KA C90 vs PA-31T vs C425

[Capt.Crash'n'Burn]

In a previous thread about turbne singles, Dave Siciliano brought up some good points on the capabilities of small turbine twins (KA C90) vs their single engine counterparts. This got me to thinking about how the KA's competitors stack up against it.

From what I've read, the C90 has the largest cabin and is the most comfortable of the bunch, with the Cheyenne being the fastest and longer range with the C425 being somewhere in between. Does that sound about right?

What about other factors? Does one plane have other less tangible advantages? (easier to fly, easier to maintain, etc?) What about short field capabilities? Does one take off quiker than the others? Is there much difference in operating costs?

 

[N747JB]

I just bought a 425, it seemed like a good fit for my family. It's is faster than a C90, 20-35 knots depending on which version of C90, I'm not sure on the Cheyenne speeds, I didn't like the cabin. The spar passes right behind the cockpit and makes it tough on fat guys to enter and exit.
I flew a KA200 one time, several years ago, I liked it, I'm not wild about stepping over the pedestal to get in the pilots seat, if I were riding in the back, I think a 200 would be high on my list.
I get between 250-260 knots true at FL220, burning about 400 PPH, I flight plan for 75 GPH on my shorter trips, I haven't done any 2+ hour trips yet to see what that total fuel burn would be.
I can't comment on maintenance yet, I'm in for my first phase inspections, including prop overhauls. KA's do have 5 and 6 year items that have to be accounted for, but Cessnas have the ongoing SID inspections, which is turning out to be more than many people thought. My airplane is on an AAIP maintenance program, which breaks the SIDS down into calendar inspections vs doing them all at once, I have 14 more years to complete the program. Once each phase of the SID is complete it becomes a recurrent inspection.
I am a life long Cessna guy, so I am predisposed to Cessnas.

 

[txflyer]

What about the Baron turbine conversion fella's?

Would you say it is even in the same league as these others?

 

[Ted]

I have no 425 or King Air time of any sort, but I've got about 25 hours in a PA-31T-620 (Cheyenne II). There's also the PA-31T-500 (Cheyenne I) and I forget the Cheyenne IIXL's type.

The Cheyenne I flew had a weak left engine and did about 235 KTAS in the low 20s. At FL250 it did 225 KTAS. Fuel burn at FL250 was 400 PPH combined, and about 450 in the low 20s. The cabin is basically the same as the Navajo's. It flies like a Navajo, which is good if you like and are used to Navajos. It seemed to be a pretty easy aircraft to maintain and fairly reliable. The fuel bladders started leaking on it, and that was a pain to do. Plus they never figured out what was wrong with the weak left engine, but it was cheaper to say "They all do that."

Another friend of mine with a better Cheyenne II seems to get 240-250ish in the low/mid 20s. He doesn't have a weak engine.

I really liked the Cheyenne as a pilot. I found it stable, comfortable, and to have good manners. Since most of my time is in Piper twins (and I went into the Cheyenne with a enough Navajo time and systems knowledge), I found its systems to be straightforward. I suspect if you took someone with Cessna or Beechcraft time, they would find the same to be true for the options from that company.

 

[Henning]

What about the Baron turbine conversion fella's?

Would you say it is even in the same league as these others?

No, the Duke conversion is closer, but still a smaller airframe.

 

[J3 Driver]

After flying Cheyenne I, Cessna 441 and the KA350 I'll take the Beechcraft any day of the week. For me the Kingair is the most comfortable of them all and the newer C90s are around 275 knot airplanes.

 

[Ted]

After flying Cheyenne I, Cessna 441 and the KA350 I'll take the Beechcraft any day of the week. For me the Kingair is the most comfortable of them all and the newer C90s are around 275 knot airplanes.

The market seems to agree with you overall.

 

[N747JB]

My take on these conversions, Baron, Duke, 340, 421 etc are they are trying to fix something that ain't broke. All these airplanes do well as piston twins, as they were designed. If you look at the cost to bastardize an airplane into something it wasn't designed to be. And compare it to factory turbo props, that are designed for turbine engines, it's cheaper to buy a really nice factory airplane AND have the fuel capacity and useful load to make use of the turbine engines.

What about the Baron turbine conversion fella's?

Would you say it is even in the same league as these others?

