Power calculations

[DBRV10]

Your understanding of applying Mike Bush's Red Fin (because he graphed it that way) is quite sound. By the way Mike did the APS class many years ago….THREE TIMES. Not because he was dumb, because he was pationate in learning and applying it to his new (then) business.

To answer your question properly, you need to do the course!  That way the answer and all the factors around it will be understood. The quick answer I give you now will likely lead to hundreds of questions back and forth and this is not the place to be doing that.

Simply though it is all about keeping the internal cylinder pressure (ICP) and thetaPP in the right proportion and angle. This keeps things in the comfort zone of the design.

Can you play around inside the red box…..sure! Many folk have for decdes, but to get better life and less stress on the engine, it is best not too. You can achieve the same HP at varying stress levels and lower CHT by doing it right. You need to see the dyno runs in the class to appreciate what I am saying. But in simple terms I can run 85% power LOP and be cooler with less stress on the engine than running the exact same HP ROP, unless I run very ROP (not as per the POH).

I am not sure where you are but if getting to a class in Ada is too hard register for the online class. John Deakin will look after you! Give him my regards!

DB

PS: Have a look at this photo which is on the front cover of the course manual. Look closely at the two engines. Ask yourself which engine is working the hardest and which engine will run out of fuel the soonest. The pilots feet are flat on the floor and the skid ball is centred (no rudder trim to cheat being used), thus they are delivering the same HP! 

 

[Battson]

That is a good photo.
It takes a couple of seconds to see what's happening, but it does a really good job of illustrating the reasons for running your engine LOP.

I live in New Zealand, so it's unlikely I would ever be able to attend the course in Ada personally

 

[DBRV10]

OK I have an even better deal for you, and a LOT cheaper than doing a course in Ada.

Brisbane 27-29 March.

Air New Zealand (Worlds best Airline they say) is $500 return!

Will be a heap of fun and educational!

 

[vlittle]

I'm trying to understand how Dynon determines ROP/LOP status. It sounds like they track the intersect of a ROP power curve based on RPM, MAP, PA, OAT and a LOP power curve based on BSFC.

The BSFC curve requires engine horsepower to determine, so I guess this is the reason for setting this in the SkyView.

However, I assume it also requires an accurate fuel flow calibration, So fudging the engine HP number before calibrating the FF is probably not a good idea.

To Dynon: Is this a correct assumption?

Vern
========

Appendix, here is the result of my derivation of ROP HP calculation. Note that LOP, it would be FF*14.3 for normal compression engines (based on BSFC of 0.42 lb/hp at std temp).

Lycoming O-320 B and D series Horsepower Formula (Rich Mixture)

h=(H-((R-r)*(5.58-0.125*(M-m))/100 + 7.35*(M-m)) + 2.0*pa/1000)*sqrt((519-3.58*pa/1000)/(460+ta))

h% = h/H*100

where

Constants:

H= maximum sea level horsepower at maximum manifold pressure (from manufacturer’s data)
R= maximum sea level RPM at maximum manifold pressure (from manufacturer’s data)
M= maximum sea level manifold pressure at rated RPM (from manufacturer’s data)

For Lycoming O-320 -B and -D series:

H= 160
R= 2600 (Sensenich prop limit)
M= 28.6

Variables (inputs)

r= actual RPM
m= actual manifold pressure
pa= actual pressure altitude (altimeter set to 29.92 inHg)
ta = actual air inlet temperature at pressure altitude

Outputs

h = calculated horsepower
h%= calculated percent horsepower

 

[DBRV10]

However, I assume it also requires an accurate fuel flow calibration, So fudging the engine HP number before calibrating the FF is probably not a good idea.

To Dynon: Is this a correct assumption?

I would call that a correct assumption and correct procedure.

As for Dynon revealing a proprietary pice of code for a very good EMS…... :-? I would not even ask!

 

[dynonsupport]

LOP/ROP detection does use post-calibrated fuel flow as a parameter, so you should get your FF pretty close before you try and adjust it too much, or at least know you will need to re-adjust after a FF adjustment.