Pilot training | billing flown hours as hobbs, tacho, operating time

  A novice pilot who is not knowledgeable about billable hours may pay as much as 20 to 60 percent more in basic pilot training than they would actually need to. How is this possible?
 It has just as much to do with hourly billing and phraseology! "CZ"

 Not many beginner students know this and so it is easy to "work with" them.

Let's take a model example. You decide to do your basic PPL pilot training. You have chosen four schools that have the same Cessna 172 aircraft and charge the same price per hour at the first sight 4500CZK with some additions to distinguish the type of hour . Such information about add-ons is most likely beyond your discernment as a novice pilot. But those prices are not the same at a second sight, what's more they are dramatically different from the point of view of a pilot-student, who wants to fly as much as possible for his money in each task in the air! He doesn't care much about taxiing and other things. So he checks the prices:

One school will tell you that they charge motor "TACH" hours, another will tell you that they charge "HOBBS" hours, a third school will tell you that they calculate "flight hours" which you pay for. The fourth school will tell you that you will only pay for "takeoff to landing time".

At each school, even though the price looks the same you will pay something different and quite substantially!

And with each charging there are different advantages and disadvantages associated with it, for the student, the aircraft owner, the operator, which will be reflected in the training, the students and the condition of the aircraft.

If you want to understand all this comprehensively, or make your training cheaper, read the following text where everything will be explained.

For a better understanding, we must start with the technical equipment - switches, wiring diagrams and the actual timeclock types to make everything clear:
The "engine hour" sometimes called "TACH" is usually part of the tachometer and is located in the lower half of the instrument, or it is directly dependent on the tachometer and can be located elsewhere. The actual engine hours show the number of normalized engine hours, which you can imagine as accelerating and decelerating depending on the actual engine revolutions. In other words, if you idle the engine for an hour of normal time on your watch - the correct motor hours will count and show one tenth of an hour, for example.If you fly for an hour at 2500 rpm, the engine clock will show one hour because it has that mode as the normal mode (if it is set that way).If you were still overspeed the airplane for one hour at 3000 rpm then the engine clock will show, for example, an hour and a half of "flying" time.  This is a model situation which shows that engine hours are very important for engine and propeller maintenance and parts and oil change intervals and show the stresses on machine parts. Engine hours used to be on larger and more complex aircraft
Some aircraft use a "TACH" clock made of glasscocpite that depends on altitude change. So the clock turns on after take-off and off after landing.

Some engineclocks are FADEC dependent, these then indicate otherwise by a combination of the above.  You may not encounter a "Tacho" clock in basic training.

Ultralights and simple planes have "some" would-be "engine hours which, if wired to an oil pressure switch, these only simulate the above real engine hours. The "engine" clock in an ultralight can only distinguish between turning the engine off and on via the oil pressure switch. They cannot work with engine speed!

If this some "clock" in an ultralight is wired to the main switch, then it shows how long the on-board installation has been switched on, and such a reading is completely useless and untelling if someone leaves the main switch on and goes on vacation. The would-be "engine clock" counts and counts, the hours jumping one after the other if the other on-board accessories have not been properly switched off, until, for example, the oil and recharge lights totally drain the battery, or the owner returns from holiday. A "sort of engine" clock wired like this has no telling value!

The Hobbs on-board clock is usually fitted by the GA aircraft manufacturer and shows one tenth of an hour as the smallest part, which is six minutes. The important thing is where the signal that starts this clock is wired !!! Most small aircraft in the GA category have "hobbs" clocks.
The biggest problem is that even Hoobs clocks can be wired to a master switch- master, or to an oil pressure switch.
If they are wired to the Master switch, they will turn on and start showing the time without you ever having started the engine, warmed up the engine, done the necessary procedures, set the instruments and radio station, or driven to the holding position on the track. The above described matters, especially in winter operation when you warm up the engine before taxiing for a long time, and for a long runway when you taxi for a long time, can consume perhaps 15 to 20 minutes, but only if you have started the old Cessna 172 for the first time! Which is not the rule with old airplanes! Not every instructor will let you taxi with a cold engine, thinking you will warm it up by taxiing.

