Maintenance Cost Formula

[joefremont]

Right now the maintenance costs of an aircraft are based on a percentage of its market value. This can produce some unrealistic numbers especially when dealing with older out of production where the real world market value is very low compared to current production aircraft. Often these aircraft have a very low market price because the maintenance costs are so high, where flynet reverses this, where the newest aircraft with the lowest maintenance costs are penalised because of there high purchase price. I would therefore propose the following change to the maintenance calculation.

Instead of using the market value to calculate maintenance cost, we would calculate a 'maintenance value' that would be based on the dry weight of the aircraft (larger the aircraft the larger the cost) the formula would be.

500v$ per KG of the aircraft's dry weight
+10% per engine.
+5% per engine if piston powered (not turbines).
+10% if no longer in production (alternate +1% for each year since production stopped).

Some examples, for two aircraft of about the same weight)

A320, current production two engines, market value is 61m, using this formula the maintenance value would be 25.3m and an A level check would be 759.000v$ rather than the current 1.830.000v$.
B727-200, not in production three engines, market value 40m, using this formula the maintenance value would be 63.5m and an A level check would be 1.9m rather than the current 1.2m.

Another comparison would be the DC-3, current market price 300.000v$ an A level check is 9.000v$. Using this formula
(8030kg * 500v$ * 1.4 two piston engines plus out of production) a maintenance value of 5.621.000v$ so 168.630v$ for an A level check. Of course this could lead an airline to conclude its cheaper to scrap an airplane than fix it, which happens some times in real life.

Now I am running an airline with primarily old propliners so I would be hit by this change but I still think it would be more realistic.

[CAPFlyer]

I think this is a good solution to the cost calculation side of it. Tie this with the time-based maintenance instead of percentage-based, and then we'll have an MX program that makes the costs much more reasonable (although an A-check in real life for most planes only costs a couple hundred dollars for topping off the oil and nitrogen to top of any low tires).

[cmdrnmartin]

All I really see is this lowering the maintenance value across the board...

747-400 Maintenance Value:
125 129 200

Actual Price of AC: 200 000 000

So you've halved the A-check price.

It gets worse when you work with two engined aircraft, the cuts in price are steeper. As well, remember are 'a-check' is that in name only, since our planes can go as low as 95% and still only require the a check. Not enitrely realistic, but its a workable system.

My fear in doing this new method is that it simply makes it even easier for people to make money, a fear I believe you share with me capflyer. The big crunch on ioncome has been fuel. people flying with the old planes, dont make more than the new planes because in general the old planes gulp gas and dont hold as many payuing passengers. Making it even harder for people to use the vintage aircraft, is in my opinion, stupid.

Comments?

[joefremont]

The point of what I am suggesting is that the maintenance cost of an aircraft should not be linked to its market value. For aircraft of about the same size the relationship would often be inverse of each other. Think of your own car, as its market value goes down due to depreciation, your maintenance costs do not go down also, they probably go up.

Its also true that two engine aircraft would have lower costs than larger aircraft, but this is true in the real world also, which is why the majority of new offerings by Airbus and Boeing are two engine aircraft.

Now the factors can be adjusted to so that the average remains the same as today but in general new aircraft and two engine aircraft would be lower, old and four engine aircraft would be higher. And those bargain relics would be a lot higher.

[cmdrnmartin]

The point of what I am suggesting is that the maintenance cost of an aircraft should not be linked to its market value. For aircraft of about the same size the relationship would often be inverse of each other. Think of your own car, as its market value goes down due to depreciation, your maintenance costs do not go down also, they probably go up.

Its also true that two engine aircraft would have lower costs than larger aircraft, but this is true in the real world also, which is why the majority of new offerings by Airbus and Boeing are two engine aircraft.

Now the factors can be adjusted to so that the average remains the same as today but in general new aircraft and two engine aircraft would be lower, old and four engine aircraft would be higher. And those bargain relics would be a lot higher.

Actually, two engines are offered because they are more fuel efficient. It took a while because manufacturers had to get some pretty hefty ETOPS ratings to get there planes certified and flying with the airlines, but it has been shown that they really are better and longer legged.

