Newowner Posted September 3, 2021 Report Share Posted September 3, 2021 What do you see on RPM gage on takeoff. Mine has new engine and showing 2630. Old engine was showing 2710 on takeoff roll. May be governor need adjustment. Engine hat 7hrs on it. It’s 1967 M20F. Thank you. Quote Link to comment Share on other sites More sharing options...
hammdo Posted September 3, 2021 Report Share Posted September 3, 2021 Use a digital tach to confirm it's true RPM... Most A&Ps have them... -Don Quote Link to comment Share on other sites More sharing options...
Newowner Posted September 3, 2021 Author Report Share Posted September 3, 2021 I do have EDM 930. It’s new and I’m pretty sure it’s accurate. But I’ll double check with digital tach. Sent from my iPhone using Tapatalk Quote Link to comment Share on other sites More sharing options...
Jim Peace Posted September 3, 2021 Report Share Posted September 3, 2021 mine is set up for 2650 ....I have the JPI900 I guess I could ramp it up to 2700 but then I would get nuisance warnings.... Quote Link to comment Share on other sites More sharing options...
Bolter Posted September 3, 2021 Report Share Posted September 3, 2021 1 hour ago, Newowner said: What do you see on RPM gage on takeoff. Mine has new engine and showing 2630. Old engine was showing 2710 on takeoff roll. May be governor need adjustment. Engine hat 7hrs on it. It’s 1967 M20F. Thank you. I am sure someone will correct me if I am wrong, but you may need to adjust the prop to get full 2700 rpm if the governor adjustment is already maxed out. Quote Link to comment Share on other sites More sharing options...
carusoam Posted September 3, 2021 Report Share Posted September 3, 2021 Once rolling…. Whatever max rpm for your prop/engine is…. should be available… For full T/O power… 1) Max MP… kind of depends on where you are… depends on DA… 2) max RPM… as defined by your governor… 3) Max FF…. Kind of depends on MP of where you are… 4) example: for my engine, +200 rpm is +30hp, or +10% HP…. (IO550) 5) Randomly dropping HP will randomly increase your T/O distance…. 6) In cruise, we can sort of sub MP with RPM… but, on T/O…. There isn’t any excess MP to exchange for lower rpm… 7) Could be instrument error, could be gov setting error… 8) A good back-up tach can be found in your phone’s version of the AppStore… Sooooo…. New engine you say…. Make sure all three of these variables are producing the numbers you are expecting…. A back-up measurement can be made comparing T/O distance to book numbers… When the rpm isn’t up to speed… the FF and HP won’t be up to speed… and the T/O distance grows… non-linearly…. Anyone have insight on nuisance alarms for exceeding rpm on the various engine monitors? JPI EI Big G EIS I’m not a big fan of the nuisance, and I’m a lesser fan for changing my procedure to meet them… PP thoughts only, not a mechanic… Best regards, -a- Quote Link to comment Share on other sites More sharing options...
Guest Posted September 3, 2021 Report Share Posted September 3, 2021 7 hours ago, Newowner said: What do you see on RPM gage on takeoff. Mine has new engine and showing 2630. Old engine was showing 2710 on takeoff roll. May be governor need adjustment. Engine hat 7hrs on it. It’s 1967 M20F. Thank you. It should turn 2700 at full power. Static RPM on the ground is limited by the propeller, maximum RPM on the roll and in flight is limited by the governor. The governor high speed screw usually changes RPM by about 25 per revolution of the screw. Clarence Quote Link to comment Share on other sites More sharing options...
Raymond J1 Posted September 3, 2021 Report Share Posted September 3, 2021 Does it happen to some to derogate from the POH and take off with the regime chosen for the climb... On long track with more investigations than normal... But for nuisance problems ? Quote Link to comment Share on other sites More sharing options...
Pete M Posted September 3, 2021 Report Share Posted September 3, 2021 I would Wait for the engine to break in before adjusting rpm as long as its in the ball park. I try to resist demanding digital accuracy in an analog world:) Pete 2 Quote Link to comment Share on other sites More sharing options...