 

[Ted]

My take on these conversions, Baron, Duke, 340, 421 etc are they are trying to fix something that ain't broke. All these airplanes do well as piston twins, as they were designed. If you look at the cost to bastardize an airplane into something it wasn't designed to be. And compare it to factory turbo props, that are designed for turbine engines, it's cheaper to buy a really nice factory airplane AND have the fuel capacity and useful load to make use of the turbine engines.

The one thing I'd say with the Baron/Duke/340 is that they're making a turboprop that's a bit smaller than what was otherwise available. Not everyone necessarily needs a full on cabin class turboprop twin. However, the 340 seems to be the only one that really gets the conversion "right" as in has the fuel capacity to handle the thirstier turbines.

The biggest thing I don't like is the low pressurization, which I don't see them being able to improve.

 

[N747JB]

The smaller turbines are probably a good fit, but historically these conversions have been very tough to resell. Realizing that airplanes aren't investments, the conversions seem to really take a dive, pricewise!

The one thing I'd say with the Baron/Duke/340 is that they're making a turboprop that's a bit smaller than what was otherwise available. Not everyone necessarily needs a full on cabin class turboprop twin. However, the 340 seems to be the only one that really gets the conversion "right" as in has the fuel capacity to handle the thirstier turbines.

The biggest thing I don't like is the low pressurization, which I don't see them being able to improve.

 

[txflyer]

My take on these conversions, Baron, Duke, 340, 421 etc are they are trying to fix something that ain't broke. All these airplanes do well as piston twins, as they were designed. If you look at the cost to bastardize an airplane into something it wasn't designed to be. And compare it to factory turbo props, that are designed for turbine engines, it's cheaper to buy a really nice factory airplane AND have the fuel capacity and useful load to make use of the turbine engines.

Makes sense to me.

 

[Dave Siciliano]

I moved to the C90 from a P baron; so, I only have that perspective. There are different model C90s, the new ones have a more powerful engine that raises TAS. My plane was very early in the upgrade from a -20 to -21s. The -21s were standard on the C90 for years. The E90 has a more powerful engine and more fuel with other differences I won't go into to keep it simple. The F-90 had 750 HP engines derated to 550 which is what the new C90 has.

Let me just tell you what the C90 with -21s will do and go from there. Eight seats. Crew plus four club seats and a side and rear seat is pretty standard, but one can have other arrangements. There is a relief tube under the pilot's seat. Curtains between crew and passengers. Coffee pot that can stay hot in flight; cooler and some storage in the main cabin. Potty seat in the rear and a baggage area in the rear that can hold five for six good sized suitcases. Curtains in front of potty seat which also has a relief tube.
The -21s are rated at 550 hp and with a pretty good load, I climb at 140 knots about 1,500 fpm to the low teens on a standard day A bit slower to the low flight levels from there. I cruise at 225 to 235 at FL 200 with a cabin at between 6 and 7,000 feet. Fuel burn up there is about 65 gph. The plane will go faster in the mid teens but burn more fuel. Trading fuel burn for a reasonable cabin altitude makes low flight levels attractive to me. With full fuel, which is about six hours in the low flight levels, I have about a 950 pound payload. Took four adults and three kids to the Bahamas this summer and payload wasn't the issue. One can always use more room. With play pens and baby stuff we were pretty full, but it all fit.
I just can't convey how much better one feels in the twin turbine compared to the piston. Much smoother running, quieter, climbs almost twice as fast to the flight levels as my baron did and it's very stable. The plane has an easy 800 mile range with no wind and IFR reserves and can do 1,000 with VFR reserves and no wind. Let me know if I can add anything else. Can't really compare it to the planes you mention because I don't have time in them.

Best,

Dave

 

[Dave Siciliano]

Ted: we need to get you up in the KA next time you're out this way so we can have someone with your background properly versed in KAs

Best,

Dave

 

[txflyer]

Aerostar's are interesting.

I'm surprised no one has strapped a couple of turbines to one. Guess it doesn't pencil out.

 

[Ted]

The smaller turbines are probably a good fit, but historically these conversions have been very tough to resell. Realizing that airplanes aren't investments, the conversions seem to really take a dive, pricewise!

I absolutely agree, John. My point was strictly from a capability perspective, ignoring money. Isn't that what we should do with airplanes?

