Tach Time v. Foreflight Logbook Time

SoCal 182 Driver

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SoCal 182 Driver
Friends - Over the last couple of days, I took three flights. My Foreflight logbook recorded almost an hour more time than the plane's tach. (4.7 hours v. 3.8 hours). Can anyone explain why there is such a significant difference?

Thanks.
 
What kind of flying was it? Pattern work or going somewhere? ForeFlight either records movement time or projected time, while tach only count full speed at high rpm.
 
Foreflight measures time you're moving faster than some threshold.
Tach time counts engine revolutions and divides by some nominal RPM to compute the time.

Pilot time is neither of these. Pilot time is the time from which the plane first moves under its own power for the purpose of flight until it comes to rest. The FAA (almost always) takes any reasonable approximation of the time... hobbs, tach time, tach time with a correction factor, facebook time, etc... as acceptable. I know only one enforcement action when the FAA was so hell-bent at ramming an action through that they thought otherwise (which was completely stupid anyhow, because the parties involved certainly committed violations in other ways).

Time in service (for maintenance) is the time the airplane is off the ground. Unless you have a hobbs on a squat switch (which I did for a while), the tach time, hobbs time, or even engine above idle time is often used.
 
What kind of flying was it? Pattern work or going somewhere? ForeFlight either records movement time or projected time, while tach only count full speed at high rpm.

Flight #1: KCMA to KUDD. Pretty much straight and level most of the way, with nominal taxiing at KCMA and a long taxi at KUDD.
Flight #2: KUDD to KMYF. Lots of moving around to avoid clouds and terrain. Normal taxiing times (a few minutes).
Flight #3: KMYF to KCMA. For the most part straight and level, but some altitude and power adjustments to avoid clouds. Normal taxiing times (a few minutes).
 
Pretty much why I wouldn’t rely on ForeFlight to keep track of my hours.

Note Hobbs time before / Note Hobbs time after ... Done!
 
Hobbs.. or a simple watch / stopwatch

The Foreflight tracking is trash. Sometimes it won't log a flight at all, other times it records a 200 hr flight with me driving all over San Diego with it in my trunk
 
Often the Foreflight tracklog continues recording well after the engine is shut down. It shows my path of walking from the airplane to the hangar door, pushing the airplane into the hangar, wiping bugs off the wings, etc., etc. Very entertaining.
 
My Foreflight logbook recorded almost an hour more time than the plane's tach. (4.7 hours v. 3.8 hours). Can anyone explain why there is such a significant difference?
Hours on the tachometer are roughly analogous to the odometer in a car. It merely counts the number of times the prop spun and normalizes the number against a certain RPM. If you pulled back on the blue knob then it will go slower than real time. And as others have said, Foreflight tracking does have issues.

Often the Foreflight tracklog continues recording well after the engine is shut down. It shows my path of walking from the airplane to the hangar door, pushing the airplane into the hangar, wiping bugs off the wings, etc., etc. Very entertaining.
Maybe it was a super strong headwind. :)
 
EFBs and GPS units typically record time in motion greater than some speed, e.g. 30 kt. So you won't capture taxi time or part of the takeoff and landing rolls.

Tach time is based on an rpm value for which the tach was calibrated, e.g. 2300 rpm. If you fly at higher rpms, you rack up more "time", if you fly at lower rpms, you register less "time."

Hobbs meters start timing when oil pressure comes up, or at engine start.

Hobbs or a watch would give the most accurate measure of loggable time.
 
Pretty much why I wouldn’t rely on ForeFlight to keep track of my hours.

Note Hobbs time before / Note Hobbs time after ... Done!

I don't have a Hobbs. Only a tach.
 
Often the Foreflight tracklog continues recording well after the engine is shut down. It shows my path of walking from the airplane to the hangar door, pushing the airplane into the hangar, wiping bugs off the wings, etc., etc. Very entertaining.
I have had it include 40 minutes of driving and errands in and out of stores.
 
Friends - Over the last couple of days, I took three flights. My Foreflight logbook recorded almost an hour more time than the plane's tach. (4.7 hours v. 3.8 hours). Can anyone explain why there is such a significant difference?

Thanks.
I have the same issue. After I pull out the plane, I turn on FF and my GDL51 so it can be ready before I go. At the end of the flight when I click on "info" in the track log, I can see its been logging from the time I turned it on. I have to adjust the times. When I put in the Hobbs and Tach numbers, that usually solves it.

