Cost for jet rebuild

[Cujet]

Originally Posted by MolaKule
Well, I don't know what happened to your last post (apologize) as I attempted to quote it but my question was:

Understand but what is that centrifugal-looking element at the front of the core assembly. Is that a diffuser?


The engine has a 4 foot fan, with blades designed to shed ice outward via a bit of reverse twist at the root. The core engine draws air from the fan's blade root area. So I think what you are looking at is simply the layout and ducting of the engine. I'm hoping to find a better picture.

I took a bunch of pictures when at RR Canada for the overhauls. I'll look for them.

BR725 cutaway. Same engine, one extra low pressure turbine.

Possibly of interest, but these engines are really quite different (in design and materials) from high bypass airliner engines. They are medium bypass engines, with long engine cowls and high discharge pressures/velocities. The goal is to provide adequate thrust at very high altitudes and speeds. This is done by increasing nozzle discharge temperature, thereby raising the speed of sound at the nozzle and increasing the discharge speed. Done by mixing core engine exhaust with fan air. The Gulfstream G650 we had could cruise at M .92 at FL470. That was about the limit of it's performance (in normal mode) , with regard to altitude and speed, but what a nice limit. FL510 was a bit slower. Of course, it had enough thrust below FL470 to easily run into and over MMO (max mach operating number, airframe speed limit) .

With regard to the "normal mode" I mentioned above, the engine can make more thrust in "alternate" mode. Normal mode is set, in part, by the airframe manufacturer to prevent overspeed/overthrust/airframe stress and to allow rated thrust under all published conditions. Alternate mode is a mode of operation limited only by engine RPM and Temperatures.

 

[Cujet]

With regard to the OP's thoughts, the RR BR700 series engines on the Gulfstream Jets cost about $11-12M and when disassembled, it becomes clear as to why they cost so much. These are complex beasts, with each part made from the lightest material possible. They use exotic materials and machine them into jewels.

It's also interesting to note that Pratt Whitney takes a completely different approach to making similar engines. As they use a single piece fan! A smaller airline derived core engine (existing parts) , and they spend the engineering effort towards simplifying everything. Pratt had some teething problems but eventually got it right. Same performance, same good efficiency, significantly lower cost.

 

[MolaKule]

Thanks for the info.

The last Gulfstream I worked with was the G280 (sans G250) which had the Honeywell HTF7250G turbofans engines.

https://www.businessinsider.com/gulfstream-g280-private-jet-tour-photos-2018-7

 

[JTK]

A bit OT, but how long do the APUs go on aircraft between rebuilds? I'd imagine they're not cheap either.

With the all the costs involved to be up in the air, it's amazing you can buy a ticket for as cheap as we can.

 

[Exhaustgases]

And lastly added on to the costs is the huge fuel consumption bill. Like Agent JZ says there is no fuel ratio control in a jet engine the goal is to spray in the fuel and it burns.

 

[pitzel]

Originally Posted by Exhaustgases
And lastly added on to the costs is the huge fuel consumption bill. Like Agent JZ says there is no fuel ratio control in a jet engine the goal is to spray in the fuel and it burns.


For a typical bizjet, the fuel is just a rounding error. For airlines, about 1/3rd of the overall bill.

 

[fdcg27]

Originally Posted by Exhaustgases
I found a site that mentioned up to 500k to rebuild one engine on a small private jet plane and posted TBO was 4000 hours, the first rebuild would probably be in the 250k area, because the big life cycle parts may have more time. So what would the price be for a 737 or 787 or airbus? I'm thinking 2.5 to 3 Million per engine.


4000 hours sounds like a hot section inspection, not a full rebuild.
Anyway, the last generations of big piston engines had plenty of power as well as fuel efficiency comparable to the first large turbojets.
The jets were more economical to operate because they were far more reliable and cheaper to maintain.
Not all turbine engines are the same. of course and they range from the high of 30K hours plus of on-wing time achieved by an RR on an AA 757 (I think, might have been a 767) to the far lower hours the engines of the 717 or MD80 are capable of.
Ask any piston GA owner about engine overhaul time and costs and be prepared to get an earful, particularly for turbo engines.
Most of these aircraft aren't flown enough to get to anything close to rated TBO before the engine(s) gets flagged in an annual, so it's either off to the shop, parted or offered cheap on Trade-a-plane.

 

[Exhaustgases]

Originally Posted by fdcg27
Originally Posted by Exhaustgases
I found a site that mentioned up to 500k to rebuild one engine on a small private jet plane and posted TBO was 4000 hours, the first rebuild would probably be in the 250k area, because the big life cycle parts may have more time. So what would the price be for a 737 or 787 or airbus? I'm thinking 2.5 to 3 Million per engine.


4000 hours sounds like a hot section inspection, not a full rebuild.
Anyway, the last generations of big piston engines had plenty of power as well as fuel efficiency comparable to the first large turbojets.
The jets were more economical to operate because they were far more reliable and cheaper to maintain.
Not all turbine engines are the same. of course and they range from the high of 30K hours plus of on-wing time achieved by an RR on an AA 757 (I think, might have been a 767) to the far lower hours the engines of the 717 or MD80 are capable of.
Ask any piston GA owner about engine overhaul time and costs and be prepared to get an earful, particularly for turbo engines.
Most of these aircraft aren't flown enough to get to anything close to rated TBO before the engine(s) gets flagged in an annual, so it's either off to the shop, parted or offered cheap on Trade-a-plane.


