AMURRAY

AMURRAY

Well Known Member
Most of the airplanes I have flown have the hobbs meter connected to the squat switch which wouldn't run the hobbs until the weight is off the wheels. Well you don't have that choice with RVs. I know Vans method is to connect the hobbs to an oil pressure switch. Then the hobbs is turning as soon as you start. I know another way is to use a mechanical tach that turns the timer slower at idle I.E. Tach time. Most people are not using mechanical tachs anymore. I used to fly a Dutches that used a pitot pressure switch instead of a squat switch. The switch would close at something like 30 knots. One of my thoughts is to use one of these pitot switches hooked up to a hobbs. Some people have two hobbs, at least some of the trainers I flew, tach and TT. That way they could maintain the airplane per the slower running tach and charge you per the TT which was connected to the master. Any thoughts.

Thanks,
Aaron
 
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Oil Pressure

I use the oil pressure switch. It will end up showing more time on the plane and engine than if connected to the tach. Since I have the Repairman Certificate I can decide when to do the maintanence and therefore I adjust the oil change etc to corrispond to using the oil pressure instead. Down side is when (if I ever do) sell the plane it will appear to have more hours than if I used the tach.
 
Tach for engine time?
Oil Pressure driven HOBBS for Pilot in Command Time?
Coin toss for airframe time method - unless rules say otherwise.
Jim Sharkey
 
Try EI

Aaron:

You might consider an EI (Electronics International) RPM gauge. It is electronic and will record tach time. I don't use mine for that purpose (I use the Hobbs gauge) but I think it won't start recording until you've exceeded a certain RPM, i.e., cruise power settings. You might want to look at EI's website and investigate.

I figure I'm not going be around long enough to reach 2,000 hours on my Hobbs so I'm not sweating the difference. You are right, however, that the difference can be substantial especially if you fly out of a busy airport like I do at Addison, TX. It is not unusual for me to see .3 or .4 on the Hobbs just waiting for takeoff at ADS.

Chris
 
I put an EI in my RV-4. It starts recording time when RPM exceeds 1300 or so. If your at idle a lot, like in the pattern, it ads no time. On the flip side, it records time like a clock. (as opposed to mechanical tachs that record slower for slower engine speeds.) They preset it to my engines time at the factory, so no adding two numbers to get the total. Has a bunch of other features, but I'll not bore you with them. Allowed me to close up a firewall hole too. ;-)
Good luck
 
I could be wrong....

jsharkey said:
Tach for engine time?
Oil Pressure driven HOBBS for Pilot in Command Time?
Coin toss for airframe time method - unless rules say otherwise.
Jim Sharkey
Click to expand...

I think the regs call for logging time on airframe and engine to be airborne time, i.e.: Liftoff to Touchdown.

As always, I am standing by to be corrected!;)
 
Well....

I'm told by a long time Corporate Pilot the rules say "block to block" which isn't recordable by any instrument other than the fancy watches they sell to pilots that can afford them! :eek:
Am using oil pressure Hobbs for all. I fire up and am rolling within 60 seconds. Seems reasonable for engine records and flight time? Am sure open to a better idea! :confused:
 
Hobbs vs others

PCHunt said:
I think the regs call for logging time on airframe and engine to be airborne time, i.e.: Liftoff to Touchdown.
Click to expand...

I was always taught to log PIC time from when the engine started to when it stopped (hopefully parked at that point). So Hobbs is good for this. And it makes sense since the PIC is responsible for anything that happens when the engine is running. How this relates to engine time, however, is debatable and makes for an interesting discussion considering the low demands of taxiing and idle versus takeoff and cruise. I have no idea what the right answer is to this, but would be curious if Lycoming, et al address the subject.

Chris
 
chrispratt said:
I was always taught to log PIC time from when the engine started to when it stopped (hopefully parked at that point). So Hobbs is good for this. And it makes sense since the PIC is responsible for anything that happens when the engine is running. How this relates to engine time, however, is debatable and makes for an interesting discussion considering the low demands of taxiing and idle versus takeoff and cruise. I have no idea what the right answer is to this, but would be curious if Lycoming, et al address the subject.
Click to expand...

And since you're paying for fuel, it at least makes your personal logged time, "more accountable" as well.

First 10 hours for insurance purposes? The 25 to 40 hour flyoff before passengers? Hobbs on oil pressure is the way to go.

