On Mar 8, 3:23*pm, Martin Gregorie
wrote:
On Sun, 08 Mar 2009 14:29:37 -0700, brianDG303 wrote:
I'm struggling with a similar question, and it relates to rebuilds. I
guess different rebuilds cost very different amounts, and it seem that a
Pawnee rebuild is $35K and a little more. Could it be that a cheaper to
rebuild tow plane could be a better choice?

Seems to me that you need to total up several factors:
1) The cost of replacing/rebuilding the tow plane
2) The cost of insuring the replacement for the time you'll keep it
3) The total operating cost for the time you'll keep it, i.e. include
* *both overhauls/part replacement as well as fuel and oil.

Then calculate the total cost per annum of each course of action.

--
martin@ * | Martin Gregorie
gregorie. | Essex, UK
org * * * |

SO let's make it an even dozen.

Some other things that apply to all choices (including the Pawnee...)

4) who will maintain the tow plane, what experience on type/model do
they have and how many others doing similar things are available to
learn/get help from?
5) Vendor/product risk - a risk factor for chance the vendor will go
out of business or there will be a nasty AD etc. (yes nastier than the
spar mounts on Pawnee, and yes this risk applies to Pawnees etc. as
well)
6) Parts risks/costs - for some models where the vendor is no longer
making them, what is the risk parts won't be available, will be hard
to find or will be expensive to fabricate if at all possible? (And yes
this risk applies to Pawnees etc. as well, but is reduced somewhat by
their wide use)
7) Operational limitations - find out how whatever you are looking at
tows on the days you need to, on the surfaces, at the temperatures and
density altitudes etc. (e.g. more than a few motor gliders have
cooling issues when it gets hot outside).
8) The expected TBO of the engine - I'd be pretty cautious about
assuming anything based on published TBOs - in general and especially
if the motorglider is towing. I'd go talk to real owners who have been
doing something similar. I have a lot less confidence in the engines
in some of these motorgliders doing as well there say compared to a
Lycoming in a Pawnee - but that is just my bias, unconfirmed by
reality either way. Bear in mind that with towing you may be putting a
lot more time on the engine than others so you'll be the canary in the
coal mine.
9) The utility at all of the motorglider as a XC glider/training
glider (you may just maintain it as a tow plane).
10) Insurance costs, pilot experience requirements and other issues. I
have no idea there, but I'd be calling my insurance agent early on in
the process (like now). Especially if some of the desire is to get
glider pilots with a motorglider endorsement towing - I cringe a bit
at that unless those folks have some power experience and/or a lot of
time in the motorglider.
11) Experimental category issues (if it's an experimental motorglider)
in the USA - I'd expect you would run into issues towing with
motorglider with an contest and exhibition certification.
12) You need to know that a tow release system is available or what
one involve/will cost to put through as a 337 only (if the FSDO would
do that?) and what issues that involves. One of the appeals of the tow
setup on many Pawnee's is the retractable tow rope. I'm guessing there
may not be space to install that in many motorgliders.

Anyhow just more brain food.

Darryl