A previous thread was discussing the merits of adding a recording tach instead of using the Hobbs. I just finished reading the SR20 POH again and I can’t find any mention of any kind of a permanent time recording device. Does the SR20 have a Hobbs meter. If not, how do you deal with warranty, maintenance, or even oil changes?
Art: There is a reference in the POH, but it is easy to miss. Check page 7-16 where the following language is found:
“CENTER CONSOLE”
A center console contains the avionics, flap control and position lights, power lever and mixture controls, fuel system indicator and controls, and audio controls. System circuit breakers, the alternate static source valve, alternate induction air control, and ELT panel switch are located on the left side of the console for easy access by the pilot. A friction knob for adjusting throttle and mixture control feel and position stability is located on the right side of the console. An accessory outlet, map compartment, audio jacks, hour meter, emergency egresss hammer, and headset jacks are installed inside the console armrest."
The concern regarding the hour meter provided is that it accumulates time whenever the engine is running, i.e. any time the alternator is producing output. It thus records idleing time, taxi time, etc. and not just the hours over a certain rpm setting. There are electronic tachs that will record only the time above a certain rpm and thus give a more realistic “tach time”. I plan seriously consider having the electronic tach in the Cirrus replaced by one of these. The FAA requires that any limitations (max rpm, min rpm) be annunciated, and there is one unit that will do this.
See Electronics International Inc. at www.Buy-EI.com for details on their RPM instrument. It will permanently record tach time as well as flight time. Tach time is going to be less than the time recorded in the hour meter inside the console. Whether the difference is worth the cost and trouble of putting in an
IE tach is the question.
One way to address this is to install an air switch so the Hobbs only ticks when the airspeed exceeds, say, 30 knots. The air switch is installed on a pitot/static line. This apparently has been done on at least one Cirrus SR20, N5841, which is (was?) a rental aircraft owned by the “Windy City Flyers” at Palwaukee airport.
The Garmin 327 transponder turns on at 30 knots, so there may be an output available for that state. I’ll try and find out if this is a possibility.
Presumably, either of these modifications would require a 337.
Art: The other advantage of the EI tach is it’s more graphic display of engine rpm and the red led’s for any out of limits rpm. Since it is over on the right side of the panel, this should make setting a specific engine rpm more precise. The tach timer is internal to the unit and is triggered by the rpm reading, so no air switch or connection to the GPS is required. The flight timer function is duplicated on the Garmin 327 so there is not a great advantage there. I asked EI if they intended to contact Cirrus to make their unit an option, and they had no interest in doing that. After I get my SR22, I will need to decide if there is an advantage in changing the existing tach.
Under no circumstances should the hobbs meter be removed.
This is the second or third time that this thread has emerged. My questions is why the concern about how time is recorded?
As I see it, here are the issues.
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Annuals are done annually (duh), aircraft time is no factor -only calendar time.
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If you have to do 100 hour inspections, then this would essentially defer maintenance by around 10%, but if the aircraft is being paid for by the time in use, this is offset by lower earnings.
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For insurance reasons, the more time is better.
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For resale purposes, the time is slightly lower so the value may be slightly higher.
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For oil changes, you set the time intervals and it is what it is, regardless of how you record it. If you are trying to stretch the interval, you only may be fooling yourself.
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But here is the real issue. Things will break, wear our and need replacement at their own schedule, regardless of how you record time. If the engine makes it to TBO, then it does, if it doesn’t, then it doesn’t. Same with the cylinders. When they need work/replacement they are not looking at the clock.
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If you ‘time-out’ parts (alternators, vacuum pumps, etc.) then it is your schedule anyway and you can adjust the hours any way you please.
What am I missing?
Marty,
You’re not missing anything. Your comments are right on the money.
Jerry
- Annuals are done annually (duh), aircraft time is no factor -only calendar time.
Agree.
- If you have to do 100 hour inspections, then this would essentially defer maintenance by around 10%, but if the aircraft is being paid for by the time in use, this is offset by lower earnings.
Disagree. FBO’s, others I’ve asked and my own experience, say that the number is about 25% difference. This directly translates into more money put into inspections than tack time. It also shorten’s the calendar time between inspections for an airplane that flies a set amount.
