View Full Version : Hobbs or Tacho?


pistongone
12th September 2006, 23:47
How many of you object to paying on the Hobbs? It makes you rush through checks whilst watching the hobbs spin and even waiting for the pitot to heat up cost you money! I think the farest way is tacho or airborn, what say you Gents?
PS: i was once stuck at Elstree international, when the ground controler(a/g to the CAA) kept me waiting at the hold for 20 MINUTES:ugh: Whilst Mr Montclare came in a twin! The PA 32 costs £3:00/min so i wasnt best pleased. Before you say i was entitled to go on my discretion, i want to go back as a few friends of mine live very close to the airfield and cheesing them off wont look good on my CV, like they wont accept you back in:=
Your thoughts please:confused:



Dude~
12th September 2006, 23:51
Hobbs sucks. At one airport I was held for 45 minutes due to commercial traffic. At least I wasn't paying for it though.

In oz I once hired a Duchess and was charged via an airswitch - basically I paid for all time spent about 50 kts! Definitely the best way. 2 nd best it Hobbs.

I don't like places that just rely on the instuctors watch as the tech logs become horribly out of synch with reality.

Grainger
12th September 2006, 23:55
LASORS Appendix A to Section A:Flight time (aeroplane): The total time from the moment that an aircraft first moves under its own or external power for the purpose of taking off until the moment it comes to rest at the end of the flight.

Flight time (helicopter): The total time from the moment a helicopter's rotor blades start turning until the moment the helicopter finally comes to rest at the end of the flight and the rotor blades are stopped.That's what you should be logging, and I guess what you should be paying for.

Whatever, never allow anything to make you "rush through your checks". :eek:

IO540
13th September 2006, 00:00
There is just one solution to this frequent problem: get yourself a plane.

Then you log total moving time (brakes off to brakes on) in your personal logbook.

You log the airborne time in the aircraft logbook(s). All time-based aircraft maintenance is (or should be) based on airborne time only.

The above is correct for both G-reg and N-reg ops.

Anything else (like taking the reading from some meter in the dash) is mandated by the fact that a lot of people (both students and instructors) cannot be trusted to report the correct times :)

Charging for BO-BO (common in many schools) encourages crazy behaviour on the ground, but the reality is that if they charged for airborne time only, the hourly rate would have to go up to compensate for the reduced income.

Say again s l o w l y
13th September 2006, 00:50
Or you charge for airborne + a set amount. We use 10 mins. This is to stop people rushing checks or not letting the engine warm up.

It also has the added benefit of not ripping people off if they get stuck on the ground for an extended period of time.

IO540
13th September 2006, 09:46
How do you measure airborne time?

One could take it on trust, with the sanction that EDM700 data can be downloaded ;)

Despite rumours about their existence, I have never actually come across an airspeed (or landing gear) operated timer.

slim_slag
13th September 2006, 10:53
There are outfits out there who will charge on the hobbs, unless the tacho is higher, when they will charge on the tacho.

So if you spend most of the time in the pattern or practice area you will pay on the hobbs - even though expensive stuff like engine maintanance is done of the tacho. If you go on a long cross country and operate at high RPM you could find yourself with a higher tacho and pay more than the hours you actually operated the engine.

Just something else to watch out for :)

Say again s l o w l y
13th September 2006, 10:59
Airborne time is taken on trust, though we have the records from the tower to go on if someone is doing a local flight.

There some new things on the market that will end any ambiguity, basically a hard drive that records flight time and is then downloaded when you return to base.

Most people are basically honest though, so it's rare you have a problem, though I usually notice any issues from the fuel burn. If it looks significantly out, then I'll have a dig about, otherwise we rely on honesty.

Mark 1
13th September 2006, 11:04
The main reason the Hobbs is used by commercial hirers, is that it allows them to advertise a lower "headline" hourly rate.

In my aeroplane, the tacho is about 20% behind the Hobbs; they both started at zero when the aircraft was flown for the first time.
So, to get the same revenue, the hourly rate would be about 20% higher if using tacho. That may amount to the same cost to the user, but it would be commercially less attractive to advertise the higher rate.

Putting an airspeed switch in the Hobbs circuit is relatively cheap and easy, and makes accurate log keeping easier, but unattractive for the same reasons as using the tacho.

I have always used tacho for group owned aircraft, as it's a fairer way of apportioning costs.

False Capture
13th September 2006, 11:11
Pistongone,

How many of you object to paying on the Hobbs? It makes you rush through checks whilst watching the hobbs spin and even waiting for the pitot to heat up cost you money!

For economical flying, try this:
MASTER SWITCH ................ OFF

Darth_Bovine
13th September 2006, 12:44
I'm pretty sure the Hobbs (certainly in the planes I hire) only turns over when the oil pressure reacehs a certain level. I.e. when the engine is running. At this point you are most certainly in command of the aircraft and hence should log (and pay) as such.