You can see exactly what its logging if you go into the track log and then select "info".
 
If you are logging tach time, you are shorting yourself.

Big time

Log prop start to stop in your logs

Mx is done on tach

Lots of rental places bill off hobbs

Personally I use ForeFlight for logging, though I don’t use the automatic function, I hit the record button when I start the engine for flight, hit it again after I shut the engine down.
 
Look at your watch when you start the engine and look at your watch when you stop the engine. Pretty simple.
As stated tach time shorts you. It does not count correctly at low RPM's.
 
If you forget to check the time then the usual convention is tach times 1.2 or so I am told and I have found this to be mostly correct for flying from here to there. However, do a bunch of taxiing, pattern work or slow flight and tach time could be significantly less.
 
You should not use either for your logbook flight time. Either use an elapsed timer of some sort starting the timer after run up and stopping it after clearing the runway or write down those times as read from a clock. The tach will be close to that if it’s a straight flight with climbout and descent with no maneuvers. The Foreflight time will most always be over because it begins upon taxi and ends upon stopping back in front of the hangar or wherever you taxi to after the flight.

An elapsed timer is ALWAYS a worthwhile member of the panel.
 
Friends - Over the last couple of days, I took three flights. My Foreflight logbook recorded almost an hour more time than the plane's tach. (4.7 hours v. 3.8 hours). Can anyone explain why there is such a significant difference?

That actually sounds about right. Your times above are perfectly plausible for tach vs. actual. I know that some people will log tach * 1.2 or 1.3 (not a practice I recommend, since there's nothing the FAA says that you can use to defend that practice should you be called out for it). Your 3.8 hours * 1.236 would give you 4.7...

I also have noted that most flights, I have an average of 0.3 hours of loggable non-flight time. 0.3 hours * 3 flights is exactly the 0.9 difference you're seeing.

Depending on what kind of tach you have, the tach will act in one of these ways:

1) Mechanical tach: Generally counts as a percentage of max or cruise RPM - Let's say 2400 RPM. If you're flying along at 2400 RPM for 6 minutes, you'll get 0.1 hours on the tach, while if you're on the ground idling at 800 RPM, you'll need to do that for 18 minutes before you rack up 0.1.
2) Electronic tach: Generally counts 1:1 above a certain RPM, and not at all below. IIRC, EI's threshold is 1300 RPM while Horizon's is 800. Any time spent above that RPM will give you 0.1 for every six minutes, while any time below that RPM will count as 0.
3) Garmin "tach": Generally, the various Garmin gear starts counting once you hit 30 knots. If it's only a GPS that'll be groundspeed, whereas I believe that an EFIS such as the G1000 will use airspeed.

I'm not sure of ForeFlight's exact algorithm since it's been out for a long time, but IIRC when they detect a takeoff, they'll go back to when you were at rest and count from then. So, for example, it'll go back through your taxi time to when you were on the ramp or at the hangars and at rest, and mark that as the start of the recording. Next time you go flying, have someone watch the timer on the track log recording button on your Maps page - Once it starts recording, it'll instantly have 10-15 minutes on it (the time you spent taxiing). Since the FAA's definition of flight time starts "when the aircraft first moves under its own power for the purpose of flight" that's what ForeFlight is capturing.

I have noticed that their end-of-flight auto-stop is not quite as good, especially if I'm in a hurry - If I taxi up, jump out the door, run into the hangar to grab the towbar, push the plane in quickly, run to the car and leave the airport (ie, I never really stop moving at all) sometimes it'll capture my entire drive home. So, to ensure it hasn't done this, go to More -> Track Logs and choose one of the flights in question. Look at the altitude/speed graphs, zoom in on your destination airport, and move the little slider to that point and hit play if you so choose. If you see yourself taxiing up to the ramp and the recording stops, you're all good. If you see yourself walking around, going to your car, etc then take a look at when you first pulled up to your parking spot, note the time on the slider at the bottom and put that in as the ending time on your logbook entry.

The Foreflight tracking is trash. Sometimes it won't log a flight at all, other times it records a 200 hr flight with me driving all over San Diego with it in my trunk

It has improved significantly over time, FWIW.

An elapsed timer is ALWAYS a worthwhile member of the panel.

