iPhone as a diagnostic tool

Darren S · #1 02-21-2011, 12:55 PM

No it's not a new app but I am having an issue with my -7 running rough. The stats: -7, IO-360, Hartzell C/S prop, 325 hours on engine and prop. Have owned since July last year. I put on 100 hours so far.

I usually cruise around at 22" MP and 2350 RPM. This give me the 65% power and the 9.3 gph that I like. She usually runs smooth at this setting. Started doing loops and rolls lately. That's about all that has changed.

I have an iPhone mounted on the panel that I use for music. It has a feature where if it is shaken the song will skip forward to the next one. It is mounted in a rubber cradle. Usually it is fine and doesn't skip. Then a week ago I detected a vibration at my usual setting. This was confirmed by the iPhone which keeps skipping at 22" and 2350 RPM.

If I run the RPM to 2450 there is less vibration, subsequently at 2250 RPM the vibration is worst.

I have read old posts on exhaust tips needing to be turned down or manifolds that could be loose or the need for rubber floor mats etc.... I have rubber floor mats and the exhaust has been checked.

Something has changed and I don't think running the prop faster (just because it is smoother) is the solution. The engine seems fine and runs within the CHT, EGT range as it always has.

HELP.

Somethings I've been thinking about. Does the prop need greasing ? I've never had the prop balanced. Can it go out of balance ? Did the Acro do something ? Do other's have a vibration in this same region ?

This issue is bugging me and kind of taking the fun out of flying at the moment.

Thanks for any help or suggestions.

Darren

Darren S · #2 02-21-2011, 02:51 PM

more thoughts:

My alternator failed last month. The bracket was broken. Maybe the vibration issue has been going on longer than I thought and could have had a hand in the broken bracket ?

I have two Slick Mags. Run-up mag drop is about 100 RPM on one and 70 on the other. Could mag's cause rough running ?

Does what I've read about harmonics and certain Hartzell C/S props apply ? Is harmonics and vibration the same thing ?

Something is causing vibration when I dial the prop out (2250 RPM) and less at 2500 RPM. I don't think this is normal.

Thanks,

Darren

Ironflight · #3 02-21-2011, 07:25 PM

I would definitely have the prop dynamically balanced if it were me Darren - it may not fix your vibration, but it sure could - and you have to attack things one at a time. Smooth operation is better for everything, and I have been surprised how much a dynamic balance can smooth things out.

Paul

leaker311 · #4 02-21-2011, 07:39 PM

well I dont know how much I can help you with the vibration issue with my limited knowledge but to answer your question if the prop needs greasing... this is what the manual says:

hartzell owners manual page 6-5
"...propellers be lubricated after the first one to two hours of operation because centrifugal loads will pack and redistribute grease, which may result in a propeller imbalance..."
probably not the issue since you have been flying for a while now, but who knows?
additionally..
also on page 6-5
lubrication intervals:
"...must be lubricated at intervals not to exceed 100 hours or at 12 calender months..." so yeah lubrication, come annual time, is a must (well according to the manual at least)
Good luck and keep us posted.

Marco

dpansier · #5 02-21-2011, 08:27 PM

http://www.vansairforce.com/communit...ghlight=iphone

Darren S · #6 02-21-2011, 09:48 PM

I took a second flight today and found that at 21.7" MP and 2380 RPM the vibrations were much less noticeable. Even the iPhone didn't skip....at least until I hit some turbulence

I checked into the operating limitations on the Hartzell site and all it said was to avoid extended periods of running under 2250 RPM and over 2600.

I am going to take Paul's advice and check into the Dynamic Balancing. I read a bunch of posts this afternoon and the pro's seem to outweigh the con's. I'll get the hub greased at the same time.

Didn't know about the iPhone vibration app !! Cool.

Thanks for the help.

Darren

Norman CYYJ · #7 02-21-2011, 10:24 PM

Did your exhaust system shift and now causing some extra pulses in the floor?

Snowflake · #8 02-21-2011, 11:22 PM

The first time I flew with my iPhone wired into my intercom input, I found that I had one of the world's most expensive iPhone remote controls. Roll left, song skips to the next one. Roll right, song skips back.

Pretty cool, but of limited functionality.

RV7AV8R · #9 02-21-2011, 11:43 PM

Darren, I have basicly the same set up as you and have had my prop dynamically ballanced but 2350 rpm is definitely the worst for me. Some friends have said the same thing with their 360s. I run at 2400 or 2450 where it is smoother.

Darren S · #10 02-22-2011, 04:51 PM

Hey John,

Thanks for the feedback. I spoke to Hartzell today and they suggested that perhaps I should take a second look under the cowl and make sure nothing is loose and causing a vibration. They said that with an out of balance prop the vibs are worse as the RPM increases, not better. I will do so when the weather warms up.

What MP are you running ?

Thanks,

Darren