Ted: we need to get you up in the KA next time you're out this way so we can have someone with your background properly versed in KAs

Best,

Dave

Sounds like a great idea!

Aerostar's are interesting.

I'm surprised no one has strapped a couple of turbines to one. Guess it doesn't pencil out.

There was someone who attached a pair of jets to one at Osh a year or two ago. The plane supposedly was quite fast that way, but I haven't heard anything about it.

The real issue as John alluded to is that you have to find the market that will actually buy it. I think most of the people with the money at that point will go cabin class for comfort. Meanwhile, dreamers like me think more in terms of what I could afford to operate if the plane was free.

Pistons can have some advantages, though. An old colleague and I were talking about the Lancair Evolution the other day. He and I have both flown the piston variant (or at least flown in - my 1000th hour as a pilot was flying it), and I found its climb performance rather lackluster. I suspect that's why it's proven unpopular. But, with the same fuel tanks as the turbine version, its range is actually further, and it will get some places faster as a result of the turbine needing a fuel stop the piston doesn't. Also, if you live in an area where it takes a long time to get to altitude due to vectoring/traffic (think the east coast), the piston is a real fuel saver.

Of course, it also has the glide ratio of a brick when that piston engine quits.

 

[Henning]

Aerostar's are interesting.

I'm surprised no one has strapped a couple of turbines to one. Guess it doesn't pencil out.

Actually they put a couple of turbojet engines on it as Ted Smith had intended. I know there is one out there, I'm not sure where Aerostar is on their program with certifying the conversion.

 

[N747JB]

It's funny reading Dave's description of his C90, with the exception of a little more speed at altitude, our airplanes are pretty similar. I have 8 seats including the potty seat, our baggage goes in the nose vs the tail, I am missing the pilots relief tube though! I might have to look into that one!
Just two manufacturers version of the same thing. Not unlike Ford vs Chevy, both are good, but some folks like one over the other.

 

[Capt.Crash'n'Burn]

I moved to the C90 from a P baron; so, I only have that perspective. There are different model C90s, the new ones have a more powerful engine that raises TAS. My plane was very early in the upgrade from a -20 to -21s. The -21s were standard on the C90 for years. The E90 has a more powerful engine and more fuel with other differences I won't go into to keep it simple. The F-90 had 750 HP engines derated to 550 which is what the new C90 has.

Let me just tell you what the C90 with -21s will do and go from there. Eight seats. Crew plus four club seats and a side and rear seat is pretty standard, but one can have other arrangements. There is a relief tube under the pilot's seat. Curtains between crew and passengers. Coffee pot that can stay hot in flight; cooler and some storage in the main cabin. Potty seat in the rear and a baggage area in the rear that can hold five for six good sized suitcases. Curtains in front of potty seat which also has a relief tube.
The -21s are rated at 550 hp and with a pretty good load, I climb at 140 knots about 1,500 fpm to the low teens on a standard day A bit slower to the low flight levels from there. I cruise at 225 to 235 at FL 200 with a cabin at between 6 and 7,000 feet. Fuel burn up there is about 65 gph. The plane will go faster in the mid teens but burn more fuel. Trading fuel burn for a reasonable cabin altitude makes low flight levels attractive to me. With full fuel, which is about six hours in the low flight levels, I have about a 950 pound payload. Took four adults and three kids to the Bahamas this summer and payload wasn't the issue. One can always use more room. With play pens and baby stuff we were pretty full, but it all fit.
I just can't convey how much better one feels in the twin turbine compared to the piston. Much smoother running, quieter, climbs almost twice as fast to the flight levels as my baron did and it's very stable. The plane has an easy 800 mile range with no wind and IFR reserves and can do 1,000 with VFR reserves and no wind. Let me know if I can add anything else. Can't really compare it to the planes you mention because I don't have time in them.

Best,

Dave

Thanks for the post Dave, lots of good imfo there.

