Hobbs time verses TACH time

[corjulo]

This came up on the latest podcast show from the pilotcast.com

For a club situation is it better to bill against tack time rather then hobbs time. The logic is using hobbs time encourages pilot to fly the plane as fast as possible in-order to save money. Because the rate is wet this waste fuel and is possible harder on the engine.

By billing again tach time pilot are not penalized for flying at a reduced rpm.

Any down side people can see? How is a tach hour calculated?

 

[Skip Miller]

This came up on the latest podcast show from the pilotcast.com

For a club situation is it better to bill against tack time rather then hobbs time. The logic is using hobbs time encourages pilot to fly the plane as fast as possible in-order to save money. Because the rate is wet this waste fuel and is possible harder on the engine.

By billing again tach time pilot are not penalized for flying at a reduced rpm.

Any down side people can see? How is a tach hour calculated?

The tach hour meter is essentially an engine revolution counter calibrated in hours. Just like the odometer in your car is really a driveshaft revolution counter, calibrated in miles. The tach hour meter is designed so that one tach hour will equal one clock hour at a specified RPM, which is usually somewhere in the cruise rpm range. You should be able to find the equivalency rpm in your POH, maintenance manual, or TCDS.

Your theory is good. Measured against the Hobbs meter, many rental pilots fly at full "rental power" which is wide-open throttle. Some good guys actually pull it back to 75% power but you will never see 65% in normal operations.

A (minor) downside: The hours you are billed for are not what you should put in your logbook for flight time. True, Hobbs time isn't perfectly accurate here, either, but it is a better approximation than the tach hour reading. Why? You spend a lot of time on the ground at idle and taxi rpms, recording very little tach time. Most pilots count this time as hours flown, so the tach hour meter undercounts this time significantly.

-Skip

 

[Bill]

For a club situation is it better to bill against tack time rather then hobbs time. The logic is using hobbs time encourages pilot to fly the plane as fast as possible in-order to save money. Because the rate is wet this waste fuel and is possible harder on the engine.

By billing again tach time pilot are not penalized for flying at a reduced rpm.

Our club bills by tach hour, and on our planes, I've noticed that at 2400rpm 1 tach hour is equal to one clock hour. And yes, I think this is good. If someones wants to go fast, they can, but they'll pay more than someone out for a slow Sunday flight.

Also, this is easier on students, as slow flight, pattern work, etc. usually doesn't use 75% power all of the time.

The interesing plane is the Skylane, someone running 23" and 2400rpm is going to pay more than someone running the same pressure and 2200rpm.

 

[Bill]

A (minor) downside: The hours you are billed for are not what you should put in your logbook for flight time. True, Hobbs time isn't perfectly accurate here, either, but it is a better approximation than the tach hour reading. Why? You spend a lot of time on the ground at idle and taxi rpms, recording very little tach time. Most pilots count this time as hours flown, so the tach hour meter undercounts this time significantly.

My CFI (and all of our club members, for that matter) log 1.2 times tach time. IE, tach time was 1.0, log 1.2.

 

[Richard]

For logging purposes, I use the clock. For the purpose of flight....

 

[ScottM]

I use the Hobbs for my pilot log and the tach for all the maintenance stuff.

 

[Tim]

I use local time

 

[TMetzinger]

I tend to run WOT any time I'm at 6000 or more, since the normally aspirated engines I'm usually behind won't make much more than 75-80% at that altitude.

And remember the engine TBO is based on 100% power, not 75% power. I'm not convinced that running the engine at higher power settings appreciably shortens it's life.

That said, in training or local flying tach time is usually much less than hobbs, and that's nice. I don't mind paying "full" price when I'm going from point A to B - the whole purpose of those flights is to get there safely and quickly.

 

[Laurie]

This came up on the latest podcast show from the pilotcast.com

For a club situation is it better to bill against tack time rather then hobbs time. The logic is using hobbs time encourages pilot to fly the plane as fast as possible in-order to save money. Because the rate is wet this waste fuel and is possible harder on the engine.

