Low RPM on Vagabond w/ Lycoming 0145

[mikegordon]

Ok, this might be obvious to some, but not to me. Why is it that I am not getting the redline RPM (~2550) at full throttle on takeoff? I understand that the 65 HP Lycoming only puts out the 65 HP at redline. It would be great to have more HP on takeoff. We have a wood Sensenich prop (w/ metal leading edge). Regards, Mike (N4318H)

[d.grimm]

Mike,
That's the advantage of a constant speed prop. Your prop is a compromise between climb and cruise since the prop blades don't adjust. According to the Type Certificate Data Sheet (A800) your static RPM should be between 2370 to 2110 RPM. In level flight at full throttle do you see 2550 rpm? The TCDS shows two props, a 70LY34 and a 70LY 38. The 70LY34 would give you better climb. If those things don't work I have the paperwork for a C-85-12 that I can send you.
Dave

[mikegordon]

Dave,
This weekend when I go flying, I will look at the tach at full throttle at level flight, and I'll get the prop model number and let you know.

Thanks for the reply.

Mike

[Stephen]

Your tachometer may not be exactly accurate.

[Tripod]

You can easily check the accuracy of your tachometer with a hand-held digital tach commonly used by radio control modelers. Just point it through the windshield. They're fairly inexpensive and available at most model hobby stores. Here's a link to a popular mail-order store:

http://www3.towerhobbies.com/cgi-bin/WT ... &search=Go (http://www3.towerhobbies.com/cgi-bin/WTI0095P?FVSEARCH=tachometers&search=Go)

On second thought, the newer meters may not work. I'm reading that they must be held within 12" of the prop; not too practical in this case.

I have an old Heathkit hand-held tach that worked for me when used from behind the windshield during flight. I guess it used different detectors than the new tachs (?).

-dave

[deandayton]

I can't speak for the handheld tachs in your weblink. But I bought an inexpensive "modelers" handheld tach just a few years ago and it worked fine from the cockpit. I have used it both on the ground and in flight.

I think it was this one http://www.aircraftspruce.com/catalog/i ... etouch.php (http://www.aircraftspruce.com/catalog/inpages/onetouch.php)

[Steve Pierce]

According to the PA15 Type Certificate Data Sheet it should turn no more than 2370 rpm and no less than 2110 rpm static. What are you getting for a static rpm?

[mikegordon]

Thanks for the advice on the hand-help tach. What is meant by "static rpm"- full throttle on takeoff?

Mike

[JohnW]

No. Wide open throttle with brakes locked.