Not what the article said. There was mention of a life cycle part that goes so many cycles or 1700 hours, I think it was the turbine disk. No matter what, turbines are not a cheap item to operate.

 

[Cujet]

Originally Posted by fdcg27

Ask any piston GA owner about engine overhaul time and costs and be prepared to get an earful


Of note: The IO360 angle valve 4 cylinder in my 177RG costs about $30K to overhaul and will consume $120,000 worth of fuel over it's 2000 hour life.

 

[Exhaustgases]

Originally Posted by fdcg27
Originally Posted by Exhaustgases
I found a site that mentioned up to 500k to rebuild one engine on a small private jet plane and posted TBO was 4000 hours, the first rebuild would probably be in the 250k area, because the big life cycle parts may have more time. So what would the price be for a 737 or 787 or airbus? I'm thinking 2.5 to 3 Million per engine.


4000 hours sounds like a hot section inspection, not a full rebuild.
Anyway, the last generations of big piston engines had plenty of power as well as fuel efficiency comparable to the first large turbojets.
The jets were more economical to operate because they were far more reliable and cheaper to maintain.
Not all turbine engines are the same. of course and they range from the high of 30K hours plus of on-wing time achieved by an RR on an AA 757 (I think, might have been a 767) to the far lower hours the engines of the 717 or MD80 are capable of.
Ask any piston GA owner about engine overhaul time and costs and be prepared to get an earful, particularly for turbo engines.
Most of these aircraft aren't flown enough to get to anything close to rated TBO before the engine(s) gets flagged in an annual, so it's either off to the shop, parted or offered cheap on Trade-a-plane.


Millions of dollars for an overhaul is not cheaper. Nor was the 8.3 gallons per minute per engine on a DC-8, I got that number watching the Aircrash investigation show on tv about the DC8 that ran out of fuel and crash landed in oregon.
No jet engine that has dust or fod blasting on those blades will go 30K hours, runways have to be spotless for them and no sand storms or volcano's. Jets and turbines are very suseptable to abrasive wear, and there is no air filters allowed.

 

[DeepFriar]

Originally Posted by Cujet
With regard to the OP's thoughts, the RR BR700 series engines on the Gulfstream Jets cost about $11-12M and when disassembled, it becomes clear as to why they cost so much. These are complex beasts, with each part made from the lightest material possible. They use exotic materials and machine them into jewels.

It's also interesting to note that Pratt Whitney takes a completely different approach to making similar engines. As they use a single piece fan!



Blisk. Great machining and materials innovation. These airliner engines are so valuable that a *mature* airframe without engines or without rebuildable engines is hardly worth what the Coke cans can be made from it are. Modern turbines are really quite miraculous but only cost effective over a long life span. One other thing, the flying public would probably be aghast if they knew how many used parts are in virtually all the (non brand new) operational engine fleet. Nothing wrong with that but you sure don't hear anybody making the public *aware* of it either.

 

[nthach]

Originally Posted by DeepFriar

Blisk. Great machining and materials innovation. These airliner engines are so valuable that a *mature* airframe without engines or without rebuildable engines is hardly worth what the Coke cans can be made from it are. Modern turbines are really quite miraculous but only cost effective over a long life span. One other thing, the flying public would probably be aghast if they knew how many used parts are in virtually all the (non brand new) operational engine fleet. Nothing wrong with that but you sure don't hear anybody making the public *aware* of it either.

Who came up with the idea of blisks - GE on the GE90 or Rolls-Royce with the Trent family?

No wonder why GE/CFM and Rolls-Royce/IAE are using a pay per hour pricing model for their new engines - the LCCs love it(and the legacy carriers), and there's access to a fresh engine in case one goes out, and no need to train your in-house MRO on rebuilds.

 

[Exhaustgases]

So you are saying most jet engines are rented out, or leased?

 

[FowVay]

At 5 million each this is a good months work. We turn about 60 of these a year and this is just one engine line.

 

[Exhaustgases]

How much fuel do they burn per hour?

 

[tundraotto]

Originally Posted by DeepFriar
Originally Posted by Cujet
With regard to the OP's thoughts, the RR BR700 series engines on the Gulfstream Jets cost about $11-12M and when disassembled, it becomes clear as to why they cost so much. These are complex beasts, with each part made from the lightest material possible. They use exotic materials and machine them into jewels.

It's also interesting to note that Pratt Whitney takes a completely different approach to making similar engines. As they use a single piece fan!



Blisk. Great machining and materials innovation. These airliner engines are so valuable that a *mature* airframe without engines or without rebuildable engines is hardly worth what the Coke cans can be made from it are. Modern turbines are really quite miraculous but only cost effective over a long life span. One other thing, the flying public would probably be aghast if they knew how many used parts are in virtually all the (non brand new) operational engine fleet. Nothing wrong with that but you sure don't hear anybody making the public *aware* of it either.


This is one critical situation where one could discuss; 'used' (and proven) vs. new 'and unproven' parts.
On some parts - used could be the right answer, on other parts the new one.