By billing again tach time pilot are not penalized for flying at a reduced rpm.

Any down side people can see? How is a tach hour calculated?

I don't know if I see a down side necessarily, but I really find it hard to believe that there are club pilots out there running their engines at redline to save $5 or $10 on their rental cost. I'm not sure what kind of plane you're talking about, but I can tell you on a C-172 the difference between running the engine at redline 2700 RPM and pulling it back to 2300 RPM is about 2, maybe at most 3 knots. All the extra power does is burn more gas, make more noise and doesn't produce any appreciable speed difference. Maybe I'm an optimist or whatever, but I think that most clubs, where the pilots are part-owner of the plane, are more interested in taking care of their aircraft and getting the best compromise on speed/fuel burn. You may not be paying for the gas directly on a wet rental, but it is a factor of the rental price - if the fuel costs are skyrocketing rental price will follow. So, I really don't see an advantage one way or the other for recording flight time strictly by hobbs or tach for the purposes of billing.

 

[poadeleted20]

My CFI (and all of our club members, for that matter) log 1.2 times tach time. IE, tach time was 1.0, log 1.2.

Don't let the FAA find out, because that is not an FAA-accepted way of logging flight time in a pilot logbook. If you don't have a Hobbs meter (which they do accept), you should note the times you pull out of and stop back in the chocks, as that's the legally correct way to log the time in a pilot logbook.

 

[Skip Miller]

I don't know if I see a down side necessarily, but I really find it hard to believe that there are club pilots out there running their engines at redline to save $5 or $10 on their rental cost.

Laurie, there is a big difference between a club pilot and a straight rent-it-from-the-FBO pilot. That shouldn't be true, but it is...

-Skip

 

[Areeda]

Our club rents by tach time and I'm all for it as a renter and a board member. I agree with the flight planning options being much closer to how an owner plans compared to a renter.

As an instructor it is nice that a full stop taxi back costs only a little more than a touch an go. Significant time waiting for clearances doesn't hurt anywhere near as much.

Bill's point about the 182 is right on, I tell new pilots to look in the POH and choose the lowest RPM appropriate to the power setting (% power not MP) it's quieter, same speed and cheaper.

There is no one factor to align hobbs and tach time because it depends on the flight regimen. A day of full stop taxi back it can be a factor of 2 and a long cross country at high power it can be 0.95.

One last point is the club expenses are more closely aligned with tach time than hobbs time.

Joe

OK one more last point:

I don't know if I see a down side necessarily, but I really find it hard to believe that there are club pilots out there running their engines at redline to save $5 or $10 on their rental cost.

The redline part is probably a bit much but top of the green is within the flight plan for maximum efficiency goal which I think we all do. The definition of efficiency for most of our flights is the lowest long term cost, sometimes speed is more important than cost but not often. If we price the planes so that maximum speed gives us minimum cost I believe most people will flight plan that way.

 

[flyingcheesehead]

The interesing plane is the Skylane, someone running 23" and 2400rpm is going to pay more than someone running the same pressure and 2200rpm.

In our club 182, I use WOT until I'm descending. WOT/full RPM for takeoff, back to WOT/2500 for climb, WOT/2200 for cruise which is usually up in the 7 or 8,000 foot area. If the MP is to be believed, I'm only getting 20-21" at those altitudes anyway.

My CFI (and all of our club members, for that matter) log 1.2 times tach time. IE, tach time was 1.0, log 1.2.

You're gypping yourself. My average ratio in the Archers last year was 1.358. If I did the simple 1.2 * tach, I would have eight fewer hours in my logbook. (50.96 tach hours in our Archers, logged off the clock at 69.2 hours.)

VFR cross country flights have the lowest ratio due to high average power setting (and less time spent at lower approach settings). My ratio on VFR XC's was 1.194. On the other end of the spectrum, flights with lots of pattern work or approaches can end up in the 1.4-1.5 range.

