Message-ID: <009801c1ac53$c84df5e0$af193e44@rocsth01.mi.comcast.net>
From: "Edmond de Chazal" <edechazal@home.com>
To: <lancair.list@olsusa.com>
References: <20020120063035.AAA1458@pop3.olsusa.com>
Subject: Re: High speed vibration in a 360 & high altitude performance
Date: Sat, 2 Feb 2002 20:40:38 -0500
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Thanks to all who gave me suggestions to remedy my high speed vibration.
After some tweaks to the gear doors, it seems the vibration has been
eliminated, or at least pushed out of the way.  Now, instead of a buzz at 195
KIAS, things are smooth up to the max tested speed of 210 KIAS.  The changes
included placing some weathersealing under the nose gear door at the rear so
that if it vibrates, it hits something soft instead of the fuselage.  I also
adjusted both inboard gear doors at the hinges and tightened the fit of the
left inboard door by reducing the stop.  It's a frustrating exercise since the
inboard hydraulics really apply a lot of force and pull the door hard up
against the front of the well opening.  Getting that perfect fit I once had on
the bench seems hopeless.  But, that notwithstanding, the buzz is gone and I
now know it is not some flutter problem.  The tail and ailerons look rock
solid at these speeds.

While I was at it, I collected some data some of you may be interested in.
These were high altitude tests.  The marvelous mountain high EDS system was
strapped on and the required IFR clearance in hand. This plane has the short
wing and ram air.  The engine is a stock IO360-B1F.  The prop is an MT-12B,
Airplane weight at test was 1,600 lbs.

Level Flight:

FL 200:  WOT, Map=14.1 inches, 2500 rpm, leaned to onset of roughness,
8.1gph, -28 degrees C,  131 KIAS = 178 KTAS
FL 180:  WOT, Map=15.3 inches, 2500 rpm, leaned to onset of roughness,
8.0gph, -24 degrees C, 139 KIAS = 183 KTAS
17,000 feet:  WOT, Map=16.5 inches, 2500 rpm, leaned to onset of roughness,
8.0gph, -23 degrees C, 146 KIAS = 189 KTAS
15,000 feet:  WOT, Map=17.9 inches, 2500 rpm, leaned to onset of roughness,
8.1 gph, -20 C, 152 KIAS = 190 KTAS

Maximum speed attained in level flight was 197 KTAS at 9,000 feet: 22.7 map,
10.1 gph, 2500 rpm, -7C.  That seems to be around 75% power as I read the
Lycoming charts.

Climbs:

Maintaining a constant 1,000 feet/min climb (WOT, 2500rpm) at:
3,000 feet - 160 KIAS  (yes, fellow builders who fly certified planes, that's
correct)
5,000 feet - 158 KIAS
7,000 feet - 150 KIAS
9,000 feet - 143 KIAS  (some leaning begun here)
11,000 feet - 125 KIAS
13,000 feet - 120 KIAS

Maintaining a constant 500 feet/min climb at:
14,000 feet - 130 KIAS
16,000 feet - 126 KIAS
18,000 feet - 120 KIAS
FL190 - 115 KIAS
FL200 - 110 KIAS

The handling was not confidence inspiring while climbing through the high
'teens'.  Airspeed was slow and the aileron control was very light, as if it
was near stall.  But as you can see, the airspeed indicator was always well
above stall and the angle of attack indicator never (sport model) never moved
off the peg.  Stall is 60 KIAS.  But the controls were so soft that I did not
feel confident proceeding beyond FL200.  It was strange being cleared by ATC
to "maintain at or below FL230".  I believe the manual states that Vy is 90
KIAS.  Consequently, I presume the plane will climb to well over FL200 prior
to reaching its service ceiling (defined as <100 fpm rate of climb).  Has
anyone probed to see where that might be?

For this airplane, anyway, it seems the operational ceiling that maintains
reasonable performance and handling is the VFR altitudes going up to 17,500
feet.  A very nice range of capability for such an economical bird.

Best Regards,
Ed de Chazal,
361DC

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