Alan,
I’ve read the posts in response to
your original post. I’ve also reviewed your original and you don’t
say whether or not you are normally aspirated. Regardless, some of the
answers you received conflict with my real life experience so I’ll
recount it for you and then retire; I don’t intend to get trapped in
endless conjecturing.
I fly a L IVP with a TSIO 550 B2B engine.
It is set up with a low boost, high boost and a push button prime, like one of
your responders. Low boost is always used above 10,000 feet. On two
occasions I forgot the low boost and encountered rough running and then engine
surges at about 18,000 to 20,000 feet. Turning low boost on immediately
corrected the problem.
About five years ago my engine quit at 400
feet, immediately after takeoff from Port Columbus, OH, westbound over the
city. No time to think. I turned high boost on, IAW my
understanding of the engine’s needs (thanks, Charlie
Kohler) and it immediately recovered. I climbed out in
disbelief of what happened, stayed within easy gliding range of a recovery
airport and leveled off at 10,000 feet. The engine was running perfectly.
I then turned the high boost off to see what would happen so I would have a
more complete picture for the mechanic. It instantly quit again.
For the remainder of the flight it ran normally on high boost, even at idle in
the high, emergency pattern I used for landing. It ran normally taxiing
in. The engine shop quickly found that the engine driven fuel pump had
suffered a catastrophic failure.
IMHO, the high boost pump worked as
designed. Good luck on your project.
Carl La Rue
L IVP 1560 hrs.
From: Lancair Mailing List
[mailto:lml@lancaironline.net] On Behalf Of Alan
K. Adamson
Sent: Friday, September 22, 2006
2:35 PM
To: Lancair Mailing List
Subject: [LML] Re: Boost pump
switching
Ok, you guys are
making me feel a little better.... I may just stay with the OFF-LOW-(HIGH)
concept on a single switch and do some testing during phase 1.
However, I will share
a recent experience in a TSIO-550. I was flying an ES recently with this engine.
In all flight configurations, at 10K or higher, the low boost was turned
on. There was no hesitation in the engine and it continued to perform
with no rough running, or other noticeable changes. The guys I flew with,
would do a 10K check both climbing and descending. At 10K, boost pump and
landing light on or off depending on climbing (on) or descending (off) - light
opposite.
Alan
From: Lancair Mailing List
[mailto:lml@lancaironline.net] On Behalf Of Jim
Scales
Sent: Friday, September 22, 2006
2:45 PM
To: Lancair Mailing List
Subject: [LML] Re: Boost pump
switching
My ES has a momentary
prime switch along with a low and high boost switch.
I use the high boost
to pressurize the fuel system before starting. I use the prime position
for a couple of seconds before doing a cold start. I do not use it
on hot starts.
I use low boost to
clear the injector lines of any vapor when doing a hot start. I turn it
off for the start. After the engine starts I turn the low boost back on
for about 30 seconds to prevent vaporization. Then the pump is off for
all operations.
(Early on I would use
the high boost pump to cool the fuel lines for a minute or so before a hot
start. Eventually, I found that I could get better results by setting
mixture full rich and then using low boost to clear and pressurize the injector
lines. I can actually hear when the vapor clears and the lines develop
pressure. The pump begins to labor and the sound gets deeper. Hot
starts are no problem.)
I have experienced a
loss of engine driven fuel pump while on the ground. Low boost kept the
engine running but in no way could the plane have been flown. Way too
rich.
I once used the
low boost in flight when trying out tank switching procedures. Low boost
made the engine run extremely rough. I have trouble thinking there is a
ever a time to run the pump in normal flight operations.
My $.02. No
flaming please. This stuff works really well for me.
Low Boost - switched on at or above 10K feet and run for the duration of the
flight at that level to provide added purging of vapors or bubbles that
might exist in the lines
High Boost - Prime at startup.
Ok, now, I've also heard that you use High Boost any time you loose an
engine driven fuel pump. Will low boost suffice?
I've found a couple of switches that I could replace the single with that
will allow switching to low and locking out high unless placed there, or I
could go to an ON-ON-ON
type without the momentary.
So, could you splain to me, what the various boost modes are or if there is
another compromise that I haven't thought of with one switch.