To be realistic I assume a ten year ownership horizon. This would cover one set of engines overhauled, two prop cycles, two vacuum pumps, heater and hoses twice, some random ADs, some avionics. If the aircraft is parked what is saved in hangar age is spent on airframe maintenance. At today’s prices these perishables work out at around £100k, or £10k p.a. This estimate is on the low side, so best case.
Annual maintenance at one annual and one fifty hour (implying 100 hours utilisation), with the usual rectification item(s) – other perishables, avionics maintenance, undercarriage items (seals etc), might average £10k, with a s.d of £2k and kurtowsis on the upside.
Insurance comes in at £3k with a relatively low hull value. Hangar at around £6k in a metropolitan area.
Before turning the props call it £30k, or £20k before funding reserves. First hour is typically 110litres, then 80litres at best economy with Gamis and engine multi probe analyser. On a two and a half hour sector, say 90litres per hour. Airways costs £40 per hour, and for each sector you have twin airport charges, say £10 per hour at VFR airports.
All in cost for 100 hours per annum and £1.7 per litre Avgas, ca. £500 per hour.
A more modest twin, say a Seneca 1, which is sub two tonnes, and runs at 70 litres per hour block, and has four fewer cylinders, might be closer to £400 per hour.
This assumes you bought cheap and you sell cheap, the latter almost a certainty, so essentially a wash. Although you might recoup £15-25k of your overhaul investment if you bought a run out and sell it as a half time left aircraft.
The above does not include a bunch of other stuff which might need rectification. e.g. compass slaving system, autopilot, .833 kHz upgrade, recurrent training, boots, pads, wind shield de iced, hard to get airframe items (eg flap actuating rods, under carriage items) which need replacing because, well they have been AD’d or wear out.
Note these are normally aspirated, unpressurised twins. Regular flight above FL180 results in higher engine maintenance for Pistons. Or put another way the Duke’s Lycoming -540 is expected to put out 380hp compared to the same displacement in the Aztec at 250hp.
Is this a question ?
At any rate, I maintain a few piston twins, some under and a couple over 2T.
IMHO AND based on real & first-hand experience, your £10K pa for Annuals and another for “perishables” not covered in the Annuals, to be way over the top for this class acft..
I maintain 2 Cessna NA 310s, they are > 2 metric tons. Annuals come in at half your figure INCLUDING those “persihables” you mention.
Both Hangar & Insurance is significantly less, at least on the Continent it is.
I say your figures are easily 30% over what my clients are experiencing.
Michael, sounds like you aren’t charging enough!
I can rent a DA42 FIKI for 400€/hr. Just saying.
I can rent a DA42 FIKI for 400€/hr. Just saying.
Which would include servicing the loan and/or depreciation of a multi-hundred-thousand £ acft as well as the insurance premium to cover the hull and every Tom,Dick & Harry with a PPL that rents it !
Regular flight above FL180 results in higher engine maintenance for Pistons
Can you elaborate on the factors behind this? Cooling? Turbos? Pressurisation? Why is 65% power at FL90 harder on a piston engine than 65% power at FL180?
RobertL18C is spot on with the costs. I have operated a Piper Aztec MTOW 2359kgs for several years, now on my second one after running out the engines on the first, and the average annual is £10k with operating costs of just over £500 per hour assuming 100hr per annum. Not at all economic but a lot of fun to fly.
Can you elaborate on the factors behind this? Cooling? Turbos? Pressurisation? Why is 65% power at
FL90FL180 harder on a piston engine than 65% power at FL180FL90?
[I am assuming you meant it the other way round – as the statement was. Sorry if I misinterpret]
More time at high power to get there in the first place, with increasingly worse cooling as you get higher, is probably the main culprit.
Higher CHTs at same power while you are up there, although at 65% probably not much of an issue. On the way down: it all depends on if you believe in shock cooling.
FWIW: In the Columbia 400 speed was TIT limited on warm days at high altitudes, in the SR22TN CHT-limited. In both cases (lean of peak) the response was to lean a bit more, which at that point of the mixture curve reduced power a bit and brought things back nicely.
In the Columbia 400 you also had the option to fly ROP, which turned it from a reasonable 17.5 GPH into a ravenous monster drinking 24 GPH pretty much at the same speed.
Yes, sorry, typed that the wrong way around.
I would have thought that the extra high-power -to-climb time should be the only real factor here. Slightly higher CHT once at altitude shouldn’t really be a factor in engine maintenance, if within limits? But difficult to prove either way.
I have operated a Piper Aztec MTOW 2359kgs for several years, now on my second one after running out the engines on the first, and the average annual is £10k with operating costs of just over £500 per hour assuming 100hr per annum.
Care to share your costs spreadsheet for G-BJNZ with us John ?