L.Adamson
 
Time?

kinda splitting hairs..... but my $.02 .........
I use Tach time for oil changes, I change my oil on 100, hrs 150 hrs, 200 hrs, on the RV 8. It has an oil filter. The Super Cub does not have a filter and it gets changed every 25 hrs, ie 100, 125, 150, 325, hrs.
I think a hobbs is great if you are charging rent. I own my own airplanes and do not rent them out. I think buying a piece of equipment ie, hobbs meter for my use would be a waste of $$
For my log book entries I use the Garmin 396 flight log. Quit using / wearing a watch when I got a cell phone.
 
RVadmirer said:
I'm told by a long time Corporate Pilot the rules say "block to block" which isn't recordable by any instrument other than the fancy watches they sell to pilots that can afford them! :eek:

The reality is pilot time is recorded block to block but not aircraft time. Large turbine aircraft (with the exception of some smaller Citations) don't have hobbs etc. and the time and cycles (landings) are recorded by the crew.

Engines and airframe times are takeoff to touchdown or actual flight time. Aircraft and engine cycles can be the same as landings, or you have the option of recording each engine start and stop as a cycle for that engine, but very few people do. What this means is all the maintenance runs we do on the pad are not recorded for their hours or cycles - perfectly acceptable by the manufacturers and feds. APU's generally have a hobbs meter and some also meters to record starts (cycles).

Also as a point of interest, most professional pilots I deal with wear standard old watches like everyone else. Guys of my generation can't read those little bitty numbers on "pilot watches" anyway. That's what airplane clocks are for.:D

Don
Click to expand...
 
I just log whatever the AFS Engine monitor records - it records anything over zero RPM as Hobbs time and anything over 1250 RPM is tach time. At this point that creates a difference of 220 Tach vs. 260 Hobbs.

I count Tach time towards oil changes etc and Hobbs time for my pilot log.
 
It's in AC 43-9C.... Time In Service

PCHunt said:
I think the regs call for logging time on airframe and engine to be airborne time, i.e.: Liftoff to Touchdown.

As always, I am standing by to be corrected!;)
Click to expand...

Pete... you are correct, the regs. do call for actual flight time.... however most pilots I know use tach or hobbs time.

In the case of experimentals, where time in service is less critical, it does not make much difference, but for certified aircraft, hobbs time certainly does rack up the hours faster, and hobbs time might...

The requirements are actually in AC 43-9C...

Part 1, section 1.1, Definitions, defines time in service, with respect to maintenance time records, as that time from the moment an aircraft leaves the surface of the earth until it touches down leaves the surface of the earth until it touches down at the next point of landing.

NOTE - this is for airframe/engine stuff only, not pilot's logs...

gil A

...recently came up in a discussion with my IA, who does actually manually record flight time... Some GPS units will do this per flight, but some loose the record on power down... like my Apollo....:(
 
Depends on the instrument you are using

Aaron, one thing I don't think anyone has pointed out yet is with all the glass engine monitors available to us in the experimental world, it is going to depend a lot on what you use in your airplane. I am using the Dynon engine monitor. It records both hobbs time off oil pressure and tach time off one mag. Take your pick. I'll record hobbs..........although in my Bonanza I recorded off the tach.......just 'cause it didn't have a hobbs;)
 
I was advised quite some time ago by someone at Lycoming that tach time is engine time. If you purchased a new engine with factory warranty then you should use tach time for the engine. TBO and warranty on engine is based on 2000 hours tach time. This can be 20-30% less time than what a hobbs meter will show. This also goes for oil changes and any AD'S or time in service on mags or any other engine accessory.
 
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Tach Time at 75%

I was told that Hobbs was 15-20% greater than tach. Also, the mechanical tach records true hours at 75% power (2350-2400rpm). It runs a little faster at full power and slower at lower power settings.
That said, if you use Hobbs for your engine time, you should easily get 2300-2400 hours before TBO.
 
I use the times recorded by my garmin 496 for flight time. If there is a long taxi then I might add 0.1 or so. The flight log in the garmin starts ticking when you are a certain speed and altitude over where you were when the unit started.
 
tach time and Hobbs

FWIW....I use both, mechanical tach which I use to record flight time. the hobbs gets read and recorded when I do the annual. Personally next time I won't even bother with the hobbs....my $.02
 
When I learded to fly (off a grass strip) we figured the hobbs showed 15-20% more time than the tach. Here at Sarasota (SRQ) the builders who have both hobbs and tach are showing around 25% higher on the hobbs. This is due to longer taxi and hold time for jets. So it depends where you are located at what the difference will be . On long cross countries the time shown is closer together.
 
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