REFLECTOR: Las egas accident

[Alex Balic]

It would be dangerous to have a positive displacement supercharger on an
airplane for just that reason- if anything happens to the drive for the
unit, it will suffocate the engine- there are several makers of centrifugal
superchargers which would produce boost the same way, and still allow for
fairly unrestricted airflow if they stop- I am not sure what type of unit
the velocity factory was testing, or the one that was on the recent accident
aircraft, but would surely be interested to find out.

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Vance Atkinson
Sent: Thursday, August 28, 2008 6:50 AM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Las egas accident

Brian Michalk wrote:
> Not much more information that the original NTSB report.
>
> What does it mean to engage the supercharger?
>   
> A supercharger is a positive displacement compressor.
> Now, technically speaking a turbine (centrifugal) compressor powered via
> belt or other non-exhaust type source is considered a supercharger.
> However, most people understand that a "supercharger" is a positive
> displacement device
>   
> This means that if the power source is removed from a supercharger
> (broken belt, etc.), then it will be a restriction to airflow.
>   
This flight could of had the duct leading to carb/throttle body open.  
That is, spilling out the compressed air that would of gone to the 
engine.  However, some installations have a bypass door (like factory 
fuel injected spam cans) that allow air to flow from an alternate source 
when needed ( like ice in the air inlets)
> So, for the first flights, was the supercharger bypassed?  
Maybe......... maybe the owner will divulge the configuation for this 
particular test flight.
> It's amazing
> to me that the first five hours were uneventful, then this had to
> happen.  It's a tragic loss.
>   
I have an RV friend who has an Eggenfeller engine which worked fine 
until he added a supercharger a year later.  Result, engine stoppage, 
the belt had a problem.  Fortunately, for him he was able to put it in a 
field with min damage.  After repairs were completed, he took the 
supercharger  off.  (it was a Roots type charger)  
> A turbocharger, or centrifugal compressor would not present such a
> restriction.  I have done quite a bit of ground testing with the turbo
> installed as part of the induction path.  The engine runs quite well
> with a seized or non-powered turbo.
>   
Vance Atkinson
COZY N43CZ
VEZ  N3LV