Of course, YRMV - But I'd encourage you to hit the clock at startup and shutdown and see how much time you're missing.

 

[AirBaker]

VFR cross country flights have the lowest ratio due to high average power setting (and less time spent at lower approach settings). My ratio on VFR XC's was 1.194. On the other end of the spectrum, flights with lots of pattern work or approaches can end up in the 1.4-1.5 range.

I'd just definte it to 'cross country' flights and not just VFR.

"You get what you measure." Depending on the altitude, aircraft, etc., you could end up with a renter flying at a high MP and very low RPM to save a few bucks.

 

[flyingcheesehead]

I'd just definte it to 'cross country' flights and not just VFR.

If you go on a <100nm XC flight IFR and you actually fly an approach, the ratio does go down somewhat. Maybe .05, but still. I've had flights where I've spent the vast majority of the flight at 90 knots flying approaches and had ratios around 1.45 Hobbs/1 tach.

"You get what you measure." Depending on the altitude, aircraft, etc., you could end up with a renter flying at a high MP and very low RPM to save a few bucks.

IMHO, most club pilots are a bit nicer to the planes than that, because they do own a small part of them and are directly affected when they're down a lot. (Note: I am talking about real clubs here, not those "FBO clubs".)

 

[Bill]

Don't let the FAA find out, because that is not an FAA-accepted way of logging flight time in a pilot logbook.

Learn something new every day (subtitled: Stupid CFI).

you should note the times you pull out of and stop back in the chocks, as that's the legally correct way to log the time in a pilot logbook.

Now that I think about it, thats exactly how the hours in my logbook have been figured.

 

[Bill]

In our club 182, I use WOT until I'm descending. WOT/full RPM for takeoff, back to WOT/2500 for climb, WOT/2200 for cruise which is usually up in the 7 or 8,000 foot area. If the MP is to be believed, I'm only getting 20-21" at those altitudes anyway.

Interesting. We were taught WOT and full prop on initial takeoff and climb, then once at a comfortable altitude (2000agl-ish), pull back to 23" and full prob for the remainder of the climb. (23" is the top of the green arc on the pressure gauge)

I maintain 23" during the climb, and as you climb, you're eventually back at WOT and then the pressure starts to fall off. Then at cruise, prob back to 2300. I prefer 9k east and 10k west in the Skylane.

This is a 2002 182T where full prop redline is 2400rpm anyway.

 

[flyingcheesehead]

This is a 2002 182T where full prop redline is 2400rpm anyway.

Ah... Ours is a 1971, full prop is 2600 RPM which is kind of noisy. Pull back after takeoff is to be neighborly.

I'm sure a few other things changed in the 30+ years between 'em too...

 

[Greg Bockelman]

Don't let the FAA find out, because that is not an FAA-accepted way of logging flight time in a pilot logbook. If you don't have a Hobbs meter (which they do accept), you should note the times you pull out of and stop back in the chocks, as that's the legally correct way to log the time in a pilot logbook.

How are the Feds going to find out one way or the other? And after you have the requirements for all the ratings you are going to get, what difference does it make anyway?

 

[jason]

How are the Feds going to find out one way or the other? And after you have the requirements for all the ratings you are going to get, what difference does it make anyway?

It's against the FARs to falsify your logs. If you don't want to log it, you don't have to. But if you are logging it you have to do it in an approved manner.

That said, I agree with the fact that they'll never know or care one way or the other.

 

[Greg Bockelman]

As far as I am concerned I am NOT falsifying my logs. I flew the time, I have history that on average, tach = 1.2 hobbs. That is what I use. More often than not I forget to hack the clock both before and after a flight. I thinks a REASONABLE Fed would accept that. Of course Reasonable Fed may be an OXYMORON.

 

[poadeleted20]

As far as I am concerned I am NOT falsifying my logs. I flew the time, I have history that on average, tach = 1.2 hobbs. That is what I use. More often than not I forget to hack the clock both before and after a flight. I thinks a REASONABLE Fed would accept that. Of course Reasonable Fed may be an OXYMORON.

