From: yiannis@ccad.uiowa.edu (Yiannis Papelis)
Subject: Certification of Light aircraft (was Las Vegas->Chicago Race)
Organization: CAD-Research, University of Iowa, Iowa City
Date: Wed, 9 Sep 1992 17:02:43 GMT

In some article blh+@cs.cmu.edu (Bruce Horn) writes:
>In addition, Neico Aviation is planning on certifying both the Lancair IV
>and Lancair ES.  This information confirmed by Sport Aviation (and hopefully
>not just wishful thinking).

I have some comments and questions about homebuilts, 
the certification effort, especially regarding cost and 
performance of these aircraft.

First some generally ad-hoc observations.  

One of the most attractive features of the high performance 
homebuilts (HPHBs) has been performance.  I'm not very good 
with remembering numbers but the retractable gear 
lancairs/glasairs/various canards/cirrus
are 4 place aircraft which by using 180-250 hp engines reach speeds 
well into the 200 mph range, and by using 300+ hp engines get speeds
close (or over) 300 mph.  Fixed gear designs are generally within
the 200 IAS range using 200+ hp.  (These numbers are approximate)

I don't think there are any RG singes that can reach the 300 mph IAS
but the high end mooneys and bonanzas are definately within 
the 200 mph range.  Given the assumption that the price of production 
aircraft contains a large percentage of liability cost in them, one
would expect that homebuilts, given the capability of using newer 
materials/airfoils without worry about liability could offer
better performance with much lower price.

But after looking closer to the specs and performance numbers of
some of the homebuilts I have noticed two characteristics shared by
most of them:

  Stall speeds in HPHBs are high, >75 knots, and
  often not even specified.  That translates, and that is PERSONAL
  opinion, to higher wear and tear due to higher touchdown speeds,
  increased risk in case of an engine failure (a while ago, in a rec.aviation
  thread there was talk of the high glide speed > 100 mph of a HPHB).

  HPHB have unspecified stall behavior.

Overall then, the question is, if we were to compare homebuilts 
according to the same criteria used for certificated aircraft, are 
homebuilts really better?  Stall speeds can be reduced by 
modifying the airfoils, which will generally reduce performance.  
Elaborate flap systems can be used but cost will
increase.  Regarding unspecified stall behavior, extensive testing ($$)
can provide answers but cannot fix a badly behaved A/C.  

It just seems that after some equalization, the costs are very similar.

While at OSH, I talked to the Lancair people about the ES and 
especially their certification effort.  Again, I don't remember 
the exact numbers, (feel free to set me in line if I'm wrong) 
but what I gathered from the conversation, is by the time the 
'tamed' the airplane, its performance became comparable
to an RG production A/C, ~150-160kts, low stall ~60 kts.  
When cost came around nobody would even talk about the projected 
cost of a finished kit but by the time you add instruments, engine, 
interiors, factory profit etc, and calculating labor for 
a 1000 hour construction, you come up with some fairly steep numbers.
And it is a two place A/C.
Even if it were 'somewhat' cheaper than a certificated A/C, the price
difference is not that much, to many people there is no difference
between a $100,000 A/C and a $130,000 A/C, both are out of reach.

So the question is, are homebuilts that hot or is it generally that 
they can trade features (i.e. stall speeds, stability etc.) with 
performance, something that certificated A/C just can't do?

Any comments, corrections, ideas ???
-- 
Yiannis E. Papelis,            - Electrical & Computer Engineering, U of Iowa
Center of Computer Aided Design- Home of the Iowa Driving Simulator & future
e-mail: yiannis@ccad.uiowa.edu - home of the National Advanced Driving Simulator