Heh, and about your maintenance issue, a DC-3 is incredibly rugged as an aircraft, you can pour all types of crap into its engines, and it will still run ok. Compare that to thos pissy RR engines with their overly complicated contra rotating compressors? Thats a real maintenance hassle. As well, if you have a problem in say, the control of the rear elevator in a 707, and the control of the rear elevator in an A321. The 707 will require a tighteing of the control wire, or some other relatively simple fix. the A321 will probably take a long time just to find the fault in the system, then a while to dig through code, etc to fix it. It's simple to clen the gunk out of a piston engine, a bit harder to precisely balance and reduce rotational shift on a turbofans primary shaft.

I'm just saying, your idea, with good intention, unfortunately only makes it easier to make money, and pushes people even further from worthy classic aircraft.

[joefremont]

I'm just saying, your idea, with good intention, unfortunately only makes it easier to make money, and pushes people even further from worthy classic aircraft.

Look at the simple economics, the market value* of an aircraft is directly related to the profit it can generate, ((Seats * ticket price) - (fuel cost + maintenance cost)) * the number of flights a day it can make * some constant = market value.

Since FlyNET does not take into account aircraft speed in ticket price or how many hours are left on the airframe, assuming you have enough pilots, you will make far more money with a fleet old propliners than you will with one modern big jet.

* = Note: Market value is not nessesarly the same as market price.

[cmdrnmartin]

I'm just saying, your idea, with good intention, unfortunately only makes it easier to make money, and pushes people even further from worthy classic aircraft.

Look at the simple economics, the market value* of an aircraft is directly related to the profit it can generate, ((Seats * ticket price) - (fuel cost + maintenance cost)) * the number of flights a day it can make * some constant = market value.

Since FlyNET does not take into account aircraft speed in ticket price or how many hours are left on the airframe, assuming you have enough pilots, you will make far more money with a fleet old propliners than you will with one modern big jet.

* = Note: Market value is not nessesarly the same as market price.

No you won't.

Fuel Burn is much higher, for carrying less passengers. Try flying a 707-320 transatlantic, then fly an A332. They fly roughly the same, but the 707 will take most likely about 1/3rd more gas, and carry at best, 1/2 the number of passengers as the A332. Thus, to make it fair, the older planes are sold at lower prices.

And you still havnt addressed the fact that your formula makes it even cheaper for the big new jets. Trust me, I was around for the multiplier wars, and the decision was to base the system around having a small basis in reality, slow expansion at higher levels (to allow for larger airlines etc, when they come). It just seems stupid to penalize even further the jets that almost no one flies. Albatross excluded.

And David now that I think about it, with his MD-11s, not that their old, but with 3 engines, hes going to be hit even harder if this rule goes into play.

Anyways: Fuel is how we control the market, the clunkers are there to allow for startups to have trans oceanic ability, if they want to sacrifice pax loads and thus income in the long run.
Making it even easier for the twinholer crowd is not sound judgement. And Im saying this as an airline who flies only twin holers.
I liked maintenance the way it was before the A-check system. I like it now, depsite it costing me a bit more sometimes. I would not like it if it got even easier.

Cheers,

[joefremont]

Hi Martin, you brought up two issues, realism and playability.

And you still havnt addressed the fact that your formula makes it even cheaper for the big new jets. Trust me, I was around for the multiplier wars, and the decision was to base the system around having a small basis in reality, slow expansion at higher levels (to allow for larger airlines etc, when they come). It just seems stupid to penalize even further the jets that almost no one flies. Albatross excluded.

On this issue I am inclined to agree with you. From a game play stand point starting off with the old clunkers and building from them a large airline modern airline would not be possible if the econimic system was really relistic. Right now my fledgling startup is using DC-4's between SFO/LAX and given the cost of the AC I am getting pretty good revenue from it and should soon have enough to start getting some more modern aircraft. In the real world the fact that my planes are slower, noiser and have much higher maintenance costs would not make this possible, which is why in the real world so few of these AC are still in use. As long as we all understand that its not truly a "realistic economy system".

