How Flight Training or Hire Costs are Calculated

Different Methods of Working Out the Time a Light Aircraft is Flown

Oct 16, 2008

Engine on to Engine off, brakes off to brakes on, 'tacho hours', 'datcom' hours, 'hobbs' hours etc; there are many ways to calculate and charge for flying a plane.

When students start to learn to fly airplanes, they are charged by the hour. When pilots want to hire a plane, they will be quoted an hourly rate.

And those who have a share in a group-owned aircraft will often pay at last partially by the flying hour.

But how are these flight times calculated? There are different ways, and they may affect the actual cost when a student or pilot is comparing rates.

All planes have a meter called a ‘datcom’ or ‘hobbs'. This turns over whenever the aircraft engine is running. So if the pilot is charged datcom or hobbs hours, he or she will be charged the exact time during which the plane’s engine is on, regardless of whether the aircraft was standing still, taxying, or flying. This flying time is recorded automatically.

Brakes Off to Brakes On

Some organizations charge only during the time the aircraft is moving. The student or pilot pays from when he or she first takes the brakes off and starts taxying, to when the flight is completed and the brakes are put back on again. This way of charging depends on the pilot recording the time precisely, so mistakes are more likely than with the first method.

‘Tacho’ Time

A ‘tacho’ is a gauge that counts the hours the aircraft engine is running. However, the rate at which it turns depends on the engine RPM. So if, for example, the aircraft is idling while waiting for other traffic, it could be there for half an hour, but the tacho might only have recorded a quarter of an hour. But during a very fast cruise, half an hour recorded on the tacho might have only taken twenty minutes. Tacho hours are often used for maintenance purposes, so many flying groups use this method.

Which Method Works out Cheapest, and Which is Most Expensive?

Hobbs or datcom charging is usually the most expensive. Brakes off to brakes on hours can often work out cheapest, particularly at a busy airfield where the planes are often idling while waiting for traffic.

Tacho hours depend very much on the type of flying which is done. If the pilot usually flies long legs at a normal cruise setting, this can be a very cheap method of paying. If, however, he pushes the aircraft to its limit, or does aerobatics, it may work out quite expensive.

The author of this article used to fly a light aircraft which was charged using tacho time, and she found that it was about 10% cheaper than hobbs or datcom hours, and around the same as brakes off to brakes on charging.

Any student or flying who is shopping around for flying lessons or to hire an aircraft needs to remember the above. As well as asking the hourly rate, he should ask how it is being calculated, since this can make a huge difference over a period of time.

See also the aurthor's Blog, which has an on-going series about her flying training.

The copyright of the article How Flight Training or Hire Costs are Calculated in Aviation is owned by Helen Krasner. Permission to republish How Flight Training or Hire Costs are Calculated in print or online must be granted by the author in writing.