Left the master on...

How to keep the Cessna 170 flying and airworthy.

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Ryan Smith
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Joined: Tue Nov 25, 2008 4:26 am

Re: Left the master on...

Post by Ryan Smith »

wabuchanan wrote:This is one of the things I just love about the piano switches.

As long as they all line up, the Master is off.

Sorry to hear about yours being left on Doug :? :|
Except when the grommets have rotted away. That happened to me twice before.

In the airline world, the nav lights stay on all the time, so I have adapted that practice for GA. It saved the the other say when I was distracted getting out of the airplane and the very bright LEDs caught my attention.

Also, most Hobbs meters are plumbed such that oil pressure is required in addition to DC power as a stopgap for this. Dad’s Bonanza had a Hobbs meter installed that was only wired for electrical power from the main buss, so when did some panel work recently I ditched it. Unless the airplane is being used for hire, I see no need for a Hobbs meter, personally.
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Karl Towle
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Re: Left the master on...

Post by Karl Towle »

I will insert this idea here and we can see where it goes. I've had a Horizon P-1000 tach installed for years. Being an electronic tach, its tach time was accurate, and only ran with the engine - like a Hobbs. Anyway, twice it simply forgot its tach time, and had to be sent in to be reset. The final straw was when it started simply shutting off in flight. Something had to be done. However, without going for the whole enchilada and installing a flat panel display, there wasn't much else available. Along the way, I discovered that there wasn't a TSO for tachometers in existence in 1954 when my 170B was "born." So, after a discussion with my friendly IA, we installed a MGL Avionics Blaze RPM-2 instrument in the panel. It is not TSO'd, but works GREAT. The installer can initialize the tach time to equal the SMOH or mainframe time, or anything else for that matter. It has a number of other great features, including a flight timer. And, of course, the tach time accurately accrues when the engine is running - just like a Hobbs.
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Ryan Smith
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Re: Left the master on...

Post by Ryan Smith »

I just shelled out $400 for a new battery that I roached by leaving the master switch on twice. The rubber grommet on that switch had dry rotted and fallen out, probably even before my grandfather bought the airplane in 1986, and I finally had enough. It hasn’t happened since I restored the piano key assembly, but the damage was already done.

In the 121 world, we leave navs on 100% of the time. It’s our indication that the airplane is powered up, and the beacon comes on engine start. Now I leave my navs on all the time, especially since they’re LED, they’re super bright and hard to miss and don’t draw any power. When I re-wired Dad’s Bonanza, I didn’t even put the navs back on the piano key, instead I put it on a circuit breaker switch on the auxiliary circuit breaker panel. This necessitated putting resistors on a separate dimming circuit switch for the indicator lights, but is well worth the effort. When I get around to putting Whelen Orions on the 170, I’ll do the same and leave the nav light switch out of the piano keys.

To answer your question about the Hobbs, unless the airplane is being used for commercial operations, they’re useless. Most of them require oil pressure and battery power to turn over, but the one in the Bonanza used battery power only. It got yanked with the re-wire. Your Hobbs can be useful for actual engine run time for oil changes since a recording tach is only accurate at its normal operating RPM. If you’re somewhere where you’re at idle a lot, you may end up running your engine longer than your tach says.
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GAHorn
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Re: Left the master on...

Post by GAHorn »

Engines experience less wear at lower RPMs such as at idle…so I don’t worry about the fact that a recording tachometer runs a bit slower than “real time” at idle…..this is commensurate with the need for oil changes….. and who actually changes oil “on the dot” at whatever change interval selected..??

Some hour meters operate by relative wind switches. Some activate with engine vibration. The ones which are hardwired and activate with Master Switches are the ones I especially dislike because they are indicating higher time on the engine than actual operation.

This is nothing too different than logging pilot time at “push-back”… or logging PIC time at 100% flight time and 50% taxi time…. or similar methods of micrometer/grease-pencil/hatchet operations. IMO.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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