...that's because someone peed in it!

...but it’s still warm

Williams specifically prices off program maintenance to be HIGHER than being on the program by about 30%. Williams is the only place you can get those major events done, so they control all the pricing and rules. Unless you consider the plane to be disposable, being on the program is the cheaper way with Williams.


You can't "come out ahead" with Williams. When you hit HSI or OH (aka "MPI 3" or "MPI 4"), you will end up paying more than if you had been on the program. And that is if nothing is wrong with the engine. If they find major issues, you will pay even more.


For the JT15D, being off program is best since you can find use engines and shops that do the major work independent from Pratt.


There is (or at least was last time I checked) ways to remove the 150 hour minimum. That involved paying in a 300 hour balance to Williams and topping that up each anniversary. This is not part of the standard contract, you have to ask for it, and Williams doesn't promise they will offer it on a continual basis. They make the rules and can change them at any time.

For a program price of about $350/hour for a pair of engines, a 300 hour pay in is about $105K, so not a trivial balance to keep, but if you fly less than 100 hours/year, paying for hours you aren't using is worse.

Also, the Williams contract allows you to fly under the 150 hour minimum 1 year in 5 without penalty. You don't get to choose that year, it is the first one you fly under the minimum. So don't have a 149 hour year, make sure you have a 150 hour year and save that "get out of minimum" card for another year where it is more valuable.


This is proof that the TBO extension is purely a business decision on the part of Williams. You can enroll in the program at 4000 hours, and suddenly your engine is good for another 1000 hours. How the engine knows it can work longer because you sent money to someone is beyond me.


Williams gets high marks for customer support.

If you think the Williams program price is expensive, price out the Pratt program for the PW500 series that is on the Bravo, Encore, etc. It is close to $500/hour.

When I compared JT15D versus FJ44, the JT15D wins if you TBO extend it and/or can get used engines so that you get hours cheaply to make up for the extra fuel burn. If you have to do HSI/OH on the JT15D nominal schedule (1750 HSI, 3500 OH), then the FJ44 on program wins due to fuel savings, plus having unscheduled maintenance insurance. If you can't handle a major unscheduled event, then the FJ44 on program wins for sure.

The only time FJ44 off program wins is if the plane was bought for almost nothing and you consider the plane and engines disposable at the first major event, and you don't have any major unscheduled events. The most amount of time you can have to the next major event is 2000 hours.

Mike C.

Williams specifically prices off program maintenance to be HIGHER than being on the program by about 30%. Williams is the only place you can get those major events done, so they control all the pricing and rules. Unless you consider the plane to be disposable, being on the program is the cheaper way with Williams.


You can't "come out ahead" with Williams. When you hit HSI or OH (aka "MPI 3" or "MPI 4"), you will end up paying more than if you had been on the program. And that is if nothing is wrong with the engine. If they find major issues, you will pay even more.


For the JT15D, being off program is best since you can find use engines and shops that do the major work independent from Pratt.


There is (or at least was last time I checked) ways to remove the 150 hour minimum. That involved paying in a 300 hour balance to Williams and topping that up each anniversary. This is not part of the standard contract, you have to ask for it, and Williams doesn't promise they will offer it on a continual basis. They make the rules and can change them at any time.

For a program price of about $350/hour for a pair of engines, a 300 hour pay in is about $105K, so not a trivial balance to keep, but if you fly less than 100 hours/year, paying for hours you aren't using is worse.

Also, the Williams contract allows you to fly under the 150 hour minimum 1 year in 5 without penalty. You don't get to choose that year, it is the first one you fly under the minimum. So don't have a 149 hour year, make sure you have a 150 hour year and save that "get out of minimum" card for another year where it is more valuable.


This is proof that the TBO extension is purely a business decision on the part of Williams. You can enroll in the program at 4000 hours, and suddenly your engine is good for another 1000 hours. How the engine knows it can work longer because you sent money to someone is beyond me.


Williams gets high marks for customer support.

If you think the Williams program price is expensive, price out the Pratt program for the PW500 series that is on the Bravo, Encore, etc. It is close to $500/hour.

When I compared JT15D versus FJ44, the JT15D wins if you TBO extend it and/or can get used engines so that you get hours cheaply to make up for the extra fuel burn. If you have to do HSI/OH on the JT15D nominal schedule (1750 HSI, 3500 OH), then the FJ44 on program wins due to fuel savings, plus having unscheduled maintenance insurance. If you can't handle a major unscheduled event, then the FJ44 on program wins for sure.

The only time FJ44 off program wins is if the plane was bought for almost nothing and you consider the plane and engines disposable at the first major event, and you don't have any major unscheduled events. The most amount of time you can have to the next major event is 2000 hours.

Mike C.

Holy thread resurrection batman

I have just finished reading this entire thread, and have read many of the same points from many other threads over the past year. One of many ways I have tried to approach the Williams Tax is with fuel burn. I am interested in a 550, S550, Stallion, Super 2 and Super S2. Since there are two options for engines on these jets, JT15's and FJ44's, is looking at the fuel savings / TAP cost delta sensible?

My research shows a 149gph vs 177gph block fuel average for a Super SII vs an S550. On a typical trip of mine, SGR to JAC(1150nm) I see about $140/hr in fuel savings at $5/gal, and considering 420ktas vs 385ktas. That could be higher or lower depending on real world data, fuel prices and others I'm not considering. It seems like a logical and sensible approach to offset the engine program cost by this amount, leaving an actual cost of around $200 per hour. To have most of the engine maintenance already paid for and additionally have insurance for a catastrophic event, it doesn't seem like that big of an issue, and in many ways ads some stability to a lot of expensive unknowns.