Fuel Burn is much higher, for carrying less passengers. Try flying a 707-320 transatlantic, then fly an A332. They fly roughly the same, but the 707 will take most likely about 1/3rd more gas, and carry at best, 1/2 the number of passengers as the A332. Thus, to make it fair, the older planes are sold at lower prices.

This is really not a fair comparison as the two AC are separated by about 40 years of technology and engine development. A more fair comparison is the A330-300 and the A340-300, both aircraft have the same body and wings but the one is twin engine and the other is four engine and the rate of fuel consumtion between the two is very close. If you were to compare the A332 to the 747-400, it would come out the looser. Based on numbers from the boeing and airbus website.

B707-320: 141 passangers * 9,913 km / 90,290 l fuel = 15.5
A330-200: 253 passangers * 12,500 km / 139,100 l fuel = 22.7
A340-300: 295 passangers * 13,350 km / 140,640 l fuel = 28.0
B747-400: 416 passangers * 13,450 km / 216,840 l fuel = 25.8
A380 : 550 passangers * 15,000 lm / 310,000 l fuel = 26.6

Granted aircraft with longer ranges will get much higher scores on this test as a lot of fuel is used in takoff and getting up to cruise altitude and there are lots of other factors that can effect fuel used per passanger mile but you get the genral idea. Airlines prefer the twins more because there are fewer parts to maintain and there are fewer things that can break, twice as many engines means you are twice as likely to have an engine failure.

I hope my comments have been of some use.

[cmdrnmartin]

Hey Joe,

I think on the second point you misunderstood my argument, i was just pointing out that an old clunker will not make the same amount of cash that a new plane makes.

The airlines like two engines because of the fuel efficiency. Sure, twice as many engines means more chance for something to break, but it also means you can survive the loss of one engine. Under current rules, if a twin loses an engine, there is no question about what is to be done, they WILL be diverting to the nearest alternate. A four engined bird, while less fuel effiecient, is allowed to continue on to its destination on 3 engines.

But again, the 747 to A330 is an unfair comparison. 777-300ER to the 747-400, thats a better comparison.

Anyways, for FLYnet purposes, just remeber the 'general' realism principles we apply to most of our modeling.

Cheers,

[HS1]

It just seems stupid to penalize even further the jets that almost no one flies. Albatross excluded.

The old birds are the best birds! The question is, to what extent does that apply? I'd say the maintenance system is fair enough and economical enough for all planes; striking a reasonable balance between realism and simplicity.

[joefremont]

Hey Joe,
I think on the second point you misunderstood my argument, i was just pointing out that an old clunker will not make the same amount of cash that a new plane makes.

Maybe I was misunderstood in my argument that clunkers will make more money than a new jet. Here is a comparison based on some data on two recent flynet flights out of SFO. Common assumptions, fuel cost = 1.18, salary = 10%, Multiplier = 500% and each airplane gets an A-Check every 10 flights.

The first flight is a DC4 from SFO to LAX with 70 pax and no cargo income, 1033kg fuel used, net income for the flight is 2,179,000v$. Second is a 739 from SFO to SAN with 177 pax, 12042v$ from cargo and using 3515kg of fuel used, net income for the flight is 11,583,000v$. Now you might think this proves your point but wait, the DC4 has a market value of 500,000v$ so the return on investment for this one flight is 435%, the 739's market value is 66,000,000v$ so is ROI is 17.5%.

The airlines like two engines because of the fuel efficiency. Sure, twice as many engines means more chance for something to break, but it also means you can survive the loss of one engine. Under current rules, if a twin loses an engine, there is no question about what is to be done, they WILL be diverting to the nearest alternate. A four engined bird, while less fuel efficient, is allowed to continue on to its destination on 3 engines.

