lml@lancaironline.net Mailing List Archive

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.

Jim Scales

N98AF

Angel's Playmate

800 hours

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.