Guest Posted September 3, 2021 Report Share Posted September 3, 2021 10 hours ago, Pete M said: I would Wait for the engine to break in before adjusting rpm as long as its in the ball park. I try to resist demanding digital accuracy in an analog world:) Pete Break in has nothing to do with the engine turning rated RPM. A quick look at the engine test run sheet should confirm the engine turned rated RPM in the test cell. Clarence Quote Link to comment Share on other sites More sharing options...
ilikethewoods Posted September 4, 2021 Report Share Posted September 4, 2021 Not trying to jack this thread for my story. I have the OG RPM gauge and...*should've listened to everyone saying use a digital RPM first to verify the OG gauge is reading correctly*. Well I went ahead and adjusted my prop-gov (the little stop screw at the Prop Governor). Did high power runs down the runway, flew, adjusted it so it sat right at 2700 inflight. Fast forward, had an instructor fly with me not to long ago and ask: how come we're not climbing, isn't this a Mooney. I charged that one to the game and thought in my mind: at least I own an airplane...! Installed a JPI 830, with the RPM harness. Guess what, my OG gauge is about (cant remember exactly) off. So at 2700, I'm really below that RPM. Now back to adjusting, high taxing, more flying for a problem that could've been resolved with a simple effort on my part. That's my story. 1 Quote Link to comment Share on other sites More sharing options...
Raymond J1 Posted September 4, 2021 Report Share Posted September 4, 2021 (edited) The mechanical speed gauge is driven from a cascade of sprockets with decimal transmission ratios, with a more or less used flex, more or less homokinetic. The RPM indication is approximately good, since the aircraft left the factory. By the way, it is certified with this approximate indication. What is the point of knowing that your engine runs exactly at 2700 rpm rather than at the indicated 2700 rpm + or-50 rpm ?. What is accepted is that the mechanical instrument is verifiable, that there is a calendar of verification for it, so that its indication is good with the tolerance defined from the start. Also, with this mechanical instrument, it is quite possible to obtain the correct setting as certified and also the performance of the certificate. In itself, it is enough. Edited September 4, 2021 by Raymond J Quote Link to comment Share on other sites More sharing options...
A64Pilot Posted September 4, 2021 Report Share Posted September 4, 2021 On 9/2/2021 at 11:42 PM, Jim Peace said: mine is set up for 2650 ....I have the JPI900 I guess I could ramp it up to 2700 but then I would get nuisance warnings.... This is the reality of modern digital instrumentation on an engine Certified in the Analog world. Its not just pistons even legacy turbines it’s normal if you exceed takeoff RPM even by 1 RPM for it to be an over speed. So as you say, you either live with the nuisance alerts or give up some HP. I would set it at 2700 and just dial back the RPM a smidge to prevent the alerts, that way if you need the HP from a full 2700 you still have it. Quote Link to comment Share on other sites More sharing options...
PT20J Posted September 4, 2021 Report Share Posted September 4, 2021 Nuisance warnings for minor, temporary exceedances are a common complaint with electronic primary instruments. The G3X EIS solves this by having separate gauge marking and alert settings, so you can set the alert at a slightly higher value. Skip 1 Quote Link to comment Share on other sites More sharing options...
Oscar Avalle Posted September 4, 2021 Report Share Posted September 4, 2021 On take off roll I get 2710 RPM. My field is at 2,100 feet and density altitude is often above 3,000 Oscar Quote Link to comment Share on other sites More sharing options...
jaylw314 Posted September 4, 2021 Report Share Posted September 4, 2021 I thought I recalled reading somewhere that any excursion over 2700 RPM more than 6 seconds needs to be logged, and any over 2750 needs to be inspected before further flight. I can't recall if that was instructions from Lycoming, Hartzell, or Mooney, though, and I'm not sure of those numbers. Does anyone know that off hand? Quote Link to comment Share on other sites More sharing options...
Pete M Posted September 4, 2021 Report Share Posted September 4, 2021 23 hours ago, M20Doc said: Break in has nothing to do with the engine turning rated RPM. A quick look at the engine test run sheet should confirm the engine turned rated RPM in the test cell. Clarence Not to be argumentative but Did they use his prop and governor in the test cell? I base my opinions on experience. In theory i agree with you but in practice i've seen take off rpm change slightly after break in. A Lot of moving parts working together. Obviously a digital tach check is required. Since its not an overspeed could it really hurt anything to wait to correct? Quote Link to comment Share on other sites More sharing options...