I will concede that on older jets larger engines were more efficient than smaller ones, hence two large engines would use less fuel for the same thrust as four smaller but on newer jets engine designs that not as true, note the rise of small regional jets in recent years. But the size of an engine really does not effect how much time it takes to maintain them, although the parts will be smaller and therefore cheaper. Take a look at this table for GE turbofans http://www.geae.com/engines/commercial/ ... bofan.html. Note the ratio for "Specific Fuel Consumption at Max Power", you will note this ratio is not dependant on the max thrust of the engine.

Theoretically a four engine jet should be more efficient since an AC needs enough extra power to continue to fly less one engine, a 2 engine jet needs 100% excess power and a 4 engine jet only needs 33% excess power, but I don't think we are going to convince each other on this point. My original idea was that maintenance costs should not be based on market price since AC with real world high maintenance costs would have lower market prices, even if we just said the maintenance costs were based on dry weight and nothing else, it would be more realistic.

But again, the 747 to A330 is an unfair comparison. 777-300ER to the 747-400, that's a better comparison.

I wont argue with that, but its not as unfair as comparing an A330 to a B707.

I think we have beaten this topic to death.

[cmdrnmartin]

Hey Joe,
I think on the second point you misunderstood my argument, i was just pointing out that an old clunker will not make the same amount of cash that a new plane makes.

Maybe I was misunderstood in my argument that clunkers will make more money than a new jet. Here is a comparison based on some data on two recent flynet flights out of SFO. Common assumptions, fuel cost = 1.18, salary = 10%, Multiplier = 500% and each airplane gets an A-Check every 10 flights.

The first flight is a DC4 from SFO to LAX with 70 pax and no cargo income, 1033kg fuel used, net income for the flight is 2,179,000v$. Second is a 739 from SFO to SAN with 177 pax, 12042v$ from cargo and using 3515kg of fuel used, net income for the flight is 11,583,000v$. Now you might think this proves your point but wait, the DC4 has a market value of 500,000v$ so the return on investment for this one flight is 435%, the 739's market value is 66,000,000v$ so is ROI is 17.5%.

The airlines like two engines because of the fuel efficiency. Sure, twice as many engines means more chance for something to break, but it also means you can survive the loss of one engine. Under current rules, if a twin loses an engine, there is no question about what is to be done, they WILL be diverting to the nearest alternate. A four engined bird, while less fuel efficient, is allowed to continue on to its destination on 3 engines.

I will concede that on older jets larger engines were more efficient than smaller ones, hence two large engines would use less fuel for the same thrust as four smaller but on newer jets engine designs that not as true, note the rise of small regional jets in recent years. But the size of an engine really does not effect how much time it takes to maintain them, although the parts will be smaller and therefore cheaper. Take a look at this table for GE turbofans http://www.geae.com/engines/commercial/ ... bofan.html. Note the ratio for "Specific Fuel Consumption at Max Power", you will note this ratio is not dependant on the max thrust of the engine.

Theoretically a four engine jet should be more efficient since an AC needs enough extra power to continue to fly less one engine, a 2 engine jet needs 100% excess power and a 4 engine jet only needs 33% excess power, but I don't think we are going to convince each other on this point. My original idea was that maintenance costs should not be based on market price since AC with real world high maintenance costs would have lower market prices, even if we just said the maintenance costs were based on dry weight and nothing else, it would be more realistic.

But again, the 747 to A330 is an unfair comparison. 777-300ER to the 747-400, that's a better comparison.

I wont argue with that, but its not as unfair as comparing an A330 to a B707.

I think we have beaten this topic to death.

"Beware of posting in haste and contradiction, for there in lies flames" --Daniel Freedson, Mosaic User

Ok, one by one:
I never said a bigger engine was more fuel efficient, I just said twin jets are more efficient than quads.

DC4 was a lot slower to fly, mad props (no pun intended) to the pilot who flies it the same route as the 739, might as well let them get the extra money. Smart choices in aircraft purchasing = Faster growth. Reference :Albatross (again) They made more money with their Il 86 then I think they knew what to do with. New airlines start with junk (sometimes) because it is cheap. Westjet had 732s, Southwest did too. I think Jetsgo had MD-80s or something, old douglas beaters, but they made it work, for a while. That low startup cost and high returns is only there for people who want to fly the old planes, without such things as, say, autopilot, GPS, etc. And they burn more fuel generally too. Although I am going to change the DC4s price, make it only 230% or something instead of the 435 you pointed out.

