M.A.P.

Gday Mike,

"....p35 section 8.3 and 8.4"

My Operators Manual. Printed 12/09/2018 would seem to be diffrent to your reference above.

My Chapter 8. SET-UP OF PROPELLER PITCH STOPS.  Pages 61 - 69

My reading of this chaplet suggests to me, that my Airmaster is operating as intended, without need to change the factory settings.

Weather has prevented flying since I asked my question about MAP & RPM. Your responses have given me cause to question my observations.

FYI - All my figures are with the Controller in the Auto Mode. I have played with the Manual Override but not recorded any figures. I have not used the Hold option. 

At the next suitable opportunity, I will test fly and make more careful observation/notes of  RPM/MAP, Alt., OAT, Air/True Speed

You're right, my manual is v3, 12/2/10. However having looked at your (the latest) edition on the website, the content of chap 8 is the same, just different page numbers.

More Comment:

My Rotax figures for RPM / MAP come from the Operators Manual Chapter 5. Performance and Fuel Consumption, Page 5-6

Most recent flight -  80 minutes at 4500 ft, 5030 RPM / MAP 24.7, Air Speed 130 knots (TAS 135 Kn)  OAT 08C

Rotax chart suggests MAP 26"

Hi Sean,

With the disclaimer that my opinion is probably worth exactly what you're paying for it (i.e., nothing):

These figures just indicate that your airframe can do 130 knots while using less than 75% power. I seriously doubt you could do any damage to the engine by running it at those settings, but you may get slightly better fuel economy by experimenting with the settings for one of the lower power levels listed in the table. (I assume we're talking about the table on page 5-6 of the current OM-912 here.)

P.S. My Gazelle is no better in carrying capacity than a Sonex in space or weight either, and holds a lot less fuel - but it's fun to fly and I like the challenge of keeping an orphan type airworthy. I do appreciate the thought behind your alternative airframe suggestions though!

Sean Griffin wrote:

More Comment:

My Rotax figures for RPM / MAP come from the Operators Manual Chapter 5. Performance and Fuel Consumption, Page 5-6

Most recent flight -  80 minutes at 4500 ft, 5030 RPM / MAP 24.7, Air Speed 130 knots (TAS 135 Kn)  OAT 08C

Rotax chart suggests MAP 26"

I still can't understand your point.

The manual says that 5000rpm at 26" gives 75% power (I think you can assume this means at ISA although it isn't stated.)

You are CHOOSING to run at 5030 24.7", therefore producing somewhat LESS than 75% power. There is nothing pre-ordained about it. You appear to think that at 5030/24.7 you are getting 75% power - why do you think that?

Leave the Airmaster controller in cruise position so you will get 5000rpm +/- a few, open the throttle a bit more to get 26", and you will then be CHOOSING to run at 75% power. Presumably your speed will increase, or you can keep the speed the same and have some rate of climb, or push the stick forward and see if you reach Vne. Within a reasonable band, rpm and MAP will be constant, what will vary is the prop pitch.

The curve on P5-7 shows that you should be able to achieve 75% power at 5000rpm at density altitude up to about 2200m i.e. 7250ft but at that DA it will need WOT. At lower DA it will need less throttle.

It is all under your control.