Below are things I have wrote to others who asked about C425 costs. Basically the costs are in line with operating a 400 series twin Cessna airframe with PT6A turbine engines. Costs are rising for maintaining a 25+ year old airframe.

I hear some parts are getting difficult or time consuming to get repaired. I heard a while ago that there are no exchange units for the bleed air shutoff valves and the vendor who can OH them is saying it is a 6 month turn around time. So you find some 425's where you have hot bleed air coming into the cabin even when the bleeds are in off. That doesn't make for a comfortable cabin on the ground on hot summer days.

You have the Cessna SIDS and most 425s should have had them done.

My C425 hit or beat POH performance numbers by a few knots. For planning purposes you'll probably fly either in the high teens 16K-17K or at FL240-FL250.

At mid-weights at 17K will be 256K TAS burning 500PPH (250PPH/side). AT FL250 250KTAS at 400PPH.

Fuel burn anywhere below the FL's is 500PPH in cruise. So you have a 4 hour airplane with 2456lbs of fuel. If you climb to FL250 or above you have 5+ hours.

FL250 is the sweet spot for cruise. Cabin altitude is 9000 at FL250. At FL280 240TAS at 380PPH. Climb up to FL280 will be slow at about 500FPM or less. It doesn't pay to go that high unless there is a good operational reason. You'll also find the higher FL's have the big iron and the smaller turboprops are kept to the lower FL's in high density areas.

All the performace numbers are for ISA temps. All performance is based on density altitiude so if it's warmer you may get FL270 performance at FL250.

Max perf and normal performance are the same. Below about 17K you run at max torque until you hit max ITT temp. Then you maintain max ITT temp and can't increase TQ as it decreases as you climb.

Max range in the POH is whatever power setting gives you an airspeed of 210-220KTAS. I don't find it real useful. I run at normal power and make a fuel stop if necessary.

I think the Blackhawk 135 conversion is good. I already had 4 bladed props. You go faster but burn more fuel with the -135 engines so range is about the same. You still have the issues of what FL you'll be able to cruise at and the cabin altitude at the higher FL's.

Tips for purchase:

- You need a really good pre-purchase inspection and complete flight check
- you need to decide if your going to split the engine during inspection. there are pros and cons to it. You need someone with good PT-6 experience to look at the engine history and advise you.
- do the spar crack inspection during pre-purchase and see if the spar strap is installed
- check that the cabin holds pressurization with one bleed air source at about 17K
- review the inspection history and time in service for engine parts and airframe. Lot's of pricey stuff that needs periodic inspection and overhaul. For example starter generators need to be OH every 1000 hours for I think about $2500. Every 2 year D checks cost about $25,000.

The C425 fleet is small. Only 236 were built between 1981 and 1986.

Cost of ownership - you really want to know? Here are the major items from a stack of maintenance invoices:

5/01 - D Check - $21K
8/01 - Replace low pressure fuel switch - $800
8/01 - Misc repairs - broken door cable, patch boots - $2K
10/01 - Replace tire, troubleshoot pressurization - $500
12/01 - Replace failed encoding altimeter - $2700
1/02 - Replace aux heat blower - $700
5/2 -Fix broken wire in press dump switch - $1800
6/2 - Replace TQ gauge - $500
7/02 - Fix leaking TQ gauge line & replace ITT gauges - $2200
8/02 - Phase 2 & 3 Inspection (100hr & annual) - $5200
12/02 - Replace aux heat blower, troubleshoot gear, replace door cable, replace left cabin window - $2500
3/03 - Troubleshoot generator parrelling & OH starter generator - $2000
4/03 - Fix AP air data computer - $2800
5/03 - D Check - $21K+???

Other then the D check ($21K) and Phase 2/3 inspection ($5k) the other costs are for maintaining a 20 year old complex aircraft.

I also did a $100K avionics upgrade and replaced the interior.

There are not enough of them that are active owner/operators. Thats what happens when you leave the piston world (excepting jetprops/meridians).

The Conquest II is a beast. The hard part is finding one with reasonable airframe hours for a realistic price tag. You need a monster hangar also.

Full fuel useful load is about 780 lbs,

Fuel burn anywhere below the FL's is 500PPH in cruise. So you have a 4 hour airplane with 2456lbs of fuel. If you climb to FL250 or above you have 5+ hours.

No wind range at FL250 can be 1000 nm with reserves.

And costs less to HSI and OH. I'd much rather have the 441 than any model KA.


Add in a 100 knot headwind and that isn't so true any more. Go 500 nm in a headwind, and the speed issue becomes very significant. A plane that goes 250 instead of 300 is like having a 50 knot extra headwind all the time. This also plays into per mile costs as much of the maintenance cost is per hour.


The only "small hangar" twin TP is the MU2. Under 40' span.


The MU2 is both. :-)

Mike C.

I love my Mits, but if there was just room for 700 more lbs. of fuel...

The range is the only thing the Conquest has over the MU2. Everything else is no contest.

Outstanding feedback as always Allen. The real cause for concern regarding the MX costs you summarize above isn't the costs, it's the frequency of MX events. I count roughly 7 MX events per year over this 2 year span. If you have an outstanding service center on your field or at your base of operation, this is no big thing. However, if you have to get her to a shop off-field 6-7 times / year, this would be bonkers. The time involved in maintaining a bird like this is a much bigger factor than the number and size of checks written, at least to me.

Well, not everything.

441 has no SFAR mandated training. For an insured part 91 owner operator, really no practical impact since they will be required to go to type school anyway.

441 can go higher, FL350, if RVSM.

441 is less noisy on the ground. The MU2 engine under wing makes a howling resonance when at taxi RPMs that the overwing and longer tail pipe 441 doesn't seem to have as bad.

441 is less trim intensive. MU2, being short coupled, requires a fair amount of trim activity.

441 is easier to fuel, 2 filler ports on a low wing versus the 6 filler ports on the MU2 high wing.

People are less likely to walk into a prop on a low wing 441. Been a number of prop accidents for the MU2.

MU2s have no autopilot upgrade options as of yet. I would think the 441 does, but don't know that for sure.

I have a long list of "MU2 better than 441" comments, but the point is every airplane is a set of compromises and sometimes those compromises fit one owner over another better.

Mike C.

D check occurs every 2 years, and 12 years ago it was $21K each base rate?

That seems excessive, or is that gold plated service center pricing?

MU2's routine "big" inspection is every 600 hours or 3 years (they don't have lettered "checks"), I hit the 3 year limit first. This is an additional $3800 base charge (over the routine 100 hour/1year/2year inspections, ~$5K) from my mechanic. Just had it done last week.

Mike C.

D check occurs every 2 years, and 12 years ago it was $21K each base rate?

That seems excessive, or is that gold plated service center pricing?

MU2's routine "big" inspection is every 600 hours or 3 years (they don't have lettered "checks"), I hit the 3 year limit first. This is an additional $3800 base charge (over the routine 100 hour/1year/2year inspections, ~$5K) from my mechanic. Just had it done last week.

Mike C.

Outstanding feedback as always Allen. The real cause for concern regarding the MX costs you summarize above isn't the costs, it's the frequency of MX events. I count roughly 7 MX events per year over this 2 year span. If you have an outstanding service center on your field or at your base of operation, this is no big thing. However, if you have to get her to a shop off-field 6-7 times / year, this would be bonkers. The time involved in maintaining a bird like this is a much bigger factor than the number and size of checks written, at least to me.

The Twin Cessna organization has just opened up a section for Cessna Conquest owners. The site is at www.twincessna.org

Max