I can't see how you can pay for a lower time than you log. Surely you can't say that taxiing is not logged time? :ugh: Hence you should pay for it as such. If I could get away for only paying for the time above a certain airspeed I'd have a lot more hours in my log book and have saved a fortune! Most of it would have been spent taxiing around the airport though rather than boring holes in the sky.

Cheers,
R.

slim_slag
13th September 2006, 12:58
Long time ago managed to run up 0.3 on the hobbs trying to start an engine after a night at sub zero temperatures at 7000ft. Probably did more damage to the engine than many hours at cruise. So there is enough oil pressure in a cold engine just when being turned over by the battery (which held out superbly!) Asked for some additional instruction on starting cold engines after that :)

waldopepper42
13th September 2006, 13:36
False Capture,

Yep, that works - bit difficult negotiating controlled airspace though.

Many years ago, my club did use hobbs as the basis of charging of one of our aicraft. The master switch ploy was one reason for reverting to tacho, the other reason was that the more unscrupulous renters were simply flying the whole trip with the throttle against the firewall. Get there faster and, therefore, cheaper(!)

Not their problem if the engine wears out a bit quicker.....

WP42

bose-x
13th September 2006, 13:50
I charge take off to landing on the occassions I let others use mine. That way they are relaxed and dont rush into the air, miss checks or abuse my expensive engine.

I know to the litre what the fuel burn is and know if I am being had over. Touch wood so far everyone has responded to the trust appropriatly.

Hobbs and Tacho just encourages abuse.

Martin @ EGLK
13th September 2006, 14:03
Personally, I prefer the Tacho solution that our group PA-28 runs on.

If I fly for an hour at 90kn, the tacho shows about 45 mins. If I fly at 110, it shows about 65 mins. So I get more airtime for my money. If I was on hobbs/clock, I'd go everywhere at 110kn. I think of it as my reward for treating the engine with care. :)

The aircraft at a club that I frequent use the airswitch that Dude mentions. It activates at 40kn. I pay for my time >40 +10 mins ground time. The reason they do this is so that we DON'T rush checks & take care when taxying the old girls around a bumpy grass strip.

BFMD
13th September 2006, 16:17
The thing that annoys me at my club is their method of recording the times. I recently flew to a small airfield where you literally parked next to the runway. When getting back to the club I was picked up for putting 0.1 as taxying time and was told to change it to 0.2. I argued the point saying that my taxy time was about 30 seconds, but was told that's what club policy is.

I guess this must happen on a daily basis which means the aircraft's airborne times must be well out. By doing this they are reducing the airborne time they log, thus reducing how often they have to service the aircraft, which ultimately reduces their running costs. Thinking about it, is this illegal?

A and C
13th September 2006, 19:36
I lease a number of aircraft to a flying club and I charge for take off to landing.

The taxi time is not an issue to me as I lease the aircraft "dry" but the reason that I charge Take off to landing is one of flight safety after all if a pilot is not paying for taxi time there is no reason to rush the checks or take off with a cold engine.

Only time will tell if this is the correct policy but if the engines reach overhaul with the cylinders only being removed once for a look at the top end I will be happy.

I won't use a hobbs or the tacho to record times but if I suspect that a pilot is cooking the books the fuel uplift is sure to catch him out, I have also considered fitting GPS loggers to the aircraft to automate the invoicing but the drive to do this is to cut down on administration costs rather than squeeze the customers for more money.

OpenCirrus619
13th September 2006, 19:51
I know of at least 2 clubs who have a Hobbs controlled by a pressure switch connected to the pitot system fitted to their aeroplanes. This arrangement provides an accurate record of flight time.

One of the clubs adds a little (fixed amount) for taxi time.

Either way there is no incentive to rush checks - it costs the same whether you take 5 or 25 minutes between startup and take off.

OC619

FullyFlapped
14th September 2006, 09:46
Must admit I'm confused now, as my tacho always seems to tie up with my watch ... or have I just assumed this ?

What exactly does the tacho measure ?

FF :ok:

IO540
14th September 2006, 09:54
A "tacho" (the hour counter inside the rev counter instrument) might measure various things.

Some will measure purely engine running time, but they actually count revs so the "time" will be right only at say 2400rpm.

Some will measure engine running time but only if above 1200rpm or so (I have one of those).

Etc.

These threads always run for ever. There is arguably only one equitable way of doing this: charge for airborne time, and charge for fuel separately.

Technologically this is possible but since there is no tamper-proof flowmeter, you have to take it on trust that somebody has not fiddled with it. I have seen both ordinary renters and instructors fiddle with the flowmeter, to reduce the bill.

In practice almost no flying school is going to install a flowmeter; it's about £2000.

And as has been pointed out, charging for airborne time only results in an hourly rate which appears uncompetitive. You can't win.

slim_slag
14th September 2006, 12:39
There is arguably only one equitable way of doing this: charge for airborne time, and charge for fuel separately.

Technologically this is possible but since there is no tamper-proof flowmeter...Oh io540, nothing works for you unless it's full of silicon and costs thousands of pounds. One wonders how people got along in the old days.

