Jetprop 900 vs 1000

[Achim H.]

When comparing a Jetprop 900 with -10 engines and the stall warning STC for FL350 and RVSM to a Jetprop 1000 -- what differences remain? Larger gross weight on the 1000 but where does it come from? Structural modifications or only paper? Anything else different?

I'm trying to get a better understanding of how the 900 with all modifications compares to a 1000.

Thanks!

[donv]

I think the difference is that the 1000 had a higher takeoff horsepower rating. I'm guessing that the -10 conversion on the 900 doesn't change the takeoff power, but I could be wrong about that.

Someone like Bruce Byerly or Norm Ralston would know the answer, for sure.

[Achim H.]

On http://twincommander.com/models/ac1000/ I found this:

The model 1000 is the most advanced version of the Twin Commander. The first version of the 1000 (695A) was certified in April, 1981 and was the same aircraft as the model 900 except that it used Honeywell TPE331-511k engines, better known as Dash 10. In February, 1984 a second version of the model 1000 was released (695B) that used Dash 10 engines, raising shaft horsepower output to 820 per engine. This gave the aircraft a maximum cruising speed of 308 knots and maximum range of 2,080 nautical miles on 482 gallons of fuel. The maximum ceiling rating increased to 35,000 feet. Weight ratings also increased slightly over the model 900. Minor structural changes were made to the 1000 to accommodate the increased weight ratings and engine power.

It says "minor structural changes [...] to accommodate the increased weight ratings and engine power". Is that for all 695 or only from the 695B with the 820hp power output? How much power does a -10 converted 690D have?

I'm trying to find out if I should be looking for 1000s or also for 900s. Actually I like the takeoff weight of the 900 because it is below 5 tons which would be more economical in Europe.

[donv]

There were structural changes between the 695A and 695B. However, I'm pretty sure the 900 is the same structure as a 695A-- heck, a really late 900 might even be the same as a 695B, but I wouldn't count on that.

Bruce Byerly would now-- send him a message. He's a member of this site.

[Adam Frisch]

The last 57 models produced, from both the 690D batch and the 695B batch had the 511K engines, whereas the normal -10 engined ones had the 501K. I think they had a slightly higher thermal rating and a little more poke up high, but we're talking marginal here. The 1000 probably ate any slight performance edge with the higher rated engines up by being heavier.

I've asked Bruce to chime in.

[donv]

I've never really understood the difference between the 501 and 511, although I think all the airplanes have long since been upgraded to 511.

However, none of this is relevant to the 900 (690D), since the definition of a 900 is a 1000 with -5 engines. Any 900 with -10s was upgraded.

[Bruce Byerly]

Ok, I'll take a quick stab.  Don't worry about 501's (can't even remember seeing one of those) vs 511's or confusing 513's, 515k's etc. until you get to a specific plane and a detailed review of engine status and history.

Sounds like a -10 900 might be best if the 10,775 gross makes a big difference.  A -10 900 is typically rivet by rivet identical to a 1000 with the exception of the higher TO TQ rating, lack of SRL computers, and, potentially, lack of the goofy high altitude stall warming system which would be required for RVSM.  Real world, a -10 900 is effectively identical at cruise and in every meaningful way and the power difference down low is something one easily could "work around" if an emergency situation required it.  There are many other considerations of course, but that's the short version.

I noticed somewhere along the way that you said it might have to sit outside.  That would not be a good situation for any plane of this age or class.  Financially, you'll be money ahead in the hangar in my opinion. 

[donv]

I agree completely with this. You really don't want these airplanes to sit outside for extended periods.

I noticed somewhere along the way that you said it might have to sit outside.  That would not be a good situation for any plane of this age or class.  Financially, you'll be money ahead in the hangar in my opinion.

[donv]

Bruce, do all 900s have the left and right CB panels and pedestal-mounted pressurization panel, like the 695Bs? Or are there "early" and "late" 900s?

[Achim H.]

Is there anything about the Commanders that would make them less suitable for being stationed outside than other pressurized turbine aircraft of the same age?

All my aircraft have had hangars and I agree it's not smart to try to save money by letting it sit outside but sometimes there isn't any choice.

[Adam Frisch]

Achima, I'm assuming you would have a comprehensive and good cover made up for it, right?

[Achim H.]

I assume the windscreen would get some protection as well as turbine inlet and exhaust but putting on a large cover is very difficult, even my current C182 requires two people and it's hardly possible when there's some wind. I don't think it would be practical on a Commander.

There are lots of turbine aircraft sitting outside and all airliners are outside. It should be OK for a pressurized aircraft, in a non corrosive environment. Not ideal for sure but sometimes one doesn't have a choice.

So unless there's something specific to the Commanders that make them less suitable for staying outside than comparable aircraft, this is what I will have to do.

[donv]

I don't think there is anything specific to the Commander which makes it an issue. If no hangar is possible, then I guess you do what you have to do.

If it's a budget issue, plan for a new paint job much more frequently (if it's hangared, paint can last almost indefinitely, but outside you are probably looking at a 5 year life). In a dry place, that's probably the main thing you need to worry about. If it's damp, then you may see additional maintenance issues from corrosion, water leaks, and interior mildew/wear.

I have a nice set of inside windshield covers which came with my airplane, and that seems to help keep the interior temperatures reasonable when parked outside in the summer.

[donv]

One other thing: airliners typically don't sit idle for days at a time. That makes a big difference-- if you're flying it every day, it's going to be a lot better than if it sits for a week, flies a day, sits for another week, etc.

[Achim H.]

I would put it on the waiting list for the $2,200 / month unheated hangar but no guarantees even though it should stack very well with most airplanes in the hangars being low wing. Crazy pricing but what use is a plane if takes over an hour to drive to it? The metropolitan areas are difficult for GA, the countryside has great GA airports.