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Forum: Tech Log
24th Jun 2012, 12:40
Replies: 156
Views: 51,036
Posted By keith williams

If you feel the need to hang on to that figleaf...

If you feel the need to hang on to that figleaf ogger then do so.

Life's too short for me to waste any more time conversing with you oggers.

I'm sure most of the people who have followed...
Forum: Tech Log
22nd Jun 2012, 12:27
Replies: 156
Views: 51,036
Posted By keith williams

I thought you might wish to deny one or more of...

I thought you might wish to deny one or more of your errors, so I did a search.

1. Propellers continue produce THP when the aircraft velocity is zero.


Page 1 post 8 “Not that myth again....
Forum: Tech Log
21st Jun 2012, 12:33
Replies: 156
Views: 51,036
Posted By keith williams

As the collective is lowered the aircraft starts...

As the collective is lowered the aircraft starts to descend and the induced velocity and the induced power both fall to zero. As the aircraft accelerates downwards the direction of the total reaction...
Forum: Tech Log
18th Jun 2012, 13:29
Replies: 156
Views: 51,036
Posted By keith williams

The author of the essay to which you have...

The author of the essay to which you have repeatedly referred did not actually state that the equation is invalid as speed approaches zero. What he actually said was:

While working on a project...
Forum: Tech Log
17th Apr 2012, 16:57
Replies: 156
Views: 51,036
Posted By keith williams

Rudderrudderrat, If Oggers had wanted to...

Rudderrudderrat,

If Oggers had wanted to accept the fact that propeller efficiency is zero when forward speed is zero, he just needed to read the Essay to which he referred on page 4 of this...
Forum: Tech Log
17th Apr 2012, 10:33
Replies: 156
Views: 51,036
Posted By keith williams

OK lets’ look at your scenario and see if it...

OK lets’ look at your scenario and see if it really proves your point.

To simplify the situation and to avoid any ambiguities we will assume the following:


1. The aircraft is initially in...
Forum: Tech Log
16th Apr 2012, 22:09
Replies: 156
Views: 51,036
Posted By keith williams

Oggers, It's a bit too late for me to reply...

Oggers,

It's a bit too late for me to reply to your post tonight.

For the moment, would you please state what you believe to be the correct equation for propeller efficiency.
Forum: Tech Log
14th Apr 2012, 08:35
Replies: 156
Views: 51,036
Posted By keith williams

We can calculate the efficiency of any process...

We can calculate the efficiency of any process that we choose to look at.

How efficiently do I digest my food? (not very efficiently, judging by how much I eat and how little exercise I do)
...
Forum: Tech Log
13th Apr 2012, 20:15
Replies: 156
Views: 51,036
Posted By keith williams

Happy to oblige. In the paragraph...

Happy to oblige.



In the paragraph above you are using the thrust multiplied by the AICRAFT VELOCITY to get the THP. That is entirely correct
Forum: Tech Log
13th Apr 2012, 15:44
Replies: 156
Views: 51,036
Posted By keith williams

Oggers, The first point that we should...

Oggers,

The first point that we should note is that the author of that paper is not a universal authority on these matters. He has his point of view, but this cannot be used as an argument for...
Forum: Tech Log
13th Apr 2012, 14:02
Replies: 156
Views: 51,036
Posted By keith williams

Oggers, some of your posts appear to indicate...

Oggers, some of your posts appear to indicate that you think that if thrust is not zero then propeller efficiency cannot be zero. If you do believe this, then you are wrong (once again).

If you...
Forum: Tech Log
12th Apr 2012, 18:57
Replies: 156
Views: 51,036
Posted By keith williams

OK, then I will refine the statement a little....

OK, then I will refine the statement a little. THP is the power that we use to carry out the work of pushing the aircraft forward against the drag at our chosen aircraft speed.The second type is the...
Forum: Tech Log
12th Apr 2012, 14:39
Replies: 156
Views: 51,036
Posted By keith williams

Oggers you really must try reading instead of...

Oggers you really must try reading instead of just writing!

The POWER AVAILABLE from the PROPELLER is turned into two different types of power.

The first type is THP which is used to push the...
Forum: Tech Log
12th Apr 2012, 12:27
Replies: 156
Views: 51,036
Posted By keith williams

Oggers, it was actually your second post in which...

Oggers, it was actually your second post in which you said the following:



But you were wrong, because you were confusing THP with the power that is being wasted in the propwash. You have...
Forum: Tech Log
12th Apr 2012, 10:48
Replies: 156
Views: 51,036
Posted By keith williams

Oggers you are overlooking the power that is...

Oggers you are overlooking the power that is being wasted in doing work on the propwash.

When the aircraft is stationary on the ground with engine running all of the propeller power output is...
Forum: Tech Log
5th Apr 2012, 15:26
Replies: 156
Views: 51,036
Posted By keith williams

Oggers, My only purpose in contributing to...

Oggers,

My only purpose in contributing to this thread was an attempt to assist blackhand to understand why his car was not producing any THP. I can assure you that it was not in any way meant...
Forum: Tech Log
3rd Apr 2012, 19:51
Replies: 156
Views: 51,036
Posted By keith williams

The book "The Jet Engine" by Rolls Royce gives...

The book "The Jet Engine" by Rolls Royce gives the following version of the equation for propulsive efficiency for a jet engine.

Propulsive Efficiency = (Work done on the aircraft) / (Work done...
Forum: Tech Log
27th Mar 2012, 13:51
Replies: 156
Views: 51,036
Posted By keith williams

tcyandy What are you studying that has made...

tcyandy

What are you studying that has made you ask this question?

If you are studying for the JAA/EASA ATPL then the answer they are looking for is.

Propeller torque is resisting the...
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