Does anyone know if N31TT, the Aerostar with turbine engines is coming to Oshkosh? It was on EAA’s FB page today.

Unlikely
Jim Christy flew it out the year it was done.
But, absent a bunch of money to get it certified (@ a higher differential and altitude) the economics of bringing it out again aren’t that favorable.

Thank you. I saw that it had flown for about 18 minutes, with a quick pop up to 10,000 and back down a few weeks ago. I was hoping it was getting ready and would be out there again. It’s been about a decade and change since it was last out (2011/2012?). I missed it in 2013. I was going to come this year but had some things come up that will prevent the trip this year. Hopefully I will be able to take the time off next year.

Though, if N31TT was there, I was planning a day trip up from Chicago or Milwaukee to see it.

Actually, there's a question I'd like your opinion on, Forrest: Given a choice between chopped props and winglets on a 600, which would you choose?

Knowing you, your answer is: both!

But seriously, if you could only have one or the other, which would you pick? I'm asking because unlike what that seller told Frank, there's very little improvement at cruise speed with winglets; they're primarily more lift at low speed. So assuming you're doing heavyweight takeoffs from short runways on hot days, would you rather have winglets or the twenty extra horsepower you get with short props and 2,700 RPM?

Ignore the MTGW bump you get by putting the wing extension on before the winglets. An apples to apples 600 at 5,500 lbs. Options 275 + 277 v. Option 249.

Just curious...

Actually, there's a question I'd like your opinion on, Forrest: Given a choice between chopped props and winglets on a 600, which would you choose?

Knowing you, your answer is: both!

But seriously, if you could only have one or the other, which would you pick? I'm asking because unlike what that seller told Frank, there's very little improvement at cruise speed with winglets; they're primarily more lift at low speed. So assuming you're doing heavyweight takeoffs from short runways on hot days, would you rather have winglets or the twenty extra horsepower you get with short props and 2,700 RPM?

Ignore the MTGW bump you get by putting the wing extension on before the winglets. An apples to apples 600 at 5,500 lbs. Options 275 + 277 v. Option 249.

Just curious...

My apologies, Walter. I didn't think anybody had tricked out a 600 to that extent. Now I'm well jel...

To answer the question:

Winglets

Not because they will increase cruise speed (although they may) but because they will improve single engine performance.

There is a debate (well, there used to be) over the advantages of a 700 -short props higher rpm vs. a -680 long props lower max rpm.
The long prop advocates said the 680 accelerated faster because the long props generated more thrust. The short prop folks believed more HP equals better performance.

I think the winglets are an excellent upgrade for every Aerostar.

Unbiased view........The 680's rock! And they also hold a couple of speed records.

Forrest,

Minor knit pick. If you fly at or near Carson speeds I have seen this referenced as Lz), winglets will give you a few more knots.
But in an Aerostar, unless you are attempting a long range mission or best economy, this seems to be way to slow and you would never really see the benefit.

Tim

Vz = 154KIAS

The winglets biggest performance benefit is at high angles of attack.

Rotation, high altitude, heavy, low power cruise, and operation after an engine failure.

There is a fairly steep increase in induced drag as IAS drops below Vz.

Which means airspeed isn’t stable.

Note:
I’m not an aerodynamic engineer but here’s the deal as I see it:

Two kinds of drag -parasitic-drag that comes from pushing the airplane through the air
It increases with more indicated airspeed.

Induced drag - drag that comes from keeping the airplane in the air, and the drag that comes from the downforce from the elevator (and from ailerons).

Parasitic drag makes for stable airspeed if the plane slows a bit, the drag decreases and the airplane gets back to speed.

Induced drag is more complicated, and depends on the design efficiency if the wings and elevator at a given speed.

Back to the question:

Ted Smith designed Aerostars to go fast, he used a wing that works great at cruise, but it’s a wing that isn’t very efficient at slower speeds.

That means slow flight takes a fair bit of power, and cruise at less than 140 indicated is frustrating because the increase in induced drag is greater than the decrease in parasitic drag, when the plane slows, it tends to go even slower.

Worse, on my turbo normalized 601P, up high, my waste gates are closed, so less airspeed equals less MAP.

Winglets fixed all these problems by reshaping the lower indicated airspeed portion of the induced drag curve to perform more like the higher speed portion of the drag curve and that makes it possible to comfortably set economical cruise power settings.

I think this would be a big deal on a 600 as well because it’s normally aspirated engines are going to lose power with altitude.

IMO the hot ticket (for a 600), would be an oxygen concentrator (to avoid having to refill the O2 tank), winglets, and electronic ignition (with spark advance).

Run around in the mid teens (<18K’) when winds are favorable, no turbos to deal with, fast, economical transportation.

On the other hand, pressurization is wonderful.

Walter, do I even need to ask whether you've got e-mags?

That's the one good thing after having to wait so long for the 600 to be added to the AML. When SureFly finally got them approved last year, timing advance was included.

But I don't understand why you think I should be flying up in the teens, Forrest. Sure, if I'm eastbound on a long leg and there's wintertime low altitude howling jetstream, Ill go up for the hundred knot tailwind. But I didn't even take the bottle along on the most recent trip out to Vegas. What am I missing?

Do you spend much time flying up in the teens, Walter?

The great majority of unpressurized piston GA aircraft are at 12,500’ or below.

Commercial Jets normally cruise in the 30s.

Starting @ 15,000’-17,000’ airspace is pretty much wide open.

Weather (and winds) permitting, flying at those altitudes makes for a cool and smooth ride.


With 5.5 pressurization, cabin altitude @14,000’ is about 1,000’.

Easiest is the pick a VFR altitude (15,500, 16,500, 17,500) and go direct with flight following.

There are times when ATC routing for a flight in the low to mid 20s makes it worth descending to 17,500’ and canceling IFR (ATC clears descending to 17,000’ and cancel at 17,500’)

I often cancel IFR and go direct w/FF going between Norfolk VA and Danbury CT.

Out of courtesy, I tell ATC before changing altitude, and normally I get permission to descend into the NYC Class B once I’m north of the City.

My thinking is that if O2 is easy(ier) in my hypothetical ultimate 600, pilots will choose to go high more often.

From experience, up to 30Kts, I rather fight a head wind up high than deal with the bumps and bugs (and birds) down low.

Walter, do I even need to ask whether you've got e-mags?

That's the one good thing after having to wait so long for the 600 to be added to the AML. When SureFly finally got them approved last year, timing advance was included.

But I don't understand why you think I should be flying up in the teens, Forrest. Sure, if I'm eastbound on a long leg and there's wintertime low altitude howling jetstream, Ill go up for the hundred knot tailwind. But I didn't even take the bottle along on the most recent trip out to Vegas. What am I missing?

Do you spend much time flying up in the teens, Walter?

Yeah, 15-17000ft was kinda my sweet spot too when I had mine. Very rarely did you have much traffic at those altitudes.

16,500 or 17,500 unless the weather is not VFR...
Direct right over all the class bravos,
Above the bumps (although I've been in bumps at 17500, buts its really rare.)
Almost no traffic outside of the terminal areas...

The plane is really happy there.