Howdy all,
I called Zenith a year back to ask about how they determine the vne of their
planes. I was told that the speed assigned was the speed that the
plane has been tested to in flight (at sea level), and not an actual
"failure speed", which they don't have a way of determining and don't test
too.
Also, regarding the 6g design load, both Zenith and Sonex told me the same
thing, the wings on the HD and the Sonex are designed to an ultimate of 9
g's ,
So technically they are aerobatic category stressed, but for legal reasons
they don't state this in writing as they don't want folks doing aerobatic
maneuvers in them.
Note: The HD does stand for Heavy Duty.
I register my 601 HDS as "Utility" class after I swapped out the engine.
Roger
_____
From: owner-zenith-list-server@matronics.com
[mailto:owner-zenith-list-server@matronics.com] On Behalf Of Dirk Zahtilla
Sent: Tuesday, November 25, 2008 2:19 PM
To: zenith-list@matronics.com
Subject: Lets look at the specs
Per Juan Vega:
> pull up the archives, i brought up the issue of VNE and Max manauvering
speeds over one year ago, but the back room engineers ignored it.
>
> Fly it and follow the specs. My guess is the guys flying and that augered
in ignored the flight envelope of the aircraft. BUILD IT TO PLANS AND FLY
IT TO SPECS.
Ok. The zenith website listssome specs for the XL and now the 650as:
Max cruise @sea level 138 mph
75% cruise @8000' 160 mph
VNE 180 mph
G load (ultimate) +/- 6 g
However when I received my plans the VNE is listed as 160 mph
this is an excerpt from the specs page:
Vigorous performance:
"My evaluation of cruise speed showed about 140 mph at 2800-2900 rpm,
however, the company plans a different prop for Sport Pilot.
If we look at these numbers and keep in mind that part of testing a newly
built aircraft is to prove these numbers, how many of you feel safe taking
your XL up to 180 mph?
How about the g load testing. At +/- 6 that should mean a safe limit of +/-
4 (why doesn't zenith state this) with a 50% margin. would you feel safe at
a +4g steep turn? A typical loop produces about 3.8 to 4 gs How about
inverted pushing up at -4g?
How do we decide whether VNE is 160 or 180. if it's 160 what about this 75%
cruise of 160.
I'm sorry but something is wrong here and we deserve factual answers, not
this garbage expecting blind faith. I'm building my XL. I like almost
everything about the design, but I will gladly sacrifice an extra 50lbs. of
weight making it seriously strong. When the day comes that I fly it for the
first time I want to know without reservation that it isn't coming apart,
period.
Dirk Z
