In my case, when on the ground before takeoff, I start with flat pitch at 1500 rpm, A fairly easy pull of an inch or so drops the rpm to 1200. A second more aggressive pull returns the rpm to 1500 rpm. I have noted over the last fifteen years that in flight the required force has progressively increased. I have mitigated that by dropping the rpm at pitch change. I am now probably closer to 1800 rpm than 2200. There is some evident wear on the pitch change rods, likely creating some binding due to greater centrifugal force at increased rpm. Not to suggest that this is yet an airworthiness issue.
M On Sun, Oct 14, 2018, 12:38 PM <[email protected]> wrote: > Hi Jarek, > > > > With our newish prop (280 hours, also with aSN that starts with A), we > shift into cruise at about 1800-2000 rpm, and find that when in flight (as > opposed to pitch changes on the ground during run-up), the pull requires a > bit more force, but the lever should only come out about 2-4 cm. I would > describe the pull as steady but not sharp and not particularly slow. Kristn > just uploaded a short video of me this > https://m.youtube.com/watch?v=VyYbV802UAM > > Tom > > > > Sent from my Windows 10 device > > > > *From: *Jarek Steliga <[email protected]> > *Sent: *Sunday, October 14, 2018 13:57 > *To: *[email protected] > *Subject: *Re: [DOG mailing list] Hoffman propeller HO-V62-R / Issues > withchanging positon to cruise > > > > [image: smigło dimona nr.JPG] > > Tom and Nigel, > > > > Perhaps that's where the shoe pinches? Perhaps the manner I pull the pitch > change handle needs to be looked into before other reasons are examined > (shaft runout or two bearings not touching the driven plate > simultaneously). It is unlikely that serious mechanical malfancions occur > just a year since that particular prop had been released by Hoffman from > overhaul, with the time of actual use not exceeding 20 hours. > > > > I have to admit that I always pulled the handle all the way and only now > having read your remarks realize that perhaps that was completely wrong. > Can the handle be pulled slowly untill the drop of RPM occurs or does it > have to be a shorter but energetic jerk? > > > > Is the jury out on the RPMs at which the pitch change should be made? Is > it 2200 or between 1800 and 1900 or what? Which works best for you? > > > > > > Regards > > > > Jarek > > > > > > > > > > > > > > > > > > > > niedz., 14 paź 2018 o 14:03 Nigel Baker <[email protected]> > napisał(a): > > Hi Jarek I checked the Hoffman Prop manual and indeed you are correct. > > However all on this list will say 2200 RPM I think. > > Expect a drop of 200 rpm for cruise so aim for a drop of 250 momentarily. > The idea is to provide enough clearance for the slide to move into place in > the Centre stem nut shoulder without the RPM dropping so far that the > centrifugal force drops so much the slide will not stay out in the cruise > position. > > It is a balancing act between RPM and hand force on pull handle. > > As Tom says if you pull the change handle far enough back it will rumble > like hell as the blades are stalling due to too high an angle of attack. It > won’t do any damage but is unnerving. > > This takes a little finesse but once mastered you will find it easy enough. > > > > Nige. > > > > > > > > > > *From:* [email protected] <[email protected]> *On > Behalf Of *Tom Preisser > *Sent:* Sunday, October 14, 2018 8:19 AM > *To:* [email protected] > *Subject:* Re: [DOG mailing list] Hoffman propeller HO-V62-R / Issues > with changing positon to cruise > > > > Perhaps you are pulling the handle too far out ? Just pull it a little, > because if you pull it too far the prop will rumble, the rpm will fall too > much, and no change to cruise will happen. > Let us all know what you discover. > > On Friday, October 12, 2018, Rob Thompson <[email protected]> wrote: > > 1- Normally the RPM on change should be 2200 to go into cruise. > > 2 - Sounds like the pitch change/feather plate on the rear of the prop > is not running true or alternatively the two bearings that contact it are > not touching at the same time. > > Use a finger dial guage to check if the plate is true. > > regards > > Rob > > Rob Thompson > > 0429 493 828 > > (Please note that my new email address is [email protected]) > > > > On Sat, Oct 13, 2018 at 6:53 AM Jarek Steliga <[email protected]> > wrote: > >> > >> > >> Hello, > >> I am quite new here (have owned Dimona for only 3 months). > >> Despite scrupulously folliowing the instructions regarding the required > RPM-s of between 1800 to 1900 at which the propeller pitch is changed from > START to CRUISE in midair, I have only succeedded twice despite numerous > attempts. Also pulling the pitch lever in the cockpit results in scary > vibrations which discourages me from continuing my trial and error methods. > Can someone please help? > >> > >> Best regards > >> Jarek > >> > > > > --------------------------------------------------------------------- > You are subscribed to the Dimona Owners Group mailing list. > To unsubscribe, send email to: [email protected]
