On Monday, July 14, 2014 11:00:13 PM UTC-6, Morgan wrote:
Hi Bill,



Took me a little while to get back to this, but I've got two spreadsheets to share with you.



One is a pretty generic airplane cost that you'll probably look at and feel familiar with. It's one I got from someone, cleaned up and added a few formulas in order to make changing variables cleaner and easier when trying to assess costs.



The second is pretty old. How old? Well, Avgas was $4.10gal last time I updated it. It was $5.85 here when I fueled on Sunday.



In any event, it's not terribly pretty, but allows you to assess the cost across the number of tows each year. That one is the GenericTowplaneCost.xls file.



Between the two you can probably work out a reasonable cost structure to anticipate for providing tows. Our towplane has been great for our club, despite an early rebuild and some unexpected damage pulling it from the hangar one day. I think we've been turning close to $20,000 in tow revenue annually as of late and that is at relatively low tow rates thanks to volunteer tow pilots.



Towplane Operational Costs:

https://dl.dropboxusercontent.com/u/...tEstimate.xlsx

Morgan,

Looks like a reasonable spreadsheet. Not sure about recent years, but our Pawnee D (with 250hp STC) does about 300 hours annually, thus the cost is nearer $165/hour I believe. That includes engine reserve at $14.50/hour and compensation for tow pilots, $50/day plus $1.50 per tow, and $5 revenue. From that we set tow rates based on, IIRC, 5.5 2000ft tows per tach hour. Easily included in the spreadsheet. My numbers are mostly historical as I haven't looked at this recently. It's possible to run the O-540 well past 2000TBO, including a top end only about 3000. But that strategy doesn't always work and it's nice to have $erviceable core$.

Tow planes operating in the high country don't make full power and the fuel 'cools' the temp somewhat. Not uncommon to go way beyond the TBO, but risky over 4000 hours with the O-540.

Nearer sea level, cracked jugs are more common due to higher power and more thermal shocking. Thus the engine reserve rate needs to be higher.

YMMV,

Frank Whiteley