How about using a marker pen and a stick of wood. After a little bit of work you can even throw the marker pen away. This will allow you to work out how much fuel you start off with and how much fuel you have finish with. Use some mental arithmentic (remember that??) to calculate the difference and bingo, you know how much fuel you used.

I know you will find objections to this simple solution, but they are all easily worked around.

Hampshire Hog
14th September 2006, 12:52
My club charges chocks off to chocks on but, if we experience a taxy/take-off delay, we are told to report it to the club and they adjust the time accordingly. I've done it once, after holding for commercial traffic at Bournemouth. That seems like a fair policy, so long as it is not abused.

HH

B2N2
15th September 2006, 05:11
Tach time only works for group operated aircraft.
For Commercial operations (pay for hire) hobbs is the way to go.
Hobbs time is equal to clock time while tacho time is not.
Tach time varies with engine load.
You pay for the time you have the aircraft running under it's own power under your control, it's that simple.
You don't complain about being stuck in traffic with a rental car do you?
You bring it back 2 hrs late, you pay for another half day.
That's their rules.
For economical flying, try this:
MASTER SWITCH ................ OFF
Right, no transponder, no radio, no Nav...and a tacho time higher then Hobbs...big FLAG

SoCal App
17th September 2006, 18:37
Here is the FAA Safety.gov's answer to this question as it applies here in the US. The full text can be found here: http://www.faasafety.gov/hottopics.aspx?id=20

Here is the cut and paste. Remember this is as it applies here in the US.

Logging Time -- Flight & Aircraft


Where does the time go? How do you log your time? Sure, I know it goes into a pilot log or maintenance record, but where does it come from? If we log two hours of flight time, does that mean the aircraft was in the air for two hours? When a 100-hour inspection is performed on an aircraft, is the 100 hours in operation based on the tachometer reading? Hobbs meter? Sun dial? Part 1 of the Federal Aviation Regulations contains definitions of terms used. It defines the following:
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 is the time that commences when the glider is towed for the purpose of flight and ends when the glider comes to rest after landing.
Time in service, with respect to maintenance time records, means the time from the moment an aircraft leaves the surface of the earth until it touches it at the next point of landing.
Neither definition talks about tachometers or Hobbs meters, and clearly, they are not the same times. The term, “block to block” is a convenient way of describing “flight time”. It means that the aircraft has been started and may have been running for some period of time, but “flight time” doesn’t begin until it moves for the purpose of flight. The tachometer will have certainly begun recording time as soon as the engine was started, and the Hobbs meter, depending on how it is installed, may have begun recording as soon as power was applied to the aircraft. “Flight time” ends when the aircraft terminates at its parking location even if the engine continues to be operated for some period of time. Pilots, who log “flight time” based on tachometer readings or a Hobbsmeter, may be in error.
“Time in service” on the other hand, is defined as the time from the moment of takeoff to the moment of touchdown. This also is probably not represented accurately by either a tachometer reading or Hobbs meter. Some operators have installed a “squat” switch on their aircraft with retractable landing gear. As soon as the weight is off the wheels, a recorder begins tracking time until the aircraft touches down again. As long as the aircraft isn’t landed gear up, this is probably the most accurate method of keeping track of time in service. Operators, who base required inspections on tachometer or Hobbsmeter readings, are probably cheating themselves out of several hours a year, depending on how much flying is done in the aircraft. Aircraft operated at busy airports may spend considerable time with engines running before takeoff and after landing as they taxi to and from the parking area, or hold on the ramp while a pilot picks up a clearance and performs a run up.
In most cases, flight time and time in service for a helicopter are the same. In the case of a helicopter with wheels, it is conceivable that the aircraft may spend some time taxiing in or out of parking areas that should not be applied against the time in service. This might be an important factor since many expensive helicopter parts are time limited. Losing 10 hours over a 2000-hour life might be significant.
The reason most places use tachometer or Hobbs time is because to log time correctly would require the operator to accurately record block out/in, and takeoff and touchdown times. Who cares anyway? Maybe after 100 hours of logging flight time from the tach, a pilot has accumulated 1 hour of extra time. What’s the big deal? It’s not like anyone is loading the logbook with several hundred hours of Parker Pen time, perhaps not. But if someone were trying to make an issue of an airman’s competency, it would certainly be an easy way to start by proving that we don’t even know how to properly log time. Too many sources of time can make us uncertain about which is correct.

End of cut and paste.

Lister Noble
17th September 2006, 20:04
Too many sources of time can make us uncertain about which is correct.

Years ago when I first started sailing from the UK to Europe I set one clock to GMT,one to "Eurotime" and one to British summer time.
Boy and did I get into a real muddle,all trips after that I set time on main clock to GMT and used that for all navigation,set wrist watch to local time.
Lister:)

Pilotdom
17th September 2006, 22:48
At My school we Log the Hobbs time and them -0.2 to allow for taxi and checks etc so

1.2 on the Hobbs gets charged at 1.0 to the student!