It pays to test all the systems on the ground. This failure would

have

probably been found on the test stand if sufficient time in ground

running

had been done. And no risk to plane or pilot. See my discussion I

sent to

the group a couple of years ago.

smale@ncinternet.net

Mike Wills wrote:

  Keith's email indicates there were about 20 hours of run time on the
installation, 4 of which were flight hours and the other 16 hours were
ground run. If it were your plane would you consider 16 hours of ground
test time sufficient to prove the installation prior to beginning flight
testing? How much ground test time is sufficient? 20 hours? 100 hours?

Or

do you just test until something breaks and then you know how long to
expect that particular part to last? If it were my airplane I would have
considered 16 hours of ground test time sufficient to prove the
installation. Its always easier to be the quarterback on Monday morning.

  Someone else pointed out that during the initial flight test phase it
makes sense to stay within a glide of the airport. I totally agree.

Also,

it seems possible to me that this was not a sudden catastrophic failure
(though thats not certain). Could be that there were indications of
impending failure that might have been found through inspection prior to
the last flight. All of the heat shielding around the exhaust may have
hindered or precluded those inspections. The fiberglass wrap around the
exhaust system makes routine inspection virtually impossible.

Mike Wills

I agree Mike.
They may have run it 16 hours on the ground but obviously they did
not inspect it adequately. Something like that does not just happen
all at once. It starts with a small crack.

I have 2 comments to make.
! I was still finding problems at 20 hours at max power. It took 50 hours on
a test stand to run successfully with out problems. the engine must have a
prop on it to develop vibration similar to the airplane.

2 if the engine was run on the aircraft in ground testing, it would be
difficult to develop full power. very difficult to tie the plane down, with
out damaging structure. If the plane had a fixed pitch prop full power
probably could not be developed and max stress on the power plant would not
occur. problems could remain hidden until flight. if the plane had a
constant speed prop this would not apply. I have considerable experience in
ground testing because of my one of a kind istallation. I did not trust the
powerplant until i got very bored running it. I still do not completely
trust it in the plane.

chris smale
smale@ncinternet.net

 
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