A64Pilot Posted September 4, 2021 Report Share Posted September 4, 2021 (edited) 3 hours ago, jaylw314 said: I thought I recalled reading somewhere that any excursion over 2700 RPM more than 6 seconds needs to be logged, and any over 2750 needs to be inspected before further flight. I can't recall if that was instructions from Lycoming, Hartzell, or Mooney, though, and I'm not sure of those numbers. Does anyone know that off hand? Your probably right, but I can tell you it’s extremely common for float planes to set theirs 100 RPM high, it’s tough to get on step sometimes and that extra 100 really makes a difference. ‘If memory serves, and this goes back to 1987, but we flew the IO-360 in the Army TH-55 at 2900 RPM continuously? We had a 5 min manifold pressure max that was ignored as you would never learn to hover if you didn’t. I know that’s a different engine, and I’m not abdicating exceeding limits, just think the limits have a pretty big safety cushion. Are you reducing the life on an engine by exceeding them? I’d bet money you are. Edited September 4, 2021 by A64Pilot Quote Link to comment Share on other sites More sharing options...
MikeOH Posted September 4, 2021 Report Share Posted September 4, 2021 3 hours ago, jaylw314 said: I thought I recalled reading somewhere that any excursion over 2700 RPM more than 6 seconds needs to be logged, and any over 2750 needs to be inspected before further flight. I can't recall if that was instructions from Lycoming, Hartzell, or Mooney, though, and I'm not sure of those numbers. Does anyone know that off hand? Kind of....here are the details, but if less than 10% (270 rpm) for less than 3 seconds, you are ok. https://www.lycoming.com/sites/default/files/SB369S Engine Inspection after Overspeed.pdf 1 1 Quote Link to comment Share on other sites More sharing options...
jaylw314 Posted September 5, 2021 Report Share Posted September 5, 2021 55 minutes ago, MikeOH said: Kind of....here are the details, but if less than 10% (270 rpm) for less than 3 seconds, you are ok. https://www.lycoming.com/sites/default/files/SB369S Engine Inspection after Overspeed.pdf Thanks, I read that and then couldn't remember where I read it, and obviously remembered all the numbers wonky. The part that go me was that any oversped (even 10 rpm over) for more than 3 seconds TECHNICALLY needs to be logged in the engine logbook (which I'm guessing nobody does). 2 hours ago, Pete M said: Not to be argumentative but Did they use his prop and governor in the test cell? I base my opinions on experience. In theory i agree with you but in practice i've seen take off rpm change slightly after break in. A Lot of moving parts working together. Obviously a digital tach check is required. Since its not an overspeed could it really hurt anything to wait to correct? IIRC they use paddle blades on the test stand, and they can control the drag they produce to produce a specified RPM, so it's pretty much like a prop and governor. Quote Link to comment Share on other sites More sharing options...
PT20J Posted September 5, 2021 Report Share Posted September 5, 2021 47 minutes ago, jaylw314 said: IIRC they use paddle blades on the test stand, and they can control the drag they produce to produce a specified RPM, so it's pretty much like a prop and governor. That’s correct. The governor is considered an accessory, not a part of the engine. Engines are run in a test cell with a test club that generates the proper drag (torque) without generating much thrust - the opposite of a propeller. 1 3 Quote Link to comment Share on other sites More sharing options...
jaylw314 Posted September 5, 2021 Report Share Posted September 5, 2021 44 minutes ago, PT20J said: That’s correct. The governor is considered an accessory, not a part of the engine. Engines are run in a test cell with a test club that generates the proper drag (torque) without generating much thrust - the opposite of a propeller. Huh, so that's what they look like. How do they adjust the drag, though? Quote Link to comment Share on other sites More sharing options...
PT20J Posted September 5, 2021 Report Share Posted September 5, 2021 29 minutes ago, jaylw314 said: Huh, so that's what they look like. How do they adjust the drag, though? Different clubs depending on engine. Quote Link to comment Share on other sites More sharing options...
Raymond J1 Posted September 5, 2021 Report Share Posted September 5, 2021 3 hours ago, PT20J said: Different clubs depending on engine. It seems to me that the clubs this is just for the cooling flow in the old facilities with mechanical froude brake. Today, the installation is often an electric (generator) or hydraulic froude brake, the cooling installation is specific and there is no longer a club. 1 1 Quote Link to comment Share on other sites More sharing options...
Prior owner Posted September 5, 2021 Report Share Posted September 5, 2021 16 hours ago, A64Pilot said: ‘If memory serves, and this goes back to 1987, but we flew the IO-360 in the Army TH-55 at 2900 RPM continuously? We had a 5 min manifold pressure max that was ignored as you would never learn to hover if you didn’t. I That is also my recollection from flying the TH-55! Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.