Cost of Operation
Nov. 2010 I now have put another 100 hrs on the MX7-160. The engine has been running great. We are
working on replacing other maintenance items such as a worn throttle cable. Over all this 160 hr. stripped down
"Sportplane" should be an economical airplane to operate. I have been quite surprised with the performance. The
airplane is 250lbs. lighter than my M6. Therefore the stall speed is less so I can land slower and shorter. I have
the standard climb prop so I only cruise at 105 mph, but on climb out with me and 40 gals of fuel, 4000ft DA I get a
climb of +1000 ft/min. Take off with 180lb. pilot, 25 gals of fuel, DA 3500 ft, no wind = 300 ft ground roll.
Nov. 2011 One year and 300 hours later. I guess I shouldn't have used economical and airplane in the same
sentence. I started setting aside $25.00 per hour for maintenance needs of the MX7-160.. I later went to $35.00
and now $40.00 per hour plus $10.00 per hour engine reserve. Over the year I added extended tanks which is
an upgrade not routine maintenance but you still need to set aside money for such items. I did have to replace a
cylinder because the valve guide came lose in the head, Why? I don't know. ( 750 hrs. on a new Millenium ) Most
every thing else was general wear and tear.
Dec. 2012 Just finished another 100hr./ annual on the MX7-160. Nothing major to report. I did upgrade the ELT to a 406 type. Other expenses over the year included - Fine wire spark plugs ($49.50 ea), new mags and harness ($1900.00),
replaced the front floor boards, installed the new type of tank vents. I have flown N10240 a little over 200 hours
this past 12 months. Setting aside $40.00/hr. I have about $400.00 surplus for the 2012 calender year and
$800.00 in the checkbook since we started setting money aside. I have also set aside $10.00/ hour for engine
The one expense I now see I haven't planed for is a recover/paint job. At the present a good quality job will be in
the $20,000.00 to 25,000.00 range. If you don't care about looks you can expect the modern covers to test good
for 30 years or more but the structure underneath may need work before that. Most of us don't keep an airplane
for 30 years. The recover cost is should be taken into account at the purchase of the aircraft. This is one cost
that can be devastating to aircraft ownership if you aren't prepared for it.
Jan. 2013 This being tax preparation time I decided to look at the operation expenses of my M6. I had airframe
and engine overhauled in 2005. So now I have 7 years and 1800 hours on the airplane. During that time some of
the major expenses - prop overhaul ( I run part 135), replaced 5 cylinders (it was a cheep overhaul and used
rebuilt and welded cylinders), new mags and harness and new exhaust system. So all that plus annuals, oil
changes and regular maintenance - $26.69 per hour. Now of course that doesn't include buying 31" Bushwheels,
auto fuel STC and wing mod, etc. All those I consider optional not true operating expenses but should be factored
in to your calculations. Since I run part 135 I will need to replace the engine at 2000 hours. I have looked into
what a factory reman with new hoses, ducting, engine mounts,etc and installation would cost. Looks to be in the
$35000.00 range which means $17.50 / hour. Now yes with a good core I can get by for less but I'd rather plan for
the high for the worst case.
May 2013 Not again! I had to make a precautionary landing in my MX7-160 when I was out on a pipeline patrol.
Luckily I was over the flat farm land of central Montana and taxied up to a farmstead. I had no compression on
one cylinder. After removing it I found the valve guide had come loose in the head and had broken into pieces.
The same thing had happened in Nov. 2011. (See above) This was a different cylinder. (1000 hr. SMOH) I
started to see a pattern here. When I got the airplane back to Cut Bank we pulled the other two cylinders. With a
small hammer and punch we could tap out the other valve guides! We sent all four cylinders in to ECI. After they
inspected them they didn't say there was a problem, but they sold us new cylinders for $300.00 ea. We split the
case again to clean out the debris in the oil sump and replace bearings. Things are now back together and
running fine. We'll see how things go from here. That's now twice I've had to tear the engine down because of
problems beyond my control. What will be next?
Mar 2015 I have now installed my overhauled O-540 in my M6. The base price for the work was a little under
$26000.00. Since this was not the first overhaul on this engine I needed to replace some gears in the accessory
case. That was close to $5000.00 for serviceable replacements. After the added expenses of removing
,shipping,reinstalling, new baffles, engine mounts, new ducting,etc. the price is around $33500.00.
Jan. 2016 A year ago it looked like I could get by putting $20.00 an hour aside for regular maintenance in the 160hp Maule. I haven't had any other major engine problems since installing the new cylinders. After I pay for an annual the check book will be back close to $0. At that amount it leaves nothing for up grades in avionics or airframe upgrades. I'm going to start setting $30.00 per hour aside for maintenance.
Feb. 2018 I've decided I need to put aside $40.00 per hour for general maintenance for the MX7-160. After ten years of ownership I've have less than $800.00 in the account and I have an annual coming up in two months. Not much of a cushion! Looking back over my expenses from 2014 -2017 on my M6-235 I see I have spent $60.00 an hour on general maintenance. That's with a usage of 150 hours per year. I also need to set $20.00 per hour aside for engine and prop overhaul.
Author Rick Geiger
I bought my first Maule in 1993. Over the years the aircraft has proven to be rugged and reliable. I have learned a few things along the way that might help you avoid some of my mistakes and expenses of owning and operating an aircraft.