I have set up the engine to flow 43 GPH at 2700 = RPM/38.5” MP and full rich mixture on takeoff. I can tell you from personal = experience that my engine will die with the boost pump on high and full = throttle/mixture in. Since I can control fuel flow with the mixture, or by turning = off the boost pump, I’m thinking this is better than the alternative of = not having enough fuel flow should either the mechanical or electric pump = malfunction. Likewise, I’m not ready to set up my system to run with the boost = pump on at all times. To me, that means the engine will run lean, if not quit, = if either the mechanical OR the electric pump fail. Running the boost pump on was = no big deal with carbureted engines…the float valve in the carb just shut = off the flow when it got enough, no matter (within reason) the pressure. Not = so with constant flow injection systems where fuel flow is directly related to = input pressure and engine RPM…

BTW, I FINALLY checked my flap extension on the ground = and in the air. I marked the full down flap position with pieces of red tape on = the flaps positioned to “reveal” just behind the trailing edge = of the wing when viewed from the cockpit. There is some slop in the linkage, so = they do “dangle” lower than they fly. This is normal/expected. I = was careful to “air load” the flaps before installing the tape = by pushing them toward the retract position firmly before establishing the = sight line. (BTW, it is IMPORTANT that the flaps NOT hit the limit of the = track travel when fully extended—write back if any questions about this, = but apparently you don’t have this problem anyway.) We then went up = for a flight check. Flaps extended fully (all the tape showing) at about 135 = KIAS, which is the full extension limit speed.

Thought you’d like to = know…

Bob

From:= Lancair = Mailing List [mailto:lml@lancaironline.net] On Behalf Of Colyn Case at = earthlink
Sent: Friday, June 19, 2009 12:22 PM
To: lml@lancaironline.net
Subject: [LML] Re: Boost pump question

Richard said: When you setup your fuel system for = your engine you should verify that high fuel pump mode will not flood your = engine.

I'm not sure what you can do about that except cut your max = FF to too low a rate. On my plane, the engine definitely will not run = well

with high boost AND a properly functioning mechanical pump. = I'm not sure it will outright die or not.