I think the latter part sums it up. If the Feds find out, they will not be happy, so either find a legally-acceptable way to do it or don't continue to tell anyone what you're doing.

 

[Greg Bockelman]

Don't let the FAA find out, because that is not an FAA-accepted way of logging flight time in a pilot logbook. If you don't have a Hobbs meter (which they do accept), you should note the times you pull out of and stop back in the chocks, as that's the legally correct way to log the time in a pilot logbook.

Ron, point me to the reference that explains what the FAA accepted method of figuring flight time is.

 

[TMetzinger]

Ron, point me to the reference that explains what the FAA accepted method of figuring flight time is.

Part 1 - " Flight Time means:
(1) Pilot time that commences when an aircraft moves under its own power for purpose of flight and ends when the aircraft comes to rest after landing."

Hobbs time is commonly accepted since the airplane normally moves shortly after engine start and the engine stops shortly after the airplane comes to rest.

Tach time is continuously variable and that's probably why an FAA type who is predisposed to "get you" for something could make a case against it.

 

[RotaryWingBob]

There's an interesting twist to all of that in helicopters. Some, like our R22, have a hobbs that runs as long as there's oil pressure. On the R44 Raven II (and many turbines), the hobbs doesn't start running until you pull pitch, and stops when the collective is fully lowered. This means that if you're practicing autorotations, you don't get credit for that time. Some helicopters have two hobbs meters, one for maintenance, one for pilot logging...

 

[Greg Bockelman]

Part 1 - " Flight Time means:
(1) Pilot time that commences when an aircraft moves under its own power for purpose of flight and ends when the aircraft comes to rest after landing."

Hobbs time is commonly accepted since the airplane normally moves shortly after engine start and the engine stops shortly after the airplane comes to rest.

Tach time is continuously variable and that's probably why an FAA type who is predisposed to "get you" for something could make a case against it.

I accept the part 1 Definition of Flight Time. What I want is reference to what the FAA considers acceptable as far as recording flight time.

 

[poadeleted20]

I accept the part 1 Definition of Flight Time. What I want is reference to what the FAA considers acceptable as far as recording flight time.

They haven't published one, but they have always accepted Hobbs time as recorded. OTOH, they have never to my knowledge knowingly accepted a multiple of tach time, and the mechanics of the system would make it very hard to justify as an accurate reflection of "flight time" as defined in the rule.

 

[Stache]

I don't think the FED's are out to get anyone, just the bad guy screwing it up for everyone else. As long as you log you time correctly for the rating you hold there is nothing to worry about.

Just one man's opinion.

Stache

 

[poadeleted20]

I don't think the FED's are out to get anyone, just the bad guy screwing it up for everyone else. As long as you log you time correctly for the rating you hold there is nothing to worry about.

Well, Stache, that's really the question being asked, isn't it? Is logging 1.2 times tach time as your total flight time considered "log[ing] you[r] time correctly"? I don't think your colleagues on the Operations side of the FSDO house would say it is.

 

[RogerT]

If you don't have a Hobbs meter (which they do accept), you should note the times you pull out of and stop back in the chocks, as that's the legally correct way to log the time in a pilot logbook.

I don't see where a Hobbs meter is any more accurate. Just having the
engine running doesn't mean the aircraft has moved for flight yet.

 

[poadeleted20]

I don't see where a Hobbs meter is any more accurate. Just having the engine running doesn't mean the aircraft has moved for flight yet.

While that is true, the FAA accepts Hobbs-based time for pilot logging purposes, and they do not accept any tach-multiple for that purpose.

 

[jesse]

and they do not accept any tach-multiple for that purpose.

Seems to me that you have yet to produce anything that says such.

 

[RogerT]

While that is true, the FAA accepts Hobbs-based time for pilot logging purposes, and they do not accept any tach-multiple for that purpose.

