During cruise Bonanza flies with pitch down

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charliecharlie
Airman
Posts: 11
Joined: 17 Sep 2018, 09:09

During cruise Bonanza flies with pitch down

Post by charliecharlie »

Hello,

During each flight with the Bo, when levelled off at required altitude, she flies with a slight pitch down, beetween -1° and -2°, sometimes -3°

During this flight (see picture below) I was alone pilot and the weights as follow

Pilot 170 lbs
Baggage 89 lbs
Total fuel 383 lbs (tip tanks empty)
TW 2991 lbs
weather : temp and QNH on ground were STD with default P3D4 wx (no AS).
The pitch trim wheel ( aircraft under AP control) was around -16/-17 (mouse tooltip values)
Adding 3 passagers decreased the pitch value to -1° but still negative.

Image

That seems a little bit strange to me. Is that a normal behavior of the Bo, V tail consequence ?

Thanks for any enlightenment

Georges

charliecharlie
Airman
Posts: 11
Joined: 17 Sep 2018, 09:09

Re: During cruise Bonanza flies with pitch down

Post by charliecharlie »

Sorry I didn't manage to insert my dropbox image, I probably missed something with the forums tags.

Hope my description speaks by itself.

Best regards

Georges

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DC3
Technical Sergeant
Posts: 695
Joined: 03 Jul 2012, 00:46
Location: California

Re: During cruise Bonanza flies with pitch down

Post by DC3 »

What is your RPM and Manifold Pressure set at? What is your IAS and Altitude?

charliecharlie
Airman
Posts: 11
Joined: 17 Sep 2018, 09:09

Re: During cruise Bonanza flies with pitch down

Post by charliecharlie »

Thank you DC3 :)

IAS 175 kts
MP 21,5
RPM 2300
Alt 8000ft
OAT 0°C
Flaps up ! (just check my picture, in case of.....)
Pilot alone

https://www.dropbox.com/s/qc4g8l6t3tu9y ... 9.jpg?dl=0

best regards

Georges

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Nick - A2A
A2A Captain
Posts: 13728
Joined: 06 Jun 2014, 13:06
Location: UK

Re: During cruise Bonanza flies with pitch down

Post by Nick - A2A »

Georges,

I'm not sure this is anything to worry about. The Bonanza is a very clean aeroplane and in your example, you're flying at well under gross weight. I'll mention it to Scott though, nonetheless.

Thanks,
Nick

P.S. I've edited your first post to show the Dropbox image. It's just a case of changing the "www" part of the URL to "dl". More info on this kind of stuff here.

charliecharlie
Airman
Posts: 11
Joined: 17 Sep 2018, 09:09

Re: During cruise Bonanza flies with pitch down

Post by charliecharlie »

Thank you so much Nick.

Regarding the weight, if I add Pax and luggage accordingly, the pitch increases but is still negative, around -1°

In fact nothing really annoying, the pitch down is not obvious to see and the flight dynamic feeling is awesome.
Until I pass the mouse cursor over the ADI, I didn't notice anything :wink: , and I thought the ADI attitude was a POV parallax effect.

Thanks to investigate about this one, curious to know if it's an issue or not.

P.S. I take note about the dropbox tip for the future.

Best regards

Georges

EnDSchultz
Technical Sergeant
Posts: 504
Joined: 24 Feb 2014, 20:05

Re: During cruise Bonanza flies with pitch down

Post by EnDSchultz »

I noticed this as well. I don't think it's terribly unusual for high performance airplanes to cruise with a slight nose-down attitude. Aircraft are usually built with a positive "angle of incidence" - this is the angle between the chord line of the wing and the nose of the aircraft. This means that with the nose perfectly pointed at the horizon, the wing is still at a positive angle and therefore has a positive angle of attack and is producing lift. Since high performance airplanes tend to cruise at a rather high airspeed, they don't need all that extra AoA in order to produce enough lift, and therefore often cruise at a slight nose-down attitude. This tendency is very evident in the Beech Baron sim at my flight school, which will stabilize at several degrees nose down at high cruise.

Jarek
Senior Airman
Posts: 180
Joined: 31 Aug 2018, 14:59

Re: During cruise Bonanza flies with pitch down

Post by Jarek »

AoI is +4 at root and decreases to +1 at tip, so it doesn't look bad at speeds close to maximum.

charliecharlie
Airman
Posts: 11
Joined: 17 Sep 2018, 09:09

Re: During cruise Bonanza flies with pitch down

Post by charliecharlie »

Yes you're absolutly right, AOA and pitch angle are not the same.
I presume the Bonnanza wing profile and the angle beetween le chord line and the fuselage axis are built in a way to allow
great performance speed with minimum drag.
That could explain the slight pitch down in cruise, AOA being still positive of course !
What you said makes sense, thanks for your comments EnDSchultz !

Georges

charliecharlie
Airman
Posts: 11
Joined: 17 Sep 2018, 09:09

Re: During cruise Bonanza flies with pitch down

Post by charliecharlie »

Thank you Jarek, this makes things more clear now

Georges

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