Ratio of Hobbs to Tach for instruction w/tower

Let's say someone (not me!!) is crazy enough to buy a Cessna 152 or 172
and instruct in it at a towered airport. What sort of ratio of Hobbs
to tach time would you expect?

The value (I've played with .85 up to 1.0) has a surprisingly large
effect on how much you have to charge for the plane.

--
Ben Jackson

http://www.ben.com/

I don't think it makes a lot of difference whether the airport is towered or
not. Why not just put a Hobbs meter in the plane?

"C J Campbell" wrote in message
...
I don't think it makes a lot of difference whether the airport is towered or
not. Why not just put a Hobbs meter in the plane?


Or look at your watch? Write down engine start time, then engine shutdown time.
That's how we did it when towing banners. Cub's don't have electrical systems
or hobbs meters, and when you're flying along at 1900 rpm's, the tach time isn't
exactly accurate either.

In article ,
C J Campbell wrote:
I don't think it makes a lot of difference whether the airport is towered or
not. Why not just put a Hobbs meter in the plane?

It does have a Hobbs meter. But plane costs are mostly in units of Tach
time. At a towered airport you (probably?) spend more time taxiing and
therefore accumulate more Hobbs time per unit Tach.

So if you charge $66/hr wet hobbs and tach time is accumulating at 85%
as fast as the hobbs you have about $7765 of revenue per hundred tach
hours.

--
Ben Jackson

http://www.ben.com/

On Sat, 03 Jan 2004 22:41:13 +0000, Ben Jackson wrote:

It does have a Hobbs meter. But plane costs are mostly in units of Tach
time. At a towered airport you (probably?) spend more time taxiing and
therefore accumulate more Hobbs time per unit Tach.

I assume you mean maintenance since that's about all done with tach time,
where rentals are usually based on Hobbs time, if the plane has one of
those. The reason is that the rental makes more money since the Hobbs
will indicate a higher number than the tach. This is a benefit when it
comes to paying for your maintenance.

I've almost never rented a plane based on tach time unless the Hobbs was
not working right, but then most of the planes I rent have a Hobbs meter
and you can see why they'd want to use it's figure.

You're correct in that at towered airports you'll log more Hobbs time than
tach time, but those have been the breaks for me. I know of no planes
around here that use the tach for anything beyond maintenance.

Out of curiosity, why are you trying to figure the ratio anyhow? It
varies at each airport depending on how far from the hangar to the ramp or
runway you are, how long you warm it up, etc.

Based on your website, are you planning on getting back into flying, or is
your site just not updated, kinda like how I do mine?

In article . net,
Matthew P. Cummings wrote:
On Sat, 03 Jan 2004 22:41:13 +0000, Ben Jackson wrote:
I assume you mean maintenance since that's about all done with tach time,

Scheduled maintenance (100hr inspections, possible 50hr inspections),
oil changes, oil consumption, fuel consumption, engine life, airframe
life, etc all scale with tach time.

If you then charge by Hobbs time there's a 'slop' factor in there
because Hobbs Tach. My question is: what is that factor? I was
hoping someone who had been involved in renting airplanes had an
estimate.

For example, let's say it costs exactly $45/hr wet Tach to operate a
Cessna 152. If you charge $45/hr wet Hobbs and the ratio is 1:1, you
will never break even (pay your fixed costs of insurance, storage, and
interest on the loan above and beyond hourly expenses). However if the
ratio is .85 Tach hours per Hobbs hour, then you will get about $8/hr
towards your fixed expenses. In that case you might break even around
600 hours, assuming about $5000/yr fixed expenses.

Since the margins are small, the factor makes a big difference.

Based on your website, are you planning on getting back into flying, or is
your site just not updated, kinda like how I do mine?

Oh, I just never update my website. I bought a 1965 Comanche 260 last
August and I'm about 2/3rds of the way to my instrument rating (checkride
on Feb 7 if the weather lets up enough to get the rest of my hours).

--
Ben Jackson

http://www.ben.com/

"Ben Jackson" wrote in message news:BJFJb.49560

. What sort of ratio of Hobbs
to tach time would you expect?

I've recall a figure of about .8 for planes used at flight schools. Of
course, that's going to vary widely depending on the nature of usage and
location, but on average, .8 or a little higher. All you could use the
figure for would be an approximate anticipated figure, anyway. Your real
figures could only be determined after-the-fact.

JG

I had the hobbs go out on me just added .2 to every .8 on the tach


"Ben Jackson" wrote in message
news:BJFJb.49560$I07.154008@attbi_s53...
Let's say someone (not me!!) is crazy enough to buy a Cessna 152 or 172
and instruct in it at a towered airport. What sort of ratio of Hobbs
to tach time would you expect?

The value (I've played with .85 up to 1.0) has a surprisingly large
effect on how much you have to charge for the plane.

--
Ben Jackson

http://www.ben.com/

Or look at your watch? Write down engine start time, then engine shutdown time.
That's how we did it when towing banners. Cub's don't have electrical systems
or hobbs meters, and when you're flying along at 1900 rpm's, the tach time isn't
exactly accurate either.

That's the way I do it today, with my watch, though by the puzzled
looks I get when I'm converting minutes to decimals, I think most
everybody else must use the tach.

My first flight instructor used watch time, and as with so many
things, the way you learned it when you were green is the way you keep
doing it.

all the best -- Dan Ford
email:

see the Warbird's Forum at www.warbirdforum.com
and the Piper Cub Forum at www.pipercubforum.com

Ben Jackson wrote:

If you then charge by Hobbs time there's a 'slop' factor in there
because Hobbs Tach. My question is: what is that factor? I was
hoping someone who had been involved in renting airplanes had an
estimate.

The FBO at the uncontrolled field at which I got my PPC used to use a factor of
1.2 times the tach in a Cessna 150. The aircraft had Hobbs meters, and we usually
paid according to the Hobbs, but sometimes one of the meters went TU.

George Patterson
Great discoveries are not announced with "Eureka!". What's usually said is
"Hummmmm... That's interesting...."