As well, your argument for RJs just increases my argument for twin jets being more efficient.

You don't see many of these:


in the air compared to these:



Cheers,

[joefremont]

"Beware of posting in haste and contradiction, for there in lies flames" --Daniel Freedson, Mosaic User

Ok, one by one:
I never said a bigger engine was more fuel efficient, I just said twin jets are more efficient than quads.

DC4 was a lot slower to fly, mad props (no pun intended) to the pilot who flies it the same route as the 739, might as well let them get the extra money. Smart choices in aircraft purchasing = Faster growth. Reference :Albatross (again) They made more money with their Il 86 then I think they knew what to do with. New airlines start with junk (sometimes) because it is cheap. Westjet had 732s, Southwest did too. I think Jetsgo had MD-80s or something, old douglas beaters, but they made it work, for a while. That low startup cost and high returns is only there for people who want to fly the old planes, without such things as, say, autopilot, GPS, etc. And they burn more fuel generally too. Although I am going to change the DC4s price, make it only 230% or something instead of the 435 you pointed out.

As well, your argument for RJs just increases my argument for twin jets being more efficient.

Cheers,

I can't believe you changed the price of the DC-4 because of this discussion. Before you go changing them arbitrarily we should probably review the prices of all the propliners, both turbos and pistons to determine there fair value. I admit that I submitted it and based its value on its piston engines rather than turbo's, its unpressurised hull, and of the few I found listed for sale online, none were more than 300k.

As for your efficency arguments about 4 vs 2 engines. Any combination of engines are more efficient either because of a better thrust to fuel consumtion ratio or because of the cost to maintain them. If its more efficent because of fuel, then its because two big engines are more efficent that four smaller ones at producing the same amount of thrust. Now over all the two engines will probably be lighter and therefore the plane can carry more of other stuff, but you have not given any other reason as to why.

Over all I agree that its more cost effective to fly twin engine planes than four engine planes, but the main reason for that is not fuel savings, its cost of purchase and maintenance.

[CAPFlyer]

If you change it Justin, I'll change it back. A DC-4 sells on the open market for a cool $500,000. If you want back up, I'll make some phone calls and get official offer sheets for a couple that are out there.

The 739 is bought brand new. The DC-4 isn't. The point that Joe is trying to point out is that when you buy used airplanes (i.e. any one off the "market") then the MX formula as it is does not take that into account properly to penalize somewhat those who operate used aircraft because they DO take more maintenance to keep flying than a new airplane. Yes, you can defer maintenance on a DC-3 and it'll keep chugging for quite a while, but I'm part of the Commemorative Air Force's DFW Wing, and we have an R4D-6 (C-47B/DC-3). Last October at AirSho '05, we lost an engine. We replaced it. We flew the plane back to Lancaster and started the annual inspection. Guess what - we found metal chips in the OTHER engine. Now we've had to replace both engines. That's over $200,000 that has been shelled out on engines alone in 6 months. Not only that, but there was a lot of other equipment replaced and overhauls on both of the props while we were at it (usually runs about $10,000 per prop). So we've nearly doubled the $200,000 market value for a freighter-only version. As a restored museum piece, the plane's worth about $500,000 though. But even then, that restored R4D-6 is still worth less than 1/4 what the FG-1D in the hangar is worth - $2.5 Million.

I've been taught 3 things by real-world airplane mechanics who have a lot more experience than I'll ever get.

1) Pistons take more maintenance than Old Jets.
2) Old Jets take more maintenance than New Jets.
3) The more of anything you have, the more likely one of them is to fail. (i.e., if you have 4 pistons, 1 is almost certain to fail. If you have 2 pistons, it's much less common to have one go. Why that is, no one really knows, it just is).

Prices don't seem right not because they aren't, but because the maintenance system isn't right.

[cmdrnmartin]

Curses, Foiled by CAP FLyer.