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Forum: Tech Log
18th Jun 2012, 19:01
Replies: 156
Views: 51,143
Posted By barit1

keith williams: Well done! :ok:

keith williams:

Well done! :ok:
Forum: Tech Log
17th Apr 2012, 03:14
Replies: 156
Views: 51,143
Posted By barit1

oggers, please re-read post #144. I made it...

oggers, please re-read post #144. I made it pretty clear that there are two kinds of efficiency, one for static thrust, and one for propulsive efficiency. Please - when you refer to "efficiency" -...
Forum: Tech Log
16th Apr 2012, 03:09
Replies: 156
Views: 51,143
Posted By barit1

A Squared: Very good breakdown of the SHP...

A Squared:

Very good breakdown of the SHP problem. I've been stung by that "factor of 12" issue before - it's egg-on-your-face big time!

I will, however, point out 1 or 2 little items: Torque...
Forum: Tech Log
14th Apr 2012, 02:24
Replies: 156
Views: 51,143
Posted By barit1

oggers: Exactly, because it's a...

oggers:



Exactly, because it's a different kind of efficiency - i.e. a measure of how much STATIC thrust can be had, compared to some theoretical "perfect" static thrust. That's altogether...
Forum: Tech Log
13th Apr 2012, 12:48
Replies: 156
Views: 51,143
Posted By barit1

The answer is found in the question "how much...

The answer is found in the question "how much aerodynamic drag (due to vehicle speed) is there?"

If there's no velocity, and no drag, then there's no work being done to move the plane. And thus...
Forum: Tech Log
12th Apr 2012, 12:59
Replies: 156
Views: 51,143
Posted By barit1

oggers: Power AVAILABLE (not power...

oggers:

Power AVAILABLE (not power delivered) is very nicely defined by KW:


And I will add: The wasted propwash power is dissipated in heat (friction between air molecules in the turbulent...
Forum: Tech Log
12th Apr 2012, 01:52
Replies: 156
Views: 51,143
Posted By barit1

To spell it out, using a 10000# thrust engine for...

To spell it out, using a 10000# thrust engine for example:

At zero TAS, THP = 0

At 375 MPH (i.e. 550 fps) TAS, THP = 10000

At 750 MPH (i.e. 1100 fps) TAS, THP = 20000

...and so on. As you...
Forum: Tech Log
11th Apr 2012, 12:23
Replies: 156
Views: 51,143
Posted By barit1

Nope. THP is the power DELIVERED TO THE VEHICLE. ...

Nope. THP is the power DELIVERED TO THE VEHICLE.



See above.
Forum: Tech Log
7th Apr 2012, 20:13
Replies: 156
Views: 51,143
Posted By barit1

The conditions I propose: o Parked, brakes...

The conditions I propose:

o Parked, brakes locked (zero GS)

o Zero wind (thus zero IAS)

The questions: How much induced AND profile drag?

and...
Forum: Tech Log
7th Apr 2012, 16:05
Replies: 156
Views: 51,143
Posted By barit1

True, but I believe the unstated assumption here...

True, but I believe the unstated assumption here is a steady-state (unaccelerated) vehicle.
Forum: Tech Log
7th Apr 2012, 02:34
Replies: 156
Views: 51,143
Posted By barit1

A few thoughts: At zero airspeed, how much...

A few thoughts:

At zero airspeed, how much induced drag does the aeroplane see? How much profile drag?

How much horsepower does it then take to (ahem) "move" it at zero airspeed?

There may...
Forum: Tech Log
31st Mar 2012, 14:37
Replies: 156
Views: 51,143
Posted By barit1

Old Fella: Hmmm. Since the aircraft...

Old Fella:

Hmmm. Since the aircraft performance is dependent on the props being driven at some torque rating, I must ask how you determine your performance-limited TOGW??
Forum: Tech Log
31st Mar 2012, 14:32
Replies: 156
Views: 51,143
Posted By barit1

And so when a PW4000 runs up to max on a...

And so when a PW4000 runs up to max on a terrestrial test bed, it is actually creating ~70,000 thrust HP? Is that what we surmise? :rolleyes:
Forum: Tech Log
28th Mar 2012, 20:59
Replies: 156
Views: 51,143
Posted By barit1

Permit me, please, another thought problem: ...

Permit me, please, another thought problem:

A C-130 with a failed #4 starter lines up behind another C-130 for a "buddy start". The "mother ship" runs up a couple engines while standing on the...
Forum: Tech Log
27th Mar 2012, 16:01
Replies: 156
Views: 51,143
Posted By barit1

IF tcyandy is talking about a direct-drive,...

IF tcyandy is talking about a direct-drive, ungeared engine, then there is ONLY ONE TORQUE to consider. It is the torque the engine crankshaft delivers to the prop.

You may call it prop torque, or...
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