How do I figure time to log from Tach?

[rcb]

I've got a lot of flights where I have the Tach times (this is a 182) but the Hobbes is borked (shows LESS time than the Tach). So how should I log that?

I was trying to figure out how much to log with the flights below.
First number is Tech, second is time from engine start to shutdown via stopwatch.

1.8 Tach 2:00 stopwatch
.44 " :35 "
.92 " 1:15 "

and a 1.47 Tach, 1:27 t/o to taxi.

So, I figure adding .2 was probably about right? In total, I have 19.3 hours of Tach with 21.3 logged flight time. 18 flights. Adding .2 in that case doesn't seem like enough. 18*.2=3.6, wo that would give me 22.9 total logged via that formula.

On a related note, seems like I've always logged Hobbes time even though that's really not 'flight time' per the definition. (Ok, flight time is usually only slightly less than Hobbes. Say, .05 per flight but it adds up.)

Opinions? This may seem silly but I try and keep my logbook very truthfully. Which means of course my time building is taking a lot longer.

I'm loving logbook pro, it uncovered a few minor mistakes in my first logbook I just finished....

 

[ShawnC]

Hobbs is the generally accepted way to log time.

When no Hobbs is available the most accepted way to log ( and charge) is to multiply tach by 1.2

 

[katanabob]

You have to be careful about where the Hobbs came from. (or not, I guess) We have installed, removed, and replaced many a Hobbs meter in the course of everyday maintenance and annuals at our shop, and while about half are turned on and off by an oil pressure switch the rest have some pretty 'creative' methods for actuation. Some are just hotwired to the master bus, avionics bus, or alternator field lines. Some have little tabs on the outside of the airplane which turn the meter on only when a certain airspeed is exceeded. (very few of these at FBOs; they want to rape you for every cent)

 

[ShawnC]

Master Switch...

The twin at one of the FBOs around here, has the hobbs hooked up into the master switch. One creative student would turn the master on, and go on twin cross countries. It lasted a little while until a student noticed that the beacon was on, they got busted.

 

[AutoTransfer]

Another Option is to record your Engine Start and Engine Stop times on your kneeboard or whatever you use to record ATIS, clearances, and such. This gives you an exact representation of your flight time in the event of an inaccurate hobbs reading. Just a thought.

Clear Skies (or 200 and 1/2 if thats your bag, baby),
AutoTransfer

 

[TDTURBO]

Re: Master Switch...

The twin at one of the FBOs around here, has the hobbs hooked up into the master switch. One creative student would turn the master on, and go on twin cross countries. It lasted a little while until a student noticed that the beacon was on, they got busted.

I don't get it, if anything I would think he would fly with the master off and not leave it on when parked. Since the beacon light was on, the master was on and since the hobbs is wired directly to the master it would be running also.

 

[YODA]

If your question is regarding flight time, under FAR part 1.1 Flight time means: (1) Pilot time that commences when an aircraft moves under its own power for the purpose of flight and ends when the aircraft comes to rest after landing. ie. Mark the time you release brakes to roll, and mark your time you come to a stop after landing. That is your logged flight time.

 

[ShawnC]

I don't know why. He was logging time, paying for it, without flying it.

 

[tarp]

Original question:

I've seen folks use 1.2, 1.25 and 1.3 as conversion factors (tach to hobbs). You have to remember that a "tach hour" is an hour with the engine running at rated power. So, if you go out in a C-172, spend 5 minutes taxiing and running up and then go for a 3 hour X-C with the engine pushing as hard as it can, then the ratio is almost 1:1. But if you spend an hour in the rented C-172 doing pattern work and taxiing back around for a few takeoffs instead of doing touch and go's, then your ratio will soar (1.4:1).

To ShaunC:

You mean some one went out to a plane sitting on the tarmac, turned on the master switch and let the hobbs run so that they could log time without flying the time???? (And they paid for this rental time?) Where are those Darwin award people when you need them?

I've heard of students getting booted out of planes and clubs for firing them up, climbing to altitude and then "proving" that the plane's engine can run just fine with the master turned off. The hobbs would stop running and the person would do say an hour and a half of flying while paying for only an hour. Of course, the reality that you have no alternator, no transponder, no lights, no radios might be a deterent for the more sane pilots in the world.

Of course the most favorite "money saver" is the rental of the Seminole where on taxi back to the FBO, the brain surgeons decide to shut down the engine with the hobbs meter. Funny how that only gets tested once when you immediately find out how hard it is to taxi a Seminole on one engine. (Works if all the turns are in one direction, but not if you need to make turns both left and right!)

 

[TDTURBO]

Shawn,

I would not have used the term, "creative", maybe infinitely stupid but not creative. If he had half a brain, he could have just logged some pencil time or padded his hours but to pay for twin time and not fly it is beyond comprehension! Are you sure he didn't accidentally just leave the master on? If not, that has to be the dumbest thing I ever heard!