What about Tach x 1.0? That invalid too?

This all seems a little irrelevant for someone who's not building
time for anything and only logging requirement is enough
landings in the last 90 days to be current or enough approaches,
tracking, holding to be ifr current.

Isn't flying supposed to be fun and not overly anal?

RT

 

[poadeleted20]

Seems to me that you have yet to produce anything that says such.

Seems to me that nobody has produced anything that says they will accept it, and there's plenty of regulatory matter (starting with the definition of flight time in 14 CFR 1.1) to the contrary. If you don't believe me, fine, use it, but don't say I didn't tell you so if the FAA rags on you later for doing it that way. And don't expect me to sign a practical test endorsement for you if you tell me that's how your time is logged and there's an aeronautical experience requirement for that ticket which you just barely meet.

 

[jesse]

And don't expect me to sign a practical test endorsement for you if you tell me that's how your time is logged and there's an aeronautical experience requirement for that ticket which you just barely meet.

Shouldn't be a problem.

 

[Stache]

This is one man’s opinion and I may be wrong.

The methods of recording and tracking time is very important for the rating pilots hold reference FAR 61.51 and AC 61-98 Currency and additional qualification requirements for certified pilots.

CFI’s and the FAA review the pilot's logbook to determine total flight time and type and recency of experience. So here is the problem as I see it. If you use Tach time and the 1.2 hours per 1-hour flight time it is a (estimate) not true and accurate time. Using the Hobbs is closer to true time and using a clock is more accurate.

Where I work we would prefer to see clock time, as it is the most accurate, however Hobbs time is acceptable. Please remember your pilot logbooks are offical records and in most logbooks there is a statement about being true and accurate where the pilot signs their name. If you are using Tach time and estimating 1.2 to mean 1-hour it may not be true and accurate statement, but an estimate of time depending on the peculiar aircraft. Estimating time is not an acceptable method of accounting for flight time.

Here is the reference for the rule about logbooks:

FAR 61.51 Pilot logbooks.
(a) Training time and aeronautical experience. Each person must document and record the following time in a manner acceptable to the Administrator:
(b) Logbook entries. For the purposes of meeting the requirements of paragraph (a) of this section, each person must enter the following information for each flight or lesson logged:
(1) General-
(i) Date.
(ii) Total flight time or lesson time. (NOTE: total flight time)
(iii) Location where the aircraft departed and arrived, or for lessons in a flight simulator or flight training device, the location where the lesson occurred.
(iv) Type and identification of aircraft, flight simulator, or flight training device, as appropriate.
(v) The name of a safety pilot, if required by §91.109(b) of this chapter.

I will say this much estimating time is not an acceptable method to the Administrator such as converting 1.2-tach hours to 1-hour flight time.

FAR 1.1 states; 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; (Block to Block).

So question is what is the preferred method to track time? I would say clock time then Hobbs time.

Stache

 

[RogerT]

I had a discussion about this with a FSDO friend and he shed some light
on it I wasn't aware of. He said the 1.2 thing was originally a way for
military pilots transitioning to the airlines to convert their flight time.
It wasn't meant for anything else. I don't know anything about military
logging .. maybe Ron would have some input.

He also said the best way is by the clock, block to block, which
is what he does.

RT

 

[poadeleted20]

I had a discussion about this with a FSDO friend and he shed some light on it I wasn't aware of. He said the 1.2 thing was originally a way for military pilots transitioning to the airlines to convert their flight time. It wasn't meant for anything else. I don't know anything about military logging .. maybe Ron would have some input.

The military logs flight time from takeoff to touchdown, not chock to chock as defined in the FAR's. Unless they keep a personal log, military flyers don't have any "official" record of the extra "flight time" they merit for FAA purposes above and beyond what's in their military records. Some airlines allow the aforesaid multiplier when considering applicants' military times for hiring purposes, but it's not an official FAA thing for Part 61 purposes.