Ibra wrote:
n 4 cylinders Mooneys, If one is looking to save fuel and cover distance: WOT, 2200rpm, 30lop is the sweet 55% economy in 6kft-8kft band (2200rpm & 28mp < 75% power and one can lean at any altitude) If one is looking to get there fast (as some think it’s the essence of Mooneys): WOT, 2500rpm, 100rop is the sweet 75% power in 6kft-8kft band
Yep.
One should not forget that Mooney always has been about speed, particularly in the US. Hence no wonder that their former top guy recommends going balls to the wall. Mooneys in many regards are looked at as “Ferraris of the skies” and that explains why those of us for whom the main advantage of a Mooney is efficiency get shot down in the community when asking about how to get the most gas mileage e.t.c.
If you follow Mooneyspace you might have noticed I got total lack of any understanding when I wondered aloud about how to operate the 3-blade prop I got as there are no power setting tables available for the regime the RPM restriction imposes. The answer I kept getting is, just get into the damn airplane and fly it and when you get short on fuel land, fuel and carry on. Which, in the US can be done, here the situation is different, you usually can’t do that particularly on a longer cross country and with all the PPR restrictions we have.
The fact that range is the best speed mod has not necessarily a lot of meaning in places where you have a suitable airport with gas every 15 minutes of the way.
There is a fantastic amount of stuff out there about engine management and most of it is very old stuff based on no engine instrumentation and thus no understanding of what is going on.
Basically the profile is Full throttle and max RPM for climb all the way to TOC and then fly WOT and 2500 RPM leaned to best power or best economy
Yes WOT is way to go for climb and cruise altitudes, anything else drags the engine…at low levels setting less throttle is OK in cruise
For RPM, I don’t think 2500rpm from Bob Kromer is the perfect number for cruise? 1/ with CSU propeller stays efficient down to 1950rpm (it may lose 1% theoritical efficiency but low rpm on 3 blades get you a reduction in froction, noise, blade interaction and -0.5gph in fuel burn) 2/ the propeller rpm has to be adjusted higher with altitude if you are after best power (100rop) above 10kft 3/ Mooney POH best economy (max egt to 25rop) is useless if one could operate smoothly in LOP with fuel flow, cht/egt monitors on each cylinder…
In 4 cylinders Mooneys,
For MP & RPM in climb, yes I do hear 25/25 in 4 cylinder Mooneys, I have not figured out where that comes from? poh clearly state wot/max for max climb and 26/26 in normal climb…I am sure the 25/25 relates to noise harmonics or maybe some undocumented CPL Complex training?
NCYankee wrote:
I use full throttle and max RPM for climb.
That is also what Bob Kromer recommended for the Mooneys. Unfortunately those articles have gone by now but they were quite good.
Basically the profile is Full throttle and max RPM for climb all the way to TOC and then fly WOT and 2500 RPM leaned to best power or best economy. He and others claim that this is the best profile you can fly a non turbo engine. Clearly, CHT must be monitored in certain installations, particularly in Mooneys, if flying with full power and several engines actually have limitations on the use of full take off power to a certain time limit.
I’ve done this twice, on departure from Samedan. The change in performance is noteworthy if you leave max RPM on.
Take off power reduction to 25/2500 often is used in Europe in particular for noise abatement. And clearly, 2500 RPM will reduce the ambient noise vs 2700. So that is why in terrain where max climb is not necessary, we still do it. Apart from that, the POH actually refers to 25/2500 as climb RPM.
What I’ve also seen in this regard is that while MP stays where it is (usually 26-27 in low elevations) only RPM is reduced for noise. By the time this is done, MP usually is close to 25 anyhow.
The app author is releasing an updated iPhone app soon.
Yes, thanks. There’s no iPhone version, iPad only. That explains why I couldn’t find it when searching from my phone.
Does this work: https://apps.apple.com/gb/app/aircraftpower/id718023187
Dan wrote:
Jim Petty has created a fantastic and free app called AircraftPower available on the App Store.
I can’t find this on the iOS App Store (I’m in the UK). Maybe it’s locked down to certain countries? Has anyone in the UK managed to find/download it?
To lean the engine, I just set the fuel flow
That is what the “constant EGT climb” is. All the way from sea level to the operating ceiling, only the mixture is touched.
That is also fine for climbs to low level, say 5000ft, except that
So I set 23"/2400rpm then. Others set 23"/2300rpm, etc. But the fuel flow for low level is 11.7 USG/hr and that is the “immediate target” at top of climb.
I use full throttle and max RPM for climb. I used to bring the power back to 25 square, but I have owned my Bonanza for going on 44 years and as it got updated with engine monitoring equipment and digital fuel flow, it became apparent that bringing the throttle back to 25 inches increased the EGT and CHT during the climb. At full throttle, the fuel flow is extra rich and the initial throttle reduction does not change the MP indication, but primarily reduces fuel flow, so you are leaning the engine by bringing the throttle back to 25 inches. On my Bonanza with an IO520BA engine, the initial reduction of the throttle makes no indication of MP reduction and you have to make a substantial reduction before anything shows up on the MP. Only belatedly, the MP indication starts to come down and eventually starts to follow the throttle reduction. So leaving full throttle keeps the engine cooler. I am in no hurry to reduce the RPM, but usually do it after 1000+ AGL. By the time I reach 4000 or so a little over 3 minutes, the full throttle is down to 25 inches anyway, so I view making regular changes to keep the MP at 25 inches a waste of effort and IMHO is harder on the engine. To lean the engine, I just set the fuel flow. 12.5 GPH gives me close to 65% which is what I use for cruise. I have found that the digital fuel flow is very accurate but the indication lags behind, so I use the analog fuel flow (fuel pressure calibrated in fuel flow) is less accurate but very repeatable and near instant indication, so I just pull the mixture until the analog gage reads 12 GPH (the big pull) and the digital settles out at 12.5 GPH. The Bonanza of my vintage has a combine MP/FF indication on the same instrument, which during climb, I set the fuel flow by sight where the MP indicator on the LH side forms a straight line with the FF indication on the RH side. I lean to 12.5 GPH for cruise at any altitude up to about 8000 MSL. Above that altitude I will lean more.
