Rockwell Turbo Commander

[Jmmccutc]

my question regarding the turbo commander is this...is that the only name for it? we used to have one in the hangar of the airport i used to work at, it had "DASH-10" painted on the tail of the plane, i wasn't sure what this was or if maybe it was something about the engines...thanks

jake

 

[pilotyip]

conversion

Most likely a TC-690A or B that came new with -5 engines from the factory, someone is putting the -10 on them as a retrofit. It makes a great airplane, a fantastic one. The TC was one of my favorite airplanes to fly, from a pilots point of view I would take it over a King air any day, and I have 2500 hours in King Airs.

 

[jergar999]

Dash 10 means that the engines are Dash-10 Garretts. Some Commander models came from the factory with the Dash-10, but most come with Dash-5's.

To second pilotyips comments, I fly King Airs full time and have a part time Commander gig with a local company. The Commander outperforms the King Air in almost every category except room and useful load. They are a blast to fly, even with the Dash-5's.

 

[Cat Driver]

Flew a 690B part time for a couple of years it is my very,very favourite little airplane.

Truly a pilots dream

Cat Driver

 

[satpak77]

To second pilotyips comments, I fly King Airs full time and have a part time Commander gig with a local company. The Commander outperforms the King Air in almost every category except room and useful load.

In other words the Commander cannot carry what the King Air carries nor does it have the room. The commander does outperform the King Air in other areas, however only when it is not down in the shop for maintenance.

 

[jergar999]

Originally posted by satpak77
"In other words the Commander cannot carry what the King Air carries nor does it have the room. The commander does outperform the King Air in other areas, however only when it is not down in the shop for maintenance."

Agreed. My King Air job is an air ambulance one, and there is no way the 690 could carry everything we need to carry, both bulk and gross. Both airplanes have a niche. I don't think I would enjoy trying to load a patient, nurse, medic, family member, and full portable trauma room in a Commander, but for hauling a few company folks around the country it does a beautiful job. And in all fairness, I have only flown a straight C90 and an A100, so that is all I really can compare the Commander to. If the performance numbers are correct, a B200 would be roughly 10% faster than the 690 at 10% higher fuel flow. Considering there is almost a ton difference in the weights of the two, I would think the King Air might be more cost effective and efficient if you were to fill it up.

As for maintenace issues, that I haven't had to deal with. When I started flying for these guys the airplane had just come back from Eagle Creek Indianapolis with a complete annual and two new engines, and it hasn't so much as made a funny noise.

 

[Lrjtcaptain]

Its just a bragging sticker that the airplane had the TPE331-10's

It was an upgrade for 690A,B,C, and D to use the Tpe331-10T engine.

higher, fuel efficient flight levels, full rated power to 16,000ft as apposed to factory engines giving it to you to 6,000ft.

Basically fly higher, faster, with about 10% less fuel and save almost $200,000 on scheduled mx cost.

Makes the plane valuable, reduced hot section costs



Factory 690's came with -5's
TPE331-5's (TPE331-10T) ISA, 9000lb., 96%, 20,000ft., 310KTAS
Thermodynamic SHSP 840min (1000 min)
Flat rated torgue to 6,000ft (16,000ft)
Cruise speed: 276kts (310kts)

 

[Jmmccutc]

In other words the Commander cannot carry what the King Air carries nor does it have the room. The commander does outperform the King Air in other areas, however only when it is not down in the shop for maintenance.

yeah ours was down constantly...thanks for the answers, you guys just afirmed what i already thought...

 

[wrigley23]

Why are Garrett engines so freakin loud when at idle? It seems when on the T/O roll they quiet down a bit. Anyone who has been around a Turbo Commander/MU-2/or B100 on the ramp knows that your teeth will rattle. Does it have something to do with the direct drive? Just curious.

 

[Lrjtcaptain]

becasue they are direct drive engines. The rpm on the props is really high!


the pt6 is geared down more, hence slower rpms, less noise, more spool time etc..

the tpe gives you less spool so it acts almost like a piston when it comes to power settings yet turbine power of course!

 

[EatSleepFly]

Why are Garrett engines so freakin loud when at idle? It seems when on the T/O roll they quiet down a bit. Anyone who has been around a Turbo Commander/MU-2/or B100 on the ramp knows that your teeth will rattle. Does it have something to do with the direct drive? Just curious.

Yes.

Can't speak for the Commander, but in the B100 at ground idle with the engine speed levers full low, the engine speed is still 65%. Ground idle with ESL's full high, engine speed is 96.5% and then its REALLY noisy.

