Jetprop conversions - any disadvantages?

[VMC-on-top]

Jetprops, ie piston engine aircraft converted to turbine seem tremendous value for money as far as I can see. Are there any major disadvantages over the equivalent piston engined / turboprop (putting aside the initial cost obviously).

For instance, Malibu piston:-
manages about 210 to 220 knots true airspeed up at about FL230 while consuming about 22 to 24 gallons per hour. It needs about 2,550 feet of take-off space to clear a 50-foot obstacle and climbs at about 1,200 fpm.

The aircraft converted to the JetPROP DLX turns in between 250 and 270 knots true, can cruise as FL270, consumes about 30gph and needs 1,200 feet of runway to clear that same obstacle!!

The Bonanza Jetprop sees similar increase in performance ie. 25gph at 250knots, 1,000 feet TODR!

The figures seems quite remarkable and when you consider, in the Piper's case, the Meridian's (turbo prop) purchase price is substantially higher (as much as twice?).

Presumably, there are major drawbacks? Are they, maintenance, insurance, shortened airframe life - anything else?

[IO540]

Yes, the JP is a rocket.

The downside depends on who you ask.

Socata and Piper dealers will slag it off, saying that rivets fall out of the tail end, people fly them with the Vmo warning circuit breaker pulled out, etc. There is a little bit of truth in this which is why you may want to buy a more recent PA46 airframe which Piper reinforced (because, being Piper engineering, the rivets were coming out of the Malibu versions too :) ).

As for Socata, the JP is probably under 1/2 of the total operating cost per mile of a TBM, and that is if you buy a £1M plane (which will be a nice one) - about the same as a £1M TBM (which will be a bit of a dog).

I know one owner who did considerable due diligence on the airframe versions. This is probably desirable. Some years are relevant; can't recall which but something like 2002 or later is what you want.

The downside of that era of PA46 is that it came with the wonderful KFC225 autopilot whose half life is highly variable :) It's OK if you are a smart pro-active owner who can manage the maintenance, is willing to fly with a box of spare servos, and tolerate maybe 1 failure per year. Honeywell have washed their hands of this product, and all OEM customers designed it out as fast as they could unscrew them. But when they work they are among the very best out there and much more accurate than the STECs. I've got one :)

I think it's a very good plane for a technically clever pilot who can manage the power. The thing can bust Vne during the climb... mind you, the FAA set the Vne (expressed as IAS) at the top of the yellow arc, as is customary on TP conversions. Only the huge TAS gain at FL270 gives you the great cruise speed.

I'd buy a JP as a logical upgrade from my TB, and skip the whole piston turbo stage, with cracking cylinders, etc.

[Ozzy Unlocked]

Most of the reasons why not everyone flies with a turbine-powered aircraft were already given by IO540.

A turbine conversion also comes with less range, less useful load and turbine efficiency only at 25k ft. Means: anything less you will have to buy with less speed and higher fuel consumption.

Also, you will lose flexibility: in a piston-powered PA46 you simply fly a lot lower if on FL250 you'd have have an 80-knot headwind blowing. In a turbine-powered PA46, you don't have this option. I am not sure where it breaks even, but it simply takes away a lot of flexibility and choices you had before.

If all planes would be equipped with turbines and tomorrow somebody would invent the piston-powered engine, many people would change just to avoid this disadvantage.

A great part of private flying is about flying low, enjoying landscapes and the flexibility you have with a piston-powered engine. With turbine-engines you loose this advantage.

[Big Pistons Forever]

The DLX jet prop has a very low payload load with full fuel (can be less than 300lbs) and there is no yellow arc on turbine aircraft. Therefore the redline VMO speed is reduced to the Vno top of the green arc speed. This can be a significant limitation when flying at low altitudes. Finally Piper significantly increased the size of the tail in the Meridian. The JP has a reputation for having marginal longitudinal stabilty at higher altitudes.

[BackPacker]

A great part of private flying is about flying low, enjoying landscapes and the flexibility you have with a piston-powered engine. With turbine-engines you loose this advantage.

Yeah, and turbines are not that happy with aerobatics either. But could you do this with a piston-powered engine?

Flight of Imagination - Flight of Imagination (http://www.flightofimagination.nl/)

(PH-LUX is owned two members of my flying club and in total there's four or five club members who have the TR.)

[IO540]

For some real owner views, go to jetprop.com.

The Meridian is much heavier than the JP - about 2300kg versus 1999kg. This translates into a substantial IFR operating cost advantage in Europe - of the order of £100 plus for a flight across France.