I have tried finding a Foreflight profile for a Stallion, Super S2 or a Super 2 and can not find one. The S550 profile I have found reduces this delta, showing the actual block fuel for the S550 to be 154gph. From the cruise and climb efficiencies I have read on the Williams powered jets I suspect it too has a lower GPH block total, so this may be offset. Regardless they are clearly more fuel effecient engines and this to me seems logical to offset the engine program costs.

A few other questions I have are:

What are current TAP program costs and any change to the 150hr min policy? Sure would be nice if that was 75 hours.

What would the estimated current cost be to dump engines that are at OH and purchase used -4s that have 1000 left tell OH? Can I convert to 4b's for cheap or reusing existing parts?

What is average estimated cost of a JT15-4b HSI at time of typical overhaul on 7000hr engine. What is average estimated cost of OH at 7000hr engine that had OH at 3500?

Anyone heard of bird strike that takes out engine inlets on FJ44's totaling the plane? I have heard the inlets are third party and that company is gone... Insurance buys the plane...

Any change in the idea that the legacy Citations are disposable in the current markets, especially with new avionics, interior and paint? What is the value of a 550 or S550 with no engines and avionics, interior and paint in like new shape?

The current policy, last I understood it, is that you could select one of two options that you select at contract time, and thus locks you into that choice for 5 years.

The "standard" option is you pay the base rate for each hour flown and there was a 150 hour per year minimum. If you didn't reach 150 hours, you are forgiven for 1 year in the 5 year contract. The next time it happens, you owe the difference to 150 hours.

The "low use" option is you pay for 135 hours up front at the start of the year. Then you can fly 150 hours at no additional cost. Once you hit 150 hours in that year, then all hours above that are charged at 135% of base rate.

I made a chart to compare the two based on your yearly hours:

The crossover point is 193 hours. If you fly less than 193 hours in a year, the low use plan is cheaper. If you fly more, then the standard plan is cheaper.

The base rate is now approaching $200/hour/engine. Williams can increase this cost every year and does so. Many years ago the contract limited the increase to inflation (CPI-W), but that was removed and now Williams can jack the rate at will any amount they feel like. The rate has been going up faster than inflation.

There are many gotchas in the Williams terms. For example, if you fall off program and then want to rejoin, they do not consider all the prior payments, they are gone, and you have to pay up back to hour zero. The contracts are 5 year terms, but Williams is under no obligation to extend the contract to you, they could just drop you. Williams can also change the terms every 5 years to their liking and have done so many times.


That is the wrong approach. You would take the JT15D-4B engines and do HSI and fly them past OH. That is the cheapest option assuming you are not cycled out on your life limited parts.


I don't know those figures precisely and it will vary with engine condition. I'm led to believe HSI is not terribly expensive if your parts pass.

At 7000 hours, you need to be aware of some life limited parts, like the impeller which often is a 9000 cycle life and expensive to replace.


There's a healthy used parts market for such airplanes, so it will be worth something. Used parts have gone up in price with the increased flying and supply chain issues.

Mike C.

It is just beyond comprehension that aviation is still the only business where you leave the keys at the engine shop and you have no clue if it's going to be $1K or $1Million? Google "PT6 overhaul costs" and come back to me with a cohesive number. It can't be done.

Why is this accepted? Why is it so %#$@? It's simply unacceptable.

There are some major OH shops for PT6 engines that have a cap of what the cost will be, not every engine applies. When was had a -135 I believe the cap was $292k/engine about 3 years ago.

-Citation Jet Exchange

When we had our King Air, there was a local, highly experienced P&W guy that would act as your advocate. He would be there when they tore it down and give feedback on what he thought was and wasn't necessary. He could give you very good probabilities based on engine times and how you ran it. There are also shops that have access to secondary market parts for the part 91 folks. If one is really pushed for usage and goes to the factory shop, it's pretty open ended and you always get the: you might as well do it now while we have it apart call.

I fly fadec Williams on a beech product, IMHO the original prat version isn’t a realistic plane today, the failure points the fuel burn lack of range etc, just a plane that needs to go to pasture, parts, or williams upgrade

The FJs have been trouble free, the only issues we have had with the planes have been all the other parts lol

The Williams powered Beechjet is one heck of an airplane!!!

Hawker 400XP / FJ-44 / Garmin G5000 that's a machine!!!

The Williams powered Beechjet is one heck of an airplane!!!

Hawker 400XP / FJ-44 / Garmin G5000 that's a machine!!!

The Williams powered Beechjet is one heck of an airplane!!!

Hawker 400XP / FJ-44 / Garmin G5000 that's a machine!!!

Climb to FL410 loaded ain’t no thing, high and hot isn’t as much of a deal, full fadec, NE to SE US in one shot, it makes it a real working airplane in 2023


Only draw back is no TRs combined with the original very antiquated antiskid brake system, plus still needing to be 2 crew

Pretty much all the BE40s and BE4Ws that become tin cans, it’s from a runway overrun

But overall they are a damn good bang for the buck if they are taken care of

Climb to FL410 loaded ain’t no thing, high and hot isn’t as much of a deal, full fadec, NE to SE US in one shot, it makes it a real working airplane in 2023


Only draw back is no TRs combined with the original very antiquated antiskid brake system, plus still needing to be 2 crew

Pretty much all the BE40s and BE4Ws that become tin cans, it’s from a runway overrun

But overall they are a damn good bang for the buck if they are taken care of