaul manual that I should not cycle the propellor before the first test hop of the engine because that action took oil pressure away from the front main bearing and that the new engine needed all the oil it could get.
In the olden days, we were taught to cycle the propellor to get warm oil into the dome and to help remove the sludge. What will happen if we don't cycle the prop? Well, it may surge on takeoff.
Modern propellors have a small flow of oil all of the time. If the engine is thoroughly warmed at moderate power, the oil will be circulated adequately.
I have not cycled the propellor in the last three thousand hours of operation of my airplane and it has never surged even once.
Modern propellors fed with modern oil do not need to be cycled.
Now, how about the feather check? Well, if you check it once, how do you know it hasn't failed immediately after that check?
Personally. I make a feather check before my first flight in any multiengine airplane. After that, I check it only on occasion.
When that occasion arises vary's based on my knowledge of the airplane. Once a week or once every twenty to thirty hours of operation serves me just fine. Most of our light twins have fixed mechanical connections that maintain featherability. If the mechanisms work once those connections are made, it should continue to work as long as those connections are properly maintained.
Back when I was a gainfully employed airline pilot flying piston engined airplanes, we checked the feather buttons after every start because they were electrically operated and the power for the feathering motor came through the same current limiter that was used for starting the engine. The idea was that by hitting the feather pump momentarily, we were checking the current limiter. There was no need to run that pump any longer than was needed to assure that it was getting electrical power. It always occurred to me that we might even fail that current limiter by the momentary check, but it never happened to me, so I guess it worked acceptably.
We cycled the propellors with the propellor controls only at the first runup after picking up any particular airplane. If we made ten more stops that day, no more cycling and only a long enough tap of the feather button to assure electrical continuity.
Do all the runups really needed to assure proper operation of the components, but don't do them needlessly or without thought as to why you are doing what you are doing and what, if anything, is being accomplished.
)
