Check your Tach

[andya]

What optical tach did you try?

[Alessandro]

Hi, I bought from Spruce TruTach II.
I checked in the past my tachometer with a digital one, used with model aircraft and I red, on ground, some differences.
My original tachometer with cable indicated more rpm than real.

I fixed the TruTach on my panel. It works perfectly in flight.
I will fix it with some Velcro and I will leave it.

these the numbers in cruise:

2500 indicated on std instrument are 2420 on real (trutach)
2700 are 2620 real
2780 are 2700 real.

+ 80 rpm

These are my performance, TRUE RPM:

Tripacer 160, prop 58”, 1000 ft , h1017, 20 celsius, 2470 rpm, 105 knots

WOT 2790 rpm, around 115 knots, but it is a little over the limit of 2700.

Infact I’m in doubt if re-pitch the prop to 59/60, but now during take off and climb is a rocket and I like it a lot!

What do you think about?

[Subsonic]

Alessandoro, I found I was suffering from an overly optimistic original mechanical tach by about 150 to 200 RPM near the false redline. My 58" pitch performance numbers were very similar to yours. Now, I really like my Electronics International digital tach that replaced the original mechanical spinning/magnetic thing. EI digital has Big easy to read numbers accurate to 10 RPM. I changed from a used but recently overhauled Sensenich 74MDM6-058 to a brand new Sensenich 74DM6-060 and noticed very little difference in climb performance. I gained about 3-4 mph in cruise flight - now 120 to 122 mph at 2450 at 7,000 ft under varying atmospheric conditions, and a full 4 to 5 mph at WOT. Now show about 129 to 131 mph at WOT at 7,000 ft at 2660 - 2670 RPM. I don't think it will go to 2700 now with the 60" without some descent help to get the RPM up. I have a 150 hp O-320 AIA rebuilt about 250 hours ago. I have to really hold the spit in the middle of my mouth and trim it for hands-off for those numbers. Any uncoordinated stuff or not holding level and the numbers fall off a mile or three, which is typical for me as I look out the windows and generally s-turn my way to wherever I'm headed. My static system is working properly and my AI is pretty accurate when I compare with GPS ground speed on no wind days. Generally, I just cruise at 2350 to 2400 and take whatever airspeed I get, with the ball mostly centered, because I like to look around. : )
-Subsonic

[Alessandro]

Alessandoro, I found I was suffering from an overly optimistic original mechanical tach by about 150 to 200 RPM near the false redline. My 58" pitch performance numbers were very similar to yours. Now, I really like my Electronics International digital tach that replaced the original mechanical spinning/magnetic thing. EI digital has Big easy to read numbers accurate to 10 RPM. I changed from a used but recently overhauled Sensenich 74MDM6-058 to a brand new Sensenich 74DM6-060 and noticed very little difference in climb performance. I gained about 3-4 mph in cruise flight - now 120 to 122 mph at 2450 at 7,000 ft under varying atmospheric conditions, and a full 4 to 5 mph at WOT. Now show about 129 to 131 mph at WOT at 7,000 ft at 2660 - 2670 RPM. I don't think it will go to 2700 now with the 60" without some descent help to get the RPM up. I have a 150 hp O-320 AIA rebuilt about 250 hours ago. I have to really hold the spit in the middle of my mouth and trim it for hands-off for those numbers. Any uncoordinated stuff or not holding level and the numbers fall off a mile or three, which is typical for me as I look out the windows and generally s-turn my way to wherever I'm headed. My static system is working properly and my AI is pretty accurate when I compare with GPS ground speed on no wind days. Generally, I just cruise at 2350 to 2400 and take whatever airspeed I get, with the ball mostly centered, because I like to look around. : )
-Subsonic

Thank you for your reply and for your feedback.

The TriPacer is new for me and “I’m playing” with everything to understand.

In the Aeroclub based in my airport there is a PA28 with a sensenich 74dm6-60, it’s grounded for maintenance, I can ask them if they loan me the prop to do a test.
But for a couple of miles in cruise I think I will leave the 58”, the only doubt that I have is WOT level flight that I reach 2790 rpm, I don’t know how it works in altitude...

I’m happy with my performance, are almost the same of your plane.

The only think that I have problems are the brakes.
I changed the pump with Steve’s but I think that I must upgrade to disc.
Alex.

[Steve Pierce]

I prefer to the climb, not gonna go that much faster when figuring a 3 hour leg and how much time it saves.

[Alessandro]

Hi Steve, I agree with you. I just have that doubt for that 90 rpm more than 2700 limit at full throttle.

It isn’t a problem in cruise at standard level, probably I will never fly WOT, but close to me I have the Alps and sometimes I flew at 10000 ft (never done with PA22).

[Pacerfgoe]

I’d leave it the way it is. The only way these things make rated power is if they get to the rated RPM. If you overpitch then you never make rated RPM and power. You can always pull the RPM’s back if needed.

I wish someone would come up with a modern two position prop like the older ones where we could have great takeoff performance and great cruise as well.

[Alessandro]

I’d leave it the way it is. The only way these things make rated power is if they get to the rated RPM. If you overpitch then you never make rated RPM and power. You can always pull the RPM’s back if needed.

I wish someone would come up with a modern two position prop like the older ones where we could have great takeoff performance and great cruise as well.

Yes, like the old “aeromatic”...

[Vagabondblues]

http://www.sensenich.com/shop/aircra...tol-propeller/

[J Ryd]

Ive got a low time A2B. It had a 60" prop and I had it repitched to 57. It maybe got me another 25rpm at best. Now about 2575rpm WOT. I question the repitch accuracy and may have another shop verify. Wonder why I cant get 2700? She runs like a top. All this done with a Trutak in the dash.

Jan