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Yeah, this is an interesting topic. I've asked
probably a dozen or so Lancair flyers, all flying some form of the IO-550.
NONE of them seem to use the fuel pump for places that I would expect.
That being take off, landing or fuel tank switching. And yet, every low
wing certified airplane that I've ever been in does.
All they can say, is that with a Cont, you don't need to,
in fact, it appears that below 10K feet, there is some suggestion that doing so
(even low boost) will provide "too much" fuel. However, my mind would
suggest that because all of these engines have "return lines", that too much
fuel is just returned to the tank so how can it "over pressure" the lines and
flood the engine...
Maybe Walter and the guys at Gami can offer a
suggestion. If they do, please offer it for both or either IO-550 or
TSIO-550 if they are different.
Thanks,
Alan
You guys don’t turn on
low boost for takeoff and landing?
Chat
Daniel
Super
ES
From: Alan K.
Adamson [mailto:aadamson@highrf.com]
Sent: Friday, September 22, 2006 3:35
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.
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