At max. power the engine shaft is turning at 41,730 RPM while the prop is 2000 RPM. If you spin the prop one full revolution, and look at the first stage compressor, it will spin around almost 21 times for each complete turn of the prop. Thats a lot of reduction gearing!

One day up in Michigan (Flint, I think), we were getting ready to go out, and the FBO manager comes up and asks if we can keep our time in front of the FBO to a minimum...

 

[johnpeace]

At max. power the engine shaft is turning at 41,730 RPM while the prop is 2000 RPM. If you spin the prop one full revolution, and look at the first stage compressor, it will spin around almost 21 times for each complete turn of the prop. Thats a lot of reduction gearing!

I thought the King Airs (and Caravans) used a fluid coupling from the turbine to the prop.

Does the fluid coupler spin at 1:1 with the turbine shaft, and then prop RPM is controlled through gear reduction and a RPM governor?

How does it work?

 

[EatSleepFly]

I thought the King Airs (and Caravans) used a fluid coupling from the turbine to the prop.

Does the fluid coupler spin at 1:1 with the turbine shaft, and then prop RPM is controlled through gear reduction and a RPM governor?

How does it work?

The B100 has Garrett engines, which are direct drive and quite a bit different than those found the other King Airs or a Caravan. The engine speed is very high, and the prop speed is relatively low. The RPM reduction (shaft to prop) is acheived through a reduction gearbox. You set power with the power levers. You set prop/engine speed with engine speed levers. The speed levers set operating speed of the prop governor. The governor changes prop blade angles as necessary to maintain that selected engine/prop speed. Clear as mud?

 

[johnpeace]

Clear as mud?

Yeah, thanks..I am really fascinated about this stuff and love learning more.

So the PT-6 powered ones are fluid coupled?

 

[avbug]

These are not "fluid coupled" but air free turbine engines. What you have is a turbine engine blowing exhaust gasses on a turbine that's connected to the propeller. The propeller isn't driven mechanically by the engine, but by exhaust gasses being expelled from the engine. As exhaust gasses exit the combustion chamber, they turn the engine power turbine, which turns the compressor wheel.

The exhaust gasses are then done doing work for the engine, and blow across the propeller turbine wheel, which turns the propeller through a reduction gearing.

In theory (and theory only) you can hold onto the propeller of a PT6 powered engine and start the engine; the engine isn't driving the propeller. The only force acting to turn the propeller is exhaust gas from the engine. The problem with that theory is the amount of torque imparted to the propeller turbine wheel by those gasses; you'll get tossed and hurt if you try to hold onto the propeller.

The commander is a hot rod compared to the king air, but is more of a maintenance pig, and the tail doesn't tend to fall off of king airs. The same can't be said for the king air.

 

[johnpeace]

These are not "fluid coupled" but air free turbine engines. What you have is a turbine engine blowing exhaust gasses on a turbine that's connected to the propeller. The propeller isn't driven mechanically by the engine, but by exhaust gasses being expelled from the engine. As exhaust gasses exit the combustion chamber, they turn the engine power turbine, which turns the compressor wheel.

So, given that understanding of 'air free turbine engines' why aren't they 'fluid coupled'?

I mean, the coupling between the turbine and the prop is a fluid (air), so...doesn't that make it 'fluid coupled'.

Why is it wrong to call it that?

 

[avbug]

You call it whatever you like, John. It probably won't hurt a thing.

 

[johnpeace]

You call it whatever you like, John. It probably won't hurt a thing.

lol, OK...so I am taking it that the more technically correct and universally accepted name is 'air free turbine'.

thanks.

 

[EatSleepFly]

Free Air Turbine, actually.

I was a bit confused by the term, "fluid coupled" myself....

 

[avbug]

It's definitely not air free...unless it's being operated in a vacum...

True fluid coupling would be reminiscent of the power recovery turbine feature of a turbocompound R-3350 engine. While the atmosphere is certainly fluid, and is a gasseous fluid, no particular coupling or coupling effect exists in the PT6 or any other free turbine engine. The degree of "coupling" is dependent upon airspeed, power setting or torque setting, scheduled blade angle, etc. propeller movement and action is independent of engine movement or action. While an increase in power will impart an increase in torque by increasing the force of exhaust gasses acting on the propeller turbine, because of variances possible to callit a coupling would be incorrect. The engine is not coupled, hence the terminology "free turbine."