Few questions on the Beechcraft...

[LZ-WIL]

Hello everyone,

As writing this post, I am wondering if anyone else has noticed this, while operating the Bonanza;

1) While on the ground and leaning the mixture, it rises and stops, does not drop, when the mixture gets too lean like in the Cessnas in example.
I wonder is this normal for the Beechcraft models?

2) When I apply throttle for take off, the RPM reaches the red line at half or 2/3 of the throttle way ( just above 20mp and prop is full in)? I am afraid to apply full power like in the 172 or the Cherokee.

The third one is more like of a curiosity one: why, are there two altimeters on this airplane?

Cheerz,
Vladimir

[Oracle427]

1) What rises and stops, does not drop?

2) This is a constant speed prop. The RPM will be maintained at the set value provided the engine is generating enough power to turn t
the prop at an RPM that requires the prop governor to increase pitch. You must use the FF, MAP and RPM together to identify how much power you are generating.

3) I believe there is another thread about this. One altimeter is an encoding unit that provides data to the other avionics in the aircraft.

[LZ-WIL]

1) What rises and stops, does not drop?

2) This is a constant speed prop. The RPM will be maintained at the set value provided the engine is generating enough power to turn t
the prop at an RPM that requires the prop governor to increase pitch. You must use the FF, MAP and RPM together to identify how much power you are generating.

3) I believe there is another thread about this. One altimeter is an encoding unit that provides data to the other avionics in the aircraft.

Hi Oracle427,

1) I apologize for this - the RPM rises when you lean. I was excited in writing and forgot to mention it. Thank you for your reply.

2) I understand it is a constant speed prop airplane, I guess I must be careful not to overspeed the prop. What is FF by any chance?

3) Though so, could not find it on the forums. Thanks!

Cheerz,
Vladimir

[Oracle427]

You can't overspeed a constant speed prop unless the governor has malfunctioned or you dive so fast that the governor runs out of adjustment range to control the RPM. Under normal circumstances, you do not need to be concerned with this.

FF = Fuel flow

The power the engine3 is producing is a function of fuel flow, MAP and RPM. You need to observe all three to understand what the engine is producing. The MAP tells you how much oxygen is going into the engine, the FF tells you the amount of fuel and the commanded RPM dictates how much work the engine is performing on the air. Looking at any one of those in isolation from the others doesn't give you enough information. The cruise performance charts provide all these pieces of data to help you determine what settings to use. You must consider the density altitude as that has a dramatic effect the power produced by the engine, and this is part of the information on the cruise performance charts.

The engine is an air pump and the MAP tells you how much air it is sucking in. The thing is that even if the engine is producing no power, it will still suck air in if a prop is windmilling. An engine producing little power will still turn the prop at its rated RPM. Generally, the governor runs out of pitch when the MAP drops to around 13" IIRC if in a shallow descent. The FF tells you how much fuel it is taking in but NOT how much is being converted to mechanical energy. That is because too much or too little fuel will result in poor or no combustion.

Takeoff is a special time where excess fuel must be fed into the combustion chamber to prevent detonation. The engine needs to be run very rich to prevent the fuel from spontaneously combusting and causing catastrophic damage when at high power settings generally in excess of 75% for these types.

You can't lean by RPM on a constant speed prop as the governor will adjust the prop angle to maintain RPM. You will need to use EGT to lean. When leaning on the ground, lean until the point that the engine starts to run rough when at 1200 RPM and then enrichen just enough to run smoothly. Don't forget to go full rich prior to takeoff when below 5000 feet. Above 5000 feet you should lean to the same EGT observed just after takeoff at sea level for max power and proper cooling/anti-detonation margin. The reason you need to lean at 1200 RPM is because that is sufficiently past the point when the throttle position closes off the idle circuit.

[Nick - A2A]

Hello Vladimir,

3) I believe there is another thread about this. One altimeter is an encoding unit that provides data to the other avionics in the aircraft.

Yes, as Oracle says the KEA is an encoding altimeter which is electrically powered. This means it requires a regular barometric altimeter as a backup. More info here.

