National Aeronca Association Bulletin Board

What is the suggested rpm for a mag check on a c90

Depends on how good your brakes are. There's no real reason you need to be above 1500 though.

Agree with Al. Doesn't make a lot of sense to be picking up any more gravel and sand than necessary.
Mikeb

I've got a C90 in mine and I use 1700. That's what the previous owner used and recommended so it's what I do. Don't know where or even if it's written anywhere.

I have looked high and low. Continental and Aeronca info. It is not written anywhere I have found. What rpm is going to give an accurate indication of a valid mag check.

Hi Captain,

I down loaded the Army L-16B Manual, which is for the C-90 and it states 1500 RPM for Mag Check. That is what I use as some of the others have posted and have had great results.

Ciao - Robert

An interesting question - I've always used 1,800rpm for mag checks on my Champ's C85, but without any real basis other than it being 75% of the 2,400 rpm max static.

Robert, your post about downloading the Army L16 manual intrigued me, as I've never come across a flight manual for a Champ; a little research led me to the item below (warning: it's a 4meg file).

http://www.aeronca.com/manuals/L16A_L16 ... ndbook.pdf

However, that is probably not the manual you refer to as it contains this rather surprising information on page 8, section 2-12 Before Take-Off:

d. Ignition system check - Accomplish at 2400 rpm for L-16A and at 2300 rpm for L-16B (my bold). The maximum allowable drop in engine speed is 75 rpm

Max static rpm for mag check? That's just got to be wrong!

Rich

I use 1500RPM only because my tach has a nice bold line there. It's easier to see the drop at a glance.
It's been my experience with the Slick stuff that you can have an acceptable drop at 1500 and at 2100 it causes all kinds of havoc. If I'm trouble shooting a mag issue I always check for problems at differing RPM's.
Paul

I know this has been about mag check, rpm doesn't seem to matter much, just don't do both once. I almost blew the exhaust off in flight from the back fire.
Carb heat is another matter, About once a year I get carb ice on take off, even after checking carb heat function on run-up. Worst cases were after the plane had been out in the rain over night. Run-up RPMs aren't enough to suck the last water out of the air filter and power loss becomes noticable about the time of rotation. Then you have to try to stay airborn while heat clears the carb before getting full power. Memorable moments.