- For insurance reasons, the more time is better.
Theoretically yes however this hasn’t been my experience in owning a previous airplane over 1000 hours.
- For resale purposes, the time is slightly lower so the value may be slightly higher.
This is very important. If you are selling an airplane with 2000 hobbs hours, the buyers will probably all say the engine is runout and want to adjust the price accordingly. However with a tach it is only 1500 hours.
- For oil changes, you set the time intervals and it is what it is, regardless of how you record it. If you are trying to stretch the interval, you only may be fooling yourself.
Agree, but if I do my oil changes every 75 hours by the hobbs then a buyer could be turned off by that fact. Sure he may be educated in the difference, but perhaps he also thinks it should be 10% difference. So now we have a problem based on my interpretation versus his. And there aren’t as many airplane buyers out there as there used to be.
- But here is the real issue. Things will break, wear our and need replacement at their own schedule, regardless of how you record time. If the engine makes it to TBO, then it does, if it doesn’t, then it doesn’t. Same with the cylinders. When they need work/replacement they are not looking at the clock.
Agree, but in the case of a TBO in a 135 operation, you have to overhaul at TBO. If it’s 25% difference, pretty expensive.
- If you ‘time-out’ parts (alternators, vacuum pumps, etc.) then it is your schedule anyway and you can adjust the hours any way you please.
Agree.
The real issue is it is a cheap way to potentially help your resale. If you’re a commercial operator, it will save you money.
P.S. Jim at Lancaster was looking into a tach time gauge that will replace the existing tach. He was going to find out from Cirrus if he can replace the existing one with it and what the problems with certification will be.
Derek
Except that when people buy used airplanes, the first question they ask is, “What is the total time engine and airframe?”.
Paul,
Tthe second question is: “is that Tach or Hobbs time?”
Jerry
And for the vast majority of aircraft out there, the answer is “Tach time”. So in this regard the Cirrus is starting from behind the 8 ball.
- If you have to do 100 hour inspections, then this would essentially defer maintenance by around 10%, but if the aircraft is being paid for by the time in use, this is offset by lower earnings.
Disagree. FBO’s, others I’ve asked and my own experience, say that the number is about 25% difference. This directly translates into more money put into inspections than tack time. It also shorten’s the calendar time between inspections for an airplane that flies a set amount.
I think you will find the difference is greatest in a low power training environment, such as a flight school where a lot of time is doing pattern work and not cross country. If you fly cross-country most of your time, and especially at higher power settings, I think you will find the difference much less.
- For resale purposes, the time is slightly lower so the value may be slightly higher.
This is very important. If you are selling an airplane with 2000 hobbs hours, the buyers will probably all say the engine is runout and want to adjust the price accordingly. However with a tach it is only 1500 hours.
You can use the figures any way you want, but that looks like the hobbs is reading 33% more than the tack. Either way, a buyer will also look at compression, airframe condition and perhaps a borescope. If you feel it is important, go ahead, but I think the FBO/Mechanic will end up making (saving) more money on the deal than you!
One final question: Would you remove the Hobbs? If not, both times are usually recorded and that will always beg the question, Why did you remove it?" Also, if the buyer has been shopping Cirruses, he will note that you have one of the very few without a Hobbs.
Good luck.
I agree that an airswitch is likely the simplest solution, all the better if it can come off the GTX 327. Let us know what you find out!
I sure don’t want to beat a dead horse, but, has anyone come up with a reasonable solution that is already approved that allows us to track both hobbs and tach time? I think they are both worth tracking…
Greg
Yes, add an airswitch to the pitot line, connected to a second hourmeter, located below the existing one.
Greg,
See my post in Members Forum on 4/16/02.
The Garmin(s) do indeed record CUMULATIVE and RESETTABLE flight times (starting when the plane exceeds 30 knots ground speed and ending when ground speed is under 30 knots). “Distance divided by average speed equals hours flown”.
I keep a log, entered at maintainance events, of HOBBS TIME and FLIGHT TIME. I log and reset one Garmin 430 with each oil change.
Randy