6cyl CS prop operating costs?

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asicer

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asicer
I was going through some old files and came upon Ron Levy's paper on ownership costs. In it, he posits that non-calendar maintenance (i.e. oil&filter, mags, vacuum pumps, non-major repairs due to wear&tear, etc but not including annual/pitot/static/transponder/ELT checks) should be about half the cost of fuel per hour for a fixed gear fixed prop 4cyl. For example, an Archer/Tiger/172SP burns about 10GPH and fuel is about $5/gal so I should budget about $25/hour for a maintenance reserve.

That got me wondering. What's the multiplier for a big bore 6cyl with a constant speed prop? Does half the cost of fuel per hour rule still hold?
 
I never subscribed to the maintenance reserve because the engine could crap out tomorrow or could go another 3,000 hours so do I put in a hourly cost of $40,000 or $13?

Basically if you buy a plane have money ready for an overhaul tomorrow. My dad bought a 0SMOH engine and had to have it OH at 200 hours. (Long story not his fault)
 
It’s all reading tea leaves.

Just pay for consumables (gas etc) understand how much a jug, mag or OH costs and go from there. Mx reserves are kinda sillly, some engine go a few thousand past OH, some pop with only 100TSMO, just stay on top of mx, don’t be ham fisted, have a good engine monitor, put gas in and have fun.
 
Turbo or normally aspirated? And there is less maintenance required when gas is cheaper, is that because in theory you’ll fly more?


Tom
 
The relationship may be a good accounting trick for forcing yourself to save for maintenance if you're incapable of saving for it on your own accord, but mechanical expenditures certainly hold no empirical relationship to fuel consumption to the degree that a little formula can model it. On that merit alone the use of fuel use as a metric is garbage. As others have already alluded to, throttling back your use of the airplane to lower hours will not have an impact on the probability of still having a mx failure on the subsequent hour you fly. Thinking it does really sets you up for disappointment in ownership imo.
 
Are you guestimating operating cost to guide a purchase decision, or are you actually thinking of reserving for routine maintenance.

When I was a flying club treasurer we reserved $18/hr for the engine funds. We did not reserve for routine maintenance. That was always paid from regular dues.

Things like engine AD's or SB's were complied with using engine fund, but oil changes and most other fixes did not.
 
Rough numbers on a 182: we budget ~120/hr for opex (including all non-annual mx), figure gas is about 70/hr at 12gph, so that leaves 50/hr for oil/mx/etc, so in our case the multiplier would be more like .7 than .5. Makes sense that it needs to be a smidge higher since you need to budget for the prop in addition to the engine.
 
I spent around 2,000 hours of flight time running constant speed props on piston twins (so figure 4,000 hours of prop time) between the Aztec, 310, and 414. My opinion is that it's pretty bipolar. On the Aztec and the 310 I spent virtually $0 on the prop costs. The Aztec I had to replace the heating boots on the props, and at one point the spinner backing plate had to get replaced but that can happen on any plane. So, basically $0 reserve there.

On the 414 after 75 hours of operation one of the (20 year since overhaul) props started leaking the evil red dye. Being old threaded-hub McCauley the options for replacement were limited, and the props were rotten performers that had a lot of negatives. So long story short, we went with the MT STC options, which was a fantastic improvement for the plane.

The real thing is that the bigger the plane and the more complex the systems are, the more the bipolar factor comes in. So on the MU-2 the engines are essentially free until an HSI comes up ($30-$100k is the general range) or an overhaul (which I haven't researched much, but generally $200-250k range). Those can be budgeted for, but you really need to be budgeting for those from new to have the appropriate amount of time. And if the engine grenades, now you're talking about an instant $200-250k probably, depending).

The general adage I've found for a piston aircarft is you should always be in a position to replace the engine if you have to. If you can do that, then you can probably handle about anything else that comes along.
 
Ok, let me rephrase the question (maybe this is what I should have asked in the first place). Let's say I had a C182, an M20F and a V35. Hangar, inspections, insurance, taxes and GPS databases are all taken care of. What's a good dry tach rate to charge a family member for a non-equity partnership and still expect to remain family?
 
depends....if nothing breaks....something around $100-150/hr dry. If something big breaks....it won't matter....it won't be enough. :D

just add up your fixed yearly costs and add in engine costs. Without engine costs I can get to $6,500 easily. Divide by 100 hrs of flying....and that's a starting point.
 
Checkout_my_Six said:
depends....if nothing breaks....something around $100-150/hr dry. If something big breaks....it won't matter....it won't be enough. :D

just add up your fixed yearly costs and add in engine costs. Without engine costs I can get to $6,500 easily. Divide by 100 hrs of flying....and that's a starting point.
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That's on the Bo? Or all 3?
 
asicer said:
Ok, let me rephrase the question (maybe this is what I should have asked in the first place). Let's say I had a C182, an M20F and a V35. Hangar, inspections, insurance, taxes and GPS databases are all taken care of. What's a good dry tach rate to charge a family member for a non-equity partnership and still expect to remain family?
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$45 an hour.
 
asicer said:
That's on the Bo? Or all 3?
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should be about the same on all 6 cylinder's...

Ins......................... $1,500
Annual insp no maint...$2,000
hangar.....................$3,000
...........totals...........$6,500/100hrs as a starting point for any of your choices.

engine and prop fixed costs.....$55,000/1,800hrs = $30/hr

then add in variable costs.....oil and stuff that will break.
 
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asicer said:
So basically you are saying "screw the family member"? ;)
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yup.....It's all good till something breaks. Then your hourly model falls apart.

If it's someone who knows airplanes and you want to help out....let them fly it and have them kick in what they want. I wouldn't charge my dad or grand D....meh, maybe I'd charge a brother or cousin.


but, that's me.......none of this stuff works out like it does on paper.
 
Checkout_my_Six said:
If it's someone who knows airplanes and you want to help out....let them fly it and have them kick in what they want. I wouldn't charge my dad or grand D....meh, maybe I'd charge a brother or cousin.
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That's more or less the situation. Thinking of helping out a cousin and wondering what is reasonable.
 
asicer said:
That's more or less the situation. Thinking of helping out a cousin and wondering what is reasonable.
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You cold probably just charge $50/hr and they buy fuel on top of that. That way, they carry their own insurance and you can eliminate the fixed costs like hangar/group insurance out of the rental rate since you'd be paying that cost anyway. Otherwise, you're just charging him a fully-loaded rate, at which point he may as well become an equity partner.
 
If you charge anyone to use your plane (beyond just the fuel and oil consumed) are you subject to 100-hour inspections?
 
Checkout_my_Six said:
and that would require kicking in much-much more.....
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Sure. I was just making the point that if he is trying to do his family member "a favor", I don't think offering him a fully-burdened rental rate is going to be of much service. He could just rent something from a true rental outfit at that rate. If he just wants to toss $50/hr for usage of the aircraft and buy his own fuel, I'd think that would be sufficient.
 
Wow. The guy asked a simple hypothetical question. Give him a break. It’s not a value judgement on how much he should spend on a plane or whether he can afford it.

The .5-.7 multiplier seems reasonable. I’ve been lucky so far but have had a few maintenance issues pop up. That amount of reserve would probably have given me some amount of cushion on my 182RG but I’ve only had the plane for a few years.
 
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