Message-ID: <01C12EEB.02CE47B0.thomas.low@sri.com>
From: Thomas Low <thomas.low@sri.com>
Reply-To: "thomas.low@sri.com" <thomas.low@sri.com>
Reply-To: lancair.list@olsusa.com
To: "'lancair.list@olsusa.com'" <lancair.list@olsusa.com>
Subject: L/D Max,  Lancair 235 Comments, Hole in the product line
Date: Mon, 27 Aug 2001 11:25:42 -0700
Organization: SRI International IPET
Encoding: 72 TEXT

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Gentlemen
	Lets see if we can put this subject to rest.  The relationship between max 
range and max endurance is given by:

	Speed for Best Range=Speed for Max L/D
	Speed for Longest Endurance= Speed for Max L/D Divided by 1.316

We can also discuss the optimal cruise speed, which results in the minimum 
fuel flow per knot of airspeed. This is given by

	VmaxL/D*1.316.

These equations assume no wind, and a fuel burn rate that is proportional 
to power delivered. (constant efficiency).  For details, see 
http://www.eaa1000.av.org/technicl/perfspds/perfspds.htm

	To address Steve Reeves questions relating to the 235, as a happy owner of 
one of these birds, I will provide my two cents...
	The 235 kit was not produced in as great a number at the 320/360 
variation, and you certainly don't see as many 235's around anymore.  As 
far as the tradeoffs between the 235 and 320/360, I offer the following 
observations:
	The 235 represents a good tradeoff between economy (purchase and operat  
ing) and performance, but has some limitations that should be considered 
before deciding on one.  As far as cost,  235's, when you can find them, 
sell for between 40 and 60 k.  The 320's and 360's are about twice that 
amount.
	With the standard 118 HP 0-235 powerplant and fixed pitch prop, takeoff 
and climb performance is "modest", and may be a limiting factor when 
operating at high density altitudes.  My plane has the L2C engine with 
9.7:1 pistons.  I comfortably operate out of a 2600 foot paved runway at 
sea level.  I see climb rates (full fuel 33 gal) of 800 fpm solo, and 600 
fpm with a passenger at 120 mph.   I am reluctant to operate out of high 
altitude airports unless solo.  I visited Lakeview, Oregon this summer, 
which is around 5000 MSL.  The 5000 foot runway was more than adequate for 
the early morning departure (solo).  Takeoff and climb performance should 
be improved greatly if a controllable pitch prop is used.  (I see 2370 RPM 
static)
	Cruise performance is 190 mph indicated at 25 inches and 2650 rpm, 3000 
MSL.  Fuel burn is typically between 6.0 and 7.5 gph in cruise.  True 
speeds of 200 mph  at 21 inches and 2700 are achieved at 9000 feet.  My 
empty weight is 945 lbs.  Don't expect to carry much baggage with full fuel 
and a passenger. The 235 airframe is only slightly smaller than the newer 
320/360, but the instrument panel is considerably smaller, and outfitting 
for full IFR was a challenge.  My panel has a single COM, Transponder, 
VM1000, Airspeed, Horizon, Altimeter, Turn Coord, Loc/GS, Marker Beacon, 
Vac, Gyro Compass, and Climb, Carb Temp, Clock and fuel gauges.  I cant get 
anything else in!  I am presently not IFR rated but plan to start soon.
	I haven't flown a 320/360, but the stability and sensitivity of the 235 
(IMHO) makes it less than an ideal IFR platform,  The aircraft is neutral 
in roll, and requires attention to keep the wings level.  A single axis 
autopilot should be considered for IFR.  Pitch control is very light. My 
aircraft does not have a bob-weight on the elevator linkage, and I've been 
told that this would help.
	The above performance figures are observed values from my aircraft.  There 
are many 235 airframes with O-290's or O-320's in them, and the will 
obviously have better performance. Many recommend installing a larger tail 
when using the larger powerplants.  Hope this helps.
	All in all, I think the 235 is a great little plane, and was still the 
best choice for me.  I wish that Lancair would introduce a new kitplane 
that fills the niche that the 235 had once filled.  The Legacy is a very 
nice airplane, with more power, performance, payload, and room than its 
predecessors.  It is however a very expensive airplane.  If Lancair 
produced a kit for a 235 class airplane for $35K using some of the Legacy 
quickbuild construction techniques, and employing the 160 lb. Jabiru 120 HP 
engine (around $10K new), you could probably finish such a plane for around 
60k.  It seem with the emphasis on faster, higher and larger, that Lancair 
has conceded the affordable sport plane market to Rans.  If not for the 
235, based on cost considerations, I would have probably ended up with an 
RV 6  instead.

Tom Low

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