Acclaim with 310 HP.

[RobertoTohme]

Quote: Mcstealth

Roberto. What has happened to your GPH? Good, bad, or otherwise?

Mcstealth

[rnation]

Roberto, Wondering if you noticed any changes in CHT's and TIT's

[RobertoTohme]

Quote: rnation

Roberto, Wondering if you noticed any changes in CHT's and TIT's

[KSMooniac]

Roberto, why do you pull back to 2600 RPM for part of the climb? 

[RobertoTohme]

Scott,

I've been trying to replicate the conditions used by Midwest Mooney when they did their record run from sea level to FL250, and Justin advised me that after takeoff, around 3000 ft, they backed down to 2600 rpm but cited no particular reason.  This same engine model runs on Cessumbias at 2700 rpm unrestricted, and the STC granted to MM states that while it can run at 2700 with no time limits during climb, they advise to reduce rpm to 2600 "after obstacles have been cleared"...  The engine certainly can sustain 2700 much longer, but I guess that TBO may be reduced by doing so continuosly.  I'll try next time going all the way to FL250 at 2700 rpm to see how much climb time I can still chop off my 2 previous pulls; I will fly this sunday, but the winds aloft forecast at FL240 is almost 90 kts and well aligned with the nose of the plane so I'll stick to the "low and slow" technique at 12K, hoping that my return trip on tuesday the jetstream will back up north and higher bugging you guys instead of us southerners... LOL!

[KSMooniac]

Roberto, the reason I asked is that pulling the prop back "to save the engine" is just an Old Wives Tale that is still out there.  I took the Advanced Pilot Seminar class in 2007 and they shattered the myth with some facts and data...which I have unfortunateyl forgotten already!  I'll dig through my course notes when I get a chance and see if I can find the reasons why you should just leave it at 2700 until you set cruise power.

I join you in wishing the jetstream would go back north!  We had 60s last weekend when I started my owner-assist annual, and today we're in the 30s.  And we're not northerners here in KS!    I'm from TX and will always be a Texan...I'm just residing in KS currently. 

[TurboExec]

Scott you got a little over-excited there!

[RobertoTohme]

Scott,

Math alone, 200 extra RPM times 2000 hr. theoretical TBO is an extra 400,000 engine turns...  I know the engine is certified at 2700 on "other" applications, and understand that those list 1800 hrs. TBO...  Who knows, but I'll sure start trying the max effort climb leaving the prop at 2700 all the way up...  and yes, you can keep the jetstream to yourselves!!!  LOL  We don't need no jetstream here!  Makes the FL's pretty slow westbound...

[KSMooniac]

Roberto, I looked at my notebook from the class and reducing RPM while otherwise holding the mixture and MP constant results in higher internal cylinder pressures (ICP) and causes the peak pressure to occur earlier relative to the crank position.  Both of these consequences are less-optimal than running at max RPM.  Engine wear is not caused by extra revolutions of the crank, it is caused by the heat and pressure inside the cylinders, so for optimal engine life you want to operate in a way to reduce the heat and ICP.  That is why cylinders sometimes don't make a full TBO run while the crank and bearings (lower end) usually are fine so long as there isn't a prop strike or long periods of storage that result in corrosion.

I would encourage you to take the Advanced Pilot Seminars course if you want to learn all about it.  There are a lot of misconceptions that are still passed around the pilot community that have no basis in fact.  The APS crew will really give you a lot of education in a short amount of time!

[RobertoTohme]

Thanks for the input, Scott; I'll look into APS and find some time to attend.

Cheers.