Hi: I was just told by a A/P that in order to install a new tach in our planes that it would have to be FAA certified for Cirrus or STS and that it could not be used to log engine time to TBO. Does anyone know if this is fact? The savings in dollars is just to great not to have one installed, if it can be used as “official engine time”. I still have a very low time engine and every minute counts.
Norm N6839R
In reply to:
Hi: I was just told by a A/P that in order to install a new tach in our planes that it would have to be FAA certified for Cirrus or STS and that it could not be used to log engine time to TBO. Does anyone know if this is fact? The savings in dollars is just to great not to have one installed, if it can be used as “official engine time”. I still have a very low time engine and every minute counts.
Norm,
A couple of points here, and also a couple of opinions:
Under part 91, if not operated for hire, there’s no requirement to overhaul the engine at TBO. So, I’m not sure what you mean when you ask “can be used to log engine time to TBO”, since reaching TBO doesn’t really have any meaning, except perhaps in the marketplace when you’re trying to sell a plane with XXX hours, and TBO is YYY.
It seems that each regional FSDO has slightly different rules about these things, in terms of paperwork required for installation. Bill Dobson has mentioned this w.r.t. getting GPSS installed (for example, I personally did not seem to require a 337 for installation, just a log book entry - others are the same. But the FSDO near Bill wants a 337 or STC).
Personally, I would think that it wouldn’t be TOO hard for a shop to write up a 337 (major alteration form) for installing a tach, as long as the tach is certified [STC’ed] for use in SOME certified plane, not necessarily a Cirrus. It will be some extra paperwork – and thus some extra money on your part – but doesn’t seem to me to be too bad. But then again, if your FSDO is a real stickler for things, maybe this route isn’t open to you.
Similarly, you could delay other maintenance; if you wanted to change your vacuum pump every 500 hours, just change it at 600 hobbs hours (= 500 x 1.20) instead.
Others have proposed that reselling the plane will be easier because you can say “it only has XXX hours” (rather than XXX x 1.2 hours as recorded on the Hobbs).
But if I were buying a used Cirrus, I would compare apples to apples. Since EVERY Cirrus has a hobbs meter, I would ask you what the hobbs time was, so that I could compare it to other Cirruses I was shopping for that did not have a tach. So I’m not even sure it buys you anything there, either.
In summary, given that non-hire part 91 does not mandate overhauls at a certain time, or oil changes at a certain time***, etc. it seems to me that there’s not a whole lot of rationale to installing a tach meter.
But that’s just me - I understand that others feel differently.
Steve
*** the only exception I can think of is that some ADs require compliance within a certain # of flight hours. But that doesn’t seem to be THAT big a deal. And of course, if you’re renting our your Cirrus, or otherwise using it for hire, then most of my argument is moot.
Norm,
A FAR 91 operator can legally exceed TBO on most piston engines, since the TBO is merely a manufacturer’s recommendation. Nothing in FAR 91 requires compliance with these recommendations. On the other hand, the TBO is limiting for a FAR 135 operator, as FAR 135.421 requires compliance with manufacturer’s recommendations related to engines, propellers, rotors, and items of emergency equipment.
I know many IAs won’t sign an annual if the engine has exceeded the TBO. I don’t blame them. Why should they take the risk?
The key for just about all things that are based on hours is called “Time in Service.” As defined in FAR 1.1:
“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 the Tach nor the Hobbs measures this.
Steve,
I like your line of thinking on this one. Better to spend the money for this project on something else IMHO.
Mason
Steve thanks for the great answer and clarification. The issue still is the a high time engine with a TBO of 1700 when you decide you want to sell. The time difference would be about 300 to 500 hours difference in reference to TBO life of the engine.
Norm N6839R
What is the reason for Cirrus to pick this type of recording. I always had a tach type. There must be a techiacl reason. Or money reason for them. From Don
Steve’s point was, there is no difference between an airplane with 1500 on the Hobbs vs. one with 1500 on the Hobbs and 1250 on the Tach.
In reply to:
Steve’s point was, there is no difference between an airplane with 1500 on the Hobbs vs. one with 1500 on the Hobbs and 1250 on the Tach.
This is true, but there IS a difference between an ad for a used airplane that says “1250TT” vs. one that says “1500TT” and with the tach you would have a factual basis for claiming the lower figure. And I wouldn’t be surprised if many buyers will NOT be as aware of the nuances as we are reading this thread.
(But I tend to agree with you that this is not something worth the cost. I do wish Cirrus had chosen a tach with a traditional “odometer”)
Tim
Who knows why. I think a traditional odometer would be the way to go and not even have a hobbs meter. But that is just me.
Mason
I asked Cirrus this question directly when in Duluth in Nov and was told there was not a recording tach available in the size they use. They did not consider the EI a choice for production. I dont know why. Probably cost.