Thanks,
Nick

[LZ-WIL]

Hi,

I would like to thank you for this detailed and interesting explanation, I have remembered and learned stuff. I must say I feel kind of sheepish, especially for the constant speed prop. Of course the governor take care of the propeller like you said unless it's damaged or the aircraft is an excessive dive.
I will focus more on the EGT, when leaning the constant speed GA airplanes. Did not know the reason why lean at 1200, that was something new.

Thank you once more for the answers and your time!

Cheerz,
Vladimir

[ClipperLuna]

About the overspeed thing, I'm guessing you, like me, noticed the engine speed transiently increases past redline on takeoff (unless you are absurdly slow pushing the throttle all the way in) and were worried about it? I think these engines can safely "overrev" a little bit for brief periods of time. I saw a figure of no more than 10% for no more than 3 seconds for Lycomings (forgot which one). I tried to look this up for the Continental 520 but I couldn't find anything about it. Anyone know?

[LZ-WIL]

Hello Vladimir,

3) I believe there is another thread about this. One altimeter is an encoding unit that provides data to the other avionics in the aircraft.

Yes, as Oracle says the KEA is an encoding altimeter which is electrically powered. This means it requires a regular barometric altimeter as a backup. More info here.

Thanks,
Nick

Interesting...

Thanks Nick! Currently reading for KEA 346...

Cheerz,
Vladi

[Oracle427]

There must be a published limit in some SB somewhere. The prop and engine have their own separate limitations, depending on the make and model. 10% isn't very much and it is almost a certainty that an engine that hasn't warmed up very much after sitting may not warm up the oil in that prop hub to get good operation from the governor. You can see a significant overspeed if you forgot to cycle the prop during runup and then apply the throttle quickly at takeoff. Not good!

[Piper_EEWL]

Regarding the constant speed propeller on the Bonanza I’ve definetly noticed one big difference to the Cessna 182T. When you hold the plane with the brakes and apply full throttle the Cessna with the IO-540 will only bearly reach the red line rpm. Only when the plane accelerates will the governor have to reduce the rpm. This is also what my real life experience with the C182T reflects.

With the Bonanza and the IO-550 as Vladimir already pointed out red line rpm will be reached at way lower throttle settings. Subsequently one has to slowly advance the throttle to not overspeed the engine too much since the governor takes some time to react. Even after cycling the prop in the runup. I usually manage 100rpm above the red line. Is this normal behavior for the Continental engine with this propeller? And when yes what’s the purpose?

Unfortunately I don’t have a Bonanza at my disposal to verify this

[ClipperLuna]

That's been my experience as well. If i'm doing a rolling takeoff, the engine goes about 100 rpm past redline even after I cycled the prop a few times during runup and I advance the throttle slowly. Last night I made sure I didn't put the throttle all the way in until I reached a count of 11-12 and it still did it. Could it be deliberately set like that to give us an extra shot of power?

BTW, if you haven't flown this plane at night yet you're seriously missing out. The colored lights cockpit are an absolute visual feast.

[Oracle427]

Everything in good condition in the maintenance hangar?

IRL, every plane I fly with a constant speed prop has slightly different max RPMs. You just learn the specific machine and then tweak the prop control in the cockpit to respect the limit.

Anything beyond 50 RPM is definitely going into the shop for adjustment before I fly it again.

[ClipperLuna]

Yup, my A&P guy said everything's good.

[Piper_EEWL]

In my hangar everything is fine too. It just feels like the governor takes it sweet time to reduce the rpm. Once the power is set to full the rpm returns to the red line and stays there until I reduce it. It’s just weird to me that the max rpm is reached at 50% (or so) throttle.

[LZ-WIL]

Hi guys,

This is exactly, what I had in mind when I asked the over speed question. May be this is how the Beechcraft Bonanza governor works and we are not used to it yet. It is an A2A aircraft after all with the latest generation of Accu-Sim.

Cheerz,
Vladimir