Hate to sound like a broken record, but a Turbo Commander will burn less fuel, go further, fly higher, carry more, in cabin class, and cost less to operate than a TBM.
Adam, don’t have SFC or specific air range tables for a TBM, but am I correct in suggesting that an AC690 is burning 500 to 600 lbs/hour for a KTAS of 250? The PC12 at FL280 is burning 300 lbs and motoring at KTAS of 230. (The TBM site suggests the 900 is burning slightly over 400 lbs/hour)
A TBM with less wetted area than both these types must surely be doing even better, perhaps not on a passenger seat basis, but then the PC12 must be the king of the roost in its commuter version?
Put another way the Garrett must be doing something interesting in the thermodynamics department to have a superior SFC on two engines to the PT6 single?
Even less. The -10 engined TC’s will burn 58gal/hr doing 290kts up high. That’s 388pph in total. The older models with -1’s and -5’s will do 54gal/hr doing 240-250kts, so that’s an even lower 360pph.
It’s because we don’t compare hp to hp and think two engines will burn “twice as much”. A PC12 is a 1200hp engine and because the PT6 is about 20-30% less efficient than a Garrett, it all adds up to about the same as the 2×840hp in the TC. A PC12 might get down to the same fuel burns in total up high, but it won’t be doing the same speeds. Probably due to drag, it’s a big and lumpy airframe. TBM is probably a little more efficient due to reduced drag. I would put it pretty close to a Garrett twin up high.
Here’s a shot of my friends old -1’s at 16000ft. 54gal/hr doing about 240ktas:
Wait until the CirrusJet arrives. Then the single engine logic will take full swing in the press. Only the to realize that the Mustang will probably burn less fuel. But we’ll see. I hope it does well for GA.
Adam might that be due to operating very light? Fuel flow is reasonably proportional to mass. 367pounds per hour is low, unless you were around 75% of your maximum all up mass.
Here is a typical charter operator specification table and he is quoting 470 pph, which seems close to the typical 500 pph quoted.
http://www.eagle-creek.com/wp-content/uploads/2010/09/Commander-Package-2013.pdf
This was in cruise, at 96% with 3/4 tanks, 3 persons on board and with the lower powered -1’s. Naturally, the cruise FF will be lower than an average over the flight. Yes, first hour with climb etc is probably around 500pph, second somewhere in between, and third you’re down to the quoted numbers of 380pph up high. In the link in previous post, he’s at FL340 in the example of 58gal/hr. Seems like the PC12 does about 68gal/hr, or 456pph, at FL280 doing 255kts, so it’s still a significant edge towards the TP twin, even though the FF at FL280 probably is a little higher. My guess around 60gal/hr.
RobertL18C wrote:
Fuel flow is reasonably proportional to mass.
It is? Mass will affect induced drag, but I would expect parasitic drag to be dominant at cruise speeds. Or does it work differently with turbine aircraft at high levels?
Fuel flow is more dependent on mass as you approach Vbg which is where jets cruise. Piston GA normally cruises way up the drag curve where the mass has almost no bearing on the fuel flow. I guess turboprops will be somewhere between the two?
Ben wrote:
Enjoy what ever you fly and don’t do the calculations, reality will take the fun out of your flying.
I agree. TBM900 is my dream airplane and it looks like I am no the only one. If they were 500 or 1000 EUR per hour, we’d all be flying them.
I calculated that buying privately, using it for leisure 50 hrs per year for 5 years and selling afterwards would be about 7000 EUR/h.
If one kept it for 20 years, fly 100 hrs per year and sell at 1M, cost is about EUR 2300/h.
I am sure there are mistakes in my calculations and owning with a company would help reduce the cost, but it doesn’t change the fact that it is a very expensive toy.
Details for 5 years at 50h:
Buy 4,2M (incl. VAT)
Service 0 (maintenance is free for first 5 years and there is 5 year warranty for most parts)
Fuel 71k (60gph at EUR 1,25/l)
Insurance 175k (at 1% value per year, decreasing value)
Hangar 30k (500 monthly)
Sell -2,7M (5 year old 850 are around that incl. VAT)
Total cost: 1,75M or 7000 EUR/h.
Details for 20 years at 100h:
Buy 4,2M
Service 380k
Insurance 540k
Fuel 570k
Hangar 120k
Sell -1,1M
Total cost: 4,7M or 2300 EUR/h.
Fuel flow doesn’t look very important in this scenario :)
Adam here is an ISA PC12 max cruise and long range table.
I have just been flying a P46T Piper Jetprop DLX at a dry flying price of 250 euro / hr. That is pure flying price (not block time) and excluding fuel. That price is better than the Cirrus SR22T for a similar trip.
As for price comparisons. It it all to do about price? Flying to me is priceless. Find something else that makes you the money and I don’t mind paying 10.000 euro per hour for a TBM to fly me anywhere I want.
I have just been flying a P46T Piper Jetprop DLX at a dry flying price of 250 euro / hr
That is definitely a real bargain. I think the usal price for a dry charter is at least twice this amount.
