Speedy Tachometer

I posted this on the J3 forum, but not much help offered:

My (new to me) PA-11 has a rebuilt tachometer on its rebuilt C-90.

The RPM's are reading accurately, but the tach time is accruing at an alarming rate.

At 2300 RPM, 1/10 hour rotates in 3m38s.

Even a Hobbs would take 6m for that to occur.

Thoughts?

Daryl

There should be a placard on the tachometer which gives the rpm at which one hour records. It's probably set up to record an hour at a lower rpm. (unless it is broken)

Or you have a bonified time machine.

When I ordered my last tach, one of the options was to select normal cruise RPM so that hours would accrue properly.

I was going to post this on the J-3 forum for you - my buddy took his AC tach to a speedometer outfit in Lemon Grove, and for $140 they made it brand new. The hour meter is dead-nuts, after he figured out that it was in tenths and hundredths. Needle is steady as a rock. He had the hours match his airframe logbook.

So, look for a speedometer shop in your neighborhood, or I will get the name of this shop.

Now that explains an old mystery to me! Every summer for almost thirty years I flew the lodge
Circuit out around Bristol Bay/Illiamna area, when you showed up in the spring, they asigned you
An aircraft ( Beaver, Helio,206 floatplane) so since I didnt bother to log flight time everyday, I simply noted tach time when I picked up the plane I was to fly all summer and when you took it back to Anchorage in the fall and was done you wrote down tach time for the end of that summers work, I noticed a huge error in my time ,compared to all the other pilots I ever flew with, that where logging daily? When asked
How many hours they had acquired during the summers flying? The standard answer was 4-500 hrs, this amazed me as flying right beside them, trip for trip ,when I add up my log book entrys ,for all the summers I ever flew for lodges, it only avgs 280 hrs ??? So I now realize they all must have
Had a tach just like yours! Lol................ I am guessing about a 40 % error over 30 years compounded monthly? So next time someone tells you he has been flying for 25 years and he says I have 10,000 hrs , well I am guessing if he probably has more like 5500........when a fellow
Pilot tells me how many girls he has had ,, and how much flight
Time HE wrote in a log book, Both are likely exaggerated! (probably compounded at a similar rate)
Most fellas that really have 10K , never both to mention it
E

Turbo, I hope that you were not being paid by tach time. ;-) All of that time which you were taxing at low power to and from the other end of the lake was done at low rpm. So if you taxi for four hours you may accumulate one hour on the recording tach. The tach hourmeter is an rpm counter based on a designated cruising rpm giving the result in hours.

A 'Hobbs" meter is an electric clock normally connected to an oil pressure switch. Any time that the engine is running the "hobbs" is recording real time. FBOs use these for revenue producers since students do spend a lot of time at low rpm. The hourmeter on a tachometer is used for aircraft/engine log book purposes (with FAA approval).

Nope we got paid by the month so your hrs were not relivent too your pay, and your explaination on hobbs meters will be duly noted,
Of course for the really enthusiastic time builders, another whole different scheme was to skip the hobbs approach, and just look at your watch while you are eating your breakfast looking at an airplane, and then again when it is too dark to see it anymore, and log that as a days
Flying??(non FAA approved) No wonder there are so many 10K guys around. I met a guy one time from Palmer, Ak to buy an old ADF from him, he introduced himself as" so n so "and I have ten thousand hrs in Super Cubs............... I said ok ,and thought, that was an unusual way to introduce yourself?.
He then went on to inform me he had one of the lightest cubs known to man, and his highly modified engine 0320 had peged the dyno in areas not seen before! I later got to watch him in action down on the peninsula, and his story really fell seriously short of checking out......

In the old days this was referred to as P-51 time. (Parker 51) For you youngsters there was a pen made by Parker which was a model 51. ;-)

Ah yes, the old pen time, that seamed to be a favorite one for all the low time float pilots when trying to gain Alaskan employment, when the insurance requirements jumped to 500 hrs on floats, So the standard response was "one bic pen and two six packs of beer". :roll:

I wonder if an incorrect part was used in the tach or somewhere.
Vintage Harley speedometers are driven by the transmission, not by the wheel. Back in the day, I had the transmission on my panhead overhauled, and when I got it back together the speedo indicated about half the speed I was really going. Turns out that there were two different drive gears available, depending on which speedo you used. I took it back to the shop, they swapped drive gears, and all was well. So maybe something like that?

Daryl, leave it like it is, you will get cheaper insurance with more flying time. And before you know it you will have 10,000 hours.

Widely misunderstood! Pilot logbook time is not the same as aircraft time. Typically it is 10-15% more!

Pilot time is from first movement under power until engine shutdown. Aircraft time is liftoff to touchdown. The two are never the same, and a recording tach more closely approximates airframe time than it does pilot time.

Falsifying either is a totally different issue.

If the aircraft time is "lift off to touch down", where do you mount the squat switch on a Cub??

Same place as on the Airbus. Sends data back to the FBO.

OK. I'm doing an annual on one of my planes. I'll call the FBO tomorrow and get the correct time. Wait a minute, I'm the FBO for that plane! That squat switch must be broke. I never got any times from the switch. I better fix it..

T.J. said:

If the aircraft time is "lift off to touch down", where do you mount the squat switch on a Cub??

Click to expand...

Air Hobbs.....

STC can be purchased at SeaPlanes North at Lake Hood.

MANY many airplanes on the approved model list.

An air pressure switch "T"'s into the pitot line and completes the circuit to the Hobbs meter at around 30MPH. It is a huge timesaver for maintenance. The tachometer counter may still be used for "billing".

(907) 248-7070 SeaPlanes North Parts Counter......they are also a Cessna Parts Distributor and Viking DeHavilland Parts dealer and have tons of hardware and supplies if you happen to need that kind of thing at Lake Hood. Open 8 to 5 M-F.

I bet the tach saves more time in Cub-like airplanes. For pattern work, tach time is about 2/3 of hobbs time. The squat switch will save if the mission is fast X-C.

Wow more guages to put in. I must have been doing it wrong all this time: Using a wrist watch and a bic pen is just not cub chic anymore...
But I bet I could squeeze a new Air Hobbs into my limted panel space- right between the Keurig coffee maker and the DVD player

If you talk to a pilot needing 1500 hours before he can start flying for pay than logbook time starts when he can see the plane at he drives to runway (some figure leaving home driving to plane a good time to start counting because you are planing flight, emergency actions, ect). If you talk to a APT in left seat of a heavy the talk of 2-3 grand of round motor time, 3 grand twin time, ect they only care how much they get paid for standby or landings (what you get paid extra for landing the plane). What we really need is a instrument that will be placed in the rectum of very pilot at there first flight. This will record how much of the seat cushion is pulled into the rectum. This will show how much experience the pilot really has. The logbook has no ideal how many hours the plane really in in the air!!! Just saying!!
DENNY

wronghand said:

Wow more guages to put in. I must have been doing it wrong all this time: Using a wrist watch and a bic pen is just not cub chic anymore...
But I bet I could squeeze a new Air Hobbs into my limted panel space- right between the Keurig coffee maker and the DVD player

Click to expand...

the air hobbs uses your existing hobbs meter..