Wiring the Hobbs clock to the master switch will cause the highest increase in counted time.

We won't speculate why, who and for what purpose wired the Hobbs clock to the main switch.  If you have arranged with the flight school to pay for the HOBBS clock as part of your pilot training, then a Hobbs clock wired in this way will count 10-20 percent more time that you never taxi or fly and you will pay the same amount as if you flew "takeoff to landing".

Wiring the hobbs clock through the oil pressure switch will cause it to start reading time after the oil system is pressurized after the engine is started. It's a little more accurate to measure, but not nearly as accurate as actual engine hours, and it also helps you save some precious minutes that you don't have to pay in, for example, radio settings for individual microphones, freqventions settings, and other instruments that can run off battery for a short time without having to start. But the fact is that any instructor will teach you how to start the engine, check oil pressure and set the rpm on recharge. Only when the alternator is recharging will he let you configure and operate the other instruments and equipment on board.That's the way he has it down and he won't want to change it.

 The flight school may want to count the students hours in HOBBS because the planes are not theirs and they have leased them, or they pay high lease rates, offices at busy expensive international airports and old experienced instructors.

This then the student pays other costs hidden in the hobbs in addition to the lease. The advantage for the flight school is full time paid including taxiing and engine warm up.  Which is the most significant problem for the first client on a winter flight day when the engine is hard to start and pays without flying.  Further, it is very much to your disadvantage if you are flying navigation flights to multiple airports with full landing and paying fees.  In that one real flight training "hour" you will pay for, say, three taxi times from RWY to stand and back if you have visited three airports.

  The training syllabus lists the hours flown in each exercise. If you agree with the school to include the taxiing in the hours flown (and some schools practice this) then you have actually flown 20-25% less, but only if you have a short home airport and a hangar very close to the RWY. If the hangar is further away and the runway is long, then that is a significant element in your disadvantage when charging hobbs.
 I'm not saying it's right or wrong, just stating it, some students have it and fly out of large international airports basic pilot training, others don't have it and fly out of small airports. That's everyone's business, it's their decision.
 The downside for the operator, and even more so for the aircraft owner, is that when they lease the aircraft to HOBBS, there is a risk that pilots will not follow the warm-up procedures or regimes exactly, and will fly away with an under-warmed engine, and will also put more stress on the landing gear when taxiing fast- because the taxiing is also paying. I have also seen takeoffs from taxiways where AFIS was not present or its service had ended!  And of course pilots will try to set the altimeter and radio including the transponder while taxiing to save time. This means they pay less attention to taxiing, which may not end well at grassy or poor quality airports.I've also seen broken landing gear and broken propellers outside the taxiway.

"Flight hours" is a term used in large scale aviation to mean the time from putting the aircraft into motion under its own power for takeoff to the aircraft coming to rest on the stand after flight. Flight time is the time from departure to arrival (from wheel schock to wheel schock).
    In the case of aeroplanes, engine powered gliders and powered-lift aircraft, it is the total time from the time the aircraft is first set in motion to take off to the time it comes to a final stop at the end of that flight.
    For helicopters, the total flight time from the time the helicopter rotors begin to rotate until the helicopter comes to a final stop at the end of that flight and the rotors stop
    For gliders, it is the total time from the moment the glider starts to taxi during take-off to the moment it comes to a final stop at the end of that flight.
 Other flight schools explain the same thing from removing the vheel chocks to getting them back. This time is convenient for the flying staff, when their paychecks run out and their flying breaks are counted.
It actually differs from "Hoobs" in that the student pilot does not pay for attempts to start and warm up the engine, including setting up instruments, radios, transponder, etc.

