Re: PA28-181 Fuel pressure drop off - Inspired by the Gascolotor thread.

It seems, from the initial comments that a fuel pressure fall off during
climb in PA28 aircraft is seen more often than I thought.
As a mechanical engineer, I can concur that the engine driven fuel pump is
only just keeping up with the full fuel flow needs of a 0-360.
Which is the reasoning behind why I decided to fit a new fuel pump.
My thinking was that the internal diaphragm was tired and could fail.
Sound reasoning, but on the assumption that the pump was more than man
enough to hold good fuel pressure. Not so maybe.

Well where do I go from here .....

Roy



<papenfussDIESPAM@xxxxxxxxxxxxxxxxxxxx> wrote in message
news:dhc0mg$b5l$1@xxxxxxxxxxxxxxxxxxxx
> Roy Page <g4dyr*Removethisantispamstuff*@earthlink.net> wrote:
> : Well you could be correct about a possible vapor lock.
> : As far as I can see the fuel lines are not insulated.
> : The autofuel STC on an Archer calls for mods to the fuel system to
> prevent
> : vapor locks.
> : But I do run on 100LL which is less volatile that Regular Gas.
> : But if the PA28 aircraft are prone to vapor locks, I would have expected
> to
> : see an AD a long time ago ?
>
> : Thanks for the input.
>
> My cherokee could be vapor lock, but I've seen it on three different
> cherokees
> that I've flown, with autofuel or on 100LL.
>
> The flow of the pump is just barely adequate. Petersen described the
> "ditch
> test" where they had to put the tail of the plane down in a "ditch" to get
> a high
> nose-up attitude. In the worst conditions, the stock fuel system was
> unable to
> deliver the flow rate with an acceptable safety margin. Thus the
> modifications to the
> fuel system for autofuel STC.
>
> What *really* bugs me is that a PA28-160 has to do the fuel mod for the
> STC,
> but if it's got low-compression pistons (i.e. PA28-140/150), the fuel mod
> isn't
> required. You tell me how changing the pistons (i.e. low compression vs.
> high
> compression) changes fuel flow. Safety through liability and
> regulation...
>
> -Cory
>
>
> *************************************************************************
> * Cory Papenfuss *
> * Electrical Engineering candidate Ph.D. graduate student *
> * Virginia Polytechnic Institute and State University *
> *************************************************************************
>


.

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