And it's already part of many panels, whether you know it or not. Most Garmin transponders have both flight and elapsed time functions, that's what I use myself - But even a lot of the older King avionics have an elapsed time function, if you just RTFM to find it.
 
I log all time I spent on POA

I should log about .3 Hobbs reading this





Dear FAA - I am kidding
 
The software I use, in conjunction with an android GPS logger, pauses logging any time the speed is less than 5 mph, and displays each individual segment, with the start/end location (airport ID or GPS coords if not an airport). Easy to see which is the flight and which is the stop at the restaurant if I forget.

It's actually a program I wrote myself and am developing, with an eye toward maybe releasing for public consumption once I'm happy with it.
 
You should not use either for your logbook flight time. Either use an elapsed timer of some sort starting the timer after run up and stopping it after clearing the runway or write down those times as read from a clock. The tach will be close to that if it’s a straight flight with climbout and descent with no maneuvers. The Foreflight time will most always be over because it begins upon taxi and ends upon stopping back in front of the hangar or wherever you taxi to after the flight.

An elapsed timer is ALWAYS a worthwhile member of the panel.

You are shorting yourself loggable time. Taxi time with the intent to fly is fine to log.

For Reference 14 CFR 1.1 defines flight time as:

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; or
 
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For the purpose of flight is rolling forward on the runway.

Ever fly a tailwheel airplane? On windy day? Better be flying it from the time the wheels move till they stop.

Obviously you have if you own a 140. ;)
 
For the purpose of flight is rolling forward on the runway.
The FAA doesn't hold that view. Taxi time is included in pilot time. The FAA holds that moving the plane to the runway to fly is as important as other regimes of the flight experience.

Taxi to and from the runway when you're flying is "for the purpose of flight."
Taking it to the maintenance shop or the fuel pumps without flying it is not.
 
The FAA doesn't hold that view. Taxi time is included in pilot time. The FAA holds that moving the plane to the runway to fly is as important as other regimes of the flight experience.

Taxi to and from the runway when you're flying is "for the purpose of flight."
Taking it to the maintenance shop or the fuel pumps without flying it is not.

Taxi for 3 hours, fly for 12 minutes. 3.2 PIC. Yeah baby!

I can log a 24 hour "flight" a Comanche that has tip tanks without refueling. 24 hours for the price of 6? Don't mind if I do.

Duty time? Sure. Flight time? Another case of the FAA wearing their ass as a view limiting device.
 
Taxi for 3 hours, fly for 12 minutes. 3.2 PIC. Yeah baby!

I can log a 24 hour "flight" a Comanche that has tip tanks without refueling. 24 hours for the price of 6? Don't mind if I do.

Duty time? Sure. Flight time? Another case of the FAA wearing their ass as a view limiting device.

Look at it this way you get to log the time that if you get in a wreck the FAA cares about.

I know a guy who wrecked a plane during a starting accident (no electrical system). Thankfully nobody was seriously hurt. Lots of bad decisions and judgement they were intending to fly so the FAA got involved. Had the same thing happened during winter maintenance he could have dragged the plane back in the hanger and never called the FAA.
 
Ever fly a tailwheel airplane? On windy day? Better be flying it from the time the wheels move till they stop.

Obviously you have if you own a 140. ;)

I don’t disagree, but taxiing is not for the purpose of flight. It is for transporting the airport into position to move for the purpose of flight.
 
I don’t disagree, but taxiing is not for the purpose of flight. It is for transporting the airport into position to move for the purpose of flight.

I believe the FARs disagree with your logic. It’s defined in FAR 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; or

(2) For a glider without self-launch capability, pilot time that commences when the glider is towed for the purpose of flight and ends when the glider comes to rest after landing.


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I don’t disagree, but taxiing is not for the purpose of flight. It is for transporting the airport into position to move for the purpose of flight.
You and Ed Fred are on the same page. But that page is different than most of the rest of us. LOL
 
Apparently there are some who want to milk as much flight time in their log book as possible. Can’t blame you for that, but I’m not convinced it’s correct. I suppose it’s way too much to ask the FAA to be clear about things.

From a practical perspective, the logging of that extra few percentage points of flight time could only have a negative effect if it were protested when there was barely enough time for some purpose such as minimum amount of time for a particular rating. If one were at the exact number of hours to qualify it might turn out to be a problem. After just a few hours beyond that, one would have enough either way.
 
