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  #21  
Old 09-20-2018, 04:09 PM
meyer228 meyer228 is offline
 
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Originally Posted by RV8JD View Post
With Van's redefining Vne in terms of TAS, my RV-8 with a YIO-360-M1B will exceed its Vne of 230 MPH TAS if I don't bring back the power in a descent. Van's (possibly conservative) redefinition of Vne in terms of a constant TAS value at all altitudes, limits the RV-8's downhill performance.


Sorry for the thread drift!
Yeah, that's kind of what I experienced. TAS VNE really easy to bust... No complaints. Just need to manage it...and descend earlier...
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  #22  
Old 09-21-2018, 12:21 AM
gasman gasman is offline
 
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Originally Posted by meyer228 View Post
Cool..

Okay follow up questions - Do you find yourself doing anything a little more cautiously? Making sure you don't shock cool? Make sure you've get the CHT's in the "green" before take off??

Also, from what I understand the failure mechanism (if there is one) isn't necessarily catastrophic engine failure but, separation of the head from the cylinder and subsequent partial loss of power. Right?

As you could likely guess, I have purchase a 9a with the ECI Group B cylinders/heads. < Correction - I have Group A >

Thanks for sharing your info...
Wrong..... it will still produce enough power to keep the aircraft in the air. BUT the aircraft will shake violently enough that you will want to get on the ground ASAP. You will need to reduce power to avoid tearing then motor from it's mounts.
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  #23  
Old 09-21-2018, 12:26 AM
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Ironflight Ironflight is offline
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Quote:
Originally Posted by RV8JD View Post
With Van's redefining Vne in terms of TAS, my RV-8 with a YIO-360-M1B will exceed its Vne of 230 MPH TAS if I don't bring back the power in a descent. Van's (possibly conservative) redefinition of Vne in terms of a constant TAS value at all altitudes, limits the RV-8's downhill performance.

Note where Redline is (in terms of MPH IAS) in the screenshots below, at much less than 75% power.

400 FPM descent at 9800':



600 FPM descent at 16,120':



Sorry for the thread drift!
Of course you have to observe all operating limits -but you descend at speed, throttling back just enough to observe Those limits, and get a nice fast ride downhill - you donít have to pull all the power off to where youíre worried about cooling in order to lose 10,000í in 60 miles....
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  #24  
Old 09-21-2018, 02:33 PM
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grubbat grubbat is offline
 
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Default Prop driving engine

Lycoming rep advised me to keep manifold pressure at 18" or above to prevent prop from driving engine. I used to think it was around 15" min but not so. Prop driving engine is not good. Constant speed prop really helps with the need to loose altitude while maintaining proper manifold pressure.
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  #25  
Old 09-21-2018, 07:04 PM
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erich weaver erich weaver is offline
 
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Originally Posted by grubbat View Post
Lycoming rep advised me to keep manifold pressure at 18" or above to prevent prop from driving engine. I used to think it was around 15" min but not so. Prop driving engine is not good.
Why not? Isn’t this essentially what happens every time we descend with a constant speed prop?

Erich
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