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wing tank fuel line connection.. (probably not related)

 
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frank.hinde(at)hp.com
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PostPosted: Tue Mar 28, 2006 8:18 am    Post subject: wing tank fuel line connection.. (probably not related) Reply with quote

I would suspect most fuel starvation is caused by three factors...

1) Running out by trying to stretch range.
2) Poor venting or running vent to tubes to a low pressure area on the
airframe
3) Vapour lock through not understanding the physics of this deadly
phenominom (sp?)

I doubt the choice of fuel line represents a big risk area but your
point about experimenting is well taken.

Please read the extensive list of emails about fuel system design on
this forum to understand the physics of pumping a high vapour pressure
liquid...namely fuel, especially autofuel.

Regards

Frank
601 HDS 394 hours

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Tim Juhl



Joined: 21 Mar 2006
Posts: 488
Location: "Thumb" of Michigan

PostPosted: Tue Mar 28, 2006 10:01 am    Post subject: Re: wing tank fuel line connection.. (probably not related) Reply with quote

Frank,
I would agree with you on all points. You can be assured that I'm paying close attention to this issue since constructing a low wing airplane will be a new one for me. I have instructed in a number of them but all my personal aircraft have (and are) high wing so gravity does my work for me.

Reviewing the NTSB reports on the 601, most of the engine stoppages did not appear to be the result of no or low fuel or mechanical failure, thus my interest.

As far as your other comments: Lack of proper venting is a real concern and has contributed to a number of accidents. Mud dauber wasps have been known to bring airplanes down by packing mud in the vents which the pilot did not catch on preflight. We also had a fellow with an old airplane who installed his ram air vented caps backwards and wondered why he had problems with fuel flow.Rolling Eyes Vapor lock is something I've never experienced in 30 + years of flying but I did teach power recovery methods for it in Cessnas. I wonder if with more people using mogas it has become a greater problem?

I appreciate the wisdom and comments of those like you who have had more experience with the 601 type. With 394 hours on your aircraft you obviously must have done things right Smile

Tim


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frank.hinde(at)hp.com
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PostPosted: Tue Mar 28, 2006 10:28 am    Post subject: wing tank fuel line connection.. (probably not related) Reply with quote

Well of course vapour lock has four components.

1) Sucking on fuel..up hill or through restrictions
2) Higher vapour pressure fuel (namely mogas)
3) Heating the fuel (hot day plus a mechanical fuel pump on a hot
engine)
4) Altitude.

Item 3 is not that big of a deal in a 601 because it doesn't usually fly
that high. On an RV at 20,000ft this can be a real issue with fuel
literally boiling in the gas tank!

Items 1,2 and 3 can however easily collide on an unsuspecting builder
and there are documented (of course the evidence dissapperas by the time
of the accident investigation) cases of crashes. My fear is that folks
think they are safe because they sort of copy what "Real airplanes
do"...But of course a Certified ship is using the same fuel system as
all airplanes were when the earth's crust was still soft..In other words
nobody in their right mind would trust an electric pump (even two
redundant pumps) back when Lycoming first certified its fuel system. To
get around a rather poor system they use 100LL with a lower VP and cool
the pump with a blast tube. The boost pump is intended to be a backup in
the low wing configuration from what I can see.

While this marginal system works with 100LL it may not work with mogas
and as electric pumps are probably as reliable as mechanical ones these
days...Well there are just better ways of doing things.

Incidently..My FI RV (yet to fly) has an electric punp in each wing root
and no mechanical pump..The only dissadvantage I see is what happens if
struck by lightening?

Cheers

Frank

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frank.hinde(at)hp.com
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PostPosted: Tue Mar 28, 2006 10:44 am    Post subject: wing tank fuel line connection.. (probably not related) Reply with quote

Ooops...i meant iten #4 is not that big of deal.

Frank

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