 

[Capt.Crash'n'Burn]

I just bought a 425, it seemed like a good fit for my family. It's is faster than a C90, 20-35 knots depending on which version of C90, I'm not sure on the Cheyenne speeds, I didn't like the cabin. The spar passes right behind the cockpit and makes it tough on fat guys to enter and exit.
I flew a KA200 one time, several years ago, I liked it, I'm not wild about stepping over the pedestal to get in the pilots seat, if I were riding in the back, I think a 200 would be high on my list.
I get between 250-260 knots true at FL220, burning about 400 PPH, I flight plan for 75 GPH on my shorter trips, I haven't done any 2+ hour trips yet to see what that total fuel burn would be.
I can't comment on maintenance yet, I'm in for my first phase inspections, including prop overhauls. KA's do have 5 and 6 year items that have to be accounted for, but Cessnas have the ongoing SID inspections, which is turning out to be more than many people thought. My airplane is on an AAIP maintenance program, which breaks the SIDS down into calendar inspections vs doing them all at once, I have 14 more years to complete the program. Once each phase of the SID is complete it becomes a recurrent inspection.
I am a life long Cessna guy, so I am predisposed to Cessnas.

Thanks for the post. There's good info here too.

One question for you. Do you know of the 421 turbine conversions have to go through the same SID inspections as the 425?

 

[Capt.Crash'n'Burn]

Speaking of 421 conversions. Does anyone know if these perfomance figures are accurate??

http://www.controller.com/listingsd...NE/1975-CESSNA-421B-RILEY-TURBINE/1186785.htm

 

[Ted]

Jason used to fly a Riley turbine 421, so he probably knows the speed numbers better on the speeds.

The 421 didn't have the AD for wing spar inspections, but Cessna did publish a procedure for all the twins. For the 310 it's recommended at 11k hours and is about a 450 hour book time inspection.

Yeah, I think I'll skip that.

 

[Dave Siciliano]

It's funny reading Dave's description of his C90, with the exception of a little more speed at altitude, our airplanes are pretty similar. I have 8 seats including the potty seat, our baggage goes in the nose vs the tail, I am missing the pilots relief tube though! I might have to look into that one!
Just two manufacturers version of the same thing. Not unlike Ford vs Chevy, both are good, but some folks like one over the other.

Probably so John! Didn't mean to mislead on the baggage. It's in the rear of the pressurized cabin; not in an unpressurized area. I do have to say, when I compare the way Beechcraft are built, I think a more accurate comparison might be Ford or Chevy compared to a more top of the line car. All analogies have shortcomings, but ask a mechanic or look at door thickness, how things latch, etc. Yet, same capability and there certainly is a place for each.

Best,

Dave

 

[N747JB]

Thanks for the post. There's good info here too.

One question for you. Do you know of the 421 turbine conversions have to go through the same SID inspections as the 425?

I don't believe the 421's are included in the SID inspection process, I know it didn't apply to my 421B. The 421 turbine conversions were all B models up until this latest group starting to build them.

 

[N747JB]

No misleading, they are different airplanes with similar missions, built by tow companies that have different philosophies. I think Cessna was looking more towards the owner flown market, while Beech catered to the owner flies in the back crowd. I do like the way the King Airs are built, it's no secret that the 425 is a reworked 421C, they changed the tail and heating system, but it's pretty danged close otherwise.
It's all good!
All I need now is to get the props back from the overhaul shop on Monday so I can fly for Thanksgiving!

Probably so John! Didn't mean to mislead on the baggage. It's in the rear of the pressurized cabin; not in an unpressurized area. I do have to say, when I compare the way Beechcraft are built, I think a more accurate comparison might be Ford or Chevy compared to a more top of the line car. All analogies have shortcomings, but ask a mechanic or look at door thickness, how things latch, etc. Yet, same capability and there certainly is a place for each.

Best,

Dave

 

[Dave Siciliano]

Hope your machine comes back on time and under budget John!

Best,

Dave

 

[kgruber]

I moved to the C90 from a P baron; so, I only have that perspective. There are different model C90s, the new ones have a more powerful engine that raises TAS. My plane was very early in the upgrade from a -20 to -21s. The -21s were standard on the C90 for years. The E90 has a more powerful engine and more fuel with other differences I won't go into to keep it simple. The F-90 had 750 HP engines derated to 550 which is what the new C90 has.

