This is good general info, thanks Cary! Wish this would have been posted a year ago when I was teaching myself how to fly with a constant speed prop.

Gawrsh, you shoulda asked!

Cary

Kind of related. A good article on running "over square".

http://www.avweb.com/news/airman/184483-1.html?redirected=1

Cory,

I run mine pretty close as you describe, although I do not run LOP, stock injectors. I cruise at 23/ 23 until mp drops due to altitude. I nearly always burn 12 gph. What are your speeds at an rpm of 22? I have found the 205 charts are very close to actual. Guess I will go out today and run at 22 to see what mine does.

The neighbor and his wife are looking at it on Saturday, will let you know what happens. Getting a bit melancholy!

Stan

Not being a CFI, nor a mechanic I figured I'd leave this thread to those that are (specially the second one). A thought occurred to me though.... most of the advice here (good stuff BTW) encompasses what would already be in the POH (assuming stock config). Is it just me or does anyone prefer to run their prop a little on the fast side if they find themselves loping along on the floor of a canyon at slower than 'cruise' speeds? I just hate the notion of needing to pour the coals to it and forgetting that the prop was pulled wayyy back.

Another odd thing I do, is dial my prop back in the decent as I dial the throttle back. My philosophies here are this;
A) Running an entire circuit with the prop set at a low rpm is much less noisier than a prop turning at full tilt. While I love airplane noise, I realize we are probably the minority, consequently I think it behooves us to be good neighbors.
B) Lowering the RPM builds manifold pressure (already building in the decent) manifold pressure builds heat (usually bad)
Heat in the decent is our friend, because it already wants to cool tooo quickly...
C) I hate using the prop to drive the engine... no jake brake on my planes...
D) when cruising around at low speeds elsewhere, I tend to run a low RPM as well as low manifold, and since we are essentially in a low cruise speed in the pattern, why would I want to run the entire circuit with the rpm set the same as a highspeed cruise, and the throttle pulled back.
Lastly, once the prop has fallen off the governor, the prop is going to go full fwd anyhow, (again, not using the prop to drive the engine) so why not take advantage of the lower fuel burn in the decent caused by the lower rpm?.

None of this was gained during conventional training, so it may in fact be a poor practice, but it has worked for me. Once while ferrying an airplane with a good friend / ATP I was chastised for this practice, although he couldn't explain to me why it was a bad habit... just that it shouldn't be done. He then proceeded to roll the nose over let the steam build and literally shove the prop fwd to slow the airplane down once on short final. Although I use the prop to help manage speed on turbines I cringe at treating recips like that...

Any thoughts?

Rob, When I'm in a plane that goes fast?? (Tbonanza, T210, Tbaron) (10-20,000') when on decent I do pretty much the same, a long long ways out I roll back a few rpm's towards the bottom of the green arc,(Cool it down before heading down) then start down, rolling the MP back also, trading altitude and gravity for gas and speed. Keep it running hard enough to still make some heat! This sometime is 20-30-40 miles out.
Should be a continual slow down to and once in the pattern to flare and landing, not sure why you need to wind up the prop and make noise and burn gas trying to land?
Seems to work lower in most bugsmashers also.
Again worth it's weight in BS

Rob and M6RV6,

Thanks for the discussion on descent technique. I've struggled to manage this phase as much as I've struggled to get good instruction for my airplane. Last instructor wanted me to just nose it over and would have allowed us to approach Vne. I'll go back to the drawing board, starting down on MP even earlier. Thanks for the help.

Cary wrote:

This is good general info, thanks Cary! Wish this would have been posted a year ago when I was teaching myself how to fly with a constant speed prop.

Gawrsh, you shoulda asked!

I thought about it but figured I'd just get the standard "go find and instructor" replies.

Lots of interesting info in this thread.

Rob wrote:Not being a CFI, nor a mechanic I figured I'd leave this thread to those that are (specially the second one). A thought occurred to me though.... most of the advice here (good stuff BTW) encompasses what would already be in the POH (assuming stock config). Is it just me or does anyone prefer to run their prop a little on the fast side if they find themselves loping along on the floor of a canyon at slower than 'cruise' speeds? I just hate the notion of needing to pour the coals to it and forgetting that the prop was pulled wayyy back.

Another odd thing I do, is dial my prop back in the decent as I dial the throttle back. My philosophies here are this;
A) Running an entire circuit with the prop set at a low rpm is much less noisier than a prop turning at full tilt. While I love airplane noise, I realize we are probably the minority, consequently I think it behooves us to be good neighbors.
B) Lowering the RPM builds manifold pressure (already building in the decent) manifold pressure builds heat (usually bad)
Heat in the decent is our friend, because it already wants to cool tooo quickly...
C) I hate using the prop to drive the engine... no jake brake on my planes...
D) when cruising around at low speeds elsewhere, I tend to run a low RPM as well as low manifold, and since we are essentially in a low cruise speed in the pattern, why would I want to run the entire circuit with the rpm set the same as a highspeed cruise, and the throttle pulled back.
Lastly, once the prop has fallen off the governor, the prop is going to go full fwd anyhow, (again, not using the prop to drive the engine) so why not take advantage of the lower fuel burn in the decent caused by the lower rpm?.

None of this was gained during conventional training, so it may in fact be a poor practice, but it has worked for me. Once while ferrying an airplane with a good friend / ATP I was chastised for this practice, although he couldn't explain to me why it was a bad habit... just that it shouldn't be done. He then proceeded to roll the nose over let the steam build and literally shove the prop fwd to slow the airplane down once on short final. Although I use the prop to help manage speed on turbines I cringe at treating recips like that...

Any thoughts?

This all sounds like what John Deakin suggests. Since I'm already at the bottom of the green arc when I start the decent, the reduction step is already done. While the prop forward can help with descent, a little better descent planning would negate the need for it. Higher RPM results in higher fuel flow which also results in more cooling to the engine (not what you want). I'd never run it to Vne, especially if the air wasn't absolutely smooth. Not only can an unexpected bump cause you to overspeed and/or put unneeded stress on the frame, but you're also pouring a ton of cooling air over the engine, which isn't helping your cause.

Once in the pattern, I prefer bringing the prop to high rpm once it's off the governor as opposed to doing the monkey grab for it and the throttle during a go-around. Mixture also comes to a ROP/max power setting at this point too for the same reason.

I think that those people that chastise you for it but can't explain why it is bad are those that probably haven't owned their own plane and given any thought as to the why of how they operate an engine and have just gone along with what they were taught. Unfortunately, there is a lot of bad info that is handed down from CFI to student who eventually also hands it down. I myself was guilty of this. After buying our 205 last year, I've put a lot of effort into learning the why of it all (still learning) and how I operate an aircraft engine has changed considerably.

sburg58 wrote:Cory,

I run mine pretty close as you describe, although I do not run LOP, stock injectors. I cruise at 23/ 23 until mp drops due to altitude. I nearly always burn 12 gph. What are your speeds at an rpm of 22? I have found the 205 charts are very close to actual. Guess I will go out today and run at 22 to see what mine does.

The neighbor and his wife are looking at it on Saturday, will let you know what happens. Getting a bit melancholy!

Stan

Hey Stan.

At 22"/2200RPM, I see 150 mph TAS ROP and 130 mph TAS LOP. Fuel burn is between 12-13 gph 100-120 degrees ROP (can't tell you for sure because I never run it there. I just know from the Gami lean tests that they all peak around 11.7 gph) and as low as 9.3 gph LOP. As mentioned above, I run it between 10.0-10.3 gph to keep my #5 CHT a little warmer.

Good luck! Let me know how it goes.

Cory