red indication on tach

[dogone]

I have an avcon 180 convert with constant speed prop. Got it a few months back. The tach has a 2700 red line but with the right light I noticed red from about 2100 to 2350 rpm. The previous owner is not available. Is this a recycled tach or should I avoid settings using these rpms. The lycoming card that came with plane has many settings using these rpms. Just being cautious!

[c170b53]

What you have to check is your propellor and blades. Hartzell TC docs P-920 will list the limitations which if applicable should be represented on the gauge.
You could look at your STC paperwork but looking at your engine data plate will tell you what you really have. Looking at your propellor logbook and confirming the prop hub s/n will confirm your looking at correct data for your prop. Then consult the Hartzell manuals on their website for the info pertaining to what you really have and hope the parts are approved under the STC . The STC is also listed on their website and the approved parts if you're short on paperwork which I don't no how that happens

[Metal Master]

I have an avcon 180 convert with constant speed prop. Got it a few months back. The tach has a 2700 red line but with the right light I noticed red from about 2100 to 2350 rpm. The previous owner is not available. Is this a recycled tach or should I avoid settings using these rpms. The lycoming card that came with plane has many settings using these rpms. Just being cautious!

My Buddies 172 tail drager has the same Engine Prop combination. If you have a Horizon Tachometer which I presume you do the original STC for the tachometer required that the engine - propellor limitations be sent to the manufacturer (Horizon) to have the red line, green arc and yellow cautionary items be programmed into the tachometer. If you do have a Horizon tachometer those numbers should be in Bold numbers on the front of the Tachometer. But other wise the Limitations should be in the Supplemental Type Certificatre for the Engine - Prop combination. Barring anything else it should be found as C170B53 noted.
Also if you have a Horizon Tachometer there should be an operators manual for it as well. If you do not have one contact Horizon Instrument Sandi will help you out. Be prepared with your Horizon Tachometer part number and serial number.
Jim

[c170b53]

Jim, I think I (we) need more info from this owner to give a specific answer, so I went generic. I also thought new owners have to get back to the basics of understanding what they have. Heck sometimes I forget to think about the numbers because I generally just assume things.
Recently I have been looking for another plane and thought I had found one. It was described as a 56B but the s/n of an early 52B meant the logbooks had no real meaning. A pic of the plane from a distance told me I was looking at at least 4 different planes.
Did the present owner know? I'm not sure the present mechanic knew! I'm getting older and I certainly don't have Metal Masters ( Jim's) extensive knowledge but now we have (and so we should) a new generation acquiring old planes.
That's the basis of my reasoning for my very unspecific info to this gentleman. The older these planes get the more likely there's been substitutions for the approved equipment. Some of these alterations may have been covered by a 337 but sometimes it's a stealth installation. When all else fails, the numbers tell the true story.

[DaveF]

If your airplane has a Lycoming O-360-A1A and a Hartzell HC-C2YK-1BF propeller with F7666-2 blades, modified per Avcon STC SA806CE, the tach should have a yellow arc from 2000 to 2250 and a placard that says "Avoid continuous operation between 2000 and 2250 rpm". This is to avoid an engine/prop resonance.

[JohnNielsen]

My C170B with MT Prop

Metal props on a Lyc -360 all have this limitation due to the natural harmonic frequency of the metal blades working at those RPM's WITH engine firing pulses that result in dangerous vibration levels in the engine/prop. There is a heavy harmonic balance ring that is installed behind some of them to eliminate this RPM range restriction.

Best cure is to install a MT Composite 2 or 3-blade prop. The wood/composite core of the MT Props absorb engine pulse vibrations and have no RPM range restrictions....they are also lighter by like 20+ pounds and are more efficient at turning HP into thrust as a result. More info here: www.Flight-Resource.com

John Nielsen
1955 C170B w O-360