The lowest price is for "time in the air" the technical term sounds misleading :" Time in operation" i.e. from take-off on the RWY to landing on the RWY. It is the time from the moment the aircraft leaves the ground to the time of first contact with the ground on subsequent landing. The operating time is the time interval according to which the different items of the maintenance programme are also carried out.
It is usually based on GNSS (GPS, Glonass, Galileo) data from some forward speed that can be set and is not taxi speed, or a transponder based on a pressure sensor change where it turns on and off after about 10-50m of altitude after take-off. If the aircraft is not so equipped the pilot keeps track of the time on a stopwatch or watch himself. Such time counting is very convenient for the student in flight school and disadvantageous for the instructor, operator and aircraft owner. It is more of an aero club practice, or in the case of small flight schools, the owner uses it to gain clients and students for convenience at the expense of his own time and money. The indisputable advantage to the owner is that all sensible pilots take their time, taxi slowly, and devote themselves to taxiing and warming up the engine before takeoff because they don't to pay for it. The aircraft is then in better condition than one operated on "flying hours" and in many times better condition than one operated on "Hobbs"

 Well, let's finish the example from the introduction, in which the biggest variable is the length of the aircraft taxi from the hangar to the RWY holding point:

Cessna 172 price 4500,-CZK per hour Hobbs you pay 1x 10 minutes warm up, 2x taxi from the stand to the RWY which is 1000m long plus 200m from the hangar, taxiing at walking speed - as prescribed you will travel 100m in 1 minute.Then taxiing will cost you 12 minutes x2 is 24minutes. Engine test and prop test 2 minutes. 60-10-24-2 is 24 flight minutes in one hobbs hour. The bigger  airport then the less you fly and more you taxi not to mention that you have to give way, taxiing landing and taking off aircraft when crossing the runway and on hold. So add at least 5 minutes or more. We'll tactfully leave out the fact that the runway changed during your training and you had to taxi to the other side. So you probably only flew 19 minutes of the billed hobbs hour.

Cessna 172 cost 4500,- per hour Tach ( if the switching signal is linked to actual moto hours) You do not pay for warm up below operating speed, or a very reduced price because the engine -moto hours are slow and you adjust the RDST restraints etc. during warm up. You pay for the engine test 2mins plus taxi 24mins. You give priority to landing and take off traffic and that will give 5 minutes. 60-2-24-5 is 29 minutes flown in a TACH flight hour.

Cessna 172 price 4500,- per hour "flight hour" ( from wheel chock to wheel chock) You do not pay for engine warm up and engine and propeller test on site before the aircraft starts. (Unless the instructor deliberately asks you to do it at the holding position or if it is necessary to do it  due to noise precautions) You do not pay for instrument settings, rdst, transponder, etc. You pay for 24 minutes of taxiing. You pay to give way to other traffic for 5 minutes. 60-24-5min is 31 minutes of net flight time as described in the TACH flight hour.

Cessna 172 cost 4500,- per hour for "takeoff to landing" time spent in the air or for" operating time".
You do not pay for engine warm-up, engine and propeller test, or taxi. You don't even pay priority for other traffic. You  enjoy your net 60 minutes of flight time.

In ultralight flying, not many schools charge in hobbs. Here they usually charge "flight hours" or better for the student "operating time- time in the air".

It is possible that an ultralight student pilot with a minimum of 20 hours flown ( as per the syllabus) will actually spend more time flying in flight training than a PPL student pilot flying in hobbs. with 45 hours "flight time" as per the PPL syllabus.

A student pilot of an ultralight aircraft with an average training price of 50 000,-CZK can then actually fly more hours in the air than a student PPL pilot with an average training price of 180 000 to 200 000,-CZK.

What is the efficiency of the training and the resources spent according to the individual hours charged, the kind reader can certainly calculate for himself.

Filip Zejda


V roce 2014 jsme se umístili na skvělém druhém místě v anketě "Letecká škola roku" ve kategorii škol věnujících se výcviku pilotů ultralehkých letadel.



Letecký informační server... více

Stol Zenair letouny...  více


Mobil:    +420 603 107 704
E-mail:   filip.zejda@seznam.cz
Adresa:  Zbilidy 101, PSČ 58805