Re flying at altitude... well, yes, if you want to go A to B seriously, with a decent despatch rate (up in the 90s %) then you have to be doing exactly that. The objective is a rapid climb to VMC on top. Only relatively impoverished piston twin owners, without turbos or oxygen/pressurisation, will be sitting at 5000ft, with the deicing boots working overtime, with the whole thing bouncing around... And most piston twins are > 2000kg so you pay the route charges as well, unless you file "VFR" which of course never happens ;) The JP is not for local bimbles; neither is the TBM.

[nouseforaname]

My Dad owns a Cessna P210 Silver Ealge it's basically a P210 with the old piston engine taken out and replaced with an RR Allison 250 (b17 to b exact).

I0540 has basically covered every point that makes pressurised turboprop aircraft better than a piston. One thing I will say with the Allison 250 even at low levels it doesnt exactly drink fuel, about 27gph of jet which is still cheaper than our turbo piston 182 that we still have whilst doing 180kts at low level. When we gut up to 20k we do about 210tas and 22gph. Regular trips to Ireland cost us about £55/hr on fuel whilst there is no airway charges and, like I0540 said, we v rarely get put off by the weather or freezing levels even in the depth of winter

[englishal]

Of course they CAN fly at low levels, and if someone else is picking up the tab, very nice to do too ;) But a B200 has a DOC of something like £10 per minute, so if money is an object, perhaps it is best to avoid one and stick to the SEP....

[VMC-on-top]

I'm no expert on the performance of turbines at different altitudes but surely with the cost of A1 being less than half the price of AVGAS, the fuel cost per mile must be way cheaper with a turbine - even bearing in mind the higher fuel consumption?

[IO540]

Around 2002 when I got my TB20 I was talking to a TBM700 pilot. It turned out that the TB20 cost about the same in fuel cost per mile as the TBM700.

The TBM fuel flow (kg/hr or whatever) was about 4x higher but the fuel was half the price and the plane flew twice as fast.

Obviously there are other costs. The TBM is massively more expensive to maintain. The overall DOC, based on say 200hrs/year, was about £400/hr for the TBM and about £70/hr for the TB20, and that ignores depreciation. (if you take dep into account you will stay in bed and invest all your money in financial instruments, and die very rich not having done anything).

However, because a TBM flies 2x faster, a busy traveller is a lot less likely to be doing say 200hrs/year in a TBM than in something slower. So a decent cost comparison is hard to do, for somebody moving from one to the other without a concurrent big and appropriate change in mission profile.

The higher speed, resulting in less time spent flying, also impacts pilot currency. A lot of the time that I see a TBM land somewhere, I see the owner/pilot step out, followed by an instructor, and a lot of the time it is an instructor that I happen to know, who does this more or less for a living. A lot of TP owners do fly with instructors a lot of the time, because they realise they have insufficient currency.

So I think a TP is a great tool for a serious distance traveller but probably not a good choice for a piston pilot who does say 150hrs/year of which only a proportion is done on long trips. If somebody gave me a TBM, my 150hrs/year would shrink to about 30-50, because the long trips would be done in half the time, and the intra-UK flying and local cloud-drilling I would not do anymore because who is going to be cloud drilling at £500+ per hour?

So one's currency goes down the pan. You spend a lot of time on the recurrent training treadmill, flying with instructors (who often make you work really hard; I've done that myself), or going to Flight Safety (which isn't going to be easy, or cheap, I bet) and spending time on a sim. Some people like this but, personally, I like to just damn well FLY, and keep current doing that, not spend half my time banging approaches under the hood.

I don't for a moment believe that flying a SE TP at 270kt TAS is any harder than flying a SEP at half that speed. And the stall speeds, and therefore approach speeds, will be similar. In both cases you cannot do a "Cessna 150" i.e. join the circuit at your cruise speed :) You have to plan ahead and manage the energy, in both cases. But one isn't going to be current in either type at 30-50hrs/year.

The final thing is matching one's mission profile to the plane. It doesn't matter how much money you have - if you fail to do this, you will be for ever miserable, wondering why the hell you got into this. I know of a few TBM owners who are wishing they had not done it.

[englishal]

I think the key is....if you have bags of money, just buy one :O

If I had millions, I'd buy a VLJ like the Phenom, not because I cared about the money, but because it is cool and would be fun. I suppose for the same reason people buy 911's etc....you know the minute your drive off the lot, you have lost £30,000, but who cares if you have that kind of money!