Let me just tell you what the C90 with -21s will do and go from there. Eight seats. Crew plus four club seats and a side and rear seat is pretty standard, but one can have other arrangements. There is a relief tube under the pilot's seat. Curtains between crew and passengers. Coffee pot that can stay hot in flight; cooler and some storage in the main cabin. Potty seat in the rear and a baggage area in the rear that can hold five for six good sized suitcases. Curtains in front of potty seat which also has a relief tube.
The -21s are rated at 550 hp and with a pretty good load, I climb at 140 knots about 1,500 fpm to the low teens on a standard day A bit slower to the low flight levels from there. I cruise at 225 to 235 at FL 200 with a cabin at between 6 and 7,000 feet. Fuel burn up there is about 65 gph. The plane will go faster in the mid teens but burn more fuel. Trading fuel burn for a reasonable cabin altitude makes low flight levels attractive to me. With full fuel, which is about six hours in the low flight levels, I have about a 950 pound payload. Took four adults and three kids to the Bahamas this summer and payload wasn't the issue. One can always use more room. With play pens and baby stuff we were pretty full, but it all fit.
I just can't convey how much better one feels in the twin turbine compared to the piston. Much smoother running, quieter, climbs almost twice as fast to the flight levels as my baron did and it's very stable. The plane has an easy 800 mile range with no wind and IFR reserves and can do 1,000 with VFR reserves and no wind. Let me know if I can add anything else. Can't really compare it to the planes you mention because I don't have time in them.

Best,

Dave

King Air is a great ride. I'd love to fly one again. One nit....The F-90 engines are "flat" rated to 550, not "derated. Big difference.

 

[N747JB]

We're close on time, never got an estimate on the props, so I guess we are on budget! The phase inspections were pretty clean, so I don't expect any surprises unless the prop shop found something big and is waiting to tell me!

Hope your machine comes back on time and under budget John!

Best,

Dave

 

[Ted]

We're close on time, never got an estimate on the props, so I guess we are on budget! The phase inspections were pretty clean, so I don't expect any surprises unless the prop shop found something big and is waiting to tell me!

Too bad I don't have pictures of my Aztec props to show. Now those were good!

 

[Dave Siciliano]

King Air is a great ride. I'd love to fly one again. One nit....The F-90 engines are "flat" rated to 550, not "derated. Big difference.

Yep, the -135s for the C90 are de-rated. Good catch.

Best,

Dave

 

[J3 Driver]

Aerostar's are interesting.

I'm surprised no one has strapped a couple of turbines to one. Guess it doesn't pencil out.

Its been done. Bobby Allison had one with Allison or. RR turbines.

 

[Capt.Crash'n'Burn]

King Air is a great ride. I'd love to fly one again. One nit....The F-90 engines are "flat" rated to 550, not "derated. Big difference.

Yep, the -135s for the C90 are de-rated. Good catch.

Best,

Dave

OK, I'l still a little shaky on the difference. From what I understand, a de-rated engine is just that, a more powerful engine that has some kind of restrictor installed to reduce HP. My understanding of a Flat Rated engine is that it behaves a bit like a turbo-normalized engine where it will produce the same HP over a wide range of altitudes and temps. Am I close??

 

[Henning]

OK, I'l still a little shaky on the difference. From what I understand, a de-rated engine is just that, a more powerful engine that has some kind of restrictor installed to reduce HP. My understanding of a Flat Rated engine is that it behaves a bit like a turbo-normalized engine where it will produce the same HP over a wide range of altitudes and temps. Am I close??

IIRC correctly, the PT6-135 can go all the way to 2000hp, so at 500 in the KA it is most definitely using a derated version. A turbine would derate by restricting fuel flow.

 

[ronnieh]

Let me try to answer that. A turbine engine is a normally aspirated engine. Go up in altitude and power goes down. A flat rated engine is restricted to max torque per the airframe. An example I am familiar with: The Cheyenne IIIA has the -61 engine with a thermodynamic rating if I recall correctly of 920HP. Piper only allows 720 HP per side. You are therefore restricted to partial throttle operation limiting the torque to I think it was 2100 ft lbs. per side (720 HP).
As you climb you can add power to maintain the full 720 HP until you temp out. This means at some point there is not enough air to make the 720 HP and maintain the ITT below redline. At that point you start going below the flat rating of the engine. It is at this point that fuel usage per mile starts improving significantly. Most turbine applications have some flat rating imposed by the airframe. The larger the delta in thermodynamic rating and the flat rating the better the speed at altitude. That is what makes the IIIA faster than the straight III even though both are flat rated to 720 HP. The B200 is faster than a straight 200 due to the ability to make the flat rated HP to a higher altitude. Does this help?

