Author Topic: More on Engine (Throttle Adjustment) sounds (Read 705 times)

CurtissP-6EHawk · « **on:** February 17, 2004, 05:09:06 PM »

Well, I had to sit back and think about it.

Cessna 180J:

When I increase the throttle, volume increases when rpm increases as well as sound tone changes resulting from the prop pitch changes. After rotation, MP is reduced by the throttle thus changing the tone and volume slightly. Volume should remain about the same since rpm stays about same. Then the prop speed (rpm) (power) is reduced using the prop lever (knob) thus changing tone and volume.

I think what is missing in beta is the slight change in tone when increasing/decreasing MP. IN beta, the volume of the tone stays constant. An abrupt change on the MP will cause the props to over rev allowing for a more dramatic change in "noses". Can anyone explain it better?

However, The "bug" I did find was on downwind leg for landing. There I made my "before landing check" and later discovered that when I increased rpm (back to full-in), the thottle then will not reduce "power" "rpm" when the throttle is fully closed. Thus causeing me to approach to fast, go around and find the problem.
However, If I did not mess with the rpm to begin with, I had no problems and did notice a sound change below a certain rpm when the engine slowed down to idle. Also, this sound was after landing.

CurtissP-6EHawk · « **Reply #1 on:** February 17, 2004, 05:30:18 PM »

1. On runway, full power...note sound changes as MP and RPM increase and when the sounds change in ref. with the MP indications.

2. Above a certain speed, the RPM will not drop below a certain speed. Example:
A. At idle the MP stays at 800 rpm
B. At 25 mph the MP stays at 1,100, rpms
C. At 50 mph the MP stays at 1,500 rpm
and will not reduce untill airspeed slows down.
Pay attention to the volume and tones at these settings!

Now, once airborn I did find some bugs.

Ruduce power for cruise flight, Max Cruise in P-51D is 38 MP and 2,400 rpm. reduction rpm using the num pad (+ -) keys. Then advance and retard the throttle..note the only thing that moves is MP. Then the sound is a constant tone but an increase/decrease in volume. This itself is a sound
bug!

Then close the throttle. Note the RPM stays the same...this is a bug as well. Even when RPM is set to a given rpm, closing the throttle will also reduce RPM. Now, when you do this, you will loose airspeed, so we a have a two-fold bug!
The program sees a decrease in power, thus the decrease in airspeed but it does not change the RPM needle nor engine sound only the volume!

BTW, look at the right side cockpit data plate for some power settings.

hitech · « **Reply #2 on:** February 17, 2004, 06:28:18 PM »

Ahh curtis does a 180j have a constant speed prop?

HiTech

CurtissP-6EHawk · « **Reply #3 on:** February 17, 2004, 06:42:13 PM »

Power settings are beginning to look wierd.

Sitting on runway engine running:
Increase to full throttle; should the RPM max out at 3,000 before MP reaches static? RPM reaches 3,000 when MP increases to only 20". Thats like 10% of foward throttle movement. Thats a big engine, I am not familur with settings.

CurtissP-6EHawk · « **Reply #4 on:** February 18, 2004, 12:14:07 AM »

Ahh curtis does a 180j have a constant speed prop?

yes, it has the McCauley constant speed propeller, Hub 2A34C66, Blades 90AT-8