Speaking of which, it is lottery night tonight, so hopefully I can place my order in the morning :}

[IO540]

If I had millions, I'd buy a VLJ like the Phenom, not because I cared about the money, but because it is cool and would be fun

I can guarantee, Englishal, that unless you have enough money to pay someone to look after it, and employ a crew to fly it, you would get sick of it in no time at all.

One day you would wake up and say to yourself "why am I doing this... running a bl00dy airline" and you would chuck it all in.

I know a bloke who did just that :)

In flying, the return (fun, utility, whatever) has to exceed the hassle, by a comfortable margin, otherwise 100% of people chuck it in, usually within a year. Vast amounts of money can buy out the hassle, but aviation at this level is going to be one massive hassle so basically you are paying others to deal with the hassle.

Aviation ownership is a huge hassle at any level, and I can only just imagine what crap one would have to deal with being the owner/operator/pilot of a jet. Take a year out of your life for starters to get the paperwork so you can fly it PIC...

But then you may as well buy a Netjets hour block... at least the pilots will be reasonably current, and the bird you will be taking down to Cannes will be beautiful enough to be dumb enough to believe you when you tell her it's yours :)

Surely you can buy a 911 for under £10k these days... and the kind of bird you will pull with that will be too dumb to not realise it is an old wreck :)

[englishal]

:}:}

Well it is academic now as I didn't win the lottery, but you are probably right. The rich folk I have met in the USA who own jets employ pilots to fly them, so they can sit in the back with a G&T. They may venture up front for an hour before they get bored. If you have that kind of money, just phone Netjets and order a G5 for the day :D

[Seat 22C]

We fly a king air at low level when necessary, and regularly at FL100 or so. The fuel burn is not an issue. The concept that a turboprop cannot fly at lower levels to get out of the wind is a red herring.

Agreed. The JetPROP DLX burns 32-35 gph at FL100 and 32-35 gph at FL270. The difference is that at FL100 it's doing less than 200kts and at FL270 its doing 260kts.

So why would a DLX owner *want* to fly at FL100?

[Daforty]

Sometime I fly low in my DLX (N22CX). I have a "milk run" that I do several times a month that's only about 100NM and sometimes stay low to stay under the Dulles inbound traffic - when under IFR, the approach controllers usually won;t let me get much above 9K on the route. Of course, when the weather's good I usually shoot right up to 14 or 15 thousand (it really is amazing in climb) and then come back down after a couple minutes at cruise. Fuels is about the same either way.

The only other time I've deliberately flown low was on a Trip from DC to Dayton - 20 knot headwinds at 10000 feet, 100+ knots in the flight levels.
And yes, the fuel consumption is the same but in this case it was 175kts GS at 10K vs 150kt at FL250.

[Bill Watkins]

The jet prop is truly a wonderful airplane. I have a 1986 pa-46 converted in 2003 with -21 prat. This airplane is lightest of pressurized jets. Its greatest qualities in descending order is 1. It's 2000 feet per minute climb is great. 2. It's 27000 service ceiling is next. 3. Pressurized and air conditioning is next. 4. Fuel burn averages 30 gph including climb, cruise and decent. 5. It's long range cruse averages 235 knots. Now one has to say that is a great package.
One climbs on top in 10 minutes and enjoys lots of wonderful qualities.

[veetwin]

Can anyone give me an approximate cost for the conversion of a Piper Malibu Mirage to a Piper Jetprop?

[Desert185]

Seat 22C:
Quote:
We fly a king air at low level when necessary, and regularly at FL100 or so. The fuel burn is not an issue. The concept that a turboprop cannot fly at lower levels to get out of the wind is a red herring.
Agreed. The JetPROP DLX burns 32-35 gph at FL100 and 32-35 gph at FL270. The difference is that at FL100 it's doing less than 200kts and at FL270 its doing 260kts.

So why would a DLX owner *want* to fly at FL100?

Agreed, again.

I fly an airborne science DC-8 with planned enroute cruise fuel burn of 12,000 PPH. Much of the time we fly 500' over water and 1,000' over land. The planned fuel burn? 12,000 PPH. If we do a lot of vertical profiling up and down, the average burn increases slightly to maybe 12,600 PPH. The difference is a slower speed and reduced range because of that slower speed, but the burn essentially stays the same.

[jecuk]

To convert a piston PA-46 to Jetprop is at least $600,000. They are good planes, but different from a Meridian. Many systems such as environmental remain the piston version. You can have differing views on whether that matters.

Best not ask about W&B though....