 

[N747JB]

I am not mechanic, but I think you are correct, they flat-rate a 750 HP engine to produce 500 HP at sea level and it is able to maintain that power up a higher altitude than an engine that is rated at 500 HP. This is how they use the -135 engines on KA 90's and C425's they have to use the stock HP for take off, but they can make full power up to much higher altitudes, giving faster climbs and higher cruise speeds.
On the C425's the stock -114's are 450 HP, the Blackhawk -135 conversion is a 750 HP engine that is flat rated to 450, or so I understand.

OK, I'l still a little shaky on the difference. From what I understand, a de-rated engine is just that, a more powerful engine that has some kind of restrictor installed to reduce HP. My understanding of a Flat Rated engine is that it behaves a bit like a turbo-normalized engine where it will produce the same HP over a wide range of altitudes and temps. Am I close??

 

[ronnieh]

Henning, not exactly. A PT6-135A is rated at 750HP. They are flat rated to I think 500 in the KA 90 series allowing the full 500 to be available to a higher altitude. I am sure Dave can give more accurate numbers. A stock 90 (older model with the -21) would temp at perhaps as low as 10,000 feet. You seldom see a straight 90 with the -21 operated above 20,000 and that is a struggle. The 135A conversion with the larger delta between thermodynamic and flat rate allows perhaps up to 17,000 feet before temping out.
The 135 series engines are available up to I THINK 2000 HP but the compressor wheels and PT wheels would be different depending on HP.
The altitude at which you temp out is dependent of more than one factor, condition of compressor components, PT components, and of course atmospheric conditions.
Edit: Dave it is FLAT rated not DErated.

 

[Skylane81E]

IIRC correctly, the PT6-135 can go all the way to 2000hp, so at 500 in the KA it is most definitely using a derated version. A turbine would derate by restricting fuel flow.

Yep, a gross over simplification of how a turbine is controlled is to think of a well balanced recip running full throttle lean of peak. You can control the power by adjusting the mixture, more fuel gives more power and more heat

 

[Baron2PG]

My take on these conversions, Baron, Duke, 340, 421 etc are they are trying to fix something that ain't broke. All these airplanes do well as piston twins, as they were designed. If you look at the cost to bastardize an airplane into something it wasn't designed to be. And compare it to factory turbo props, that are designed for turbine engines, it's cheaper to buy a really nice factory airplane AND have the fuel capacity and useful load to make use of the turbine engines.

I've seen the Baron 55 turboprop experimental; while interesting, as a BE58 pilot I don't care for it. First, it would need to be a 58 for ease of seating and loading bags. With the conversion you have to suck on O2 as the airframe isn't pressurized; big suck factor. Also, you loose the nose baggage which is a major loss of storage space. In the end, you would be much farther ahead buying a TBM700.

 

[ronnieh]

Duncan, not exactly. Just dumping more fuel into a 135A will not make a 2000 HP engine out of a 750. The 135's that are rated above the base 750 have different internal parts. Compressor wheels, PT wheels, perhaps fuel nozzles, burner cans, fuel control units and I am sure other parts. The -135 is a family of engines with different available HP ratings depending on configuration.
Edit: I corrected this in a later post. PT6 is the family and -135A is one member, rated at 750 HP.

 

[Henning]

Again, not exactly. Just dumping more fuel into a 135A will not make a 2000 HP engine out of a 750. The 135's that are rated above the base 750 have different internal parts. Compressor wheels, PT wheels, perhaps fuel nozzles, burner cans, fuel control units and I am sure other parts. The -135 is a family of engines with different available HP ratings depending on configuration.

Right, but since it's available as 2000hp, anything below that is a derating regardless of how it's accomplished. So in the instance it is both derated and flat rated.

 

[Skylane81E]

Duncan, not exactly. Just dumping more fuel into a 135A will not make a 2000 HP engine out of a 750. The 135's that are rated above the base 750 have different internal parts. Compressor wheels, PT wheels, perhaps fuel nozzles, burner cans, fuel control units and I am sure other parts. The -135 is a family of engines with different available HP ratings depending on configuration.

Like I said, gross over simplification of control