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What a fuss this makes.

Block Time: Start Moving-Stop Moving (aka Chocks out-in). Loggeable, includes flight time.

Flight Time: Take-Off to Landing. Airborne.

Garmin Pilot is very precise and useful in this, at work the Fmgs will record these times for me. Tachometer will cut you time off, but will actually record a calculation of engine working time instead of a "moving" one.
 
Apparently there are some who want to milk as much flight time in their log book as possible. Can’t blame you for that, but I’m not convinced it’s correct. I suppose it’s way too much to ask the FAA to be clear about things.

(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; or

There are lots of regulations where you need to read multiple Legal Opinions by the the FAA Chief Counsel to cover the edge cases, e.g compensation, holding out, logging safety pilot time, etc. But there is absolutely no ambiguity in this one. I don’t know how they could make it any clearer. You start the airplane, taxi three feet and do a brake check, and start the clock. You taxi to your hangar or tiedown and stop the airplane so you stop the clock. I can sometimes spend 15 minutes taxiing if I pick a time when the airlines are landing and taking off, but for logging purposes, that’s pilot time. If you aren’t pursuing a rating, you are only required to log takeoffs and landings for currency, and an hour every two years for your Flight Review, so if you want to log flight time instead, you are free to do so.

FYI, ForeFlight does a good job of tracking actual flight time if you tap the record button when you start and tap it again when you stop. If you just shut off the iPad it sometimes gets confused and will not stop the clock.
 
I log the way the majority here do - engine running time, Hobbs or watch or electronic logbook. Doesn't matter too much.

However, I can also see the other side, especially with @EdFred 's example of taxiing for 10 minutes, sitting in the runup area for 24 hours, doing one lap around the pattern and logging 24 hours of flight time. Given the current interpretations of flight time, of course, this is (apparently) completely legitimate. And also absurd.

So I was thinking - IF you were the FAA in the beginning and wanted to write the reg so that flight time started on takeoff roll and ended at the end of the landing roll, how would you write it? You might write it basically the same - "move under its own power for the purpose of flight" would be a reasonable way to try to specify the takeoff roll. Maybe not the best way, but a reasonable one.

Of course, the easiest way to eliminate any issue on this would have been to write it as "begins when the aircraft takes off and ends when it lands". Why would anything else be counted as anything like "flight time"?

But like I said, I log like most others, because it's well established and really doesn't matter from an ethical or moral basis anyway.

However, I do notice that often, people will ignore the second half of the rule - "and ends when it comes to rest after landing" - when it comes to flights that were aborted for some reason. I've seen people with 0.3 logged **, no landings, because they taxied out, did a runup, found a problem and taxied back. And the arguments will generally be some variation of "you're PIC even on the ground" or "you have to fly it at all times". Well, yes, but if you don't have a landing, then logically it doesn't count as a flight by the second part of the definition. It's either that or the flight time is infinite, if the clock starts when you first taxi but only stops if you land. Pick the choice which is not absurd.

** I am one of them, a flight like this back in my training days, my instructor logged it like that. Doesn't seem worth correcting at this point.
 
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If it was only the takeoff roll they were concerned with they probably would have just defined it as in the air. the time an aircraft takes to launch from the runway and come to a stop doesn't probably add up to a couple of minutes even on the monster jets that take up all of the 11,000+ foot runways at IAD.

As I said in my first post. The FAA intent (and practice) is to include taxi time as long as the taxiing was part of a flight.
As RussR says (and I pointed out) the FAA takes a pretty liberal view on allowing pilots to estimate both pilot time (for your personal logbook) and time in service (for your maintenance logs), be it Hobbs time or Tach time or some other reliable mechanism. Just be consistent.
 
what does foreflight record if you fly 40 kts into a 40 kt wind?
 
Let’s say you’re a student pilot doing your training at Addison airport in the Dallas area. IF all your taxi time is flight time you will be logging a lot of time waiting in line in the taxiway. That time is not going to be very indicative your flight experience.
 
Friends - Over the last couple of days, I took three flights. My Foreflight logbook recorded almost an hour more time than the plane's tach. (4.7 hours v. 3.8 hours). Can anyone explain why there is such a significant difference?

Thanks.

Use wristwatch time beginning from first movement to parking.

Bob
 
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