What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Baffling caution range marked on tach

jimw

jimw

I'm New Here
I've just bought a flying -9A with an YO-320-D1A and a Sensenich 70CM6S9. One of its two tachs has a yellow band marked between 2,000 and 2,250 RPM; the other does not.

Both Lycoming and Sensenich have told me that no such limitation pertains to their components, but that there could be an issue with the airframe/engine/prop combo of which they're unaware.

Does the generic -9(A) have any RPM limitations with this engine and prop, beyond the 2,600 red-line?
 
Last edited:
Interesting…. Two tachs? Pictures please. I’m thinking that one is on the EFIS and one was scrounged from a used parts place and thus has a yellow arc that doesn’t matter.

Just a guess, perhaps a picture would yield a better guess by others.
 
jimw said:
I've just bought a flying -9A with an YO-320-D1A and a Sensenich 70CM6S9. One of its two tachs has a yellow band marked between 2,000 and 2,250 RPM; the other does not.

Both Lycoming and Sensenich have told me that no such limitation pertains to their components, but that there could be an issue with the airframe/engine/prop combo of which they're unaware.

Does the generic -9(A) have any RPM limitations with this engine and prop, beyond the 2,600 red-line?
Click to expand...
I would look at the tach that has the yellow arc for a part number. Maybe that tach was sourced from a type certified airplane that needed the limitation for a different prop... Never seen an RV with a caution range
 
The TADS for the UK RV9s only have the following:

Engine Limitations
Maximum Engine RPM: 2700 (2600 rpm when Sensenich 70CM 2-blade metal propeller fitted to O-320 or IO-320 engines; 2800 with certain O- 235 engines)
 
There is a caution range on some Lycoming engine models with certain constant speed, propellers, in the RPM range you listed if the manifold pressure is above a certain value.
 
Is there any chance the plane originally had a different prop on it that had a restriction for continuous use? I would ask the original owner, if that's possible. Perhaps they wrote something in the POH about it?

If there is no legitimate RPM restriction, that should be easy to change on the Dynon EFIS.
 
D-Dubya said:
Is there any chance the plane originally had a different prop on it that had a restriction for continuous use? I would ask the original owner, if that's possible. Perhaps they wrote something in the POH about it?

If there is no legitimate RPM restriction, that should be easy to change on the Dynon EFIS.
Click to expand...
There is such a chance. The airplane did come with a return oil line for a constant speed prop, though it looks unused. I'll dig in. Thx.
 
Last edited:
I fly a friend's GlasStar occasionally and it has a similar yellow arc on the dynon. He didn't build the plane and doesn't know what it's for. My best guess is that the original builder programmed it in as a reminder for when he might want to use carb heat. If you don't discover an RPM limit on teh prop that would be my guess here as well.
 
Desert Rat said:
I fly a friend's GlasStar occasionally and it has a similar yellow arc on the dynon. He didn't build the plane and doesn't know what it's for. My best guess is that the original builder programmed it in as a reminder for when he might want to use carb heat. If you don't discover an RPM limit on teh prop that would be my guess here as well.
Click to expand...
I'm thinking that the proper range for cautionary carb heat use would include settings lower than 2,000 RPM. Does that make sense?
 
I have a very similar yellow arc on my tach (2050 to 2300), as mandated by MT propeller for their MTV-11-C/183-59 on a Lycoming O-320 (when operated above 20 in. Hg.).

It is also possible that the EFIS was purchased second hand from someone who had a similar setup.
 
A common restriction for some 4 cylinder Lycomings with some Hartzell constant speed props reads, "Avoid continuous operations between 2000 and 2250 rpm."
If that doesn't apply, it's easy to change in the Dynon even if you don't have the manual.
If your Sensenich has a 2600 rpm limit, you can change that at the same time. A piece of red tape on the analog tachometer can make everything agree.
 
Thanks to all who replied. My takeaway: The yellow arc is just decoration unless/until I replace the FP prop with a CS that has such a limitation. I'll work some magic with the Dynon to remove the marking. A correction to the electric tach red-line will follow.
 
Tdeman said:
similar yellow arc on my tach (2050 to 2300), as mandated by MT propeller for their MTV-11-C/183-59 on a Lycoming O-320 (when operated above 20 in. Hg.).
Click to expand...
Tdeman, would you have the ref from MT for that?
Asking cos I have the same 2050-2300 max 5 minutes restriction, but on a O-360-A1A married to a MTV 12B, and couldn't find where the source of the restriction is :unsure:
 
You must log in or register to reply here.
Back
Top